• Ruqayya Khan

The battiest of them all

Urban areas across the U.S. and Canada are often dominated by big brown bats, Eptesicus fuscus. These bats represent one of the very few US/Canada species with a distribution that spans the entire US. They are everywhere!

Big brown bat, photo by Paul Cryan.

The “big brown bat” name really does not capture how amazing this commensal bat can be. It does truthfully reflect one thing though: the bats are indeed bigger than most of the other hibernating North American bats of the ultra-diverse bat family Vespertilionidae, with over 400 species [1]!

In the spring and early summer, the females of the species come out of the wild to form temporary maternity colonies for giving birth to the young. Historically, maternity colonies were probably in tree cavities. In modern, human-dominated landscapes, however, many maternity colonies are in buildings and residential properties.

In the winter, the bats go into hibernation. Importantly, the big brown bat hibernates in smaller groups, and in colder and drier conditions than many of the other North American bats. This behavior likely contributes to their ability to survive the white-nose syndrome, a disease that has been decimating other hibernating bats on the continent. (By contrast, read about the little brown bat Myotis lucifugus and its struggle with the white-nose in one of our previous blog post.)

As an insectivore, big brown bats play a crucial role in maintaining bug populations and are an agriculturally valuable species. These bats are often sought out by corn farmers, as they consume cucumber beetles that are capable of destroying an entire season’s crop [2]. Farmers can build bat boxes stable place to roost, encouraging these bats to move in and provide their services. Instructions on how to construct your own bat box can be found on the National Wildlife Federation’s website.

Because they are so willing to share buildings with us, big brown bats have historically been a species that scientists study a lot. For example, one of the closest looks yet into the details of a hibernating bat’s life was the Fort Collins Bat Project, a 5-year study that scientists from USGS, Colorado State University, and CDC collaborated on from about 2001-2006 to study population dynamics of big brown bats in Fort Collins, CO, and the dynamics of rabies viruses circulating in this population. The findings of that study were many and profound, but one of the coolest aspects was that they marked over 4,000 individual big brown bats with passive integrated transponder (PIT) tags and followed their movements and gave them occasional health check-ups over the years of the project. Read this paper for a summary of the project!

Today, we share the chromosome length assembly of the big brown bat based on the EptFus1.0 draft generated by the Broad Institute. In order to do the upgrade, we generated a Hi-C library using a sample donated by one of the tagged bats from the Fort Collins Bat Project. (Sample collected under Colorado Parks and Wildlife Scientific Collection License 14TR2010 issued to Paul Cryan. Protocols approved by the Institutional Animal Care and Use Committee of the USGS Fort Collins Science Center (FORT-IACUC #2014-08).


The bat, who was at least 10 years old when she died, had successfully birthed a pup during the four years of the study when the scientists were regularly checking in on her health. Like a good proportion of the big brown bats in Fort Collins, they detected rabies virus neutralizing antibodies in her blood in multiple years, so she was presumably immune!

This is the third Vespertilionidae bat family genome assembly at the DNA Zoo, after the little brown bat Myotis lucifigus and the North American long-eared bat Myotis septentrionalis. See how the genome assemblies relate to each other below!

DNA Zoo Vespertilionidae whole genome alignments: bit brown bat (EptFul1.0_HiC); little brown bat (Myoluc2.0_HiC) and North American long-eared bat (myse_ont_racon_pilon_HiC).

Blot post by Ruqayya Khan & Olga Dudchenko

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