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NWP Global Registry of Apprentice Ecologists - Orellana Province, Ecuador

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Orellana Province, Ecuador
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Registered: February 2015
Posts: 1
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Population Assessment of a Primate Sanctuary:

Population Census of the Common Squirrel Monkey (Saimiri sciureus) on Sumak Allpa, Orellana Province, Ecuador

Abstract. A population assessment of the common squirrel monkey (Saimiri sciureus) was carried out from April 14 to May 4 of 2014 on Sumak Allpa, a 113.5 hectare-island along the Napo River located within the Ecuadorean Amazon. The overarching objective of the study was to conduct a population census and evaluate the growth of the population in accordance with previous data. 30 direct observation periods occurred in the mornings between 6 am and 9 am and in the afternoons between 3 pm and 6 pm. Results demonstrate three large troops, one small troop, and one solitary monkey inhabiting the island, with approximately 55 to 60 individuals currently in existence. Such data favorably demonstrates a constant growth rate in the population of the common squirrel monkey on Sumak Allpa, as 21 individuals were observed in November of 2012. Challenges were particularly encountered in determining the composition of the troops relative to gender, largely due to the agility and the small size of these primates. Moreover, only four occasions or 13.33% of the time constituted aggressive behavior, suggesting that the troops are not currently competing for food. Conclusively, the population census indicates a healthy population on the island that is steadily increasing, thus supporting the need to initiate the liberation process of such primates in approximately one year. Such a process heavily depends on telemetry methodology and increased funding.

Resumen. Desde el 14 de abril hasta el 4 de mayo de 2014, se elaboró una evaluación de la población del mono ardilla (Saimiri sciureus) en la isla Sumak Allpa, cuya dimensión es de 113,5 hectáreas, ubicada a lo largo del río Napo dentro de la Amazonía ecuatoriana. El objetivo principal del estudio fue elaborar un censo de la población, evaluar su crecimiento y generar un análisis comparativo, tomando en cuenta un censo preexistente. 30 períodos de observación directa se produjeron en las mañanas de 06:00 am-09:00 am y por las tardes 15:00 pm-18:00 pm. Los resultados obtenidos en base de los estudios demuestran: tres grandes grupos, un pequeño grupo, y un mono solitario en la isla, la cantidad de especímenes divididos en estos grupos asciende aproximadamente a 55 a 60 monos. Estos datos demuestran favorablemente una tasa de crecimiento constante de la población del mono ardilla en Sumak Allpa, en comparación a noviembre de 2012. Fue un gran desafío particularmente encontrar composiciones sociales relacionadas a género en determinadas grupos de monos, en gran parte por la agilidad y el pequeño tamaño de los primates en cuestión. Por otra parte, solo en cuatro ocasiones el 13.33% del tiempo, mantenían un comportamiento agresivo, lo que sugiere que los primates no están actualmente compitiendo por los alimentos. En conclusión, el censo indica un promedio en la isla cuya población está en constante aumento, lo que apoya la necesidad de iniciar el proceso de liberación de estos primates hacia lugares más convenientes en aproximadamente un año. Ese proceso depende en gran medida de la metodología de la telemetría y el aumento del financiamiento.


The Amazon Biome:
The Amazon encompasses both the world’s most extensive tropical rainforest and river basin, extending 6.7 million km2 and across nine different countries of South America: Ecuador, Brazil, Peru, Colombia, Venezuela, Bolivia, Guyana, Suriname, and French Guiana. Ecological and evolutionary specializations, coupled with geographic isolation, have allowed for unparalleled biodiversity and endemism to occur in this region (Garber, 2009), which encompasses one in ten of the known species on Earth (World Wildlife Fund). Presently, the staggering array of flora and fauna includes at least 40,000 plant species, 427 mammal species, 1,298 bird species, and 3,000 freshwater species (Silva et al., 2005). Accordingly, “In recent years tropical rainforests have begun to receive a great deal of attention on account of their uniquely high species richness and ecological complexity, and the rapidity with which they are being destroyed” (Gentry, 1993). Increased deforestation rates are directly related to the growing human population, consequently allowing for various anthropogenic disturbances. The continent of South America experienced an annual population growth rate of 1.1% in 2011, with a 1.6% rate in Ecuador as of 2012 (The Word Bank: Ecuador).

