Animals meet more often when they live closer to humans

Multi-species interactions captured on camera traps, like this Wisconsin Snapshot image of a pair of low-antagonism turkeys and deer, are few and far between. Thus, the UW-Madison researchers analyzed the time between the appearances of the species on the Wisconsin Snapshot cameras to study the frequency of their interactions near human activity. Credit: Wisconsin DNR/Wisconsin Snapshot

Human presence and influence on landscapes changes the way other animals interact by bringing them closer together more frequently than occurs in wilder places.

Researchers at the University of Wisconsin-Madison used photos from over 2,000 camera traps in the Wisconsin Department of Natural Resources Snapshot Wisconsin program to determine proximity in space and time to animals of various species. The time between different species appearing on cameras was significantly shorter in areas closer to human disturbance, meaning they are likely to interact more often when people are nearby.

The findings published today in the Proceedings of the National Academy of Sciences, support the compression hypothesis – the idea that the encroachment of human activity compresses space and time shared by animals, leaving them closer and more likely to meet. Another school of thought, the expansion hypothesis, predicts fewer interactions because certain types of animals (like predators) are disproportionately moved by humans.

“Compression works like a house party,” says Neil Gilbert, lead author of the study, which he conducted while completing his doctorate in forest and wildlife ecology at UW-Madison this year. “The more people you cram into a party, the less wiggle room you have and the more likely someone will step on your toes.”

Although not all species are troubled by human activity– squirrels and deer in particular thrive near people – one thing is clear: animals that want to avoid human contact have to settle for less wiggle room.

“We’ve converted over 40% of the Earth’s land surface to human uses, urbanized landscapes, agricultural landscapes,” says Ben Zuckerberg, study co-author and UW-professor of forest and wildlife ecology. Madison. “We can consider that to be a pretty significant form of habitat loss for many species.”

How this loss affects animal behavior and relationships can be difficult to study. Mark individual animals or small groups Trackers offer too narrow a view to study interactions at the community level. But Snapshot Wisconsin, a community-based science initiative that recruits volunteers to place camera traps on private and public lands, has thousands of sites across the state, producing millions of photos that enable near-continuous monitoring of moving animals. in a wide range of landscapes.

“Snapshot Wisconsin supports DNR decision-making, answering important questions about species like elk and deer,” says Jennifer Stenglein, Snapshot Wisconsin research scientist and co-author of the study. “But it can also push the boundaries of theoretical studies when someone like Neil gets creative with this big data set.”

Gilbert pulled nearly 800,000 photos of animals from the Snapshot Wisconsin archive, assigning each of the nearly 2,000 camera locations a rating for the level of human disturbance within a 5-mile radius — plots like those in national forest at the lower end and urban development or intensive agriculture at the upper end – based on NASA satellite imagery.

The researchers also grouped 18 observed species into 74 pairs and sorted them according to the likelihood of an encounter turning violent, from low-antagonism pairs like skunks and rabbits to high-antagonism pairs like deer and coyotes. Next, they measured the time between appearances at individual camera sites by an animal of each member of a pair.

“Temporal separation is our proxy for an encounter,” Gilbert says. “If a camera picks up a squirrel and then a minute later picks up a coyote, those two animals are more likely to interact than if it was like a squirrel and then three weeks later a coyote.”

The pairs in the study had an average of 6.1 days between camera detections in the low-disturbance landscapes, but 4.1 days between detections in the high-disturbance landscapes. Pairs with high antagonism had the longest time between detections on average and pairs with low antagonism the least, but the trend held for each group: the closer they were to human disturbances, the less time between likely interactions.

“It’s a big question in ecology: how does human disturbance affect wildlife? We clearly see that it can alter their interactions,” says Zuckerberg. “The next questions are about the ramifications. Does this lead to changes in disease transmission? Does it alter predation? Does it affect things like deer and vehicle collisions? »

The researchers hope their work will help people understand the general impact they have on changing not just animal numbers and habitat size.

“Even if it’s just in terms of the animals in your garden, your environment, your neighborhood, I hope it will encourage thinking about our impacts as humans on these invisible dimensions of biodiversity,” says Zuckerberg.

More information:
Neil A. Gilbert et al, Human disturbances compress the spatiotemporal niche, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2206339119

Provided by
The University of Wisconsin-Madison

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