Rodents key players in forest health

        When University of Rhode Island teaching professor Christian Floyd brought students in his mammalogy class to a nearby forest in September to set 50 box traps to capture mice and other small mammals, he was surprised the next morning when more than half of the traps contained a live white-footed mouse.
        “I usually expect to catch three or four, and on a good year we’ll get about 12, but you never get 50 percent trap success,” URI’s rodent expert said. “White-footed mouse populations fluctuate in boom and bust years, and this year seems to be a boom year.”
        Floyd speculated that abundant acorns, recent mild winters, and healthy growth of concealing vegetation were probably factors in the unusual numbers of mice captured this year. But whatever the reason for their abundance, healthy mouse populations are a good sign for local forests.

White-footed mouse (iStock)

        A new study by scientists at the University of New Hampshire concluded that small mammals such as mice, voles, shrews, and chipmunks play a vital role in keeping forests healthy by eating and dispersing the spores of mushrooms, truffles, and other fungi to new areas.
        According to Ryan Stephens, the postdoctoral researcher at UNH who led the study, all trees form a mutually beneficial relationship with fungi. Healthy forests are dependent on hundreds of thousands of miles of fungal threads called hyphae that gather water and nutrients and supply it to the trees’ roots. In return, the trees provide the fungi with sugars they produce in their leaves. Without this symbiotic relationship, called mycorrhizae, forests would cease to exist as we know them.
        Different fungal species enhance plant growth and fitness during different seasons and under different environmental conditions, so maintaining diverse fungal communities is vital for forest composition and drought resistance, according to Stephens.
        But fungal diversity declines when trees die because of insect infestations, fires, and timber harvests. That is why the role of small mammals in dispersing mushroom spores is so critical to forest ecology.
        To effectively support healthy forests, Stephens said these animals must scatter spores of the right kind of fungi in sufficient quantities and to appropriate locations where tree seedlings are growing. But not every kind of small mammal disperses all kinds of spores, so it’s imperative that forest managers support a diversity of mammal species in forest ecosystems.
        “By using management strategies that retain downed woody material and existing patches of vegetation, which are important habitat for small mammals, forest managers can help maintain small mammals as important dispersers of mycorrhizal fungi following timber harvesting” and other disturbances, Stephens said. “Ultimately, such practices may help maintain healthy regenerating forests.”
        Distributing mushroom spores isn’t the only important role played by mice and voles in the forest environment. They are also tree planters.
        “Almost all rodents cache food — they have a cache of acorns, seeds, maybe truffles, little bits of mushrooms,” Floyd said. “Our oak forests are probably all planted by rodents. They scurry around and dig holes and bury things.”
        White-footed mice, which Floyd said are the most abundant mammal in Rhode Island, are also voracious consumers of the pupae of gypsy moths.
        “For a mouse, gypsy moth pupae are like little jelly donuts; they’re a delicacy,” he said. “The theory is that when mouse numbers are high, they can regulate gypsy moth populations.”
        Mice, voles, shrews, and chipmunks are also the primary prey of most of the carnivores in the forest, from hawks and owls to foxes, weasels, fishers, and coyotes. These small mammals are a vital link in the food chain between the plant matter they eat and the larger animals that eat them.
        Are these small mammals the most important players in maintaining healthy forests? Probably not. Floyd believes that accolade probably goes to the numerous invertebrates in the soil. But this new research on the dispersal of mushroom spores by mice and voles may move them up a notch in importance.

        This article first appeared in EcoRI.org on November 28, 2021.

Local weasel population difficult to assess as national study finds decline

        A national study of weasels found across much of the United States has revealed significant declines in all three species evaluated, which has a local biologist wondering about the status of the animals in Rhode Island.
        The study by scientists in Georgia, North Carolina, and New Mexico found an 87-94 percent decline in the number of least weasels, long-tailed weasels, and short-tailed weasels harvested annually by trappers over the past 60 years.
        While a drop in the popularity of trapping and the low value of weasel pelts is partially to blame for the declining harvest, the researchers still detected a significant drop in the populations of all three species.
        “Unless you maybe have chickens and you’re worried about a weasel eating your chickens, you probably don’t think about these species very often,” said Clemson University wildlife ecologist David

Long-tailed weasel (iStock)

