Molossus alvarezi, Gonzalez-Ruiz, Ramirez-Pulido & Arroyo-Cabrales, 2011

Don E. Wilson & Russell A. Mittermeier, 2019, Molossidae, Handbook of the Mammals of the World – Volume 9 Bats, Barcelona: Lynx Edicions, pp. 598-672 : 624

11.

Alvarez’s Mastff Bat

Molossus alvarezi

French: Molosse dAlvarez / German: Alvarez-Samtfledermaus / Spanish: Moloso de Alvarez

Other common names: Alvarez's Free-tailed Bat

Taxonomy. Molossus alvarezi Gonzalez-Ruiz, Ramirez-Pulido & Arroyo-Cabrales, 2011 ,

“Rio Lagartos, 20 m, Municipio de Rio Lagartos, Yucatan, Mexico (21°35’51”N, 88°9' 28"W).”

Specimens of Molossus sinaloae from Yucatan were described as M. alvarezi based on morphology. Recent molecular study showed that individuals from Central and South America group with M. alvarezi and not with individuals of M. sinaloae from Pacific slope of Mexico, with which they were previously grouped. Monotypic.

Distribution. Yucatan Peninsula of Mexico, Belize, and Guatemala through Central America into South America, including Colombia, coastal Venezuela, the Guianas, and Amazonian Peru; also on Trinidad I.

Descriptive notes. Head-body 65-88 mm, tail 41-48 mm, ear 10-14 mm, hindfoot 10-12 mm, forearm 42-7-47-4 mm; weight 20-30 g. Alvarez’s Mastiff Bat is larger than Pallas’s Mastiff Bat ( M. molossus ) but smaller than Miller’s Mastiff Bat ( M. pretiosus ) and the Black Mastiff Bat ( M. rufus ). Dorsal fur of Alvarez’s Mastiff Bat is brownish, with wide paler band at base accounting for more than one-half the hair length. Venter is grayish or brownish and always paler than dorsum. Dorsal pelage is long reaching 3-5 mm; ventral pelage is 2-3 mm. Ears are rounded and arise from same point on forehead. Tragus is small, and antitragus is constricted at its base. Face is chocolatebrown, and upper lip and snout are smooth and lack any medial ridge. Wings and uropatagium are brownish. Skull has elongated braincase, triangular occipital region, and infraorbital foramen opening laterally in frontal view. Basioccipital pits are moderately deep. I? is thin and elongated, with parallel tips. Dental formula for all species of Molossusis11/1,C1/1,P 1/2, M 3/3 (x2) = 26. Chromosomal complement has 2n = 48 and FN = 58.

Habitat. Rainforests, low forests, deciduous tropical woodlands, and xeric vegetation bordering coastal, rural, and urban areas from lowlands to elevations of ¢. 2400 m.

Food and Feeding. Alvarez’s Mastiff Bat is an aerial insectivore that mostly eats moths, but beetles and other insects are also part of its diet.

Breeding. In Honduras, pregnant, lactating, post-lactating, and reproductively inactive female and reproductively active male Alvarez’s Mastiff Bats were caught in July. In Nicaragua, pregnant and lactating females were also caught in July and reproductively active males in June-August. In Costa Rica, pregnant females and juveniles were caught throughout the year, but most reproductive activity was observed in May-June and December. Pregnant and lactating females have never been observed at the same time. Littersize is typically one, but twins have been reported in one in 20 litters. Lactation lasts 6-8 weeks.

Activity patterns. Alvarez’s Mastiff Bats are more active two hours after sunset and two hours before dawn. They roost in caves and houses. Search calls are composed of a small FM element and larger CF component. Search calls regularly alternate between two of three tones. First pulse has lower frequency (26-36 kHz), and second pulse has slightly higher frequency (31-38 kHz).

Movements, Home range and Social organization. Colonies of Alvarez’s Mastiff Bats have 20-106 individuals. Three types of roosting social structures were reported: solitary males, multiple-male colonies, and groups of females with occasional or frequent visits by resident males. In Nicaragua, a nursery colony was observed in June with only females and young, and another colony was reported with adult males, lactating females, and young. In February, a small colony with one adult male, one pregnant female, and one young was documented. Alvarez’s Mastiff Bat has been reported roosting with Pallas’s Long-tongued Bat (Glossophaga soricina) and sharing differenttiles in the same roof segment with the Black Mastiff Bat ( Molossus rufus ) and the Common Dwarf Bonneted Bat ( Eumops bonariensis ).

Status and Conservation. Classified as Data Deficient on The IUCN Red List. Because Alvarez’s Mastiff Bat was recently described, no information is yet available on its conservation status.

Bibliography. Arroyo-Cabrales (2014), Birney et al. (1974), Bowles (1972), Bowles et al. (1990), Eisenberg (1989), Freeman (1979), Gonzéalez-Ruiz et al. (2011), Handley (1976), Harris (1943), Heideman et al. (1990), Jones (1966), Jones, Smith & Genoways (1973), Jones, Smith &Turner (1971), Jung et al. (2014), LaVal & Fitch (1977), Loureiro et al. (2019), Marinkelle & Cadena (1972), Mora (2016), O'Farrell et al. (1999), Owen & Girén (2012), Reid (2009), Simmons & Voss (1998), Timm & LaVal (1998), Warner et al. (1974).

Figures

1. Blunt-eared Bat (Tomopeas ravus), 2. Lesser Naked Bat (Chewromeles parvidens), 3. Greater Naked Bat (Chewromeles torquatus), 4. Peters’s Little Mastff Bat (Mormopterus jugularis), 5. Reunion Little Masuft Bat (Mormopterus francoismoutoui), 6. Mauritian Little Mastiff Bat (Mormopterus acetabulosus), 7. Sumatran Little Mastift Bat (Mormopterus doriae), 8. Least Little Mastiff Bat (Mormopterus minutus), 9. Kalinowski’s Little Mastiff Bat (Mormopterus kalinowskii), 10. Incan Little Masuft Bat (Mormopterus phrudus), 11. Alvarez’s Mastff Bat (Molossus alvarez), 12. Aztec Mastff Bat (Molossus aztecus), 13. Coiban Mastuff Bat (Molossus cotbensis)

Distribution. Yucatan Peninsula of Mexico, Belize , and Guatemala through Central America into South America, including Colombia , coastal Venezuela , the Guianas, and Amazonian Peru ; also on Trinidad I.