Specifically, the Ecuadorean Amazon is commonly referred to as the “Oriente,” occupying 5.5 million km2 of tropical moist broadleaf forest across the eastern lowlands of Ecuador (Ecuador Nature Expeditions). Despite the nation’s relatively small size that covers less than 0.2% of the planet (Sumak Allpa), Ecuador continues to represent one of the most biologically diverse places on Earth. The country, however, continues to face a 1.5-1.8%-annual rate of deforestation (Garber, 2009), categorizing the country among one of the highest deforestation rates in Latin America. According to the UN-REDD Program, “almost 200,000 hectares of forest are lost each year to deforestation, which produces about 55 million tons of GHG emissions each year,” thus displaying an urgency to reduce deforestation and environmental degradation while also developing sustainable forestry management. (UN-REDD). With such objectives, Ecuador can continue to represent a country of incredible biodiversity.

Philosophy of Sumak Allpa:
The study was conducted through The Sumak Allpa Foundation, a non-profit organization established as a primate sanctuary in 2005: “Sumak Allpa” translates to the “land of no pain.” The island encompasses 113.5 hectares, located on the eastern side of the Ecuadorian Amazon and bordering the Napo River. Approximately 78-80% of the island consists of primary forest, suggesting the pristine forested areas throughout the island (Vargas, personal communication, 2014).

Sumak Allpa is a secluded sanctuary for 6-9 different species of primates in Ecuador, with 7 species currently existing on the island: the common squirrel monkey, the woolly monkey, the black-mantled tamarin, the golden-mantled tamarin, the saki monkey, the pigmy marmoset, and the owl/night monkey. This organization upholds a unique philosophy different from other primate centers, aiming to rescue, rehabilitate, and repopulate threatened species that are not in captivity; all of the primate species live freely on the island without any human intervention. Through such management practices, the sanctuary aims to foster natural survival skills for the primates, in hopes of reintroducing the animals into the wild, and thus, strengthen the ecosystems of Ecuador.

In addition to the management of primate species, Sumak Allpa works to preserve the culture and the language of marginalized indigenous communities in the Ecuadorean Amazon region, an area home to ten indigenous communities. Through the establishment of the Bicultural Education Bilingual School in the Loma del Tigre community, the foundation promotes greater access to environmental and cultural educational programs (Sumak Allpa).

Primate Rehabilitation Centers:
The four overarching justifications for establishing a primate sanctuary include the accommodation of rare species, the local education of one’s natural heritage, the economical benefits produced by tourism, and the ethical grounds upheld to promote primate conservation (Schoene & Brend, 2002). Approximately 130 primate sanctuaries are currently established worldwide, with 48 sanctuaries located in the Americas; in fact, Sumak Allpa represents one of only two primate sanctuaries in the Americas with squirrel monkeys (Leichter, 2012).

Primate sanctuaries tend to face the two major challenges of overcrowding and of negative impacts to the habitat. Firstly, many sanctuaries allow the primate populations to surpass the capacity of the region, in which “the ‘supply’ of primates exceeds the ability to care for them, and/or the availability of safe and appropriate areas in which they can be released” (Schoene & Brend, 2002). Secondly, many sanctuaries allow for the increased degradation of the natural habitat as a result of overcrowding; “The care for an endangered species must also include the care for its habitat. It does not seem justified to tolerate and even actively promote the destruction of a part of this habitat while trying to protect some members of the species” (Schoene & Brend, 2002). Instead, sanctuaries have the potential and the responsibility to mitigate habitat destruction, and thus, positively contribute towards conserving both the wildlife and the habitat of the region.

