Assignment 4

Body Size and Sexual Dimorphism

LEMURS

1.         Lemurs reside on the Madagascar and Comoro islands off the coast of Africa. Some live in trees in the thick rainforest jungles, which is why they are called arboreal.  Others live in desert areas that are hot and dry making them adaptable to their environment.  Most lemurs can by found in the forest simply because more food can be found there.  Lemurs are primarily nocturnal and rarely nest in one place for too long to avoid predators.

            Lemurs vary in size from different species, but within their own species, the male and female are relatively the same. However, lemurs do show a sexual dimorphism between the colors of their fur.  Typically, males have a plain color fur, such as black, while females have more bright color furs, like brownish shades and contrasting colors. Sexual dimorphism plays a little role in avoiding predators because the main threat to lemurs is deforestation and a change of fur color won’t help with their survival in that sense of matter. For mating purposes, the female’s brighter colored fur attracts males and betters their odds for reproduction.

            While body size does little in sexual dimorphism, it does play a role in their survival. Most lemurs are small and lightweight, which allows them to stay high up in the canopies and away from predators. Jumping from tree to tree is the main source of traveling so being small and agile is essential to arboreal lemurs.

SPIDER MONKEYS

2.         Spider monkeys live in the tropical rainforests of Central and South America. Like lemurs, spider monkeys travel from tree to tree with lanky arms and are considered arboreal too. When they are born, they tend to stay close to the mother and depend on her for survival. Since humans usually hunt these monkeys for food, they tend to stay clear of us and are easily scared off. One main difference between spider monkeys and other primates is that they do not possess a thumb but a stronger tail.

            There’s little difference between male and female spider monkeys. Sexual dimorphism is almost non-existent. The female does however make a high-pitched screech that wards off predators and can be used to determine male from female.

            Like lemurs, spider monkeys are also small and lightweight. This enables them to live in the trees. Their strong, muscular tail acts as a third arm and supports their weight when hanging from limbs since they do not have thumbs.

BABOONS

3.         Baboons are very adaptable to different environments. They are typically ground-dwelling primates during the day and seek shelter in tall trees or cliffs during the night. They tend to stay near water on savannah-like plains. Baboons are social primates and are usually found in groups of thirty or more. While females stay with their troop for most of their lives, males are know to travel in and out of other troops as well.

            Unlike lemurs and spider monkeys, baboons do show a lot of sexual dimorphism. The first would be the weight and body size. Males can grow up to twice the size of females. Secondly, the different colors of fur. Females have more of a brownish coat while males are more grayish. Thirdly, the female flashes her behind to males. The females bottom swells and becomes bright pink to attract males. Lastly, tooth size is a factor. The canines of a male baboon can grow up to four times longer than that of

females.

            These sexual dimorphisms help with the survival of baboons, especially the males. Like I stated before, males can travel from one troop to the next. Displaying these long canine teeth to other males is a way of being accepted into the troop and mating with multiple females. The canine and body size of males is also to protect them from predators. Since baboons are mainly ground-dwelling primates, they may come in contact with leopards, cheetahs, and even humans. By having a group of large males with long canines, they can fend off or scare predators away

GIBBONS

4.         Gibbons are common in areas of India, Indonesia, and China (Southeast Asia). They are a bit different from the rest of these primates. Although they do live in tropical rainforests, they do not make nests like the others. Gibbons are arboreal and can move very fast while swinging. The only main threat to gibbons is increasing deforestation.

            Like lemurs and spider monkeys, gibbons show practically no sexual dimorphism. The males are a bit larger than the females. Male and females are mates for life, so there is no need for a ‘show of attraction’ if you will. The males and females do have different calls. These calls are to warn other gibbons in their group of predators and to keep away gibbons outside of their group from coming into their territory. The female usually starts these calls and can be an indicator to determine male from female.

            The gibbons are small, lightweight, and agile which allows them to maneuver from branch to branch avoid predators on the ground (including humans).

CHIMPANZEES

5.         Chimpanzees, our closest living relatives, live in social communities within African rainforests, woodlands, and grasslands. While they can walk on all fours, they swing from tree to tree, collecting and eating food. Chimps also do their nesting in trees. They, like us, are omnivores and eat meat, fruits, and insects. They are also known to use tools to get to food and water.

            Since chimpanzees and humans are closely related, it’s only right that we would have some same sexual dimorphisms. Males are both heavier and taller than the females. Male and female are very similar in appearance. A female chimp and her child have a special bond and can often be seen together, making it relatively easy to find a female.

            While the females care for the infant chimpanzees, the males are left to defend their group. The bigger stature males possess is an advantage to fend off predators. Like baboons, a group of large, male chimpanzees can be threatening to a predator. Also, the stature of a male can be used in finding a mate and reproducing with females.

SUMMARY

Overall, New World Monkeys show less sexual dimorphism and body size between their species. While spider monkeys and chimpanzees show little difference, baboons show noticeable difference between male and female. Also, Old World Monkeys are typically not tree-dwelling primates. A male gorilla or baboon would have trouble swinging from branches because they can grow to be very heavy. So while lemurs, spider monkeys, and gibbons can brisk through canopies to evade their predators, baboons display a bigger stature and huge teeth to fend off enemies.