The Targeted Monkey: a Re-Evaluation of Predation on New World Primates
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JASs Reports Journal of Anthropological Sciences Vol. 83 (2005), pp. 89-109 The targeted monkey: a re-evaluation of predation on New World primates Bernardo Urbani Department of Anthropology, University of Illinois at Urbana-Champaign, 109 Davenport Hall, 607 S Mathews Ave., Urbana, Illinois 61801, USA, e-mail: [email protected] Summary – This work reviews the information related to predation on Neotropical primates by human and non-human predators. Paradoxically, humans have been systematically neglected while evaluating the potential effects of predation in the structure of non-human primate populations. Predation paradigms do not include humans in their propositions. In this review, it is shown that effectively humans are the main predators of monkey communities in the Neotropics. The results also suggest that humans do not fit with predation theoretical views given for non-human predators. Homo cultural hunting practices contribute to this situation. For example, humans seem to prefer larger primate groups that allow their location for hunting, or humans tend to prey primary larger monkeys with longer interbirth interval. In sum, it is suggested that since at least 11,000 years of human occupation in the Neotropics, Homo might have been played a fundamental role in the current organization and distribution of primate populations, including local extinctions. Humans seemed to have potentially influenced New World primate population in such short ecological time scale. Keywords – Predatory behavior, ethnoprimatology, human hunting, predation paradigms, transdisciplinary perspective, conservation, Latin America. Introduction works of the natural history of primates (e. g. Kinzey, 1997); however, reports of predation are “The indications are that man is the most extreme scarce. In part, this relates to difficulties serious enemy of howlers and that occasionally obtaining field data on predation because of its young animals may be attacked by ocelots” said low rate and rapid occurrence. In addition, Isbell Clarence Ray Carpenter in 1934 after observing (1994) suggested that limited predation mantled howler monkeys in Panama (Carpenter, observation might be related to the observers (field 1934: 129). In fact, it was his last conclusion in primatologists) that are normally not present the first systematic primate behavioral research when main predators are active (at night) and the conducted in the wild, and probably also the first presence of the observer may inhibit the scientific account of the impact of predators on appearance of predators during the day. feral primates. After this work, other researches However, predation and predation risk have have taken predation risk into account as a been considered important in modeling the potential factor influencing the evolution of structure and organization of the extant and sociality in general, and the social structure of extinct primate populations (see review: Isbell, primate populations (e.g. Cheney & Wragham, 1994). In this sense, it has been argued that some 1987). For example, since the 1960s chimpanzees “anti-predatory” behaviors such as vigilance, had been the subjects of the longest-term studies polyspecific associations, group cohesion, direct or even carried out for any wild mammal; but active defense and alarm calls are related to the paradoxically it was not until 1990, that the first selective pressure of predation on primates case of predation on chimpanzees by lions was (Cheney & Wragham, 1987; Isbell, 1994). Van reported (Tsukahara & Nishida 1990). In Schaik & Horstermann (1994) proposed a addition, predation has been systematically cited in hypothesis that suggested that the quantity of the JASs is published by the Istituto Italiano di Antropologia www.isita-org.com 90 Predation on Neotropical Monkeys primate males -and group composition- is not Recently, Miller (2002) added to the discussion only related to sexual competition but also to the concept of predation vulnerability in predation risk. Their hypothesis predicts that understanding primate social organization. She males are more vigilant than females, and play a defined vulnerability as the “qualitative measure of greater role in predator detection. the probability that an individual will be the victim In her literature review, Isbell (1994: 65-68) of a predator at any given moment” (Miller, 2002: characterized five patterns of predation on 2). She indicated that this fact may play a major role primates. These patterns are, 1) larger primates are in the foraging strategies and decision-making expected to be less vulnerable to predation than among primates. Miller (2002) suggested that are smaller primates; 2) an individual’s predation vulnerability might be evaluated using vulnerability to predation increased in unknown three different variables. A biological variable, in or unfamiliar areas (for a definition of which different characteristics that are “under vulnerability, see below: Miller, 2002); 3) primates genetic control” and expressed in the primate are more vulnerable in the upper canopy, in phenotype might be significant for a given anti- discontinuous forests and on the forest edges than predatory response (e. g. body size); a social variable in continuous, undisturbed forests; 4) predation is such as differences in rank, group size and group episodic and may be related to prey preferences composition; and an environmental variable such and different use of daily ranges and home ranges as the degree of predation vulnerability associated between predators and prey; and 5) terrestrial with foraging location and the quality of the cover primates have higher rates and risk of predation or refuge available to primates. than do arboreal primates. In addition, Chapman (2000) reviewed the predation avoidance Humans as primate predators hypothesis by examining patterns of group Isbell (1994) and Cheney & Wrangham structure and movement in 54 primate species. He (1987) briefly suggested that humans are the argued that living in groups, “[may] increased major predators on primates. Similarly, Boinski et probability of predator detection, … [create] al. (2000: 47) stated in their review, “primate greater confusion of a predator trying to focus on predators are restricted to nonhuman predators an individual prey, … [propitiate] a decreased because humans probably hunt most primates” probability of each individual being captured by (italics are mine). Thus, although the impact of predators, … and increased defense against humans as predators on primates has been noted, predators” (Chapman 2000: 27). few researchers have focused on the role of human However, Janson (1998) indicated that the predators may have played in non-human primate evaluation of predation should be done with social organization (see: Sponsel, 1997). Predation caution due to the fact that presumed anti- by humans has been under-emphasized in the predatory behaviors (e. g. alarm calls, vigilance, theoretical discussions about predation on non- living in larger groups) might be linked with other human primates. However, to hunt defined by the behaviors. For instance, he indicated that for some Oxford English Dictionary (Simpson & Weiner, primate species it might be beneficial to live in 1989: 496) is “the act of chasing wild animals for small groups that are difficult for predators to the purpose of catching or killing them”; not less detect. In addition, Hill & Dunbar (1998) than another form of predation. Consequently, as suggested that predation risk is a more indicated by Mittermeier (1987) and Chapman & comprehensive parameter for evaluating predation Peres (2001), New World primates are highly on primates than predation rate. They argued that threaten due to intense hunting or human potentially the role of predation as selective predation. Nevertheless, humans had often been pressure might be more important for primates neglected in the literature on predation in when the risk of predation is perceived. In primates (Sponsel 1997). In this paper I will addition, they indicated that predator-prey examine primate prey-human predator relationship should be evaluated as the potentiality relationship in the Neotropics. So, I address the that a given primate species might be recovered following questions, from predatory events by adjusting its behavior. a) Is there evidence that predators affect the B. Urbani 91 structure of primate communities in Neotropical human vertebrates that prey on Neotropical forests? primates. b) How human predators differ from non- b) Homo predator: refers only to Amerindian human predators in prey choice, hunting hunters of monkeys in the tropical forests. In this techniques and potential affect on primate social work only Amerindians groups were included, organization? considering the assumption that are the human b) Are humans primary agents that influence populations that preyed on monkeys inheriting ecological changes such as local extinctions of long-term traditional hunting techniques and primate populations? knowledge in the Neotropics (for Campesinos - Latin American creoles-, see discussion). Methods c) Prey: the targeted New World monkey genus obtained by non-Homo or Homo predators. Information of predation on Neotropical Associated with this entry, in the cells of the primates was compiled (see Appendix). Only Appendix, information on the numbers of observed predation cases on monkeys by direct observed predation cases, age/sex of the prey, and sightings or from inspection of alimentary samples