Humans are often to blame for illnesses and injuries that land animals in wildlife rehabilitation centers, a recent analysis in the journal Biological Conservation suggests. The broad-reaching study looked at animals housed in wildlife centers in the United States and Canada — and highlighted threats that humans present to over 1,000 species.

The study reviewed a data set of 674,320 digitized records from 94 wildlife centers throughout North America running from 1975 to 2019. The records contain information about all kinds of animals, but Eastern cottontail rabbits, Eastern gray squirrels, Virginia opossums, American robins and raccoons were most frequently admitted to wildlife rehab centers, although species varied by region.

Researchers pinpointed several leading reasons for animal injuries, including human disturbances such as collisions with vehicles, injuries and illness; predators; and poisonous substances.

Nearly 40 percent of all cases were caused by humans, and vehicle collisions were the main cause of injury, affecting 12 percent of animals admitted, the study says. Other dangers included fishing, collisions with buildings or windows, and run-ins with domesticated dogs and cats, researchers found. Reptiles suffered the highest proportion of human-caused rehab admissions.

Overall, human activities have “a large, negative impact on wildlife,” the researchers concluded.

Just 32.5 percent of animals ended up being released back into the wild, and about 9 percent were transferred to another facility or otherwise being treated; the rest died or were euthanized. More mammals were eventually released than any other type of animal.

Humans’ presence could be felt throughout the study, even in cases in which they did not directly injure the animals.

Lead poisoning and the effects of human-caused climate change also put animals in danger, with heat stress, die-offs and other issues linked to the extreme weather thought to be fueled by human activity. These factors affected different animals in different ways: For example, bald eagles were dramatically more likely to be admitted for lead poisoning than other animals, and red-tailed hawks bore the brunt of pesticide exposure.

The researchers called for wildlife centers across the continent to standardize their systems to enable more research. Overall, they write, such records are “an excellent source of data for identifying threats to wildlife health and establishing management and conservation priorities and responses.”