LA SELVA-BRAULIO CARRILLO MAMMALS 99 



Fig. 77. Mantled howler monkey, Alouatta palliata. Photo by C. Thorington. 



and may be as high as 10 or 11. Lone individuals, which are usually males, are 

 seen occasionally. Troops that included juveniles were seen in February 1983 (eight 

 adults— three males, five females; two juveniles; and one infant), in April 1983 

 (three adults— one male, two females; one subadult female; one juvenile; and one 

 infant in natal yellow coat), and in May 1986 (three adults— two males, one female; 

 and one juvenile). Howler monkeys were observed eating the flower buds of Costilla 

 elastica in April 1982 and the leaves of Cecropia sp. in November 1982; both plants 

 are in the family Moraceae. In the late 1960's only one troop of howler monkeys 

 was known to occur on the La Selva property, but by 1980 two troops were regularly 

 heard. The late foreman of La Selva, Rafael Chavarria, commented that before 

 the 1953 yellow fever epidemic, howlers were extremely abundant along the Rio 

 Puerto Viejo. 



The biology of howler monkeys in Costa Rica was reviewed by Glander (1980, 

 1983). 



