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Black Bears May Escape Gulf Oil Contamination, Experts Hope
By Jordan Schaul, PhD | National Geographic | July 2010
Photo by Pam Mcllhenny, USFWS
Daily reports and aerial footage of the direct impact of the oil spill on marine ecosystems draws anger, outrage, sadness, and much hopelessness among those of us removed, but tuned into the news updates coming out of the Gulf Coast region.
Certainly, much more heightened emotion is elicited among those directly affected by the fallout of this ecological catastrophe. But floating carcasses of bottlenose dolphins, growing numbers of oiled brown pelicans, northern gannets and sea turtles, and concerns over the health of shellfish and pelagic fisheries impress upon us how broad in scope and real this ecological tragedy is. And it is all the result of a single off-shore oil leak.
Among environmentalists (naturalists and some scientists included), frustration will likely grow as the collateral damage has extended beyond theory and shown real or perceived potential to endanger more than marine and estuarine ecosystems. The oil spill’s trajectory may now clearly reach riparian zones of inland forests and other biomes.
What may make this more insidious is that the impact on non-aquatic or non-surface water habitat and species is not so easily comprehensible or obvious or certain.
“THE GULF COAST DISASTER MAY DRAW ATTENTION TO SOME SURPRISING UMBRELLA SPECIES THAT LIVE WITHIN THE REGION.”
The wildlife that inhabits regions in the trajectory of the oil leak may not be particularly affected by the contamination in the short term, but if anything, the Gulf Coast disaster may draw attention to some surprising umbrella species that live within the region.
Although they are not so closely tied to estuarine habitat or even to some riparian zones, these uber-iconic megafauna associated with bald cypress swamps, like the Florida panther (Puma concolor coryi), one of 30 subspecies of the cougar or mountain lion, and one of the most endangered mammals on Earth, serve as keystone species representing diverse faunal groups. [Read the blog post-Florida Panther Fights for Survival Again–This Time in Washington D.C.]
These include marine and brackish water ichthyofauna (fish) and herpetofauna (reptiles/amphibians), avifauna (birds), and a host of mammalian species. Some include species that have already been impacted by the oil leak from oiled Ciconiiformes (e.g., herons) and Pelecaniformes (e.g., pelicans) to species more indirectly impacted like piscivorous and scavenging raccoons to living dinosaurs. The impact on American crocodiles which were downlisted from Endangered to Threatened in 2007 and American alligators are largely unknown.
Aerial photos of a bear in a food plot, June 6, 2010.
Photos by Jeb Linscombe, Biologist Louisiana Department of Wildlife and Fisheries
Two subspecies of the American black bear, the Florida black bear (Ursus americanus floridanus) and the Louisiana black bear (Ursus americanus luteolus), have received less attention. But they also serve as umbrella species in the Gulf Coast region for a diversity of fauna living in somewhat disparate zoogeographic regions where these occasional and common peri-domestic, and highly adaptable opportunistic omnivores find themselves, as suitable and available habitat continues to shrink.
The Louisiana black bear was federally listed as a threatened species under the Endangered Species Act in 1992 and is one of the most imperiled of the 16 subspecies of American black bears. Two subspecies also range throughout northern Mexico.
Any black bear subspecies living within the historic range of the Louisiana subspecies is also provided with the same federal protection as the threatened Louisiana black bear. This subspecies currently range throughout eastern Texas, the southern part of Mississippi, and the state of Louisiana (they are currently confined to three small populations in Louisiana). The historic range of the subspecies includes southern parts of Arkansas.
In March of 2009, the U.S. Fish & Wildlife Service (USFWS) designated critical habitat for the Louisiana black bear in the state of Louisiana, where the bear is also celebrated as the state mammal. The designated area covers 1,195,821 acres spanning 15 parishes.
Prior to this, large-scale efforts to create forest corridors in the state of Louisiana were launched as part of a national and federal bear-recovery plan.
Several breeding populations of the Louisiana black bear have been identified north of coastal zones in habitat that includes cypress-tupelo swamps also known as southern deepwater swamps.
Areas where breeding populations exist as well as areas of preferred habitat type like bottom wood hardwood forests are still important to the conservation and management of the Louisiana black bear.
Management efforts require that the habitat is restored and protected from threats to degradation and fragmentation and other human disturbance.
The stability of the bear population must be carefully monitored and as for any species, consideration of augmentation through reintroduction programs must be carefully planned.
These bears also utilize riparian habitat, which refers to the interface between the water’s edge and the specific surface water run-off in the form of rivers, streams, and creeks.
The bears less commonly utilize brackish and freshwater marsh habitats. When they do use marsh habitat they can be found traveling across elevated spoil banks which may serve as travel corridors.
Marsh wetlands are subjected to continuous flooding and are predominated by grasses, sedges, and other herbaceous vegetation, including some of the flora that the bears may consume.
Inland, the black bears primarily use the swamp and particularly the cypress and tupelo trees as denning sites. The bears den in hollow trees, which also provide “escape cover” for these shy and reclusive animals.
A bear crossing a spoil bank. “These banks crisscross the coastal habitat and are important travel corridors for the bears,” says Maria Davidson, Large Carnivore Program Manager, Louisiana Dept. of Wildlife & Fisheries.
Photo by Thomas C. Michot, USGS-National Wetlands Research Center, Lafayette, Louisiana, 1996
As a part of a habitat and species restoration initiative, the Black Bear Conservation Coalition is managing stands of these trees to preserve critical denning habitat for Louisiana black bears. It is the cover and not so much the abundance of food resources that draw the bears to specific sites within the cypress swamps which are home to upwards of 400 vertebrate species.
As opportunistic foragers, the bears have quite catholic tastes and will just as readily feed on yellow jacket nests and reptile eggs along with other available and easy-to-access foodstuffs. They are not particularly piscivorous, that is predisposed to feed on fish in this habitat, or as likely to seek out challenging prey such as aquatic rodents that make the deep water swamp an underwater refuge.
It’s much easier to feed on accessible herbs, berries, nuts, grasses, palmetto hearts, ants, and grubs. But occasionally, the bears will feed on small mammals and carrion. And similar to raccoons or skunks or scavenging birds, exposure to just one carcass contaminated with oil can be potentially lethal to a bear.
“LONG-TERM EFFECTS ON INDIVIDUAL BEARS OR OTHER WILDLIFE MAY INCLUDE SUPPRESSION OF THE IMMUNE SYSTEM AND IMPAIR REPRODUCTIVE CAPACITY POTENTIALLY IMPACTING POPULATION LEVELS.”
Long-term effects on individual bears or other wildlife may include suppression of the immune system and impair reproductive capacity potentially impacting population levels. For more information on the impact of oil exposure on wildlife, please read this USFWS report.
Paul Davidson, executive director of the Black Bear Conservation Coalition, points out that it would be quite rare for black bears to become victims of this Gulf Coast tragedy unless an unusually strong tidal surge from a powerful storm were to push oil-contaminated water beyond marsh habitat, precipitating a major fish kill.
My colleague, Dr. Joe Clark, chief of the U.S. Geological Survey’s Southern Appalachian Research Branch at the University of Tennessee, agrees that the three Louisiana black bear populations are quite well insulated from contaminated waters living inland in forested habitats.
He adds that two are somewhat sequestered north of Highway 90 (the coastal population is south of 90), a major East-West expressway that transects the southeastern United States. Furthermore, Dr. Clark added that his research of black bear habitat disturbance by Hurricane Katrina indicated that the impact on bears was minimal.