Jachowski, who led the study. “Even the state agency biologists who are charged with tracking these animals really don’t have a good grasp on what is going on.”
        The three weasel species are small nocturnal carnivores that feed primarily on mice, voles, shrews, and small birds, often by piercing their preys’ skull with their canine teeth. The weasels prefer dense brush and open woodland habitats, where they search for prey among stone walls, wood piles, and thickets. Because of their secretive nature and cryptic coloring, they are difficult to find and observe.
        By assessing trapper data, museum collections, state statistics, a nationwide camera trapping effort, and observations reported on the internet portal iNaturalist, the scientists found the animals to be increasingly rare across most of their range.
        “We have this alarming pattern across all these data sets of weasels being seen less and less,” Jachowski said. “They are most in decline at the southern edges of their ranges, especially the Southeast. Some areas like New York and the Canadian provinces can still have some dense populations in localized areas.”
        Jachowski noted weasel populations in southern New England are likely facing similar declines as the rest of the country. He believes, however, there is the potential for some areas of the Northeast to still have robust numbers of weasels, especially long-tailed weasels, which are considered the most common of the three species.
        Charles Brown, a wildlife biologist at the Rhode Island Department of Environmental Management, who contributed data to the national study, said in his 20 years of monitoring mammal populations in the Ocean State, the only one of the three weasel species he has found is the long-tailed weasel.
        “I’ve had a few infrequent encounters with them over the years and seen a few dead ones on the road,” he said. “A mammal survey done in the 1950s and early ’60s documented two short-tailed weasels, and those are the only records I’ve found for the species.”
        Least weasels are not found within 300 miles of Rhode Island.
        Brown has contributed 19 or 20 long-tailed weasel specimens to the Museum of Comparative Zoology at Harvard University over the years from many mainland communities, including Little Compton, East Providence, Warwick, and South Kingstown. Weasels are not known to inhabit any of the Narragansett Bay islands.
        “It’s hard to say what their status is here,” he said. “Trappers might bring in one or two a year, and some years none, and we don’t have any other indexes to monitor 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 have not been a priority to study.
        “In a perfect world, I’d certainly like to try to find a specimen of a short-tailed weasel to see if they’re still around here, but I have nothing to go on about them from a historic perspective,” he said.
        Data from the University of Rhode Island is helping to provide a current perspective of the species’ distribution. URI scientists recently concluded a five-year study of bobcats and the first year of a study of fishers, each using 100 trail cameras scattered throughout the state. Among the 850,000 images collected so far are about 150 photos of long-tailed weasels.
        According to Amy Mayer, who is coordinating the studies, the weasel images were collected at numerous locations around the state, suggesting the population does not appear to be concentrated in any particular area of Rhode Island.
        It is uncertain what could be causing the national decline in weasel numbers, though Jachowski and Brown believe the increasing use of rodenticides, which kill many weasel prey species, could be one factor. A recent study of fishers collected from remote areas of New Hampshire found the presence of rodenticides in the tissues of many of the animals.
        “How it’s getting into the food chain in these remote areas, we don’t know,” Brown said. “There was some discussion that a lot of people go up there to summer camps, and when they close the camp up for the season, they bomb it with rodenticides to keep the mice out. That’s just speculation, but it makes sense.”
        The decline of weasels may also have to do with changes to available habitat, the scientists said. The maturing of forests and decline of agricultural land has caused a reduction in the early successional habitats the animals prefer. Brown also believes the recovery of hawk and owl populations, which compete with weasels for mice and voles and which may occasionally kill a weasel, could also be a factor.
        Jachowski said the findings from his national study have led to the formation of what he is calling a “weasel working group” to share data and discuss how to monitor the animals around the country. Brown is among the state biologists and academic researchers who are members of the group.
        “We’re hoping the public will become involved, too, by reporting their sightings to iNaturalist,” Jachowski said. “We need to see where they persist, and then we can tease out what habitats they’re still in, what regions, and then do our studies to figure out what kind of management may be needed.”

        This article first appeared on EcoRI.org on November 18, 2021.

Different kinds of phytoplankton respond differently to warming oceans

        Tiny marine plants called phytoplankton are the foundation of most food webs in the ocean, and their productivity drives commercial fisheries, carbon sequestration, and healthy marine ecosystems. But little is known about how they will respond to increasing ocean temperatures resulting from the changing climate. Most climate models assume they will all respond in a similar way.
        But a team of researchers at the University of Rhode Island’s Graduate School of Oceanography, led by former doctoral student Stephanie Anderson, has concluded that different types of phytoplankton will react differently. An examination of how four key groups of phytoplankton will respond to ocean

