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Cronon33 t1_iu4utzt wrote

Reply to comment by iayork in Is it possible that only 4 moose imported to Newfoundland in 1904 could produce a viable modern population of 110,000 today? by SlipCritical9595

Thanks for this insight, I would have assumed at 4 individuals they'd surely be beneath the minimum viable population and destined for inbreeding depression

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iayork t1_iu52lpr wrote

Mostly that’s true. But given the right background, and a significant amount of luck, very small founder populations can expand enormously. This is very common in invasive species. The 200 million starlings in North America today arose from a few dozen in the late 1800s. Bull trout in Montana arose from two founders. A million Barbary Ground Squirrels arose from a single female.

Again, this is possible but not inevitable. Most such introductions will collapse due to inbreeding. But occasionally explosions can happen.

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Cronon33 t1_iu54o2o wrote

Right of course, there is no guarantee either way, at least with breeding individuals

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atomfullerene t1_iub56ki wrote

Minimum viable population is less of a rule and more of a guideline. Specifically speaking, it's usually defined as something like "the minimum population to have a 95% chance of survival for 100 years, in a population that isn't being specifically managed by people."

95% is a pretty high percentage, so there's a lot of "room" below it. Maybe 4 moose only have a (to pull a number out of the air) 25% chance of survival....but that's common enough that it isn't surprising to see it happened.

And furthermore, populations can have big advantages that mean their actual odds of survival are higher than the given percentage. For example, moose introduced onto an island with no competitors and no predators can expect to have a greater fraction of their offspring survive. And that means their population will more rapidly grow out of the danger zone.

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