Did you know that many bats migrate? Some of them hibernate AND migrate. And migratory bats face extra conservation challenges.
Bats are not birds
Bat migration is similar to its well-studied cousin, bird migration, but there are many important differences. First, migration is very common in birds, but seems to be uncommon in bats. This might be because bats can escape extreme conditions by hibernating, and birds do not. Second, bats also move shorter distances than birds, but there are a few species that move thousands of kilometers each direction. A larger number of bat species travel in the 100-500 km range, often between hibernacula and summer roosts; we call these “regional” migrants.
Regional migrants
In the Midwestern US, some bats use caves for hibernation but move to forests in the summer to have their pups. This includes the endangered Indiana bat (Myotis sodalis) and threatened northern long-eared bat (Myotis septentrionalis). They travel 300 miles or more each year between summer maternity roosts and winter hibernation caves. The map shown here is from a paper describing Indiana bats banded in Michigan during the summer, and then later seen hibernating in locations hundreds of miles to the south. Other regional migrant bats in this area do not use caves. For example, eastern Red bats (Lasiurus borealis) hibernate in trees or even in leaf litter on the ground.
Long distance migrants
Brazilian free-tailed bats Tadarida brasiliensis are an interesting example of long-distance migratory bats. Not all individuals migrate; those in the eastern United States are thought to be sedentary, although this topic has not been recently explored and we have now documented considerable northward and westward range expansion. Long-nosed bats, which are important pollinators, are also long-distance migrants. Without these bats we would not have tequila!
Conservation of migratory bats
Many of these bats are already under severe pressure from an invasive fungal disease called “White-nose Syndrome” which has resulted in up to 100% mortality at affected sites in the eastern US. In addition, wind turbines kill large number of migratory bats each year. So it’s urgent that we have a better understanding of what bats need during migration. One fun way that you can help migratory bats is to purchase bat-friendly tequila. Research shows that if only 5% of agave plants are left to bloom, it would be enough to sustain migration of long-nosed bats!
Questions? Comments? There’s more information in the blog entries below, but please feel free to start a conversation with me on Twitter: Tweet to @batgrrl