Accordingly, professionals at the Centre for Wildlife Management at the University of Pretoria in South Africa, offer a threefold solution in order to stray away from the issues formerly discussed: 1) through effective organization, planning, and qualified staff, sanctuaries must reach an appropriate level of professionalism that cannot be criticized, 2) through adequate funding, the sanctuary can establish essential facilities and employ qualified staff, thus enabling the sanctuary to invest in improved outreach and educational programs, and 3) through long-term conservation programs, sanctuaries can operate in a manner that relies on constant presence and example, allowing for an enduring conservation ethic (Schoene & Brend, 2002).

In the Ecuadorian Amazon, the amaZOOnico Animal Rescue Center located within the Selva Viva forest, is representative of an effective primate center in Ecuador, upholding the overarching goal of liberating species into the wild – working to rescue, rehabilitate, and release primates (amaZOOnico). On several occasions, however, the primates of amaZOOnico have returned due to their reliance on a constant food source (Vargas, personal communication, 2014). Most other primate centers in Ecuador are representative of zoos and/or wildlife exhibition sites; “The fundamental difference between an animal sanctuary and a zoo is that all animals in a sanctuary are rescued and not held captive for the primary purpose of display, breeding, or research” (Schoene & Brend, 2002). While Sumak Allpa has not currently released any individuals into the wild, this sanctuary could potentially be the first primate center in Ecuador to successfully translocate and repopulate primate species, resulting from a near-wild existence for the species.

History of Common Squirrel Monkey on Sumak Allpa:
Between the years of 2006 and 2008, approximately 20 individuals of the common squirrel monkey were introduced to Sumak Allpa, with most originating from the surrounding areas of Coca: the Madeira River, the Napo River, and the Auca Road region. As one of the most commonly found primate species in the illegal trade market, the monkeys were confiscated from various vendors. Naturalist guides in Ecuador embody the authority of park rangers, allowing such individuals to rightfully seize the primates (Vargas, personal communication, 2014).

Background Information of Common Squirrel Monkey:
Based on biogeography, comparative anatomy, and molecular evidence, New World primates, or platyrrhines, may have reached South America 26 million years ago; “Currently, there are 19 genera, 7 subfamilies, and 199 recognized species and subspecies of New World monkeys, making platyrrhines one of the most taxonomically, behaviorally, and anatomically diverse primate radiations” (Garber, 2009). Significantly, primates of South America embody unique reproductive biology, mating strategies, and social systems, attracting primatology research and conservation programs in recent years.

The common squirrel monkey, a New World species, is commonly found in various regions of the Amazon biome of Ecuador, with a distribution ranging across the provinces of Orellana, Napo, Sucumbíos, Pastaza, and Morona and Santiago. As diurnal and arboreal primates, they inhabit humid (sub) tropical forested areas at altitudes between 200 and 1200 meters (Tirira, 2007); they also prefer the sub-canopy and/or canopy levels of the forest with dense vegetation, branches, and vines – such as that of Sumak Allpa.

This small and agile primate species is uniquely characterized by a white mask of fur encircling its eyes, a black muzzle, a non-prehensile tail used for balance, and a grey or olive coat coloration with the bright gold color of its forelimbs, hands, and feet. Their diet is composed of ripe fruits and insects, in addition to nectar and flowers – spending most of the day in constant motion in search of food. These monkeys tend to be noisy with squeals and birdlike whistles while climbing and leaping through the forest for long distances (Emmons & Feer, 1997).

