Chilonatalus micropus

Geographic Range

Cuban lesser funnel-eared bats ( Chilonatalus micropus ) are found across Jamaica, though most frequently observed in three caves (Oxford, St. Clair, and Windsor). They have also been observed, though less abundantly, on Hispaniola (Dominican Republic and Haiti) and on the Colombian islands of San Andrés and Providencia.

• Biogeographic Regions
• neotropical neotropical
  • native native

• Other Geographic Terms
• island endemic island endemic

Habitat

Cuban lesser funnel-eared bats are obligate cave roosters, and have been found in 21 terrestrial caves of various sizes, though mostly in caves that are small and isolated. These caves tend to be warm, with high humidity, and relatively high concentrations of carbon dioxide and hydrogen sulfide. Cuban funnel-eared bats require an environment with fairly stable humidity. Though C. micropus appears to be able to tolerate variations in roost temperature, they have adapted to the warm environment of tropical caves, as this is the only habitat type with a sufficient and stable enough humidity. It is possible that the obligate cave roosting lifestyle of C. micropus has evolved due to the frequency of hurricanes in the Caribbean region, as cave roosting individuals would be more likely to survive a hurricane than exposed bats, such as those that dwell in trees.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• rainforest rainforest

• Other Habitat Features
• caves

Physical Description

Cuban lesser funnel-eared bats are perhaps the smallest of their genus. Records of adult male specimens collected reported weights ranging from 2.30 to 3.32 g, and adult female specimens collected had weights ranging from 2.80 to 2.88 g. The head-body length of C. micropus ranges from 38 to 45 mm, with a tail length ranging from 45 to 48 mm. Their hind legs measure 7 to 8 mm in length, with the tail extending as long as, or longer than the legs. The tail extends to the posterior end of the uropatagium, but never beyond this membrane. Forearms of C. micropus have been measured between 31.0 and 35.7 mm. Individuals from different regions vary in measurements, with Jamaican individuals measuring larger, on average, in most measurements taken. There is some degree of sexual dimorphism in the size of C. micropus , with females being described as larger. Lengths of female skulls, crania, forearms, and third metacarpals exceeded those of males, though males had larger and broader brain cases.

Individuals of C. micropus have a pelage that is fine and soft, but densely packed. Individual hairs are considered long, from 3 to 7 mm. The dorsal surface of Cuban lesser funnel-eared bats tends to appear pale brownish yellow, with bicolored hairs that are lighter at the roots, and darken to a reddish brown color at the tips. The ventral fur is often a slightly darker pale yellow brown, though both dorsal and ventral fur have been described as light greyish brown. Thicker hairs curve along the lateral edges of the upper lip and are "moustache-like" in appearance. Thin, sparse hairs occur along the posterior edge of the uropatagium.

All adult males of C. micropus have a rounded, glandular-like organ on their head. This organ is found in all species of, and only in the family Natalidae , and is most prominent in the Chilonatalus genus. The appearance and placement of this organ on the head is useful in distinguishing one species from another. In Cuban lesser funnel-eared bats this organ is nearly naked, hemispherical in shape, and medium to large sized, (approximately 2.5 mm diameter). This organ is found in Cuban lesser funnel-eared bats on the dorsal surface of the head, where the brain case meets the rostrum, between the eyes, and near the anterior bases of the ears. The function of this organ is not fully understood, though it does contain some sensory-like cells and is thought to have some kind of glandular function.

Many facial features used to describe C. micropus are common to the entire family or genus. In the genus Chilonatalus , the pararhinal glands on the anterior tip of the muzzle are relatively large and well developed, so much so that the projections form a primitive nose leaf-like structure that appears as a small, hairy projection on the dorsal tip of the snout and forces the nostrils forward. Nostrils open ventrolaterally in an elliptical shape. Despite the similarities found within the family and genus, facial features are important for distinguishing differences among Natalidae species. In Cuban lesser funnel-eared bats, the muzzle is tipped up, and the upper lip is slightly thickened. The lower lip is noteably thick, fleshy and well developed. Below the lower lip is a small, transverse, ridge-like projection, creating a distinguished "groove" below the mouth. This trait is present in some similar species, but is most pronounced in C. micropus .

