Bats, Pterosaurs and Echolocation
Rickard Toomey
I have combined discussion from a couple of separate, but
related threads.
First, in an email to me in response to my discussion of
characteristics that might indicate echolocation in
pterosaurs, bke...@mdc.net (Bob Keeter) asked a couple
of very good questions concerning whether I would expect
to see bat like echolocation adaptations in pterosaurs
if they echolocated. (Bob, I hope you don't mind me
answering publicly, your question was very good.)
The character I would look for as evidence of echolocation
in pterosaurs would be modifications that lead to
isolation of the bones enclosing the cochlea. This
characteristic is found not only in bats, but also
in echlocating cetaceans. It apparently aids in
keeping confounding signals from being conducted in
to the ear through bones.
Second, bke...@mdc.net (Bob Keeter) asked (in
a thread entitled "Re: Were pterosaurs really fish-eaters?").
> Please tell me if I am wrong, but my understanding was that the
> earliest fossil even remotely resembling a bat was already easily
> recognizable and fully adapted as a insect-eating bat? Extended
> finger-bones, "mal-formed" rear legs/pelvis, spikey little teeth, etc
> (including adaptations to the skull optimized for echolocation). Also,
> do I not remember somewhere that the fruit bats all basically lack
> echolocation, depending entirely on sight/smell for feeding? Why would
> a non-flying predecessor evolve echolocation to eat fruits, develop
> wings to fly around and THEN "de-volve" the echolocation just to
> continue eating fruit? Guess I am just missing the logic here!
Bob is correct in several aspects of these comments. Yes,
"fruit bats" (i.e. Megachiroptera) generally do not have
the ability to echolocate. There are two Megachiroptera
genera that are thought to echolocate (Rousettus and
Eonycteris). However, neither echolocates in the same
manner as is seen in the Microchiroptera.
Also, he is correct in saying that the earliest known
bats (several genera from the Early-Middle Eocene Messel
and Green River deposits) closely resemble modern
Microchiroptera. Bat paleontologists agree that they
could echolocate (although not in as sophisticated
manner as most modern Microchiroptera).
So, Bob's question about the potential loss of echolocation
is well taken. The answer depends on the relationship
between the phylogeny of bats and the acquisition of
both echolocation and flight.
Harry Erwin <her...@gmu.edu> commented on the issue
within a thread entitled "Re: When is a duck not a duck?"
> Bats
> probably evolved from small nocturnal arboreal fruit/insect eaters that
> already echolocated, while pterosaur ancestors were probably diurnal and
> may have been meat/fish-eating. Pterosaurs were probably descended from
> vertical clingers and leapers, while bat ancestors were probably more
> like the mammalian gliders that hang from the branches.
If Harry is correct, then we are faced with trying to answer
Bob's question. However, the hypothesis provided by Harry
is not the only one that has been proposed.
In truth there are four general classes of hypothesis that
potentially address the relationship of bat evolution
to flight and echolocation.
The first hypothesis would be that bats are not a monophyletic
group, that is, Microchiroptera and Megachiroptera evolved
separately from different non-flying ancestors. This
hypothesis was popularized by Pettigrew. If correct, it would
answer Bob's question because there would be no reason to
assume that Megachiroptera evolved from an echolocating
ancestor. So, they would not have lost echolocation.
However, I would agree with Simmons and Geisler (1998) in
noting that the monophyly of bats is one of the most
strongly supported of all higher-level mammals relationships.
It is supported by morphological, biochemical, and genetic
data. So, I would not favor this as an answer.
If we accept that bats are monophyletic, there are three
viable hypotheses. These are generally "echolocation
first," "flight first," and "tandem evolution." See
Simmons and Geisler (1998) for a good discussion of
these hypotheses and their relationship to reconstructed
bat phylogeny.
If echolocation evolved before flight, we cannot reasonably
answer Bob's question of why Megachiroptera lost the ability
to echolocate and then had two species re-evolve the ability
in different ways.
The tandem-evolution idea focuses on the fact that flight,
breathing and echolocation are physiologically coupled in
Microchiroptera, and they could arise together with no additional
metabolic cost. Speakman (1993) developed this idea. It
also fails to account for the (presumed) loss of echolocation
in Megachiroptera.
The only hypothesis that currents accounts for the phylogeny of
Chiroptera and does not require the (unexplained) loss of
echolocation in Megachiroptera is that bats evolved flight
first and then one group (ancestors of Microchiroptera)
evolved echolocation. Simmons and Geisler (1998) note
the following (p.4):
Our phylogeny provides a basis for evaluating previous
hypotheses on the evolution of flight, echolocation,
and foraging strategies. We propose that flight evolved
before echolocation, and that the first bats used vision
for orientation in their arboreal/aerial environment.
The evolution of flight was followed by the origin of
low-duty-cycle laryngeal echolocation in early members
of the microchiropteran lineage. This system was most
likely simple at first, permitting orientation and
obstacle detection but not detection or tracking
of airborne prey. Owing to the mechanical coupling
of ventilation and flight, the energy costs of
echolocation to flying bats were relatively low. In
contrast, the benefits of aerial insectivory were
substantial, and a more sophisticated low-duty-cycle
echolocation system capable of detecting, tracking and
assessing airborn prey subsequently evolved rapidly.
The need for an increasingly derived auditory system,
together with limits on body size imposed by the
mechanics of flight, echolocation, and prey capture,
may have resulted in reduction and simplification
of the visual system as echolocation became
increasingly important.
References cited
Simmons N.B. and Geisler, J.H., 1998, Phylogenetic relationships of
Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx
to extant bat lineages, with comments on the evolution of echolocation
and foraging strategies in microchiroptera. Bulletin of the
American Museum of Natural History, Number 235, New York. 182pp.
Speakman, J.R., 1993, The evolution of echolocation for predation,
Symposium of the Zoological Society of London 65: 39-63.
Hope that helps clarify some of the questions.
Rick Toomey
Illinois State Museum
too...@museum.state.il.us
Bob Keeter
the "To," "Cc," and "Newsgroups" headers for details. ]]
In article <37F64780...@earthlink.net>, Rickard Toomey
<myo...@earthlink.net> wrote:
First off, thanks much for the detailed reply. I would like
to pursue one part a bit more though.
>
> First, in an email to me in response to my discussion of
> characteristics that might indicate echolocation in
> pterosaurs, bke...@mdc.net (Bob Keeter) asked a couple
> of very good questions concerning whether I would expect
> to see bat like echolocation adaptations in pterosaurs
> if they echolocated. (Bob, I hope you don't mind me
> answering publicly, your question was very good.)
> The character I would look for as evidence of echolocation
> in pterosaurs would be modifications that lead to
> isolation of the bones enclosing the cochlea. This
> characteristic is found not only in bats, but also
> in echlocating cetaceans. It apparently aids in
> keeping confounding signals from being conducted in
> to the ear through bones.
>
If I am to understand your explaination, the isolation of the
cochlean bones produces a mechanical "band pass" filter similar
to the piezoelectric mechanically controlled filters used in
some radios (and early radars). I had not thought about that
possibility at all. Makes sense that some sort of "band pass"
would be needed, BUT is that the only way to get there. Could
not a "tuned cavity" for an ear canal do about the same with
only soft tissue? Just as a wave guide would on a radar or
VHF transmitter?
Do the echo-locating fruit bats ALSO have this inner ear adaptation
even though they generate the sound with "tongue clicks" instead of
vocalization?
Yeah, Im reaching a bit and Mr. Occam would not be happy, BUT I still
have trouble with the little beady eyes, totally mis-positioned for
aerial navigation, on some of the big pterosaurs. I really think that
they needed some help (even in broad daylight!) to navigate in flight,
even if only to avoid flying into things.
As for the rest, you definitely confirmed my suspicion that there
was not much for a "hard answer". Guess we will have to think
about that one a bit more!
Thanks again
bk
Rick Toomey
the "To," "Cc," and "Newsgroups" headers for details. ]]
Hello,
I am not sure how much isolation of the cochlea occurs in
either of the Megachiropterans that echolocate. By the way,
you are correct that Rousettus uses tongue-clicking, but
Eonycteris apparently slaps its wing tips together to
create the outgoing signal. By the way, neither may have a
sophistocated enough echolocation to model what you have
proposed for pterosaurs.
