Multi-state models with age structure

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Multi-state models with age structure

Postby X33277 » Tue Mar 12, 2019 9:32 pm

Hello, I am a new Mark user and inquiring about how to best set up a multi-state model with age structure. I have gotten as far as chapter 13 in the Mark book over the past several months but obviously have a long way to go..... In this current study there are 3 states with 2 age classes. I thought maybe about 6 states with each age class having its own 3 states and constraining psi so that the older age class cannot transition to any state of the younger age class. Perhaps 3 states with 2 age groups would work as well but not sure if it would be more or less appropriate. I am sure the best approach is obvious to most here.... so I am hoping for some suggestions.
Thanks for any advice.
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Re: Multi-state models with age structure

Postby simone77 » Tue Mar 19, 2019 5:48 am

I am afraid you have not been clear enough as to make possible someone can help you. Think of a state as some individual trait that changes in a dynamic and stochastic (non-deterministic) way along its life. Age is a dynamic individual trait but it is not a state (in capture-recapture jargon) because it changes in a deterministic way and, therefore, the model is not going to estimate the probability of transition between, say, age 1 to age 2.

A group, instead, is some fixed individual trait (it does not ever change as, for instance, sex in many species).

Age, group and states are treated in a different way in MARK (or any other software for capture-recapture modelling). States sometimes are related to age when, for instance, your state refer to the breeding status (non-breeder and breeder) but in many cases they don't. Also, six states are quite a few and it may mean a lot of parameters to be estimated (p from s1 to s2, p from s2 to s1, p from s1 to s3, ..., p from s6 to s5), is that realistic with the data you handle?

Anyway, it is really difficult to help you if you do not explain in mode detail your study system and your goals. May you please try?
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