Who’s Your Daddy?
Archie the giant anteater may have a hard time answering that question. Born to mom Armani at the LEO Zoological Center in Greenwich, Connecticut, Archie seems perfectly normal except for one small detail: Zookeepers have no idea how he came into being.
Armani had previously given birth to a baby named Alice after a romantic rendezvous with Alf, a male anteater also at LEO. But this wasn’t an episode of Leave it to Beaver. Male anteaters are known to kill and eat their offspring, so the zoo’s staff kept Alf separate from Armani and Alice for several months. Before the anteater family was reunited, however, Armani somehow got pregnant with Archie, according to the Connecticut newspaper Greenwich Time. (Related post: “Weird Animal Courtship and Mating Rituals.”)
This pregnancy mystery immediately triggered thoughts of virgin birth, a.k.a. parthenogenesis. Animals conceived via parthenogenesis don’t actually have a father. Instead, the embryo grows and develops in the absence of fertilization. It sounds unusual—some might even say miraculous—but it’s a surprisingly common occurrence in the animal kingdom. Researchers believe that an absence of available males likely drives the phenomenon.
Although a variety of different animals have been found to reproduce via parthenogenesis, it is most common in invertebrates (such as water fleas, parasitic wasps, and bees) and certain types of vertebrates (fish, amphibians, and occasionally birds). Although the exact mechanisms of parthenogenetic reproduction can vary from species to species, all parthenogenesis produces normal, healthy offspring.
Check out the wide range of species below that have produced children without a father.
In the mid-2000s, two Komodo dragons at the London Zoo laid viable eggs via parthenogenesis. Neither female had encountered a male during captivity, and subsequent genetic tests revealed no paternal contribution of DNA. (Also see “Virgin Birth Expected at Christmas—By Komodo Dragon.”)
New Mexico Whiptail
As its name suggests, this lizard lives throughout the desert southwest. It appears to have originated as a hybrid between two other closely related species: the little striped whiptail and the tiger whiptail. Although hybridization between these two whiptails can still produce viable New Mexico whiptails, all of the resulting offspring are female. Thus, the New Mexico whiptail reproduces solely via parthenogenesis.
Parthenogenesis might seem like an especially good reproductive choice when no males are handy, but female copperhead snakes use parthenogenesis even when there are plenty of males nearby. A 2012 study in Biology Letters showed that 1 of 22 captured pregnant copperheads gave birth parthenogenetically—much higher than the researchers expected. Most of the observed cases of parthenogenesis have occurred in captive animals, leading researchers to wonder exactly what drives the process in the wild. (Related: “‘Virgin Birth’ Seen in Wild Snakes, Even When Males Are Available.”)
In 2001, a hammerhead shark gave birth at an Omaha zoo—hardly newsworthy. She didn’t have a mate in captivity, but zookeepers figured the shark had stored sperm after copulating in the wild, which is a quite common occurrence. The baby shark was killed shortly after birth by a stingray. Genetic analysis revealed that the little shark had no paternal DNA—only maternal genetic information. (Related: “‘Virgin Birth’ Record Broken by Hotel Shark.”)
Archie’s Mystery Solved?
Zookeepers at LEO believe that Archie was likely the result of embryonic diapause. Not virgin birth in the strict sense of the phrase, embryonic diapause happens when a mother puts a fertilized egg on hold in her uterus.
If environmental conditions aren’t right, the mother can prevent the fertilized egg from implanting and developing for a long period of time. Although the process has never been previously observed in an anteater, researchers have documented it in armadillos, which are closely related to anteaters. (Watch an anteater video.)
If Armani did undergo embryonic diapause, she’s in good company. A paper published last year in PLoS ONE showed that a wide variety of mammals have the potential to use embryonic diapause. Thus while it might look like Armani didn’t need a male to conceive Archie, she actually did. It’s just that zookeepers didn’t catch them in the act.
So the next time “Millionaire Matchmaker” or “The Bachelor” comes on TV, just imagine what kind of programming we could have if animals created shows based on their own reproductive strategies. “No Males Allowed,” anybody?