Effort information when using hair traps

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stefano palmero

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Nov 19, 2025, 10:12:32 AM (13 days ago) Nov 19
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Hi all,
I would have a question regarding SCR modelling, and I thought you might help.
With camera traps, when a camera does not work, but an animal passes by, not accounting for the malfunctioning of the device would, of course, lead to an underestimation of g0. 
And this has to be accounted for when using any kind of detector. 
I will get a dataset with data from hair samples collected at sticks that were lured with valerian scent at the start of each week. That means the sticks get less appealing in the following days, similar to a trap that stops functioning, so to say. 
I was thinking I could arbitrarily set a day after which I consider the detector (the stick) as no longer able to attract (0 instead of 1).

Thanks!

Murray Efford

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Nov 19, 2025, 3:18:49 PM (13 days ago) Nov 19
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Two points:
1. In your case the 'usage' mechanism seems unduly arbitrary. Why not fit a temporal trend (~T) or equivalently use a time covariate?
2. Simulations suggest temporal variation in detection is not a big deal (Sollmann 2024; SECR book Ch 6)

stefano palmero

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Nov 21, 2025, 6:09:03 AM (11 days ago) Nov 21
to Murray Efford, secr
Hi Murray,
Thanks for the prompt reply, as always.
If I use g0~T, I don't need to provide the usage to the "trap" file?

Thanks

Dr. Stefano Palmero


Department of National Park Monitoring and Animal Management 

Freyunger Str. 2

94481 Grafenau

Germany



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Murray Efford

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Nov 25, 2025, 9:47:46 PM (7 days ago) Nov 25
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No, there's no connection to 'usage'. 'usage' and g0~T can be used together if, for example, there are days when some traps were not set. g0~T applies to captures at the traps that were set.

stefano palmero

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Nov 26, 2025, 3:43:44 AM (6 days ago) Nov 26
to Murray Efford, secr
I see, thank you.
Alternatively, I could also use the day as a covariate.

Thanks

Dr. Stefano Palmero


Department of National Park Monitoring and Animal Management 

Freyunger Str. 2

94481 Grafenau

Germany


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