February 26, 2024

The Ways Humans Harm Wildlife: Tracking the Toll

Bald eagle pair along the Lewis and Clark River near Astoria, Oregon. Photo: Jeffrey St.

At hundreds of wildlife rehabilitation centers across the U.S., people can learn about wild animals and birds up close. These sites, which may be run by nonprofits or universities, often feature engaging exhibits, including “ambassador” animals that cannot be released — an owl with a damaged wing, for example, or a fox that was found in kit and has become accustomed to being fed by humans.

What is less visible are the patients – sick and injured wildlife that have been admitted for treatment.

Every year, people bring hundreds of thousands of sick and injured wild animals to wildlife rehabilitation centers. Someone might find an injured squirrel on the side of the road or notice a robin in the yard that can’t fly and then call the center to pick up an animal in distress.

We study ecology and biology and have recently used newly digitized records from wildlife rehabilitation centers to identify the human activities that are most harmful to wildlife. In the largest study of its kind, we reviewed 674,320 records, mostly from 2011 to 2019, from 94 centers to paint a comprehensive picture of threats affecting more than 1,000 species across much of the US and Canada.

Our findings, published in the journal Biological Conservation, point to some strategies for reducing harm to wildlife, especially injuries caused by cars.

The Minnesota Wildlife Rehabilitation Center, the largest independent rehabilitation center in the U.S., treats more than 1,000 sick and injured animals annually.

Tracking the toll

Humans are responsible for the deaths and injuries of billions of animals every year. Bats and birds fly into buildings, power lines and wind turbines. Domestic dogs and cats kill birds and yard animals. Development, agriculture and industry alter or destroy wildlife habitats and expose wildlife to toxic substances such as lead and pesticides. Extreme weather events linked to climate change, such as floods and wildfires, can be devastating for wildlife.

Most Americans support the protection of threatened and endangered species and recognize that human activities can harm wildlife. But it’s surprisingly difficult to determine which activities are most harmful to wildlife and identify effective solutions.

Information from wildlife rehabilitation centers in the US can help fill in this picture. When an animal is brought to one of these centers, a rehabilitator assesses its condition, documents the cause of the injury or illness, if it can be determined, and then prepares a treatment plan.

Wildlife rehabilitators may be veterinarians, veterinary technicians, or other employees or volunteers certified by state agencies to treat wildlife. They follow professional codes and standards and sometimes publish research in peer-reviewed journals.

A growing dataset

Until recently, most wildlife rehabilitation records existed only in folders and files. As a result, studies based on these records typically used materials from a single site or focused on a specific species, such as eagles or foxes.

Recently, however, rehabilitation centers have digitized hundreds of thousands of case records. Shareable digital records can improve wildlife conservation and public health.

For example, the Virginia Wildlife Center worked with government agencies and other rehabilitation centers to establish the WILD-ONe database as a tool for evaluating trends in wildlife health. This will be an interesting area of ​​research as more records are digitized and shared.

Map showing the distribution of wildlife centers that provided data for the study.
Locations in the US and Canada where animals were found (blue dots) before being taken to wildlife rehabilitation centers (red stars) included in Miller et al., 2023.
Miller et al., 2023, CC BY-ND

Threats vary by species

Using this dataset, we have explored wildlife health patterns across North America. In our study, we identified the main threats affecting wildlife by region and for iconic and endangered species.

Overall, 12% of animals taken to rehabilitation centers during this period were injured in vehicle collisions – the biggest cause of injuries. For great owls, which are common in the U.S., cars were the most common cause of admission — possibly because owls often forage at the same height as vehicles and may feed on roadkill.

Other threats reflect the habitats and living patterns of various animals. Window collisions were the most common injuries for the big brown bat, another species found in many U.S. habitats. Fishing incidents were the main reason for the admission of the endangered Kemp’s ridley sea turtles, which are found in the Gulf of Mexico and along the Atlantic coast.

Toxic substances and infectious diseases represented only 3.4% of cases, but were important for some species. Bald eagles, for example, were the species most commonly brought to centers with lead poisoning. Eagles and other birds of prey inadvertently consume lead ammunition when they feed on carcasses left in the wild by hunters.

In South Florida, hurricanes and floods have resulted in spikes in the number of animals taken to rehabilitation centers, reflecting the impact of climate-driven extreme weather events on wildlife health.

About a third of the animals in the cases we analyzed were successfully returned to the wild, although this varied greatly between species. For example, 68% of brown pelicans were released, but only 20% of bald eagles. Unfortunately, around 60% of the animals died due to injuries or illnesses, or had to be humanely euthanized because they were unable to recover.

Featured solutions

Our results highlight measures that can help conserve wildlife in the face of these threats. For example, transportation departments can build more wildlife road crossings, such as bridges and underpasses, to help animals avoid being hit by cars.

A large wild cat emerges from an underpass beneath a highway.
A mountain lion uses an underpass to safely cross Route 97 near Bend, Oregon.
CC BY

Wildlife management agencies may prohibit or limit the use of ammunition and fishing gear containing lead to reduce lead poisoning. And governments can incorporate wildlife into disaster management plans to account for increases in wildlife rescues following extreme weather events.

People can also make changes on their own. They can drive slower and pay more attention to wildlife crossing the roads, switch their fishing and hunting gear to lead-free alternatives, and place decals or other visual indicators on windows to reduce bat and bird collisions with windows.

To learn more about the animals in your area and ways to protect them, you can visit or call your local wildlife rehabilitation center. You can also donate to these centers, which we believe do great work and are often underfunded.

The scale of the threats wild animals face may seem overwhelming, but wildlife rehabilitators show that helping one injured animal at a time can identify ways to save many more animal lives.The conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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