Mr. Clarke et al., INFANT-NONMOTHER INTERACTIONS OF FREE-RANGING MANTLED HOWLERS (ALOUATTA-PALLIATA) IN COSTA-RICA, International journal of primatology, 19(3), 1998, pp. 451-472
Proximate and ultimate explanations of interactions between infants an
d nonmothers vary depending upon the relatedness of the interactors. W
e investigated interactions of infants and nonmothers from a 22-month
continuous study and from the long-term monitoring of the mantled howl
er population of La Pacifica, Guanacaste Province, Costa Rica. Related
ness is low or absent in these mantled howler groups. Juvenile females
appeared to practice care skills with older infants, but as most firs
t infants died, they failed to benefit. Infant positive interactions w
ith adults occurred with the mother and probable father Other adult fe
males behaved aggressively toward the youngest infants. Mothers were r
etentive of infants and responded negatively to these interactions, su
ggesting that they perceived them as threatening. Interactions with in
fants appear to reflect competition in groups of unrelated adults. A r
eview of other populations of Alouatta palliata and other species of h
owlers indicate variability in social group size and suggest variabili
ty in intragroup relatedness. We suggest that further study will confi
rm that social behavior (including interactions with infants) will var
y by resource availability (group size) and associated demographic pat
terns (male and female migration) that affect relatedness in howler so
cial groups.