Chilonatalus micropus ( Dobson, 1880 )

Tejedor, Adrian, 2011, Systematics Of Funnel-Eared Bats (Chiroptera: Natalidae), Bulletin of the American Museum of Natural History 2011 (353), pp. 1-140 : 30-35

Chilonatalus micropus ( Dobson, 1880)

Figure 15

Natalus micropus Dobson, 1880: 443 . Type locality ‘‘Environs of Kingston, Jamaica.’’

Natalus (Chilonatalus) brevimanus: Miller, 1898: 328 . Type locality ‘‘Old Providence island, Caribbean Sea,’’ Colombia.

Chilonatalus micropus: Miller, 1907: 185 . New combination.

Chilonatalus brevimanus: Miller, 1907: 185 . New combination.

Natalus micropus brevimanus: Varona, 1974: 31 . New combination.

Natalus micropus micropus: Varona, 1974: 32 . Name combination.

HOLOTYPE: Holotype by monotypy, BMNH 80.12.14.1 collected in the ‘‘ Environs of Kingston, Jamaica.’’ Skull in good condition .

DISTRIBUTION: Hispaniola ( Dominican Republic), Jamaica, San Andrés and Providencia islands ( Colombia); fig. 11.

DIAGNOSIS: Forearm long (30.7–35.1 mm); tibia relatively short (14.7–17.95 mm); penis long (3.6–6.5 mm), natalid organ hemispherical and small (3.3–3.7 mm); least postorbital breadth relatively wide; lateral margin of ear deeply notched; wing attaches at the distal half of tibia (at about 2/3 of its length, measured from the knee); dorsal point of flexion between rostrum and braincase forming a well-defined angle dorsal to orbit; braincase globular and rising abruptly from rostrum; ridge between basisphenoid furrows wide, caudal margin of ascending ramus of mandible forming an angle smaller than 70u with alveolar plane of dentary; p2 not crowded; fusion between original elements of thoracic cage complete but with visible suture lines. A comparison of diagnostic characters between C. micropus , and other species of Chilonatalus is summarized in table 4.

DESCRIPTION: Small size (forearm length 30.7–35.1 mm; greatest skull length 13.5– 14.7 mm; weight 2.6 g); muzzle long and dorsoventrally flattened; nostrils elliptical, opening ventrolaterally at the end of short, 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; low dermal tubercle on dorsum of rostrum caudal to nostrils; tubercles of ramal vibrissae coalesced into transversal ridge ventral to lower lip; natalid organ small and hemispherical, located at intersection between rostrum and braincase; ears relatively long (13.0– 16.4 mm); ear pinna very wide and funnel shaped; pinna with moderately pointed tip; medial margin of pinna straight; lateral margin of pinna concave; 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 (14.7–17.9 mm) slightly short- er 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 (25.5– 33.5 mm) longer than 5th metacarpal (23.7– 30.2 mm); wings attach to tibia at about 2/3 the distance from knee to ankle; pelage dense and lax; hairs long (4–7 mm, dorsally; 3– 6 mm, ventrally); pelage color from light grayish brown to yellowish or reddish 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 concave dorsal to molars; braincase extremely inflated (globular), rising abruptly from rostrum; sagittal crest poorly developed; postorbital constriction relatively wide (41 % –45 % of zygomatic breadth); maxillary branch of zygomatic arch thin, as deep as 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 medium sized, covering about half of the periotic; upper incisors long and pointed; I1 similar in length to I2; 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; molar 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 bellshaped structure with sutures remaining among original elements; vertebrae C7 to T3 fused among themselves and to ribs; vertebrae T11–L5 fused entirely without vestige of sutures; vertebrae L6 free; caudal vertebrae 4 to 7 longer than distance from ischium to iliac crest of sacrum.

COMPARISONS: From species of the genera Natalus and Nyctiellus , Chilonatalus micropus can be distinguished on the basis of generic characters (see comparisons under account of Chilonatalus macer ). From other species of Chilonatalus (i.e., C. tumidifrons and C. macer ), C. micropus can be distinguished by several external and osteological characters. Externally, in C. micropus , the distal fourth of the ear is narrower than in the remaining species of Chilonatalus , leaving a concavity in the lateral margin of the pinna, which is absent in C. macer and C. tumidirostris . Also, the dermal tubercle above the nostrils is relatively low in C. micropus , whereas it is high and prominent in C. tumidifrons and C. macer . In C. micropus , the plagiopatagium attaches to the distal half of the tibia whereas in the other two species of Chilonatalus it attaches to the proximal half of the tibia. In addition, males of C. micropus have a relatively long penis (3.6–6.7 mm) and a small, hemispherical natalid organ, whereas males of C. tumidifrons and C. macer have a relatively short penis (penis length less than 2.5 mm) and a very large, elliptical natalid organ that in full development extends from the rostral tubercle to the crown.

