3.2.10 Female Bonded - the core of the group is made up of females. - This is how it is in primates. - Most primates eat fruit. Fruit is found in different places throughout the forest, both spatially and temporarily. - This means that you can defend a fruit tree. - Groups can be excluded from having access. - Females will especially work together to defend the trees, because they need the nutrients for reproduction. - This results in bonding. Infanticide - intentional killing of an infant. - Occurs in the Hanuman Langur monkies in India. - Langurs live in harems (adult male and several females, and their dependent offspring). - The male controls reproductive access. - Outside of these groups, there are some adult males that are not a part of the harem. - Males that have just come into adolescence are not part of the harem. They have not established themselves. - Older males are not a part of harems either. - The young males attempt to compete with males that have control of the harems. Occasionally, they are successful. - The first thing the young male will do when challenging the harem is kill the offspring. - If the offspring is nursing, the adult female is not in estrus. If the offspring is killed, she is no longer in estrus and can be susceptible to mating. For this reason, the offspring that are still nursing are the ones that are killed. - A male is usually in charge of a harem for three years, which is the amount of time it takes to create and wean a child for the langurs. - If a non-infanticidal male comes in the group, he must wait for the baby to be born and weaned. - An infanticidal male's children are more likely to be infanticidal. - Infanticide only benefits the individual. Pseudo-Estrus - Counter strategy to male infanticide. - The females display false signs of estrus, particularly when they are pregnant and when a new male comes into the harem. - The male mates with her because he believes she is in estrus, and is then less likely to kill the offspring. These are behaviors that have evolved through natural selection. They are not done consciously. Apes Superfamily Hominoidea (apes and humans) - Hominoid Sexual Dimorphism - Difference in size (gorillas vs. humans) 1. Family Hylobatidae (lesser apes) - These are medium sized apes (20 lbs.) - Brachiation - lesser apes swinging beneath the branches, rather than walking on top of the branches like monkies. - Gibbons are advanced in brachiation because of their fingers - they have the longest. - In apes, long arms indicate suspensory behavior - suspend their weight to hang onto branches. - They also have long arms to balance. - Not good at walking on the ground bipedally. - Gibbons live in Southeast Asia islands and tropics (Thailand, Indonesia) 2. Family Pongidae (great apes) - Orangutan - only found in Borneo and Sumatra. Females are half the size of males. - They are suspensory. - Quadrumanual - "Four Handed" - they use their arms and legs in climbing to distribute their weight. Their hands and feet look the same. - In zoos they can get up to 300 lbs., in the wild only about 100. - Gorilla - Africa - Largest Living primates; males can get up to 400 lbs., females 200. - Vegetarian. - Dian Fossey - first woman who studied gorillas. Chimps - Africa Jane Goodall - studied chimps. - They recognize each other by faces. - They make and use tools. - They are playful. - They eat meat. - They can be bipedal, though not as effectively as humans. Bonobos (pygmy chimps) - Africa Social Distinctions between Apes: Gibbons: - They are monogomous - bond as pairs for life. - Males exclude males so they won't have access to his female, and females exclude females so they won't have access to her fruit. - Territoriality - they mark territories by singing. - Male and females are the same size. Orangutans: - They are solitary - males and females only interact when the female is in estrus. - Force Copulation - rape. Usually done by young males who are not established, and come into a territory when the older male is not around. Usually is done when a female is not even in estrus. - They do not benefit from female-bonded groups because the females are large enough that they would be able to eat a whole tree themselves. Female-bonding would result in competition. Gorillas: - They live in harems, but the females in the harem are not related. There is no benefit with grouping with females since they eat vegetation. Vegetation doesn't need to be defended. They are in harems to protect offspring from other males. Chimps - They live in male-bonded communities. - Males embark on a border patrol - when they are on the edges of their community, they become very quiet. If they encounter another individual from the other community, they will attack and usually murder the animal. - In a 5 year period, Jane Goodall documented that the males killed 6 of the 7 males in a neighboring community. The benefit of this is they gain access to the females from that community. - Bonobos are more peaceful; they do not have border patrols. - Chimp mating behavior is promiscuous. When a female is in estrus, she will mate with all males in the community. This is why we do not see much sexual dimorphism - they do not have to fight for access to females. - This does result in sperm competition - has to do with testicle size. - For females, this is beneficial because the males won't kill the child if it might belong to them - this is called paternal confidence. - Bonobos and humans are the only primates that mate even when the females are not in estrus. - Termiting - chimps get a thin, flexible strip to probe a termite hill. The soldier termites attach to it to attack it and the chimp can eat them. - In West Africa, chimps use rocks to open up nuts. In East Africa, they have not learned how to do this. This is an example of culture and learned behavior. - Chimp males and chimp females prefer different things to eat. Females get most of their protein from insects, and males get most of their protein from animal meat. - Chimp males hunt - usually young baboons.
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