Also, I failed to mention the animals that might provide
the best information on what you might look for in pterosaurs
to suggest echolocation. Several types of birds are known
to echolocate (to one degree or another). These include
oilbirds (Steatornis) and cave swiftlets (Collocialia and
Aerodramus). I have no idea what auditory modification
they exhibit. That might be a good avenue to pursue
if one was looking for what modifications might occur
whan an archosaur uses echolocation. This is not a
topic with which I am very familiar. I can provide some
references to papers on oilbird and cave swiftlet echolocation
if people would like (but I have not seen any of them).
Sorry, I can't provide much additional info on the question
of other means to isolate the cochlea from bone transmitted
sound. Perhaps Harry Erwin will have some suggestions or
insights into this question.
Hope this helps some.
Rick Toomey
Illinois State Museum
too...@museum.state.il.us
Bob Keeter wrote:
>
> [[ This message was both posted and mailed: see
> the "To," "Cc," and "Newsgroups" headers for details. ]]
>
> In article <37F64780...@earthlink.net>, Rickard Toomey
> <myo...@earthlink.net> wrote:
>
> First off, thanks much for the detailed reply. I would like
> to pursue one part a bit more though.
>
> >
> > First, in an email to me in response to my discussion of
> > characteristics that might indicate echolocation in
> > pterosaurs, bke...@mdc.net (Bob Keeter) asked a couple
> > of very good questions concerning whether I would expect
> > to see bat like echolocation adaptations in pterosaurs
> > if they echolocated. (Bob, I hope you don't mind me
> > answering publicly, your question was very good.)
> > The character I would look for as evidence of echolocation
> > in pterosaurs would be modifications that lead to
> > isolation of the bones enclosing the cochlea. This
> > characteristic is found not only in bats, but also
> > in echlocating cetaceans. It apparently aids in
> > keeping confounding signals from being conducted in
> > to the ear through bones.
> >
>
Rick Toomey
Cal King provided an interesting analysis of why one might
not be surprised to find that Megachiroptera would lose the
ability to echolocate.
In particular Cal King wrote:
> >
> >If echolocation evolved before flight, we cannot reasonably
> >answer Bob's question of why Megachiroptera lost the ability
> >to echolocate and then had two species re-evolve the ability
> >in different ways.
>
> The answer is pretty easy. Evolutionary reversal is rampant. Unneeded
> features degenerate quickly. Chorophyll is one of the most conservative
> molecules around for very good reasons. Yet in those plants in which
> photosynthesis is no longer needed, its chemical structure quickly
> deteriorate, as botany student Brian Speer noted in some of his past posts to
> this group. Shows that a lack of selection can lead to rapid "evolutionary"
> change indeed. If macrochiropterans are merely "degenerate" microchiropterans
> that changed their diet from insects to fruits, then it is easy to see why
> such an unneeded character can quickly be lost through reversal. Fruits
> just don't move. Why some macrochiopteran species re-evolve echolocation will
> depend on an analysis of the adaptiveness of echolocation in these species.
> The fact that the echolocation system these species use is different is strong
> support for Dollo's principle: evolution does not occur in exactly the same
> way twice. It is also strong support for reversal in the character of
> microchiropteran echolocation. Hence there really is no obstacle to the
> acceptance of the echolocation first theory. Echolocation can indeed be
> useful for a nocturnal arboreal bat precursor if it helps the bat locate
> insects lying on branches. Catching insects on the wing is a highly
> specialized feeding method and it is not a common mode of feeding even among
> birds. Perhaps nocturnal bat precursors glided to avoid enemies much as
> diurnal arboreal animals do, and flight evolved from the tree down in bats.
> The already present ability to echolocate would help a bat precursor glide
> safely even in total darkness. In fact, it really makes little sense to fly
> in the dark hoping that one will catch insects without the ability to
> echolocate especially if the possibility of collisions are high. Most birds
> are diurnal for this simple reason.
>
The problem with this logic is that if echolocation is so useless
for bats that are eating food that does not move, why have NONE
of the approximately 150 species of Microchiroptera that feed on
fruit, nector, and/or pollen lost their ability to echolocate.
These are not isolated species within insectivorous groups,
they include almost all of the members of second largest family
of Microchiroptera (Phyllostomatidae).
Clearly, echolocation is advantageous for plant eating bats
as well as insect eating ones. The fact that two genera
of Megachiroptera also evolved the ability also confirms
this.
With respect to another point. Cal King's suggestion
that bats evolved flight from the tree down is certainly the
commonly accepted model for aquisition of flight.
Something to think about.
Ralph W. Miller III
> BTW, I see no
> problem with the positioning of the eyes in pterosaurs. Their placement is
> similar to those of birds. It may be noteworthy that one specimen of
> Archaeopteryx was misidentified at first as a pterosaur. The amount of
> convergent similarities between birds and pterosaurs is remarkable to say the
> least.
The Teyler specimen of _Archaeopteryx_, originally dubbed _Pterodactylus
crassipes_ (the type specimen, yet!), is the most fragmentary scrap of skeletal
material yet identified as _Archaeopteryx_. Just some wing bones and feather
impressions. Its original identification as _Pterodactylus_ owes less to
convergent features and more to its excavation date of 1855, before any other
_Archaeopteryx_ material had been recovered or identified. Luckily, the ICZN went
along with Ostrom's petition to rename the specimen _Archaeopteryx lithographica_,
because otherwise we would be referring to what we now call _Archaeopteryx_ as
_Pterodactylus_, because that is the oldest known valid name for an
_Archaeopteryx_ specimen! See Pat Shipman's _Taking Wing_, pp. 38-44.
Much more compelling are the anatomical similarities between _Archaeopteryx
lithographica_ and _Compsognathus longipes_, as the wonderfully complete Eichstatt
specimen of the former, and the nearly complete Solnhofen _Archaeopteryx_
specimen, were both mistaken for _Compsognathus_, each going for years by the
wrong name! Convergence... or homology? You be the judge.
-- Ralph W. Miller III gbab...@best.com
"I resemble that remark!"
Dave Timpe
Rickard Toomey <myo...@earthlink.net> wrote in message
news:37F64780...@earthlink.net...
| The character I would look for as evidence of echolocation
| in pterosaurs would be modifications that lead to
| isolation of the bones enclosing the cochlea. This
| characteristic is found not only in bats, but also
| in echlocating cetaceans. It apparently aids in
| keeping confounding signals from being conducted in
| to the ear through bones.
This causes me to ask, are there such adaptations in echolocating birds?
(Swiflets, for one echolocate, other cave nesters and night flyers also do,
but I can't recall the species). If they also have isolation of the
cochlear bones it would make it as close to a clear-cut indicator as you're
likely to get.
--
Dave Timpe
davetimpe at cybrzn dot com
bull.net Cal King
>If we accept that bats are monophyletic, there are three
>viable hypotheses. These are generally "echolocation
>first," "flight first," and "tandem evolution." See
>Simmons and Geisler (1998) for a good discussion of
>these hypotheses and their relationship to reconstructed
>bat phylogeny.
>
>If echolocation evolved before flight, we cannot reasonably
>answer Bob's question of why Megachiroptera lost the ability
>to echolocate and then had two species re-evolve the ability
>in different ways.
The answer is pretty easy. Evolutionary reversal is rampant. Unneeded
>The tandem-evolution idea focuses on the fact that flight,
>breathing and echolocation are physiologically coupled in
>Microchiroptera, and they could arise together with no additional
>metabolic cost.
Yes, but such a scenario is implausible because it represents a quantum leap
and smacks of intelligent design. Evolution really does not occur that way.
I am sure when more fossils become available, it would likely show that
echolocation evolved first.
Speakman (1993) developed this idea. It
>also fails to account for the (presumed) loss of echolocation
>in Megachiroptera.
>
>The only hypothesis that currents accounts for the phylogeny of
>Chiroptera and does not require the (unexplained) loss of
>echolocation in Megachiroptera is that bats evolved flight
>first and then one group (ancestors of Microchiroptera)
>evolved echolocation. Simmons and Geisler (1998) note
>the following (p.4):
>
> Our phylogeny provides a basis for evaluating previous
> hypotheses on the evolution of flight, echolocation,
> and foraging strategies. We propose that flight evolved
> before echolocation, and that the first bats used vision
> for orientation in their arboreal/aerial environment.
