90 CHAPTER 4 | Primate Behavior
of trails or where downed trees obscure the path, will de-
liberately stomp down the vegetation so as to indicate their
direction or rip off large leaves and place them carefully
for the same purpose. Thus they all know where to come
together at the end of the day.^16
Primatologists have also found that primates can com-
municate specific threats through their calls. Researchers
have documented that vervet monkey alarm calls com-
municate on several levels of meaning to elicit specific re-
sponses from others in the group.^17 The calls designated
types of predators (birds of prey, big cats, snakes) and
where the threat might arise. Further, they have docu-
mented how young vervets go about learning the appro-
priate use of the calls. If the young individual has uttered
the correct call, it will be repeated by adults, and the ap-
propriate escape behavior will follow (heading into the
trees to get away from a cat or into brush to be safe from
an eagle). But if an infant utters the cry for an eagle in
response to a leaf falling from the sky or in response to a
nonthreatening bird, no adult calls will follow.
From an evolutionary perspective, scientists have
been puzzled about behaviors such as these vervet alarm
calls. Biologists assume that the forces of natural selection
work on behavioral traits just as they do on genetic traits.
It seems reasonable that individuals in a group of vervetpleasure with sociable body contact. Calls called “pant-
hoots,” which are used to announce the arrival of indi-
viduals or to inquire, can be differentiated into specific
types. Together, these facilitate group protection, coordi-
nation of group efforts, and social interaction in general.
To what degree are various forms of communication
universal and to what degree are they specific to a given
group? On the group- specificity side, primatologists have
recently documented within-species dialects of calls that
appear as groups are isolated in their habitats. Social fac-
tors, genetic drift, and habitat acoustics could all contrib-
ute to the appearance of these distinct dialects.^14
Smiles and embraces have long been understood to be
universal among humans and our closest relatives. But re-
cently some additional universals have been documented.
Blind athletes use the same gestures to express submission
or victory that sighted athletes use at the end of a match,
though they have never seen such gestures themselves.^15
This raises interesting questions about whether primate
communications are biologically hardwired or learned.
Visual communication can also take place through ob-
jects. Bonobos do so with trail markers. When foraging,
the community breaks up into smaller groups, rejoining
again in the evening to nest together. To keep track of each
party’s whereabouts, those in the lead, at the intersections
Athletes who have been blind since birth
use the same body gestures to express
victory and defeat as sighted athletes.
Because they do this without ever hav-
ing seen an “end zone” celebration, this
indicates that these body gestures are
hardwired into humans and presumably
derive from our primate heritage.
(^14) de la Torre, S., & Snowden, C. T. (2009). Dialects in pygmy marmosets?
Population variation in call structure. American Journal of Primatology 71
(4), 333–342.
(^15) Tracy, J. L., & Matsumoto, D. (2008). The spontaneous expression of
pride and shame: Evidence for biologically innate nonverbal displays.
Proceedings of the National Academy of Sciences 105 (33), 11655–11660.
(^16) Recer, P. (1998, February 16). Apes shown to communicate in the wild.
Burlington Free Press, 12A.
(^17) Seyfarth, R. M., Cheney, D. L., & Marler, P. (1980). Vervet monkey alarm
calls: Semantic communication in a free-ranging primate. Animal Behavior
28 (4), 1070–1094.
© Bob Willingham