When calculating the number of independent events and trapping rates for a camera trap study, I used a specific time interval between sequences to determine independence for single individuals of the same species. However, what to do with gregarious species? If in a sequence there is more than 1 individual of the same species (even if I cannot ID them individually), should I count this as 1 event or count the total of events according to the number of individuals?
This is important when calculating trapping rates as they can vary a lot for large groups like Mangabeys and chimpanzees. I have only found 1 paper that mentions specifically this issue: Monroy-Vilchis Octavio et al., Fototrampeo de mamíferos en la Sierra Nanchititla, México: abundancia relativa y patrón de actividad. Rev. biol. Trop., 2011 Mar; 59(1): 373-383.
Usually the type of definition for independent event I find are similar to this one: “Consecutive photographs of the same species at the same site were deemed independent when there was at least 1-h interval between them” without specifying what happens when more than 1 individual is recorded in the same sequence.
Hello Rosa,
What kind of software do you use to analyse the data? In my team, we use Camera Base (http://www.atrium-biodiversity.org/tools/camerabase/), which allows you to specify the number of observed individuals for each photo/video and if it is a social group. So regarding your question - we would count it a single independent registration of a group of n individuals.
If the species is gregarious then you're essentially working with group trapping rates, rather than individual trapping rates. Having recorded the size of the observed groups you can then analyse this data further depending on your question/s (e.g. are smaller or larger groups captured more frequently).
Hope this helps!
Elitsa
fHello Elitsa,
Thank you for your response. I am using this new software:
https://www.zsl.org/zsl-camera-trap-data-management-and-analysis-package
It allows to specify the number of animals observed as well. The camera trapping rate is for the group with events associated at a group level.
It makes sense to analyse at a group level so the rates do not shoot up for some of the species. After i can pose other questions regarding the group size as you suggest.
Best
Rosa
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