The ears of C. micropus are large, and lack prominent ridges (3 subtle ridges may be visible). The pinnae are relatively long (11.4 to 15.0 mm) and funnel shaped, hence its common name. The tips of the ears are anteriorly truncated at a 30 degree angle relative to the posterior edge of the ear. The ear narrows laterally towards the distal end (more so than in other species of the same genus), resulting in concave pinnae with slightly pointed distal ends. The widened bases attach to the dorsal surface of the head along a curved margin, just above the eyes. The medial edge of each pinna is relatively straight, while the lateral edge presents as more concave, and is deeply notched. The conch is rounded and projects forward. The tragus is short and twisted in a helical form. Eyes are small and not prominent.

The skull of C. micropus is elongate with a narrow, dorsoventrally flattened rostrum that tips up at the distal end and is longer than that of other species of the genus. The brain case is rounded and rises abruptly from the rostrum. A sagittal crest is present, though poorly developed. The zygomatic arch is complete and thin. The skull length is less than that of other species within the genus, and has been recorded between 13.5 and 14.7 mm. Dentition varies to some degree between species within the genus and can be used as a distinguishing factor. Cuban lesser funnel-eared bats has 38 teeth and the dental formula is as follows: I 2/3 C 1/1 P 3/3 M 3/3. The upper incisors are long and pointed, with the two outer ones being either smaller, or of similar size relative to the inner ones. Upper incisors are paired, with a wide space between the pairs, and a separation from the canines. The lower incisors are well developed. The upper premolars are not crowned, and the first premolars are slightly smaller than the second. The molars have relatively broad cusps. The palatal region may also help to distinguish Cuban lesser funnel-eared bats from other species as it has nine palatal ridges, five of which are divided, while the remaining four are continuous across the palate.

The ribs of C. micropus are fused together, and fused to the sternum with sutures visible. The ribs and sternum come together to form a bell-shaped structure. Vertebrae C7 to T3 are fused, as well as those of T11 to L5. The location of the attachment of the wing membrane to the leg differs among species. In Cuban lesser funnel-eared bats, the wings attach to the legs where the middle and distal thirds of the tibia meet. The tibia is approximately half the length of the forearm. The wings of Cuban lesser funnel-eared bats are relatively long and wide, with a long, thin calcar that runs along two thirds of the edge of the uropatagium.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Research on the reproductive system and behaviour of C. micropus is lacking.

Individuals of the species possess 36 chromosomes (18 pairs) and may have low genetic variability. Genetic material does not differ greatly from other members of the genus. A precise breeding season and time to weaning is unknown, but lactation appears to end in July. This speculation is based on samples of females collected throughout July where up to 90% were lactating, as compared to a sample collected at the end of July that was entirely reproductively inactive. The species is known to have prominent nipples and mammary tissue in females, and long penises in males. The baculum is smaller than other members of the genus, and is slightly wider at the base than it is through the short, straight shaft. The tip of the baculum curves slightly downward.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Research on the reproductive system and behaviour of C. micropus is lacking. Like other bats, young of this species is cared for by mothers until independence.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female

Lifespan/Longevity

The generation length of C. micropus is listed as 5 years by the IUCN, but another source (Pacifici et al., 2014) declares the species specific generation length for Cuban lesser funnel-eared bats to be unknown, while noting an average generation length of 5.67 years for o.Chiroptera individuals of similar mass.

Behavior

Cuban lesser funnel-eared bats are an obligate cave roosting species. They roost in groups on the ceilings of caves, spaced about 7 to 10 cm apart. They seem to prefer recessed or protected areas, such as the undersides of ledges, though they have also been observed roosting in open areas of caves. Some groupings observed consisted of 10 to 20 individuals, while others were estimated to be up to several hundred. It is unknown why C. micropus is an obligate cave rooster, though a closely related species found in the same region, Natalus major , loses water to the environment easily through their thin wing membranes. This results in dehydration, which may explain why these species are restricted to humid caves.

In some instances, C. micropus has been observed roosting amongst other bat species, though the species tend to separate into aggregates of conspecifics when disturbed by humans. One observed group, seemingly disturbed by human presence, flew in close proximity to one another. It is speculated that this type of behavior may be an anti-predator response, though there is not enough information to definitively say that it is not a typical behavior of the species. Individuals have also been observed flying low, within one meter of the cave floor, and near the cave walls. Again, the presence of humans may or may not have affected their flying behavior. Additionally, Cuban lesser funnel-eared bats are a slow flyer relative to other bats, and are active at night.

• Key Behaviors
• troglophilic
• flies
• nocturnal nocturnal
• motile motile
• colonial colonial

Home Range

The home range of C. micropus is restricted to the island caves mentioned in the above sections on geographic range and habitat. There is no evidence at this time suggesting they leave their cave habitat for any extended period of time.

