 |
|
Key 'impact hunters' catalyze hunting among male chimpanzees
February 04, 2008While hunting among chimpanzees is a group effort, key males, known as "impact hunters" are highly influential within the group. They are more likely to initiate a hunt, and hunts rarely occur in their absence, according to a new study. The findings, which appear in the current issue of Animal Behaviour, shed light on how and why some animals cooperate to hunt for food, and how individual variation among chimpanzees contributes to collective predation.
The study was led by Ian Gilby, a postdoctoral researcher in the Department of Anthropology in Harvard's Faculty of Arts and Sciences, with Lynn Eberly of the University of Minnesota and Richard Wrangham, Ruth Moore Professor of Biological Anthropology at Harvard.
Chimpanzees live in communities of 40 to 150, within which fluid subgroups of changing size and composition form. While their diet is largely ripe fruit, chimpanzees also prey upon red colobus monkeys, which are agile and live in the trees. For this study, the researchers followed the hunting patterns of 11 adult males over more than a decade, among which two chimpanzees were identified as impact hunters. The chimpanzees that were studied live in Kanyawara, in Kibale National Park, Uganda.
"Our findings show that while hunting among chimpanzees is a group process, these individual males have a strong effect on whether or not others decide to hunt," says Gilby. "They have a strong catalytic effect on the decision to hunt. When a party of chimpanzees encounters a troop of red colobus, the impact hunters tend to be the first to hunt. By doing so, they dilute the prey's defenses, thereby reducing the costs of hunting for other chimpanzees. Hunts rarely occurred in the absence of the impact males."
If all chimpanzees were equally skilled at hunting, the addition of any given chimpanzee to a party would increase the likelihood of hunting. However, this did not appear to be the case; it was the addition of these two impact hunters that increased hunting likelihood. It is not entirely clear what special qualities these chimpanzees might posses that would contribute to their role in hunting groups. Of the two impact hunters one was the alpha male, but one was not particularly high-ranking or outstanding in terms of physical appearance. What appears to be significant is that these particular chimpanzees display a unique willingness to hunt, and have a high success rate when hunting. The findings of this study may also be applicable to the hunting behavior of other animals that hunt in this way, such as dolphins and lions.
This study also addresses the motivation for hunting in groups. It has previously been suggested that hunting with others increases the amount of meat that each individual obtains. However, chimpanzees obtain most of their calories from ripe fruit, and hunting does not increase in response to a scarcity of fruit. Instead, the researchers theorize that meat provides important micronutrients that are difficult to obtain solely from fruit, and because of this, even a small scrap of meat is beneficial.
Gilby and his colleagues have shown that as the number of hunters increases, so does the likelihood that an individual will receive a piece of meat. Therefore, there is an incentive for a given male to join a hunt. However, in large groups, hunters and non-hunters were equally likely to obtain meat, suggesting that an individual should refrain from hunting thus avoiding the inherent risks and dangers of chasing prey. This is exactly what the researchers found - the likelihood that a given male hunted increased rapidly with party size, but only to a point. In large groups, there was no effect of party size on an individual's hunting probability.
While predation among chimpanzees is cooperative, the researchers found that hunting does not appear to be a collaborative process. Males were not more likely to hunt for reasons of social bonding, nor was there an association between the presence of a sexually receptive female and an increased likelihood of hunting.
Harvard University
"Our findings show that while hunting among chimpanzees is a group process, these individual males have a strong effect on whether or not others decide to hunt," says Gilby. "They have a strong catalytic effect on the decision to hunt. When a party of chimpanzees encounters a troop of red colobus, the impact hunters tend to be the first to hunt. By doing so, they dilute the prey's defenses, thereby reducing the costs of hunting for other chimpanzees. Hunts rarely occurred in the absence of the impact males."
