Some bats are migratory contrarians

        October is one of the busiest months of the year for migration.
        Millions of songbirds that spent the summer breeding in the Northeast – warblers and flycatchers and orioles, for instance – are winging their way southward to Central America, South America or the Caribbean to enjoy the warm climate and to feed on the abundance of insects that are mostly absent during our northern winters. They’re joined by an equal number of their offspring, all of whom are making the dangerous journey for the first time.
        At the same time, geese and ducks and finches and many sparrows are heading southward from the north, destined to spend the winter eating from our bird feeders or carousing in our ponds or along our

Little Brown Bat (Kentucky Fish and Wildlife)

 coastlines. For them, the New England winter is their version of the Tropics. They’re accustomed to chilly winters and adapted to eating seeds or mussels or whatever else we have available in winter.
        Our few migratory butterflies and dragonflies have departed by now, too, in their search for warmer temperatures to the south. Reptiles and amphibians are also on the move, just not nearly as far – mostly to nearby underground lairs or to the muddy bottoms of ponds and streams.
        But strangely enough, one group of animals is going in the opposite direction. Most of our bats are migratory contrarians. October is the time when they are moving northward instead of south, toward caves and mines in Vermont, New Hampshire and the Adirondacks.
        They’re seeking out a very precise environmental condition – high humidity and a temperature that will remain stable a bit above freezing for the next five months. That’s where they’ll hang together from the ceiling, sometimes in large numbers, in a state of inactivity and slow their metabolism so they don’t have to eat or drink for the entire winter. Rhode Island doesn’t have any suitable caves or mines in which bats can hibernate, so most of our bats head to those closest to us, all of which are to the north and northwest.
        These bat caves – officially called hibernacula – are the perfect location for their long winter naps. But because the bulk of the region’s bat populations are all gathered together in a very few sites, it made it easy for an unexpected disease to rapidly spread among them. Bunched together wing to wing, a deadly disease called white nose syndrome was quickly passed from one bat to another – sort of like Covid-19 among party-goers – and over a few short years close to 90 percent of our bats died.
        That’s why we’re seeing far fewer bats now than we did 20 years ago. The one exception is a species called the big brown bat – as opposed to the little brown bat, which used to be the most abundant species in the Northeast. A few big browns have found enough old buildings, underground bunkers and earthen crevices in Rhode Island with adequate enough conditions to keep them home for the winter. Which may be one factor – along with good genes and naturally occurring probiotics – that has allowed them to survive the disease in greater numbers. Their populations only crashed by about 50 percent.
        I wouldn’t want to suggest that the bats that migrated in the opposite direction of all the other wildlife on our continent are like the clumsy Gang That Couldn’t Shoot Straight, but there’s something to be said for the bat that simply chose to stay home. Maybe, by not migrating at all, the big brown bat is the true migratory contrarian. 

This article first appeared in The Independent on Oct. 11, 2020.