Before wildlife biologist Mike Bottini started his 2008 survey to measure the distribution of river otters on Long Island, there was little information on the furry mammal and whether it inhabited the island at all. Now, with supporting data from the completion of his study, he says the species, Lontra canadensis, is making a comeback.
The exact number of otters is still unknown, but in “The Natural Recolonization of Long Island, New York by the River Otter,” Mr. Bottini reported 77 confirmed latrine sites – areas where otters leave scat and scent – in 2018 compared to 22 in 2008.
“It was a pleasant surprise to see that the adaptable and fairly intelligent animal is actually doing quite well,” Mr. Bottini said in an interview. “That’s also a testament to the work that the conservation community has done.” He noted that open space protection and designating local estuaries – such as Peconic Estuary – as areas of national significance are important methods for protecting water quality and aquatic habitats.
Much of the river otter population initially disappeared from Long Island and New York State during the fur trade era centuries ago, as the quality of the species’ dense fur was in high demand. By the 1800s, Mr. Bottini said the river otter was thought to be wiped out from Long Island, and by the 1900s, nonexistent in the rest of the state outside of the Adirondacks.
The enactment of conservation laws and a moratorium on hunting and trapping otters in the mid-1900s, as well as a reintroduction program, helped encourage the growing population again – but information on whether river otters had made their way back to Long Island was still unknown at the time. In the last survey of Long Island river otters in the 1960s, Mr. Bottini’s report notes that naturalist Paul Connor indicated that there were still no otters on the island.
But otters are good swimmers. In the 1990s, they began to find suitable habitat in the Oyster Bay area, making their way over from Connecticut and Westchester County, Mr. Bottini explained.
“Once they got a foothold on the North Shore of Nassau County, they slowly expanded eastward where there was another good habitat,” Mr. Bottini said. “A decade after the survey documenting where they were, I was able to show that they expanded their range – the whole North Shore from Nassau to Orient Point is occupied.”
“Slowly, but surely, they seem to be doing pretty well and I think it’s emblematic of the fact that natural systems can recover if you let them,” said Bob DeLuca, President and CEO of Group for the East End, an environmental advocacy organization. The organization was also one of the funders for Mr. Bottini’s 2018 fieldwork and report preparation.
In fact, since the completion of the 2018 survey, Mr. Bottini has documented river otters moving further south in the Long Pond Greenbelt, and he expects that they will colonize the South Shore in the next decade, including Sagg Pond, which contains their favorite prey: blue crab.
The increasing development of Long Island – which brings with it traffic concerns that can endanger animals – has not inhibited the otters’ recolonization of the land, Mr. Bottini said. Nor has the overall rise in global temperatures because the species has a tolerance for withstanding temperature changes.
“Otters have a very large range of threshold; fish, as a generalization, have a lower tolerance to wide fluctuations in temperature,” Mr. Bottini said, noting that rising temperatures could instead impact otters’ selection of prey.
“As the world changes and as we change the world, there are certain things that seem to be able to live with us better than other things,” Mr. DeLuca said.
The river otter appears to be one of them, as it is an adaptable species. They will eat whatever is easiest to catch. “Name a fish and the otter will eat it,” Mr. Bottini said, adding that they won’t spend energy going after fast-swimming fish like trout but perhaps will catch slower-moving fish like sunfish instead. “I can definitely say, based on the study, they are doing quite well – and on their own.”
After attending the 14thInternational Otter Congress in the Tangjiahe National Nature Reserve in China in April, Mr. Bottini said he has an idea that could help him measure the number of otters living on Long Island. If he chooses a watershed and collects scat samples over a period of time, a DNA test could identify the number of otters living in that home range. Based on that number and the linear miles of shoreline habitat of the home range, Mr. Bottini thinks he can come up with an estimate for the otter population on Long Island.
“There’s still a lot of excellent habitat for otters on Long Island that hasn’t been colonized,” Mr. Bottini said. “I expect that we will see the continuing trend of the otters filling those holes in the next decade.”