Rio Grande scrub restoration could assist ocelot population
Protective devices help plants survive, add to cat habitat.
Native plants in the Rio Grande Valley are nothing if not tenacious.
Each one seems to have some type of thorn or sticker or tough skin designed to make it as difficult as possible to eat, or enabling it to fend off insects or to keep from being colonized by parasites.
But even this resilient and drought-resistant flora can use a helping hand.
A program at Laguna Atascosa National Wildlife Refuge is attempting to do just that. The goal? Accelerating the complete restoration of native Tamaulipan thornscrub from 25 to 30 years to maybe half that time.
“Those tree protectors we call them — tree tubes or tree protectors — they do two major things to help the plant survive,” said Kim Wahl, a U.S. Fish and Wildlife Service plant biologist who is leading the restoration effort. “Without them on, rodents and rabbits will chew them down until just little nubs.”
“They also protect against natural elements like sunlight, and the dew will condense inside the tube and run down the tube,” she added. “The humidity inside those tubes is higher, and the temperature is a little bit lower.”
Re-establishing native habitat from what is now Rio Grande Valley farmland is both time- and labor-inten- sive. It was only 100 years ago, prior to the agricultural revolution that arrived with electricity, pumps and irrigation, when practically the entire Valley was covered in dense thornscrub.
Wahl said about 275 acres were replanted between October and March this year to restore Tamaulipan thornscrub in Cameron and Hidalgo counties. Most of that acreage was planted without the protection of the 3-foot tree tubes.
Among the species planted at Laguna Atascosa were snake eyes or devil queen, Texas torchwood, crucita or Christmas bush, trixis or American threefold, lantana, Berlandier croton and manzanita, or Barbados cherry, Wahl said.
For her part, Wahl is less interested in overall restoration recovery time than she is in how animal and plant species adapt to the new habitat. She says wildlife can use the plots almost immediately after planting.
“I don’t know if we have a good idea of just how much time it will take” to completely restore the thorn- scrub habitat, Wahl said.
“But from the time we plant, it becomes useful right away for small mammals, rodents, pollinators like bees and butterflies that first year, and then to be use- ful for birds, it needs to start seed production or the trees get large enough for nesting,” she said. “From there, you are beginning to be more beneficial for larger mam- mals and ultimately we’re looking at making these areas suitable habitat for ocelots.”
At any one time, there are about 15 of the endangered Texas subspecies of ocelot on the Laguna Atascosa refuge, and about 80 in South Texas. Habitat restoration is considered a key compo- nent to saving the wildcats, which, unlike their bobcat cousins, can be quite particular when it comes to habitat.
Hilary Swarts is a biologist with the U.S. Fish and Wildlife Service stationed at Laguna Atascosa. She also is an expert on ocelots.
Swarts says there are three primary threats to the Texas ocelot: highway deaths, lack of genetic diversity and loss of habitat.
“The way I look at it, their immediate threat is road mortality, and there are two ways to combat that,” she said. “One is keeping them off roads by installing crossings, and one is keeping them off the road by establishing contiguous, good habitat where they don’t need to run off into the middle of nowhere.
“The sort of mid-range threat is the genetic issue” involving inbreeding within an ocelot population that is isolated from ocelot populations in Mexico, she said.
“Butreally their long-term problem, to me, is space,” Swarts added. “So that’s where habitat comes in. The loss of habitat initially is what prompted those two other threats to come to the forefront.
“The longer I’ve been working on this project, the more I understand habitat is the first step in under- standing the plight of this species,” Swarts said.
The problem of highway mortality is being addressed by about a dozen new under- passes being installed along roads by the Texas Department of Transportation in ocelot-friendly areas such as FM 106 between Rio Hondo and the refuge on Buena Vista Road.
The second threat might take some diplomacy to persuade Mexican officials to share a female ocelot or two to reinvigorate the genetic line of the Texas subspecies.
The third problem — hab- itat restoration — is being attacked with the tree tubes.
Wahl said the tubes will stay in place for nine months, and by that time the plants’ root systems will be well established and provide some defense against browsing animals. The tubes will then be re-used at another restoration site.
In November, the tubes will come off the plants at Laguna Atascosa, and will be reused at another site.