User:CooperOfford/Squirrel monkey

The content of the Squirrel Monkey page on Wikipedia is relevant to the topic, but it is narrow in scope. The leading section is informative and the taxonomy section provides detail, while maybe lacking citation. Following this is a tiny section on evolution that needs more work, as well as sections on descriptions, behavior, ecology, and color vision. The description section looks okay but it is lacking citation. The color vision section is interesting and informative with good citation but the behavior and ecology section needs more information and citations. I think there should also be more sections on mating systems, reproduction, physiology, biogeography, distribution, etc. The article is written with a neutral tone. I think I could add to this article by making it much more extensive in the information it provides, and I could add some stuff relative to what I'm learning in class with physiology. Most of the citations look to be reliable journals and institutions.

Additions I'm going to make:

First, I'm going to add a few things to the lead section to make sure it briefly touches upon the content of the article. I'm going to add sentences related to my additions and a summarizing sentence or two relating to other people's additions that they failed to add to the lead section.

Lead Section Additions:
There are two main groups of squirrel monkeys recognized. They are differentiated based on the shape of the white coloration above the eyes. In total there are 5 recognized species. Squirrel monkeys have short and close fur colored black at the shoulders, yellow or orange fur along the back and extremities, and white on the face. (This is collectively information I did not add, but that other people have added into the article and I think a sentence or two on it should belong in the lead section).

Squirrel monkeys have determined breeding seasons which involve large fluctuations in hormones and there is evidence of sexual dimorphism in males.

Squirrel monkeys can only sweat through the palms of their hands and feet and so must make use of other thermoregulation techniques such as behavioral changes and urine washing. These monkeys live in habitats of high temperatures and high humidity, making it essential for them to maintain proper osmoregulation if conditions pass certain thresh-holds. (This is information summarizing what I've added to the article). Color vision studies have also been performed on squirrel monkeys for the purpose of better understanding vision ailments in humans. (This is something someone else added, but I felt should have a sentence in the lead section).

Now on to the actual stuff that I've added to the article:

Reproduction, Mating, and Hormones:
Studies show that Saimiri collinsi time the weaning of their young with the period of time when there will be maximum fruit availability in the environment. This reduces the energetic struggles that newly weaned juveniles will face when transitioning from a milk diet where they are dependent on their mother for food to a more diverse diet where they have to forage for food. There is evidence that squirrel monkeys show sexual dimorphism during the breeding season. In the months leading up to breeding and in the months of breeding, sexually mature adult males have been recorded to increase in size by significant amounts relative to females. These size changes are caused by seasonal fluctuations in androgen hormones synthesized in the hypothalamus, pituitary, adrenal and gonadal axes. The fluctuations include increases in the concentrations of testosterone, androstenedione, and dehydroepiandrosterone levels in sexually mature males during the breeding season, peaking in January. Following the breeding season, these androgen concentrations drop. The evolutionary reasoning for these size changes in sexually mature males is suggested to be both intra-sexual selection among males and also female choice selection, as the larger males are more likely to be preferred by females and partake in more copulations. There is not clear evidence yet as to why females choose larger males, but a leading hypothesis is that the larger males are more likely to have better vigilance for their young.

Thermoregulation in Squirrel Monkeys:
Squirrel monkeys can only sweat through the palms of their hands and the soles of their feet. Sweating in these areas alone does not provide enough cooling for the monkeys to survive in the high temperature environments they live in, requiring them to use other methods to thermoregulate. They will use behavioral tactics such as seeking out shaded areas sheltered from the sun and also make use of postural changes to better dissipate heat from their body. They will also make use of an interesting technique to maximize evaporative cooling known as urine washing. The monkeys will urinate on their hands and rub the urine over the soles of their feet. The urine is then evaporated off the body in a cooling process. Studies have shown this behavior to be maximized during times of high temperature, highlighting its importance as a thermoregulatory behavior.

Osmoregulation in Squirrel monkeys
Squirrel monkeys are subject to both high temperatures and high humidity in their natural habitat. The humidity can range from 70% saturation in the 'dry' season up to 90% in the 'wet' season. Squirrel monkeys are able to tolerate up to 75% humidity with small adjustments in behavior and physiology that increase in significance as the humidity goes up. When reaching approximately 95% humidity, the monkeys have more drastic changes in osmoregulation in order to maintain homeostasis. As evaporative water loss decreases at these high levels of saturation, the monkeys will take in less water and create a more concentrated urine in order to maintain proper ion and water levels inside the body.

Cooperation Studies
Cooperation is largely evident in human primates. Squirrel monkeys do not often display cooperation in the wild, while many other nonhuman primates do. Studies have been done to suggest that female squirrel monkeys show disadvantageous inequity aversion as it pertains to food rewards. However, the same could not be said for male squirrel monkeys. More studies need to be done on squirrel monkey behavior to yield more information regarding why squirrel monkeys rarely show cooperation and if disadvantageous inequity aversion is a relevant factor.

Evolution Phylogeny
Diversification of squirrel monkey species appears to have occurred during the Pleistocene epoch, likely due to climatic changes associated with interglacial periods in South America at the time. The origin of squirrel monkeys in Central America is unclear, but a possible hypothesis is human transport. More genetic work needs to be done on the subject to reveal a true answer.