Chilonatalus macer Miller, 1914

Tejedor, Adrian, 2011, Systematics Of Funnel-Eared Bats (Chiroptera: Natalidae), Bulletin of the American Museum of Natural History 2011 (353), pp. 1-140 : 26-30

Chilonatalus macer Miller, 1914

Figure 14

Chilonatalus micropus: Miller, 1904: 340 . Not Natalus (Chilonatalus) micropus Miller, 1898 .

Chilonatalus macer Miller, 1914: 225 . Type locality Baracoa, Guantánamo, Cuba.

Natalus (Chilonatalus) macer: Dalquest, 1950: 443 . New combination.

Natalus micropus macer: Viña Bayés and Deas Díaz, 1970: 7 . New combination.

HOLOTYPE: USNM 113724, adult female, skin in alcohol with skull removed, collected by W. Palmer on 6 February 1902, ‘‘in a cave’’ (identified by Silva-Taboada, 1979, as Cueva de la Majana), Baracoa, Cuba. The skin has the tail membrane and both hind legs disconnected from the body. The skull is complete but has been apparently slightly compressed transversally, so that the zygomatic arches are asymmetrically buckled.

DISTRIBUTION: Cuba, Isle of Pines, Grand Cayman (fossil only); fig. 11.

DIAGNOSIS: Forearm short (32.1–33.8 mm); tibia long (18.2–20.25 mm); penis short (1.5–1.9 mm); natalid organ long (2.35–7.7 mm); greatest skull length (13.8–14.5 mm); least postorbital breadth relatively narrow; lateral margin of ear straight; attachment of wing to tibia on the proximal half of the tibia (at about 1/3 of its length, measured from the knee); in lateral view, braincase uninflated and rising from rostrum as a gently curving slope dorsal to orbit; ridge between basisphenoid furrows wide; caudal margin of ascending ramus of mandible forming a straight angle with alveolar plane of dentary; lateral sides of basisphenoid pits nearly parallel; p2 not crowded; fusion between original elements of thoracic cage seamless ventrally. A comparison of diagnostic characters between C. macer , and other species of Chilonatalus is summarized in table 4.

DESCRIPTION: Small size (forearm length 32.1–33.8 mm; greatest skull length 14.2– 14.9 mm; weight 2–4 g); muzzle long and dorsoventrally flattened; nostrils elliptical, opening ventrolaterally at the end of tubelike projections on margin of upper lip; upper lip slightly thickened; lower lip markedly thickened and constricted in dorsal and ventral margin, with numerous transversal grooves; small, smooth central pad on dorsal margin of lower lip; high dermal tubercle on dorsum of rostrum caudal to nostrils; tubercles of ramal vibrissae coalesced into transversal ridge ventral to lower lip; natalid organ very large (up to 1/2 of greatest length of skull), elliptical, and reaching crown of head; ears relatively long (12.7–16.4 mm); ear pinna very wide and funnel shaped; pinna with moderately pointed tip; lateral and medial margins of pinna straight; three very small ear ridges along lateral margin of distal pinna; ventral region of ear pinna greatly expanded, covering the eye and tragus in lateral view; medial ear margin thin and flexible; tragus markedly short, lanceolate, and twisted into helixlike structure; tibia (18.2–20.3 mm) longer than half the length of the forearm; calcar very long and thin, occupying about 2/3 of the length of the free edge of uropatagium; free margin of uropatagium with sparse fringe of thin hairs; wings relatively long and wide, with 3rd metacarpal (30.3–32.4 mm) longer than 5th metacarpal (27.9–30.5 mm); wings attach to tibia at proximal third of distance between knee and ankle; pelage dense and lax; hairs long (5– 8 mm, dorsally; 3–7 mm, ventrally); pelage color from light brown to orange brown, lighter dorsally; hairs bicolored, with tips darker than bases; dense mustachelike hair tufts along lateral margins of upper lip; mustache formed by dense, tough, parallel, and ventrally curved hairs; natalid organ nearly naked; skull long and narrow with moderate rostral flexion; rostrum long and narrow, with marked sulcus between nasals; moderate palatal emargination; maxilla con-