That certainly is plausible as well. It appears that bats are not as well
adapted for nocturnal living as some primates are (e.g. the small eyes).
> The evolution of flight was followed by the origin of
> low-duty-cycle laryngeal echolocation in early members
> of the microchiropteran lineage. This system was most
> likely simple at first, permitting orientation and
> obstacle detection but not detection or tracking
> of airborne prey. Owing to the mechanical coupling
> of ventilation and flight, the energy costs of
> echolocation to flying bats were relatively low. In
> contrast, the benefits of aerial insectivory were
> substantial, and a more sophisticated low-duty-cycle
> echolocation system capable of detecting, tracking and
> assessing airborn prey subsequently evolved rapidly.
But there is a difficulty with this hypothesis. If bats are indeed diurnal,
they don't need to echolocate to catch insects during the daytime. Swallows,
for example, do it well enough using their eyes alone. It appears that bats
evolved echolocation to feed in the dark. It would be fool hardy to try
to feed on flying insects in the dard before evolving echolocation. So I
still think that echolocation must have become quite accurate and
sophisticated before bats can even attempt to make a living catching insects
on the wing and in the dark.
> The need for an increasingly derived auditory system,
> together with limits on body size imposed by the
> mechanics of flight, echolocation, and prey capture,
> may have resulted in reduction and simplification
> of the visual system as echolocation became
> increasingly important.
I do not dispute the claim that sight became less important as echolocation
became more sophisticated. But if this is correct, there is the possibility
that bats may have had large eyes that were part of their adaptation for a
nocturnal, arboreal existence and that their eyes became reduced (another
reversal) as bats grown to rely upon echolocation instead of their eyes.
>References cited
>
>Simmons N.B. and Geisler, J.H., 1998, Phylogenetic relationships of
> Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx
> to extant bat lineages, with comments on the evolution of echolocation
> and foraging strategies in microchiroptera. Bulletin of the
> American Museum of Natural History, Number 235, New York. 182pp.
>
>Speakman, J.R., 1993, The evolution of echolocation for predation,
> Symposium of the Zoological Society of London 65: 39-63.
>
>
>Hope that helps clarify some of the questions.
>
>Rick Toomey
>Illinois State Museum
>too...@museum.state.il.us
>
Thanks for the references and the stimulating discussion of current theories
of the origin of flight and echolocation in bats. Personally I think the
echolocation first theory is probably the most plausible of the available
theories for the reasons cited above.
bull.net Cal King
Keeter) wrote...
>Yeah, Im reaching a bit and Mr. Occam would not be happy, BUT I still
>have trouble with the little beady eyes, totally mis-positioned for
>aerial navigation, on some of the big pterosaurs. I really think that
>they needed some help (even in broad daylight!) to navigate in flight,
>even if only to avoid flying into things.
I don't know where Mr. Keeter gets the idea that pterosaurs have "beady little
eyes." It is just not true. The illustrations that I do see all show large
orbital openings. Perhaps he just loves to say that particular phrase so much
that he just doesn't care if pterosaurs really have big or small eyes. I am
only raising this point for the sake of clarity and accuracy. BTW, I see no
bull.net Cal King
<gbab...@best.com> wrote:
>Cal King wrote:
>
>
>> BTW, I see no
>> problem with the positioning of the eyes in pterosaurs. Their placement is
>> similar to those of birds. It may be noteworthy that one specimen of
>> Archaeopteryx was misidentified at first as a pterosaur. The amount of
>> convergent similarities between birds and pterosaurs is remarkable to say the
>> least.
>
>crassipes_ (the type specimen, yet!), is the most fragmentary scrap of skeletal
>material yet identified as _Archaeopteryx_. Just some wing bones and feather
>impressions.
As Feduccia (1996:32) tells it, this specimen consists of "parts of one hand,
miscellaneous leg and arm bones, feet, and some feather impressions." If one
can identify it as a pterosaur, then it does show that there is a great deal
of convergent similarities between birds and pterosaurs. After all,
pterosaurs were at one time considered as possible ancestor of birds,
although this hypothesis never gained wide acceptacnce due to the
dissimilarities between their wings.
> Its original identification as _Pterodactylus_ owes less to
>convergent features and more to its excavation date of 1855, before any other
>_Archaeopteryx_ material had been recovered or identified. Luckily, the ICZN
> went
>along with Ostrom's petition to rename the specimen _Archaeopteryx
> lithographica_,
>because otherwise we would be referring to what we now call _Archaeopteryx_ as
>_Pterodactylus_, because that is the oldest known valid name for an
>_Archaeopteryx_ specimen! See Pat Shipman's _Taking Wing_, pp. 38-44.
It shows that the ICZN is not a dictatorial organization and that the rules of
taxonomy are only guidelines, not inviolable laws. It also shows that the
ICZN values taxonomic stability above nomenclatural priority, which is perhaps
the most universally respected rule in taxonomy. What does it tell us (and
the cladists) when the supreme ruling body of nomenclature says that
nomenclatural stability is so extremely important to biologists world wide
that some of its rules may be waived if the alternative is taxonomic
instability?
>Much more compelling are the anatomical similarities between _Archaeopteryx
>lithographica_ and _Compsognathus longipes_, as the wonderfully complete
> Eichstatt
>specimen of the former, and the nearly complete Solnhofen _Archaeopteryx_
>specimen, were both mistaken for _Compsognathus_, each going for years by the
>wrong name! Convergence... or homology? You be the judge.
>
>-- Ralph W. Miller III gbab...@best.com
T. Huxley, aka Darwin's bulldog, was the first to note the similarities
between Compsognathus and Archaeopteryx, but he also noted a great deal of
similarities between Archaeopteryx and the Ornithischian dinosaurs. (Feduccia
1996:52) May I also point out that there is also a great deal of similarity
between the Ornithomimid saurischians and birds, including the independent
evolution of tooth loss in the two lineages. There is therefore a great deal
of convergent evolution in the many lineages of Archosaurian reptiles, and one
should not use circular reasoning to attempt to sort the convergent
similarities from homologues. IOW, when one assumes these similarities are
synapomorphies, then one performs a cladistic analysis using these characters,
and then use the results of that analysis to "prove" that these putative
synapomorphies are in fact homologous, one is engaging in circular reasoning.
A better way is to analyze each character's anatomical detail to look for
clues of independent origin. When these characters are thus analyzed in
detail by some of the greats of paleontology past and present (such as Romer,
Simpson, Dollo, Osborn, to name but a few), the overwhelming consensus is that
they are convergences. In contrast, the "benchmark" cladistic study (Gauthier
1986) which unites the birds and theropods, is in Gauthier's words, "armchair
cladistics." Gauthier (1986), according to Feduccia (1996) never analyzed the
characters he used. Many of the characters used by Gauthier (1986) are not
examined in person, but are based on PUBLISHED sources, many of them not well
figured, according to Larry Martin.
Now, YOU be the judge as to why anyone should put more weight on the detailed
anatomical analyses of Romer, Simpson, Dollo et al. or on the total LACK of
any anatomical analysis by Gauthier (1986) when it comes time to decide
whether the similarities between Compsognathus and Archaeopteryx are
convergent or homologous!
bull.net Cal King
>The problem with this logic is that if echolocation is so useless
>for bats that are eating food that does not move, why have NONE
>of the approximately 150 species of Microchiroptera that feed on
>fruit, nector, and/or pollen lost their ability to echolocate.
I surmise it is because they can still benefit from echolocation, since their
eyes cannot replace their echolocation. That would suggest to me that the
macrochiropterans evolved quite early in the history of the bat lineage, but
after echolocation had evolved. An analog could be made between bats and
birds. Flightless birds come in many different varieties. The ratites have
been flightless for so long that they have lost the hooklets on their
barbules and have greatly shortened front limbs. More recently evolved
flightless birds retain powerful flight muscles, long front limbs, primary
flight feathers and barbules with hooklets. Macrochiropterans are the
ratite analogs of the bat world; they have been fruit eaters for a long time
and have lost their ability to echolocate. Microchiropteran fruit eaters have
only recently turned to these food sources, and owing to a deficiency with
their visual system, continues to need the ability to echolocate.
>These are not isolated species within insectivorous groups,
>they include almost all of the members of second largest family
>of Microchiroptera (Phyllostomatidae).
>
>Clearly, echolocation is advantageous for plant eating bats
>as well as insect eating ones. The fact that two genera
>of Megachiroptera also evolved the ability also confirms
>this.
