Nonnative Species

Unwanted Guests of the Big Thicket

Invasive Animals and Insects

You may hear a ranger talking about invasive or exotic species during a program about the Big Thicket. These are species that are native to another country, island, or continent but have escaped, been released, or have moved into the Big Thicket usually with some help from man. Norway rats are a good example of a creature that hitched a ride in the ships of the early colonists and traders coming over from Europe and who are now found all over the North American continent. They are famous for entering homes as unwanted guests, eating the eggs of many native birds, and of doing vast amounts of agricultural damage. These invasive species often eat the food of, take over the space of, or even kill and eat the native animals of the Big Thicket. This can lead to the loss of some native animals or much damage to the native habitats and surrounding timber and agricultural lands that man is trying to manage. The preserve does all it can to limit the impacts from these species, but as noted below many are thriving in the warmer, wetter climate and dense forests of the Big Thicket.

Feral Hogs

One of the most damaging non-native animals found in the Preserve are feral hogs (Sus scrofa)—both in terms of their raw habitat-altering impact and the challenge to control them. An estimated 2-3 million feral hogs range over the state of Texas. The term “feral hog” applies to domestic hogs that were released or escaped to the wild, Eurasian wild boars introduced for sport hunting, and hybrids of the two. Brought to the United States by early explorers and settlers and first introduced to Texas in the 1680s, feral hog numbers have increased dramatically in the past decade.

Feral hogs are omnivorous and have voracious appetites. They compete with native wildlife for food, and can root-up large areas literally overnight. Feral hogs are known to eat acorns, tubers, fruits, insect grubs, carrion, amphibians, reptiles, eggs, birds, and arthropods (especially beetles) and can prey on the young of many mammals including white-tailed deer fawns. Because they can be carriers of a host of diseases and parasites such as brucellosis, tuberculosis, plague, and anthrax they also represent a health hazard to native wildlife, domestic animals, and humans.

Control efforts for feral hogs in the preserve include permitted hunting in 6 of the larger units and limited trapping and removal by Preserve staff in areas where feral hogs pose a threat to visitors or unique plant habitats. A recently completed Feral Hog Management Plan details a number of other tools that may be used. These will be implemented with a focus on the non-hunting areas where feral hog populations go unchecked and threaten both the flora and fauna of those units.

Other Unwanted Guests

Some of the other unwanted and non-native guests to the Preserve include nutria, Eurasian banded doves, starlings, and a couple of ant species. Nutria were once raised on fur farms. They are a large, dark-colored, semiaquatic rodent that have short legs, an arched body that is approximately 24 inches long, and they can weigh 12 to 20 pounds as adults. Their round tail is 13 to 16 inches long and scantily haired like a muskrats. Nutria live in semiaquatic environments eating the vegetation in the bottomland hardwood forests where an alligator may occasionally take one for dinner. Eurasian banded doves are a larger dove that competes with mourning doves for food and nesting habitat. Starlings have spread across most of the North American continent since their introduction in the 1890’s. Their competition for food and nesting sites has impacted many of the woodland songbirds. Red imported fire ants, have become well established in southeast Texas and invaded the preserve about 20 years ago. They directly affect native ants, other insects, reptiles, and ground-dwelling birds by swarming and biting the adults, and often killing the young as they hatch out of eggs. They are a hazard to humans and larger mammals as their stings, rather than bites, are highly painful and can cause serious reactions. A new ant species to the state that is now being found in the Preserve is known as the Raspberry Crazy Ant. It is a small ant that develops huge populations which impact native wildlife and enter human habitations in such numbers that they can short out electrical appliances, outlets, and motors.

Feral cats and dogs

Strays or abandoned animals that have entered the Preserve from adjacent lands and become self-sufficient—are also of concern at Big Thicket National Preserve because of their competition for resources, some of the feral dogs turning predatory, and the cruelty that arises from them being ‘dropped off’ on backcountry roads and left to fend for themselves. Also, predation of native birds nationwide by both feral and domestic cats continues to be seen as a significant cause of drops in many songbird population numbers.

Invasive Plants

Non-native plant species pose significant threats to Big Thicket’s natural resources. These include aggressive terrestrial plants and highly invasive aquatic plants. The highly fragmented nature of the preserve, which is crossed by numerous pipelines, road corridors, and waterways, as well as the potential for invasive weed seeds to come from neighboring private lands, from several urban areas, and from oil & gas production pads all have allowed several invasive plant species to gain a foothold in the Preserve.

Invasive plants are among the greatest threats to the ecological integrity of the preserve. Problematic species include Chinese tallow tree, Japanese honeysuckle, Chinese wisteria, trifoliate orange and Japanese climbing fern, which are regional concerns and widespread. New non-natives recently found in the preserve include Chinaberry, kudzu and coral ardisia. Water hyacinth, an aquatic invasive of particular concern, is prolific, and is expanding in the waterways. Common salvinia and giant salvinia are also found in the Preserve. They grow in dense mats on the water surface and eventually choke off the backwater channels and lakes.

Staff from Big Thicket National Preserve work on priority areas and invasive species each year using an array of Integrated Pest Management tools in an attempt to hold the invasive plants at bay. Numerous volunteers, and periodically, staff from the NPS’s Exotic Plant Management Team stationed in Beaumont, Texas also assist in this effort.

Last updated: April 7, 2015

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