A

Funnel-eared bats

(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

List of Species

Funnel-eared bat
White-bellied funnel-eared bat
Bahamian funnel-eared bat
Small-footed funnel-eared bat
Gervais' funnel-eared bat

Funnel-eared bat

Natalus stramineus

TAXONOMY

Natalus stramineus Gray, 1838, type locality unknown, probably Antigua, Lesser Antilles. Seven subspecies are currently recognized.

OTHER COMMON NAMES

French: Vespertilion à couleur de paille.

PHYSICAL CHARACTERISTICS

Over most of its continental range, it occurs in two color phases: a light phase with a buffy back and a darker phase of reddish brown. The belly is lighter, but correspondingly tinted in each phase. The adaptive significance of this chromatic polymorphism is currently unclear. However, the populations show great fidelity to particular cave systems as roost sites. Since these may be quite isolated, this has resulted in some inter-population difference in coloration and average measurements. It is currently unclear if this reflects random drift or microevolution to precise local conditions. There is a black "moustache" of stiffer hairs above the upper lip and a white one below the lower lip. The natalid organ is bell-shaped and covers the entire muzzle. The specific name means "made of straw" and refers to the color of the body in the first-described subspecies, N. s. stramineus.

DISTRIBUTION

Northeastern Mexico (Baja California) to eastern Brazil, Cuba, Hispaniola, Jamaica, Lesser Antilles, and Tres Marias islands off western Mexico. Also known from fossil remains in cave deposits on the islands of Andros, Grand Caicos, and New Providence in the Bahamas, and Isle of Pines, near Cuba, and Grand Cayman Island south of Cuba. The New Providence deposit is some 8,000 years old; those on Andros are less than 4,500 years old.

HABITAT

Dry and seasonally deciduous forests, and gallery forests. Occasionally entering moister forest types.

BEHAVIOR

At higher altitudes, some populations may go into seasonal torpor.

FEEDING ECOLOGY AND DIET

Nothing is known.

REPRODUCTIVE BIOLOGY

Females migrate to special maternity roosts during the breeding season. Breeding occurs in the late dry season. Embryonic development is slow, with gestation lasting 10 months. Babies are proportionately large, weighing up to 0.07 oz (2.1 g) at birth, or more than 50% of the mother's weight. Thought to be polygynous.

CONSERVATION STATUS

Not threatened. The Cuban subspecies, primus, is known only from skeletal remains from Cueva de los Indios, Daiquiri, and is considered Extinct.

SIGNIFICANCE TO HUMANS

None known.

---

White-bellied funnel-eared bat

Natalus tumidirostris

TAXONOMY

Natalus tumidirostris Miller, 1900, Hatto, Curaçao.

OTHER COMMON NAMES

English: Trinidadian funnel-eared bat; French: Vespertilion à couleur de paille; German: Trichterohr.

PHYSICAL CHARACTERISTICS

Weight is 0.1 oz (3.3 g). Dorsally, a rusty brown; belly white; snout and lips pink; ears black outside, while pink with black rims inside.

DISTRIBUTION

Colombia, Venezuela, Suriname, Trinidad, and Curaçao. Sub-fossil remains have been found in caves on Andros, Cat, Great Exuma, and New Providence Islands in the Bahamas.

HABITAT

Roosts deep in caves.

BEHAVIOR

Roosts in caves, but a roost also recorded in a hollow rubber tree. Colonies reported from 100 to several thousand.

FEEDING ECOLOGY AND DIET

Has the slow fluttery flight of all natalids, reported to make a soft regular vocalization when hunting, audible to children, and described as sounding like a sewing machine. It uses the tail membrane to catch insects.

REPRODUCTIVE BIOLOGY

On Curaçao, young are born in October, at the start of the rainy season. This species is most likely polygynous.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

Species of the bacterial genus Borellia have been isolated from N. tumidirostris. B. recurrentis causes relapsing fever in humans; it is transmitted by the bite of insects and ticks from wild reservoirs such as bats and mice. The effects of the Borellia isolated from N. tumidirostris (if any) are not known. Many bats, including N. tumidirostris, have organisms associated with their guano, which cause disease in humans. These include several fungi, including Blastomyces dermatitidis, which causes blastomycosis (Gilchrist's disease, an infection of the skin, lungs, and lymph nodes). A species of yeast-like fungus, Candida chiropterorum has been found in the organs of several bat species, including N. tumidirostris.

---

Bahamian funnel-eared bat

Natalus tumidifrons

TAXONOMY

Natalus tumidifrons (Miller, 1903), Watling Island, Bahamas. This species has had an involved taxonomic history. It was originally described as a member of the genus Chilonatalus. This was re-designated as a subgenus of Natalus. Later, along with three other taxa, N. tumidifrons was considered to be a subspecies of N. micropus (N. m. tumidifrons). While it was recently re-elevated to species status, three other former species are now considered to be subspecies of N. micropus. It is the only bat endemic to the Bahamas. Fossils bones of N. tumidifrons, 8,000–12,000 years old from caves on Andros and New Providence, are indistinguishable from those of living animals.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Very similar in color and appearance to N. micropus, but has a larger forearm and body size.

