In a recent study, researchers at the University of Georgia’s Savannah River Ecology Laboratory and UGA’s Warnell School of Forestry and Natural Resources identified new ways to prevent the spread of rabies in raccoons in northern Indiana.

The researchers conducted fieldwork in the spring of 2011 to help determine how to perfect the technique of aerial baiting — filling bait with a vaccine to provide rabies immunity to wild carnivore vectors of rabies. While the method has reduced the westward spread of rabies in raccoons in the eastern United States, it hasn’t been successful enough in completely eliminating rabies.

As a result, researchers set out to determine if they could make raccoons more receptive to bait by monitoring raccoon movement. Northern Indiana’s fragmented land and high densities of raccoons and opossums made it the optimal location, according to Assistant Research Scientist James Beasley.

“The first thing we wanted to address was the fact that wildlife don’t utilize the landscape randomly, but concentrate movements in areas of preferred habitat,” Beasley said. “We wanted to take movement data from raccoons and build resourceful models to identify hotspots in the landscapes where there are concentrated areas of raccoon activity.”

Beasley and Professor and Director of the Savannah River Ecology Laboratory Gene Rhodes created traps in eight sights and estimated the density of raccoons. Once they knew the density, they distributed placebo baits with a biomarker Rhodamine B, which is found in whiskers and hair. “When we recaptured the raccoons, we were able to see if they ate the bait,” he said. “We then went in a few weeks after and trapped individuals at increasing distances away from the bait zone.”

Beasley and Rhodes found that using observed movement of raccoons to determine bait distribution did not increase bait consumption by raccoons. “We didn’t have very high uptake in any of our sites, which is similar to other studies,” he said.

Beasley and Rhodes also determined the probability of raccoons consuming baits farther away from the baited area.

“We know animals aren’t confined,” Beasley said. “As you move away from the baited area, the probability of the individual consuming the bait decreases.”

But, Beasley said some raccoons did consume the bait farther away from the baited area, which means there is a possible application for using bait in urban parks. He said baiting inside a park can treat individuals outside of the park as well.

Researchers also wanted to know how much bait that was set for raccoons was consumed by opossums; however, they found it wasn’t significant enough to explain low consumption rates from raccoons.

Based on the results of the study, Beasley noted that bait must be repeatedly distributed to help create rabies immunity in raccoons. He plans to further his research to determine how to better the aerial baiting technique to develop more rabies immunity in raccoons.

“I would like to go back in and repeat the study multiple times in the year to see how this influences uptake,” he said. “I would also like to study bait flavor and bait palatability.”

Beasley would also like to complete the study in eastern Ohio, where the land differs from the land in northern Indiana. In eastern Ohio, raccoons are more constrained in certain areas because of the way forests are distributed.

Beasley hopes that this and future research will help develop a more successful aerial baiting technique to reduce the spread of rabies.

Researchers have discovered several bird species that host ticks carrying Lyme disease bacteria in northwestern California as well as another pathogen that causes chronic illness in humans.

“The role of birds in the maintenance of Lyme disease bacteria in California is poorly understood,” said Erica Newman in a release. Newman is a UC Berkeley Ph.D. student in the Energy and Resources Group at the University of California, Berkeley and lead author of a recently released study that “did a molecular study of bird blood, ticks present on the birds, and the associated species of bacteria that they were hosting.”

“This is the most extensive study of the role of birds in Lyme disease ecology in the western United States, and the first to consider the diversity of bird species, their behaviors and their habitats in identifying which birds are truly the most important as carriers.”

UC Berkeley researcher Erica Newman, pictured in front of chaparral, where she studies bird communities. Chaparral biodiversity, including bird communities, is largely understudied because of the difficulty of detecting wildlife in dense shrub habitats.
Image Credit: David Hembry

Using mist netting, Newman and others in the team trapped over 623 birds from 53 different species from 14 sites in the UC Hopland Research and Extension Center in northwestern California and took blood samples to analyze them for the presence of pathogens. More than 99 percent of the ticks discovered were western black-legged ticks (Ixodes pacificus). Of the birds, 23 species were found to be infected with Lyme bacteria, though a few species harbored more subtypes of the disease than others.

The teams study showed that the lesser goldfinch (Spinus psaltria), oak titmouse (Baeolophus inornatus) and the dark eyed junco (Junco hyemalis) were all competent hosts of Lyme disease bacteria (Borrelia burgdorferi) and harbored many more subtypes than other species. The golden crowned sparrow (Zonotrichia atricapilla) was found to be infected more frequently than other species. They also found, for the first time in the world according to Newman, that some bird species were hosting a related disease that humans can contract ­­— Borrelia bissetttii — which has infected people in Southern California and Europe.

But not all ecosystems showed an equal level of infection.

“The birds that were associated with dense oak woodlands in California had higher levels of Lyme disease bacteria in them,” Newman said. “Basically the different habitats and their associated birds really showed different levels of infection.”

While chaparral shrub ecosystems tend to have high biodiversity with many species endemic to California, birds in those areas weren’t found to host Lyme disease at any significant rate.

But the birds that were found to host the disease were coincidentally the same bird species that happened to benefit from suburbanization in California, meaning they spend more time around humans.

Newman said that the team’s findings could have implications for land development policies in California such as the way chaparral is currently cleared to reduce fire risks. The practice of clearing the land may favor birds hosting Lyme disease that move into areas once the chaparral is gone.

“We may be playing around with disease ecology by trying to manage the fire ecology of a region,” she said.

Researchers with South Dakota State University are finishing up a three-year study funded by the South Dakota Department of Fish, Game and Parks and the South Dakota Agricultural Experiment Station that will determine which fall cover crops lure deer away from livestock feed in South Dakota, particularly during the months of August and September.

The study is the first controlled experiment with fall cover crops, although some landowners experiment with cover crops and deer on their own, according to Jonathan Jenks, distinguished professor at the University’s Department of Natural Resource Management and lead researcher on the study. Landowners in the state are often faced with large herds of 100 to 200 deer eating their stored livestock feed including hay and distiller grains.

With limited information so far north in the Great Plains, South Dakota proved to be a good location for the study. Further, Jenks manages a captive deer herd of 50 white-tailed deer at the Wildlife and Fisheries Sciences Research Facility at South Dakota State University. “Because we have a captive deer herd at South Dakota State, there is more control when evaluating the deer rather than just planting crops and seeing what gets eaten,” Jenks said.

In response to SDFGP’s interest in forages that best attract deer, Jenks and graduate student Troy Weiberg put together a project evaluating a number of forages that had been used in other studies.

As part of the project, Jenks and Weiberg chose six cover crops based on previous literature from state biologists — purple top turnips, Daikon radishes, Austrian winter peas, winter rye, chicory and crimson clover — and planted them at the South Dakota State’s Wildlife and Fisheries Research Facility. Based on their data, they found that deer were particularly drawn to purple top turnips, Daikon radishes and Australian winter peas — likely because they are more digestible and have the highest protein content.

Jenks plans to provide wildlife officials with the results as soon as they are compiled. He hopes that his research will help provide wildlife officials recommendations in regards to which cover crops should be used to help manage South Dakota’s deer population.