The reduced efficiency of juveniles does not appear to be related to feeding competition or small body size, but rather in locating food, leading to a greater amount of time spent spent foraging. Similarly, juvenile chacma baboons ( Papio ursinus) are less efficient foragers than adults on difficult-to-extract resources ( Johnson & Bock, 2004). Although individuals participate in this activity at low rates as infants, they do not become fully proficient at detecting prey until subadult-hood, which is at ~6 years ( Gunst, Boinski, & Fragaszy, 2010). To successfully perform this behavior, individuals must learn to locate prey. For example, brown capuchin monkeys ( Sapajus apella) use extractive foraging techniques to obtain larvae that are embedded in bamboo stalks. In other primate species, however, immature individuals do not become competent foragers until later in development. These data suggest that immature primates must become competent foragers around the time that they become responsible for their complete caloric intake and all nutritional requirements. Hiraiwa-Hasegawa (1990a) suggested that immature individuals must acquire adult feeding patterns by weaning in order to survive, and indeed most studies of primate feeding development have found that individuals exhibit adult-like diets and become proficient foragers by weaning or, at a minimum, long before adulthood (e.g., Cebus capucinus: MacKinnon, 2006 Eulemur fulvus: Tarnaud, 2004 Gorilla beringei: Watts, 1985 Gorilla gorilla: Nowell & Fletcher, 2008 Pongo abelii: van Adrichem et al., 2006 Schuppli et al., 2016 Pongo pygmaeus: Schuppli et al., 2016 Saimiri oerstedii: Boinski & Fragaszy, 1989 Saimiri sciureus: Stone, 2006). Although this approach has emphasized the importance of social learning for acquiring adult feeding behaviors, we still lack data in many species on when these patterns emerge. Instead, research has primarily focused on the social learning mechanisms by which immature individuals acquire adult dietary patterns and foraging behaviors (e.g., Boinski et al., 2003 Lonsdorf, 2005 reviewed in Rapaport & Brown, 2008).
Food habits of chimpanzees full#
To date, most studies of primate feeding development have not assessed the full developmental sequence of feeding behavior, making it difficult to identify the extent to which age-related changes in feeding development exist. Comparable information on the development of feeding behavior is therefore needed from nonhuman primate populations to evaluate whether the needing-to-learn hypothesis can explain delayed maturation across primates. However, compared to most primates, the human dietary niche is extremely skill-intensive (reviewed in Kaplan, Hill, Lancaster, & Hurtado, 2000). In small-scale foraging communities, for example, humans do not become expert hunters until adulthood ( Gurven, Kaplan, & Gutierrez, 2006 Walker, Hill, Kaplan, & McMillan, 2002).
The needing-to-learn hypothesis attempts to explain delayed maturity in nonhuman primates, but it is most supported by studies of human populations. Additionally, within a population, the needing-to-learn hypothesis predicts that immature individuals will exhibit reduced feeding competency compared to adults.
Across primate species, this hypothesis predicts that there will be a positive relationship between dietary complexity and the length of the juvenile period. The needing-to-learn hypothesis ( Ross & Jones, 1999) proposes that delayed maturation in primates provides individuals with time to acquire the skills and knowledge that are necessary to exploit a complex diet, ultimately raising lifetime fitness. The function of this extended developmental period is puzzling because it necessarily imposes fitness costs by delaying reproductive maturity. Primates, including humans, are characterized by extended juvenile periods compared to mammals of similar body sizes ( Kappeler & Pereira, 2003 Pereira & Fairbanks, 1993 van Schaik & Isler, 2012).
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