Philander opossum (Linnaeus)

VOSS, ROBERT S., LUNDE, DARRIN P. & SIMMONS, NANCY B., 2001, The Mammals Of Paracou, French Guiana: A Neotropical Lowland Rainforest Fauna Part 2. Nonvolant Species, Bulletin of the American Museum of Natural History 2001 (263), pp. 1-236 : 61-64

Philander opossum (Linnaeus)

VOUCHER MATERIAL: AMNH 266379–

266381, 266383–266387, 266389–266391,

TABLE 14 Measurements (mm) and Weights (g) of Adult Philander opossum from French Guiana and Surinama

266394, 266395, 266398, 266400, 266994, 266995, 266997–266999, 267014, 267328; MNHN 1995.915 – 1995.924 . Total = 32 specimens .

IDENTIFICATION: The species­level taxonomy of Philander was recently reviewed by Hershkovitz ( 1997) and by Patton and da Silva ( 1997), whose taxonomic conclusions differ considerably. Both studies, however, referred Guianan populations of gray four­eyed opossums to P. opossum , the type locality of which (as restricted by Matschie, 1916) is Paramaribo, Surinam. Our Paracou vouchers agree closely with Husson’s (1978) description of topotypic specimens of P. opossum in most details, but a few discrepancies merit comment. (1) Whereas Husson described the pelage of his topotypes as usually distinctly darker middorsally than on the sides, only one skin from Paracou (AMNH 266995) has fur that is slightly darker middorsally than on the sides; the rest of the adult and subadult skins from Paracou are a uniform grizzledgray over the entire dorsum. (2) Husson (1978: 25) described the fur of the head as ‘‘of the same dark blackish­brown colour as the median part of the back or even slightly darker’’, but the blackish fur of the head contrasts conspicuously with the grizzled­gray back in all adult and subadult Paracou skins, even the aforementioned example with dark­ er middorsal fur. (3) Husson (1978: 26) described the ears as ‘‘whitish with a broad black rim’’, but the ears of our Paracou specimens are only whitish at the base—most of the pinna is black. (4) Husson’s juvenile specimens were described as darker than adults and with less distinct facial markings, but three juvenile skins from Paracou (AMNH 266385, 266391, 266997) are comparable to those of adults and subadults except in pelage texture (the juvenile fur is softer).

Although most of the Surinamese material we borrowed for side­by­side comparison are darker middorsally than on the sides, as Husson described, a few (e.g., CM 52735) are uniformly gray like our Paracou vouchers. The other external differences implied by Husson’s description are not apparent in the Surinamese material we examined. 10 Cranial measurements of adult females from Paracou

10 Some color variation among the series at hand may be artifactual. For example, the blackish color of the crown of the head probably fades with age (becoming dusky­brown on old skins), and dark­tipped dorsal hairs may be more concentrated in the midline of flat skins than on round skins.

and Surinam overlap broadly (table 14), but our few adult males seem exceptionally large. We did not see any consistent qualitative craniodental differences between Surinamese and Paracou specimens.

Patton and da Silva (1997: 98) characterized the phenotype of Philander opossum as ‘‘uniformly pale­gray’’, a description that better fits our Paracou material than it does the Surinamese topotypes we examined. However, Patton and da Silva’s context for taxonomic comparisons included the almost entirely black P. mcilhennyi , as well as the black­striped P. andersoni , both of which contrast strikingly with predominantly grayish animals that those authors referred to P. opossum and P. frenata .

According to Hershkovitz (1997: 39), both gray and ‘‘brown’’ color phases occur throughout the range of P. opossum . We examined the Surinamese specimens that he cited as coat­color exemplars, however, and did not observe any consistent differences between gray and ‘‘brown’’ individuals (e.g., between FMNH 95312 and 95313, both collected by H. A. Beatty in the Wilhelmina Mountains). Yellowish or brownish tints do occur in some Philander skins, but whether these represent true coat­color variants rather than preservational artifacts (e.g., staining by sebaceous secretions or subcutaneous fat) is difficult to determine with the material at hand.