Echolocation is advantageous for plant eating birds that are still "blind like
a bat." For bats with perfectly good eyesight, it is likely to degenerate, as
in the common ancestor of the extant macrochiropterans.
>With respect to another point. Cal King's suggestion
>that bats evolved flight from the tree down is certainly the
>commonly accepted model for aquisition of flight.
>
>
>Something to think about.
>
>Rick Toomey
>Illinois State Museum
>too...@museum.state.il.us
It is in addition the only biophysically plausible model although some
bird-theropod supporters insist that birds evolved flight from the ground up.
I also made the point that echolocation evolved before flight, as Harry Erwin
had postulated. And it is also the only plausible model, since flying in the
dark without the ability to echolocate would definitely be unfit, if not
downright foolhardy.
bull.net Cal King
>Echolocation is advantageous for plant eating birds that are still "blind like
>a bat."
Erratum:
I meant "plant eating bats" of course. No bird is known to echolocate.
Ralph W. Miller III
> >Echolocation is advantageous for plant eating birds that are still "blind like
> >a bat."
>
> Erratum:
>
> I meant "plant eating bats" of course. No bird is known to echolocate.
Wrong in either case; no bat is blind. And there are birds which use echolocation. Good
guess, though.
Ralph W. Miller III
> >I wrote:
> >The Teyler specimen of _Archaeopteryx_, originally dubbed _Pterodactylus
> >crassipes_ (the type specimen, yet!), is the most fragmentary scrap of skeletal
> >material yet identified as _Archaeopteryx_. Just some wing bones and feather
> >impressions.
>
> As Feduccia (1996:32) tells it, this specimen consists of "parts of one hand,
> miscellaneous leg and arm bones, feet, and some feather impressions."
My mistake. I still think that it looks like a piece of crap compared to any of the
other specimens, but maybe that's because the other specimens are so amazing.
> Now, YOU be the judge as to why anyone should put more weight on the detailed
> anatomical analyses of Romer, Simpson, Dollo et al. or on the total LACK of
> any anatomical analysis by Gauthier (1986) when it comes time to decide
> whether the similarities between Compsognathus and Archaeopteryx are
> convergent or homologous!
Thank you for clearing this up. I will now proceed to burn every book or scientific
journal that contradicts the gentlemen you choose to agree with. Then I will cancel
my subscriptions to _Nature_ and the _Journal of Vertebrate Paleontology_; so much
for all this cladistic fluff and nonsense. I will have none of it.
-- Ralph W. Miller III gbab...@best.com
"I've never heard such a pack of lies in all my born days."
bull.net Cal King
>Cal King wrote:
>
>> >Echolocation is advantageous for plant eating birds that are still "blind
> like
>> >a bat."
>>
>> Erratum:
>>
>> I meant "plant eating bats" of course. No bird is known to echolocate.
>
>Wrong in either case; no bat is blind. And there are birds which use
> echolocation. Good
>guess, though.
>
There are birds that ecolocate? That is news to me. Please elaborate and
give me references. You have piqued my curiosity. What method of modulation
do they use? FM or AM?
Bob Keeter
>
> I don't know where Mr. Keeter gets the idea that pterosaurs have "beady
> little
> eyes." It is just not true. The illustrations that I do see all show large
> orbital openings. Perhaps he just loves to say that particular phrase so
> much
> that he just doesn't care if pterosaurs really have big or small eyes. I am
> similar to those of birds. It may be noteworthy that one specimen of
> Archaeopteryx was misidentified at first as a pterosaur. The amount of
> convergent similarities between birds and pterosaurs is remarkable to say the
> least.
Unless I am badly mistaken (and certainly Mr. King will be quick to
sieze on any mistake, missplaced article or spelling!) pterosaur skull
fossils seem to always show evidence of a "Sclerotic Ring" whose inner
diameter will define the largest possible iris and therefore the
largest possible aperture for light to enter the eye. From the
pictures and sketches that I have availble SOME of the pterasaur
species seem to have very small eyes, or at least iris openings in the
sclerotic ring are quite small for such a large animal.
Ah well, I guess that I must simply concede defeat to the obviously
superior intellectual prowness and powers of deduction! Wait a minute,
how can I really concede defeat when all I was trying to do was ask a
few questions? Ohhell, it just dont matter! Count coup, all who
desire!
Regards
bk
p.s. Yes "beady little eyes" is quite a catchy little phrase. Wish I
had invented it! ;-)
bull.net Cal King
>
>> >The Teyler specimen of _Archaeopteryx_, originally dubbed _Pterodactylus
>
>> >crassipes_ (the type specimen, yet!), is the most fragmentary scrap of
> skeletal
>> >material yet identified as _Archaeopteryx_. Just some wing bones and
> feather
>> >impressions.
>>
>> As Feduccia (1996:32) tells it, this specimen consists of "parts of one hand,
>> miscellaneous leg and arm bones, feet, and some feather impressions."
>
> of the
>other specimens, but maybe that's because the other specimens are so amazing.
What is amazing is that the discoverer of this specimen is the same person who
had found the first feather belonging to Archaeopteryx. What is amazing is
that Ostrom was able to see the feather impressions on this specimen. What is
amazing is that Ostrom was able to tell the difference between Compsognathus
and another specimen of Archaeopteryx misidentified as Compsognathus.
>> Now, YOU be the judge as to why anyone should put more weight on the detailed
>> anatomical analyses of Romer, Simpson, Dollo et al. or on the total LACK of
>> any anatomical analysis by Gauthier (1986) when it comes time to decide
>> whether the similarities between Compsognathus and Archaeopteryx are
>> convergent or homologous!
>
>Thank you for clearing this up. I will now proceed to burn every book or
> scientific
>journal that contradicts the gentlemen you choose to agree with. Then I will
> cancel
>my subscriptions to _Nature_ and the _Journal of Vertebrate Paleontology_; so
> much
>for all this cladistic fluff and nonsense. I will have none of it.
>
>-- Ralph W. Miller III gbab...@best.com
>
>"I've never heard such a pack of lies in all my born days."
That is something that I never suggested. I only ask you why I should put
more weight on an opinion that did not rely on careful observations than
earlier opinions that did. Ostrom, for example, has shown what careful
observation can do for scientific progress; his careful observations resulted
in two additional specimens of Archaeopteryx. Similarly, careful
observations by Dollo, Simpson, Romer et al. have shown us that the
similarities between birds and theropods are convergences.
May be I should not complain too much because, as S. J. Gould often points
out, science does not march as much as it staggers towards a better
understanding of nature. An occasional step or two backwards is perhaps the
norm in science.
bull.net Cal King
>
>>
>> I don't know where Mr. Keeter gets the idea that pterosaurs have "beady
>> little
>> eyes." It is just not true. The illustrations that I do see all show large
>> orbital openings. Perhaps he just loves to say that particular phrase so
>> much
>> that he just doesn't care if pterosaurs really have big or small eyes. I am
>> only raising this point for the sake of clarity and accuracy. BTW, I see no
>> problem with the positioning of the eyes in pterosaurs. Their placement is
>> similar to those of birds. It may be noteworthy that one specimen of
>> Archaeopteryx was misidentified at first as a pterosaur. The amount of
>> convergent similarities between birds and pterosaurs is remarkable to say the
>
>> least.
>
>Unless I am badly mistaken (and certainly Mr. King will be quick to
>sieze on any mistake, missplaced article or spelling!) pterosaur skull
>fossils seem to always show evidence of a "Sclerotic Ring" whose inner
>diameter will define the largest possible iris and therefore the
>largest possible aperture for light to enter the eye. From the
>pictures and sketches that I have availble SOME of the pterasaur
>species seem to have very small eyes, or at least iris openings in the
>sclerotic ring are quite small for such a large animal.
So, is that where you get the idea that pterosaurs have "beady little eyes?"
FYI, the much maligned (by you) Encyclopedia Britannica has this to say about
pterosaurs:
"The eyes were LARGE, and the eyeball, as in many birds, was reinforced
by a series of bony plates (sclerotic ring) lying in its walls." (emphasis
mine).
FYI, the domestic chicken has a sclerotic ring as well. But I seem to
remember you claiming that birds have large eyes as opposed to the beady
little ones found in pterosaurs. How can that be if both have sclerotic
rings?
