Wednesday

How Do Fish and Wildlife Survive Severe Cold Weather?

Cold-stunned sea turtles at the Brownsville Ship Channel

This week many Texans are seeing snow for the first time as a record cold front plunged our state into single-digit temperatures.

While humans struggle with power and water outages, how are our native fish and wildlife faring? For many animals, it depends on how well prepared they are, including having healthy fat reserves. 

That’s reassuring for those of us who have been building up our own fat deposits.
Texas has few true hibernating animals. But many animals do slow way, way down.

Many native wildlife species will be able to survive short durations of historic low temperatures and snow events. However, long-term impacts on a variety of wildlife and their habitats, especially on vegetation, may not be known for weeks.

Here’s a rundown of how different animals handle the cold.

 

Mockingbird, the Texas state bird, fluffed up in the cold.

BIRDS  

Though they appear to be small and delicate, birds actually have several strategies for toughing out cold temps.

 

They prepare for winter by adding more feathers, in American Robins up to 50% more.
They create their own puffer coats by fluffing their feathers to trap warm air. That’s why some birds look extra fluffy in cold weather.
 
How do they keep their feet from freezing? Birds have an adaption called countercurrent heat exchange.  As explained by the Cornell Lab of Ornithology: “Cool blood com­ing back from the foot travels through veins grouped around arteries that are sending warm blood from the body to the foot. Heat is transferred from the warm arteries to the cool veins.”
 
Birds flock to food sources to build up their energy reserves. Many Texans have noticed large flocks of robins and cedar waxwings in their neighborhoods feasting on fruit.
 
Birds that have done a good job building up fat and are generally healthy will make it through the winter.  Those that have little fat will have a hard time.

 

Surprisingly, urban communal roosts may harbor some of the most vulnerable birds. With past arctic blasts, bird deaths have been most notable among the large populations of great-tailed grackles in Texas cities.
 
 “I've seen autopsy reports of some of these dead grackles from Austin and they usually found the dead ones had heavy internal parasite loads, like liver flukes,” says Cliff Shackleford, TPWD ornithologist. “Those individuals were already weakened.”
 
TPWD staff and the public have made these observations regarding bird health and mortality due to the winter weather.


White-tailed deer in the snow.


MAMMALS 

You may have noticed your neighborhood squirrels out busily digging. They’re likely checking their stashes of food they stored to survive cold weather. The two most common squirrels in Texas, the gray squirrel and the fox squirrel, rely on these caches, along with their fast reserves and cozy nests to make it through the winter.

Deer and coyotes grow heavier winter coats to help them survive the colder weather. These winter coats are generally thicker and have a well-developed underlayer. As with birds, the healthy animals with ample fat will make it through the winter, while those in poor health may succumb to the cold, wintery conditions. 

Tri-color bats in Buffalo, Texas

Texas bats have different approaches to winter, depending on the species. Since bats rely on insects for food, and insects are scarce in the winter, they must either migrate to where the insects are or hibernate to wait out the winter. 

The bats that choose to hibernate will find a suitable cave or culvert and settle in. But that doesn’t mean they’re completely dormant.

“Bats will be down in hibernation for two weeks or so at a time,” says Nathan Fuller, TPWD bat specialist. “Some kind of trigger causes them to arouse from their hibernation and do some stuff — they go to the bathroom, fly around a little bit. This cycle can go on for months.”

Unfortunately, Texas bats are facing the deadly threat of white-nose syndrome. The syndrome has caused millions of deaths in bats across North America. The fungus that causes white-nose grows on hibernating bats, acting as a chronic disturbance and possibly causing dehydration. 

To help monitor the disease’s progression, TPWD wildlife specialists are asking the public to report dead or sick bats to wns@tpwd.texas.gov. Be sure to include a general location and, if possible, a photograph.


FISH 

During cold weather, many fish slow down and head for deeper waters where it’s somewhat warmer. Unfortunately, fish in shallow water, especially in our coastal areas, may not survive a hard freeze, resulting in large ‘fish kills’ during cold snaps. Our Kills and Spills team collects data on these events to assess the overall impact on Texas fish populations.

When temperatures on the coast fall below freezing, TPWD may close certain areas to saltwater fishing as we had to do for two days this year.

"The high mortality that a freeze can cause may deplete fish stocks for years," said Robin Riechers, director of TPWD’s Coastal Fisheries Division. "Protection of the surviving fish during the few days when they are especially vulnerable to capture would likely shorten the time period for overall recovery of coastal species, especially spotted sea trout."

 

American alligator in winter at Powderhorn WMA

SEA TURTLES, SNAKES AND OTHER REPTILES 

Reptiles such as snakes, alligators and freshwater turtles go into a state of dormancy, called brumation. They’ll find a crevice or burrow to crawl into and wait out the winter.

“They’re cold-blooded. Their metabolisms just slow down with the environment,” says TPWD wildlife biologist Nathan Rains.

One reptile that has a harder time with cold snaps is the sea turtle. When water temperatures plunge, sea turtles become “cold-stunned” and unable to swim. They float up to the surface and become vulnerable to boat strikes or wash ashore and become stranded. 

The National Park Service, working with TPWD and other partner organizations, leads the effort to rescue cold-stunned sea turtles. The turtles are taken to rehabilitation facilities to recover and then released back into the wild when temperatures warm up.

Why not let nature take its course? 

As the NPS website explains: “The green sea turtle is protected as a threatened species by both the state of Texas and the federal government. Even though their population is growing, their numbers are still too low to afford losses. Also, the Intracoastal Waterway and other deep channels, created by humans for boating and shipping, may entice sea turtles to venture deeper into the Laguna Madre and further away from the safety of the Gulf of Mexico.”

Severe cold weather definitely takes a toll on our fish and wildlife. But the majority of animals will survive to warmer days.

If you want more content like this, subscribe to Texas Parks & Wildlife magazine. Whether in print or through our mobile app, choose the version that works best for you.

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