Texan Panthers to the (Genetic) Rescue

Once upon a time, thousands of panthers roamed throughout the North American continent. Puma concolor are a highly adaptive species that inhabited a variety of habitat types. However, within 200 years after European colonization, they were eliminated from the entire eastern half of North America due to hunting and habitat loss. All that remained was a small sub-population in Florida. Even though this population has been protected from hunting since 1958, by the 1990s, there were only about 30 panthers left there, leaving conservationists in a panic.

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Florida Panther. Image Credit: Monica R. via Flickr.

How did the population shrink so drastically? When a small population remains isolated for a long time, individuals do not have the opportunity to mate with somebody who is not from their own family. When that happens repeatedly, inbreeding allows unfavourable traits that are generally masked to emerge and become common in the population. This phenomenon is called inbreeding depression.

The primary concern of conservationists is whether the traits affected by inbreeding relate to survival and reproduction. If they do, the population’s growth rate may slow down due to its small size. Florida panthers started exhibiting kinked tails and cowlicks on their throats, which was not seen in other populations of panthers.  Male Florida panthers also started exhibiting features such as poor sperm quality, low testosterone levels, and cryptorchidism (i.e. undescended testicles at adulthood). Furthermore, a host of parasites and infectious diseases started afflicting Florida panthers. Due to all of this, conservationists believed that the population would be eliminated in the next 20 years if nothing was done about it. So they took a bold step.

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The kinked tail of a Florida panther on the left, and an x-ray of a kinked tail on the right. Image Credit: Kerk, Onorato, and Oli.

A much larger population of this species exists in South Texas (where they are called mountain lions instead of panthers). In 1995, eight females from that population were brought to Florida and released at four different sites. Five of the Texas females successfully bred with male Florida panthers and created outbred kittens. Today the population has increased to 120 to 230 individuals (according to the U.S. Fish and Wildlife Service’s 2017 census). Pretty great results, right?

This process is known as genetic rescue. An important aspect of the rescue is the increase in genetic variation. A massively important tenet in conservation genetics is the concept that higher genetic variation in a population results in greater resiliency. If any pressures act on such a population, the genetic variation will help the population to survive because some individuals will be able to tolerate the change in conditions. The maintenance of genetic variation has helped the panthers in many ways, by eliminating many of the issues that had cropped up as a result of their small size and inbreeding depression. Fewer male cats are now showing poor sperm quality and undescended testicles. The cats can now inhabit places that were previously thought to be unsuitable, and they are less susceptible to disease as a population.

Genetic rescue is not the only reason these panthers have shown an increase in population size. Many conservation efforts have been implemented in the last two decades to prevent deaths by vehicles or getting shot by people who feel threatened by them. However, as the panthers demonstrate, simply removing human pressures like hunting is only the first step. Genetic rescue is a great way to give them some ammunition with which to start growing again. It is definitely not a final or a complete solution, but merely a starting point from where humans can start to remedy the harm they have caused.

 

About the Author

sonnySunishka “Suni” Thakur is an undergraduate at the University of Georgia majoring in Genetics, currently just trying to make the most of her freshman year. She loves to read, dance, work with student organizations like First Book and World Ambassadors, and gets very excited about science. More from Sunishka Thakur.