Whether it’s a birdfeeder on an apartment terrace or a corn feeder for backyard deer, many people enjoy attracting wildlife with the offer of food.

But experts say doing so can have dangerous consequences for both animals and humans.

Feeding sites bring many different kinds of animals into the same small area, which can turn into a hotbed for disease transmission and parasites, says Jeannine Fleegle, a wildlife biologist for the Pennsylvania State Game Commission.

For instance, scientists suspect a fatal disease affecting deer known as Chronic Wasting Disease is spread by exposure to urine, saliva, and feces—all of which get mixed together when animals congregate at feeders.

“Feed used to attract deer will draw turkeys, squirrels, racoons, opossums, rodents, skunks, and