Both Patton and da Silva ( 1997) and Hershkovitz ( 1997) referred French Guianan populations of Philander opossum to the nominate form P. o. opossum , a usage consistent with the results of our comparisons. According to these authors, the nominate race occurs throughout the Guianas and the eastern Amazon basin of Brazil, and differs from other subspecies principally by geographic variation in size and pelage color. However, whereas Patton and da Silva recognized four species of Philander (see above), Hershkovitz recognized only P. opossum (including frenata among other subspecies) and P. andersoni (including mcilhennyi as a subspecies). We follow Patton and da Silva in recognizing the gray foureyed opossum of the Brazilian Atlantic forest as a distinct species, P. frenata , and we interpret their phylogenetic analysis of mtDNA sequences as evidence that additional taxa currently treated as subspecies of P. opossum (e.g., canus and fuscogriseus) might also be recognized as full species. However, many nominal taxa were not represented in Patton and da Silva’s molecular analyses, and several important issues of species­level synonymy remain unresolved. Therefore, the geographic limits of P. opossum are still uncertain.

REMARKS: We agree with Hershkovitz (1976, 1981) that Philander , not Metachirops , is the correct name for pouched foureyed opossums (contra Husson [1978] and other authors). Linnaeus’s (1758) original description of Didelphis opossum was based on an adult male and an adult female described and figured by Seba (1734). Hershkovitz (1976: 297) designated Seba’s female as the lectotype, but the specimen itself was apparently not then known to have survived the breakup and dispersion of Seba’s museum (for the history of which, see Boeseman, 1970). Hershkovitz ( 1997) subsequently stat­ ed that the lectotype is still preserved as an alcoholic specimen in the Rijksmuseum van Naturlijke Historie in Leiden. 11 According to the current RMNH curator of mammals (C. Smeenk, personal commun.), the lectotype is RMNH 25421, clearly recognizable as the adult female with three pouch young illustrated and described by Seba.

OTHER SPECIMENS EXAMINED: Surinam — Coronie, Totness (CM 52731, 52733); Marowijne, Moengo (CM 52734), Perica (CM 76736); Nickerie, Avanavero (CM 68363), Kayserberg Airstrip (FMNH 93168), Sipaliwini Airstrip (CM 63517, 76739), Wilhemina Mountains (FMNH 95312, 95313); Para, Zanderij (CM 68365, 76742); Saramacca, Bigi Poika (CM 52735), La Poule (FMNH 95309); Suriname, Clevia (FMNH 95310), Lelydorpplan (FMNH 95308), Plantation Clevia (CM 76743, 76744), Powakka (CM 52741, 52742).

FIELD OBSERVATIONS: In addition to data accompanying our 32 voucher specimens, we recorded 18 unvouchered observations of

11 Hershkovitz ( 1997) gave no catalog number for the lectotype, and the caption to his (op. cit.) figure 21 confusingly refers to the ‘‘Male and female lectotypes [sic] of Didelphis opossum Linnaeus (1758) ’’. The caption is an obvious lapsus that does not affect the validity of his earlier (1976) selection of the female as lectotype. Seba’s male specimen is therefore a paralectotype.

Philander opossum at Paracou, for a total of 50 documented records of this species. Of our vouchers, 21 (66%) were shot, 5 (16%) were taken in Conibear traps, 3 (9%) were taken in Sherman live traps, 1 was taken in a Tomahawk wire live trap, and 1 was taken in a Victor snap trap, and 1 was caught by hand. One juvenile captured in a pitfall trap and another taken in a Sherman trap were released. Of all 50 records, 31 (62%) were of individuals shot, trapped, or sighted on the ground, whereas 19 (38%) were of individuals shot, trapped, caught by hand, or sighted in trees (or on other elevated substrates such as inclined trunks, lianas, etc.) from 1.5 to 6 m above the ground. With the exception of females carrying nursing young, all P. opossum that we encountered were solitary, and all were collected or sighted at night. Of 49 records accompanied by habitat data, 32 (65%) were of individuals encountered in primary forest, usually near streams or in swamps, but occasionally at well­drained sites; 17 observations (35%), however, were based on individuals encountered in roadside secondary growth or other more­or­less disturbed habitats.

One female, collected on 9 July 1991, had two pouch young measuring 49 mm crownrump; another, collected on 24 October 1992, had three pouch young measuring 24 mm; and a third, collected on 11 August 1993, had four pouch young measuring 27 mm.

XENARTHRA

Nine xenarthran species have been definitely recorded from Paracou and it is unlikely that any others occur locally (see appendix 1). Because most xenarthran species are easily recognized by external characters (Husson, 1978; Emmons, 1990, 1997), we collected few vouchers.

Bradypus tridactylus Linnaeus Three­toed sloths are possibly common at Paracou, but they are seldom seen and we did not encounter any in the course of our fieldwork. P. Petronelli (personal commun., 1993) estimated that the species is sighted about once or twice a year at Paracou, much less frequently than two­toed sloths (see below).