American black bear

‘Bottleneck’ still threatens black bears in the Ozarks

Efforts to stop the decline of black bears in the Ozark mountains should continue in order to ensure healthy populations, experts say.

Deforestation at the turn of the 20th century led to a loss of habitat for black bears in the Central Interior Highlands, an area that consists of Missouri, Oklahoma, and Arkansas. To repopulate the mountainous region, more than 250 bears from Minnesota and Manitoba were relocated to Arkansas in the 1950s and 1960s.

To examine the genetic diversity of black bears in the region today, researchers collected and analyzed DNA samples from black bears from five geographical locations. Hair samples from Arkansas, Oklahoma, and Missouri were analyzed. Additionally, blood samples from hibernating bears in Minnesota and tissue samples from Manitoba were examined for their genetic signatures.

“The focus of our study was to determine the effects of the reintroduction of black bears in the Ozark and Ouachita Mountains and how that reintroduction affected population genetics in the region,” says Emily Puckett, a doctoral candidate in the Division of Biological Sciences at the University of Missouri.

“We also wanted to determine if we could find evidence of the population that was formerly here and whether or not they mated with the reintroduced bears or if they had gone locally extinct following deforestation.”

Cut-off populations

Previous study results suggested that black bears were present throughout the CIH in the 1920s, contrary to previous beliefs. The current research indicates the bears had a remnant lineage in the northern Ozarks of Missouri, Puckett says.

The team also found that current black bears went through a brief “bottleneck,” where bears were cut off from each other and genetic diversity was reduced. However, the team also determined that the reintroduction of bears to the CIH in the 1950s and 1960s helped to restore diversity and increase population size in the Ozarks and Ouachitas.

“We observed the genetic signature of the Ozark population from Arkansas in Missouri, meaning that the bears moved north,” says Puckett. “These bears bring with them their higher genetic diversity, which may help Missouri’s bear population in the future.

“The movement north also indicates that formerly fragmented forests may have regrown thereby connecting Missouri bears to the Ozark subpopulation that was further south.”

“This represented one of the largest sample sizes in a study of this type,” says Lori Eggert, associate professor of biological sciences. “By using multiple genetic markers on samples collected from Missouri and Arkansas, hunted bears in Oklahoma, and live dens in Manitoba, we were able to conduct genetic and statistical analyses to analyze trends and gain robust conclusions.”

The team suggests that conservation efforts to promote forest connectivity will help protect bears throughout the region, so that subpopulations are not isolated, as was the case in Missouri, and genetic diversity remains high.

“Geneticists get concerned when populations have low genetic diversity,” Puckett says. “Low diversity can be indicative of low population size. When harmful mutations arise in a gene pool with low diversity, they may increase in frequency leading to poor fitness and health in the population. That’s why these management suggestions are so important.”

The Missouri Department of Conservation, Arkansas Game and Fish Commission, US Fish and Wildlife Service, and Safari Club International supported the research. The study appears in the journal Molecular Ecology.

Source: University of Missouri