Artibeus (Artibeus) jamaicensis Leach, 1821

Simmons, Nancy B. & Voss, Robert S., 1998, The mammals of Paracou, French Guiana, a Neotropical lowland rainforest fauna. Part 1, Bats, Bulletin of the American Museum of Natural History 237, pp. 1-219 : 98-102

Artibeus (Artibeus) jamaicensis Leach

Figures 38 , 39

VOUCHER MATERIAL: 23 females (AMNH *266322, *266331, *266333, *266334, *266335, *266336, *266337, *266338, *266344, *267998, *268503, *268505, *268508, *268528, *268529; MNHN *1995.1139, *1995.1140, *1995.1141, *1995.1142, *1995.1143, *1995.1144, *1995.1145, *1995.1146) and 12 males (AMNH *266321, *266332, *266341, *266345, *267202, *267999, *268502, *268504; MNHN *1995.1147, *1995.1148, *1995.1149, *1995.1150); see table 38 for measurements.

IDENTIFICATION: We follow Handley (1987) and Marques­Aguiar (1994) in regarding Artibeus jamaicensis as the senior synomym of A. planirostris (contra Lim and Wilson [1993] and Koopman [1993, 1994]). Descriptions and comparative measurements can be found in Goodwin and Greenhall (1961), Swanepoel and Genoways (1979), Koepcke and Kraft (1984), Handley (1987), Brosset and Charles­Dominique (1990), Lim and Wilson (1993), and Marques­Aguiar (1994). Although Husson (1962, 1978) provided a detailed account of ‘‘ Artibeus lituratus fallax ’’ (= A. jamaicensis ) from Surinam, his sample may have included specimens of both A. jamaicensis and true A. lituratus .

Between 10 and 13 subspecies of Artibeus jamaicensis (including planirostris ) are currently recognized (see Hall, 1981; Davis, 1984; Handley, 1987; Marques­Aguiar, 1994; Koopman, 1994), of which 5 occur in South America: A. j. aequatorialis (Pacific slope of the Andes from southern Colombia to northern Peru), A. j. hercules (eastern Ecuador and Peru), A. j. trinitatis (central Colombia and Venezuela north of the Orinoco), A. j. fallax (Venezuela south of the Orinoco throughout the Guianas, thence southward through central Brazil to Bolivia), and A. j. planirostris (eastern Brazil and Paraguay).

Our Paracou material conforms closely to published qualitative descriptions of Artibeus jamaicensis fallax , although we observed somewhat more variation in pelage color than previously described for Guianan specimens (see below). Measurements of our material fall within the range of variation previously reported by most authors for A. j. fallax, including specimens referred to A. planirostris by Lim and Wilson (1993).

Despite our best efforts to correctly identify large Artibeus in the field, subsequent museum study showed that we initially mis­ dentified 6 specimens (6%) out of 94 adults preserved as vouchers. While we never confused specimens of lituratus and obscurus , we initially misidentified one specimen of jamaicensis as lituratus , two specimens of jamaicensis as obscurus , and three specimens of obscurus as jamaicensis . All of our identification errors involved females. Most of our identification mistakes involved individuals somewhat larger or smaller than the species norm, or those with ambiguous pelage colors and facial markings. For example, most specimens of lituratus have much brighter facial stripes than those typical of jamaicensis , but we found some jamaicensis with bright stripes and some lituratus with pale stripes. We also found intraspecific variation in dorsal pelage color in all three species, with some individuals having blacker or browner fur than that reported as typical in the literature.

Unambiguous identifications of our vouch­ er material were ultimately based on the qualitative craniodental characters described by Handley (1987), Brosset and Charles­ Dominique (1990), and Marques­Aguiar (1994). In particular, Paracou specimens of Artibeus jamaicensis are uniformly distinguished by a broad postorbital region with poorly developed postorbital processes (fig. 38), and M3 is always present. By contrast, the postorbital region is always narrower (table 38) and the postorbital processes are well developed in our specimens of A. lituratus , which uniformly lack M3. Subsequent examination of our measurement data (table 38) showed that whereas mean values for external dimensions of jamaicensis are smaller than those of lituratus , these species have overlapping ranges of morphometric variation at Paracou.

