Green and golden bell frog
There used to be so many green and golden bell frogs that people would catch them to feed to snakes or to use in school dissection classes.  By the 1990s, there were fewer green and golden bell frogs.  Scientists say this is because of habitat fragmentation, which means people building things in between places where the frogs live, and because of invasive species such as the mosquito fish that eat green and golden bell frog tadpoles.