Sweet Auburn: The Magazine of the Friends A Landscape of Remembrance and Reflection - Page 7

sweet auburn | 2020 volume i Let’s meet Mount Auburn’s bats! O n a hot, humid August evening, a Big Brown Bat woke up, stretched its wings, and began to circle Halcyon Lake as the sun slipped below the horizon. The bat swooped back and forth across the water, sending echolocation calls out in search of prey. As the evening wore on and Halcyon yielded diminishing returns, the bat made its way across Fountain Avenue and up to the trees along Indian Ridge Path, chittering an alarm call as it narrowly avoided the clutches of an Eastern Screech Owl out in search of its own prey. After catching its breath and taking a careful look around, the determined bat zigged and zagged across Indian Ridge, around the corner of Oxalis Path, past the Gardner Mausoleum, and through a gap in the dawn redwoods out over Auburn Lake to continue its insect foraging. That’s one of the typical patterns that a bat survey— carried out jointly by Mount Auburn and Lesley University, now in its third year—has shown us: bats begin their evenings at Halcyon Lake, and as the night goes on, use the vegetation cover on Indian Ridge to make their way to Auburn Lake, where they continue feeding. Massachusetts is home to nine species of bats, four of which have been confirmed through visual and/or acoustic documentation at Mount Auburn. Like birds, bat populations have suffered declines over the decades due to pesticide use and habitat loss. But bats face an additional challenge in White Nose Syndrome (WNS), a fungal disease that interferes with a bat’s ability to remain in hibernation throughout the winter and ultimately causes death. The unexpected bat diversity at Mount Auburn—bats had never been studied here before—underscores the importance of initiatives like the upcoming Indian Ridge Habitat Restoration project. Greater plant diversity leads to greater insect diversity, which leads to more food for birds, bats, and everything else that depends on insect life. The most common bat by far at Mount Auburn is the Big Brown Bat (Eptesicus fuscus). This chocolate-colored bat’s body is about the same size as that of an American Goldfinch, with an 11- to 13-inch wingspan. The Big Brown, like all our local bats, eats insects, and lives in a variety of habitats, including trees, caves, and buildings, in which it hibernates over the winter. Compared to other bat species, the Big Brown has a higher recovery rate from WNS. This makes them of particular interest to researchers, who hope by studying their behavior, habitat, and biology to find answers that will help other bat species. The Eastern Red Bat (Lasiurus borealis) is also well represented here. It may be the bat that visitors are most likely to see, as it will sometimes hunt during the day, often over Auburn Lake. Its bright red fur and erratic flight as it chases after insects are eye-catching! The Eastern Red Bat is about the same size as a Big Brown, but its coloration makes it unmistakable. These forest-dwelling bats are seasonal residents at the Cemetery, arriving in the spring alongside migrating birds and spending their summers here, much like a catbird or an oriole. The Hoary Bat (Lasiurus borealis) is also a seasonal visitor, passing through Massachusetts in the spring and fall as it migrates, just like the boreal-breeding warblers. The Hoary Bat is bigger, about the body size of a Black-capped Chickadee. The female is generally larger than the male. This might be because, unlike warblers, only the females migrate in the spring to bear and raise their young in northern forests; the males remain in more southern habitats, waiting for the females to return in the fall with their offspring. Both sexes have the beautiful silver-tipped fur that gives them their frosty name. Finally, the Little Brown Bat (Myotis lucifugus), listed as Endangered in Massachusetts, has been documented in small numbers here. This diminutive species, with a body size comparable to a Ruby-throated Hummingbird, was once the most common bat in the Northeastern United States, but it has been severely affected by WNS, to the point of population collapse. This makes it especially exciting to find them living here at Mount Auburn. Much more research remains to be done, but their survival here points to the exciting potential for urban wildlife refuges like cemeteries to insulate populations of Little Brown Bats and perhaps other species from diseases and infections. See the process of mist-netting, banding and assessing a Big Brown Bat captured at Auburn Lake in June of 2019 by Lesley University researcher Chris Richardson as part of Mount Auburn’s Urban Bat Diversity and Activity Study. https://mountauburn.org/big-brown-bat-at-mount-auburn-cemetery For more information on the bat study, please contact: crichard@bu.edu 5