Precious Samples Provide Insight into Black-Footed Cat Genetics
My eyes widened as I listened to San Diego Zoo Global veterinarian Dr. Nadine Lamberski describe the process of catching black-footed cats for biological sampling.
Each night, the team drives a stretch of dirt road for hours through a South African savannah, taking turns standing in the back of the truck training a spotlight on the route until they see the characteristic eyeshine of Africa’s smallest feline. Black-footed cat sightings are exciting, but captures are no easy task. The cats are smaller than a house cat and lightning quick. They can be surprisingly ferocious for their size, and one has even been observed to hold its ground and swat at a jackal four times its size. They can easily disappear into the surrounding grass, so when a black-footed cat is caught, the resulting biological samples are precious.
The black-footed cat Felis nigripes is a small, solitary animal whose populations in Southern Africa are in decline. It is threatened with habitat degradation, persecution by farmers, and loss of prey species through pest control. Such threats have caused the species to be listed as the most vulnerable Sub-Saharan cat by the Cat Specialist Group of IUCN and declared endangered by the U.S. Fish and Wildlife Service.
Concern for black-footed cat conservation motivated Dr. Lamberski to join a long-term study on the behavior, ecology, and disease of wild black-footed cats in South Africa. The Genetics Division at the Zoo’s Institute for Conservation Research collaborates with Dr. Lamberski to study and preserve the precious samples collected in the field, frozen in liquid nitrogen, and safeguarded during the trip from South Africa to San Diego. To date we have cell cultures, blood, and tissue samples from a remarkable 29 wild black-footed cats in the Frozen Zoo®.
In 2009, Summer Fellow Daniel Acosta and I began analyzing black-footed cat samples to assess the genetic health of the species in the wild. This was the first genetic study in black-footed cats, designed to provide a baseline of genetic variation for the species. Data from wild populations would inform the management of the captive population of black-footed cats in North American zoos. We also began to augment our collection of captive black-footed cat samples, and since 2009 we have nearly doubled the number of individuals represented from 17 to 32.
The results of our genetic studies indicate that the wild population contains healthy levels of genetic diversity, comparable to levels in wild populations of large cats such as jaguars and leopards, or small cats like African wild cats and ocelots. Genetic diversity is slightly lower in the captive population, though still at a healthy level. Our data indicate that there is little inbreeding in the wild and captive populations, and this has been independently confirmed for the captive population based on the pedigree. We found some evidence of a population bottleneck in both populations, but further sampling is needed to determine if this trend is significant.
Analysis of mitochondrial DNA yielded two genetic variants of black-footed cats that differ by 0.5%, consistent with the amount of variation typically seen within species. Notably, the second variant has so far been found only in the wild population from Benfontein Farm near Kimberley, suggesting that this may be a unique and important population.
As our collection of samples grows, so will our ability to ascertain the genetic health of black-footed cat populations. Meanwhile, as I open the refrigerator and easily pluck the tube of black-footed cat DNA from its well-lit shelf, I take a moment to appreciate everything that went into collecting that precious sample and think, “Gotcha!”
Heidi A. Davis, Research Coordinator, Genetics, San Diego Zoo Institute for Conservation Research
Photos courtesy of Dr. Alexander Sliwa, Cologne Zoo.