One theory is that oral behaviors increase salivation and help buffer stomach acid.

Q.My 4-year-old gelding plays with his tongue every night in his stall at feeding time when he’s waiting on his hay (see video below or at bit.ly/2tMXPrc). Why would a horse do this? Is it because new teeth are growing in, or is he just bored?

—Jennifer, via email

A.Great video clip! This behavior goes by a few names, but lollying is probably the most common. I couldn’t appreciate if there was any sucking, as well. There are actually many variations of tongue and lip movements in various combinations and specific forms. All are pretty peculiar and very interesting. As far as I know, no one knows for sure why some horses do it