120 



NORTH AMERICAN FAUNA 75 



Oryzomys caliginosus 

 Dusky Rice Rat, Raton Arrocera 



Dusky rice rats are found from extreme eastern Honduras and Nicaragua to 

 western Ecuador (Fig. 94). In Costa Rica the subspecies Oryzomys caliginosus 

 chrysomelas is found at lower elevations. The biology of dusky rice rats was 

 reviewed recently by Gardner (1983b). 



The mean litter size, as judged by counts of embryos and recent placental scars, 

 of three females was 3.0 (Table 2). Mean testes length and width for nine adult 

 male O. caliginosus was 10.2x5.8 mm. 



A single adult female Ixodes venezuelensis was found on O. caliginosus. 



Specimens examined (41)— Finca La Selva, 3 km S of Puerto Viejo [1 male, 

 UMMZ]; Parque Nacional Braulio Carrillo [1 male, 1 female, UNA]; Puerto Viejo, 

 Rio Sarapiqui, 300 ft [5 males, 4 females, FMNH; 1 male, 1 female, LACM; 



1 sex ?, UNA]; 1.7 mi S of Puerto Viejo [1 male, LACM]; 4.4 mi S of Puerto 

 Viejo [1 male, LACM]; 5.7 mi S of Puerto Viejo [1 male, LACM]; 11 km S, 

 4.5 km W of Puerto Viejo, 260 and 280 m [7 males, 5 females, FMNH; 1 male, 



2 females, UNA], IkmS, 11.5kmEof San Miguel, 680 m [4 males, 4 females, 

 FMNH]. 



Fig. 94. Dusky rice rat, Oryzomys caliginosus. Photo by B. L. Clauson. 



