Mexican bulldog bat

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Mexican bulldog bat
Tadarida brasiliensis.jpg

Mexican bulldog bat ( Tadarida brasiliensis )

Systematics
Superordinate : Laurasiatheria
Order : Bats (chiroptera)
Superfamily : Smooth-nosed (Vespertilionoidea)
Family : Bulldog bats (Molossidae)
Genre : Folding-lipped bats ( Tadarida )
Type : Mexican bulldog bat
Scientific name
Tadarida brasiliensis
( I. Geoffroy Saint-Hilaire , 1824)

The Mexican bulldog bat ( Tadarida brasiliensis ), also known as the Brazilian bulldog bat, is a medium-sized bat native to America and is widely considered to be the most abundant mammal in North America . However, their tendency to rest in large numbers and in relatively few quarters at the same time makes them particularly vulnerable to human disturbance and the destruction of their habitats. In some locations, such as in the state of Utah , declining numbers have already been documented. In the western coastal state of California , the bat is already regarded as a particularly endangered species due to the sharply declining population. Little is known about their habits and whereabouts during winter migration . The Mexican bulldog bat is also the official state bat of the two states of Oklahoma and Texas and represents the logo of the Bacardi Rum brand.

anatomy

Mexican bulldog bats grow up to 9 cm long and weigh about 12.3 g. The tail is almost half of its length. The large ears are used to improve echolocation ; these are located near the snout and eyes. The bat tail stretches further than the uropatagium , the flight membrane between the tail and the rear extremity; this is why this species is called "free-tailed bat" in English. Mexican bulldog bats have a thick, silky fur, which is usually gray or dark brown in color. Above the shortened snout is a wrinkled upper lip. The extended wings have a narrowed tip and thus enable the Mexican bulldog bats to fly very fast, straight at a top speed of 160 km / h.

Distribution and ecology

Flying bulldog bats near a den in Texas

The Mexican bulldog bat is one of the most common mammals in the western hemisphere. They occur in the southern terrestrial half of the United States, Mexico, Central America, and South America. Their distribution in South America is still relatively unexplored. There they live in the Brazilian highlands, in the northeastern Andes, on the Peruvian coast and in the north of Chile. The Mexican bulldog bat appears sporadically in the Amazon rainforest. The bat is widespread in the Caribbean and native to the Greater Antilles and eleven of the Lesser Antilles. The largest known colony, with an estimated 20 million individuals, is located in Bracken Cave , in northern San Antonio, Texas . There they live in large numbers at an altitude of 180 to 1000 m, and even up to 3000 m.

habitat

Mexican bulldog bats live primarily in caves, but they also inhabit buildings of all kinds as long as they have access to openings and dark recesses in roofs or walls. Bats can turn all buildings into their resting places, regardless of “age, size, architecture, building materials, occupancy with people and compass orientation”. However, caves must have enough surface area on walls and ceilings to be able to accommodate millions of bats at the same time. Prior to building habitation, bulldog bats likely resided in hollows of trees such as the red mangrove , black mangrove , white mangrove, and cypress in the southeastern United States . However, most Florida bats seem to prefer man-made structures to natural hiding places. Florida caves often have pools of water at the bottom, which is why they are mostly inhabited by the southeastern mouse-eared bat . This phenomenon is explained by the higher need for relative humidity, which the bulldog bat does not need as much.

