16 NORTH AMERICAN FAUNA 75 



Chironectes minimus 

 Water Opossum, Zorro de Agua 



Water opossums are found from southern Mexico south through Central 

 America to the Amazon and Orinoco river basins in South America (Fig. 5). One 

 subspecies, Chironectes minimus panamensis, is found throughout the wet tropical 

 lowlands of Costa Rica, although few specimens exist. Water opossums are found 

 at least as high as 1,300 m in Costa Rica although their numbers and distribution 

 have been reduced due to the degradation in quality of many streams. The biology 

 of this species was reviewed by Marshall (1978). 



One C. minimus was observed swimming in the Rio Cantarrana near the 300-m 

 base camp in April 1986, and another was seen in the same area in January 1983 

 (Pringle et al. 1984). Water opossums have been reported only seven times at La 

 Selva between February 1979 and August 1988. 



Specimen examined (1)— Puerto Viejo, Rio Sarapiqui, 300 ft [1 male, UMMZ]. 



Didelphis marsupialis 

 Southern Opossum, Zorro Pelon or Zarigiieya 



The southern opossum is widespread throughout the Central and South Ameri- 

 can lowlands (Fig. 6). In Costa Rica it is found country-wide except at higher eleva- 

 tions in the Cordillera Central and the Talamanca Mountains. In a revision of the 

 Didelphis of Central and North America, Gardner (1973) recognized only a single 

 subspecies of D. marsupialis from Mexico and Central America, D. m. caucae. 

 Hall (1981), however, listed six subspecies of D. marsupialis from Central America, 

 recognizing D. m. richmondi from extreme southeastern Nicaragua and northeastern 

 Costa Rica in addition to D. m. caucae from the rest of the country. We concur 

 with Gardner that D. m. richmondi is not a distinct subspecies, and that all D. mar- 

 supialis from Costa Rica should be considered D. m. caucae. The biology of 

 D. marsupialis was reviewed by Gardner (1983a). 



We saw opossums on numerous occasions at 200, 300, 680, and 750 m, 

 although most often at 680 m. They are reported frequently near the La Selva 

 Biological Station. In July 1974 we found an adult female opossum with five pouch 

 young near the La Selva field station, on 3 July 1986 an adult female and four 

 young were observed there, and on 8 July 1988 an adult female and two young 

 were observed. Vaughan captured D. marsupialis at least 15 times at La Selva 

 in live traps baited with chickens, meat, and fish and set for small wild felids in 

 1984-85. In this area, opossums are found in both forest and clearings. Pringle 

 et al. (1984) reported D. marsupialis near their Cantarrana base camp in Parque 

 Nacional Braulio Carrillo at 300 m in June of 1983. 



External measurements for two adult males and one adult female we captured 

 are as follows: total length, 790 mm, 840 mm, 818 mm; length of tail, 401 mm, 

 460 nmi, 416 mm; length of hind foot, 67 mm, 65 mm, 67 mm; height of ear 

 from notch, 54 mm, 55 mm, 55 mm. Testes on the two males measured 22 x 12 mm 

 and 19x11 mm. 



