Lasiurus blossevilliiwestern red bat

Geographic Range

Lasiurus blossevillii, the western red bat, exhibits a widespread distribution, including southern British Columbia, most of the western United States, through Mexico and Central America, and even as far south as Argentina, Brazil, Bolivia, Uruguay, and Chile in South America. It is also present in Tobago and Trinidad, and can be found in the Galapagos. (Bucknell Univesity, 2008; Pierson and Rainey, 1998)


Roosting sites of Lasiurus blossevillii are found in the foliage of trees and shrubs in forests, most commonly 1.5 to 12 m above the ground. The western red bat's ideal roosting tree is dark and sheltered above the roost sit for protection from predators and clear below the roost, allowing the bat to easily exit and approach the tree. It often relies on riparian trees for roosting and foraging, and has been associated with mature stands of cottonwood, sycamore, and willows adjacent to streams. Lasiurus blossevillii has also been associated with some fruit trees in orchards, and some evidence has been found to indicate that they may occasionally use caves. They can often be seen feeding in rural and suburban areas, around streetlights and other light sources. (Pierson and Rainey, 1998; Pierson and Rainey, 2004)

Physical Description

Lasiurus blossevillii is a medium sized bat with red-colored pelage, varying from rusty red to brownish red. This red fur distinguishes L. blossevillii from all other western bats with the exception of the Eastern Red Bat, Lasiurus borealis, which is slightly larger. Most cranial measurements of L. blossevillii are significantly larger than other species, and it also lacks the frosted appearance that L. borealis exhibits. Lasiurus blossevilli has a short rostrum and ears that are short and rounded, with a prominent tragus. Its interfemoral membrane is covered in fur, with the exception of the last posterior third of the membrane, which is only sparsely haired. Their tails extend to the edge of the uropatagium. Western red bats have a total length of 103 mm. Length from notch to ear averages 13 mm, and forearm length is 35 to 45 mm. Average length of tail is 49 mm, with a foot length of 10 mm. (Lesson and Garnot, 1997; Pierson and Rainey, 1998; Texas Parks and Wildlife Department, 2013)

  • Average length
    103 mm
    4.06 in
  • Range wingspan
    35 to 45 mm
    1.38 to 1.77 in


Vespertilionids have been known to exhibit diverse mating systems. Though there is not much information on L. blossevillii, in its family there are systems such as monogamy, polyandry, seasonal multi male/multi female groups, year-round harems with less stable female composition, and seasonal single male/multi female groups. Some vespertilionids have also exhibited promiscuous mating systems and resource defense polygyny. (McCracken and Wilkinson, 2000)

Red bats can have up to five pups in a litter, unlike most in the vespertillionidae family which tend to have a single offspring each year. Some vespertillionids have the ability to delay certain aspects of reproduction as an adaptation for their winter hibernation, such as storing sperm until spring. Because the insects that the bats eat are most abundant during the early summer, red bats mate in late summer to early fall and store the sperm in the vagina or uterus until after hibernation. Once the female has aroused from hibernation, ovulation occurs and the sperm is motile. This allows the babies to be born during the ideal time for their feeding habits. Once the pups are born, they can fly at 3 to 6 weeks of age. (Texas Parks and Wildlife Department, 2013)

  • Breeding season
    Lasiurus blossevillii breed during late summer to early fall.
  • Range number of offspring
    1 to 5
  • Average number of offspring
  • Range gestation period
    80 to 90 days

Though there is not much data on the parental investment that L. blossevillii displays, there have been many observations of the closely related Lasiurus borealis that may have similar parental care. During the day, a L. borealis mother allows her young to cling to her with their wings while she hangs. The babies hang from a twig or leaf as they clasp their mother so that she is not burdened by the full weight of of her pups. During any hour of the day, young can be found exercising, stretching, cleaning themselves, and interacting with their mother. The mother will leave the young in the evening to search for food. Vespertillionid mothers will provide milk for their pups while they grow until they have reached at least 90% of their adult wing dimensions. This is a unique investment into the young that is advantageous because the pups are unable to maintain flight and forage for a long period of time until they have reached those wing dimensions. (Barbour and Davis, 1969; Racey and Swift, 1995)


The lifespan of Lasiurus blossevillii is unknown.


There is not any evidence at this time to indicate that Western Red Bats undergo mass migration, but some evidence is available for the eastern form and other Lasiurus species. Most Lasiurus species migrate seasonally, traveling to more temperate climates for the winter, but some red bats have been discovered to hibernate in leaf litter throughout the winter instead of migrating. It is unknown whether this is the case for L. blossevillii or not. It is difficult to determine if western red bats migrate during cold winters considering that most western red bats have been recorded in California during the winter, where they would not experience extreme winter climates. Lasiurus blossevillii tends to roost alone in the foliage of trees such as willows, cottonwoods, and sycamores. These roost sites are used during the day as the bat sleeps, and are left roughly two hours after sunset to forage for insects. (Pierson and Rainey, 2004; Texas Parks and Wildlife Department, 2013)

