Lasiurus egasouthern yellow bat

Geographic Range

Lasiurus ega is widely distributed from Mexico south to Argentina, but the range seems to be extending northward into parts of California, Texas, Arizona and New Mexico.


Bats of the genus Lasiurus generally occur in wooded areas and roost in foliage. Occasionally these bats roost in tree holes or buildings. In the U.S. L. ega is associated with introduced palms, which is thought to be a reason for its recent expansion northward.

Physical Description

A whitish buff, yellowish, or orange, usually with a blackish wash. Tail membrane is well furred.

  • Range mass
    10 to 18 g
    0.35 to 0.63 oz
  • Average mass
    12 g
    0.42 oz


Normal litter size is 2 or 3 young, although individuals have been known to have single young. Estimated gestation period is 80-90 days. Mating occurs in the late summer or fall with sperm being stored overwinter in the uterus. Ovulation and fertilization occur in the spring with births occurring from late May to early July.

  • Range number of offspring
    2 to 4
  • Range gestation period
    90 to 105 days


These bats are generally solitary, but females of some related species are known to form small nursery colonies and form flocks of several hundred for migration. Males do not generally congregate in summer, but may congregate during winter.

Communication and Perception

Food Habits

L. ega eats primarily insects caught in flight but is also known to alight on vegetation to pick off insects. Feeding flights are 6-15 m. above ground.

Economic Importance for Humans: Positive

May help to control harmful species of insects.

Economic Importance for Humans: Negative

Several cases of rabies have been reported in Lasiurus ega in southen California. In one instance, an individual landed on a human's bare foot and punctured the toe. Before 1979, there were no known instances of this species carrying rabies.

Conservation Status

Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Lasiurus ega mortalities as a result of white-nose syndrome, the disease continues to expand its range in North America.


Bridget Fahey (author), University of Michigan-Ann Arbor.



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

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.


uses smells or other chemicals to communicate


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.


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


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.


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season


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


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.


uses touch to communicate


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


Walker's Mammals of the World

Journal of Wildlife Diseases 15(2) 1979: 343-345

Cryan, P. 2010. "White-nose syndrome threatens the survival of hibernating bats in North America" (On-line). U.S. Geological Survey, Fort Collins Science Center. Accessed September 16, 2010 at

National Park Service, Wildlife Health Center, 2010. "White-nose syndrome" (On-line). National Park Service, Wildlife Health. Accessed September 16, 2010 at