Humans and landscapes change the way other animals interact by bringing them together more frequently.
The University of Wisconsin–Madison used photos from camera traps in the Wisconsin Department of Natural Resources Snapshot Wisconsin program to determine the proximity in space and time of animals. The time between appearances of different species on cameras is shorter in areas that are close to humans.
The compression hypothesis states that encroaching human activity squeezes the space and time animals share and leaves them closer and more likely to encounter each other. The expansion hypothesis predicts less interactions as some animals are disproportionately displaced by people.
Neil Gilbert, the lead author of the study, said thatpression works like a house party. The more people you crowd into a party, the less elbow room you'll have and the more likely someone is going to step on your toes.
It's clear that animals who want to avoid human contact must make do with less elbow room.
More than 40% of the Earth's land surface has been converted to agriculture. It's a pretty big form of habitat loss for many species.
It can be difficult to study how that loss affects animals. It's too narrow a view to study community level interactions if you tag individual animals or small groups. Snapshot Wisconsin, a community science initiative that recruits volunteers to place camera traps on private and public land, has thousands of sites around the state.
Snapshot Wisconsin supports the Department of Natural Resources' decision-making, answering important questions about deer and elk. It can push the envelope on theoretical studies when someone like Neil is involved.
Gilbert assigned each of the nearly 2,000 camera locations a rating for the level of human activity within 5 kilometers based on NASA satellite imagery.
The researchers sorted the 18 observed species by the likelihood that an encounter would turn violent, from low-antagonism pairs like rabbits to high-antagonism pairs like deer and coyotes. They measured the time between appearances by animals at individual camera sites.
Gilbert says time separation is a proxy for encounters. "If a camera picks up a squirrel, and then a minute later picks up a coyote, it's more likely that those two animals are going to interact than if it was a squirrel and coyote."
The study found that pairs averaged 6.1 days between detections in low-disturbance and high-disturbance landscapes. The average time between detections and low-antagonism pairs was the same as for high-antagonism pairs.
There is a big question about how human activity affects wildlife. It can change their interactions. The next question is about the consequences. Does it change the way diseases are transmitted? Is it possible that it alters predatory behavior? Do you think it's possible to affect deer vehicle crashes?
The researchers hope their work will help people understand the impact they have on the environment.
"If it's just the animals in your backyard, your surroundings, your neighborhood, I hope this encourages thinking about our impacts as humans on these invisible dimensions of biodiversity."
Neil A. Gilbert and his co- authors wrote in the Proceedings of the National Academy of Sciences. 10.1073/pnas.2206339
Journal information: Proceedings of the National Academy of Sciences
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