What to many people may seem like a trivial aspect of conservation biology, the ecology of bats using urban environments is actually an emerging and inspiring field of research. As increasing development and urbanization is harming much of our indigenous wildlife and their movement, in surprising ways bats are able to adapt right along with us and readily use our urban environments, seeking new benefits and resources in our modern world. This is especially encouraging in the face of the serious threats bats in the northeastern U.S. are facing – white-nose syndrome, habitat loss and human disturbance.
A mounting group of studies show that bats forage readily in urban environments, taking advantage of clusters of insects drawn to streetlights and seeking untapped sources of food amongst urban parks and green roofs. The generalist big brown bat is found abundantly in many types of urban habitats, as are many other species. However, some species actively avoid urban environments, seeking to forage in “cluttered” habitats with tall trees. This change in urban land cover may decrease overall bat diversity by creating a dichotomy between “urban” bats and forest-foraging bats. Another serious implication of increased urbanization is greater sound pollution and human noise. Studies of the effects of sound interrupting bat foraging yield mixed results, suggesting that bats may differ in their ability to discern anthropogenic noise from predator noise.
Not only do bats forage in urban environments, but they are able to roost in them, too. In the summer months, many bat species form all female maternity colonies where they roost together for about three months, and during that time they give birth. These roosts are traditionally made in tree cavities, but more often these maternity roosts are being established in attics and old buildings. In fact, bats that roost in buildings benefit, giving birth earlier in the season because they are largely protected by predators and thus, spend less energy being vigilant. Unfortunately, many people perceive bats as “pests” and often have outright fear of them due to misconceptions about their life history and myths about their behavior. This often leads to disturbance and eradication of maternity roosts, and in some cases persecution. Public education about the benefits of bats to our functioning ecology is crucial in conserving these threatened animals, and would allow them to utilize our urban habitats.
While no broad federal law exists protecting bat species, the U.S. Fish & Wildlife Service does not recommend killing bats that have entered your home. The only method they approve of is non-lethal exclusion. While that’s a step in the right direction, displacing an entire maternity colony can have serious and devastating effects for the population. However, this is a tricky issue to tackle, primarily because these bats may form roosts in private homes. Will we ever get to the point where we protect active maternity roosts on private properties? (I hope so!) On the bright side, there is some evidence that installing a man-made bat house on the same building as the evicted roost may successfully attract the displaced colony, providing them with a safe and stable place to roost. More research is needed on the best type of bat house and its ideal placement.
Lastly, the most important conservation effort that needs to be made is to change the deep-rooted view of bats from “pests” in the United States to unique and beneficial parts of our ecosystem. This might be most successful by increasing the number of studies that estimate their economic value, particularly to farmers. Money talks, and if that’s one way to protect bats, I’m all for it. (By the way, bats save farmers billions of dollars every year in pest suppression!) Ultimately, a surge of public outreach, education and conservation information may do more to conserve bats than anything else we can do.