Mount Pirri Isthmus Rat

The Mt. Pirri Isthmus Rat (Isthmomys pirrensis) is a species of rodent in the family Cricetidae.

Its natural habitat is subtropical or tropical moist lowland forests. It is found only in Panama. At the time of its discovery it was considered as the “most common rat of southeastern Panama” (Anthony 1916). Found only in the eastern region of Darien, I. pirrensis appears to be a relict species confined to the Panamanian side of the Serrania del Darien (Hershkovitz 1966). Its occurrence on the Colombian side of the Serrania has been suggested without documentation of specimens (Alberico et al. 2000; Cuartas-Calle and Muñoz-Arango 2003; Hall and Kelson 1958; Hershkovitz 1966). Localities for I. pirrensis indicated by museum records are in the eastern Panama state of Darien throughout the areas surrounding Mt. Pirre (=Pirri, 7° 51' 8 N, 77° 46' 24 W), Mt. Tacarcuna and the Tacarcuna Village (8° 10' 58 N, 77° 17' 3.5 W); however, no specimens are recorded from the low lying areas (<800m) that bisect these two ranges.

Although neotomine-peromyscine rodents have historically been the subject of systematic research, studies involving Isthmomys have generally excluded I. flavidus due to its rarity in museum collections and the unavailability of tissue samples for molecular analysis (Bradley et al. 2007; Bradley et al. 2004; Carleton 1973; Engel et al. 1998; Hill 1975; Stangl and Baker 1984). In addition, morphological and physiological studies involving I. flavidus (Carleton 1973, 1980; Hill 1975; Hooper and Musser 1964; Linzey and Layne 1974; Linzey and Layne 1969; Voss and Linzey 1981) utilized specimens from the Cerro Hoya locality which was originally proposed as a geographic race of I. pirrensis (Handley 1966).