Snapshot USA: First-ever nationwide mammal survey now published

UNIVERSITY PARK, Pa. — The results of the first national mammal survey, now publicly available online, provides the framework to answer a variety of questions about wild animal populations and conservation strategies for threatened species. The survey, which involved researchers from across the country including a biologist at Penn State, is made up of data from 1,509 motion-activated camera traps from 110 sites located across all 50 states.

“The data generated from this immense project are invaluable for answering fundamental questions about wild mammal populations,” said Sean Giery, Eberly postdoctoral research scholar at Penn State, who participated in the survey. “But I think the real benefits will come years from now, when we can use these data as a baseline to measure change in the diversity, distribution and abundance of mammals in the United States.”

Unlike birds, which have multiple large-scale monitoring programs, there has been no standard way to monitor mammal populations at a national scale. To address this challenge, a team of more than 150 scientists, led by the North Carolina Museum of Natural Sciences and the Smithsonian Conservation Biology Institute, recently collaborated on the first-ever nationwide wildlife survey called Snapshot USA.

“Remote-triggered cameras — camera traps — have revolutionized wildlife research, especially for mammals that are too wary to observe directly or only come out at night,” said Giery. “These cameras are widely used by hunters, but ecologists also employ them for a range of studies. Now, we can set up motion-triggered cameras for months at a time, learning what animals are present in an area and how abundant they are. Sometimes, we even get a peek at social behaviors or predation. But until now, there just hasn’t been a large-scale effort to coordinate a camera survey like this across the entire U.S.”

For two months in fall 2019, researchers collected more than 166,000 images of 83 different mammal species. White-tailed deer were the most common species detected — 34,000+ times at 1,033 camera sites — followed by eastern gray squirrels and raccoons. Pygmy rabbits, mountain beavers, hog-nosed skunks, and marsh rabbits were among the least-common mammals photographed. Yet, the most broadly detected animal overall was the coyote, which was detected in all 49 continental states — they have not made it to Hawaii yet.

All the data are archived at the Smithsonian Institution’s eMammal database and published as part of a paper appearing June 8 in the journal Ecology, a publication of the Ecological Society of America,

“Our goal was to provide a space for researchers from all 50 states to contribute a subset of their data to a broader initiative to maximize our coverage of the country and better understand drivers of mammal distributions to best inform conservation as rapidly as possible,” said Michael Cove, curator of mammalogy at the North Carolina Museum of Natural Sciences and lead author of the new paper.

Interestingly, according to the researchers, developed areas tended to have the highest overall mammal detections, with three of the top five sites for total mammal activity being urban — Urbana, Illinois; Baltimore, Maryland; and Washington, D.C. This phenomenon has been previously observed in certain urban areas, perhaps due to the presence of food or fewer predators, and the new survey suggests this “urban mammal paradox” is a widespread phenomenon. Additional research could help scientists confirm why this phenomenon occurs.

Notably, a site in southeastern Pennsylvania ranked 7th in the country for highest relative abundance of red foxes and 8th for highest relative abundance of fishers. National ranking of top sites for select mammal species can be found here.

The research collaboration has made their 2019 survey data available online for anyone to use for research. For example, the data from this survey could help scientists evaluate changes in animal populations over time or inform conservation strategies for threatened and endangered species.

“This project involved a remarkable level of cooperation and data sharing that will have to be the standard going forward to adequately monitor our valuable wildlife resources at the national scale,” said William McShea, wildlife ecologist at the Smithsonian Conservation Biology Institute.

The scientists repeated the survey during the fall of 2020, which may provide insights on the effects of the COVID-19 pandemic on wildlife distributions and habitat use. The resulting data will be available when the eMammal database is updated in 2021.