Communication and Perception

Cuban lesser funnel-eared bats are believed to use echolocation to navigate and perceive insect prey in their environment. It is likely that they do this with two frequencies between 40 and 80 kHz, though research in this area is limited.

• Perception Channels
• tactile tactile
• acoustic acoustic
• ultrasound ultrasound
• echolocation echolocation
• chemical chemical

Food Habits

While research is lacking in this area, there is evidence that C. micropus is an insectivore, like other members of the family Natalidae . Lysosome-like activity has been found in the salivary glands of Cuban lesser funnel-eared bats, which may function to breakdown chitin in the exoskeletons of insects consumed as food. Cuban funnel-eared bats are also known echo-locators, likely using harmonics to hunt for insects in the dark.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects

Predation

Information on predators is not reported in the literature. Nocturnal habits and selection of roosts in most bats is an effective form of anti-predation behaviour.

Ecosystem Roles

Cuban lesser funnel-eared bats have been observed roosting among groups of other bat species, and roosting separately with only conspecifics. Some species they have been found roosting with include Mormoops blainvillii , Pteronotus parnellii , Pteronotus macleayi , Macrotus waterhousii , Monophyllus redmani , Artibeus jamaicensis , Pteronotus fuliginosa , Erophylla sezekorni , Phyllonycteris aphylla , and Natalus major . It is unknown if C. micropus plays any significant role in the ecology of these groups, or the caves in which they reside. It is possible that Cuban lesser funnel-eared bats play some role in controlling insect populations, as they are thought to be insectivores.

Economic Importance for Humans: Positive

Cuban lesser funnel-eared bats may prove an enlightening mammalian research subject, particularly in the field of evolutionary biology due to its limited distribution and small size relative to other mammals. On Hispaniola, farmers collect bat feces from caves to use in manure based fertilizer, called guano. Some of the islands where C. micropus is found are popular tourism destinations, and recreational activities do occur within the caves where they live.

• Positive Impacts
• ecotourism ecotourism
• research and education
• produces fertilizer

Economic Importance for Humans: Negative

There are no known adverse effects of C. micropus on humans.

Conservation Status

The International Union for Conservation of Nature (IUCN) has listed C. micropus as vulnerable due to a decline in population of about 30% over three generations. Possible explanations for this decline include population isolation as well as a decline in critical habitat. Populations of Cuban lesser funnel-eared bats are fragmented across 4 islands, 2 of which are very small and near human populations which may be detrimental to the bats. Any threats posed to the caves where they live, respectively threaten the bats. Threats to caves include residential and commercial development, mining, tourism, recreation and feces collection by farmers. These activities may put stress on the species, disrupt its behavior, or degrade its habitat. Feral cats have also been known to feed on Cuban lesser funnel-eared bats in Jamaica, where the only known large population of the species exists. Extirpation of Natalidae from some Bahamian islands has been attributed to environmental changes resulting in loss of required microclimates.

Conservation efforts should focus on protecting the habitat of Cuban lesser funnel-eared bats. Protecting the caves where they reside is believed to be the best way to protect the species. More detailed research is needed to determine appropriate monitoring efforts and management strategies. This species has not been well researched despite the fact that they are known to exist in such large groups. Research efforts may have proven difficult for several reasons. There has not been a great deal of bat research in the geographic range of C. micropus . This may be party due to the hot humid conditions of the caves they are found in, which has been described as uncomfortable to humans. These bats are also very small and difficult to capture in mist nets, though they have been easily captured using hand nets. Lastly, they may have very narrow ecological requirements which may be hard to duplicate, making them difficult to keep live in captivity.

Other Comments

The phylogeny of C. micropus has been debated over the years. Chilonatalus was previously considered to be a subgenus within the genus Natalus , but it is now accepted to be its own genus, and sister taxa to the genus Natalus . The genus Chilonatalus is monophyletic, and contains three species: C. macer , C. tumidifrons , and C. micropus . The closest relative to Cuban lesser funnel-eared bats is C. tumidifrons .

The etymology of Natalus (the genus in which Cuban lesser funnel-eared bats were originally placed) is derived from a Latin word meaning "related to one's birth". This is presumably a reference to the small size of the bat, and their resemblance to newborns. The specific epithet, micropus, means "small foot".

Additional Links

Encyclopedia of Life

Contributors

Michelle Packer (author), University of Manitoba, Annemarie van der Marel (editor), University of Manitoba, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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