Guiding Ocelots: Barriers to help funnel the cats going in at FM 106 underpasses

RIO HONDO — The Ocelot Underground is taking shape along FM 106.

The roadway between Rio Hondo and Buena Vista Road is in the midst of a $15.5 million overhaul more than 11.4 miles.

One of the unique features of the construction project is the addition of concrete underpasses to allow the endangered Texas subspecies of ocelot to pass under the roadway instead of dodging traffic to cross.

Vehicle mortality is the No. 1 killer of ocelots in South Texas, which are thought to number about 80. The good news is no ocelot highway fatality has been recorded since April.

The underpasses just may keep it that way.

The dozen massive concrete underpasses are different sizes, but are sufficiently wide and tall to accommodate deer, ocelots, bobcats, raccoons and more. Some are five feet-by-five feet, while others measure eight feet-by-eight feet.

The underpasses are different sizes depending on the distance they burrow under a highway. The longer the tunnel, the bigger the entrances, which biologists say encourages animals to enter the tunnels since they can see what’s at the other end.

“Right now what they’re constructing is this fence, and it’s the wildlife fence,” said Sergio Sustaita, a TxDOT engineer. “The fence is going on top and this is what hopefully will force the wildlife underneath to protect them from the traveling public.”

The idea is the fencing will funnel ocelots and other animals into the underpasses and keep them off the road.

The fence along the ocelot underpasses is an unusual one for rural South Texas.

There are several hundred feet of fencing already installed along both sides of FM 106, and it is a fine-mesh link fence which wouldn’t be out of place in a suburban backyard.

Most fencing in the region aimed at keeping livestock in place is barbed wire, which works perfectly well with cattle and horses.

Elsewhere, where nilgai roam, a type of fence known as a King Ranch fence is preferred. Nilgai, which can weigh as much as 500 to 600 pounds, frequently bash right through barbed wire but shy away from pushing over the King Ranch fencing.

But the King Ranch fencing, with its wide mesh with squares of six or eight inches or more, would prove little trouble to an ocelot bent on reaching the other side.

“They would slip right through it,” said Hilary Swarts, a federal biologist at Laguna Atascosa National Wildlife Refuge and an ocelot expert.

The concrete underpasses also have “catwalks” 18 inches high and 18 inches wide, that allow an ocelot to cross under a highway without getting its feet wet.

The $8 million in funding for the wildlife crossings was paid by TxDOT out of the department’s discretionary fund.

Boyd Blihovde, refuge manager at Laguna Atascosa, and other federal officials have had nothing but praise for TxDOT’s support in funding and building the underpasses.

FM 106 cuts through part of the refuge before terminating in the east at Buena Vista Road.

The FM 106 project is a major overhaul of the road. In addition to reconstructing the existing roadway, the road also is being widened. Currently it is closed to all but local traffic for people who live along the road.

FM 106 ocelot project

Cost: $15.6 million

Length: 11.4 miles

Area: From FM 1847 to FM 510

Work started: Nov. 2015

Completion:  Dec. 2017

Contractor: Texas SAI Inc.

Work done: 47 percent

Source: TxDOT