If all chimpanzees were equally skilled at hunting, the addition of any given chimpanzee to a party would increase the likelihood of hunting. However, this did not appear to be the case; it was the addition of these two impact hunters that increased hunting likelihood. It is not entirely clear what special qualities these chimpanzees might posses that would contribute to their role in hunting groups. Of the two impact hunters one was the alpha male, but one was not particularly high-ranking or outstanding in terms of physical appearance. What appears to be significant is that these particular chimpanzees display a unique willingness to hunt, and have a high success rate when hunting. The findings of this study may also be applicable to the hunting behavior of other animals that hunt in this way, such as dolphins and lions.
This study also addresses the motivation for hunting in groups. It has previously been suggested that hunting with others increases the amount of meat that each individual obtains. However, chimpanzees obtain most of their calories from ripe fruit, and hunting does not increase in response to a scarcity of fruit. Instead, the researchers theorize that meat provides important micronutrients that are difficult to obtain solely from fruit, and because of this, even a small scrap of meat is beneficial.
Gilby and his colleagues have shown that as the number of hunters increases, so does the likelihood that an individual will receive a piece of meat. Therefore, there is an incentive for a given male to join a hunt. However, in large groups, hunters and non-hunters were equally likely to obtain meat, suggesting that an individual should refrain from hunting thus avoiding the inherent risks and dangers of chasing prey. This is exactly what the researchers found - the likelihood that a given male hunted increased rapidly with party size, but only to a point. In large groups, there was no effect of party size on an individual's hunting probability.
While predation among chimpanzees is cooperative, the researchers found that hunting does not appear to be a collaborative process. Males were not more likely to hunt for reasons of social bonding, nor was there an association between the presence of a sexually receptive female and an increased likelihood of hunting.
Harvard University
Chimpanzees Current Events and Chimpanzees News RSSA year after discovery, Congo's 'mother lode' of gorillas remains vulnerable
A new study by the Wildlife Conservation Society says that western lowland gorillas living in a large swamp in the Republic of Congo-part of the "mother lode" of more than 125,000 gorillas discovered last year-are becoming increasingly threatened by growing humans activity in the region.
Scientists unlock clues for tailoring corn plant for food, energy needs
Scientists have long known that the offspring of two inbred strains tend to be superior to both their parents. Now, a team of researchers including a University of Florida geneticist has discovered clues to why that might be the case for one of the most important crops in the world: corn.
Unknowlingly consuming endangered tuna
While most of us would never willingly consume a highly endangered species, doing so might be as easy as plucking sushi from a bento box.
Babies with an accent
In the first days of their lives, French infants already cry in a different way to German babies.
Hormone that affects finger length key to social behavior
The hormones, called androgens, are important in the development of masculine characteristics such as aggression and strength.
Chimpanzees help each other on request but not voluntarily
The evolution of altruism has long puzzled researchers and has mainly been explained previously from ultimate perspectives-I will help you now because I expect there to be some long-term benefit to me.
Blood counts are clues to human disease
A new genome-wide association study published today in Nature Genetics begins to uncover the basis of genetic variations in eight blood measurements and the impact those variants can have on common human diseases.
Kent State University Professor C. Owen Lovejoy helps unveil oldest hominid skeleton
Throw out all those posters and books that depict an ape evolving into a human being, says Kent State University Professor of Anthropology Dr. C. Owen Lovejoy.
Ardi displaces Lucy as oldest hominid skeleton
Nearly 17 years after plucking the fossilized tooth of a new human ancestor from a pebbly desert in Ethiopia, an international team of scientists today announced their reconstruction of a partial skeleton of the hominid, Ardipithecus ramidus, which they say revolutionizes our understanding of the earliest phase of human evolution.
Hyenas cooperate, problem-solve better than primates
Spotted hyenas may not be smarter than chimpanzees, but a new study shows that they outperform the primates on cooperative problem-solving tests.
