Scientists working at the San Diego Zoo Wildlife alliance were in for a shock when two different female condors hatched chicks from eggs that had not been fertilized. After performing routine DNA testing on the chicks, the scientists were surprised to discover that the chicks had DNA only from their mothers and not from any males. This was the first time this kind of reproduction, called Parthenogenesis, was observed in a group of California condors where males and females were living together. The findings were reported in a study last week.
How typical is Parthenogenesis among animals?
According to National Geographic, Parthenogenesis takes place more often among small animals that lack a spine, like bees, ants, and other insects, although it can happen under certain circumstances in animals with spines, particularly lizards or fish. It is almost always a surprise when it happens among larger animals, as in the case of Leonie, a zebra shark whose unfertilized eggs hatched three healthy shark pups. In 2016, Leonie was kept only with other females in a tank at The Great Barrier Reef Marine Park in Australia.
"Parthenogenesis has been observed in more than 80 vertebrate species, about half of which are fish or lizards. It’s rare that complex vertebrates such as sharks, snakes, and large lizards rely on asexual reproduction, which is why Leonie and others initially stumped scientists." - National Geographic
Why did it happen?
Why did the condors lay unfertilized eggs that were able to hatch live chicks? National Geographic mentions that parthenogenesis might be a strategy for animals without mates to be able to reproduce. But in this case, the females had access to males. A co-author of the condor study, Cynthia Steiner, explains that such a situation does not apply here.
"Unlike other examples of avian parthenogenesis, these two occurrences are not explained by the absence of a suitable male.” - study co-author
But a possible explanation was not provided. In this case, some mysteries remain yet to be solved--nature has not yet given up all its secrets.
"San Diego Zoo Wildlife Alliance Conservation Scientists Report First Confirmed Hatchings of Two California Condor Chicks from Unfertilized Eggs". San Diego Zoo Wildlife Alliance. San Diego, CA. October 28, 2021.: https://sandiegozoowildlifealliance.org/pr/CondorParthenogenesis
"How some animals have ‘virgin births’: Parthenogenesis explained". National Geographic. Washington, DC. August 25, 2020.: https://www.nationalgeographic.com/animals/article/parthenogenesis-how-animals-have-virgin-births
Reef HQ Aquarium website.: https://www.reefhq.com.au/