Phytoplankton (Stephanie Anderson)

temperatures forecast to occur between 2080 and 2100 suggests that their growth rates and distribution patterns will likely be dissimilar, resulting in significant implications for the future composition of marine communities around the globe.
        “Phytoplankton are some of the most diverse organisms on Earth, and they fix roughly as much carbon as all the land plants in the world combined,” said Anderson, now a postdoctoral researcher at the Massachusetts Institute of Technology. “Every other breath you take is generated by phytoplankton. And which ones are present affects which fish can be supported in a given region.”
        Anderson, URI Oceanography Professor Tatiana Rynearson and colleagues from MIT, Scripps Institute of Oceanography and Old Dominion University published the results of their research in the Nov. 5 issue of the journal Nature Communications.
        “This study represents a key contribution to the understanding of how phytoplankton respond to ocean warming,” said Rynearson. “All climate change forecasts of marine ecosystems include a term that reflects how we think phytoplankton growth responds to temperature. In this study we've generated new, more accurate values for the temperature-growth response that better reflect the diversity of phytoplankton in the ocean. These new values can be used in future climate change forecasts, helping them to become more accurate. "
        The researchers compiled temperature-related growth measurements from more than 80 existing research studies on four types of phytoplankton – diatoms, which thrive in high-nutrient regions; cyanobacteria, which dominate in the open ocean where nutrients are low; coccolithophores, which are especially important in the uptake of carbon; and dinoflagellates, which migrate vertically in the water column. They also reviewed the heat tolerance for each group and conducted a simulation of projected temperatures to determine how phytoplankton distribution and growth rates would change in different parts of the world.
        They found that each group has a different tolerance for warming.
        “The coccolithophores will probably face the greatest proportional growth decreases near the equator, which could potentially alter community composition there,” Anderson said. “The cyanobacteria, on the other hand, are expected to face the greatest proportional growth increases at mid-latitudes, and they might expand their range poleward.”
        "We were surprised that our simulations predicted the greatest range shift for the cyanobacteria in the Gulf of Alaska and northeast Pacific Ocean, regions that support rich and abundant fisheries,” Rynearson added. “Importantly, cyanobacteria are not known to be very good fish food."
        The researchers said that all four phytoplankton groups are expected to increase their growth rates in cooler regions, but the degree of increase varies by group.
        “With all the groups, we expect their growth rates to decrease closer to the equator,” Anderson said. “The equator is already the warmest region, so increasing temperatures there might push them to their limits. The temperatures there will exceed the levels they’re comfortable at, which will hinder their growth.”
        Most species can tolerate temperatures greater than those they typically face, the researchers said, but the margin between what they typically face and the level at which they cannot survive decreases the closer they get to the equator.
        “There’s a lot of capacity to handle warming towards the poles, but that capacity drops at the equator,” Anderson said.
        The research team also found that the dinoflagellates had the smallest change in growth rate in response to increasing temperature of all of the groups examined, and they tolerated the widest range of temperatures.
        “They’re metabolic rates are not as likely to be affected by temperature changes as the other groups,” said Anderson. “We hypothesize that it could be due to the fact that they are vertical migrants. Their ability to swim up and down exposes them to more temperatures, potentially enabling them to handle more temperature change.”
        The implications of these results are significant. At the equator, where phytoplankton growth rates are projected to decrease as temperatures increase, the reduced biomass of phytoplankton may support fewer fish and other marine organisms.
        “If you’re a fish and you’re dependent on one type of food and that’s no longer present, you might have to move with your prey to survive,” Anderson said. “This could lead to shifts in food webs regionally.”
        At higher latitudes where growth rates are predicted to increase, the higher biomass of phytoplankton may be able to support a greater number of fish, providing a boost to commercial fisheries.
        The study did not consider other factors that might affect phytoplankton growth rates, like nutrient or light availability, so Anderson said the implications of the study are somewhat speculative. She is now incorporating those additional factors into a new model to see how the results may change.

Bumblebee survey reveals species thought extirpated from Rhode Island

        The results of a survey of bumblebees in Rhode Island conducted by a University of Rhode Island graduate student included one species that had not been seen in more than a decade. But it also confirmed that four other species appear to have disappeared from the state.
        “There had never been a bumblebee survey of Rhode Island – or a statewide survey of any kind of bee – and there are some species in the URI historical insect collection that are no longer found in the state,” said Elizabeth Varkonyi of Cranston, who led the project with URI Professor Steven Alm.

