When two cheetah cubs were born at the Zoo’s 3,200-acre research facility in Front Royal in December 2010, it was a huge triumph. Of course, at a zoo, most births are a triumph of some sort, but these two cheetah cubs were special.
The last time a cheetah gave birth at the National Zoo, it was at the Rock Creek campus in 2005. These were encouraging successes, especially for cheetahs.
Cheetahs are a species of concern for conservationists for a number of reasons. Due to human conflict, poaching, habitat and prey-base loss, there are only an estimated 7,500 to 10,000 cheetahs left in the wild. The International Union for Conservation of Nature considers cheetahs vulnerable to extinction.
The North American Species Survival Plan (SSP) population manages about 250 cheetahs. Historically, less than 18 percent of all cheetahs in the SSP have ever reproduced. Consequentially, the population has never been self-sustaining and zoos have traditionally had to bolster cheetah numbers with continued imports from southern African nations. Importing cheetahs is becoming increasingly more difficult. Now the SSP, with support from the AZA and its Sustainability Task Force, is focusing on generating a self-sustaining North American cheetah population for the first time ever.
In addition to threats to their survival in the wild, cheetah survival is threatened by their own DNA. More specifically, they lack genetic diversity. About 10,000 to 12,000 years ago—scientists are still unraveling the clues—the cheetah population dropped dramatically, perhaps around the same time as an ice age. Some scientists think the population may have been reduced to only one surviving, pregnant cheetah. Their highest estimates are that there were ten surviving cheetahs. Such a small population inevitably led to inbreeding. As a result, modern cheetahs have comparatively low genetic diversity. This lack of diversity makes cheetahs extremely vulnerable to disease and may contribute to high infant mortality and low sperm counts. It also means that the SSP must be extremely careful to manage this species through strict breeding and transfer recommendations.
Low genetic diversity also makes the captive cheetah population that much more important: it provides a "safety net" in case of a disease epidemic or other wide-spread catastrophe in the wild population.
Unfortunately, cheetahs have been historically difficult to breed in captivity. There are records of cheetahs in captivity, kept as hunting cats by kings and emperors, as far back as 3,000 BC. In all that long time, though, there is only one documented case of a cheetah giving birth in captivity, in India in the 1600s.
Cheetahs were kept in zoos beginning in 1829 at the London Zoo, but there were no cheetah cubs born in captivity until 1956 at the Philadelphia Zoo. Today, scientists are learning more about cheetah behavior and reproductive biology in an attempt to increase the number of cub births.
Scientists base housing and management decisions on what they have learned about the species’ natural history. For example, as with many cats, females live alone in the wild unless they have cubs with them. However, males may either live singly or may live in groups called coalitions, usually consisting of their brothers. Captive managers mimic this in captivity by housing females alone for breeding purposes, and leaving brothers together in groups whenever possible. Adjusting cheetahs’ surroundings, such as keeping them far from other large felids (including lions) helps reduce stress in this species.
Researchers are still learning about mate choice in this species. They have learned that keeping the males and females separated so they can neither see nor smell each other except during active breeding introductions helps improve reproductive success. The stimulation of novel scents (chemical cues in feces and urine that stimulate mate selection) as well as the excitement of being introduced to new potential mates can increase sexual behaviors and stimulate estrus or heat.
The cheetah is a much-beloved public exhibit animal and ambassador for conservation. However, the cheetah birth rate has been low, mainly because they seem to have cubs most successfully when they are managed in larger numbers in spacious off-exhibit enclosures called breeding centers, but are only a handful of facilities capable of providing this kind of environment. In fact, almost 95 percent of all cheetah cubs produced in the SSP have been produced in breeding centers. In 2007, SCBI made a commitment to improved understanding of cheetah biology and reproduction, and built a nine-acre Cheetah Science Facility at the Front Royal campus.
Five centers, including SCBI Front Royal, make up the Conservation Centers for Species Survival (C2S2), a group that collectively manages more than 25,000 acres of land devoted to the survival of threatened species with special needs (especially those that demand large enclosures, natural group sizes and minimal public disturbance). Each of the five centers has a cheetah breeding facility, where they conduct cheetah research and pursue long-term goals of building a sustainable captive cheetah population. Collectively, these five centers manage more than 40 percent of the SSP population. Happily, each C2S2 institution has been pleased to welcome cheetah litters this year.
The space and the labs that SCBI Front Royal provides have allowed our scientists to make huge strides in cheetah reproduction. SCBI scientists including JoGayle Howard and Adrienne Crosier have pioneered assistive reproduction techniques in cheetahs, including artificial insemination.
Non-invasive hormone monitoring enables researchers to monitor female estrous cycles and match hormonal trends with specific behaviors. All of the cheetahs at SCBI contribute to a better understanding of reproductive behavior. Evaluation of hormones in both males and females helped managers to successfully reproduce the two females this year at SCBI.
The cubs were born to two separate females. Five year-old Amani gave birth on December 6 to one cub—her first cub ever, in fact. Nine-year-old Zazi, a veteran cheetah mother, gave birth to another single cub on December 16. Cheetahs that give birth to a litter of only one cub, called a singleton, generally cannot produce enough milk to keep the cub alive. Typically in the wild, a singleton cub will die, after which the mother will go back into estrus and breed again theoretically with the goal of producing a larger litter.
Faced with two singleton cubs and a ticking clock, scientists and keepers at SCBI had to get creative. The cub born to Amani, a first-time mother, was hand-raised for 13 days, as everyone breathlessly awaited the birth of Zazi’s cubs. After Zazi also gave birth to a singleton, Amani’s cub was placed in Zazi’s den, creating a little of two that will help stimulate milk production.
“When we realized that Amani had a singleton, we removed the cub to hand rear it,” explains Adrienne Crosier, SCBI cheetah biologist. “So when Zazi gave birth, we decided it was the perfect opportunity to give both cubs a chance at survival as one litter under her care without any addition interference by us. Only a few institutions in North America have ever successfully cross-fostered cheetah cubs, and this is a first for SCBI. These births are a huge accomplishment and represent enormous efforts by the SCBI animal management, research, nutrition, and veterinary staffs”
The cubs' fathers arrived at SCBI Front Royal in April 2010. The Association of Zoos and Aquariums’ Species Survival Plan, which pairs cheetahs across the country in order to maintain genetic diversity in the population, will likely consider the two genetically valuable, Crosier said. Eventually, they will likely receive breeding recommendations of their own. It is up to the SSP to decide if they will stay here at SCBI long-term or possibly be transferred to one of the other six breeding facilities in North America.
“We are proud to help find a solution to maintaining a sustainable captive cheetah population,” said Steve Monfort, director of SCBI. “This is only our first year of having breeding pairs at SCBI, so it’s especially exciting that we have produced two cubs. The more that we understand about our cheetahs, the more we can do for those in human care throughout North America and for those in the wild.”