Survey and census of howler monkeys (Alouatta palliata) in the rain forest of “Los Tuxtlas,” Veracruz,Mexico

Howler monkey troops were censused at the biological reserve “Los Tuxtlas” in Veracruz, Mexico. The reserve includes 700 ha of rain forest. Twenty howler monkeys were also trapped, measured, marked, and released. Censuses were conducted for a period of 26 months, and they indicated the existence of 17 troops. The mean troop size was 9.12 (SD ± 2.93), and mean troop composition was 3.0 adult males, 4.12 females, 1.56 juveniles, and 1.54 infants. Ecological density was 0.23 howlers/ha or 23.29 howlers/km². The male to female ratio was 1:1.37. No discrete seasonality in births was noted. Howler monkeys in this locality inhabit the northernmost limit of the neotropical rain forest. The population parameters fall within those reported for Alouatta palliata at other sites.