Myotis grisescens
A.H. Howell, 1909

mI-O-tis gris-es-ens

Kansas State Endangered Species

An adult Gray Myotis from Crawford County. Photo by Travis W. Taggart.
Image © by Greg Sievert.

Myotis grisescens is one of the largest members of the genus Myotis. It has monochromatic gray pelage that is paler on the venter than on the dorsum. The wing membrane attaches to the ankle of the foot rather than to the base of the toes. Claws on the hind feet have a notch. The skull is highly inflated and has distinctive sagittal and lambdoidal crests. Finally, the calcar is not keeled. The dental formula, as in other Myotis, is incisors 2/3, canine 1/1, premolars 3/3, molars 3/3.
Species in Kansas that superficially resemble the gray myotis are Myotis lucifugus, Myotis septentrionalis, and Myotis velifer. The monochromatic gray pelage, wing attachment, and notched claws of the gray bat clearly distinguish it from the first two of these species. The darker color, taller skull, and attachment of the wing membrane distinguishes the gray myotis from the third of these species. 

The winter distribution of Myotis grisescens is limited to relatively cold, humid caves in areas characterized by limestone karst at latitudes less than 39 degrees north. Most Gray Myotis spend the winter in just 6 caves. In summer, this species can be found in warmer caves in the southeastern United States. Together, this distribution includes Oklahoma, Kansas, Missouri, Arkansas, Illinois, Kentucky, Tennessee, Mississippi, Indiana, Alabama, Georgia, Florida, and North Carolina. In Kansas, this bat is known only from Crawford and Cherokee counties in the southeastern corner of the state. All Kansas records likely stem from the one known roost, which is located in the storm sewer beneath the city of Pittsburg.
The earliest record of this species is from a middle Pleistocene local fauna in Maryland. Late Pleistocene fossils "that resemble M. grisescens most closely" have been reported from Georgia, Florida, and West Virginia. 

(, Museum Voucher) (, Observation) (, Literature Record)
Open icons are questionable records; Click on a marker to view details.
  • Occurrence Summary:  
  • 115 Total Records 
  • 78 Museum Vouchers 
  • 37 Other Observations 
Some county occurrences indicated below may be too imprecise to map above.
County Breakdown: County Name (# occurrences):
Cherokee (2); Crawford (113);

Natural History:
The Gray Myotis typically is cavernicolous, migrating between summer and winter caves. It also is highly gregarious, forming colonies that may number in the hundreds of thousands of individuals. In the past, the Gray Myotis may have been among the most abundant bats in North America. Today, this species is considered endangered, primarily because of disturbance of colonies by cavers and scientists. We now know how sensitive this species is to disturbance of colonies, and gates placed at the entrances to caves (to restrict access by humans) have resulted in increased populations of this bat. During summer, gray bats prefer warm caves fpr rearing young, whereas in winter they prefer cool caves for hibernation. The two sorts of caves may be near each other or may be separated as much as 250 kilometers. In summer caves, adult females congregate in maternity clusters to give birth and rear their young. The males and subadults during this period live in other caves, or at least apart from the maternity group in the same cave. It is at this time of year especially that disturbance of caves causes mortality in young bats. During winter, when Gray Myotis are in hibernation, interruption of the delicate environmental balance by closing cave entrances, forming new entrances, or arousing the hibernating bats, may cause death to thousands of these bats. Many of the bats that occur in the storm sewer beneath Pittsburg, Kansas, hibernate in a cave in southwestern Missouri.
Adults may attain the following dimensions: total length 88-107 mm; length of tail 32-45 mm; length of hind foot 9-13 mm; length of ear 12-16 mm; weight 8-16 g. The oldest known individual of this species was more than 16 years old when last captured. Average longevity is much shorter because of the high rate of juvenile mortality.
The food of the gray myotis is mainly flying insects, especially mayflies but also flies, beetles, moths, and other insects, captured over water. Bodies of water suitable for foraging near maternity caves are essential for this species.
Predators on gray myotis include house cats, snakes, owls, opossums, and raccoons. In Missouri, dead juveniles found beneath roosts had lethal concentrations of the insecticide Dieldrin in their brains. Banding data suggest that young bats have a high rate of mortality when migrating between summer and winter roosts. However, disturbance of bats in their roosts likely is the most important source of mortality in this species.
The gray myotis breeds in the autumn, and females store the sperm during hibernation. A single egg is fertilized in the spring when it is released from the ovary, sperm being present in the uterus throughout the winter. Females subsequently migrate to warmer caves, where they produce a single young in May or June. Juveniles nurse until they become volant at the age of slightly more than 1 month.

Occurrence Activity:
.In the 1960s, the colony of gray myotis in the storm sewer beneath Pittsburg, Kansas, contained an estimated 5000 to 6000 bats. By the 1980s, the number of bats in the colony had decreased to about 2400. To avoid disturbing the colony, the number of bats has not been determined since that time. Scientists, students, and citizens are urged to stay out of the storm sewer. Rabies and histoplasmosis have been documented in this species.
Myotis grisescens is monotypic in that no subspecies have been named.

1961 Long, C. A. First record of the gray bat in Kansas. J. Mamm., 42:97-98. ():
1964 Hays, H. A., and D. C. Bingman A colony of gray bats in southeastern Kansas. J. Mamm., 45:150. ():
1967 Jones, J. K. Jr., E. D. Fleharty, and P. B. Dunnigan The distributional status of bats in Kansas. Univ. Kansas Mus. Nat. Hist. Misc. Publ., 46:1-33. ():
1995 Decher, J., and J. R. Choate Myotis grisescens Mammalian Species 510():1-7
1996 Choate, J. R., and J. Decher Critical habitat of the gray bat, Myotis grisescens, in Kansas Pages 209-216 in Contributions in Mammalogy: A Memorial Volume Honoring Dr. J. Knox Jones, Jr. Museum of Texas Tech University, Lubbock, TX. pp.
1999 Wilson, D. E., and S. Ruff Smithsonian Institution Press, Washsington, DC. 1-750pp.
2000 Sparks, D. W., and J. R. Choate Distribution, natural history, conservation status, and biogeography of bats in Kansas Pages 173-228 in Reflections of a Naturalist: Papers Honoring Professor Eugene D. Fleharty Fort Hays State University, Hays, KS. pp.
2000 Sparks, D. W., K. J. Roberts, and C. Jones Vertebrate predators on bats in North America north of Mexico. Pages 229-241 in Reflections of a naturalist: Papers honoring Professor Eugene D. Fleharty. Fort Hays Studies, Special Issue 1, Hays, Kansas. pp.
2008 Timm, R. M., G. R. Pisani, J. R. Choate, N. A. Slade, G. A. Kaufman, and D. W. Kaufman, . pp.
Account Last Updated:
7/13/2017 10:14:28 AM

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