few recaptures in age model

[apinya]

Hello,
I’m a new MARK user. I did mark-capture-recapture for cobra in 2 sites for 1 year. The cobras were classified their age to 3 classes (neonate, juvenile, and adult). I get a few recapture data, only 23 marked snakes were recaptured (from about 220 marked snakes). I’d like to calculate population size in each plot, and also look at survival of snake in each age-class. I thought that the age model may be appropriate for survival estimates since I have 3 difference age classes. But only 1-2 snakes recaptured while being across its age at marking. Most of snakes still are still in the age at marking. This species may reach adult at 3 year of age, but my study period is quite short. I wonder if my data is good enough for working on age model, and even get good estimates.
Another point about age class is that neonate hatches only certain time of each year, but I did survey before that time. In order to prepare input file for analyzing data together with adult and juvenile, I add “0” for those pre-hatch occasion, but still wonder do I need to fix parameter values somewhere else in MARK.
Thank you in advance for all answers.
Best regards,
Apinya

[claudiapenaloza]

Your treatment of the neonates seems correct... it would be equivalent to having captured juveniles or adults for the first time in the second, third, etc. encounter occassion (I am assuming you had several encounter occasions in your year of study).
With respect to the age specific model... if you only have 1-2 animals per age class that "aged" throughout your study, you do not have enough data to separate them into age classes.
Would splitting the age classes into two (e.g., neonates and juveniles/adults) make things any better?
Otherwise I would suggest grouping the data and calculating survival for all age classes together.

By the way, you have a "low" recapture rate, p=0.1, but you should still be able to get some meaningful estimates... however, your models will need to be very simple (constant and no groups, for example).

Good luck,
cp