But that is okay I guess. I already know that you are here merely to "stir
the pot." We all can use a laugh now and then, as long as we know that you
are just joking. I apologize if I took you too seriously before. :( [That,
BTW, is not a frown, but a flamingo's smiley, ha ha ha.]
Ben Waggoner
> That is something that I never suggested. I only ask you why I should put
> more weight on an opinion that did not rely on careful observations than
> earlier opinions that did. Ostrom, for example, has shown what careful
> observation can do for scientific progress; his careful observations resulted
> in two additional specimens of Archaeopteryx. Similarly, careful
> observations by Dollo, Simpson, Romer et al. have shown us that the
> similarities between birds and theropods are convergences.
But the last time (OK, the only time) I heard Ostrom speak, he
was quite definitely in favor of a theropod-bird link, and he
specifically mentioned detailed features shared by birds and
dromaeosaurs. Whose set of careful observations are you in favor
of? Wait, don't answer that, it was a rhetorical question. . .
--
Ben
And how did I get sucked into this anyway? Who cares about the
phylogeny of two minor branches of the small phylum Chordata,
anyway?
Tom Maier
>
>And how did I get sucked into this anyway? Who cares about the
>phylogeny of two minor branches of the small phylum Chordata,
>anyway?
It's just the expression of typical self-centered behavior
found in the chordate phylum. You never see mollusca
writing books about themselves, do you?
Tom
Harry Erwin
> [[ This message was both posted and mailed: see
> the "To," "Cc," and "Newsgroups" headers for details. ]]
>
>
> Rick Toomey
> Illinois State Museum
> too...@museum.state.il.us
>
One problem with active echolocation is that the signal is about 60-100
dB louder than the return--loud enough to damage the hair cells. The
isolated cochlea is thought to help mute the signal before it reaches
the hair cells. It's probably worth looking for in the fossils.
--
Harry Erwin, <http://mason.gmu.edu/~herwin>, Sr SW Analyst,
PhD cand (informatics/computational sci) modeling how bats
echolocate (def Nov?), and Adj Prof of CS (data struct/adv C++).
Harry Erwin
> In article <37F81D0D...@best.com>, "Ralph W. Miller III"
<gbab...@best.com> wrote:
> >Cal King wrote:
> >
> >> >Echolocation is advantageous for plant eating birds that are still "blind
> > like
> >> >a bat."
> >>
> >> Erratum:
> >>
> >> I meant "plant eating bats" of course. No bird is known to echolocate.
> >
> >Wrong in either case; no bat is blind. And there are birds which use
> > echolocation. Good
> >guess, though.
> >
> >-- Ralph W. Miller III gbab...@best.com
>
> There are birds that ecolocate? That is news to me. Please elaborate and
> give me references. You have piqued my curiosity. What method of modulation
> do they use? FM or AM?
From Suthers and Hector (1987)
"Oilbirds, Steatornis caripensis, live in colonies in caves, within
which they navigate by echolocation (Griffin 1953, Snow 1961). The
sonar "clicks" of these nocturnal birds typically last about 40 to 80 ms
and are emitted at repetition rates up to about 12/s. Most of the
acoustic energy lies between 1 and 15 kHz."...
Produced in the syrinx. Wideband.
--
Harry Erwin, <http://mason.gmu.edu/~herwin>, Sr SW Analyst,
PhD cand (informatics/computational sci) modeling how bats
echolocate (def Sept), and Adj Prof of CS (data struct/adv C++).
bull.net Cal King
>Cal King wrote:
>
>> That is something that I never suggested. I only ask you why I should put
>> more weight on an opinion that did not rely on careful observations than
>> earlier opinions that did. Ostrom, for example, has shown what careful
>> observation can do for scientific progress; his careful observations resulted
>> in two additional specimens of Archaeopteryx. Similarly, careful
>> observations by Dollo, Simpson, Romer et al. have shown us that the
>> similarities between birds and theropods are convergences.
>
>But the last time (OK, the only time) I heard Ostrom speak, he
>was quite definitely in favor of a theropod-bird link, and he
>specifically mentioned detailed features shared by birds and
>dromaeosaurs. Whose set of careful observations are you in favor
>of? Wait, don't answer that, it was a rhetorical question. . .
Don't conflate observation with hypothesis. Ostrom has never mistaken a bird
for a theropod or vice versa. He knows that these two groups are distinct.
OTOH, many cladists conflate birds with theropods, clothing theropods with
feathers and misidentifying mole-like characters in Mononykus as evidence that
it is a bird. Ostrom is not fooled. He knows from careful observation that
Mononykus is a fleet-footed theropod, not a bird.
Ostrom's *hypothesis* of a close relationship between birds and theropods is
based on a phenetic resemblance between these two DISTINCT groups. Whether
these phenetic resemblances are in fact homologous is open to question.
According to Feduccia (1996), Ostrom paid little attention to the homology
between these resemblances, and apparently neither did the cladists since they
did not examine these characters in detail. Thus both Ostrom and the cladists
have converged on the same conclusion about a bird-theropod nexus because both
relied on similarities without regard to homology.
Little wonder cladistics has been called phenetics in disguise.
Rick Toomey
I presume that the fact that some birds echolocate is news
to Cal King because he posted his message before my posting that
mentioned specifically which ones do so reached his server.
I suppose that his question counts as taking me up on my offer
to post references concerning the echolocation in birds. As
I noted in my earlier posting, I have not looked closely as the issue,
and cannot discuss the details of their use of echolocation, but
I can supply some references so that people can find their own
answers.
Two different groups of birds are known to use echolocation. They
are the oilbirds (genus Steatornis) and cave swiftlets (genera
Collocialia and Aerodramus). References on their echolocation include
the following (complied from a variety of sources):
Coles, R.B., Konishi, M. and Pettigrew, J.D. (1987) Hearing and
echolocation in the Australian Grey Swiftlet, Collocalia
spodiopygia. Journal of Experimental Biology, 129: 365-371.
Fenton, M.B. (1975) Acuity of echolocation in Collocalia
hirundinacea (Aves: Apodidae), with comments on the distribution
of echolocating swiftlets and molossid bats. Biotropica
7: 1-7.
Fullard, J.H., Barclay, R.M.R., and Thomas, D.W. (1993) Echolocation
in free-flying atiu swiftlets (Aerodramus sawtelli). Biotropica
25: 334-339.
Griffin, D.R. (1953) Acoustic orientation in the oilbird, Steatornis
Proceedings of the National Academy of Sciences 39: 884-893.
Griffin, D.R. (1986) Listening in the Dark. Ithaca, NY: Comstock
Publishing Associates.
Griffin, D.R. and Suthers, R.A. (1970) Sensitivity of echolocation
in cave swiftlets. Biological Bulletin 139: 495-501.
Henson, O.W. and Schnitzler, H.-U. (1980) Performance of airborne
animal sonar systems II. vertebrates other than Microchiroptera.
IN (R.G. Busnel and J.F. Fish, eds.) Animal Sonar Systems
New York: Plenum. p. 183-195.
Medway, Lord (1959) Echolocation among Collocalia. Nature 184:
1352-1353.
Medway, Lord (1967) The function of echonavigation among swiftlest.
Animal Behavior 15: 416-420.
Novick, A. (1959) Acoustic orientation in the cave swiftlet.
Biological Bulletin 117: 497-503.
Pettigrew, J.D. (1985) Echolocation. IN (B. Campbell and E. Lack, eds.)
A Dictionary of Birds. Calton: T. & A.D. Poyser.
Sales, G. and Pye, D. (1974) Ultrasonic Communications by Animals,
London: Chapman and Hall
Hope these provide a start.
As an interesting side light, both the edible-nest and black-nest
swiftlets, whose nests are used in making bird nest soup, are
echolocating species.
Rick Toomey
Illinois State Museum
too...@museum.state.il.us
bull.net Cal King
>Cal King <getulus@no bull.net> wrote:
>
>> In article <37F81D0D...@best.com>, "Ralph W. Miller III"
><gbab...@best.com> wrote:
>> >Cal King wrote:
>> >
>> >> >Echolocation is advantageous for plant eating birds that are still "blind
>> > like
>> >> >a bat."
>> >>
>> >> Erratum:
>> >>
>> >> I meant "plant eating bats" of course. No bird is known to echolocate.
