During winter, when there is significant snowfall, wildlife biologist Luanne Johnson begins the hunt for otter trails.
Only in the snow can she easily track the round-toed trails at Sepiessa Point Reservation or the smooth belly slides along the hills of Cranberry Acres. Otherwise, the elusive otter remains mostly a mystery. This winter has been a good one for observations.
But even in those years when snow doesn’t fall and in the warmer seasons, too, Ms. Johnson has another resource from which to seek clues — otter scat. Think CSI by way of Cranberry Acres.
Ms. Johnson, in association with Biodiversity Works, a nonprofit dedicated to wildlife research, monitoring and mentoring, began an otter diet analysis for Martha’s Vineyard in 2010 through a grant from the Edey Foundation, along with donations from Mal Jones and the Nan and Bill Harris Family Foundation. Only one other otter diet study has been completed on the Atlantic Coast, in Newfoundland, Canada.
“Here they are, this keystone species in our watersheds, and we really don’t have any information on them,” Ms. Johnson said. From Chilmark Pond to Herring Creek, Ms. Johnson and fellow biologist Liz Baldwin identified 150 latrines carved by otters along ponds, shrubs and salt marshes. Like a loyal pet owner cleaning up after its dog, the two biologists carefully collected otter scat into plastic bags. Visiting 50 sites regularly, they logged 450 scat samples, which they then sterilized and sifted. With the help of volunteers, the biologists have sorted through and documented the scat sample contents, matching fish scales to species.
Along with deer, otters stand at the top of the Vineyard food chain, chowing down 10 to 15 per cent of their body weight every day in fish, crustaceans, insects and other food.
“They are essentially sampling the ponds and waterways for us,” Ms. Johnson said at the Nature Conservancy, as she helped a volunteer identify a crunchy blue claw crab leg piece found in the scat. “They are telling us what is available for them to hunt and eat, because if otters need to eat that much food, they are not going to waste time and energy on food that isn’t easily accessible.”
In her office at the Nature Conservancy, boxes of sifted scat are stacked against the walls.
Volunteer Judy Klumick carefully unwrapped a coffee filter, and poured the contents onto a blue book. The dried fish scales and crab pieces fell softly like confetti.
“Luanne, you have to be the only person that can turn poop into a party,” said Tom Chase, the Nature Conservancy director of conservation strategies.
“It’s amazing that these people want to come in and pick through otter poop,” Ms. Johnson added. “This work needs special volunteers.”
But the volunteers work diligently. Ms. Klumick smooths out the fish bits, and begins placing the tiny scales onto a microscope slide.
Under the microscope, the fish scales still showed their individual grooves, all uniquely curving like those of a fingerprint. The volunteers recognized the smallest details to differentiate a mummichog from a striped bass, just two of 24 species identified so far.
Though she has yet to analyze the data, Ms. Johnson said the scat collections will present what types of fish and other creatures dominate the ponds, or which are more quiet guests, like the mantis shrimp.
“They have this crazy weapon,” Ms. Johnson said as she held up a skinny claw with sharp teeth-like edges. “The otters dig these guys out of the mud.”
Ms. Johnson expects the scat dissection to be finished by spring, and then the full extent of her analysis can commence.
“We could repeat this study 10 years from now,” Ms. Johnson said. “And if one of these species of fish that the otters eat regularly isn’t showing up in their diet, it would make us wonder if the fish population or availability of different species could be shifting. Or maybe it wouldn’t shift at all.”
“It will give us a snapshot in time of pond fauna.”