Elizabeth Varkonyi and Julia Vieira

“There used to be 11 species in Rhode Island, but only six of those had been seen since 2014. I wanted to get a better idea if those six were truly the only species found here now. And it turns out that we’ve added a seventh species to the list.”
        Bumblebees are important pollinators of flowers and agricultural crops. Certain crops like tomatoes, peppers and blueberries require a specific kind of pollination called buzz pollination that only a few types of bees, including bumblebees, can do efficiently, Varkonyi said. During buzz pollination, bumblebees vibrate their flight muscles when they land on a flower, and that vibration causes the plants to release their pollen.
        With the assistance of fellow URI graduate students Casey Johnson and Julia Vieira, Varkonyi trapped bumblebees at 54 sites around Rhode Island from 2019 to 2021 and surveyed 48 other sites with abundant flowers to record bumblebees and the flower species they were visiting. Of the 7,096 bumblebees she documented, just two species – the common eastern bumblebee (Bombus impatiens) and the brown belted bumblebee (Bombus grisecollis) – made up 82 percent of the total.
        “Bombus impatiens seems to be dominant in the region, and that could be a factor contributing to our bumblebee decline – competition with this species,” Varkonyi said. “A lot of farmers purchase colonies of this species to pollinate their crops, and they might carry parasites or diseases that could be spread to wild populations of other species.”
        The most notable finding in her survey was the rediscovery of a single specimen of the American bumblebee (Bombus pensylvanicus) in southern Rhode Island, a species being considered for endangered species status and that had not been documented in Rhode Island since 2009. Robin Baranowski, a field botany instructor at URI, was the first to spot the American bumblebee in August 2021.
        “We were really only expecting to find the six species that we knew were here, so we couldn’t believe it when we found that seventh species,” she said.
        Varkonyi also found 23 individuals of the yellow bumblebee (Bombus fervidus), another rare and declining species.
        She did not, however, find any evidence of four other species that used to be found in the state – Bombus affinis, Bombus citrinus, Bombus terricola, and Bombus ternarius. While some of these four species are still found in nearby states, all appear to be declining. Some have shifted their ranges northward, perhaps due to the changing climate.
        “Having a higher diversity of bumblebee species is important because we found that each species has its own floral preferences,” said Varkonyi, who will graduate next August and plans a career involving the management and conservation of habitat for pollinators. “Losing one species can negatively affect the flowers and crops it pollinates.”
        The most common plants that Varkonyi found bumblebees visiting were bee balm, common St. John’s wort, yellow wild indigo and red clover. The newly rediscovered American bumblebee was found visiting bee balm, while the rare yellow bumblebee primarily visited red clover.
        Varkonyi presented the results of her bumblebee survey at the annual meeting of the Entomological Society of America in Denver on Nov. 1, where her research poster won first place in the Systematics, Evolution and Biodiversity category.

Reducing noise has benefits for wildlife - and us

        During a birdwatching trip last month to Costa Rica, I was impressed by how little our enjoyment of the wildlife and natural world was interrupted by human-made noises.
        Nearly everywhere we went – and we visited many parts of the West Virginia-sized country – we were mesmerized by the unimpeded sounds of howler monkeys waking us up each morning, unusual insect noises in the rainforests, and beautiful birdsong everywhere. While hiking and observing hummingbirds, parrots, sloths and all sorts of other amazing creatures, we seldom heard the noise of cars or planes or other signs of human civilization. Not even other people.
        It was a far cry from the experience of most places in the United States, where traffic noise, planes and other abrasive man-made sounds often intrude upon one’s enjoyment of the natural world. As I’ve learned, it’s not just my poor hearing that makes it difficult to listen to birds singing in many places around our region.
        Yet people seeking to enjoy nature aren’t the only ones who are sometimes annoyed by harsh human noises in seemingly wild corners of the country. Many animals are, too. And it may be having negative consequences on their health and safety.
        Many birds and frogs in urban and suburban areas, for example, must sing louder to attract a mate than their relatives in the countryside. Those that don’t increase their volume can have difficulty finding a prospective partner because the soundscape is so cluttered that the animals can’t hear each other calling.
        Whales and dolphins face a similar difficulty. Despite how loud their underwater calls are and the great distances those sounds can travel through water, marine mammals struggle to have their voices heard because of the tremendous increase in shipping, oil and gas exploration, seafloor mining, offshore construction and other industrial uses of the oceans. Even recreational boats and Jet Skis traversing coastal environments are having negative consequences on marine mammals seeking to communicate with their fellow creatures.
          Lots of other marine life, from fish to shrimp and crabs, make sounds in the water to communicate, detect prey, avoid predators or for other purposes, and the abundance of ship noises and other human sounds has been shown to have an impact on their behaviors, too.
        Another example: Owls have evolved particularly refined hearing to be able to detect and capture prey in complete darkness, but that skill erodes as background noise gets louder. One study found that for every 1 decibel increase in background noise, owls are 8 percent less successful in capturing prey. And bats, which use sound to navigate at night, can become disoriented when an area becomes noisier and noisier until they must abandon the area entirely.
        With this in mind, let’s take some steps to reduce noise pollution to improve our enjoyment of the natural world and decrease its impact on local wildlife. There’s not much we can do individually about shipping noises, traffic noise, or airplanes flying overhead, but we can use quieter, non-mechanical tools when performing outdoor maintenance and find quieter ways of enjoying the outdoors.
        The easiest thing we can do, however, is to keep our voices low when walking on trails. Talk like you’re in a museum. Voices travel far in the forest, and for most of us it’s the loud voices when you’re not expecting them that has the greatest negative impact on our enjoyment of nature.
        Your fellow park lovers and nature enthusiasts will appreciate your efforts. And so will the birds, the bats and the bees.

        This article first appeared in The Independent on November 11, 2021.