Draft#1 All you want to know about the Red Backed Squirrel Monkey
This discussion topic submitted by Leela Sequeira (
lee_seq@yahoo.com) at 8:34 pm on 4/26/01. Additions were last made on Sunday, October 27, 2002.
Decline of the Red backed Squirrel Monkey
General Introduction
Squirrel monkeys are small neo-tropical primates. There are up to five generally recognized species and 16 forms of sub species. Specialized studies have shown that squirrel monkeys have a long evolutionary history independent of other primates. These studies are strengthened by the derived features they share with other new world primates (Thorington, 1985).
Location and Genecology
Squirrel monkeys are found throughout the Amazon Basin with isolated populations found along the western Panama and Costa Rica border as well as in eastern Costa Rica, which indicates that this species had a much larger distribution in the past (Cooper, 1968; Hershkovitz, 1984; Thorington, 1985). The hypothesis that man could have introduced the squirrel monkey in Central America has been rejected because of the distinctive form of Saimiri found in these regions. Known climatic changes of the Pleistocene Age must have therefore dispersed the Saimiri during a short period when the forests were extensive. Within the genus Saimiri there are two generally recognized groups of squirrel monkeys, determined by the shape and color of the pelage of the upper eyebrow. These groups are commonly called the Roman arch type and the Gothic arch type. The red backed squirrel Monkey belongs to the Gothic arch type group.
Introduction to Red back squirrel monkeys
Along with 13 other mammals the Red backed squirrel monkey are classified as threatened species in Costa Rica (IUCN Red list of threatened Animals). A common name for this monkey is Mono Titi, while its zoological name is Saimiri oerstedii (although some times treated as a sub species of Saimiri sciureus by some taxonomists). It is an endemic primate native to Costa Rica's central Pacific coast. There are less than 2,000 squirrel monkeys of the sub species Saimiri oerstedi citrinellus which is endemic to the central pacific coast of Costa Rica. The red back squirrel monkey gets its name due the notable golden red coloration of their backs. Adult female red backs have black crowns while males and juveniles have gray crowns.
Their Environment and Ecology
The range of red back squirrel monkey has always been restricted to the Pacific lowlands of Costa Rica and Panama. They can be found in primary and secondary forests and in cultivated areas and appear highly flexible in their ability to adapt to different environments and in some geographic areas appear to prefer disturbed habitats (Konstant and Mittermeier, 1982; Boinski, 1987b). Disturbed and early successional habitats are advantageous because of their greater supply of preferred food. They are omnivores and their diet consists mainly of insects, such as grasshoppers, and small berry-like fruits. Crops are raided when nothing else is available.
These monkeys weight up to 1kg and they rarely travel on the ground. Being diurnal they are most active in the morning and late afternoon. A local population of Central American squirrel monkeys probably uses only 1 or 2 trees for sleeping sites. Central American squirrel monkeys travel and forage almost exclusively on branches between 1 - 2 cm (0.4 - 0.8") in diameter and rarely make horizontal leaps longer than 2 m (6.6'). They move in large group sizes (40 - 70) in continuous forest. It was thought that these groups tended to break up during the day for foraging in smaller groups, rejoin for a time during the day for a rest period and then continue foraging separately until coming back together for the night (Thorington, 1967). More recent reports find that these groups tend to forage as cohesive groups and explain the earlier reports as documenting the use of several large fruiting trees at one time by the same troop (Mitchell, 1990). Boinski (1987b) found that in Costa Rica squirrel monkeys tend to forage more widely and rest less when food is scarce during the peak wet season and travel least during the birth season. Studies of these monkeys in Costa Rica indicate that they are highly egalitarian and non-aggressive, with neither males nor females appearing to be dominant over the other sex. These studies also indicate that a female member readily changing troops with no aggression from either resident male or female troop members. (Boinski et al. 1998) A female matures faster (3years) as compare to males (5 years) but they both become independent when they are 1 year old. The yearly reproductive cycle has been shown in some field studies to be related to annual rainfall cycles and thus seasonal food availability with the birth season occurring at the period of greatest food availability insuring the female adequate nutrition post-parturition (Dumond and Hutchinson, 1967; Baldwin, 1968;Dumond, 1968; Thorington, 1968; Baldwin and Baldwin, 1981; Boinski, 1987a). Changes in light cycles have also been shown to be related to the timing of the reproductive cycle (Rosenblum, 1968; Follett and Follett, 1981) as has humidity level (Dumond, 1968). Boinski (1987a) in her field studies in Costa Rica found a strong tendency towards birth synchrony in this species, which she suggested might be an anti-predator adaptation.
