Local weasel population hard to assess as national survey finds species in decline – ecoRI News


By TODD McLEISH / ecoRI News contributor

A national study of weasels found across much of the United States found significant declines in all three species assessed, prompting a local biologist to question the status of the animals in Rhode Island.

The to study by scientists from Georgia, North Carolina and New Mexico found an 87-94% drop in the number of minor weasels, long-tailed weasels and short-tailed weasels harvested each year by trappers over the years. Last 60 years.

Although a decline in the popularity of trapping and the low value of weasel skins are partly responsible for the decline in harvests, researchers have still detected a significant decline in populations of the three species.

“Unless you maybe have chickens and are worried that a weasel might eat your chickens, you probably don’t think about these species very often,” said the University’s wildlife ecologist. Clemson, David Jachowski, who led the study. “Even the state agency biologists tasked with tracking down these animals really don’t have a good understanding of what’s going on.”

All three species of weasels are small, nocturnal carnivores that feed primarily on mice, voles, shrews and small birds, often piercing the skulls of their prey with their canines. Weasels prefer dense brush and open woodland habitats, where they seek prey among stone walls, woodpiles and thickets. Due to their secretive nature and cryptic coloring, they are difficult to find and observe.

By evaluating trapper data, museum collections, state statistics, a national camera trapping effort and sightings reported on the web portal naturalist, scientists found that animals were increasingly scarce across much of their range.

“We have this alarming pattern in all of these weasel datasets that are being seen less and less, Jachowski said. “They are most in decline at the southern edges of their ranges, particularly in the southeast. Some regions like New York and the Canadian provinces may still have dense populations in localized areas. “

Jachowski noted that weasel populations in southern New England are likely facing declines similar to those in the rest of the country. He believes, however, that parts of the northeast may still have significant numbers of weasels, especially long-tailed weasels, which are considered the most common of the three species.

Charles Brown, a wildlife biologist in the Rhode Island Department of Environmental Management, who provided data to the national study, said that in his 20 years of monitoring mammal populations in the Ocean State, the only of the three species of weasel he found is the long-tailed weasel.

“I have had a few rare encounters with them over the years and have seen a few road deaths,” he said. “A mammalian survey carried out in the 1950s and early 1960s documented two short-tailed weasels, and these are the only records I have found for the species.”

The smallest weasels are not found within 300 miles of Rhode Island.

Brown has provided 19-20 long-tailed weasel specimens to Harvard University’s Museum of Comparative Zoology over the years from many communities across the continent, including Little Compton, East Providence, Warwick, and South Kingstown. Weasels are not known to inhabit any of the islands in Narragansett Bay.

“It’s hard to say what their status is here,” he said. “Trappers can bring back one or two a year, and some years none, and we don’t have other indexes to watch them because they’re cryptic and we rarely see them. “

Brown said a monitoring program could be developed for weasels in the state using track surveys and camera traps, but because the animals have little economic value and do not cause significant damage, they do not have not been a priority to study.

“In a perfect world, I would definitely try to find a specimen of a short-tailed weasel to see if they are still there, but I have nothing to say about them from a historical point of view,” a- he declared. .

Data from the University of Rhode Island helps provide a current perspective on the species’ distribution. URI scientists recently concluded a five-year bobcat study and the first year of a fisherman study, each using 100 surveillance cameras scattered across the state. Among the 850,000 images collected to date, there are approximately 150 photos of long-tailed weasels.

According to Amy Mayer, who coordinates the studies, images of weasels have been collected from many locations around the state, suggesting the population does not appear to be concentrated in one particular area of ​​Rhode Island.

It is unclear what could be behind the national decline in weasel numbers, although Jachowski and Brown believe the increasing use of rodenticides, which kill many species of weasel prey, could be a factor. A recent study of fishermen collected from remote areas of New Hampshire revealed the presence of rodenticides in the tissues of many animals.

“How that fits into the food chain in these remote areas, we don’t know,” Brown said. “There was a discussion that a lot of people go to summer camps there, and when they close the camp for the season, they bombard it with rodenticides to keep mice out. This is just speculation, but it makes sense.

The weasel decline could also be linked to changes in available habitat, the scientists said. The maturation of forests and the decline of agricultural land have resulted in a reduction in the early successional habitats that animals prefer. Brown also believes that re-establishing populations of hawks and owls, which compete with weasels for mice and voles and which can sometimes kill a weasel, could also be a factor.

Jachowski said the results of his national study led to the formation of what he calls a “weasel task force” to share data and discuss how to monitor animals across the country. Brown is among the state biologists and academic researchers in the group.

“We hope the public will also get involved by reporting their sightings to iNaturalist,” Jachowski said. “We have to see where they persist, then we can determine what habitats they are still found in, what areas, and then do our studies to determine what kind of management may be needed.”

Rhode Island resident and author Todd McLeish runs a wildlife blog.

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