Humans have strained relationships with a lot of animals and that can have many negative consequences — even when it comes to animals that seemingly only hurt humans.

A new paper in the journal Nature Ecology & Evolution investigates the role predator and scavenger species play in the human world. The roles are complicated, with lots of give and take. For example, while cougars may attack livestock and cause economic losses, they also prey upon deer and thus could reduce the number of vehicle crashes that involve deer, potentially saving human lives. Scavengers like vultures offer waste disposal services when they feed on the dead bodies of other animals.

“Many native carnivores that live in and around human habitation are declining at an unprecedented rate — spelling bad news for humans who indirectly rely on them for a variety of beneficial services,” the Wildlife Conservation Society said in a statement.

The society worked with the University of Queensland on the research.

In addition to the work of cougars and vultures, there are bats — animals that many people fear. Bats stop insects from destroying certain crops, according to the review, which has benefits for farmers.

Photo: Julie Larsen Maher/WCS

“Predators and scavengers are frequently persecuted for their negative effects on property, livestock and human life,” the study notes. “Identifying, evaluating and communicating the benefits provided by species that are often considered problem animals is an important step for establishing tolerance in these shared spaces.”

In some places where humans perceive predators or scavengers to be a threat — to themselves, livestock or crops — they might kill the animals. But if those animals were to suffer large population losses or even extinction, it might affect the ecosystem in unforeseen ways.

“There is a lot about of research highlighting the negative impacts of predators and scavengers, and we are only just now beginning to understand the potentially irreplaceable services that these animals can provide human societies,” paper co-author James Watson said in the WCS statement. “We must understand that if we lose these animals, humanity loses. The more we understand the benefits these species provide, the better we can identify those situations that lead to win-wins for both species and societies, an outcome that could enhance the protection of one Earth’s imperiled species.”