It's anybody's guess just how many Black-Tailed Prairie Dogs there are at the Jerusalem Biblical Zoo these days. At present, the keepers believe there are 21 - but the expectation is that more of these curious creatures may pop out of the ground any day. The prairie dog exhibit, unique in Israel, is housed at the newly opened Underworld display. Black-Tailed Prairie dogs are not in fact dogs, but rodents from the squirrel family. The prairie dogs grow to be about 35 cm. long and each has a black tip on the end of its short tail. But it is the warning cry of these cautious animals that gave them a canine moniker - if they spot danger approaching they bark to each other before disappearing into the ground. Prairie dogs live together in large colonies with thousands of members and make their homes in underground burrows, of which they dig two kinds. The first are long deep burrows where they live and breed. In addition, the rodents dig shorter burrows near the surface into which they can quickly escape when danger threatens. Black-Tailed Prairie dogs come from North America, where hundreds of millions of these rodents once roamed the plains. However, development in their natural habitat and their culling by farmers as a pest has caused a sharp decline in numbers over the past 50 years. Just a few years ago, the prairie dogs were candidates for the Endangered Species List, until a recent assessment showed a recovery in the population. With the annual breeding season finished, the prairie dogs are drawing to the end of their typical six-week gestation. Each female can give birth to as many as eight cubs. After birth, the tiny, blind cubs stay underground for another month and grow from a mere 50 gr. to 150 gr. in weight. During this time their eyes open and, once big enough, they are ready for their first public appearance and exit the burrow. Since keepers have no access to the subterranean tunnels, they have no idea just how many newborn cubs there are until they surface. The zoo had four females and six males just a few weeks ago, but that number is changing fast. So far, 11 cubs have appeared, but Underworld keeper Haim Cohen-Hagadol suspects they may be the offspring of just two of the adult females. If so, the coming weeks may see more prairie dogs surfacing. With only a limited space available for the family, Cohen-Hagadol says he will try to find good homes for the youngsters at other zoos. "The problem is catching them," Cohen-Hagadol says, and he isn't joking. Prairie dogs are nervous animals that live in constant fear of predators, in particular birds of prey. These ever-watchful rodents keep a keen eye out for danger and at the first hint of an approaching keeper, they dive down their burrows. However, Cohen-Hagadol hopes that the young generation growing in captivity may be less cautious, and can be trained to accept the keepers' presence by bribing the rodents with treats. This will allow keepers to monitor the animals at close range, as well as administer medical treatment when necessary. In the meantime, all that can be done is a daily count to see just how many prairie dogs are scampering about the exhibit, or sitting up on their haunches as they watch their human visitors behind the observation windows.