>> >
>> >Wrong in either case; no bat is blind. And there are birds which use
>> > echolocation. Good
>> >guess, though.
>> >
>> >-- Ralph W. Miller III gbab...@best.com
>>
>> give me references. You have piqued my curiosity. What method of modulation
>> do they use? FM or AM?
>
>
>"Oilbirds, Steatornis caripensis, live in colonies in caves, within
>which they navigate by echolocation (Griffin 1953, Snow 1961). The
>sonar "clicks" of these nocturnal birds typically last about 40 to 80 ms
>and are emitted at repetition rates up to about 12/s. Most of the
>acoustic energy lies between 1 and 15 kHz."...
>
>Produced in the syrinx. Wideband.
Thanks, I did a little research myself. There are two known groups of birds
that echolocate. The Oilbirds is one of them and an unrelated group, the
swiftlets, the saliva of which is the source for bird's nest soup, is the
other. Both groups dwell in caves and use sound audible to human ears to
echolocate and navigate in total darkness.
Hence we have unequivocal evidence that echolocation in volant vertebrates
have arisen at least 4 times, at least twice in birds and twice in bats, since
microchiropterans and macrochiropterans have different echolocation systems.
And it shows how easily echolocation can evolve, much more easily than flight.
Hence your assertion that echolocation appeared among arboreal, nocturnal,
non flying animals appear to be on solid ground.
bull.net Cal King
>Hello,
>
> I presume that the fact that some birds echolocate is news
>to Cal King because he posted his message before my posting that
>mentioned specifically which ones do so reached his server.
Quite correct. I have since done a little research and come up with some
generalities. Thanks for the references. It seems that based on the fact
that echolocation has arisen multiple times in birds that the
macrochiropterans were indeed degenerate microchiropterans that had lost their
ancestral ability to echolocate and re-evolved a different system. And
because it is so easy to evolve echolocation that different birds can do it
independently, there is little doubt that echolocation evolved first before
bats evolved the ability to fly, since flight has only evolved three times
among vertebrates, and echolocation at least 4 times (if not more) in the same
group.
Rick Toomey
Cal King wrote:
> I also made the point that echolocation evolved before flight, as Harry Erwin
> had postulated. And it is also the only plausible model, since flying in the
> dark without the ability to echolocate would definitely be unfit, if not
> downright foolhardy.
Although Cal is correct that the "echolocation first" is one to be
considered, he is incorrect that "it is also the only plausible model."
More on that in a momment, but first I must address his stated
basis for this conclusion.
His basic premise "flying in the dark without the ability to
echolocate would definitely be unfit." is clearly incorrect.
Numerous species of noctournal bird (including owls and nightjars)
show that it is perfectly safe to do so. The fact that
something like 200 species of Megachiroptera do so as well
means that it can be done. (By the way, the flying foxes and
their allies are Megachiroptera NOT Macrochiroptera, as
indicated by Cal King in a couple of posts.)
In addition, several mammalian gliders also seem to have
no problem manuevering through forests without the benefit
of echolocation (flying squirrels, gliding possums, and
colugos).
His premise assumes that the earliest bats had poor eyesight
to begin with, so they would need echolocation to begin
flying. No one has shown this to be true. In fact,
modern bat eyesight does not even support the idea.
AIt is important that bats are not blind. Many
(both Microchiroptera and Megachiroptera) have quite
good eyesight, and eyesight seems to play a major role
in long-range navigation. Some insectivorous Microchioptera
actually use eyesight for catching prey. For example, the
California leaf-nosed bat (Macrotus californicus) was observed
in the laboratory under various conditions. When
illumination was that of a bright moolight night, it used
echolocation to locate insect prey only 1/3 of the time. The
other 2/3 of the time it used vision. At lower light
levels it still used vision a portion of the time.
Macrotus' vision is not particularly better than any other
Microchiroptera (Altringham, 1996). Altringham notes (p. 108)
"The eyesight of many bats appears to be as good as that of
Macrotus and other small, nocturnal mammals, and vision
may play a greater role than we imagine in the foraging
of other bat species, too." Note, foraging is much more
demanding in terms of vision than would be obstacle
avoidance.
So, if Cal King's suggestion that navigating in the air
in the dark without echolocation is "downright foolhardy" is
clearly incorrect, is his conclusion that "echolocation
first" is the only plausible model for bat evolution
correct?
I would say no. It is one hypothesis. Some people who
study bat evolution would agree that it is the most likely
scenario. Others would say that "flight first" is a more
likely scenario. Few, if any, serious bat workers would
say that one answer is the only one plausible. I'm certain
Cal King feels that he knows the subject better than
the people who actually research it; I would tend to
listen to people who are actively researching the topic.
As I noted earlier, Simmons and Geisler (1998) have suggested
that "flight first" is the only model that is actually
compatible with our current knowledge of bat phylogeny.
I provided detail on their hypothesis in an earlier
posting. However, not even they are willing to completely
discount "echolocation first." They simply find it to be
a less parsimonius solution, because it requires Megachiroptera
to lose a perfectly useful adaptation (echolocation) with
no selective reason.
In a different email message Cal King write:
> Hence we have unequivocal evidence that echolocation in volant vertebrates
> have arisen at least 4 times, at least twice in birds and twice in bats, since
> microchiropterans and macrochiropterans have different echolocation systems.
> And it shows how easily echolocation can evolve, much more easily than flight.
> Hence your assertion that echolocation appeared among arboreal, nocturnal,
> non flying animals appear to be on solid ground.
Actually, the number of times flight and echolocation have evolved does
not provide any information on the order in which they arose in
bats. Consider, does the number of times feathers and flight
have arisen indicate in what order they are required to have occurred?
Also, the number of times echolocation has arisen that Cal King
gave is slightly off. Megachiroptera evolved it twice.
Microchiroptera evolved it once (3 for bats total). The number
of times birds evolved it is more problematic. Some species
of cave swiftlet use echolocation others do not. I have not
seen a phylogeny of swiftlets that indicates whether echolocation
arose more than once (although I would be a bit surprised
if it did).
References cited
Altringham, J.D., 1996, Bats: Biology and Behavior. Oxford:
Oxford University Press. 262pp.
Simmons N.B. and Geisler, J.H., 1998, Phylogenetic relationships of
Icaronycteris, Archaeonycteris, Hassianycteris, and Palaeochiropteryx
to extant bat lineages, with comments on the evolution of echolocation
and foraging strategies in microchiroptera. Bulletin of the
American Museum of Natural History, Number 235, New York. 182pp.
Rick Toomey
Illinois State Museum
too...@museum.state.il.us
Betty Cunningham
echolocating bats.
Whether they, themselves, echolocate I don't know but I suspect so.
-Betty
Rick Toomey wrote:
> Also, the number of times echolocation has arisen that Cal King
> gave is slightly off. Megachiroptera evolved it twice.
> Microchiroptera evolved it once (3 for bats total). The number
> of times birds evolved it is more problematic. Some species
> of cave swiftlet use echolocation others do not. I have not
> seen a phylogeny of swiftlets that indicates whether echolocation
> arose more than once (although I would be a bit surprised
> if it did).
--
Flying Goat Graphics
http://www.flyinggoat.com
(Society of Vertebrate Paleontology member)
-------------------------------------------<,D,><
Harry Erwin
> In article <37F8F33F...@museum.state.il.us>, Rick Toomey
<too...@museum.state.il.us> wrote:
> >Hello,
> >
> > I presume that the fact that some birds echolocate is news
> >to Cal King because he posted his message before my posting that
> >mentioned specifically which ones do so reached his server.
>
> Quite correct. I have since done a little research and come up with some
> generalities. Thanks for the references. It seems that based on the fact
> that echolocation has arisen multiple times in birds that the
> macrochiropterans were indeed degenerate microchiropterans that had lost their
> ancestral ability to echolocate and re-evolved a different system. And
> because it is so easy to evolve echolocation that different birds can do it
> independently, there is little doubt that echolocation evolved first before
> bats evolved the ability to fly, since flight has only evolved three times
> among vertebrates, and echolocation at least 4 times (if not more) in the same
> group.
Cal, you can echolocate (both actively and passively). It's called
'facial vision'. See Griffin, Listening in the Dark.
Harry Erwin
> Hello,
>
>
> Cal King wrote:
>
> > I also made the point that echolocation evolved before flight, as Harry
> > Erwin had postulated. And it is also the only plausible model, since
> > flying in the dark without the ability to echolocate would definitely be
> > unfit, if not downright foolhardy.
