The Socioecology of Adult Female Patas Monkeys and Vervets in Kenya

Jill D.E. Pruetz

• Publisher: Routledge
• Year: 2015
• Print ISBN: 9780131927872
• eBook ISBN: 9781317344087
• Topic: Scienze sociali
• Subtopic: Antropologia

For upper-level and/or graduate level Primatology or Biological Anthropology courses.Socioecology of Adult Female Patas Monkeys and Vervet in Kenya, East Africa provides students with a glimpse into a research project from start to finish. It discusses basic issues of studying primates and explores one of the major theories that has defined primatology for several decades. This text not only contributes detail on primate behavior, but also on the ecological variables that influence primate behavior. These are often difficult to measure, but the unique environment at the study site enabled the author to address questions that are much more difficult to answer elsewhere.

CHAPTER
1

The Research Question

General ecological theory maintains that whereas male mammals are reproductively limited mainly by the number of mates available to them, a female’s reproductive success is limited by the availability of foods to her (Trivers 1972; Wrangham 1980). Therefore, patterns of food distribution and abundance are likely to exert a strong influence on a female mammal’s behavior. I undertook this study of vervet and patas monkeys in Kenya to test hypotheses derived from models based on these assumptions, which attempt to explain social behavior among adult female primates (Isbell 1991; van Schaik 1989; Sterck, Watts, & van Schaik 1997; Wrangham 1980). These models make predictions about the types of dominance hierarchies adult female primates will exhibit based on the distribution and abundance of foods available to them. The models assume that food availability influences competition among females and that such competition results in particular dominance styles. Feeding competition includes supplants at feeding sites or aggression during feeding (Isbell & Young 2002). Female primates are expected to compete aggressively when foods are both limited and usurpable (e.g., occurring in small patches) and despotic dominance hierarchies are predicted to emerge (Isbell 1991; van Schaik 1989; Wrangham 1980). To test the hypotheses derived from these models, I investigated the feeding behavior, social behavior, and food resources available to free-ranging vervet and patas monkeys from June 1993 to August 1995 at Segera Ranch, Laikipia, Kenya. The nature of the study site provided an excellent opportunity to examine contest competition and dominance relationships among adult females in two closely related species that use the same food resources.

STUDY SPECIES—VERVETS AND PATAS MONKEYS

Vervets and patas monkeys are members of the tribe Cercopithecini (subfamily Cercopithecinae, family Cercopithecidae), which consists of the African guenons. Guenons are a fairly recent radiation of Old World monkeys, probably evolving within the last one million years (Leakey 1988). Mating systems of forest guenons of the genus Cercopithecus [this excludes vervet and patas monkeys, talapoins (Miopithecus), and Allen’s swamp monkey (Allenopithecus)] range from female defense polygyny (i.e., one male monopolizes reproductive access to females) to promiscuity with multimale influxes (Cords 1988). Most guenons exhibit male intolerance of other adult males (with vervets being an exception), female defense of home ranges, and a lack of male interaction with nonreceptive females (Rowell 1988). Patas monkeys exhibit most of the aforementioned traits, whereas vervets are characterized only by female defense of home ranges.

Adult male vervet. (Photo by the author)

Vervet and patas monkeys are closely related primate species (Disotell 2000; Gautier 1988; van der Kuyl et al. 1995; Martin & MacLarnon 1988; Ruvolo 1988) that have been reported to hybridize in captivity (see Lernould 1988; Matsubayashi et al. 1978). They are considered more closely related to one other than to other guenons based on chromosomal banding pattern evidence (Disotell 1996), morphological traits (Strasser & Delson 1987), and protein electrophoretic data (Ruvolo 1988). Anatomically and morphologically, vervet and patas monkeys exhibit many similarities. Each has been classified as semiterrestrial (Kingdon 1988) and as showing hand and foot adaptations geared toward terrestrial locomotion (Kingdon 1988; Strasser 1992). Patas monkeys have traditionally been classified separately from other guenon species based on such morphological characters as their long limb length.

