Saccopteryx bilineata (Temminck)

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 : 37-40

Saccopteryx bilineata (Temminck)

VOUCHER MATERIAL: 11 females (AMNH *265963, *265965, *267058, *267060, *267377, *267379, *267842; MNHN *1995.847, *1995.848, *1995.849, *1995.850) and 11 males (AMNH *265962, 265964, *265966, *267057, *267064, *267374, *267378, *267840; MNHN *1995.851, *1995.852, *1995.853); see table 8 for measurements. One individual of unknown sex (AMNH 266977) was recovered from the crop of a bat falcon.

IDENTIFICATION: Descriptions and measurements of Saccopteryx bilineata from the Guianas and elsewhere were provided by Thomas (1904), Sanborn (1937), Goodwin and Greenhall (1961), Husson (1962, 1978), and Brosset and Charles­Dominique (1990). There is considerable disagreement concerning trinomial nomenclature. Thomas (1904) explicitly recognized only two subspecies, S. b. bilineata in northern South America (including Trinidad), and S. b. centralis in Central America. Subsequently, Sanborn (1937) argued that size variation in this species was continuously distributed and precluded delin­ eation of subspecies in the absence of other significant characters; in his revision, the names insignis, perspicillifer , and centralis were therefore regarded as strict synonyms of S. bilineata .

Although many authors have followed Sanborn’s (1937) opinion (e.g., Husson, 1962, 1978), others have not. Cabrera (1958), for example, recognized S. perspicillifer (from Trinidad) as a distinct species, and Goodwin and Greenhall (1961) later treated perspicillifer as a valid subspecies of S. bilineata . Most recently, Koopman (1994) recognized S. b. bilineata as ranging from tropical Mexico throughout Central America and tropical South America except northern Venezuela, Trinidad, and Tobago, and S. b. perspicillifer as occuring in northern Venezuela, Trinidad, and Tobago).

Recognition of perspicillifer as a taxon distinct from bilineata is apparently based entirely on size, with specimens from northern Venezuela, Trinidad (the type locality), and Tobago supposedly being larger and more robust than specimens from elsewhere in the Neotropics ( Miller, 1899; Goodwin and Greenhall, 1961). However, this putative geographic pattern is not supported by available data. Instead, our personal observations and data reported by Thomas (1904), Sanborn (1937), Husson (1962, 1978), and Brosset and Charles­Dominique (1990) indicate that specimens from eastern Ecuador, Guyana, Surinam, French Guiana, Brazil, and Bolivia exhibit similar forearm, skull, and dental measurements as specimens from northern Venezuela, Trinidad, and Tobago. Thus, although significant geographic variation may exist among some populations of Saccopteryx bilineata , none of the subspecies traditionally recognized by authors appear to be justified by the evidence at hand.

Our voucher material from Paracou conforms with previous descriptions of the species, and measurements fall within the range of size variation previously documented from the Guianas.

FIELD OBSERVATIONS: We recorded 34 captures (possibly including some recaptures) of Saccopteryx bilineata : 14 in ground­level mistnets, 11 in elevated mistnets, and 9 at roosts; additionally, 1 specimen was recovered from the crop of a road­killed Falco rufigularis (which had also eaten a specimen of S. leptura ). Of the 14 ground­level mistnet captures, 4 were made in well­drained primary forest, 2 in swampy primary forest, 3 in creekside primary forest, and 5 in manmade clearings. Six S. bilineata were taken in nets suspended 10–21 m over a narrow dirt road, two were netted 10–13 m over a treefall gap in creekside primary forest, and three were netted 7–10 m above the ground in the subcanopy of swampy primary forest. Six of our mistnet captures were made before dark, between 18:00 and 18:35 hours.

We found five roosting groups of Saccopteryx bilineata at Paracou. All of these occupied more­or­less vertical cavities (by contrast with the essentially horizontal chambers typically used by Cormura brevirostris and Peropteryx spp.) with not­quite­completely dark interiors (the roosting bats were usually just visible without illumination), but other roost characteristics differed. One roost was in a 2­m­high chimney, open above and below, formed by the fused buttresses of a large tree (fig. 3); another was in the semicylindrical basal opening of a central cavity that extended far up into the trunk of a much small­ er tree (fig. 21); two were in the open bases of hollow trees big enough for a grown man to stand inside; and the fifth was an open cleft, 12 m above the ground at its lowest point, in the trunk of another big tree (accessed by climbing a rope). Roosting groups that we were able to count varied from one to five individuals. Two individuals that we found roosting alone were both adult males. One group of five that we captured in its entirety consisted of two adult males, two adult females, and one juvenile.