vex dorsal to molars; braincase greatly inflated, rising gently from rostrum; sagittal crest moderately developed; postorbital constriction relatively wide (42 % –44 % of zygomatic breadth); maxillary branch of zygomatic arch thin, less deep than twice the height of crowns of last molars; pterygoids convergent; palate extending caudally to half the length of pterygoids; basisphenoid pit deep and steep sided; longitudinal medial ridge on basisphenoid present; ectotympanic large, covering about half of the periotic; upper incisors long and pointed; occlusal profile of premolars long; upper premolars of similar size and not crowded; mesostylar crests on M1 and M2 long and broadly curved, mesostylar crest present on M3; cingular cusp of p4 long and pointed; molars cusps relatively broad; spinous process of humerus much higher than capitulum; thorax relatively short and wide; all ribs fused among each other and with sternum forming a single bell-shaped structure; vertebrae C7 to T7 fused among themselves and to ribs; vertebrae T11–L5 fused entirely without vestige of sutures; vertebrae L6 free; caudal vertebrae 4–7 longer than distance from ischium to iliac crest of sacrum.

COMPARISONS: Chilonatalus macer is easily distinguishable from species of the genus Natalus and from Nyctiellus lepidus by generic-level diagnostic characters: presence of dermal outgrowths on dorsum of rostrum and on chin, producing a double-lipped aspect; presence of three ear ridges; mandibular symphysis with long posteroventral projection; shaft of angular process curved dorsally and with a markedly hooked tip; and labial cingular cusp of p4 long and pointed. In the genera Natalus and Nyctiellus , the face lacks dermal outgrows, the ear shows ridges in various numbers, the mandibular symphysis shows a short (or absent) posteroventral projection, the mandibular angle may be pointed ( Nyctiellus ) or blunt ( Natalus ); and the labial cingular cusp of p4 is short or very little developed.

From the other two species of Chilonatalus , C. macer can be separated using a combination of external and cranial charac- ters. Externally, Chilonatalus macer differs from C. micropus in its straight lateral margin of the ear, the attachment of the wing on the proximal half of the tibia, a short penis (1.5– 1.9 mm), a long tibia (18.2–20.25 mm), and a large, elliptical natalid organ (length of natalid organ 2.35–7.7 mm). Chilonatalus micropus , in contrast, is characterized by a concave lateral ear margin, a wing attaching to the tibia on its distal half, a long penis (3.6–6.5 mm), a short tibia (14.7–17.95 mm), and a small, hemispherical natalid organ (length of natalid organ 3.3–3.7 mm). Cranially, C. macer and C. micropus can be separated by the dorsal flexion point of the skull (with a well-defined angle in C. micropus and a gently curving slope in C. macer ), the angle formed by the caudal margin of the ascending ramus of mandible with the alveolar plane of the dentary (straight in C. macer and about 70u in C. micropus ), the lateral sides of the basisphenoid pits (nearly parallel in C. macer and widely diverging caudally in C. micropus ), and by the fusion of the ribs with sternum (seamless in C. macer and retaining sutures in C. micropus ).

Chilonatalus macer does not differ appreciably from Chilonatalus tumidifrons in external characters. The easiest way to separate both species is by skull size (greatest skull length 13.8–14.5 mm in C. macer and 15.15–15.95 mm in C. tumidifrons . Also, the two species differ in the relative width of the postorbital constriction (42 % –44 % of zygomatic breadth in C. macer and 38 % –41 % in C. tumidifrons ), in the degree of crowding of P2 (not crowded in C. macer and crowded in C. tumidifrons ), and in the relative width of the ridge between basioccipital furrows (narrow in C. macer and wide in C. tumidifrons ).

VARIATION: In a sample of 12 males and 18 females the only measurement that showed sexual dimorphism in size was the length of the humerus ( Silva-Taboada, 1974). The species shows no geographic variation between western and eastern Cuba or between Cuba and the Isle of Pines.

