Wildlife and aviation programs collaborate on deer population study

An outbreak of often-fatal epizootic hemorrhagic disease (EHD) afflicted more than 500 white-tailed deer in Indiana's Allen, Porter and Wabash counties last summer.

The Indiana Department of Natural Resources, which adjusts hunting deer limits in counties affected by such outbreaks, needs accurate but hard-to-obtain population estimates and other related data to make their management decisions.

"Successful wildlife management requires us to know how many animals we have," said Purdue University's Patrick Zollner, professor of quantitative ecology in the Department of Forestry and Natural Resources. "White-tailed deer, coyote and turkeys are three very prominent, charismatic species in the state, and we don't have good numbers for their populations at all."

Zollner leads a five-year project to develop better methods for monitoring the population sizes of these animals. The project team will compare the effectiveness of data-gathering methods from drones, crewed aircraft and trail cameras. The project aligns with the commitment of Purdue's One Health initiative to expand knowledge of the interdependent nature of animal, human and environmental well-being.

"There's a lot of uncertainty associated with your ability to detect wild animals in natural habitats. And absence of proof is not proof of absence," Zollner said. The study will help Indiana DNR understand the accuracy of various methods and how much they will cost.

Last summer's EHD outbreaks will reduce the white-tailed deer populations in the affected counties. "We want to understand not just how many deer we have, but also how long it takes for a deer population to recover from a disease outbreak like that," he said.

The work will encompass factors that drive disease emergence and builds on previously published research. Zackary Delisle contributed additional foundational insights as a Purdue Ph.D. student and later as a deer research biologist in the Indiana DNR Division of Fish and Wildlife. Now a National Park Service ecologist in Alaska, Delisle has an ongoing collaborative role in the project.

Additional data would enable Indiana DNR officials to operate a more flexible and fine-scale system for regulating harvest in disease outbreak locations.

"Right now, we don't even know what the population was in the first place, and we don't know how long it takes it to recover," Zollner said.

The new study also will examine transmission patterns of bovine tuberculosis, which affects livestock producers. Interactions between deer and cattle can spread the disease. Small species such as raccoons may serve as disease carriers as well.

"Raccoons aren't going to be killed by the disease, but they may help maintain a disease reservoir in the background," Zollner said. "There's a lot that we don't know. How much is this full cast of characters and their interactions influencing the ability of bovine tuberculosis to stay in a system versus being eradicated?"

The research team will sample selected locations across the state, including Franklin County, which borders Ohio in southern Indiana. "Franklin County has had incidents in the last decade of both EHD and bovine tuberculosis," Zollner said. The team will use the data to develop statistical models that can estimate species populations statewide.

The researchers will collect aerial data from early December until mid-March, when there are no leaves to obscure imagery. They also did some sampling earlier this year. On cold days with snow on the ground, the Purdue crews can operate both color video and infrared cameras.

Project collaborators include Joe Caudell of Indiana DNR's Division of Fish and Wildlife; Sonja Christensen, assistant professor of fisheries and wildlife at Michigan State University; and Wendy Beauvais, assistant professor of epidemiology and public health in Purdue's College of Veterinary Medicine.

Additional collaborators are Brian Dillman and Joe Hupy, both associate professors in Purdue's School of Aviation and Transportation Technology. Dillman oversees the crewed flights, while Hupy manages the drone sampling operations.

Purdue and MSU students play key roles in the project. MSU Ph.D. student Mike Shaw works with Christensen on fieldwork across the state, tracking the impact of EHD on white-tailed deer in recently affected areas. Postdoctoral researcher Jonathan Brooks, who recently completed his Ph.D. working in Zollner's lab, models transmission of bovine tuberculosis between white-tailed deer, cattle and raccoons with Beauvais.

Hupy works with Purdue wildlife Ph.D. student Tina Jackson in sampling animal populations from drones. And Purdue senior wildlife major Emma Johnson leads a team of undergraduates who operate an infrared camera from a Purdue Aviation Sky Arrow aircraft to collect data on white-tailed deer densities across the state.

Johnson's presentation of related research earned her the Best Flash Talk Award at last year's conference of the Indiana Chapter of The Wildlife Society.

"We are doing better research by collaborating in this way, but we're also giving both wildlife undergraduates and aviation undergraduates unique experiences to open up more opportunities for them in the future," Zollner said.

Provided by Purdue University