Issue 6

What Does a Bear Do in the Woods?

SRS researchers are looking at the Louisiana black bear, a threatened species in the Lower Mississippi Alluvial Valley (LMAV), as a possible disperser of pondberry seeds.

Knowing if pondberry can be dispersed across widely distributed patches of bottomland hardwood forest that characterize the LMAV is key to determining whether the plant will continue to survive in the Mississippi Delta. “The seeds are relatively heavy,” says Paul Hamel, research wildlife biologist with the SRS Center for Bottomland Hardwoods Research (CBHR) who works on the dispersal aspect of the pondberry project. “We’ve ruled out wind because you would need a gale force with these seeds, and water will only disperse seeds a short distance.”

From their video surveillance studies in the Delta National Forest, SRS researchers found one definite disperser in the hermit thrush—a 6-inch, brownish forest bird that forages on the forest floor, and with its distinctive call, is more often heard than seen. “We found a good match between hermit thrush movements and populations of pondberry within that particular forest, but the hermit thrush does not usually fly from one forest patch to another,” says Hamel. “So we began to look at animals that range more widely.”

The red wolf and the Louisiana black bear, omnivores to varying degrees, seemed likely candidates. In 2003, Hamel arranged with the Jackson, MS, zoo to feed pondberry fruit to captive red wolves and Louisiana black bears. Hamel ruled out the red wolves, which are almost entirely carnivorous, after several failed attempts to get them to eat pondberry fruit. “To even get them to ingest the fruit I had to wrap them in meat patties,” he says. “Even then, the dominant female would carefully pick the meat off and leave the fruit.”

Hamel found that the Louisiana black bear would eat pondberry fruit readily—now comes the fun part of doing seed dispersal research. “If you’re going to evaluate an animal as a seed disperser, you have to see how well the seed germinates after it’s been eaten and defecated,” says Hamel.

First, you count how many seeds go in the bear and how many come out to measure the likelihood of the seeds getting through the bear’s digestive system. “Kind of like trying to retrieve an earring your kid has swallowed,” Hamel comments. Then you take the seeds and plant them in greenhouse pots to determine germination rates. “Over a third of the seeds we planted did germinate,” says Hamel. “So we have proof that the fruits will go through the bear and germinate.”

The next step is to track the movements of Louisiana black bears in the wild to see how far they actually go—and whether their movement patterns could, at least partly, provide an opportunity for wider dispersal of pondberry plants. CBHR researchers are continuing their video surveillance studies of pondberry patches for possible dispersal agents, and have entered into a partnership to track individual Louisiana black bears using global positioning satellite (GPS) radio collars. The U.S Army Corps of Engineers provided CBHR with funds to purchase the collars, which were provided to biologists with the Mississippi Department of Wildlife, Fisheries and Parks (MDWFP), who attach them to Louisiana black bears they are monitoring in the Delta National Forest and the Yazoo National Wildlife Refuge.

Once common in Mississippi, loss of habitat reduced the population of Louisiana black bear—one of 16 recognized subspecies of the American black bear—to less than 12 individuals by 1932. MDWFP biologists are using the radio collars to learn more about their home range sizes and movements in hopes of increasing populations. The U.S. Fish and Wildlife Service and the Delta National Forest are involved in helping with the capture of the bears, as are interested local landowners.

Hamel and the other pondberry researchers also want to know where bears go. “We know where the pondberry populations are, and we will be able to tell from the radio collar monitoring whether the bears have had the opportunity to visit and eat berries,” he says. “Then we can start to chart how far the bears move in the time it takes the seeds to move through their bodies. We’re just in the beginning, looking at patterns, but it’s an interesting possibility—and another reminder of how animals and plants are
connected.”

Back to Pondberry: Modest But Mysterious

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For more information:

Paul Hamel at 662–686–3167 or phamel@fs.fed.us.