Are Urban Bats the Future?

Urban bats at Congress Bridge in downtown Austin, Texas / Flickr

The plight of the honeybee has been well-documented since the term colony collapse disorder made its way into news headlines about a decade ago. The phenomena fueled public interest in the health of bee populations, ushering in a new generation of bee-keeping enthusiasts. And justifiably so. Pollinators like bees are essential to our nation’s economy and food supply.

Another, albeit less popular, pollinator is also facing a precipitous population decline. Bats are dying at an alarming rate due to an invasive fungal disease that’s wiping out entire species, and the unlikely savior may be one of their own.

Bats pollinate over 500 species of plants around the world, including cocoa and agave — fans of chocolate and tequila, take note. What’s killing them is called White-Nose Syndrome (WNS), a fungal disease that grows on bats’ skin and wakes them up during hibernation. Repeated waking during the hibernation period depletes winter fat storage and causes starvation. The fungus needs high humidity and low temperatures to survive, typical cave-like conditions.

Millions of bats in North America have died from the disease since it was first documented in a cave in New York in 2007. Now, WNS has spread to 30 U.S. states and five Canadian provinces and is reaching the west coast. Last year, a bat in Washington state tested positive for the disease.

“Populations will likely never return to where they were,” said Amanda Bevan, lead for the Organization for Bat Conservation’s Urban Bat Initiative.

Bats in urban areas are less affected by the disease because they tend to hibernate in man-made structures that stay warmer than caves. And migratory species, like the Hoary Bat, do not spend the same amount of time in caves as bats that hibernate, and therefore have limited interaction with the fungus.

With more opportunity and reduced competition, Bevan says, it’s possible that some of these urban and migratory bats could push into the realms of cave and forest-dwelling bats.

“They are what’s going to be the saving grace for white-nose syndrome,” Bevan said. The Evening Bat, for example, more often found in southern regions of the U.S., has recently been discovered in caves in Wisconsin and Michigan where it’s possible it could help rebuild the states’ cave-dwelling bat populations. This is a relatively new, but potentially promising, phenomena that could help bolster species in decline.

Bevan thinks, given current trends suggesting changing behavior, urban bats are likely to become the majority population.

But there is a significant lack of research on the urban bat, and more broadly, trends in bat populations over time. Migratory bats especially are challenging to track because they are hard to catch multiple times. In absence of robust data, it’s difficult to understand movements and patterns across species.

To date, research has focused largely on cave-dwelling bats, but now ecologists seek a better understanding of bat activity in urbanized landscapes. In 2012, researchers from Fordham University published an acoustic monitoring study of bat activity in the Bronx. The report, which was the first of its kind documenting urban bats in the northeast, found five different species at various sites. A subsequent study reported increased bat activity over green roofs, compared to conventional roofs in the Bronx, indicating green roof provide habitat benefits for bats.

Urban gardeners who want to support their fellow urban-dwelling mammal can create habitats like bat houses and supply pollinator-attracting plants. Plants like milkweed and evening primrose attract night pollinators, like moths – a diet staples for bats. Gardeners can also use plants that bloom late in the day, are scented at night, and have a lighter in color. One of the biggest threats to urban bat populations are pesticides, which can affect a bat’s ability to navigate using echolocation.

3 thoughts on “Are Urban Bats the Future?

  1. Stephanie Sheffield 07/02/2017 / 3:01 pm

    It’s great if urban bat species do well, but many cave dwelling species will likely never live in/adapt to urban environments, and it is some of these species that are particularly endangered. Alteration in air flow through caves can drastically alter humidity, temperature and thereby proneness to white nose syndrome. For these cave dwelling species, it is habitat alteration, especially via destruction, degradation or alteration of cave entrances that is a major part of the problem.
    Unfortunately success of urban bats will not prevent extinction of cave bat species.

  2. Stephanie Sheffield 07/02/2017 / 3:03 pm

    Which is not to say that I am not happy for the relative success of these urban species!

  3. Benjamin Vogt 07/12/2017 / 8:23 am

    I have to address your first paragraph. Honey bees are globally stable, unlike the 4,000 native bees species in the U.S. which are superior pollinators. Lots of recent research is showing honey bees out compete native bees for forage, spread diseases, and increase invasive exotic plants. We do not need more honey bee hive keeping to “save the bees,” because this may in fact hurt native bees, which are starting to prefer urban areas where forage is greater than in total fields of monoculture. Saving bees means native plants, hedgerows, less spraying….

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