''Histiotus'' (meaning "sail ears") is a genus of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

vesper bat Vespertilionidae is a family of microbats, of the order Chiroptera, flying, insect-eating mammals variously described as the common, vesper, or simple nosed bats. The vespertilionid family is the most diverse and widely distributed of bat famili ...

s with species that include: * Strange big-eared brown bat, ''Histiotus alienus'' * Cadena-García's big-eared brown bat, ''Histiotus cadenai'' * Colombian big-eared brown bat, ''Histiotus colombiae'' * Transparent-winged big-eared brown bat, ''Histiotus diaphanopterus'' * Humboldt big-eared brown bat, ''Histiotus humboldti'' *

Thomas's big-eared brown bat Thomas's big-eared brown bat (''Histiotus laephotis'') is a species of vesper bat found in South America. Taxonomy and etymology Thomas's big-eared brown bat was species description, described as a new species in 1916 by British zoologist Oldfie ...

, ''Histiotus laephotis'' * Big-eared brown bat, ''Histiotus macrotus'' * Southern big-eared brown bat, ''Histiotus magellanicus'' * Moche big-eared brown bat, ''Histiotus mochica'' * Small big-eared brown bat, ''Histiotus montanus'' * Tropical big-eared brown bat, ''Histiotus velatus'' In Paraguay, ''Histiotus'' bats have mainly been collected at human dwellings or around domestic animals, due to the significant increase in human activity in the Paraguayan Chaco over the last 20 years.

Habitat

''Histiotus'' is found in the tropical and temperate zones in South America. Their natural habitat ranges from areas with rocky mountains, to woods in Paraguay, Peru, Brazil, Argentina and Chile.

Behavior

Echolocation and feeding

''Histiotus'' are aerial feeders and use echolocation to catch prey. They can create echolocation calls dominated by frequencies below 20 kHz in order to catch prey. ''Histiotus'' diet consists of insects; ''H. montanus'' mainly eats butterflies and

flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...

, ''H. macrotus'' eats flies, and ''H. velatus'' eat moths.

Social systems

Most of the species are colonial and some are considered individual. Individual systems are considered for bats that interact as one or less than ten bats. Females of most temperate zone bats form maternity colonies during summer to communally raise pups. These colonies allow individuals to reduce heat loss by forming a cluster. This is called social thermoregulation. (For more on metabolism go to: Metabolism).

Flying adaptations

Flight performance is determined by wing shape and ecological aspects such as foraging behavior (the way they search for food) and habitat selection. Research showed that ''H. montanus'' and ''H. macrotus'' have high maneuverability and low speed, which corresponds to bats that inhabit wooded areas. The high maneuverability or ability to quickly alter flight direction and speed is important for bats to successfully capture prey and avoid predators.

Respiratory and cardiovascular adaptations

Adaptation for flight involves many systems, and specifically cardiovascular and respiratory systems. Bats are considered as mammals adapted to extreme environments where oxygen management is crucial. Respiratory and cardiovascular systems undergo changes that allow the organism to optimize the acquisition and delivery of oxygen to tissues to be able to survive this extreme way of life. Research done on ''H.macrotus'' and ''H.montanus'' shows that they have the same respiratory strategy as other bats: "narrow-based high-keyed strategy." This strategy includes: # larger heart and cardiac output # high

hematocrit The hematocrit () (Ht or HCT), also known by several other names, is the volume percentage (vol%) of red blood cells (RBCs) in blood, measured as part of a blood test. The measurement depends on the number and size of red blood cells. It is nor ...

, high

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

concentration and high blood oxygen transport capacity and # optimization of respiratory structural parameters. In other words, these bats are able to make the most effective use of their respiratory structure.

Metabolism

For bats, energy demands are particularly high during pregnancy or lactation. One way many bats are able to save energy is through the use of

torpor Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the ti ...

, which is a controlled, substantial drop in metabolic rate and body temperature (

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

). In addition to hibernation (prolonged torpor) during winter, temperate zone bats, such as ''Histiotus'', often become torpid during periods of cold weather in summer (daily torpor) to save energy. By reducing metabolic rate, torpor prolongs gestation length and impairs lactation. This results in late births and slow juvenile growth rates. This reduces the probability for juveniles to survive their first winter, because not enough time has passed to store proper amounts of fat prior to hibernation. This is why females of most temperate zone bats, such as ''Histiotus'', form maternity colonies during summer to communally raise pups. These colonies allow individuals to reduce heat loss by forming a cluster and therefore by their behavior they are able to improve insulation and this results in the conservation of energy.

References

{{Authority control Bat genera Taxa named by Paul Gervais