Marques­Aguiar (1994) cited two pelage characters as particularly useful for distinguishing Artibeus jamaicensis from A. lituratus : (1) the dorsal surface of the base of the forearm is very sparsely furred (almost naked) in jamaicensis versus densely furred in lituratus ; and (2) the ventral fur is frosted (with white or pale gray) in adult jamaicensis , whereas lituratus has completely dark (unfrosted) ventral fur. Examination of our vouchers confirms that these traits are unambiguously diagnostic for jamaicensis and lituratus at Paracou. Unfortunately, we were not aware of these helpful identification criteria in the field.

Numerous cranial characters cited by Handley (1989) consistently separate Artibeus jamaicensis and A. obscurus , but these are obviously not useful in the field. Our morphometric data, however, indicate that jamaicensis and obscurus can be separated unambiguously (at least in French Guiana) on the basis of body weight, total length, and forearm length, in all of which dimensions obscurus is substantially smaller. As noted by Handley (1989), jamaicensis has shorter fur than obscurus , but at Paracou this difference is slight (7 mm versus 8–9 mm) and requires careful measurement to be useful for identification. Both taxa, in our judgment, have equally ‘‘soft’’ fur, contra Handley’s observations. Dorsal fur color is typically much darker in obscurus than in jamaicensis , but (as previously noted) we found enough overlapping variation in this character to compromise its usefulness in the field. Handley (1989: 450) also noted that obscurus has ‘‘fewer and smaller ornamental warts on [the] chin,’’ but we did not find this to be consistently true in our material. Most individuals of both species have the same number of chin papillae (nine small papillae arranged in a ‘‘U’’ around a larger central papilla), with considerable variation in papillary size.

As noted above, we suspect that Husson’s (1962, 1978) sample of ‘‘ Artibeus lituratus fallax ’’ was a composite of individuals properly referred to jamaicensis and lituratus . This conclusion is based on two observations. First, Husson (1962, 1978) reported that M3 was present in 26 of his 34 specimens, and absent in 7 specimens. By contrast, we found M3 to be uniformly present in jamaicensis and uniformly absent in lituratus , a pattern that was also observed by Brosset and Charles­Dominique (1990). Second, Husson (1962: table XX) provided measurements of 10 individuals, 9 of which fall within the range of variation that we observed for jamaicensis , but 1 of which does not. The latter individual (a female from the Stuttgart museum, SNM 686.1) was reported to have a postorbital breadth of 6.3 mm, a value falling well below the range of varia­ tion in our series of jamaicensis , but agreeing perfectly with our measurement data for lituratus .

FIELD OBSERVATIONS: We recorded 73 captures (possibly including some recaptures) of Artibeus jamaicensis at Paracou, of which 71 were in ground­level mistnets and 2 were in elevated mistnets. The 71 ground­level captures included 18 in well­drained primary forest, 38 in swampy primary forest, and 15 in creekside primary forest. The two elevated net captures were made 5–10 m above the ground in the subcanopy of swampy primary forest.

Figures

Fig. 38. Dorsal (A) and ventral (B) views of the skull of Artibeus jamaicensis (AMNH 266321; male) from Paracou. Dorsal (C) and ventral (D) views of the skull of A. lituratus (AMNH 267492; male) from Paracou. Note that jamaicensis has a broad interorbital region, small postorbital processes, and three molars, whereas lituratus has a narrower interorbit, better developed postorbital processes, and lacks M3. Scale bars = 10 mm.

Fig. 39. Lateral views of the skull and lower jaw of (A) Artibeus jamaicensis (AMNH 266321; male) and (B) A. lituratus (AMNH 267492; male). Scale bars = 10 mm.