General Bat Anatomy

Falcon Services, Inc.
Bird & Bat Control
P.O. Box 92
Oakley, CA 94561

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California Bat Species
Likely To Be Encountered In/Around Buildings

Mexican Free-Tailed Bat

Little Brown Bat

Pallid Bat

California Myotis

Mexican Long-Tongued Bat

Long-Legged Myotis

Western Pipistrelle

Mexican Free-Tailed Bat (Tadarida brasiliensis)

is one of the most widely distributed mammalian species in the Western Hemisphere and is the famous bat of the Carlsbad caverns in the Southwest. Maternity roosts occur in bridges, buildings, culverts, hollow trees and caves. The maternity colonies vary in size from 20 individuals to millions. In general, the maternity colonies in California do not reach the remarkable size of the southwestern cave roosts. The largest known colony in California consists of around 200,000 individuals in a cave. Although a year round resident of Northern California, evidence indicates localized migrations, and in other parts of its range migrations can be longer than 1,800 km (Wilkins 1989).  The Mexican free-tailed bat is found in many different habitats from sea level to over 3600 meters. Mating takes place in late February and March and ovulation occurs in March. Gestation is 77 to 82 days and young are typically born in late June or July (Nowak 1991). Single young are most typical and twins are rare. Ninety percent of the diet consists of moths. Foraging is usually at heights of six to 15 meters. T.brasiliensis will commute 50 km to forage and fly at altitudes of 3,000 meters or more (Wilkins 1989).

Little Brown Bat (Myotis lucifugus)

The Little Brown Myotis (commonly called the Little Brown Bat) is one of the most common bats in the U.S. and Canada. Its nitrate-rich guano was sold as fertilizer in the first half of the 20th century. Nursery colonies begin forming in April or May and disperse from late July through October. They may number in the thousands (one observed maternity colony had 6,700 individuals, others have had 4,000). The first two to three days after the young are born, their mothers suckle them constantly, except while foraging. Until they are ready to fly on their own, at about four weeks, the young remain in the roost while the mother hunts for small insects, especially flies and moths. Bats usually do not carry their young in flight. However, if disturbed, the mother may take flight with the young, carrying it crosswise, with the infant’s mouth grasping one teat and its hind legs tucked under the opposite armpit. Besides echolocation clicks, this species produces warning "honks" when on a collision course with other bats during feeding or near roosts. In the fall, these bats may fly several hundred miles to a hibernating site; they often can be seen swarming at cave entrances. From September, October, or early November through March or April, they hibernate in irregular clusters, some tight, some loose. They wake an average of once every two weeks during hibernation and may fly about outdoors on warm winter nights, but without feeding. They store about 1/16 ounce (2 g) of fat as winter sustenance, using nearly three-quarters of it during winter awakenings and emergence. The remainder must sustain them through the winter. The coloration of this species varies from shades of glossy brown above, with tips of hairs burnished brown and buff below. Mating occurs in fall and sometimes again in winter or spring. Sperm remains in females reproductive tract until spring, when eggs are fertilized. 1 young born late May - early July, usually in a building, occasionally in a hollow tree. These bats are found in areas along streams and lakes. Nursery colonies are formed in Summer and are usually found in buildings or other structures.

Pallid Bat (Antrozous pallidus)

Emerging long after dusk and beating its wings more slowly than many bats (only 10 or 11 beats per second), this stately bat is unusual in that it often feeds on the ground. Several have been caught in mousetraps. Its food consists of many large insects, including flightless beetles, crickets, scorpions, and grasshoppers. In captivity, it has captured and consumed lizards. Its several calls include an insect-like buzz; high-pitched dry, rasping, thin double notes; single, clear, resonant high-pitched notes; and clicks. The first two generally are given when the colony is disturbed, the latter two at night in flight. The summer colonies, consisting of from 30 to 100 bats, are unusual in that they include members of both sexes and young. Night roosts, often near day roosts but distinct from them, are commonly used by this species. A skunk-like odor given off by glands on the muzzle is most pronounced when the bat is disturbed. Pallid Bats are presumed to hibernate, but few have been found in winter. Pallid Bats mate on horizontal surfaces or while hanging upside down in fall and perhaps in winter. Maternity colonies form in rock crevices, buildings, and in other man-made structures. 1 or 2 young are usually born in May or June. The female is upright while giving birth, and young are caught in the flight membrane as they emerge.