migration

Mexican bulldog bats over Carlsbad Caverns National Park , New Mexico

The Mexican bulldog bats from southeastern Nevada, southwestern Utah, western Arizona, and southeastern California congregate to jointly migrate southwest to southern California and Baja California. The bats that come from southeastern Utah, southwestern Colorado, western New Mexico and eastern Arizona fly together over the western part of the Sierra Madre Oriental to Jalisco, Sinaloa and Sonora. This summer, however, some bats from Kansas, Oklahoma, eastern New Mexico and Texas will migrate south to southern Texas and Mexico. In other areas of North America there are some populations of bats that do not fly to other countries because they can adapt to the environmental conditions of the seasons. A colony of bulldog bats spends the summer in Austin , Texas under the Congress Avenue Bridge , ten blocks from the Texas State Capitol . It is one of the largest urban colonies in North America and contains approximately 1,500,000 bats. 100,000 tourists come to Texas every year to watch the bats. Another colony lives in Houston , Texas under the Waugh Street Bridge over the Buffalo Bayou. 250,000 bats live there, which also attract many visitors. In Texas, the bulldog bat is officially called the "flying mammal". Eastern Texas bats do not typically migrate, but seasonal local shifts can occur. Bulldog bats, which live in the area from Oregon to California, inhabit this area year round.

nutrition

Mexican bulldog bats are primarily insectivores. They hunt their prey with the help of echolocation. Their prey consists of butterflies , beetles , dragonflies , flies , bed bugs , wasps , and ants . The bats usually catch their prey in flight. Large numbers of Mexican bulldog bats fly hundreds of feet above the Texan soil to eat migratory insects.

Mexican bulldog bats are good pollinators and also eat dangerous insects. Their pollination of sugar cane benefits the plant a lot, as does the consumption of insects that damage it.

Enemies and mortality

An individual was recorded with a lifespan of 8 years, the age was determined with the help of the development of the teeth and the eruption of the teeth, the so-called dentition . Proven predators of Mexican bats are large birds such as the great spotted falcon , the Mississippi Weih , the red-tailed buzzard , the cuckoo , the great horned owl and the barn owl . Among the mammals there are skunks ( strip skunk and piglet skunk ), the raccoon and the southern opossum . Snake species such as the Rat Snake , the masticophis flagellum , the North American copperhead and coral snake also belong to a lesser extent to the Predators . With the grass perch as an example, they are also occasionally eaten by fish. Some species of beetles catch young and newborn bats that have fallen to the ground. The bats are less prone to rabies , at least this appears to be the case in the United States. Traces of pollutants can also be found in the bats, including some pesticides .

behavior

Mexican bulldog bats are nocturnal foragers and begin to feed after dark. You can travel up to 50 km in a fast, direct flight pattern to eat. This species is the highest flying bat (up to 3300 m). Bulldog bats are most active in the early morning hours and afternoons in June and September, especially when the weather is warm.

Echolocation

Mexican bulldog bats use echolocation to navigate and capture prey. Their calls are of a short but constant frequency, but this frequency can be varied between 40 and 75 kHz after detecting prey or the like. Typically the frequency range of their echolocation is between 49 and 70 kHz, but can also be between 25 and 40 kHz if something crosses their path during the flight.

Mating and reproduction

Bulldog bats rest in a cave in the Bahamas

During the breeding season, the females cluster in the maternity roost. The size of these sleeping areas depends on the environment, for example they are larger in caves. Mating can be done in an aggressive or passive form. In the aggressive form, the male controls the movements of the female so that she stays away from the other bats in the roost. It also tends to sing when paired. During passive copulation, the male flies to the female's sleeping place and mounts it calmly without resistance. These bat species are breeders who frequently change partners and both sexes copulate with multiple partners. The females become sexually mature at around nine months, while the males are sexually mature at two years. The females give heat once a year , which usually lasts five weeks and takes place in spring. The gestation period for bats is 11–12 weeks, with only one newborn. A number of young animals remain in “day nurseries” while their mothers rest elsewhere. The females use vocalization and scent to identify their pups. The mother also impresses her scent on the newborn. However, the young newborns try to suckle any female that joins the group. A mother breastfeeds her young every day, after 4–7 weeks it is fully grown, completely weaned and independent.

protection

Although there are large numbers of bats, the local population actively contributes to the protection and conservation of the habitats. An example of this would be the caves near Monterrey, which in summer and autumn are the habitat of the largest population of bulldog bats in Cueva de la Boca. In 2006 the Mexican environmental protection NGO Pronatura Noreste bought the property because the population of the original 20 million bulldog bats had reduced to 95%. Uncontrolled tourism, heavy pollution in the caves and vandalism were the reasons for putting this area under nature protection. Not only the bulldog bats benefit from the new habitat, but also other ecologically important animal species.

