Birth control for lionesses

Press, 16 February 1984, Page 24

Birth control for lionesses

NZPA-ReuterEtosha Pan, Namibia Scientists at the Etosha National Park, a Southern African game reserve, have been giving contraceptives to lionesses in an experiment to correct an imbalance in the wildlife population.

Mr Hu Berry, chief biologist at the park, said he noticed the Etosha lions were multiplying in excessive numbers, but there was a sharp drop in the numbers of wildebeest, a member of the antelope family which used to roam the area. The scientists found a variety of factors which were giving the park’s predators an advantage in the struggle for survival.

Mr Berry tried to correct the problem by putting lionesses of cub-bearing age on contraceptives. He implanted scm rubber capsules in their neck muscles to release a constant flow of birth control hormones into their systems.

The decision to experiment with contraceptives followed up a detailed study to find out what was causing the unusual situation at Etosha.

The Etosha Game Park, one of the biggest game reserves in the world, is about the same size as Massachusetts or Wales. At its centre is the Etosha salt pan, the vestige of a prehistoric salt lake which dried

up centuries ago. The pan, 129 km across at its widest point, is a completely flat expanse of whitish, salty clay which becomes wet during the rainy season at the beginning of the year. Mr Berry said there were too many lions at Etosha because the delicate preda-tor-prey balance had been significantly upset by man’s intervention. His team of scientists identified three main causes.

Etosha is totally fenced, which precludes the age-old seasonal migrations of the hoofed animals for water. Second, numerous boreholes have been drilled to provide a permanent source of

water for the animals which cannot follow the rains. In addition, a tourist road has been built through the reserve and in this case, Mr Berry said, the backlash of disturbed Nature took a subtle and unexpected but deadly form. The numerous gravel pits used to build the road have proved an ideal alkaline breeding area for anthrax, a disease which can decimate hoofed stock but to which the lion is immune.

Before fencing, the lion prides had to join the annual migrations of the wildebeest and many of the cubs died in the long, arduous treks. Nowadays, they have only to stake out the man-made waterholes to

feed. There are also the carcases of anthrax casualties to feast on. About 75 per cent of lions in a natural environment will die before they reach breeding age. At present, Mr Berry’s team is studying a group of about 55 lions from the park’s estimated 500. Ten lionesses have had implants and their behaviour is being compared with 15 lionesses in the group who are continuing to bear cubs. The aim is to study how the hormone changed the social behaviour of the lions, Mr Berry said. They were observed day and night and their activities recorded. The hormone stimulates post-pregnancy lactation in the animals, preventing conception. So far, the lionesses given the drug are notably healthier than those not. Female lions live about 10 to 12 years while males usually live a little longer. Life is more perilous for females who do most of the hunting and are more likely to break a leg or have a jaw broken by a zebra. They are fertile from about three to 10 years of age. Mr Berry said another major advantage of the contraceptive approach was that it did not destroy genetic material and was reversible.

The experiment is 18 months old. Mr Berry said it would be another few years before he could publish his conclusions as to the suitability of contraceptives in wildlife management.