Frequently Asked Questions
FAQs will periodically be added to the pages for each software package below. Answers to the FAQs may or may not be provided (!) and users are encouraged to submit both proposed FAQs and answers via the forms on the pages. Submitted FAQs may or may not be included, at the sole discretion of the website manager. Please ask questions about the use of the software tools only, not about modeling in general or conservation issues.
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Q:> Dear all,
I am working on a supplemented bird population. Every year 1 year old captive-born individuals are released in the wild.
To develop accurate population viability models with vortex I need to keep track of supplemented individuals after the year of supplementation as mortality from age 1 to 2 and 2 to 3 is different between supplemented (captive-born) and wild-born individuals.I know that supplemented individuals can be specified (SUPPLEMENTS) in functions, but they only represents individuals supplemented that year, updated after each population is supplemented. Do you have any advice on how to keep track of supplemented individuals ? I thought of using "individual state variables", but I struggle to find a clear example useful for my study case.
Thank you for your time and help. A:> The easiest way to track who was supplemented is to use an Individual State variable (as you suspected). Create IS1 with Initialization function "=(Y>0)", Birth fn "0" and Transition fn "=IS1". A supplemented individual will have IS1 initialized, and it will happen after Year 0, so it will have IS1=1. All other individuals will have IS1=0. You can then use this IS1 to modify mortality (or other) rates for individuals that were added as supplements.
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