NOVEMBER 11, 2016


Drivers traveling Highway 100 may have noticed the various lane closures and heavy equipment that line the road between Laguna Vista and Los Fresnos. The equipment is part of a project by TxDOT to install several wildlife crossings beneath the rural highway. Crossings are also being installed on FM 106 north of Laguna Vista.
“The latest developments are two projects that will add twelve wildlife crossings with a total cost of nearly $8 million,” said TxDOT Public Information Officer Octavio Saenz said via email. The state’s highway department is installing four crossings along Highway 100 and another eight on FM 106 which leads to the Laguna Atascosa National Wildlife Refuge (LANWR).
The refuge owns some 97,000 acres of land around the Laguna Madre, stretching from the Arroyo Colorado south to the Port of Brownsville, including the expansive restored wetlands area known as the Bahia Grande. Thousands more acres are privately owned by landowners who have entered into conservation easements with the U.S. Fish and Wildlife Service (USFWS) to help protect wildlife and habitat. As a result, much of the coastal region surrounding Port Isabel serves as a vital corridor for several species of endangered wildlife, including the aplomado falcon and the ocelot.
It was concern for the extremely rare ocelot that spurred the installation of the wildlife crossings, Saenz said. “The corridors are for all wildlife, but the high rate of mortality of the ocelots in South Texas is what spawned the construction of these crossings,”
Saenz said.
“The available scrub thorn where the ocelots live has been reduced to the areas known as the LANWR and several pockets of Willacy and Kennedy counties. Efforts have been made to before to protect the ocelot on SH 100,” he said.
Those efforts include the guardrail-like divider that currently exists along a portion of the highway, as well as several sections of jersey barrier that have large “perforations” along them, Saenz said “Chain link fencing funnels the ocelot into the designed crossing hindering its path where it could suffer an impact with a vehicle.”
Despite those efforts, several of the elusive cats have been struck and killed by motorists traveling on Highway 100 and FM 106. USFWS officials believe fewer than 75 of the animals remain the Rio Grande Valley, divided into two main populations. Approximately 35 are estimated to live on the ranchlands of Willacy and Kennedy counties, while just over a dozen cats have been documented within the Laguna Madre region. Since June 2015, seven ocelots have been killed by motorists – six males and one female, Saenz said.
Every ocelot death has a huge impact on the remaining population. After the death of a male cat in December, LANWR wildlife biologist Hilary Swarts described the effects as ‘devastating’.
“When you have such a small population, every individual is really valuable from both a reproductive standpoint and from a genetic standpoint,” she said then.
A small population decreases an animal’s genetic diversity in what is called ‘inbreeding depression,’ Swartz explained. “inbreeding depression … is when that inbreeding starts to affect individual fitness,” including physically visible deformities or animals with decreased fertility that reproduce at lower rates, she said.
The wildlife crossings being installed by TxDOT are part of a collaborative effort between the transportation agency and conservationists to try to reduce deaths among the remaining population. “TxDOT, Texas Parks and Wildlife, and USFW continue to balance the needs for safety and the needs for conservation in order to meet the mandate of each entity,” Saenz said.
TxDOT is also installing 18 cattle guards at entrances to privately owned lands that lie along the road in order to dissuade wildlife from crossing the road at those paths.

– By Dina Arevalo