Spixs diskwinged bat

Thyroptera tricolor

TAXONOMY

Thyroptera tricolor Spix, 1823, Amazon River, Brazil. Three subspecies are recognized.

OTHER COMMON NAMES

German: Haftscheiben-Fledermaus; Spanish: Murcielago de ventosas, murcielago tricolor con mamantones.

PHYSICAL CHARACTERISTICS

Back (and sometimes throat) dark brown to reddish brown. Belly white or yellowish; flanks are frequently an intermediate color; ears blackish. Calcar has one cartilaginous bump. Tail long, extending (0.19-0.31 in [5-8 mm]) beyond the uropatag-ium. Females are slightly larger than males.

DISTRIBUTION

From Veracruz, Mexico, to southeast Brazil. Apparently absent from El Salvador and Nicaragua.

HABITAT

Individuals captured in a number of different habitats within rainforest, including primary forest, swamp, and man-made clearings. Not recorded above 4,265 ft (1,300 m), and usually below 2,625 ft (800 m).

BEHAVIOR

All known roosts have been in foliage. In French Guiana, most roosts were found in unrolled new leaves of Heliconia plants or, to a lesser extent, of Phenakospermum. A smaller number of roosts were found in old, dead, scrolled leaves of Phenakosper-mum. Elsewhere, also recorded in rolled-up arrowroot (Ca-lathea, Marantaceae) leaves. Most roosts are near water and none are out of direct sunlight. Preferred leaves form vertical tubes 1.9-3.9 in (50-100 mm) in diameter and do not touch any other vegetation (so reducing the danger of predation by snakes). Such roosts are ephemeral, because the leaves generally unroll within 24 hours. Consequently, the bats must find a new roost once every few days. A stable, socially cohesive group will sequentially occupy all favorable roosts in an area as they become available and defend their patch against other groups. Roosts are generally occupied by one to nine individuals; it is rare for there to be more than one adult male in a roost. Within the rolled-up leaf, individuals roost with the head pointing upward toward the opening, making for a swifter escape if danger threatens. When roosting together, individuals are aligned one above the other. A group's home range may average some 32,290 ft2 (3,000 m2). Groups are clearly social.

FEEDING ECOLOGY AND DIET

Slow, fluttering, agile flight and a tendency to fly low indicate a diet of insects caught close to the ground. Small beetles and flies may be important diet components. Each individual consumes 0.03 oz (1 g) of insects a night (one-quarter of its body weight).

REPRODUCTIVE BIOLOGY

Polygynous. Births probably occur during the peak of the rainy season. Gestation is about two months. Once born, young cannot fly for a month and the female flies and forages with them

attached. By the end of the month, the single baby's weight may be half that of the mother. After the young learn to fly, they may fly with the mother for a few days until fully weaned. Breeding occurs twice a year.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

None; roosting occurs in banana plants but does not endanger any economic interests. ♦

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