Cranially, C. micropus is characterized by a globular braincase, which rises in a sharp angle from the rostrum. In C. macer and C. tumidifrons the braincase is relatively not as greatly inflated and rises from the rostrum in a gentler, sloping curve. Also, in C. micropus the caudal margin of the ascending ramus of the mandible is more concave and the shaft of the mandibular angle is thinner. In C. tumidifrons and C. macer the dorsal margin of the mandibular angle is deeper, rendering the caudal margin of the ascending ramus of the dentary less concave than in C. micropus .

In addition to the discrete characters mentioned above, C. micropus can be distinguished from C. tumidifrons on the basis of skull size alone (greatest skull length 13.5– 14.7 mm in C. micropus and 15.15–15.95 mm in C. tumidifrons ).

VARIATION: In C. micropus , females are larger than males in length of the forearm and 3rd and 5th metacarpals (Tukey, P, 0.05; table 8). Ottenwalder and Genoways (1982) showed that males are larger than females in depth of braincase and braincase breadth (the latter only true for Jamaican populations).

The inflation of the braincase decreases westward, with animals from Hispaniola having the most globular braincase within both the species and the family Natalidae (mean braincase breadth also follows this trend yet the differences were not statistically significant; P. 0.01; fig. 16). The depth of the rostrum, on the other hand, appears to decrease eastward with animals from Hispaniola having the most dorsoventrally flattened and slender rostra. Individuals from Jamaica were the largest in most external dimensions, with the exception of ear length (P, 0.01; fig. 16). In a larger sample, Ottenwalder and Genoways (1982) found the specimens from Old Providence to be the smallest (on average) in greatest skull length, breadth of braincase (males only) and maxillary tooth row (males only).

NATURAL HISTORY AND CONSERVATION: Species known from 21 localities of which eight have been day roosts, all of them caves. All caves known to harbor C. micropus are warm and humid, and at least five of these (Windsor, Oxford, Monarva, Los Patos, St. Clair) are medium-sized to large caves with hot sections ( Fincham, 1997). In St. Clair cave, C. micropus was found in the warmest areas, where the air was saturated with water vapor and had high concentrations of hydrogen sulfide ( Goodwin, 1970). It seems to favor protected areas inside caves such as high recesses ( Osburn, 1865), wall chambers ( Goodwin, 1970), or the underside of low ledges ( Kerridge and Baker 1978), where it has been found roosting in loose clusters. Genoways et al. (2005), however, observed C. micropus roosting out in the main passageway of St. Clair Cave. It coexists in caves with nine other bats species ( Artibeus jamaicensis , Erophylla sezekorni , Monophyllus redmani , Mormoops blainvillei , Natalus jam- aicensis, Phyllonycteris aphylla , Pteronotus macleayi , Pteronotus parnellii , and Pteronotus quadridens ). Osburn (1865; fide Genoways et al., 2005) observed C. micropus roosting separately from other species, but Goodwin (1970) found it in a mixed colony with Natalus jamaicensis , although he assumed the two species were segregated within the colony. When disturbed within caves, it retreats, flying near walls at about 1 m above the floor ( Kerridge and Baker, 1978).

Chilonatalus micropus occurs most commonly in mesic environments receiving up to 2899 mm in annual precipitation (Port Antonio, Jamaica; locality 247), from sea level to 400 m in elevation (Mahogany Hall Cave, Jamaica; locality 244). Its food habits are unknown, but as for other representatives of Natalidae , C. micropus is most certainly insectivorous. The reproductive pattern is also little known. Samples of females taken in mid-July have contained 2.6 % ( Genoways et al., 2005) to 90 % ( Kerridge and Baker, 1978) lactating individuals. Fourteen females taken on 29 July seemed to be reproductively inactive ( Genoways et al., 2005), suggesting that lactation may end during this month in Jamaica.

Chilonatalus micropus is represented by 335 museum specimens, with the largest samples having been taken in St. Clair cave ( Jamaica), Cueva los Patos ( Dominican Republic), and Old Providence Island. It is moderately gregarious at roosts, forming groups from 10–20 ( Genoways et al., 2005) to several hundred individuals ( Goodwin, 1970, Kerridge and Baker, 1978).