The social structure of common squirrel monkeys is complex, with approximately 10 to 100 individuals constituting each troop. During the day, troops will travel through the forest together, while also sleeping jointly at night (Tirira, 2007). With seasonal reproduction occurring once a year, mating occurs between September and November with births occurring between February and April. The birth season largely takes place during the wet season with the greatest rainfall, as an ample amount of food and water are available. Females nurse and care for their single infant until they reach independence, while the father takes no responsibility in caring for offspring. Males are generally 30-35% larger than females, coupled by brighter coat coloration, which result from sexual dimorphism – the phenotypic differences between males and females of the same species (Garber, 2009).

Threats to Common Squirrel Monkey:
While categorized by the IUCN Red List as a species of Least Concern, squirrel monkeys continues to face endangerment from increased deforestation, illegal trading, laboratory research, and hunting (IUCN). These factors have all contributed to the “serious decline in the biomass and survivorship of many primate populations leading to recent local extinction” (Garber, 2009). As previously discussed, the rapid rate in which the human population is growing in South America, and worldwide, directly contributes to anthropogenic disturbances of the environment. Human intrusion though colonization, petroleum, and agriculture have resulted in greater deforestation; primate species are consequently suffering from decreased habitat and resource availability. Furthermore, global climate change is also increasing the rate of various natural disasters, including droughts, floods, and fires that are degrading natural habitats that primate species depend on for survival (Leichter, 2012).

In addition to the detrimental effects of habitat destruction, squirrel monkeys are most commonly found within the illegal trade market to be sold as household pets, ideally due to their small size and adaptability. Studies have revealed that this species is frequently smuggled across country borders, being sold for “alarmingly” low expenses (Primate Info Net). Finally, primate species have often been utilized as subjects in laboratory research due to their phylogenetic similarity to humans and their stable population numbers; the squirrel monkey is the most frequently observed New World primate used for biomedical research. This has given rise to various ethical issues and increased public argument, as such primates are often deprived of natural social interactions and foraging activities (Abee, 1989). Squirrel monkeys are less hunted for bush-meat, and are more so exploited for the reasons outlined above.

Importance of Conducting Population Census:
First and foremost, conducting a population census allows for further analysis of the common squirrel monkey population on Sumak Allpa, indicating if the population is growing at a constant rate. Population data is also valuable in evaluating the overall progress of Sumak Allpa and its management practices, utilizing the study to demonstrate its success. Finally, such research can serve as a reference for future studies, providing an innovative assessment of the common squirrel monkey in Ecuador while facilitating projections about its population. In general, primate research in Ecuador is limited, starkly contrasting with ample research being conducted in Costa Rica and in Panama (Vargas, personal communication, 2014) – supporting why population assessments on Sumak Allpa are advantageous. Overall, monitoring wildlife populations is important to 1) evaluate the status and/or recovery program of a threatened or endangered species, 2) determine the status of (re) introduction of a wildlife species to an area, 3) define the biological and ecological health of an area, and 4) understand the effects of management practices and activities on a wildlife species (Witmer, 2005).

Previous Studies:
SIT alumna, Claire Leichter, conducted a population assessment of the common squirrel monkey on Sumak Allpa in November of 2012. Leichter’s research indicated one large troop on the island consisting of a maximum of 17 adults or juveniles and 3 infants, in addition to the presence of an independent individual. Utilizing the research of Latimer and Stout in 2011, Leichter calculated a positive growth rate of 0.875 births/month in 2011 and of 0.3075 births/month in 2012 (Leichter, 2012).

As indicated by Vargas, it is quite likely that more than one large troop existed during that time, suggesting that the common squirrel monkey population consisted of greater than 21 individuals in 2012. As Leichter was alone for the majority of the observation periods, the entirety of the island was not covered and various parts of the island were often excluded.

Primarily, this study aims to conduct a population census of the common squirrel monkey on Sumak Allpa. Secondly, population data collected during this study will be subsequently compared to the research of Claire Leichter from November of 2012. Thirdly, the composition of each troop will be determined, relative to gender. Finally, this study will analyze social interactions within individual or multiple troops, especially though aggressive behavior.

