We are creating a customized PVA program that can predict the extinction threshold depending on the years input. Some example and specific scientific data needed are current population of the crocodiles, age structure, vital rates, mortality rates, hatchlings, carrying capacity, mean survival for each stage, sex ratio, number of occupied patches, and etc.
The only PVA factor we can only do is Density dependence. Spatial PVA related is not included.
If you guys have existing PVA studies of other animals, it would help us construct a program for it. We can change the subject animal because of the limited data of crocs. Any help would be appreciated.
Hi!
I also suggest you to check existing software on matrix population models & PVAs (RAMAS, Vortex) as a friendly start on the subject. If you don`t know the age of your crocs, maybe you can do a stage-structured population matrix by defining stages (i.e. egg, juvenile, subadult, adult or different size classes) instead of true age.
Once you have mastered RAMAS and Vortex, you can try code your matrices in R and do the simulations there (check existing R packages on demography/population biology). The advantage is that with R you can modify the script and control all your model is doing, but you need to be VERY familiar with R language.
Good luck!
Al
Hi,
HexSim is an alternative if you decide to make spatially-explicit and individual-based models. Otherwise, all the options cited before can be fitted. You can try R packages such as popbio and primer to construct stage (or age) -structured population matrix.
http://www.hexsim.net/
Good luck!
Hi,
Another way is to construct a simple code to study how demographic, environmental, and genetic stochasticity interact with each other and with deterministic factors, such as habitat quality. In this Thesis you can find a very good example:
Johnson, Heather Elizabeth, "Escaping the extinction vortex: identifying factors affecting population performance and recovery in endangered Sierra Nevada bighorn sheep" (2010).Theses, Dissertations, Professional Papers. Paper 379.
http://scholarworks.umt.edu/cgi/viewcontent.cgi?article=1398&context=etd
Attached you can find the code in BUGS
Best regards,
Jose
Hello,
SPOMSIM may be a model you also can use. MetaConnect also but it may be harder. You can have a look on the paper of Gunton et al. 2016 in JAE (Multi-criterion trade-offs and synergies for spatial conservation planning) for more details.
Best regards
Sylvain
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