Early pregnancies prepare a cheetah for a life of productive motherhood, new research shows. A study published on 20 September in Conservation Letters advises captive breeding programs to focus on breeding female cheetahs at young ages to set the stage for many litters throughout their lives.
The world’s fastest animal, the cheetah has not outpaced a disheartening march toward extinction. Populations have declined from an estimated 100,000 a century ago to about 13,000 today. For years, researchers have pointed to the high genetic similarities among individual cheetahs as the main reason why captive cheetahs don’t often get pregnant.
“But if it was truly genetic, then wild cheetahs should have the same problem,” the study’s lead author, Bettina Wachter of the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany, told mongabay.com.
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Instead, the team’s field research showed that free-ranging cheetahs have many healthy litters if they breed starting at age three—much younger than typical first-litter ages in captivity.
Wachter and her colleagues captured 18 free-ranging female cheetahs in the open farmlands of Namibia and fitted them with GPS collars for tracking. After immobilizing the animals, researchers examined their reproductive organs with ultra-sonography—the same technique used to view human fetuses. By repeating the process with 15 captive female cheetahs, the scientists compared the reproductive health of both groups.
All of the wild cheetahs were in estrous, pregnant, or lactating: signs of active, healthy reproductive systems. About 40% of the captive adult females had active cycles. In the rest of the females, the team concluded that oestrogens—the hormones that control cycling—were impairing or “wearing out” the reproductive organs. Pregnancy and lactation give the organs a rest and promote fertility.
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Most of the wild cubs in the team’s study survived, suggesting that genetic defects are not as serious as other scientists have feared, Wachter said. Rather, lions and hyenas probably kill most cubs in other parts of Africa, such as the Serengeti. Those predators are absent from the team’s study site in Namibia.
The team also tested whether the stress of being fenced in makes captive cheetahs breed poorly, a factor proposed by other scientists. Wachter’s group measured the sizes of their cheetahs’ adrenal glands, which release adrenaline and grow larger when an animal feels chronic stress. The researchers found no difference in the glands of the captive and free-ranging cheetahs.
The combined results point toward early reproduction as the key to keeping cheetahs fertile, regardless of where they live, Wachter said.
“In the wild, cheetahs have their first litter at about three years, while captive cheetahs often are not bred until they are six, seven or eight,” she said. “If these animals are intended to be breeders reintroduced to the wild, this will have to change.”
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The results could inform captive breeding programs in the United States and elsewhere as they seek to boost cheetah numbers. Ironically, breeding captive cheetahs in Namibia is illegal for political reasons.
A forthcoming independent study also found that a cheetah’s reproductive system wears out more quickly if the animal has never been pregnant, said wildlife biologist Adrienne Crosier of the Cheetah Science Facility at the National Zoological Park in Front Royal, Virginia.
“I completely agree that the reason we often fail to reproduce cheetahs in captivity is that we wait too long with the females,” Crosier told mongabay.com.
CITATION: Bettina Wachter, Susanne Thalwitzer, Heribert Hofner, Johann Lonzer, Thomas B. Hildebrandt and Robert Hermes. Reproductive history and absence of predators are important determinants of reproductive fitness: the cheetah controversy revisited. Conservation Letters published online 20 September 2010. doi: 10.1111/j.1755-263X.2010.00142.x
Danielle Venton is a graduate student in the Science Communication Program at the Science Communication Program at the University of California, Santa Cruz.
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