It is hypothesized that an increase within the common squirrel monkey population best indicates the health and the growth of the species. A constant population increase is expected due to natural reproduction and the pristine forest quality of Sumak Allpa.

Furthermore, an analysis of social interactions within individual or multiple troops, with a focus on aggression, is also assumed to indicate whether the common squirrel monkeys are presently competing for food, in addition to whether the population has exceeded the carrying capacity of the island.


Field Materials:
• Map of Sumak Allpa with trails
• Field notebook
• Writing instrument
• Binoculars
• Camera: Canon PowerShot (12.1 Megapixels)
• Insect repellent
• Machete
• Whistle
• Rubber boots and appropriate attire

Observation Period:
The study was conducted during 30 direct observation periods in the mornings and the afternoons between April 14 and May 4, with each period lasting for two to three hours. Morning periods ranged between 6 am and 9 am and afternoon periods ranged between 3 pm and 6 pm.

Field Methodology:
The first 18 observation periods were conducted from April 14 to April 25, using Huamak as a dividing trail between the east and west sides of the island. Different sides of the island were observed in the morning and in the afternoon, allowing for the entirety of the island to be surveyed. Remaining consistent with the 2012 study of Claire Leichter – date, time and climate (temperature and weather conditions) were all noted proceeding the observation periods.

After achieving an equal number of observation periods on the east and west sides (nine), the observation schedule changed beginning on April 27. Greater efficiency was achieved during the last 12 observation periods in going directly to the estimated home ranges and/or locations where troops were most frequently encountered. The expertise of Héctor, Miguel, and Mauro were collectively used on two occasions; in order to cover the entirety of the island, each individual traveled separately to different parts of the island on both the east and west sides. This allowed for a more widespread assessment of the common squirrel monkey population on the island, particularly in determining the exact number of troops.

Given the agility and the small size of the common squirrel monkey, troops were best identified by: 1) listening to rustling of trees as they climbed and leaped through the forest, 2) following and imitating their “chuck” calls, 3) observing fallen fruit on the forest ground, and 4) following the high-pitched noises of black-mantled tamarins. It was necessary to walk slowly and remain attentive to the preceding indicators of nearby troops while conducting fieldwork, which regularly involved two observers. Refer to the Appendix below for a table outlining the observation periods throughout the study.


Population Data:
After conducting the study from April 14 to May 4, there was found to be three large troops and one small troop inhabiting the island, estimating 58 individuals within the common squirrel monkey population on Sumak Allpa. Additionally, a solitary monkey was found to frequently join and separate from the small troop. Comparing such data to the population assessment of 2012, there are 37 more individuals present on the island.
Results are as follows:

Troop 1: 22
Troop 2: 12
Troop 3: 20
Troop 4: 3-4

Home Ranges:
The estimated home ranges and/or territories were concurrently determined while conducting this study. The map in Figure 1 below illustrates that four troops of the common squirrel monkey presently inhabit the entirety of the island; the corridor of guava trees travelling across the center of the island suggests why troops have occupied certain territories. Notably, the home ranges were best estimated based on geography and on population data, which were both fundamental in determining what troops belonged to each territory.

Home ranges of the common squirrel monkey are estimated to exceed no more than 30 to 40 hectares on Sumak Allpa. While biological literature states that territories usually extend across an area of 100 to 500 hectares (Emmons & Feer, 1997), it appears that territories are much smaller on the island, with approximated overlap as well. This is likely due to the limited size of the island, measuring 113.5 hectares itself.

Composition of Troops:
The table below outlines the number of female and male individuals observed within each troop during the study.

Social Interaction:
While collecting population data during the observation periods, aggressive behavior was observed 13.33% of the time, on four different occasions. Such aggression was witnessed within singular troops, and never among multiple troops – largely indicated by distinctive high-pitched screeches contrasting with their regular “chuck” calls. While such aggressive behavior was not always clearly observed, it is assumed that it more so occurred between male individuals.


