The range of the mastiff bat, or Eumops bonariensis, extends from Veracruz, Mexico, through Central America and into South America. In southern South America mastiff bats are found throughout Paraguay, sections of Uruguay, and as far south as the Buenos Aires province in Argentina. Mastiff bats have only been found in the lowlands throughout this range. (Redford and Eisenburg 1992, Reid 1997)
Biogeographic Regions: neotropical (Native )
Eumops bonariensis is the smallest of the eight species which comprise the genus Eumops. Mastiff bats have agouti hair coloring. The base of each hair is pale while the tips are frosted. Bristles are not located on the rump but some short hairs can be found on the calcar, which is the bone that gives structure to the membrane between the tail and the hind foot. The snout is broad and flat with a few slight wrinkles on the lips. Their large ears are rounded and, when laid forward, touch the tip of the nose. The fur is soft and somewhat long (5mm). The dorsal side is gray-brown or brown whereas the ventral side is gray-brown. Little else is known specifically about this species but many physical traits are common to all Eumops species. Each species in this genus have a thick head with a broad muzzle. The eyes of Eumops are small compared to species of bats from other genera. Eumops have legs which are short, strong, and muscular with broad feet and a well developed fibula. The wings of Eumops are long, flat, and narrow giving them a high-aspect ratio. The dental formula for the genus is I:1/2,C:1/1,P:2/2, and M:3/3. Measurements (in mm) specifically for E. bonariensis are: head-body length 49-68, tail 28-47, hind foot 6-11, ear 12-19, and forearm 39-48. (Anderson and Jones 1984, Emmons and Feer 1990, Eisenburg 1989, Kunz 1982, Nowak 1999, Redford and Eisenburg 1992, Reid 1997)
Range mass: 7 to 13 g.
Other Physical Features: endothermic ; bilateral symmetry
Eumops bonariensis individuals are found at low elevations in dry, deciduous tropical forests as well as thorn scrub. (Eisenburg 1989, Nowak 1999, Reid 1997)
Terrestrial Biomes: forest ; scrub forest
Habitat and Ecology
The diet of mastiff bats consists of larger, hard-shelled insects, particularly beetles, as well as moths. Eumops are specialized for rapid aerial pursuit of these insects. The long narrow wings and the ability to retract their tail membrane allow the bats in this genus to reduce drag and enhance speed. Eumops have rapid and relatively straight flight compared to that of other insectivorous bats. Laterally placed eyes and ears give Eumops a wide field of perception, which aids in capturing prey. All Eumops emit echolocation "chirps" which are audible to humans. This system allows Eumops to locate prey and then catch it in mid-flight. (Emmons and Feer 1990, Findley 1993, Macdonald 1993, Nowak 1999, Redford and Eisenburg 1992, Reid 1997)
Life History and Behavior
Perception Channels: tactile ; chemical
Information specifically about the reproduction of mastiff bats is not well known. However, members of the family Molossidae typically have 1 young and breed once each year. Breeding occurs before ovulation, which occurs in the late winter or early spring. Gestation lasts 70-90 days. The resulting offspring weigh 3-4g but typically do not exceed 22% of the adult weight. (Grzimek 1989, Nowak 1999)
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
Molecular Biology and Genetics
Statistics of barcoding coverage: Eumops bonariensis
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
Status is unknown.
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
Listed as special protection status by the Mexican NOM - 059 - SEMARNAT - 2001 (as Eumops nanus) (Arroyo-Cabrales pers. comm.).
Relevance to Humans and Ecosystems
Negative effects on humans unknown.
Positive benefits to humans unknown.
Dwarf bonneted bat
As its common name implies, E. bonariensis is the smallest species of bonneted bat. Adults measure 9 to 13 cm (3.5 to 5.1 in) in total length, and typically weigh between 12 and 20 g (0.42 and 0.71 oz). However, there is a significant variation in size between the different subspecies, with the smallest, E. b. nanus, weighing as little as 7 g (0.25 oz).
The fur is thick and silky, and ranges from cinnamon to dark chocolate brown, being noticeably paler on the underside of the body. The head has a broad snout with a fringe of stiff hairs on the upper lip, and long, wide, ears connected by a small membrane. The wing membranes are black, but are covered with sparse hairs close to the arms. Males have been observed to have glands on the throat that become enlarged during the breeding season..
Distribution and habitat
Dwarf bonneted bats are found from southern Mexico through the whole of Central America, and in every country of South America except Chile. They inhabit a wide range of environments, from dense rainforest to dry thorny scrub. They are most commonly found in lowland habitats, but have been found as high as 1,000 metres (3,300 ft) in Colombia. Up to four subspecies are recognised:
- Eumops bonariensis bonariensis - Uruguay and neighbouring regions of Brazil and Argentina
- Eumops bonariensis beckeri - Peru, southern Brazil, Bolivia, Paraguay, northern Argentina
- Eumops bonariensis delticus - northern Brazil, neighbouring regions of other countries
- Eumops bonariensis nanus - Ecuador, Colombia, Venezuela, the Guyanas, and north to southern Mexico
Dwarf bonneted bats feed on flying insects, primarily beetles and moths. They roost in small groups of up to twenty individuals, and are often found sleeping in the roofs of buildings. They are rapid fliers, often remaining high above the ground. They often make loud calls that are audible to humans. Breeding has been recorded from March to June in Mexico, and from October to November at the southern end of the bat's range. Females give birth to a single young.
- Barquez, R., Gonzalez, E., Arroyo-Cabrales, J., Ticul Alvarez Castaneda, S., Cuarón, A.D. & de Grammont, P.C. (2008). Eumops bonariensis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 19 October 2013.
- Hunt, J.L., et al. (2003). "Eumops bonariensis". Mammalian Species: Number 733: pp. 1–5. doi:10.1644/733.