January 10, 2020 – What happens when a species is rescued from the brink of extinction? A Morris Animal Foundation-funded study currently underway at the San Diego Zoo Institute for Conservation Research is trying to answer that question with the help of a tiny mouse.
The subject of the San Diego Zoo study is the Pacific pocket mouse, a highly endangered species found in California. Saving a species from extinction is a big win for conservationists, but scientists also know there are problems unique to very small populations of animals, including limited genetic diversity. The pocket mouse could hold a key to managing similar situations in other endangered animals.
The story of the Pacific pocket mouse began 20 years ago when three small but distinct populations of mice were discovered in Southern California. The mouse was thought to have become extinct in the 1980s, so conservationists mobilized to save the few individuals re-discovered in the wild.
Unfortunately, despite efforts to protect them, mouse populations continued to decline. In 2012, the San Diego Zoo started a breeding program using individuals from all three populations. Their goal was to raise mice in captivity that would eventually be released back into the wild. The program resulted in a slow but steady increase in mouse numbers. And since the mice had different genetic backgrounds, genetic diversity also increased – a benefit.
However, caretakers also noted that the mice from one of the founding populations weren’t doing as well as the others. They hypothesized that harmful mutations affecting fertility were prevalent in the mice. Because of the limited numbers of mice in the population, the harmful mutations persisted.
“Harmful mutations can kick around a population and not cause problems if the population is large enough,” said Dr. Aryn Wilder, a conservation geneticist and the principal investigator of the study. “However, in small populations natural selection doesn’t operate well. Harmful mutations persist and accumulate and can come together in detrimental ways. This collection of harmful mutations is known as genetic load.”
For Dr. Wilder and her team, the Pacific pocket mouse presents an ideal opportunity to learn more about species recovery and the best ways to eliminate undesirable gene variants while increasing genetic diversity.
“We want to not only learn more about how to breed these mice successfully but also to learn to better manage genetic variation in other endangered species when captive breeding or genetic rescue are necessary for preventing extinction,” said Dr. Wilder.
Morris Animal Foundation has been a supporter of wildlife research for over 50 years. Our funding has aided the recovery of several endangered species, from coral species to Przewalski’s horse. We recognize that saving a species requires dedicated funding to improving the health of fragile populations.
Learn more about our wildlife grants and what you can do to help species like the Pacific pocket mouse not only survive but thrive!