San Antonio River Authority Working To Control Nutria Population | Texas Public Radio

San Antonio River Authority Working To Control Nutria Population

Jul 6, 2016

The San Antonio River Authority is spending $25,000 to trap a non-native rodent that’s wreaking havoc along the river banks.

The banks of the San Antonio River at first appear lush with vegetation, but once you look closely, you see the barren spots. That’s because the nutria, native to South America, have moved in. They can’t resist devouring the stems and roots of the plants that grow here.

So, the San Antonio River Authority has set 60 traps that span roughly 5 miles from Eagleland to the Mission Reach to catch the nutria which are sometimes called “river rats.”

Kirk Moravits

Kirk Moravits is the natural resource management specialist for the San Antonio River Authority.

"So you can see we have a trap on the east bank of the San Antonio River right across from us," Moravits says. "You can see right under the trap that there’s bare dirt, bare ground. There used to be vegetation that covered that entire area. The nutria eat that vegetation, they eat the base of the plant, they remove that plant—so that bank isn’t stabilized anymore."

Nutria have beady eyes, orange teeth, a hump back and a long, rat tail. They’re just smaller than beavers. And some people even find them cute.

But Moravits says the nutria are burrowing into the banks of the river and that’s causing erosion. Nutria can eat 25 percent of their body weight a day in vegetation. Moravits says that they take away resources, food, and habitat from native species like raccoons, turtles and opossums.

"Some of our sparrows—the swamp sparrow likes to nest in those rushes and reeds. And that’s a habitat specialist; they require certain habitats, so they’re definitely in direct competition with those nutria," Moravits says.

The traps they use to catch the nutria are made of metal and are about the size of a small dog crate. Each trap is covered with a brown paper bag to keep the nutria calm and cool until they can be removed. Moravits says the animals are then euthanized humanely.

"Respect everything in the ecosystem," Moravits says. "It’s all about respect, but it’s also about balance. These nutria are destructive and create a lot of problems. It’s our job to manage these nuisance animals."

Aside from the environmental destruction, the nutria explosion is taking place in an area near the Spanish missions that was declared a world heritage site and is expected to increasingly draw thousands of tourists. The River Authority says they are not concerned about nutrias’ impact on tourism as they are mostly nocturnal.  

Rob Gonzalez, who works as a landscaper in the area, says people who live along the river don’t like seeing rodents. 

"It’s not good for San Antonio water," Gonzalez says. "They say about keep San Antonio clean and they really don’t. I’m a landscaper and I do this every day, and this doesn’t help at all."

Michael Street thinks the River Authority is going a little too far in their approach. He stopped to talk while walking his dog, Tim Johnson.

"If they causing problems, we need to get rid of ‘em, and trapping them, yeah," Street says. "That’s way good—but killing them, no. We can do something far short of killing them, cause they love their lives just like everything else does."

Street says he wishes the River Authority instead would relocate them, build a habitat for them, or use them for education.

Moravits says before the nutria got here, the banks were lined with vegetation and the river was full of aquatic vegetation. In the past month , the River Authority has caught 48 nutria. The River Authority doesn’t know exactly how big the population is, but they say the nutria are damaging more than 300 acres of the Mission Reach ecosystem.

Moravits says they’ll never eradicate them all, but they do have to manage their numbers.