Natalidae

(vertebrate zoology) The funnel-eared bats, a monogeneric family of small, tropical American insectivorous bats (Chiroptera) with large, funnellike ears.

(Natalidae)

Class: Mammalia

Order: Chiroptera

Suborder: Microchiroptera

Family: Natalidae

Thumbnail description
Small slim-bodied bats with soft long fur; legs proportionally very long; large pale ears with distinctive papillae; facial skin pale; eyes tiny; tail longer than head and body

Size
Head and body length: 2 in (5 cm); tail 1.7–2.4 in. (4.3–6.0 cm); forearm length 1.4–1.8 in (3.5–4.5 cm); weight 1.4–2.5 oz. (4–7 g)

Number of genera, species
1 genus; 5 species

Habitat
Dry and semi-deciduous forest, secondary growth; occasionally in primary forest

Conservation status
Vulnerable: 1 species; Lower Risk/Near Threatened: 1 species

Distribution
Central and South America, Caribbean Islands

Evolution and systematics

Known by fossils and subfossils back to the Pleistocene, this family speciated in the Antilles, which have three of today's five species. One species has a very restricted distribution, being known only from two small islands in the Bahamas. This island-by-island speciation pattern parallels that of Old World fruit bats in Southeast Asia. In diet, flight pattern, and body form, this genus shows remarkable parallels with the unrelated Old World bat genus Kerivoula, the painted bats of Africa and Southeast Asia. Recent analysis of DNA has supported the conclusions of anatomists that the families Natalidae, Furipteridae, and Thyropteridae (along with the Old World Myzopodidae) are a very closely related quartet. Two of the species were formerly placed in a separate genus, Chilonatalus, while a third was considered to belong to Nyctiellus. The two are now generally considered to be subgenera of Natalus. The generic name means "related to one's birth," and refers to the small size of the adults, which look like young bats even when fully grown.

Physical characteristics

Adult male natalids have a gland-like structure in the center of the forehead. Though characteristic of the family, the precise function of this free-floating disc is uncertain. The thumb is short and nearly completely enveloped in a skin of the wing (in the closely related family Furipteridae, it is completely enclosed). Possibly as a means of providing extra flexibility in flight or perhaps to avoid wing damage in the cluttered under-story in which natalids usually fly, the third joint of the third finger remains cartilaginous, even in adults. Exceptionally long, the legs can be longer than the head and body combined. The ears are broader than high, and shaped like three-quarters of a funnel. Seeming to dominate the face, they probably serve to focus the very slight sounds of moth flight to the hunting bat. Like Kerivoula, the cone-shaped ears of natalids have small papillae on the inner surface. These may improve auditory sensitivity in some as-yet unknown way. All natalids lack a true nose leaf. However, at the tip of the snout there is a hairy protuberance that resembles a nose leaf.

As befits very small bats, natalids emit very high-pitched calls, up to 170 kHz.

Distribution

One species is widely spread, occurring from northern Mexico to eastern Brazil and certain Caribbean islands. Another occurs in northern South America and adjacent offshore islands. The other three are restricted to islands or island groups in the Caribbean.

Habitat

Dry and seasonally deciduous forests, rarely above 984 ft (300 m), though there are verified records up to 7,874 ft (2,400 m).

Behavior

All natalids roost deep in caves where it is hot and humid and the climate changes little. Individuals hang in widely spaced colonies of up to 300. Northern populations of N. stramineus may migrate in winter. In between foraging bouts, natalids may roost under overhanging rock ledges outside caves.

Feeding ecology and diet

Natalids generally leave their roost in groups 30 minutes after sunset. The greatest feeding activity occurs in forest two hours after sunset. Natalids are very agile fliers, able to fly in and out of dense under-story vegetation in search of insects. Their flight is fast and fluttery. Frequency of their echolocation calls exceeds 85 kHz, providing a very detailed "image" of the world. Because of this, natalids are rarely caught in mist nets.

Reproductive biology

Single offspring are often born late in the dry season. At this time, females establish separate maternity colonies. Species of this family are most likely polygynous.

Conservation status

Populations may be limited by dependence on deep caves as roosts. IUCN classifies N. tumidifrons as Vulnerable and N. lepidus as Lower Risk/Near Threatened.

Significance to humans

Humans have severely impacted populations of Natalus. Fossils show that today's very patchy distribution reflects past extinctions of formerly more-widespread populations. Cave-inhabiting humans may have been especially damaging, but many populations were probably affected by post-ice age climatic change and sea level rises that flooded caves and altered the environment within those that remained.

Species accounts

Resources

Eisenberg, J. F., and K. H. Redford. Mammals of the Neotropics. Volume 3, The Central Tropics: Ecuador, Peru, Bolivia, Brazil. Chicago: University of Chicago Press, 1999.

Reid, F. A. A Field Guide to the Mammals of Central America and Southeast Mexico. Oxford: Oxford University Press, 1997.

Woods, C. A., and F. E. Sergile, eds. Biogeography of the West Indies: Patterns and Perspectives. Boca Raton: CRC Press, 2001.

Buden, D. W. "A Guide to the Identification of the Bats of the Bahamas." Caribbean Journal of Science 23 (1987): 362–367.

Bat Conservation International. P.O. Box 162603, Austin, TX 78716 USA. Phone: (512) 327-9721. Fax: (512) 327-9724. E-mail: batinfo@batcon.org Web site:

[Article by: Adrian A. Barnett, PhD]

Funnel-eared bats
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Chiroptera Family: Natalidae Gray, 1866
Genera
Chilonatalus Natalus Nyctiellus

The family Natalidae, or funnel-eared bats are found from Mexico to Brazil and the Caribbean islands. The family has three genera, Chilonatalus, Natalus and Nyctiellus. They are slender bats with unusually long tails and, as their name suggests, funnel-shaped ears. They are small, at only 3.5 to 5.5 cm in length, with brown, grey, or reddish fur. Like many other bats, they are insectivorous, and roost in caves.

References

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