Mexican funnel-eared bat (Natalus stramineus)

The common name of this bat is something of a misnomer, as the Mexican funnel-eared bat (Natalus stramineus) is actually only found in the Lesser Antilles, West Indies ⁽¹⁾. This name results from the confusion surrounding the taxonomy of the Natalus genus, which has long been under scrutiny, although recent genetic evidence suggests there are at least eight distinct species ^{(1) (2) (3)}. These bats have slim, lightly built bodies with long and slender wings, legs and tail ^{(4) (5)}. Small, inconspicuous eyes sit behind the elongated muzzle and almost inside the ear and ⁽⁶⁾, as the common name suggests, the ears are large and funnel-shaped. The tragus is triangular shaped, while the males have a unique structure on the head called a ‘natalid organ’ that may have both sensory and glandular functions. The fur on these bats is soft and long, and is typically variable in colour, from grey and buff to yellowish, reddish or deep chestnut ⁽⁴⁾.

During the day, Mexican funnel-eared bats are typically found hanging independently from ledges despite being in caves in large groups ⁽⁶⁾. Shortly after sunset these bats emerge to hunt for their insect prey ^{(4) (5)}. They fly slowly and efficiently through the understory ⁽⁶⁾, but are capable of a great variety of impressive acrobatic manoeuvres ^{(4) (5)}. They find their prey using echolocation, whereby a series of noises, that are above the limit of human hearing, are emitted from the mouth or nose, and by listening to the returning echoes the bat creates a mental map of its surrounds. The insect is caught in the bat’s mouth during flight, and to restrain and trap the struggling prey, the bat will create an envelope with its wings and tail, preventing its escape ⁽⁴⁾. 

The timing of breeding in the Mexican funnel-eared bat is unknown, but the finding of a pregnant female in August in Guadeloupe suggests it is around this time. A single young is born each year after a relatively long gestation period of around eight to ten months, and for the first few months after birth the different sexes of juveniles may be segregated within the cave. These bats have a relatively slow reproduction rate, but this is offset by the fact that they live much longer than most mammals of a similar size ⁽⁴⁾. 

The Mexican funnel-eared bat inhabits islands in the Lesser Antilles north of the St Lucia channel, including Anguilla, Antigua, Barbuda, Dominica, Guadeloupe, Martinique, Marie Galante, Martinique, Montserrat, Nevis and Saba, and perhaps also Saint Maarten ⁽¹⁾.  

Roosting in dark, humid caves, the Mexican funnel-eared bat typically inhabits the most remote parts of the cave system, and forages within dry forest scrub, from sea level up to mid-elevations ⁽¹⁾.

The Mexican funnel-eared bat is classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

As the Mexican funnel-eared bat is believed to have a fairly large population, being locally common on at least four islands, and its habitat is not thought to be declining at a significant rate, it is not presently considered threatened with extinction. This bat’s cave habitat is however threatened by both mining and tourism activities and, like many other island inhabitants in the Caribbean, this species is vulnerable to the destructive effects of hurricanes and volcanic eruptions ⁽¹⁾.

In the absence of any significant threats to the species’ survival, the Mexican funnel-eared bat is not thought to be the target of any specific conservation measures. However, a future conservation priority for this species, and perhaps many other bat species with which it shares its habitat, would be to protect its roosting caves ⁽¹⁾.

ARKive is supported by OTEP, a joint programme of funding from the UK FCO and DFID which provides support to address priority environmental issues in the Overseas Territories, and Defra

For more information on conservation in Anguilla, Montserrat and St Kitts and Nevis:

• The Anguilla National Trust:
  http://www.axanationaltrust.org/
• The Montserrat National Trust:
  http://www.montserratnationaltrust.ms/
• The Nevis Historical and Conservation Society:
  http://www.nevis-nhcs.org/

To find out more about bat conservation:

• Bat Conservation International:
  http://batcon.org/
• The Bat Conservation Trust:
  http://www.bats.org.uk/
• The IUCN/SSC Bat Specialist Group:
  http://www.batconservancy.org/chiroptera-specialist-group-bat-conservation.php

Authenticated (25/02/11) by Dr Rodrigo Medellin, Co-Chair of the IUCN Bat Specialist Group,
http://www.batconservancy.org/chiroptera-specialist-group-bat-conservation.php and
http://www.ecologia.unam.mx/Laboratorios/rmedellin/

Echolocation

Detecting objects by reflected sound. Used by bats and odontocete cetaceans (toothed whales, dolphins and porpoises) for orientation and to detect and locate prey.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Gestation

The state of being pregnant; the period from conception to birth.

Taxonomy

The science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.

Tragus

A soft cartilaginous projection extending in front of the external opening of the ear. In bats, it plays an important role in filtering returning echoes in echolocation.

1. IUCN Red List (June, 2010)
   http://www.iucnredlist.org/
2. Tjedor, A. (2006) The type locality of Natalus stramineus (Chiroptera: Natalidae): implications for the taxonomy and biogeography of the genus Natalus. Acta Chiropterologica, 8: 361-380.
3. Wilson, D.E. and Reeder, M.D. (2005) Mammal Species of the World. A Taxonomic and Geographic Reference. The Johns Hopkins University Press, Baltimore.
4. Nowak, R.M. (1999) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore.
5. Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
6. Medellin, R. (March, 2011) Pers. comm.