Indiana mouse-eared
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Indiana mouse-eared mouse ( Myotis sodalis ) |
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| Myotis sodalis | ||||||||||||
| Miller , 1898 |
The Indiana mouse -eared mouse ( Myotis sodalis ) or Indiana bat is a bat species from the smooth-nosed family (Vespertilionidae), which is native to North America. It is named after its main area of distribution. The species name sodalis is Latin and means "comradely", which refers to the large group sizes in which the animals can be found.
description
The Indiana mouse- eared bat is a small bat with a forearm length of 36 to 40.6 mm and a wingspan of 240 to 267 mm. With a weight of 7.5 g, the females are slightly larger than the males with 7.1 g ( sexual dimorphism ). The short blunt tragus does not reach all the way to the middle of the auricle. The tail skin is hairy on the knees. The calcar is long and curved, the feet are a little more than half the length of the tibia . The fur is fluffy and of a dull gray-brown.
The Indiana mouse- eared bat is often confused with the small brown bat ( Myotis lucifugus ), but differs from it in the bristle-like hairs on the toes, the curved calcar and the smaller foot (9 instead of 10 mm).
Way of life
The Indiana mouse-eared mouse, like most bats, is nocturnal and feeds on insects, with preference for moths and other soft-bodied insects. On foraging flights they reach a flight speed of over 20 km / h. The echolocation calls emitted in the process range between 96 and 40 kHz and are therefore imperceptible to the human ear. The Indiana mouse- eared bat is one of the most widely studied species of bats in the context of hibernation . During hibernation, red blood cells are stored in the spleen , which leads to a 5-fold enlargement of the organ and a 41% decrease in red blood cells in the blood. During awakening, the blood cells are released from the spleen, which is likely to serve to carry more oxygen during the awakening phase and thus to accelerate the awakening. In September, shortly before hibernation, the animals gain 50% body and fat mass, which is continuously broken down during hibernation.
The body temperature of the Indiana mouse-eared mouse is always 1–1.5 ° C above the ambient temperature. If the ambient temperature falls below zero degrees outside of the hibernation phase, the bat goes into torpor and maintains a body temperature above freezing point by trembling the muscles. Temperatures above 35 ° C are poorly tolerated and can be fatal for the animals. The Indiana mouse-eared bat shares its roost with other bat species such as the small ( M. lucifugus ) and large brown bat ( Eptesicus fuscus ), M. septentrionalis , M. grisens , M. austrioriparius and Pipistrellus subflavus .
During hibernation, sandstone caves with ponds are preferred. The Indiana mouse-eared mouse-ear forms clusters that hang from the smooth ceilings or walls of the cave. Myotis sodalis prefers an ambient temperature of 2 to 5 ° C, an average relative humidity of 87% and occasionally good ventilation. The animals wake up every 8–10 days so that there are always animals in the group that are not asleep. The hibernation den is vacated in April or early June, with the females leaving earlier than the males. Then the animals migrate up to 480 km to their summer areas. Thus, the Indiana mouse-eared bat is one of those bats that migrate .
The oldest bat of this species ever found was over 20 years old. Well-known predators are the mink , snakes like the peanut snake and owls like the Eastern Screech Owl .
Reproduction
The Indiana mouse-eared mating takes place between September and October. The females store the sperm through the winter; the ovulation and subsequent fertilization of the egg takes place after hibernation in the spring. In summer the females separate from the males and form mother colonies of rarely more than 100 animals, in which they give birth and suckle their young until they are independent after 25-37 days. The females give birth to a single young each year. Mother colonies are mostly found under loose tree bark and in hollow tree trunks, but not in caves. After the young can fly independently, they accompany their mother in tandems on foraging flights.
Hazard and protection
The population of the Indiana mouse-eared ear is classified by the IUCN as endangered ("endangered") because of its small range. The reason for this is a 50% decline in the population over the past 10 years. Even after the Endangered Species Act of the US Congress in 1973, numerous measures were taken to protect the species. Previously, populations declined due to natural disasters, human disturbance and changes in the climate in the caves. The number of animals decreased by 28% within 15 years. In 1978, 87% of the total population wintered in a single Indiana cave . These and other important wintering caves are under protection. In addition to the endangerment of the hibernation areas, the protection of the Indiana mouse-eared mouse is difficult because it is hardly known where the animals spend the summer. Females are mostly found in mother colonies under loose tree bark, but practically nothing is known about the ecology of the males.
One of the most important hazards is human interference. When bats unintentionally wake up from hibernation, they use up valuable energy reserves. This is particularly a problem in commercial caves. In addition, there is the deliberate killing of the animals by private cave owners, the change in the climate inside the cave by opening additional entrances, and the improper blocking of the cave entrances. Furthermore, Myotis sodalis is one of those bat species that are endangered by the White Nose Syndrome .
distribution and habitat
The Indiana mouse-eared mouse is found in the United States in the west of Kansas to the east coast, and in the north of Michigan to the south of Alabama .
literature
- CE Thomson (1982): Myotis sodalis . In: Mammalian Species , No. 163, pp. 1-5