Treats to this species
Initially the 1950's trapping for pet trade, a yellow fever epidemic, and the tropical storm Gert (September, 93) and the hurricane Caesar (July, 1996) all led to the reduction in population of this species. Currently, deforestation and habitat fragmentation due to agriculture and tourism development are the major causes of the red backed squirrel monkeys decline. Due to fragmentation of its original habitat, 42 separated subpopulations are found in the area. (MANP). Insecticide spraying, the pet trade and electrocution from electric power lines have also adversely affected these squirrel monkeys. The Central American squirrel monkey rarely descends to the ground; therefore, any break in the forest, such as for roads or for telephone or electric power line rights of way, can severely fragment a troop's habitat. Biologists are concerned that this shy monkey may be easily stressed by crowds of enthusiastic tourists, who throw stones and shake tree branches in an attempt to see the monkeys (Jukofsky 1996). Other problems include a skewed sex ratio, failure to locate mates, disease, genetic drift, inbreeding, depression, fighting, reduction of populations of prey animals, and poaching. Long-term monitoring of isolated populations of Central American squirrel monkeys indicated that local extinction was almost certain when a group contained less than 15 members and had less than about 30 hectares (75 acres) of available habitat (Boinski et al. 1998).
Conservation methods employed
These populations will require intensive management to survive in its current fragmented distribution or in re-established populations. In order to be able to manage the forests in a deliberate way to conserve biodiversity, it is essential to maintain a region of the forest with minimal human disturbance. Conservation and proper management of such forest are hampered because there is little knowledge about the total number of species in these regions. A factor that effects the extinction rate of certain species is the amount and spatial arrangement of a forest altered or destroyed. (Tropical deforestation and Species extinction"Whitmore.C). Priorities can be set in management of these forests by understanding deforestation and the implications caused on species. Loss of genetic diversity is another important factor in conserving this squirrel monkey especially since it is nearly extinct.
Conservational Efforts
There have been a lot of concerns about the decline in populations of red back squirrel monkeys. Jard’n Gaia (hard-een guy-uh, or Earth Garden) is one such educational and protection agency in Costa Rica that has played an important role in nursing red back squirrel monkey populations. The initial goal of the center was to breed endangered species in captivity and release the offspring into the wild. It was soon realized that, if possible, it was more feasible to rehabilitate a confiscated animal, liberate it and let it reproduce in its natural environment. This is now the primary objective of Jardin Gaia. Jardin Gaia is heavily involved in conservation at a local level and focus mainly on the squirrel monkey (Saimiri oerstedi citrinellus). In the past the center had partially funded various studies of the squirrel monkey (Saimiri oerstedi citrinellus), these include testing the content of hormones in the feces, blood sampling to determine the level of inbreeding through DNA similarity, and the distribution of the subspecies in the country. By 1992, conservation both in-situ and ex-situ through the Manuel Antonio Foundation for the Squirrel Monkey Conservation was started. The government along with the national Parks later began funding this project and officially recognized it as the Pilot Project for Wildlife Rescue Center & Botanical Garden in the Central Pacific Conservation Area (1/8 of whole Costa Rica). The best-known population (Wong, Thesis, 1990) is in Manuel Antonio National Park So far six troops live in the park, and eight more in the surrounding area (Wong, 1990). This habitat has been reduced by 30% (estimate) in the past 5 years and currently planned developments will reduce this habitat another 30% in 5 years (estimate). (Jardin Gaia, 1997, wildlife and about JG, available at: http://www.csn.ul.ie/~gwh/jg/wildlife.html accessed on April14th 2001).
References:
Web sites:
1)Animal info: www.animalinfo.org/species/primates/saimoers
2)www.saimiri.usothal.edu/prl/index.html
3)www.csn.ul.ie/~gwh/jg/wildlife.html
Books:
1)Handbook of squirrel monkey research, Leonard Rosenblum and Christopher. L.Coe, Plenum Press, NY
2)Tropical Deforestation and species extinction, Whitmore . C
3)Squirrel monkeys Thorington, 1985
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