From the Bogologist Field Guide (4th Edition):

“Bat Boglins simply shouldn’t be. Although Boglin legend tells of these winged creatures, who would swoop down from the highlands to carry small animals (and sometimes young Boglins) away in the dead of night, these are the kinds of stories one tells children in order to get them to behave. There has, in fact, never been a confirmed sighting until VERY recently. Looks like the stories are true.”