Comparative Primate Post

Lemur

Environment

Lemurs are found on the island nation of Madagascar off the east coast of Africa and they flourish in the rainforests located on the east coast of the island. They have adapted to varying floral and precipitation conditions throughout the island and the dry western regions but seem to prefer the rainforest environment. They live in a harsh seasonal climate in Madagascar that usually has limited resources and unpredictable extreme weather conditions. Most lemurs live in the trees but some are terrestrial.

Body Size and Sexual Dimorphism

Lemur species range in size from the 5 inch long, 1.1 ounce mouse lemur to the 2 to 3 foot 20 pound Indri lemur. There were actually also 440 pound giant lemurs that have only recently become extinct on the island. Today there are about 60 different species of lemurs and they generally do not differ in size between male and females and are monomorphic.

Environmental Trait Adaptation

Limited food resources and very specific seasonal breeding along with small group sizes have been linked to the reasons why smaller lemur species have survived and why they are monomorphic. Larger animals need abundant resources as shown by the extinction of the giant lemurs which is not available in Madagascar. Also, adaptation may have allowed only smaller males in the existing species to survive therefore causing males and females not to differ in size in surviving generations.

Spider Monkey

 

Environment

Spider Monkeys are found in large tracts of undisturbed tropical rainforests from Southern Mexico to Brazil. They live in the trees where they use their long prehensile tail to help them move among the branches. They survive on fruits and nuts and help to disperse the seeds of the fruits they eat since they eat them whole.

Body Size and Sexual Dimorphism

Adult spider monkeys reach a size of about 20 inches long and a weight of about 14 pounds. They have a very strong 3 foot tail with a hairless tip that has grooves almost like a finger tip that they use for swinging in the trees. They have very long thin arms and legs that are the reason for their spider monkey name. They have very little sexual dimorphism and the female chooses a male to mate with from her group.

Environmental Trait Adaptation

Sexual dimorphism is not seen much in spider monkeys because the males do not need to be bigger to defend from predators or fight other males for the right to mate. It seems that living up in the trees and not being involved in choosing a mate made it useless for males to be larger in size. The environment does seem to play a big part in the lack of sexual dimorphism in spider monkeys.

Baboon

Environment

Baboons live in every environment in Africa and parts of Arabia. They live in the deserts of the savanna, in the Drakensburg mountains of South Africa, and the arid regions of Namibia and the semi-deserts of the southwestern Arabian Peninsula. They are omnivorous and can eat just about anything in their environment. Baboons can adapt to any situation and eat things from flowers, leaves, and seeds, to small animals that they can catch.

Body Size and Sexual Dimorphism

Baboons range in size from 20 inches long and a weight of 14 pounds of the guinea baboon, to 47 inches long and a weight of 90 pounds of the Chacma baboon. There is extreme sexual dimorphism in all species of baboons which includes size, canine development, color and some males have large white manes. For example the Hamadryas baboon is usually about twice as big as the female.

Environmental Trait Adaptation

Due to the fact that baboons live in harem type societies it is important for the males to be larger to be able to control his troop of females and be able to compete against other males for mating rights. They are also terrestrial animals and sometimes need protection from predators. For these reasons baboons exhibit sexual dimorphism that may have been influenced by their environment.

Gibbon

Environment

Gibbons are found in Southeast Asia and China in the evergreen tropical rainforests of the regions. They live in the trees and rarely are found at ground. Although they live in the trees they have not tails because they are actually apes. Gibbons travel through the forests by swinging through the tree tops. They eat a variety of fruits, figs, berries, leaves, vines, insects, and bird’s eggs.

Body Size and Sexual Dimorphism

Gibbons weigh about 20 pounds, are about 3 feet long and show very little sexual dimorphism. With most gibbon species males and females are about the same size with the exception of maybe the siamang gibbons, but even then the difference is slight. Gibbons are the smallest of the apes with long arms and legs to use for swinging in the trees. They are also known for pair bonding or being monogamous to their breeding partner.

Environmental Trait Adaptation

It seems that due to the fact that gibbons are arboreal with very few predators and the fact that they are somewhat monogamous, they really have no need for sexual dimorphism. There is no need to fight off predators and very little competition against other males so size does not seem to be an issue. These smaller apes are also able to survive with lesser resources in their environment.

Chimpanzee

Environment

Chimpanzees are mainly found in equatorial forest belt stretching across Central Africa. They are mostly found in dense tropical forests but can also be found in woodlands and swamps. Chimps usually eat and sleep up in the trees but they also do spend a good amount of time on the ground. They eat a variety of foods like fruits, flowers, leaves, insects, eggs, seeds and small animals. Their main predators are leopards.

Body Size and Sexual Dimorphism

Chimpanzees do have sexual dimorphism with the average male weighing 150 pounds and females weighing up to 100 pounds. They have long strong arms that they use to swing from tree branches and short bodies.

Environmental Trait Adaptation

It seems that spending time on the ground while having some predators may be part of the reason males are larger than the females. Males also need to compete with other males for females and the position of alpha male. Larger males can better protect their communities and allows males to compete for a better position in their community group. The chimpanzee environment does seem to have an effect on their sexual dimorphism.

Summary

It seems evident that the environment of an animal has a direct effect on their physical and behavioral traits. It is clear that the environments of the primates that were compared had a direct effect on the sexual dimorphism of each group. Primates that spend more time on the ground like baboons seemed to have more sexual dimorphism and larger body size in general than primates that spent more time in the trees. It also seems that primates in harsher climates like the lemurs in Madagascar were smaller in general and lacked sexual dimorphism, while the larger primates did show sexual dimorphism and probably have better resources for food. A lack of competition over mating or having females choose their mates also affected the lack of sexual dimorphism in some of the primates. In all, it seems that the environment of an animal has a great effect on their physical and behavioral traits.