Many species can't be bred in captivity,

We've been running a captive-breeding programme with the boreal toad ( Bufo boreas ) since 1995,

We've tried re-introducing them to the wild seven or eight times, but every time they die within a couple of years; if you don't get rid of the fungus, all you're doing is providing it with lunch.

You can give them the right habitat and food, but they may need specific light or heat or moisture or group size, otherwise the female won't ovulate - and it can take years to study that.

This species of bat has been observed capturing insects near the ground and vegetation, which suggests they have a wider repertoire of sonar-guided behavior than previously recognized. We thought the sonar strobe groups might be well suited to helping the bat distinguish a small object from the more complex background you would find in the wild.

I can't mate in captivity