Sheep and goats may not be known as party animals, but they’re increasingly at the center of the celebration as petting zoos grow in popularity for birthdays, graduations and other bashes.

Petting a gentle animal of any kind seems to appeal to everyone. Day-care centers, schools, churches and even nursing homes rent mobile zoos that will bring animals and handlers to them or organize trips to petting zoos.

“You can see the absolute joy as they are sitting there stroking some animal, particularly if it’s the first time in their life they have touched one,” said Sky Shivers, superintendent of Fairview Farms at the Los Angeles County Fair, 35 miles east of downtown LA.

Shivers, 63, of Prague, Okla., said a good zoo is as educational as it is entertaining, reeling off several fun facts: Baseballs have wool in their cores; doctors use the intestinal lining from some animals to graft serious burns; female goats have beards like males; and while sheep prefer grass to weeds, goats want it the other way around.

Sheep and goats are popular because they have only bottom teeth and are safer around children. “Ponies and donkeys have teeth on the top and bottom and are more likely to nip fingers,” Shivers said.

Even so, pony rides often are coupled with petting zoos, and can be found during the holidays at many pumpkin patches and Christmas sales lots.

Rental fees range from $200 to $325 per hour, depending on the number of animals and the particular business.