Vampyressa (Metavampyressa) brocki Peterson, 1968

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 : 126-128

Vampyressa (Metavampyressa) brocki Peterson

VOUCHER MATERIAL: 6 females (AMNH *266311, *267471, *268566, *268567; MNHN *1995.1185, *1995.1186) and 1 male (AMNH *267184); see table 48 for measurements.

IDENTIFICATION: As currently defined ( Koopman, 1993), Vampyressa includes three subgenera and five species: Metavampyressa (including brocki and nymphaea ), Vampyressa (including melissa and pusilla ), and Vampyriscus (including bidens only). In part because of confusion in the literature regarding middorsal stripes in Vampyressa (see discussion below), unambiguous identifications must still be based on Peterson’s (1968) review, which included a key (subsequently reproduced by Lewis and Wilson, 1987). Information about specimens of V. brocki collected after 1968 can be found in Baker and Genoways (1972), Swanepoel and Genoways (1979), and Williams and Genoways (1980a). No subspecies of V. brocki are currently recognized (Koopman, 1994).

Our voucher material, apparently the largest series of Vampyressa brocki collected at a single locality, conforms in all respects with Peterson’s (1968) original description. Although our measurement data broadly overlap those previously reported for the species, some Paracou specimens are slightly smaller than any hitherto reported in the literature.

Peterson’s original description of Vampyressa brocki was not ambiguous, but discrep­ ant readings are current in the literature. Thus, Williams and Genoways (1980a) stated that V. brocki lacks a middorsal stripe, citing Peterson as their authority, whereas other authors have evidently interpreted Peterson to mean that a stripe is present in this species (e.g., Lewis and Wilson, 1987). Peterson (1968: 1) himself clearly stated that the holotype of brocki is ‘‘greyish brown above with a faint indistinct dorsal whitish stripe.’’ A diagrammatic character summary accompanying the original description (op. cit.: fig. 6), however, does not distinguish between the faint middorsal stripe of brocki and the much brighter markings of two other congeners ( nymphaea and bidens ).

Our Paracou vouchers have a middorsal stripe, but it is extremely faint and is visible only when the dry dorsal pelage is carefully brushed. The stripe is hard to see under any conditions because it is only slightly paler than the surrounding fur, and it becomes quite invisible when the fur is wet (precluding observation in alcohol­preserved specimens).

Because the dorsal stripe is hard to see, Vampyressa brocki externally resembles V. pusilla , with which it might be confused in the field. The latter species entirely lacks a dorsal stripe and shares several traits with brocki , including small size, two pairs of lower incisors, and absence of m3 ( Peterson, 1968). Characters that unambiguously distinguish brocki and pusilla include a suite of craniodental features (op. cit.), of which the most useful include: (1) form of the inner upper incisors (tapering to a point in brocki , bilobed in pusilla ), (2) shape of the anterior lower premolar (low­crowned and bladelike in brocki , with higher crown and spearlike anterior cusp in pusilla ), and (3) shape of the nasal aperture (with straight ventral border in brocki , V­shaped ventral border in pusilla ). The latter character is visible only on cleaned skulls, but the distinction is unambiguous and provides a means of unequivocally identifying old individuals with worn or broken teeth.

FIELD OBSERVATIONS: Of the seven Vampyressa brocki we captured at Paracou, four were taken in ground­level mistnets and three in elevated nets. One of the groundlevel captures was in well­drained primary forest, two were in creekside primary forest, and one was in a manmade clearing. The elevated net captures were made 17–21 m over a narrow dirt road.