Web links

Commons : Mexican bulldog bat ( Tadarida brasiliensis )  - Collection of images, videos and audio files

Individual evidence

  1. ^ Carlsbad Caverns National Park - Bats' Wintering Sites (US National Park Service) . Retrieved October 20, 2013.
  2. ^ Gary F. McCracken, Kamran Safi, Thomas H. Kunz, Dina KN Dechmann, Sharon M. Swartz, Martin Wikelski. Airplane tracking documents the fastest flight speeds recorded for bats. Royal Society Open Science, 2016; 3 (11): 160398, doi: 10.1098 / rsos.160398 .
  3. ↑ a b c K. Wilkins: Tadarida brasiliensis . In: Mammalian Species , 331, 1989, pp. 1-10.
  4. ^ RJ Baker, HH Genoways: Zoogeography of Antillean bats . In: FB Gill (Ed.): Zoogeography in the Caribbean . Acad., Philadelphia 1978, pp. 53-97.
  5. ^ BP Glass: Seasonal movements of Mexican free-tail bats Tadarida brasiliensis mextcana banded in the Great Plains . In: Southwestern Nat., 27, 1982, pp. 127-133.
  6. ^ Bat Conservation International page on the Congress Avenue Bridge Bat Colony . Archived from the original on October 11, 2008. Retrieved October 20, 2013.
  7. ↑ Texas State Symbols, Texas State Library and Archives Commission . Retrieved October 13, 2013.
  8. ↑ L. McWilliams: Variation in diet of the Mexican free-tailed bat ( Tadarida brasiliensis mexicana ) . In: Journal of Mammalogy , 2005, 86/3, pp. 599-605.
  9. ^ Gary F. McCracken, Erin H. Gillam, John K. Westbrook, Ya-Fu Lee, Michael L. Jensen, Ben B. Balsley: Brazilian free-tailed bats ( Tadarida brasiliensis : Molossidae, Chiroptera) at high altitude: left to migratory insect populations . In: Integrative and Comparative Biology , 48 (1), 2008, pp. 107-118.
  10. ↑ M. Gannon, A. Kurta, A. Rodriquez-Duran, M. Willig: Bats of Puerto Rico. Jamaica . The University of the West Indies Press, 2005.
  11. ↑ T. Williams, L. Ireland, J. Williams: High altitude flights of the free-tailed bat, Tadarida brasiliensis, observed with radar . In: Journal of Mammalogy , 54/4, 1973, pp. 807-821.
  12. ^ P. Svoboda, J. Choate: Natural history of the Brazilian free-tailed bat in the San Luis Valley of Colorado . In: Journal of Mammalogy , 68/2, 1987, pp. 224-234.
  13. ↑ L. Allen, A. Turmelle, M. Mendonca, K. Navara, T. Kunz, G. McCracken: Roosting ecology and variation in adaptive and innate immune system function in the Brazilian free-tailed bat (Tadarida brasiliensis). In: Journal of Comparative Physiology , 179, 2009, pp. 315-323.
  14. ^ A b E. Gillam, G. McCracken: Variability in the echolocation of Tadarida brasiliensis: effects . In: Animal Behavior , 74. 2007, pp. 277-286.
  15. ^ A b A. Keeley, B. Keeley: The Mating System of Tadarida brasiliensis (Chiroptera: Molossidae) in a Large Highway Bridge Colony. In: Journal of Mammalogy , 85/1, 2004, pp. 113-1.
  16. ↑ W. Loughry, G. McCracken: Factors influencing female-pup scent recognition in Mexican free-tailed bats . In: Journal of Mammalogy , 72/3, 1991, pp. 624-626.
  17. ^ T. Kunz, S. Robson: Postnatal growth and development in the Mexican free-tailed bat (Tadarida brasiliensis mexicana): birth size, growth rates, and age estimation . In: Journal of Mammalogy , 76/3, 1995, pp. 769-783.