New study identifies the greatest threat to wildlife across North America and Canada: people

You see posts like these on neighborhood Facebook pages all the time: “An owl just flew into my window and appears stunned! Help!” or “I found a baby squirrel on the ground after the wind storm last night. Who do I call?” The answer is a local wildlife rehabilitation center—licensed individuals and organizations that take in hundreds of thousands of sick and injured wild animals nationwide each year. Wildlife rehabilitators see the highest number and greatest range of species of any government or nonprofit organization in the country, giving them unique insight into animal health—and making them great bellwethers of what’s happening in the broader environment.

A few years ago, biologist Tara Miller (GRS’22)—then working with Defenders of Wildlife—met Wendy Hall, cofounder of the Adirondack Wildlife Refuge in Wilmington, N.Y. Hall mentioned some weird occurrences she had noticed in her job over the last few years: black vultures in the Adirondacks, unusual since they are typically a southern species, and earlier “baby seasons” in many species, which researchers have linked to climate change. Miller was intrigued by the idea of using animals’ presence in rehab centers to study the impact of people and climate change on North America’s wildlife.

Miller (who uses they/them pronouns) is the lead author of a first-of-its-kind study that compiled hundreds of thousands of records from 94 wildlife centers across the United States and Canada to investigate the threats facing more than a thousand wildlife species by region—including which threats affect which animals and how effective wildlife rehab centers are at treating their patients. The Boston University–led team hopes their study, published in Biological Conservation, will help inspire safety interventions and inform the conversation about incorporating wildlife into disaster management plans.

The report includes examples of bald eagles sickened by lead poisoning, sea turtles entangled in fishing gear, and big brown bats colliding with buildings. In other words, human activities often have a devastating impact on wildlife, Miller says. What’s more, the researchers showed that more animals were admitted to wildlife rehab centers following some climate change–linked extreme weather events.

“A lot of what we found in the research isn’t going to shock anyone, but you want to be able to tell people, ‘It’s not just this one animal. This is happening across the country,’” Miller says. “I think that was what was so cool about the work we were able to do with this huge dataset: tie together what rehabbers across the country are seeing and validate it. We were able to find a lot of these trends for the big picture of how humans are impacting wildlife.”

The Major Threats to Wildlife

Miller started in BU’s Urban Biogeoscience and Environmental Health (BU URBAN) program in 2018. Funded by the National Science Foundation, BU URBAN trains PhD students in biogeoscience, environmental health, and statistics, giving them the foundation to enter careers in academia, government agencies, NGOs, and the private sector.

The program requires internships, so in summer 2019, Miller began contacting wildlife centers, which varied in size from those rescuing a few hundred animals a year to groups helping tens of thousands. Miller asked what trends they noticed and what questions they would like answered through any report. 

“I had phone calls with rehabbers where they would have to jump off because they had a baby squirrel they had to go feed, or one time someone had a porcupine autopsy they had to get back to,” Miller says. “People were so generous with their time and of their data, and so enthusiastic about this whole project.”

Until recently, most wildlife rehab records existed only in binders and file cabinets, which made them inaccessible to researchers. But slowly, over the last decade or so, centers have started to digitize their documents, thanks in part to software such as the Wildlife Center of Virginia’s WILD-ONe patient database system for wildlife rehabilitators. WILD-ONe was formed, in part, to help identify wildlife diseases and pathogens—such as West Nile virus or avian flu—that might impact human and livestock health. The software was the biggest data source for Miller’s paper; two of the paper’s coauthors, Karra Pierce and Edward Clark, Jr., work at the Wildlife Center of Virginia.

“This was a gigantic dataset, with more than 600,000 observations,” says Richard Primack, a BU College of Arts & Sciences professor of biology, who was Miller’s PhD advisor and a coauthor on the paper. Primack says he encourages all of his students to consider what questions they want their data to address. In Miller’s case, the big question was, “What are the major threats to wildlife?”

The data revealed that 40 percent of animals were sent to rehab centers because of injuries classified under the “human disturbances” category. These included vehicle accidents, building collisions, and fishing incidents. “Forty percent of the animals showing up to wildlife rehab centers, largely because of human activity that has negatively impacted them?” Miller asks incredulously. “We need to ask how we can change our policies and behaviors to impact animals less.”

Seasonally speaking, the researchers found vehicle collisions were highest from May to July and disproportionately affected reptiles. Pesticide poisonings increased in the spring, summer, and early fall, a time of more agricultural and construction activity. Lead poisonings (most common in animals like bald eagles) tended to be seen in the winter, after hunting season. Many hunters still use lead ammunition when deer hunting, which will then poison scavengers like bald eagles and vultures when they go in for a snack on a carcass.

Through their discussions, many rehabbers told Miller they knew they weren’t catching all cases of lead and pesticide poisoning since the testing is so expensive and they can’t send every suspected case out.

The researchers also found more animals arrived at rehab centers the week after extreme weather events than the week before—following hurricanes and floods in southern Florida, for example. They have also seen more animals admitted after big storms in recent years, “possibly due to the increasing intensity and frequency of extreme weather events,” the study says.

“We are seeing the impacts of these climate change–driven extreme weather effects on animals,” Miller says. “So, should we be thinking about that in terms of disaster and response plans? Do we need to boost state funding to centers to be able to care for animals after these big events?”

About one-third of the animals brought into wildlife rehab centers are eventually released back into the wild, though this number varies significantly among species. “For example, pelicans are injured but then are often released [68 percent], whereas bald eagles have a very low chance of being released [20 percent],” Primack says. “This presents a very interesting question of why the threats to wildlife are so different between these two groups of large birds.”

Recommending New Policy, Based on the Data

The team hopes their study can be used by wildlife rehab centers when they apply for grants and funding, and can convince communities to make some fairly easy changes to protect animals. Wildlife underpasses and overpasses across roads can help deer and turtles cross a highway safely (also reducing car accidents), adding decals and other patterns to windows can save birds, and educating the public on how to phase out lead fishing gear and hunting ammunition can cut down on poisoning in scavengers. Some states also have lead ammunition buy-back programs, Miller says. These changes will help humans too. Deer-car collisions are not only expensive to fix, but can also be deadly for all parties.

After graduating from BU in May 2022, Miller started work as a policy research specialist at the University of Virginia’s Repair Lab, studying and developing policy solutions to coal dust pollution that affects predominantly Black communities near coal export terminals in coastal Virginia. “Tara is now focused on applied work helping people, using many of the skills acquired as a grad student while investigating wildlife health on a continental scale,” Primack says. “It’s really pretty fantastic.”

This work was supported by the National Science Foundation Research Traineeship–funded Boston University graduate program in Urban Biogeoscience and Environmental Health.