More Chimpanzees Current Events and Chimpanzees News Articles
 |
My Life with the Chimpanzees by Jane Goodall (Author) From the time she was a girl, Jane Goodall dreamed of a life spent working with animals. Finally she had her wish. When she was twenty-six years old, she ventured into the forests of Africa to observe chimpanzees in the wild. On her expeditions she braved the dangers with leopards and lions in the African bush. And she got to know an amazing group of wild chimpanzees -- intelligent animals whose lives, in work and play and family relationships, bear a surprising resemblance to our own. |
 |
Next of Kin: My Conversations with Chimpanzees by Roger Fouts (Author), Stephen Tukel Mills (Author) For 30 years Roger Fouts has pioneered communication with chimpanzees through sign language--beginning with a mischievous baby chimp named Washoe. This remarkable book describes Fout's odyssey from novice researcher to celebrity scientist to impassioned crusader for the rights of animals. Living and conversing with these sensitive creatures has given him a profound appreciation of what they can teach us about ourselves. It has also made Fouts an outspoken opponent of biomedical experimentation on chimpanzees. A voyage of scientific discovery and interspecies communication, this is a stirring tale of friendship, courage, and compassion that will change forever the way we view our biological--and spritual--next of kin. |
 |
Nature: Chimpanzees - An Unnatural History Starring: Allison Argo Nature, the eight-time Emmy-winning PBS series, kicked off its 25th season with this powerful episode. In 1959, the United States Air Force captured dozens of baby chimpanzees in Africa, transporting them to Alamogordo, New Mexico, where they and their offspring were to endure a grueling life as the ultimate human stand-ins. From experiments in space travel and high-velocity crash tests, to pharmaceutical testing and hepatitis and AIDS research, to roles on the silver and small screens, these original Air Force chimpanzees and others that followed gave their lives to benefit humankind. Now, a few extraordinary people are working to give those lives back. Emmy Award-winning producer and director Allison Argo (Extraordinary Dogs) narrates this compelling and powerful program that witnesses... |
 |
Webkinz Plush Stuffed Animal Chimpanzee by Webkinz Webkinz Chimpanzee |
 |
Captivity by Debbie Lee Wesselmann (Author) When someone releases the chimpanzees at the South Carolina Primate Project, its director, Dana Armstrong, is forced to confront the complexity of both her past and the present as she struggles to preserve the chimps' sanctuary. |
 |
BEWARE OF THE CHIMPANZEE Adult USA Flag Hat / Cap by T-ShirtFrenzy T-ShirtFrenzy offers over 30,000 designs on tons of products to offer millions of variations. You can search our store for something for everyone on your gift list or shop for yourself (our personal favorite). Please contact us with questions. |
 |
The Chimpanzee Family Book (Animal Family Series) by Jane Goodall (Author), Michael Neugebauer (Photographer) British naturalist Jane Goodall provides an intimate portrait of a group of chimpanzees in the jungles of Africa which she has studied for many years. |
 |
Webkinz Signature Deluxe Plush Figure Chimpanzee by Ganz Signature Chimpanzee has a special internet code for your child to interact with it. They can name it, make it a home & play games. Not recommended for children under 3. *NOTE: Webkinz orders are limited to 12pcs per style per customer. Includes wish token & pet specific item. Polyester. |
 |
Nature: Chimpanzees Starring: F. Murray Abraham, Paul Christie, Howard McGillin, Peter Coyote, Jay O. Sanders Directed By: Nigel Cole Also With: Suzanne Weinert (Producer), Mark Hobson (Writer) Learn more about these creatures from the wild, who really aren't that different from us! Program 1: Jane Goodall’s Wild Chimpanzees - Jane Goodall provides privileged access to an absorbing family saga in the wilds of Tanzania. Observe the family’s complex day-to-day life through intimate communications and relationships. Program 2: Monkey in the Mirror - Chimps and primates use tools, language, politics and even culture. How does their intelligence compare to our own? This program investigates the answers in both the laboratory and the wild. |
 |
National Geographic by New Creative - Chimpanzee Garden Impressions Flag by New Creative Explore your wild side with this exclusive collection of flags , featuring breathtaking images from world-renowned National Geographic photographers. |
| © 2009 BrightSurf.com |