Sturnira lilium (E. Geoffroy)

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 : 119-124

Sturnira lilium (E. Geoffroy)

Figures 48–50

VOUCHER MATERIAL: 19 females (AMNH *266210, *266226, *266231, *266234, *266235, *266236, *267170, *268543, *268546, *268549, *268552, *268553; MNHN *1995.1197, *1995.1198, *1995.1199, *1995.1200, *1998.600, *1998.601, *1998­.602) and 35 males (AMNH *266199, *266200, *266201, *266203, *266205, *266206, *266207, *266224, *266225, *266227, *266228, *266230, *266232, *266233, *266237, *266238, *267197, *268544, *268545, *268547, 268548, *268550, *268551; MNHN *1998.603, *1998.604, *1998.605, *1998.606, *1998.607, *1998.608, *1998.609, *1998.610, *1998.611, *1998.612, *1998.613, *1998.614); see table 45 for measurements.

IDENTIFICATION: References that we found useful for distinguishing the smaller species of Sturnira include Goodwin and Greenhall (1961), Husson (1978), Davis (1980), and Gannon et al. (1989). Other descriptions and comparative measurements of S. lilium can be found in Taddei (1975b), Swanepoel and Genoways (1979), and Brosset and Charles­ Dominique (1990). Six subspecies of S. lil­ ium are currently recognized, of which the nominate form occurs thoughout tropical South America east of the Andes, including the continental islands of Trinidad and Tobago (Koopman, 1994).

Our voucher material generally conforms with published descriptions and measurements of Sturnira lilium , although a few Par­ acou specimens are slightly smaller than any previously reported from the Guianas. As noted by previous authors (e.g., Peterson and Tamsitt, 1968), the presence and development of ‘‘epaulettes’’ (patches of shoulder hairs stained dark brown by glandular secretions) varies in both sexes, with epaulettes present in virtually all older adults in our series but faint in some younger adults; subadults (with grayer pelage than the yellowgray adults) frequently lack epaulettes. The same ontogenetic patterns of pelage variation occur in S. tildae , which occurs sympatrically with S. lilium at Paracou.

In the field we had some difficuly distinguishing Sturnira lilium from S. tildae ; most of our problems involved subadults, very old animals, and a few individuals that fell near the zone of species overlap in size (table 45). We found no consistent pelage differences to distinguish these species. Although Goodwin and Greenhall (1961: figs. 55, 56) illustrated incisor differences between lilium and tildae that we found helpful for field identification, this character is not 100% reliable. Incisor morphology can be misleading in older individuals with worn teeth, and we found cases in which the incisors were morphologically intermediate to the conditions suppos­ edly diagnostic of lilium and tildae . Out of 79 specimens of Sturnira that we identified in the field using incisor morphology, we misidentified 1 female lilium as tildae and 1 female tildae as lilium , an error rate of 2.5%.

A more useful character for distinguishing Sturnira lilium and S. tildae in the field, one that we ‘‘discovered’’ only late in our study, is morphology of the lingual cusps on m1 and m2 (fig. 50). In our material, the lingual cusps on m1 and m2 are always tall and separated by a deep vertical notch in lilium , whereas tildae always has lower cusps separated by a shallow notch lacking vertical edges. On cleaned cranial material, this contrast is best seen when viewing the toothrow medially from below (i.e., tilting the lower jaw and viewing from underneath the opposing ramus, as in fig. 50). With a little experience, however, cusp morphology is also readily apparent when looking into a living animal’s mouth. Morphology of the lingual cusps was dismissed as a useless character by Marinkelle and Cadena (1971: 237), who assumed that previous descriptions noting this distinction between lilium and tildae (e.g., Hill, 1964) were based on specimens of the latter taxon with ‘‘unusually worn teeth.’’ However, we found this character to be useful even in older individuals: in our material there is little evidence of wear on the lingual cusps of the lower molars in any specimens. Morphology of the lingual cusps on m1 and m2 is strongly correlated with other diagnostic traits and, at least in the Guianas, it appears to be a reliable field character for separating lilium and tildae (for similar observations on Surinamese material, see Genoways and Williams, 1979).

Given the preceding observations, we cannot account for the small specimens of Sturnira ‘‘ tildae ’’ that Brosset and Charles­Dominique (1990: 536) reported as having lower molar lingual margins with ‘‘the serrated condition’’ (i.e., with tall cusps separated by deep vertical notches). If the specimens in question are not, in fact, referable to S. lilium , then a third species of Sturnira (hitherto unsuspected in the Guianas) may be present in their material. For additional comments on this problem, see the account for S. tildae (below).

After confirming identifications of our specimens by the qualitative characters reported in the literature cited above, we found that Sturnira lilium and S. tildae broadly overlap at Paracou in all external measurements except forearm length. All specimens with forearm length ≤ 44.0 mm in our series were found to represent lilium and all individuals with forearms ≥ 45.0 mm proved to be tildae . Specimens with forearm measurements between 44.0 and 45.0 mm included representatives of both species. Because we measured the forearms of most of the Sturnira that we released in the course of our fieldwork, we were able to make retrospective identifications from these data if other identification criteria were ambiguous or unrecorded. However, a few unvouchered capture records remain identified only as ‘‘ Sturnira sp.’’

FIELD OBSERVATIONS: We recorded 83 captures (probably including some recaptures) of Sturnira lilium at Paracou, all in ground­level mistnets. One capture was in well­drained primary forest, 1 was in swampy primary forest, 6 were in creekside primary forest, 74 were in manmade clearings, and 1 was over a roadside puddle. Of all the bats we captured at Paracou, S. lilium was the species most strongly associated with the early­successional vegetation bordering roads, gardens, and oth­ er artificial openings in the forest.

Figures

Fig. 48. Dorsal (A) and ventral (B) views of the skull of Sturnira lilium (AMNH 266232; male) from Paracou. Dorsal (C) and ventral (D) views of the skull of S. tildae (AMNH 267461; male) from Paracou. Note the species differences in incisor morphology, size and shape of the molars, and relative breadth of the mesopterygoid fossa and mastoid region. Scale bars = 10 mm.

Fig. 49. Lateral views of the skull and lower jaw of (A) Sturnira lilium (AMNH 266232; male) and (B) S. tildae (AMNH 267461; male). Scale bars = 10 mm.

Fig. 50. Oblique view of the lower jaw of (A) Sturnira lilium (AMNH 266232; male) and (B) S. tildae (AMNH 267461; male). Note the different morphologies of the lingual cusps on the molar teeth: lilium is characterized by tall lingual cusps that are separated by a deep vertical notch on m1 and m2; by contrast, these cusps are lower and separated by shallower notches in tildae. Scale bars = 10 mm.