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Individual differences |
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| Javan lutung (Trachypithecus auratus)|
Javan lutung (Trachypithecus auratus)
The Colobinae are a subfamily of the Old World monkey family that includes 59 species in 10 genera, including the skunk-like black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications split the colobine monkeys into two tribes, while others split them into three groups. Both classifications put the three African genera Colobus, Piliocolobus, and Procolobus in one group; these genera are distinct in that they have stub thumbs (Greek κολοβός kolobós = "docked"). The various Asian genera are placed into another one or two groups. Analysis of mtDNA confirms the Asian species form two distinct groups, one of langurs and the other of the "odd-nosed" species, but suggests the gray langurs are not closely related to either.
Colobines are medium-sized primates with long tails and diverse colorations. The coloring of nearly all the young animals differs remarkably from that of the adults.
Most species are arboreal, although some live a more terrestrial life. They are found in many different habitats of different climate zones (rain forests, mangroves, mountain forests, and savanah), but not in deserts and other dry areas. They live in groups, but in different group forms.
They are almost exclusively herbivores, predominantly nourishing themselves on leaves, flowers, and fruits. They occasionally eat insects and other small animals. To aid in digestion, particularly of hard-to-digest leaves, they have multichambered, complex stomachs. Unlike the other subfamily of Old World monkeys, the Cercopithecinae, they possess no cheek pouches.
Gestation averages six to seven months. Young are weaned at about one year and are mature at three to six years. Their life expectancy is approximately 20 years.
- FAMILY CERCOPITHECIDAE
- Subfamily Cercopithecinae
- Subfamily Colobinae
- African group
- Langur (leaf monkey) group
- Odd-nosed group
Sarah Hrdy's PhD thesis tested the hypothesis that overcrowding causes infanticide in langur colonies. She went to Mount Abu in India to study Hanuman Langurs, and concluded that infanticide was independent of overcrowding - it was possibly an evolutionary tactic: When an outside male takes over a group, he usually proceeds to kill all infants. This postulated tactic would be very advantageous to the male langurs who practiced infanticide. Turnover in a langur tribe occurs approximately every 27 months. The male who is taking over has a very small window of opportunity to pass on his genes, and if the females are already nursing infants, it's likely that they won't ovulate again for another year. Killing their dependent infants makes the females once again receptive to mating.
Female choice is subverted, as females are put under pressure to ovulate and are forced to breed with the infanticidal males. This is where the idea of sexual counter-strategies comes into play. Hrdy theorized that by mating with as many males as possible, particularly outside males who are not part of the colony, mothers are able to successfully protect their young, as males were unlikely to kill an infant if there was the slightest chance that it might be their own.
That gives an "illusion of paternity," as Trivers put it. The goal of the male langur is to maximize the proportion of his offspring, and according to Hrdy, a male who attacks his own offspring is rapidly selected against. While infanticide has been seemingly preserved across primate orders, Hrdy found no evidence to suggest that the human species has a 'genetic imperative' for infanticide.
In 1975 Hrdy was awarded her PhD for her research on langurs. In 1977 it was published in her second book, The Langurs of Abu: Female and Male Strategies of Reproduction. The controversy in the anthropology realm that her research sparked was not surprising - the classic belief that primates act for the good of the group was discarded, and the field of sociobiology gained increasing support. Many mistakenly assumed that she implied existence of an 'infanticidal gene' that could be conserved across primates. Today, her results and conclusions are widely received. Even Trivers, who once dismissed her apparently illogical convictions, admits that her theory regarding female sexual strategies has "worn well."
- ↑ 1.0 1.1 Template:MSW3 Primates
- ↑ 2.0 2.1 Sterner, Kirstin N.; Raaum, Ryan L.; Zhang, Ya-Ping; Stewart, Caro-Beth & Disotell, Todd R. (2006). Mitochondrial data support an odd-nosed colobine clade. Molecular Phylogenetics and Evolution 40 (1): 1–7.
- ↑ Rowe, N. (1996). The Pictorial Guide to the Living Primates, 139, 143, 154, 185, 223, Pogonias Press.
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