closed population estimates of adults and juveniles

[nepsiva]

We carry out surveys of ranches to estimate zebra population size. On each survey we record all zebras seen and photograph them for individual identification based on stripes. Using this, we can then build capture histories for each individual, having repeated the survey 5 times in a short period. Using program Mark or program Capture, I can run the Otis et al (1978) models Mo, Mt, Mb, Mh, Mth etc to estimate population size. Running these models produces reasonable results (based on my field judgement) with tight confidence limits.

Now, I believe that one of the assumptions of these models is that animals act independently. To satisfy this, we therefore, exclude from the analyses all juveniles (who move with their mothers). However, this means that we can only derive a population estimate of the total number of adults. If we wanted to derive a total population estimate (including juveniles) how could we do that? Any ideas you have on this topic, would be most helpful.

Thanks for any suggestions.
Siva

[Fish_Boy]

You could use a group level attribute e.g., juvenile or adult in the INP file or use Covariates in the Design Matrix to test whether parameters vary based on group. You could also include analyses based on specific ranch or dazzle, by including these data as covariates or group information. This may allow you to look at variation in parameters spatially as well as by life stage. There is a good chapter in the manual on the use of design matrices.