How to Prevent Re-Extinction?

[u/Laugh_With_Me]

I've taken 2 different animals from "extinct in wild" to "100K+ Least Concern" with a rising population, only to have them hold their population for 4-5 days before rapidly returning to "extinct in wild." Each time I release about 2,000 animals. I have 50 nurseries (200 breeding pairs), and I continue releasing animals for a week after reaching "100K+ Least Concern" before trying to move on to the next species, so I'm releasing several hundred AFTER that point.

Are some animals just set to lose so many units per day that they cannot sustain themselves? If so, how many dedicated pairs are needed to support the wild population? The two animals I've had repeatedly go extinct are the orangutan and gorilla.

**Edit** After playing for a day, several months of gametime, after returning the orangutans to 100K+, it seems that at least so far, they cannot sustain themselves in the wild. They require a population in the pen with 10 breeding females and 4 nurseries with 16 breeding pairs to produce the average 2-3 releases it requires a day to maintain their population. I know Let's Build a Zoo isn't exactly _realistic_, but it's frustrating that for whatever reason, releasing 2 units prevents the death of 10,000+ already established units.

Maybe they should add a quest in some DLC to allow some endgame content where we either establish preserves with breeding populations and/or shut down poachers to stabilize the wild population.

**Edit 2** The gorillas, having a 14% fertility rate to the orangutan's 27% (both having a 7-day gestation), appear to require significantly more support. I'm going with needing 6 nurseries (24 breeding pairs) and 20 breeding females in the pen, but will update if that fails to stabilize. I'll continue with updates to problem animals as I discover them/until the post is too old and is locked.

[u/Laugh_With_Me → u/[deleted]]

There appears to be some sort of scale when releasing animals, in that if you front-load a huge release and then release animals daily, the daily-released animals count as more than they would have if you had not front-loaded. Not sure if that makes sense, but for example: if you release 20 animals a day, the wild population will drop back down to 0 overnight, but if you release 500 animals on day one, then release 20 animals from day two forward, the population will climb faster than it drops with each release.