May 17, 2013 at 4:41 PM ET
Is it a case of anteater virgin birth, a hormonal quirk or just some desperate hanky-panky? Whatever it is, Armani the anteater's surprising pregnancy has sparked a debate over what animals are capable of when it comes to sex.
The story unfolded at the LEO Zoological Conservation Center in Greenwich, Conn.: Last month, Armani gave birth to a cute baby pup named Archie. The only problem was, Archie wasn't supposed to exist.
Armani already had given birth last August to a female pup named Alice, fathered by a male anteater at the center named Alf. Anteater dads have been known to kill off their progeny, so Alf was put in a separate pen for several months. Marcella Leone, the nonprofit center's founder and director, said Armani and Alf shouldn't have had the opportunity to conceive little Archie.
"It is our protocol that that should not happen, so it's a mystery," Leone told NBC News.
Leone speculated that the "virgin birth" may have been a bizarre case of delayed implantation, also known as embryonic diapause. Some species are able to hold up hormonally on having their fertilized eggs attach to the uterine wall and start developing, apparently as a stress response. That's known to happen to armadillos, which are in the same scientific superorder (Xenarthra) as anteaters. "It's been presumed that giant anteaters can do this as well," Leone said.
Could that be what happened to Armani?
"Given the paucity of literature, it wouldn't surprise me," said Bruce Murphy, director of the University of Montreal's Reseau Quebecois en Reproduction (Quebec Reproduction Network).
Diapause or desire?
Murphy is no expert on anteaters, but he is an expert on diapause. A paper on the subject that he and his colleagues published in the journal Open Biology is featured this week as an "editor's choice" in the journal Science.
A cross-species study published by a different set of researchers in PLOS ONE suggests that Armani may well have been capable of adjusting the dials on the standard six-month gestation period. "Their conclusion, and I think it's a good one, is that maybe every species has a capacity for diapause, if uterine conditions are appropriate," Murphy told NBC News.
However, it may not be necessary to turn to diapause, or to a different kind of "virgin birth" known as parthenogenesis, for an explanation. Despite the best efforts of the conservation center's staff, it's conceivable that Armani and Alf found a way to couple through the enclosure's high-tensile fence. They may have even indulged in a brief encounter while they were being moved around.
Just minutes to do the deed
"I have seen anteaters breed many times, but that doesn’t mean I know exactly what is going on in amongst all that hair," Marie Magnuson, a biologist at Washington's Smithsonian National Zoo, told NBC News in an email. "There is some thought that there is no actual penetration, just a lot of rubbing up together. If that is the case, then his sperm are doing all the heavy lifting on the job, and a fence would not be an insurmountable barrier — as long as it is chain-link and not solid."
It wouldn't take long for anteaters to do the deed, Magnuson said.
"If they were together, it was long enough," she said. "When doing a re-introduction between our breeding pair, we had planned on taking it slow and safe. We were going to put them together for five minutes and then separate them. At three minutes they were copulating."
Leone doesn't totally exclude the possibility that Armani and Alf had a furtive fling. "You can imagine what any man will do to get to his woman," she joked. "This is not our plan, but nature is a very strong force."
The way she sees it, the story is about much more than a couple of amorous anteaters.
"The thing to really focus on is that a plant or animal becomes extinct every 20 minutes," Leone said. "So the point is to learn as much as we can about giant anteaters out of the wild, so that we can apply that knowledge in the wild as well. Ultimately, the most important thing is to save those wild places for wildlife."
More about animal sex:
Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with NBCNews.com's stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.