Hot Spots Cool and Heat

a huge group of mexican free tailed bats fly in a flurry out of bat cave at dusk

Biological Strategy

Brazilian free-tailed bat

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Maintain Homeostasis

When a living system is in homeostasis, it means that internal conditions are stable and relatively constant. For example, a human’s internal temperature is approximately 37 degrees Celsius (98.6 degrees Fahrenheit) unless there’s an illness. The human body maintains this temperature despite external ambient temperature. However, as with all physiological processes, maintaining homeostasis requires communication and coordination. So living systems have ways to detect changes from the norm, mechanisms to cause an adjustment, and negative feedback connections between the two. A desert lizard called the Gila monster offers a good example of maintaining homeostasis. The lizard goes from eating large meals to fasting for extended time periods. To maintain its blood sugar levels at a steady level, when food is scarce, its endocrine system releases a hormone that raises its blood sugar levels.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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The flanks of Brazilian free-tailed bats aid thermoregulation due to a unique arrangement of arteries and veins creating thermal windows.

Image: Lauren Sobkoviak /

Image: Jonathan Reichard /

Infrared thermal image revealing radiators on n emerging Brazilian free-tailed bat. Provided by Jonathan Reichard for use on AskNature.

Image: Jonathan Reichard /

Backlit wing of a Brazilian free-tailed bat. Photo provided by Jonathan Reichard for use on AskNature.

Image: Jonathan Reichard /

Vasculature of thermal hotspots on an adult female Brazilian free-tailed bat. Photo provided by Jonathan Reichard for use on AskNature.

Image: Jonathan Reichard /

Daylight emergence of Brazilian free-tailed bats a Frio Cave near Concan, Texas

Image: Jonathan Reichard /

Infrared thermal image of an emerging Brazilian free-tailed bat. Photo provided by Jonathan Reichard for use on AskNature.

“The Brazilian free-tailed bat (Tadarida brasiliensis) experiences challenging thermal conditions while roosting in hot caves, flying during warm daylight conditions, and foraging at cool high altitudes. Using thermal infrared cameras, we identified hot spots along the flanks of free-ranging Brazilian free-tailed bats, ventral to the extended wings. These hot spots are absent in syntopic cave myotis (Myotis velifer), a species that forages over relatively short distances, and does not engage in long-distance migration. We hypothesized that the hot spots, or ‘radiators,’ on Brazilian free-tailed bats may be adaptations for migration, particularly in this long-distance, high-flying species. We examined the vasculature of radiators on Brazilian free-tailed bats with transillumination to characterize the unique arrangements of arteries and veins that are positioned perpendicular to the body in the proximal region of the wing. We hypothesized that these radiators aid in maintaining heat balance by flushing the uninsulated thermal window with warm blood, thereby dissipating heat while bats are flying under warm conditions, but shunting blood away and conserving heat when they are flying in cooler air at high altitudes. We also examined fluid-preserved specimens representing 122 species from 15 of 18 chiropteran families and radiators appeared present only in species in the family Molossidae, including both sedentary and migratory species and subspecies. Thus, the radiator appears to be a unique trait that may facilitate energy balance and water balance during sustained dispersal, foraging, and long-distance migration.” (Reichard et al. 2010:358)

Last Updated September 14, 2016

References

Journal article

Thermal Windows on Brazilian Free-tailed Bats Facilitate Thermoregulation during Prolonged Flight

Integrative and Comparative Biology | May 5, 2010 | J. D. Reichard, S. I. Prajapati, S. N. Austad, C. Keller, T. H. Kunz

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Reference

Journal article

Thermoregulation during Flight: Body Temperature and Sensible Heat Transfer in Free-Ranging Brazilian Free-Tailed Bats ( Tadarida brasiliensis )

Physiological and Biochemical Zoology | February 24, 2021 | Jonathan D. Reichard, Spenser R. Fellows |

Alexander J. Frank, Thomas H. Kunz

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