NATURAL HISTORY AND CONSERVATION: Chilonatalus macer is known from 33 localities (including two represented by bone remains only), of which 22 are day roosts, and 19 are caves. On three occasions it has been found roosting solitarily in highly unusual conditions: (1) inside a house for drying tobacco; (2) inside a camping tent, and (3) on a sugarcane sappling. These occurrences suggest that occasionally some individuals are unable to return to their permanent roosts before sunrise.

Chilonatalus macer roosts in warm and humid caves (six of these have been hot caves) but it has also been found solitarily in cooler and drier caves. These bats generally form groups of 30–50 individuals in protect- ed areas of low ceilings, keeping a wide distance between individuals, which usually hang from a single foot. This species has been found coexisting in the same caves with 13 other bat species ( Artibeus jamaicensis , Brachyphylla nana , Eptesicus fuscus , Erophylla sezekorni , Macrotus waterhousii , Mormoops blainvillei , Monophyllus redmani , Natalus primus , Nyctiellus lepidus , Phyllonycteris poeyi , Pteronotus macleayi , Pteronotus parnellii , and Pteronotus quadridens ), but usually roosts separated from them ( Silva-Taboada, 1979). Nonetheless, C. macer has been found in close association with other species on two occasions: (1) apparently solitarily, within a colony of Pteronotus quadridens (Cueva del los Majáes, Tejedor et al., 2005a); and (2) in a small group contiguous with a large colony of Nyctiellus lepidus (Cueva del Calabazar, Tejedor et al., 2005a).

Chilonatalus macer is commonly found in mesic habitats having up to 2521 mm of annual precipitation (Baracoa, Cuba; locality 152), but is occasionally found in xeric environments (e.g., Cueva de los Masones, locality 154; annual precipitation of 834 mm). It has been found from sea level up to 230 m (Cueva del Indio; locality 106).

Very little is known of the food habits of C. macer . In Cuba it has been found to feed mostly on moths (Lepidoptera) and occasionally on spiders. It can carry in its stomach up to 28.6 % of its body weight (Silva- Taboada, 1979).

The reproductive pattern of C. macer is largely unknown. Two pregnant females found in May carried embryos measuring 10 mm in crown-rump length. Of two females taken in August, one was lactating and another postlactating. Reproductively inactive females have been found in January, March, and December ( Silva-Taboada, 1979). In May, in Cueva La Barca, Pinar del Rio, Cuba, sexes have been found forming separate groups, with females roosting deep in a hot area of the cave and males occupying a cooler area near a small entrance, suggesting a pattern of sexual segregation similar to that of N. lepidus .

Chilonatalus macer is represented by at least 123 specimens in museum collections, most of which were collected at Cueva No. 2 Punta del Este, and Cueva del Promontorio, both in Isla de la Juventud, Cuba. Colonies are relatively small, containing from a few dozen to a few hundred bats.

Natural predators are not known. Chilonatalus macer is parasitized by the streblid Trichobius frequens ( Silva-Taboada, 1979) .

The foraging exodus of C. macer has been recorded to begin 14 min after sunset and to last for over 30 min. Individuals returning to their roosts have been taken late at night (23:00 hr) indicating that these bats were active for long periods throughout the night ( Silva-Taboada, 1979). This species has an amazingly maneuverable flight. It is able to fly without hovering within reduced spaces (0.125 m 3) and is easily distinguishable inside caves by its rather rectilinear flight path and its very slow and shallow wing beat. Such slow, maneuverable flight, coupled with a small size, may enable this bat to forage in denser vegetation than most other Neotropical bats. It dehydrates and dies very rapidly if taken out of their caves during daytime.

It is is listed in IUCN’s Red List of Threatened Species (IUCN, 2010) as near threatened under Chilonatalus micropus . With the recognition of this taxon as a Cuban endemic different from Chilonatalus micropus , the study of its population status merits attention to accurately evaluate its conservation needs. Given its habit of aggregating in relatively small numbers in isolated and sparsely distributed colonies, its future IUCN category may increase in threat level.