>
> Although Cal is correct that the "echolocation first" is one to be
> considered, he is incorrect that "it is also the only plausible model."
> More on that in a momment, but first I must address his stated
> basis for this conclusion.
>
Most mammals can echolocate (both actively and passively) to a
significant degree. Given the way the auditory system functions in
fish, I suspect echolocation is very primitive in chordates.
--
Harry Erwin, <http://mason.gmu.edu/~herwin>, Sr SW Analyst,
PhD cand (informatics/computational sci) modeling how bats
echolocate (def Nov), and Adj Prof of CS (data struct/adv C++).
Harry Erwin
> Some moths are capable of detecting the exact frequencies of
> echolocating bats.
> Whether they, themselves, echolocate I don't know but I suspect so.
I'm in the midst of preparing my defensible draft, and I've seen some
papers on the subject as I've looked up references. I don't have time
to check now, but I wouldn't be surprised either.
>
> -Betty
>
> Rick Toomey wrote:
> > Also, the number of times echolocation has arisen that Cal King
> > gave is slightly off. Megachiroptera evolved it twice.
> > Microchiroptera evolved it once (3 for bats total). The number
> > of times birds evolved it is more problematic. Some species
> > of cave swiftlet use echolocation others do not. I have not
> > seen a phylogeny of swiftlets that indicates whether echolocation
> > arose more than once (although I would be a bit surprised
> > if it did).
Rick Toomey
Harry Erwin wrote:
>
> Most mammals can echolocate (both actively and passively) to a
> significant degree. Given the way the auditory system functions in
> fish, I suspect echolocation is very primitive in chordates.
Thanks for the information. It is an important point to consider.
It calls for some refining the question to evaluate the various
hypotheses adequately.
The question becomes (as I see it), did the earliest bats echolocate
to a greater degree than is seen in most modern Megachiroptera?
If so, I would say that is an "echolocation first" hypothesis,
which would call for the loss of a more developed echolocation
in Megachiroptera.
If not, I would call that a "flight first" hypothesis. And
Microchiroptera developed an elaboration of the basal mammal
ability (possibly basal chordate, as you note) to echolocate.
bull.net Cal King
<too...@museum.state.il.us> wrote:
>His basic premise "flying in the dark without the ability to
>echolocate would definitely be unfit." is clearly incorrect.
>Numerous species of noctournal bird (including owls and nightjars)
>show that it is perfectly safe to do so.
Let me point out that owls have acute hearing, which may help them in
navigation at night. According to Feduccia (1996), molecular data shows that
nightjars, not hawks, are the closest living relatives of owls. So perhaps
the ability of nightjars to navigate at night may have something to do with
good hearing as well. If you have any info. on how nightjars catch insects, I
would appreciate it.
> The fact that
>something like 200 species of Megachiroptera do so as well
>means that it can be done.
Do they really fly around at night as much as the microchiropterans do?
>(By the way, the flying foxes and
>their allies are Megachiroptera NOT Macrochiroptera, as
>indicated by Cal King in a couple of posts.)
I stand corrected.
>In addition, several mammalian gliders also seem to have
>no problem manuevering through forests without the benefit
>of echolocation (flying squirrels, gliding possums, and
>colugos).
Gliding is very different than flying. Gliders may not glide all the time.
They may only glide on occasion, and may or may not glide when they can't see
where they are going.
>His premise assumes that the earliest bats had poor eyesight
>to begin with,
That is not my assumption. I actually think that the bat precursors probably
had large eyes, adapted for nocturnal vision (similar to those found on
nocturnal primates), but as echolocation evolved and became the dominant
sense, bat eyes underwent reversal.
>so they would need echolocation to begin
>flying. No one has shown this to be true.
No one has found a protobat yet.
> In fact,
>modern bat eyesight does not even support the idea.
>
>AIt is important that bats are not blind. Many
>(both Microchiroptera and Megachiroptera) have quite
>good eyesight, and eyesight seems to play a major role
>in long-range navigation. Some insectivorous Microchioptera
>actually use eyesight for catching prey. For example, the
>California leaf-nosed bat (Macrotus californicus) was observed
>in the laboratory under various conditions. When
>illumination was that of a bright moolight night, it used
>echolocation to locate insect prey only 1/3 of the time. The
>other 2/3 of the time it used vision. At lower light
>levels it still used vision a portion of the time.
>Macrotus' vision is not particularly better than any other
>Microchiroptera (Altringham, 1996). Altringham notes (p. 108)
>"The eyesight of many bats appears to be as good as that of
>Macrotus and other small, nocturnal mammals, and vision
>may play a greater role than we imagine in the foraging
>of other bat species, too." Note, foraging is much more
>demanding in terms of vision than would be obstacle
>avoidance.
Thanks for the info dispelling a common myth. However, it has little to do
with the evolution of echolocation per se. It may be true that bats may be
able to use their eyesight when there is light, but when there is no light,
even birds have evolved echolocation.
>So, if Cal King's suggestion that navigating in the air
>in the dark without echolocation is "downright foolhardy" is
>clearly incorrect,
No, it is not clearly incorrect. I give you credit for showing that bats have
good eyesight and that some birds do fly around catching insects and rats at
night. But nocturnal birds are extraordinary cases and represent perhaps just
a single case of nocturnal adaptation among birds, since sister taxa the
nightjars and owls may well be nocturnal because their most recent common
ancestor is nocturnal. Most birds are diurnal for a very good reason: they
just can't see in total darkness. Nothing can do that. Imagine a protobat
without echolocation and without the ability to fly. Would it launch itself
into the air, not being able to see where it is going or where it may land,
and with no assurance that it will catch anything at all? Does any extant
gliders without the ability to ecolocate ever try to catch insects on the wing
at night while gliding? I don't think so. So, why would bat precursors do
THAT?
> is his conclusion that "echolocation
>first" is the only plausible model for bat evolution
>correct?
I still think it is.
>I would say no.
We disagree.
> It is one hypothesis.
I have seen the alternatives. One of them requires quantum evolution and
simultaneous evolution of echolocation and flight. Possible but not probable.
The other alternative is also not very plausible, because there simply is no
non-flying vertebrate which makes a living catching insects on the wing by
lauching itself in the air. I have seen more than one house cat catch insects
on the wing with their front paws, but they don't do it by launching
themselves from a tree. Doing it in the dark is even more foolhardy.
> Some people who
>study bat evolution would agree that it is the most likely
>scenario. Others would say that "flight first" is a more
>likely scenario.
But that begs the question. Why would proto-bats evolve flight at all? What
selective advantage would it confer to an arboreal animal? Plenty of arboreal
animals have never evolved flight because of the anatomical price flyers must
pay. Flight has evolved only rarely, and in fact, flightlessness has evolved
far more often. So even though some workers may think that flight originated
before echolocation, they face the problem of explaining why it would be
adaptive to fly at all. Gliding is far more efficient energetically than
flying.
> Few, if any, serious bat workers would
>say that one answer is the only one plausible. I'm certain
>Cal King feels that he knows the subject better than
>the people who actually research it; I would tend to
>listen to people who are actively researching the topic.
That is your prerogative. In fact, I often defer to authority if I know
nothing about a certain subject. Whenever possible, however, I like to do my
own thinking and come to my own conclusions.
>As I noted earlier, Simmons and Geisler (1998) have suggested
>that "flight first" is the only model that is actually
>compatible with our current knowledge of bat phylogeny.
That is their opinion. I happen to disagree.
>I provided detail on their hypothesis in an earlier
>posting. However, not even they are willing to completely
>discount "echolocation first."
For very good reason. It makes a lot of sense to be able to echolocate before
one attempts to learn to fly in the dark.
> They simply find it to be
>a less parsimonius solution, because it requires Megachiroptera
>to lose a perfectly useful adaptation (echolocation) with
>no selective reason.
There is a very good selective reason to lose the ability to echolocate: they
don't need it. Besides, it may be more adaptive for a fruit bat to have a
generalized mouth (in order to consume fruit) instead of one that must be
specialized to emit high frequency sounds.
>In a different email message Cal King write:
Pardon me. I did NOT send you any email messages, unlike that troll who likes
to "stir the pot." You are referring to a Usenet post instead.