Communication and Perception

Vespertilionids possess a specialized larynx that allows them to produce ultrasonic sounds which are then emitted through their nose or mouth. This form of communication is called echolocation. The ultrasonic sound refracts off of objects and returns to their highly modified ears. The bat's brain can then use the information gathered from the echoes to produce a picture of its surroundings. Because L. blossevillii is active at dusk and during the night, it uses echolocation to avoid running into objects while flying and also uses it to locate food as it is foraging without the aid of light. (Woodward, 2004)

Food Habits

Red bats have a diet of insects, with about 26% of that diet consisting of moths. They forage from tree canopy height to just above ground. They typically begin one to two hours after sunset, with the majority of their foraging corresponding with the activity of the nocturnal insects that they are hunting, sometimes foraging throughout the night to catch the insects that are active in the early hours before sunrise. Lasiurus blossevillii has been observed feeding in urban areas around street lights and flood lights, but seem to prefer towns and rural areas to the more highly human populated urban areas. The winter feeding habits of L. blossevillii are not well understood, but recent documentations indicate that they occasionally arouse from their hibernation during warm days to forage briefly, then return to their hibernation when temperatures drop again. (Pierson and Rainey, 1998; Texas Parks and Wildlife Department, 2013)

  • Animal Foods
  • insects


While many other bat species are well protected from predators due to dwelling in caves and crevices during the day, Lasiurus blossevillii is more open to predation because of its foliage dwelling habits. Western red bats have been recorded being preyed upon by Virginia opossums, and have been attacked and killed by birds on numerous occasions, with jays being the most common attackers. Other birds that prey upon these bats include falcons, owls, raptors in the genus Accipiter, and even roadrunners. Domestic cats have also been known to prey upon these bats. (Pierson and Rainey, 1998; Texas Parks and Wildlife Department, 2013)

Ecosystem Roles

Lasiurus blossevillii plays an important part in its ecosystem as an insect consumer. With its consumption of insects each night it aids in managing the population of certain insects such as moths and mosquitoes. (Pierson and Rainey, 1998)

Economic Importance for Humans: Positive

Lasiurus blossevillii benefits humans through insect control, as red bats are insectivores and consume large amounts of insects when they forage at night. Another beneficial aspect is that western red bats are not commonly found inside human residences, as they tend to stay away from most urbanized areas, so there is little interaction. (Woodward, 2004)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

A potential detriment to human populations that these bats present is disease transmission. Two diseases that bats can transfer to humans are rabies and histoplasmosis. A significantly low percentage of these bats contract rabies, so they do not pose a larger threat to humans that dogs or cats. In the instance that a bat has rabies, it will rarely show signs of aggression and will die shortly after. Humans can be exposed to histoplasmosis when contaminated dust particles in the air are inhaled. (Woodward, 2004)

Conservation Status

Lasiurus blossevillii is categorized as a species of "least concern" by the IUCN.


Jenifer Lavender (author), Georgia Southern University, Michelle Cawthorn (editor), Georgia Southern University, Angela Miner (editor), Animal Diversity Web Staff.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


living in the southern part of the New World. In other words, Central and South America.

World Map


uses sound to communicate


living in landscapes dominated by human agriculture.


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


an animal that mainly eats meat

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal


uses smells or other chemicals to communicate


active at dawn and dusk

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.


The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


An animal that eats mainly insects or spiders.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"


living in residential areas on the outskirts of large cities or towns.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


Living on the ground.


uses sound above the range of human hearing for either navigation or communication or both


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Barbour, R., W. Davis. 1969. Bats of America. Lexington, Kentucky: The University of Kentucky Press.

Bucknell Univesity, 2008. "Lasiurus Blossevillii" (On-line). Wilson & Reeder’s Mammal Species of the World, Third Edition. Accessed April 22, 2013 at

Lesson and Garnot, 1997. "Western Red Bat, Lasiurus blossevillii" (On-line). Accessed April 22, 2013 at

McCracken, G., G. Wilkinson. 2000. Bat Mating Systems. Reproductive Biology of Bats, 12: 3-5. Accessed April 22, 2013 at

Pierson, E., W. Rainey. 2004. "Distribution and Status of Western Red Bats (Lasiurus blossevillii) in California" (On-line). State of California Resources Agency, Department of Fish and Game habitat Conservation Planning Branch.. Accessed April 22, 2013 at

Pierson, E., W. Rainey. 1998. "Terrestrial Mammal Species of Special Concern in California" (On-line). California Department of Fish and Game. Accessed April 22, 2013 at

Racey, P., S. Swift. 1995. Ecology, Evolution and Behavior of Bats. Oxford: Clarendon Press.

Texas Parks and Wildlife Department, 2013. "Western Red Bat (Lasiurus blossevillii)" (On-line). Texas Parks & Wildlife. Accessed April 22, 2013 at

Woodward, N. 2004. "Lasiurus borealis, Red Bat" (On-line). Accessed April 22, 2013 at