Endangered giraffes may be inbreeding themselves to death, study says

When it comes to love, a group of giraffes is keeping it in the family. It may be killing them.

Biologists discovered alarmingly high levels of inbreeding among Masai giraffes, an endangered subspecies native to Kenya and Tanzania, according to a study published June 12 in the journal Ecology and Evolution.

Distinguished by their darker coat, Masai giraffes tower over other giraffe subspecies and are the tallest land mammals roaming the Earth, according to Zoo New England.

Their population is rapidly declining because of human activities like habitat destruction and poaching. Over the past 30 years, its numbers have been halved, leaving only about 35,000 individuals remaining today.

Those that remain are divided into two groups, living on either side of the Gregory Rift escarpments, a series of “formidable” cliffs that slice through East Africa.

Researchers at Pennsylvania State University set out to determine whether the cliffs act as a natural barrier that hinders interbreeding between the two populations.

“Interbreeding among different populations results in the exchange of genetic information—often called gene flow—and is generally considered to be beneficial because it can improve overall genetic diversity and help buffer small populations against disease and other threats,” Lan Wu-Cavener, one of the study’s authors, said in a university news release.

To study the gene flow, researchers analyzed the genomes of 100 giraffes in the two groups.

They identified several haplotypes, which are clusters of genes usually inherited together, and compared them across the two populations. They found no shared haplotypes between the two groups, indicating the giraffes had not crossed the cliffs to interbreed in about 250,000 years.

Researchers concluded that the two Masai populations were founded independently and genetically distinct, suggesting the animals are even more imperiled than previously believed.

“Masai giraffe are more at risk for going extinct than what we thought,” Douglas Cavener, one of the study’s authors, told McClatchy News. “Given that Masai giraffe have already been declared an endangered species this should set off the alarm bells for their conservation.”

The researchers also discovered that the Masai giraffes engage in high rates of inbreeding, which could pose a threat to long-term viability for the already diminished subspecies.

Their inbreeding could be caused by population bottlenecking and fragmentation. It may also be the result of a rinderpest plague that triggered “mass mortality events” among giraffes in the 20th century.

But whatever the cause, the giraffes’ continued inbreeding could eventually lead to an “inbreeding depression,” which is characterized by poor survivability and fertility in related animals.

“However, they have not reached a point of no return and there is no evidence of inbreeding depression,” Cavener said. “If the Kenyan and Tanzanian governments act quickly they can save this species from extinction.”

This story was originally published June 15, 2023 at 6:37 PM with the headline "Endangered giraffes may be inbreeding themselves to death, study says."