Sex as a covariate in detecting cluster

[Eric Rexstad]

> > Fernanda:
> >
> > It is fine that you have used the characters "M" and "F" in your
> > data. You can use those as covariates after you have indicated to
> > MCDS that the field does not contain numbers, but rather contains
> > charters you wish to consider as "factors." Look at the screen
> > capture I will send separately from the project Amakihi that is
> > provided in the Sample Projects folder that comes with program Distance:
> >
> > The covariate "OBs" which are the initials of the observers making the
> > sightings, are indicated to be "factor" variables. Try this analysis
> > yourself by looking through the Amakihi Distance project.
> >
> > Of course clusters do not have genders, but Distance does not know
> > that. I suspect it would make your analysis most simple if you were
> > to analyse your data as detections of single individuals (whenever you
> > have sightings of a multi-individual cluster, you duplicate records
> > such that there are as many records (with perpendicular distances
> > equal) as there were animals in the cluster). Simulations described in
> >
> > Buckland, S.T., Plumptre A.J., Thomas, L. and Rexstad, E.A.. (2010)
> > Design and analysis of line transect surveys for primates
> > <http://www.springerlink.com/content/w975167n11kp8403//>.
> > /International Journal of Primatology/ *31*: 833-847, DOI
> > 10.1007/s10764-010-9431-5
> >
> > provide some justification for treating clusters as groups of individuals.
> >
> >
> > On 30/09/2013 16:44, Fernanda Alves wrote:
>> >> Hi everyone!
>> >>
>> >> I'm running analyses to estimate population density of a Gamebird species and most of my contacts were from single individuals but I also detected clusters and I was trying to run MCDS analyses using sex as a covariate since females are more elusive than males and my number of females is really low. When I ran the analyses I've got an error message from Distance and I believe that is because in the sex column of my data sheet I have M/F, for example. Is there a proper way to enter the data regarding sex in clusters.
>> >>
>> >> Another question, since most of my detection were of single individuals would it be better to analyse them as single contacts or I have to analyse as cluster?
>> >>
>> >>
>> >> Thanks,
>> >>
>> >> Fernanda Alves.
>> >>
>> >> --
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>> >>
>> >>
>> >>
> >
> > --
> > Eric Rexstad
> > Research Unit for Wildlife Population Assessment
> > Centre for Research into Ecological and Environmental Modelling
> > University of St. Andrews
> > St. Andrews Scotland KY16 9LZ
> > +44 (0)1334 461833
> > The University of St Andrews is a charity registered in Scotland : No SC013532

--
Eric Rexstad
Research Unit for Wildlife Population Assessment
Centre for Research into Ecological and Environmental Modelling
University of St. Andrews
St. Andrews Scotland KY16 9LZ
+44 (0)1334 461833
The University of St Andrews is a charity registered in Scotland : No SC013532


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[Fernanda Alves]

Hi everyone!

I'm running analyses to estimate population density of a Gamebird species=
and most of my contacts were from single individuals but I also detected=
clusters and I was trying to run MCDS analyses using sex as a covariate =
since females are more elusive than males and my number of females is rea=
lly low. When I ran the analyses I've got an error message from Distance =
and I believe that is because in the sex column of my data sheet I have M=
/F, for example. Is there a proper way to enter the data regarding sex in=
clusters.=20

Another question, since most of my detection were of single individuals w=
ould it be better to analyse them as single contacts or I have to analyse=

as cluster?


Thanks,

Fernanda Alves.

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[Fernanda Alves]

Hi Eric,

Thank you so much for writing me back!

I also think that it would be better to analyze my data as single
individuals rather than cluster. But since it wasn't possible to measure
the distance for each individual when a cluster was detected isn't there
any problem to use the same distance for the individuals in the cluster?

I was reading the paper that you've sent me and they said that you should
measure the distance to each individual in the cluster but I could not do
that in the field because individuals flushed as soon as they were
detected.

Many thanks,