>> Hence we have unequivocal evidence that echolocation in volant vertebrates
>> have arisen at least 4 times, at least twice in birds and twice in bats,
> since
>> microchiropterans and macrochiropterans have different echolocation systems.
>
>> And it shows how easily echolocation can evolve, much more easily than
> flight.
>> Hence your assertion that echolocation appeared among arboreal, nocturnal,
>> non flying animals appear to be on solid ground.
>
>Actually, the number of times flight and echolocation have evolved does
>not provide any information on the order in which they arose in
>bats. Consider, does the number of times feathers and flight
>have arisen indicate in what order they are required to have occurred?
Since echolocation has evolved far more often than flight, it can indeed
evolve quite easily than flight. Hence it is more likely to have evolved
first. Besides, it makes no sense for a bat to evolve flight if it does not
already have the means to catch insects using echolocation during flight. I
doubt that bats evolved as diurnal flyers, because they would have been in
direct competition with birds and would never have evolved. Competition would
have eliminated these early clumsy flyers that tried to compete directly with
the birds. Hence the most likely circumstance under which bats perfected
their flying ability would be as a nocturnal, arboreal insect eater with the
ability to echolocate, since it simply makes no sense to try to fly in total
darkness with the hope that one may chance upon an insect or two by sheer good
luck. But if one can echolocate already, then it makes perfect sense to
launch oneself in the air in the dark looking for insects because the chances
of catching one is more realistic. And the more time one is able to stay in
the air echolocating and catching insects, the more adaptive one is.
According to this scenario, it would be advantageous for a gliding,
echolocating bat to evolve flight to stay in the air catching more insects.
bull.net Cal King
>
>Cal, you can echolocate (both actively and passively). It's called
>'facial vision'. See Griffin, Listening in the Dark.
That is an interesting claim. I never even knew it myself. I will certainly
give it a try, after I read that reference of course. For now, I prefer to
carry a flash light. :)
bull.net Cal King
allow them to catch insects on the wing, meaning that they catch insects by
"netting" them in the air. This is a mode of predation that is not found in
any known bat, and it is doubtful that the earliest bats netted insects while
flying in the air. Hence it is one more clue that bats must have had the
ability to echolocate before they attempted to catch insects on the wing by
launching themselves in the air. In fact, if they had enormous gaping mouths
to begin with, they wouldn't have had to evolve echolocation in the first
place.
Reference
Feduccia, A. 1996. The origin and evolution of birds. Yale University
Press.
Robert Wilson
around the eyes is an anatomical adaptation that owls use to assist in
improving their nighttime navigation.
--
Bob Mozark
Betty Cunningham
for a while.
Cal said:
"nightjars have enormous gaping mouths that allow them to catch insects
on the wing, meaning that they catch insects by "netting" them in the
air. This is a mode of predation that is not found in any known bat,
and it is doubtful that the earliest bats netted insects while flying in
the air."
Netting is EXTREMELY COMMON amongst North American insectivorous bats.
the bat discovers a bug via echolcation - the bat approaches the bug -
the bat scoops the bug up (in flight) using it's interfemoral membrane
EXACTLY like a lacrosse net -the bat immedialy swings its lower half up
towards it's head and scoops the bug into it's mouth
Bat Conservation International can provide more than enough slow-motion
video of bats doing this very thing (you want a copy of THE SECRET WORLD
OF BATS, but the NAT GEO specials on bats and the NOVA specials on bats
usually also show at least one bat doing this)
http://www.batcon.org/ (homepage)
-Betty Cunningham
further reading:
Title------[ Bat Biology and Conservation ]
Year-------[ 1998 ]
Publisher--[ Smithsonian Institution ]
ISBN-------[ 1-56098-825-8 ]
Comments---[ Edited by: Thomas H. Kunz and Paul A. Racey ]
Keywords---[ interfamilial relationships of bats, Phylogeny of the Bat
family Hipposideridae, Phylogeny of Neotropical Short-Tailed friut
bats, Carollia spp: Phylogenetic Analysis of Restriction Site Variation
in mtDNA, Phylogenetic Accuracy, Stability, and Congruence:
Relationships within and among the New World Bat Genera Artibeus,
Dermanura, and Koopmania, A Southern Origin for the Hipposideridae
(Microchiroptera)? Evidence from the Australian Fossil Record,
Morphological Adaptations for Flight in Bats, Skin and Bones:
Functional, Architectural, and Mechanical Differentiation in the Bat
Wing, Chiropteran Muscle Biology: A Perspective from Molecules to
Function, Form, Function, and Evolution in Skulls and Teeth of Bats,
Chiropteran Hindlimb Morphology and the Origin of Blood Feeding in
Bats, Interspecific and Intraspecific Variation in Echolocation Call
Frequency and Morphology of Horseshoe Bats, Echolocation, Conservation
Biology, Functional Morphology, Phylogeny and Evolution ]
DateEntered[ 11-19-98 ]
Author---[ Anderson, G.M. ]
Title---[ A Model for the Bat Versus Moth Pursuit-evasion Problem ]
Journal---[ Acoustical Society of America Journal (Suppl.) ]
Year---[ 1978 ]
Volume---[ 64 ]
Pages---[ S88 ]
Author---[ Norberg, U.M. ]
Title---[ Some Advanced Flight Manoeuvers of Bats ]
Journal---[Journal of Experimental Biology]
Year---[1976]
Volume---[64(2)]
Pages---[489-495]
Author---[ Hoying, K.M. and T.H. Kunz ]
Title---[ The Development of Flight and Foraging in Pipistrellus
subflavus, (Chiroptera: Vespertilionidae) ]
Year---[1983]
Information---[Manuscript]
Language---[English]
Author---[ McNab, B.K. ]
Title---[ Evolutionary Alternatives in the Physiological Ecology Of Bats
]
Book---[In Thomas H. Kunz (Ed.) Ecology of Bats P(Plenum Press, New York
and London)]
Year---[1982]
Pages---[151-200]
Author---[ Norberg, U.M. ]
Title---[ Flight, Morphology and the Ecological Niche in Some Birds and
Bats ]
Journal---[Zoological Society of London. Symposia issue has separate
title: Vertebrate Locomotion.]
Year---[1981]
Volume---[48]
Pages---[173]
--------------------
additional reading on bats feeding on aquatic forms:
Author---[ Barclay, R.M.R.; M.B. Fenton; M.D. Tuttle and M.J. Ryan ]
Title---[ Echolocation Calls Produced by Trachops cirrhosus (Chiroptera:
Phyllostomatidae) While Hunting for Frogs ]
Journal---[ Canadian Journal of Zoology ]
Year---[ 1981 ]
Volume---[ 59 (5) ]
Pages---[ 750-753 ]
--------------------------
Cal King wrote:
>
> According to Feduccia (1996:320), nightjars have enormous gaping mouths that
> allow them to catch insects on the wing, meaning that they catch insects by
> "netting" them in the air. This is a mode of predation that is not found in
> any known bat, and it is doubtful that the earliest bats netted insects while
> flying in the air. Hence it is one more clue that bats must have had the
> ability to echolocate before they attempted to catch insects on the wing by
> launching themselves in the air. In fact, if they had enormous gaping mouths
> to begin with, they wouldn't have had to evolve echolocation in the first
> place.
Betty Cunningham
bull.net Cal King
>Cal, You really got to read up on bats -ferget those boring ol' birds
>for a while.
>
>Cal said:
>"nightjars have enormous gaping mouths that allow them to catch insects
>on the wing, meaning that they catch insects by "netting" them in the
>air. This is a mode of predation that is not found in any known bat,
>and it is doubtful that the earliest bats netted insects while flying in
>the air."
>
>Netting is EXTREMELY COMMON amongst North American insectivorous bats.
>
>the bat discovers a bug via echolcation - the bat approaches the bug -
>the bat scoops the bug up (in flight) using it's interfemoral membrane
>EXACTLY like a lacrosse net -the bat immedialy swings its lower half up
>towards it's head and scoops the bug into it's mouth
This isn't netting. This is "scooping." The method employed by nightjars is
netting. They open their big wide mouth and just hope that some insects are
caught while they are flying. Presumably they frequent areas where insects
are in high enough density that they will get enough random hits. The feeding
method of nightjars is analogous to those of baleen whales or whale sharks, or
any other filter feeder, if I am not mistaken.