The California Falcon for the first time reproduces without a male

Researchers were surprised to discover that parthenogenesis in the critically endangered California falcon.

For decades, scientists have been trying to save the California osprey from the brink of extinction. The entire population of this bird dropped to 22 in 1982. In 2019, efforts to breed in captivity and release into the wild helped the number of California falcons slowly increase to more than 500. The above process requires careful management of captive birds, carefully selecting mating males and females to produce healthy chicks.

The California Falcon at the San Diego Zoo Wildlife Alliance facility. (Photo: San Diego Zoo Wildlife Alliance)

Taking a closer look at the genetic data, researcher Oliver Ryder and his collaborator Leona Chemnick found that two male birds with numbers SB260 and SB517 had no genetic elements in common with the birds believed to be their fathers. In other words, they are born through "virginity" , according to the study published in the journal Heredity on October 28. Such asexual reproduction usually occurs in sexually reproducing species when some cells act like sperm and fuse with the egg of the female individual.

Although rare in vertebrates, parturition has been reported in sharks, rays and lizards. The scientists also observed self-fertilization in some captive birds such as turkeys, domestic chickens and blue-breasted quail, when females were raised in a male-free environment. But this is the first time researchers have seen virginity in the California osprey. According to Ryder, it is particularly odd that SB260 and SB517 have different mothers. Their mother is raised with the male. Both mother birds successfully reproduced with the male before and after.

Only about 300 critically endangered falcons live in California, Arizona, and Utah. In such low numbers, it is possible that falcons use their virginity as a survival tool, says Reshma Ramachandran, a reproductive physiologist and microbiologist at the University of Mississippi. There is evidence in other species that parthenogenesis is a "lifesaver" for endangered animals . For example, the critically endangered small toothed swordfish turns to virgins as it becomes increasingly difficult to find mates in the wild.

However, the above hypothesis may not be true for the California falcon. First, captive female birds can meet mates. Second, none of the offspring born through parturition survived to maturity. SB260 died after less than two years while SB517 died before the age of 8. Some California falcons can live to be 60 years old. Because scientists test the risk of genetic disorders very carefully when breeding falcons in captivity, it is possible that the young birds carry a genetic mutation that causes them to die prematurely.

Earlier this year, Robinson, Ryder, and colleagues published research detailing the entire genome of the California falcon. In the future, that valuable genetic data could help us better understand how parthenogenesis occurs in this animal. According to Ramachandran, although parturition has been observed mainly in captive animals, there is no reason to conclude that the phenomenon does not occur in the wild.