DISTRIBUTION

Great Abaco and Watling (San Salvador) islands in the northern Bahamas. Formerly occurred on Andros and other islands in the southern Bahamas, as part of an extensive 16-species mammalian fauna (15 of which were bats). Though some human impacts from cave use may have occurred, the most significant impacts on ancient populations of this bat appear to have come from post-glacial changes in climate and sea level, which flooded many caves and disrupted the thermal ecology of most others. Most bat species that became extinct at this time were, like N. tumidifrons, species that prefer to roost deep in caves where the climate is hot, humid, and stable. N. lepidus appears in the fossil record in some islands of the Bahamas at the same time N. tumidifrons disappears, leading to suggestions that competition may have hastened its disappearance. N. tumidifrons now only occurs on islands from which N. lepidus is absent.

HABITAT

Occurs only in the Bahaman dry forest. The forest on Great Abaco is lusher and taller than that on Watling Island, which is low, scrubby, and with an understory of cacti.

BEHAVIOR

Nothing is known.

FEEDING ECOLOGY AND DIET

Nothing is known.

REPRODUCTIVE BIOLOGY

Mating system is not known, but most likely polygynous.

CONSERVATION STATUS

Vulnerable. It is one of three mammals endemic to the Bahamas. Of the other two, the Bahaman Raccoon (Procyon maynardi) is Endangered and the Bahaman Hutia (Geocapromys ingrahami) is Vulnerable.

SIGNIFICANCE TO HUMANS

None known.

---

Small-footed funnel-eared bat

Natalus micropus

TAXONOMY

Natalus micropus Dobson, 1880, Kingston, Jamaica. Sometimes placed in the subgenus Chilonatalus.

OTHER COMMON NAMES

English: Cuban funnel-eared bat.

PHYSICAL CHARACTERISTICS

With head and body length of 1.5 in (4 cm) and a weight of 0.7–1.0 oz (2–3 g), this is the smallest member of the family; it is also the smallest New World bat. Dorsal fur is pale yellow at the base and reddish or chestnut-brown at the tips. Belly hair is a uniform yellowish brown. The sexes are the same size. The lower lip is reflected outward and possesses a fleshy projection, giving the appearance that there are two lower lips. Characteristically, the natalid organ is rounded and located near the base of the muzzle. A small nub of flesh on the top of the nose resembles a rudimentary nose leaf.

DISTRIBUTION

Cuba, Isle of Pines, Jamaica, Hispaniola, and islands off east coast of Nicaragua. Subfossils are also known from several cave sites in Jamaica and on Cuba. These suggest there has been little chance in the appearance of this species since the Pleistocene. The population from Old Providence Island off the Nicaraguan coast is often given subspecific status as N. m. brevimanus. Other subspecies are N. m. macer from Cuba, and N. m. micropus from Jamaica. All of these subspecies have, at various times, been given species rank.

HABITAT

Prefers deep moist caves, where they roost in loose colonies of up to several hundred under low ledges. Some populations may enter summer torpor (estivation). One colony inhabits the St. Clair cave in Jamaica, an area of rugged relief surrounded by rainforest. It shares the cave with eight other bat species. When exiting, they fly within 3.2 ft (1 m) of the cave floor.

BEHAVIOR

Nothing is known.

FEEDING ECOLOGY AND DIET

Little known. Small, lightweight, and agile flyers, these bats are rarely caught in mist nets.

REPRODUCTIVE BIOLOGY

Mating system is not known, but most likely polygynous.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS

Biologists consider the genus to be of great interest in puzzling out how species evolve on islands and how biological communities have developed in the Caribbean.

---

Gervais' funnel-eared bat

Natalus lepidus

TAXONOMY

Natalus lepidus (Gervais, 1837), Cuba. Because of a relatively flattened braincase, a small natalid organ (situated in the middle of the muzzle), and an entire (not grooved) lip, this species is placed in the subgenus Nyctiellus.

OTHER COMMON NAMES

English: Butterfly bat; Spanish: Murcielago mariposa.

PHYSICAL CHARACTERISTICS

Forearm length is 1.0–1.3 in (2.7–3.4 cm). Fur yellowish with a buffy wash. Distinguished from N. micropus by the absence of the lip-like ridge on the chin and the lack of prominent hair-covered nodules on the snout.

DISTRIBUTION

Cuba, Isle of Pines, plus Cat, Eleuthera, and Great Exuma Islands in the Bahamas. Subfossils in cave deposits show it also formerly occured on Bahamian island of Andros, but that it arrived within the last few thousand years and was not among the old Pleistocene fauna of the Bahamas.

HABITAT

Cuban dry forest.

BEHAVIOR

An obligate cave dweller, this bat requires a warm humid cave environment and prefers caves not occupied by other bat species.

FEEDING ECOLOGY AND DIET

Nothing is known.

REPRODUCTIVE BIOLOGY

Mating system is not known, but most likely polygynous.

CONSERVATION STATUS

Lower Risk/Near Threatened.

SIGNIFICANCE TO HUMANS

Proudly promoted as "the world's smallest bat," a large N. lepidus colony in the Escambray range in south-central Cuba may be threatened by future tourism developments. Cuban dry forest (an umbrella term for a variety of plant communities) formerly covered 50% of the region; it is now 10% or less on most islands.

---

Resources

Books

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.

Periodicals

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

Organizations

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: <http://www.batcon.org>

Adrian A. Barnett, PhD