Nothing has been published on the activity patterns of C. micropus . In the Dominican Republic, one individual was netted at 20:00 hr apparently coming out of the upper entrance of Cueva los Patos, Barahona, 1.5 hours after the end of the exodus of six other bat species. A second individual was netted at 23:00, flying over a creek in Arroyo Chico, Samaná, Dominican Republic, indicating that the species is active until late at night.

Chilonatalus micropus flies very slowly and does not entangle in mistnets when caught in them. In an ecomorphological study, Obrist et al. (1993) predicted, based on dimensions of the ear pinna, that the echolocation calls of C. micropus probably consist of two harmonics in the 40–80 kHz range.

Chilonatalus micropus is listed in IUCN’s Red List of Endangered Species (IUCN, 2010) as near threatened, but this classification included the Cuban C. macer , which seems to be a more common species. Yu and Dobson (2000) considered it ‘‘very rare,’’ yet their conclusion was based on distribution and population data from Kerridge and Baker (1978), which stated that it was restricted to Jamaica. Chilonatalus micropus nonetheless appears to be more vulnerable than its current IUCN status indicates. The geographic range of this species is fragmented across four islands, two of which (San Andrés and Providencia) are very small, isolated, and with dense human populations. The only large population C. micropus in Jamaica is known from St. Clair Cave, where a resident population of feral cats is reported to feed on the cave’s bats ( McFarlane, 1986). On Hispaniola, where farmers traditionally engage in large-scale extraction of bat guano from caves, the only known roost site is Cueva Los Patos No. 2, a cave in the immediate vicinity of a small town. With such a limited known distribution and potential threats, the population status of this species warrants investigation to accurately assess its conservation needs.

Figures

Fig. 15. Holotype of Chilonatalus micropus (BMNH 80.12.14.1, ‘‘environs of Kingston,’’ Jamaica). Scale bar 5 5 mm.

Tables

TABLE 8 Summary of measurementsa of Chilonatalus micropus

		Females					Males
	N	Mean	(Min.–Max.)	SD	N	Mean	(Min–Max.)	SD
Weight	1	3	– –	–	2	–	(2.6–5.0)	–
Forearm length*	34	33.8	(32.1–35.0)	0.8	56	33.2	(30.7–35.1)	0.9
Length of tibia, dry	3	15.8	(15.3–16.2)	0.5	6	15.8	(14.7–17.2)	1.0
Length of tibia	30	16.6	(15.1–17.9)	0.7	50	16.4	(14.7–17.8)	0.7
Length of 3rd metacarpal*	33	30.9	(28.9–33.5)	0.8	48	30.1	(25.5–31.9)	1.2
Length of 5th metacarpal*	33	28.2	(26.6–30.2)	0.9	47	27.4	(23.7–29.2)	1.1
Length of ear	14	14.7	(13.0–16.4)	1.0	23	14.8	(13.0–16.1)	0.9
Length of penis		–	– –	–	43	4.8	(3.6–6.5)	0.8
Length of natalid organ		–	– –	–	33	3.2	(2.1–4.3)	0.6
Greatest skull length	6	14.1	(13.9–14.2)	0.1	19	14.1	(13.5–14.7)	0.3
Zygomatic breadth	6	6.5	(6.3–6.7)	0.1	17	6.5	(6.2–6.8)	0.2
Braincase breadth	6	6.0	(5.8–6.2)	0.1	19	6.0	(5.7–6.5)	0.2
Breadth across molars	6	4.3	(4.1–4.4)	0.1	18	4.3	(3.8–4.5)	0.2
Breadth across canines	5	3.1	(3.0–3.2)	0.1	17	3.1	(2.8–3.4)	0.2
Maxillary tooth row	7	5.8	(5.7–5.9)	0.1	19	5.8	(5.6–6.0)	0.1
Mandibular tooth row	7	6.2	(6.0–6.3)	0.1	19	6.1	(5.8–6.3)	0.1
Postorbital breadth	7	2.7	(2.5–2.9)	0.1	19	2.8	(2.5–3.0)	0.1
Depth of braincase	6	5.0	(4.8–5.5)	0.2	17	5.1	(4.8–5.4)	0.2

a Descriptive statistics of measurements for each sex. N 5 sample size; SD 5 standard deviation. Weight is given in g; all other measurements are given in mm. See text for description of measurement methods. Measurements significantly different between sexes (P # 0.05) are followed by an asterisk (*).