Only two capture occasions ?

[oloide]

Dear Mark experts,

I would like to know if it is possible to estimate something sensible with only two capture occasions. I can not find a clear answer reading the Mark manual or the capture recapture literature.

More precisely, I have multiple occurence in each capture occasion thus I estimated the total population size (using Capwire software). I then used the ratio between population sizes as a estimation of the realized population growth rate (lambda according to the Pradel model).
But I would like to estimate a survival rate instead. Would it be possible?

Thank you so much in advance.

Oloide

[Jochen]

Oloide,

two capture occasions would not allow to estimate recapture probability p, hence survival estimation would be useless.

However, If "multiple occurence" means that each of your 2 occasions consisted of repeated trapping events at the same site, with some animals recaptured repeatedly and some not, you might split up your 2 occasions into smaller units and obtain estimates for p and Phi - but be sure to set the interval lengths correctly as they will vary within your data (see the basic chapters of "the book").

Hope this helps
Jochen