Tuesday, March 3, 2015

Comparative Primates: Size and Sexual Dimorphism

1.     Lemurs
a.     Though lemurs originated in extremely tropical regions such as North America, lemurs can now only be found on Madagascar and nearby Comoros Islands, islands just southeast of Africa.  Madagascar and the Comoros Islands are tropical islands with variations of hot, humid, and dry weather.  The islands contain a large variety of vegetation and species.  Madagascar is a fairly large island while the Comoros Islands are rather small.
b.     Typically, there are no sexual dimorphism with lemurs, but a few species of lemurs show sexual dichromatic, which is this difference in fur color between genders.  Lemurs are fairly small primates, weighing on average five to seven pounds.  However different species show different sizes, which can range from being just slightly bigger than a mouse to the size of a large domestic dog. 
c.      Since lemurs have a large amount of competition from other animals on the island, one way to survive is to live in the trees and reach the hanging vegetation.  They do not need a large body size to prey on other species; therefore their small body size was an adaptation to the environment.  With the small body size, the lemurs are able to swing and jump within the trees with ease.

2.     Spider Monkeys
a.     Spider monkeys can be found in the tropical rainforests of Central and South America.  Using their tail as a third limb, spider monkeys live in the upper parts of the trees in the tropical rainforests, swinging from branch to branch with ease. 
b.     Comparative to the lemurs, spider monkeys have very little sexual dimorphism.  The males tend to be slightly larger, at an average of roughly 25 pounds while the females are on average 21 pounds.  Other than the size, the spider monkeys can be indistinguishable between genders.
c.      Spider monkeys might have a smaller size in general because of their environment.  Living in the trees, having to swing from branch to branch, the spider monkey has an advantage with the smaller size.  I could also connect the size with the diet.  Though spider monkeys are omnivorous, they tend to eat a lot of vegetation since they live up in the trees.  The lighter diet could be a cause of the smaller body type. 

3.     Baboons
a.     Baboons have a more various living environment.  They can be found in savannas, rainforests, and the mountains of Africa and Asia.  They are semi-terrestrial animals, so they can live in both the trees and the ground. 
b.     The female and male baboons have big distinctions between the two.  Males are significantly bigger than females, and much more aggressive and protective of their females.  Males can be up to three times larger than the females.  Males also have a mane around their head and can have white or silver fur, while females are typically brown.
c.      The much larger body weight compared to the other two primates might be because they live closer to the ground and have a heavier diet.  The larger body type might be for defense, since they have more prey being closer to the ground or on the ground.  A reason there is such sexual dimorphism with baboons might be because the males take on a stronger role between the two, dominating their surrounding compared to the females.

4.     Gibbons
a.     Gibbons primarily cover a large area of Southeast Asia, usually inhabiting the middle to upper levels of the trees in the tropical and sub-tropical rainforests.
b.     Gibbons typically have little sexual dimorphism, yet males are slightly larger than females in body type.   Their body weight usually averages between 15-25 pounds, with elongated arms spanning over five feet.  Gibbons also have a loud call, used for warning and mating, and males usually have a louder call than females.  
c.      Their lightweight and lanky features are great for swinging through trees and racing away from predators.  The mating call might be a reason why male gibbons are not different from the females.  The males do not need to be bigger or different to attract the females, for they have the loud mating call.

5.     Chimpanzees
a.     Chimpanzees typically cover the middle and western regions of Africa in the savannas and rainforests.  They are semi-terrestrial animals depending on environment.
b.     Chimpanzees have a much denser body weight compared to the other primates analyzed.  Their weight can range from 70 to 250 pounds, females being much smaller than the males.  The males are also about a foot taller than the females on average. 
c.      The large body weight helps the chimpanzees fight off predators and dominate their prey.  The males’ larger size than the females are to attract the females and compete with the other males for reproduction.  The long arms are for swinging from tree to tree with ease. 



Conclusion:  The environment has a large impact on the differences in size and behavior with the primates.  Primates that live primarily in the trees and have a smaller diet usually have a smaller body size, while the primates that live closer to the ground and have more prey/predators have a larger body size.  I also noticed that the primates where the male and female share the parental responsibilities have little sexual dimorphism; while the ones with more mates and the females control the parenting have more sexual dimorphism, like chimpanzees and baboons. 

10 comments:

  1. Great discussion on lemurs and their expressed traits. Good connections made between their body size and their environment. How would you explain their body color differences?

    Good coverage of the spider monkeys. My only caution is the association of eating vegetation and being small. Gorillas eat primarily plant material and are the largest of all primates! There is a connection between size and diet but what you find is that smaller primates tend to eat higher protein/fat diets and larger ones tend to focus on vegetarian material. So where do humans fit in there? :-)

    Great connections made between the environment and the body size and dimorphism for baboons.

    Good discussion on gibbons. There are also coloration differences in gibbons. Is that difference an example of sexual dimorphism?

    Good analysis of the chimpanzees.

    Very good final summary. You made very good connections throughout with regard to then environment and body size/sexual dimorphism. Good post.

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  2. I really enjoyed your blog explaining the differences in size and sexual dismorphism in the five primates. Your descriptions were informative. I found it interesting that when the male and female share parental responsibilities, they have little sexual dismorphism compared to those with more mates and females control the parenting. Great job.

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  3. Very good post. It was thorough and informative. I enjoyed reading it because before this I had no idea what sexual dimorphism even was and never gave any thought to it. It seems as if size was a big factor in the distinction which I thought was interesting because that is same with humans, in most cases.

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  4. Hey Laura,
    I enjoyed reading your post, the information in it was similar to that of which I found. I had the diet portion and it is cool to see how the monkeys who live on the ground and have a larger diet are bigger, and the ones in trees who eat fruit and stay clear of predators have a small build.

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  5. Great post! It was very informative. The size and sexual dimorphism of each primate was explained well. You also gave me a better understanding of the level of influence the environment has on this particular trait.

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  6. The information you posted is very well organized and to the point. Your comments in regards of on the influence of the environment with the primate’s trait expression are also very interesting to read. I struggled on that part. The mating pattern of primates is very linked to the sexual dimorphism among primates. Other factors are also linked, such as the harshness of the climate, availability of food, or rather primates spend their times living on the ground or in trees. Great job!!!!

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  7. Great post you made as I think you covered all the main points in a very organized way. You got into specifics on every primate when it came to weight and diet as well as other aspects. Nice job with your post.

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  9. Hi Laura,
    Since I didn't study this trait expression for my blog, I found your work particularly interesting. I thought you did a good job defining sexual dichromatic and dimorphism. It is fascinating that animals vary in color in order to camouflage themselves in the nests, while others are brightly colored in order to attract mates. I also didn't know until this assignment that baboons have developed huge canine teeth for protection. I would have thought their large size would be enough of a deterrent for predators, but I'm sure having big, scary teeth helps as well. Nice work on this blog!

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  10. Good job on your post. I thought you did a good job covering all the things that were asked of us. I enjoyed reading the distinctions you gave to show us the difference between males and females. I found it interesting that they don't necessarily have to be different in size to tell them apart, but that we can easily do it by looking at their fur. Good job again! Good post.

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