Help determining best abundance estimator

[chimbioputo]

Hi all,

I have a long-term data set of >500 individuals caught opportunistically by farmers over a 20 year period. Captures are more of a response to either human-wildlife conflict, perceptions, etc. Due to this setting, sampling was not consistent and is likely to have varied largely across years. Also, exposure to trapping effort may not have been equal to all individuals particularly as trapping sites are bias to capture males.

The reason for this post it is because I am struggling to define what abundance estimator may be more appropriate for this data set. I was thinking about maybe considering each year as an occasion or at least 6 months. That would prevent the application of any robust design approach. However, maybe use the C/Jolly-Seber.

Any assistance is welcomed, please.

Thanks, Fabiano

[murray.efford]

Fabiano
I think the unpleasant truth is that the data you describe will not yield a useful estimate of abundance by any formal capture-recapture method (without strong and implausible assumptions, that is). Are there even recaptures? The typical farmer annoyed by a wild animal does not catch it and let it go! You might also have trouble defining the area that was sampled, as there seem to be no data on sampling effort (changing area is even more of a worry than changing intensity of sampling, if you don't have spatial effort data). My feeling is that you don't do anyone a service by pushing unsuitable data through fancy estimators. Of course, the data may be good for other things (e.g. as an index of conflict frequency).
Murray

[chimbioputo]

Thanks for your input, Murray.
All the issues you raised (and others), I have also been pondering about them, as I considered them to be fundamental. And yes, they are some (but very few) recaptures and a good number of animals have been released back at sites of capture. Also, some farmers have clearly reduced their trapping intensity over the years (we work closely with them). But I certainly agree data manipulation is not the best approach to do good science. Your expert opinion does help me know that that at this point (??) there is no estimator available that can be considered for data sets such the one I have for purposes of estimating abundance.
Much appreciated.
Fabiano

[cooch]

Fabiano
I think the unpleasant truth is that the data you describe will not yield a useful estimate of abundance by any formal capture-recapture method (without strong and implausible assumptions, that is)...

I'm afraid I must concur with Murray, for the reasons he listed.

[chimbioputo]

Sure, I agree with the all the comments. As they are things that I had considered but just needed an expert opinion.