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Rhinoceros Breeding Update
For a rhinoceros mom, it’s normal to have a fetus growing inside her for 15 months. It can take even longer for a rhino to get pregnant. Dana Nicholson, pachyderm area supervisor at the Milwaukee County Zoo, can attest to that. He and his staff have been trying to create the right conditions for pregnancy for a few years. The Zoo has two aging rhinos: Mimi, 24, and Brewster, 26. “They’re both healthy,” says Nicholson. And since they both came to the U.S. from the wild in Zimbabwe, their genes are invaluable to creating a genetically diverse population of rhinos in zoos. That’s important because the black rhino is an endangered species. “Brewster and Mimi are ranked fourth most important genetically in the 24 founder (original) animals in U.S. and Australian zoos. So we’re making a concerted effort to make something happen.” That includes tracking Mimi’s estrus cycles – and Brewster’s reaction to them. “When the male gets frisky and very amorous, then we put them together – for a limited time. We had to literally watch them every moment when we first introduced them a few years ago. Their courtship sometimes can be violent. Now they’re more compatible,” says Nicholson.
Rhinos are large, to say the least; Brewster weighs 2,600 pounds, and Mimi weighs 2,300.“When they breed, you hear it. The mounting lasts 30 to 40 minutes.” Mimi’s estrus cycles were more regular in 2010, compared to 2009. “We had three breedings last summer, the last on July 9. We have to wait three to four months after the last breeding to check fecal samples because the progesterone can’t be measured till then.” The level of progesterone (a hormone) indicates whether Mimi’s pregnant. By late November the tests revealed that Mimi indeed was not pregnant. So they’ll have to wait till April to try again, says Nicholson. Courtship can include “cat and mouse running” in the yard, and there’s not enough space for the rhinos to breed indoors. It has to be above 45 degrees and dry for these African mammals to go outside. If Mimi gets pregnant in April, she won’t deliver till summer 2012. In the wild, the calves have to stand soon after birth, says Nicholson, adding, wryly, “So they have to cook a long time.”
Arrived: July 10, 2010
Small Mammals Building
Janeiro isn’t like most other male tayras. “He’s very people-friendly,” says Rhonda Crenshaw, area supervisor of the Small Mammals Building at the Milwaukee County Zoo. “Our males have always been very leery of people in general, but he loves to come and see what we’re doing.” The 1-year-old tayra from the Papiliorama Swiss Tropical Gardens in Kerzers, Switzerland, can’t quite contain his elation here at the Zoo. Perhaps it’s the generous portions of raw meat, vegetables, fruits and especially bananas he receives or maybe even his blossoming friendship with the Zoo’s female tayra, Andrea. The two have progressed from avoiding each other altogether to relaxing near each other on branches and in a plastic box suspended from the ceiling.“It’s their favorite spot,” Crenshaw says. “It’s the highest point in the exhibit where they can lay down and rest.” To introduce the two weasel-like mammals, zookeepers brought them to the Animal Health Center, where they had more space and could be separated quickly if they had a conflict. So far both Janeiro and Andrea, 6, are as compatible and lively as tayras ought to be. “They’re very active,” Crenshaw says. “They love to climb and jump. They use the entire exhibit.” Tayras are known for their agility as well as their numerous vocalizations. They squeal when frightened, scream when fighting and huff when nervous. The diurnal critters live in the forests of southern Mexico, Central America, South America and Trinidad. While their population remains stable, they are dwindling in Mexico due to deforestation and farming. To tell the difference between them, look for Janeiro’s dark, thick fur against Andrea’s lighter-colored head. Janeiro is also slightly bigger, weighing about 13 pounds, while Andrea is just over 8 pounds. When the new mating season for tayras starts in spring, zookeepers hope to see the two breed.