Minnesota's bats: hanging-on!


In February 2024, Minnesota Biological Survey staff counted the number of bats at a hibernaculum (a winter shelter for bats) in southeast Minnesota. This location has been monitored since 1984 and more recent efforts have focused on documenting the impact of White-nose Syndrome (or WNS) on the overwintering population. This WNS disease, typified by a fungus that grows on hibernating bats, has decimated the four bat species that hibernate in Minnesota. All these species have been found at this site. The fungus that causes this disease was first observed at the site in 2017. At that time, the fungus was obvious on the bodies of stricken bats; a feature of many bat overwintering spots since WNS was first documented in North America in 2006. During the 2024 visit, the fungus was not observed on the bats. This is worth special note. Although the fungus is still present in the hibernaculum, the bats appear to be coping with it.

Total count numbers offer another hopeful sign. From a recorded high number of approximately 1,150 bats pre-WNS, numbers dropped to a low of 98 bats after WNS was detected here. During this year’s count 291 individuals were observed. This included a possible Northern Long-eared Bat (federally endangered and absent from the counts since 2017), as well as encouraging numbers of Tricolored Bats (proposed for federal listing as endangered).

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