"Hey! Oh, hello, fellas—all right—all right."
-- Jacob Kowalski feeding Newt's Mooncalves (WFT)
A Mooncalf is a strange creature with smooth pale gray skin and narrow legs with large hooves that only comes out of it’s burrow during a full moon. It’s eyes are very large and bulgy, they sit on the top of it’s head. It’s enormous flat hind feet leave intricate impressions on wheat fields when it dances (much to the confusion of Muggles). This is also believed to be a part of a Mooncalf mating ritual. Mooncalves are extremely shy of Muggles (FB).
Mooncalf dung that is harvested before the sun comes up makes a powerful fertilizer (FB). It is especially useful for growing Sopophorous beans (BoS).
The Mooncalves in Newt Scamander's case eat Mooncalf pellets (WFT). In turn, Mooncalves are a favorite prey of the Hodag (FB).
One of the questions in the first WOMBAT test asks (JKR-W1):
4. Your Friends wizard A and wizard B are in dispute over which of them owns a field in which Mooncalfs dance periodically. A accuses B of using nightly a Summoning Charm to collect the precious Mooncalf dung which is rightfully A's.
a. Improper use of Magic Office
b. Wizengamot
c. Pest Advisory Board
d. Improper Use of Magic Office and Wizengamot
e. Improper Use of Magic Office and Pest Advisory Board
f. Wizengamot and Pest Advisory Board
Commentary
Etymology
Historically, "mooncalf" refers mainly to a miscarried and usually deformed fetus of a cow or other animal. Occasionally, it was applied to similar human cases, as well. It refers to the belief that the cycle of the moon had adversely affected fetal development in these instances (source: Wikipedia). --BB
From the Web
"Mooncalf" from Harry Potter Wiki