California Myotis (Myotis californicus)

is common in most habitats throughout its range, which stretches from the Alaskan panhandle to Mexico (Samson 1993). Although this bat is common and can be regularly encountered flying along trails at dusk, it is rarely an abundant species in any one area. Maternity colonies are usually small,  generally less than 10 individuals. Day roosts are in rock crevices, peeling bark, tree hollows, and on buildings (Sampson 1993). These bats are very flexible in their choice of night roosts and will use any natural  or man-made shelter (Nagorsen and Brigham 1993). This bat is non-migratory and undergoes extended torpor during the winter months in most of its California range. It will arouse from torpor to forage during  winter months and has been observed foraging in temperatures as low as -8C (Sampson 1993). This bat usually produces 1 young per year  and has a potential reproductive life span of 15 years. In California,  mating takes place in early spring and young are born in late May and  early June. The California Myotis feeds primarily on moths and flies, with smaller amounts of beetles and bugs. Hunting takes place along edges of vegetation and the canopy, over water, and above open ground (Sampson 1993). These bats emerge in the evening and alternate foraging and roosting through the  night.

Mexican Long-Tongued Bat (Choeronycteris mexicana)

is gray or brownish above and paler below. It has a very long nose and tongue, and large eyes. In roosts, these bats do not cluster, but remain an inch or two apart. Extremely wary and easily disturbed, they are able to hang by one foot in such a way that they can rotate and watch any intruder. The long tongue, tipped by a brush of tiny nipple-like projections, and the lack of lower incisors make it easy for this bat to lap up flower nectar and fruit juices. It also eats insects and pollen, and may pollinate certain plants. Pregnant females separate from males into small groups in early spring, giving birth in June or July. Its range is from extreme southern California, southern Arizona, and extreme southwestern New Mexico. Mexican Long-Tongued Bats in Arizona probably migrate to Mexico for the winter.

Long-Legged Myotis (Myotis volans)

is a Federal Special Concern species. Myotis volans inhabits western North America from Southeast Alaska to Central Mexico. It is found in an elevational range from sea level to 3,770 m. This species is primarily a coniferous forest bat although it may also be found in riparian and desert habitats (Warner and Czaplewski 1984). Maternity colonies can be up to 300 individuals. Maternity roosts are found in buildings, rock crevices, and under exfoliating bark. Males roost singly or in small numbers in rock crevices, buildings and under tree bark. Night roosts are known to be found under bridges, in caves and mines, and in buildings (Nagorsen and Brigham 1993). In the northern portion of their range, M. volans commonly hibernate. It is unknown whether this bat migrates in the portion of its range where winters are less severe. Mating takes place in the fall and sperm is stored over winter. Ovulation and fertilization takes place from March to May and parturition occurs from May to August. There is extensive variation in the timing of reproductive activity in this species. M. volans is known to live 21 years in the wild (Warner and Czaplewski 1984). M. volans feeds primarily on moths. It is also known to feed on other soft bodied prey such as flies, termites, lacewings, wasps, bugs, leafhoppers, and small beetles. M. volans is a rapid, direct flier pursuing its prey over relatively long distances through, around, under and over forest canopy (Warner and Czaplewski 1984).

Western Pipistrelle (Pipstrellus hesterus)

is usually the first bat to appear in the evening. The Western Pipistrelle often flies before dark and is even seen in broad daylight. Its flight is erratic and slow, less than 6 mph (10 km/h). It skims ponds or streams, dipping its lower jaw into the water to sip while flying. In colder areas, Western Pipistrelles generally hibernate in caves, mines, and crevices, although some migrate southward. Maternity colonies and individual females have been seen on a cliff, and one colony was discovered under shutters in California. The jerky flight of the Common Pipistrelle (P. pipistrellus) of Great Britain and Europe inspired the name "flittermouse" (Fledermaus in German) for bats. Two young are born in June in small maternity colonies of up to about 12 individuals. This species ranges from southeastern Washington and eastern Oregon south to California, Utah, Arizona, western New Mexico, and north-central and Big Bend areas of Texas.

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