Both patas and vervets are characterized as having overlapping home ranges with conspecific groups, aggressive intergroup interactions involving adult females, distinct mating and birthing seasons, female-resident social groups, and seasonally restricted food sources (Table 1–1). Differences between the two species include size of day and home ranges, size of within-group spread, body size, and number of adult males resident in social groups. Notable to this study, vervet and patas monkeys are characterized by marked differences in female-dominance relationships. Vervets exhibit a linear and stable dominance hierarchy (Cheney & Seyfarth 1990; Isbell & Pruetz 1998; Whitten 1983; Wrangham 1981), whereas dominance among female patas monkeys is more egalitarian and individualistic (Isbell & Pruetz 1998; but see Nakagawa 1992). While patas monkeys are characteristically described as savanna-dwelling or savanna-woodland–dwelling primates (Chism & Rowell 1988; Hall 1965; Isbell et al. 1998; Struhsaker & Gartlan 1970), vervets are described as inhabiting riverine or gallery forest woodlands (Chism & Rowell 1988; Gartlan & Brain 1968; Pickford & Senut 1988; Struhsaker 1967b).

Adult male patas monkey (foreground). (Photo by the author)

Table 1–1 Vervet and Patas Monkey Social Structure, Behavior, and Morphology

	Patas Monkeys	Vervets
Social structure
Similarities	Male dispersal	Male dispersal
	Overlapping home ranges	Overlapping home ranges
	Group size means: 19 (N = 9), 26 (N = 3), 17.8 (N = 5), 36 (N = 10)	Group size mean: 25
Differences	Unstable female dominance hierarchy	Stable female dominance hierarchy
	Non-linear female dominance hierarchy	Linear female dominance hierarchy
	One-male social group	Multimale group
	Home ranges not defended	Defended home ranges
Behavior
Similarities	Distinct mating season	Distinct mating season
	Distinct birth season	Distinct birth season
	Omnivorous diet	Omnivorous diet
	Acacia important in diet	Acacia important in diet
	Seasonal food resources	Seasonal food resources
	Semi-terrestrial	Semi-terrestrial
Differences	Large day range, 4,220 m, 3,830 m	Small day range, mean 1,555 m
	Large home range, mean 2,770 ha, N = 2	Small home range, 178 ha
	Various sleeping sites	Regularly used sleeping sites
	Patchy woodland	Continuous woodland
Morphology
Differences	Larger body size (12 kg adult male, 7 kg adult female)	Smaller body size (5.6 kg adult female, 7 kg adult male)
	Longer limb length	Shorter limb length (relative to body size)
	Females mature earlier (2.5 years)	Females mature later (3.5 years)
	Males ~45% larger	Males ~20% larger

Sources: Afr J Ecol (1994); Chism and Rowell (1986, 1988); Chism, Rowell, and Olson (1984); Fedigan and Fedigan (1988) review; Gartlan and Brain (1968); Hall (1965); Hall and Gartlan (1965); Harrison (1983, 1984, 1985); Henzi and Lucas (1980); Kaplan and Zucker (1980); Kavanagh (1978); Lee (1984); Loy and Harnois (1988); Loy et al. (1993); Nakagawa (1992, 2000); Struhsaker (1967a,b, 1969); Struhsaker and Gartlan (1970); Tur...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• List of Figures
• List of Tables
• Preface
• Acknowledgments
• 1 The Research Question
• 2 Measuring Primate Behavior and Ecology
• 3 Foods Available to Vervet and Patas Monkeys
• 4 Feeding Behavior of Patas and Vervet Monkeys
• 5 Food Availability’s Influence on Competition and Dominance in Vervets
• 6 Comparing Vervet and Patas Monkeys in Whistling-Thorn Woodland
• 7 Testing Predictions of Models of Female Primate Behavior and Ecology
• References
• Index