hi, dr. bill! My point was that Mrs. Bryne's definitions do not seem to match what tsuwm posted. I'm just a city-boy, but I'm pretty sure that "heifer" is not the same as "horse".

But I'd also not think that Mrs. B's "bounce" (implying a rebound from an opposite-direction motion) would fit the animal behavior you describe of "jumping straight up with legs straight".

Agreed that your hypothesized "communicative" reason for the animal behavior might be of use for a prey-animal. But would it seem of use to a predator, such as a cheetah?