On a Texas barrier island, biologists have found an odd population of canines that carry genes from the critically endangered red wolf, including a unique genetic variation — or "ghost allele" — that isn't found in any known canine species of North America.
Pictured above, the canines in question live on Galveston Island, where they caught the attention of wildlife biologist Ron Wooten. After observing them for a while, Wooten emailed researchers at Princeton University to request genetic testing.
"I regularly receive this kind of inquiry, but something about Wooten's email stood out," says Bridgett vonHoldt, an assistant professor of ecology and evolutionary biology at Princeton, in a statement. "His enthusiasm and dedication struck me, along with some very intriguing photographs of the canines. They looked particularly interesting and I felt it was worth a second look."
That feeling was correct, as vonHoldt, Wooten and their colleagues report in a new special issue of the journal Genes. By taking a closer look at these canines, they've found genetic relics that may prove valuable in the quest to save this rare American wolf.
In the red
Only a few dozen red wolves currently exist in the wild, although more than 200 are maintained at captive-breeding facilities throughout the U.S. — like this one at Point Defiance Zoo and Aquarium in Tacoma, Washington. (Photo: John Froschauer/PDZA/USFWS)
Red wolves once roamed across the Southeastern U.S., but declined rapidly last century amid habitat alteration by humans and hybridization with coyotes. Despite joining the U.S. endangered species list in 1967, they were declared extinct in the wild in 1980, apparently only saved from full extinction by a captive-breeding program that had begun a few years earlier.
Scientists started "rewilding" captive-bred red wolves in the late '80s, establishing a new population at Alligator River National Wildlife Refuge in eastern North Carolina. This enclave grew to about 120 wolves by 2006, but has since fallen back to about 40, according to the U.S. Fish and Wildlife Service, largely due to gunshot wounds and vehicle collisions. Similar efforts have failed at other locations, including an experimental reintroduction program at Great Smoky Mountains National Park in the 1990s, although a tiny red wolf population seems to be surviving on Florida's St. Vincent Island (even after a major hurricane).
Once the researchers extracted and processed DNA from Wooten's samples, they compared it with each of the legally recognized wild canid species in North America — including 29 coyotes from Alabama, Louisiana, Oklahoma and Texas, along with 10 gray wolves from Yellowstone National Park, 10 eastern wolves from Ontario and 11 red wolves from the captive-breeding program. The Galveston Island canids, it turned out, were more similar to captive red wolves than to typical Southeastern coyotes.
"While there have been reports of 'red wolves' along the Gulf Coast, conventional science dismissed them as misidentified coyotes," says study co-author Elizabeth Heppenheimer, a graduate student in vonHoldt's lab at Princeton. "Now, we have shown that at least one example of a 'red wolf sighting' has some validity to it, as these Galveston Island animals definitely carry genes that are present in the captive red wolf population yet absent from coyotes and gray wolf populations."
And not only do the Texas canids share distinctive genes with today's red wolves, but they also carry a unique genetic variation that isn't found in any other North American canids. This may be left from a "ghost population" of red wolves whose variations didn't make it into the captive-breeding program gene pool, but were secretly preserved in these hybrid animals.
"This variation may represent the red wolf-derived genes that were lost as a result of captive breeding," Heppenheimer says. "It's incredibly rare to rediscover animals in a region where they were thought to be extinct, and it's even more exciting to show that a piece of an endangered genome has been preserved in the wild."
This highlights a common confusion about the word "species," Heppenheimer adds. Although it typically refers to a group of organisms that can breed with each other and produce viable offspring, that definition doesn't work for organisms that reproduce asexually, so biologists have had to develop a variety of ways to delineate species. Thus, even some creatures that are generally considered separate species can interbreed — like humans and neanderthals, for example, or coyotes and wolves.
A visual comparison of the Galveston Island (GI) canids, coyotes and red wolves. (Photos: [A] GI canids: R. Wooten. [B] western coyote: Rich Keen/DPRA/Wikimedia Commons; GI canid: R. Wooten; red wolf: R. Nordsven/USFWS. [C] western coyote: Michael Vamstad/NPS; GI canids: R. Wooten; red wolf: R. Nordsven/USFWS.)
"Coyotes and wolves are considered distinct species based on the 'ecological species' concept, which recognizes wildlife as different species if they use different resources within their environments," Heppenheimer says.
Interbreeding probably explains why the Galveston Island canids are "ambiguous-looking," she adds. Although the visual differences between coyotes and wolves tend to be subtle, there was just something about these animals that stood out. "It's hard to put my finger on exactly what about these animals made them look ambiguous, since we didn't take any quantitative measurements, but the snout shape and the overall size of the animals just didn't look quite right for them to be pure coyote."
In North Carolina, hybridization with local coyotes is seen as a threat to the wolves' endangered genetic legacy. But if a similar rewilding program could be launched near Galveston Island, these hybrid canids might actually be helpful.
"Texas may be an appropriate location for future reintroduction efforts," Heppenheimer says. "If hybridization does occur, the 'coyotes' in the area may carry red wolf genes, and these hybridization events could restore red wolf genes that were lost as a result of the captive breeding program."
More research will be needed before something like that happens, she adds, but given the way researchers often need to protect captive-bred animals from other wildlife, it is an intriguing idea for letting wild animals help us save a species we nearly wiped out.
The new study also highlights how much we still have to learn about North America's native canines. There is already some debate about the identity of red wolves, with previous genetic research raising questions about whether they should really be considered a separate species from gray wolves. And now, vonHoldt suggests, we may also want to take a closer look at some coyote populations, since they (and possibly other common wildlife) may contain valuable genetic secrets from rare or extinct species.
"This is a remarkable finding, and encourages us to possibly redefine what is considered the 'canonical coyote,'" she says. "It may not actually exist in the American Southeast. Coyote populations may more likely represent a mosaic collection of individuals with diverse histories, with some possibly carrying the remnants of an extinct species. We hope that these findings resonate with policymakers and managers, and influence how we think about endangered genetics."
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