Euderma maculatumspotted bat

Geographic Range

The Spotted bat has a patchy distribution, occurring from northern Mexico to British Columbia. They are seldom abundant. Recorded observations extend from the Pacific coast to the Rocky Mountains inland.


Spotted bats have been found foraging in many different habitats, especially in arid or Ponderosa Pine forests, and marshlands. Because of the low frequency of their echolocation calls large open habitat is predicted to be preferred. However, it is believed that the distribution of suitable diurnal roosting sites is cause for the patchy distribution of this species. Spotted Bats roost in the small cracks found in cliffs and stony outcrops. They have been found as high as 3000m above sea level, and even below sea level in the deserts of California.

(Pierson and Rainey 1998; Poche 1981; Watkins 1977)

Physical Description

Total length, 126 mm; tail, 51 mm; hind foot, 12 mm; ear, 47 mm; forearm 48.51 mm. The Spotted bat is so named for its three white spots located over each shoulder and on the rump. The surrounding dorsal fur is black while the ventral fur is light with dark underfur. The face is black and the ears and wings are pale.

  • Range mass
    16 to 20 g
    0.56 to 0.70 oz


The female gives birth to one young weighing 20% of her body weight usually around June. Young do not have the spots of the adults, nor fully developed ears at birth. Juveniles have been caught in mist nets in July. Lactating females have been caught as late as August.

(Watkins 1977)

  • Range number of offspring
    1 to 1


Very little is known about this species. It was once thought to be rare In the 100 years from the time of its discovery to 1990 only 14 individuals, for example, were collected in California. Since then the number of locations where spotted bats have been found in that state has tripled, and their range is now known to extend from Montana south to central Mexico, including in western US into arid parts of Nevada, Wyoming, Colorado, and Utah that were previously unrecognized. While the distribution is very patchy over this range, the species may be locally common. Typically at a given site usually only one is caught per night, and individuals are well dispersed, separated by distances of 750-1000m of each other. They use vocalizations to communicate with neighbors. There is at least one recorded account of an apparent territorial dispute involving vocalization and direct contact. Only in one study has this species been seen foraging in groups.

In most studies these bats forage no more than 10 km from their diurnal roost, and seem to forage constantly. Individuals fly in elliptical patterns from their roosting sites while foraging. However there is one recorded case of a lactating female flying 35.8 km straight from her diurnal roost around 23:00 h to a foraging site, roosting there for part of the night (0100 to 0330 h), and then flying back to the cliff day roost. Other bats at the same location followed that nightly pattern. This behavior could be the compromise these bats make between suitable diurnal roosting sites, and foraging sites. This species seems to be roost faithful; they return to the same diurnal roost every night in the summer. In the Autumn their behavior becomes less predictable.

Foraging behavior does not seem affected by amount of moonlight at night, in contrast to the foraging behavior of other bat species.

In addition to the nightly migration to foraging sites, these bats might have a seasonal elevation migration from Ponderosa pine high elevation habitats in June and July to lower elevations in August.

(Leonard and Fenton 1983, 1984; Navo et al. 1992; Perry et al. 1997; Pierson and Rainey 1998; Poche 1981; Storz 1995; Woodsworth et al. 1981)

Communication and Perception

Food Habits

Like most Microchiroptera, the Spotted bat is an echolocator, but uses very low frequencies to locate prey (9-12kHz). These frequencies limit the Spotted bat to catching large flying insects, apparently specializing on large moths that cannot detect echolocation calls of such low frequencies. Insects seem to be caught in the air at a rate of about one every 45 seconds, and most recorded foraging behavior occurred from 11 pm to 3 am.

(Wai-ping and Fenton 1989; Watkins 1977).

Economic Importance for Humans: Positive

Unknown, but as a specialist on moths they might be important in controlling specific moth populations

Economic Importance for Humans: Negative


Conservation Status

Very little is known about the distribution of the population of this bat. The lack of natural history data places it in class 2, requiring more information. Because the Spotted Bat seems to forage in various habitats, conservation of diurnal roosts, rocky cliffs that have snug cracks for roosting, seem to be the best way to protect this species. However large open foraging sights, where their echolocation is most effective, are important to the conservation of this species, as well as the availability of large moths as prey.

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Euderma maculatum mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America. (Cryan, 2010; National Park Service, Wildlife Health Center, 2010)


Sofia Hussain (author), University of California, Berkeley, James Patton (editor), University of California, Berkeley.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.


uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having the capacity to move from one place to another.


This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Berna, H. 1990. Seven bat species from the Kaibab Plateau, Arizona, with a new record of Euderma maculatum.. The Southwestern Naturalist, 35 (3): 354-356.

Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at

Fenton, M., D. Tennant, J. Wyszecki. 1987. Using echolocation calls to measure the distribution of bats: the case of Euderma maculatum. Journal of Mammalogy, 68: 142-144.

Fullard, J., J. Dawson. 1997. The Echolocation calls of the Spotted Bat Eudermal maculatum are relatively inaudible to moths. The Journal of Expiermental Biology, 200: 129-137.

Leonard, M., M. Fenton. 1984. Echolocation calls of Euderma maculatus (Vespertilionidae): use in orientation and communication.. Journal of Mammalogy, 65: 122-126.

Leonard, M., M. Fenton. 1983. Habitat use by spotted bats (Euderma maculatum, Chriroptera: Vespertilionidae): roosting and foraging behavior.. Canadian Journal of Zoology, 61: 1487-1491.

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at

Navo, K., J. Gore, G. Skiba. 1992. Observations of the Spotted Bat, Euderma maculatum in northwest Colorado. Journal of Mammalogy, 73 (3): 547-551.

Nowak, R. 1991. Walker's Mammals of the World, Vol. 1. Baltimore: The Johns Hopkins University Press.

Perry, T., P. Cryan, S. Davenport, M. Bogan. 1997. New locality for Euderma maculatum (Chiroptera: Vespertilionidae) in New Mexico.. Southwestern Naturalist, 42: 99-101.

Pierson, E., W. Rainey. 1998. Distribution of the Spotted Bat, Euderma maculatum, in California. Journal of Mammalogy, 79 (4): 1296-1305.

Poche, R. 1981. Ecology of the spotted bat (Euderma maculatum) in southwest Utah.. Utah Division Wildlife Resources, 81-1: 1-63..

Rabe, M. 1998. Long foraging distance for a Spotted Bat, (Euderma maculatum) in Northern Arizona. Southwestern Naturalist, 43 (2): 266-269.

Storz, J. 1995. Local distribution and foraging behavior of the spotted bat, Euderma maculatum in northwestern Colorado and adjacent Utah,. Great Basin Naturalist, 55: 78-83.

Wai-Ping, V., M. Fenton. 1989. Ecology of Spotted Bat, (Euderma maculatum,) Roosting and Foraging Behavior,. Journal of Mammalogy, 70 (3): 617-622.

Watkins, L. 1977. Euderma maculatum. Mammalian Species, 77: 1-4.

Woodsworth, G., G. Bell, M. Fenton. 1981. Observations of the echolocation, feeding behavior, and habitat use of Euderma maculatum (Chiroptera: Vespertilionidae) in southcentral British Columbia.. Canadian Journal of Zoology, 59: 1099-1102..