Three sets of fur. Long, sharp orange-yellow incisor teeth with a powerful bite. Valves in the mouth and nostrils capable of sealing out water to remain submerged for up to 10 minutes.
With just those specifications, White Rock Lake’s nutria may seem menacing. Close up, however, an onlooker would likely be undeterred by the shy rodents, much smaller than the average beaver. One might even call them cute.
Photography by Michael Flowers
But that doesn’t mean they’re not a threat.
Native to lower-latitude South American countries like Argentina and Uruguay, nutria often disrupt their adopted ecosystems. Burrowing can undermine soil and cause erosion near shorelines. When a breeding-sized population is established in a new wetland, the animals can decimate native plant life and monopolize resources relied upon by native wildlife.
Dallas Department of Park and Recreation biologist Chris Morris says the population at White Rock Lake falls definitively short of infestation levels and estimates the population to be close to one to two family groups.
“They do a little bit of a mess right around that little dock area of Sunset Bay,” Morris says. “But they haven’t really disrupted or displaced any of our native populations of rodents or other animals, and they don’t seem to have just destroyed an entire marshland.”
The nutria mainly seem to stick to the east side of the lake, with the greatest concentration found in the Dixon Branch Creek wetland between Winfrey Point and the Bath House Cultural Center.
Weighing 15 to 20 pounds as an adult, the average nutria is about one-third the size of an adult beaver, although it may look similar due to its brownish coat and teeth. Much like the beaver, nutria are nocturnal herbivores who split time in the water and on land. The majority of its diet consists of aquatic plantlife, seeds, flowers and other plants found near wetland habitats.
“White Rock Lake being a lake itself, it also has plenty of vegetation. It’s got plenty of covered habitat. It’s pretty much a little oasis on the east side of Dallas. So why wouldn’t they prefer the lake?” Morris says.
Nutria were originally introduced in the United States in the 19th century for fur farming. Since then, the invasive “river rats” have spread to more than 20 states across the U.S, according to the Department of Agriculture.
A 2003 Dallas Observer article indicates nutria have been in Dallas’ lakes since at least the 1980s and originally spread to bodies of water like White Rock Lake through the City’s drainage system.
Morris says that while the natural predators in the area, like coyotes and bobcats, seem to prefer preying on other animals, some nutria have been attacked. That, along with January/February sub-zero cold snaps, have kept the population in check.
“I think as long as we still have those nice freezes right around February, it’s kind of knocking back their populations because whatever ones are good enough and breed up during the summertime, when we get those cold snaps, they’re not used to that because their evolutionary chain from South America does not have those cold snaps.”
Morris says there is currently no population control program for the nutria at the lake, but emphasizes the impact of invasive species like nutria on native ecosystems.
“If they all disappear tomorrow, that would be really awesome, because they still steal resources from our native populations,” Morris says. “But as far as invasive species go, they’re not as bad as the feral hogs. They’re not as bad as the emerald ash borer beetle or several other invasive species.”
Brandi Nickerson, a state and federally-permitted wildlife rehabber, has extracted problematic nutria from several properties where they caused ecological damage. She says it’s important not to get caught up in their looks.
“Hogs, almost everybody understands, and they’re fine with shooting hogs and getting rid of hogs because they’re not cute,” Nickerson says. “But when you have something that’s cute, like a nutria, people tend to not care that they’re invasive, but they also don’t understand the impact that they have.”