Justification of Methodology:
Direct observation was the leading methodology used throughout the study from April 14 to May 4, requiring basic materials for carrying out fieldwork. The most essential materials needed during the observation periods included an island map with trails to note the location of observed troops, a field notebook and writing utensil, and binoculars to acquire an improved view of the primates. A machete was also necessary when following the troops through dense forested areas of the island. Ultimately, this study consisted of 30 observation periods within a span of three weeks, demonstrating its short nature. With increased observation periods and consistency, the study may have resulted in greater data and more accurate conclusions.

Limiting Factors:
A number of limiting factors were encountered during the observation periods, likely affecting the results of this study. First, the natural fluctuation of the water level of the Napo River, as well as the river movement generated by travelling motorboats, both allowed for flooding to permeate the island on a number of occasions. As a result, two afternoon observation periods on April 19 and April 20 were altered; on these dates, the study changed from observing the east side to observing the west side, avoiding the flooded areas. Additional climatic factors, relative to intense rainfall, also impacted four observation periods on April 24, April 29, April 30, and May 2. In general, the Napo River, a tributary of the Amazon River, extends across a region of 98445 km2, with the largest area located within Ecuador. The Napo River experiences an average monthly rainfall of 260 mm for approximately 12 to 20 days each month (Napo Wildlife Center) – providing reason for the frequent presence of precipitation during the study, as it occurred during the wet season of the Amazon biome.

Challenges were also encountered in locating the troops due to their agility and their small size, coupled with the dense vegetation and forested areas of the island. Consequently, it is possible and nearly inevitable that individuals were double counted during the observation periods. At one point during the study it appeared that five troops were inhabiting the island, however, four troops were eventually identified with greater investigation and with the assistance of additional observers. While the study demonstrated a total of 58 individuals within the common squirrel monkey population on Sumak Allpa, it is likely that the population more accurately ranges between 55 and 60 individuals.

Moreover, determining the composition of each troop, relative to gender, was particularly difficult during the study. Consequently, conclusions remain incomplete as demonstrated by Table 2 – providing reason for future studies in determining the composition of troops. Such an assessment appears helpful in understanding the multifaceted social structure of the common squirrel monkey. Finally, as aggressive behavior was only observed during four occasions, constituting 13.33% of the observation periods, it can be assumed that that troops are not presently competing for food and that resources continue to be available to the common squirrel monkey population of Sumak Allpa. Until the carrying capacity of the island has been met, the growth rate is expected to increase with every year.

Associations Between Primate Species:
Recent studies indicate that positive interactions among primate species are vital within ecological communities, suggesting, “primate diversity can be maintained when species partition habitat types, food resources, and vertical canopy structure in accordance with the classic paradigm of the fundamental niche” (Levi et al., 2013). One association among primates found in tropical forests includes that between the brown capuchin monkey (Cebus apella) and the common squirrel monkey (Saimiri sciureus), frequently found to feed and travel together up to 90% of the time; “This mixed-species association is particularly intriguing because Cebus is three times larger than S. sciureus and regularly preys on similarly sized mammals…” (Levi et al., 2013).

On Sumak Allpa, such an association was observed between Troop 1 of the common squirrel monkey and the black-mantled tamarins (Saguinus graellsi), with the two species frequently seen within the same vicinity. This relationship allows for greater efficiency in avoiding predators and foraging activities. Data collected during the observation periods, while also considering the study above, also indicate that these two primates species may occasionally separate from one and another – suggesting that further research is needed to understand primate associations.

Liberation Process:
Scientific literature demonstrates that primate reintroduction has been historically characterized by the lack of assessment and monitoring after releasing the species. With modern technology, it appears increasingly possible to better examine the outcomes of primate liberation; “Traditionally the use of telemetry has been used predominantly in ecological and socio-behavioral research projects for wild primates but the benefits of using telemetry for monitoring primates after release are increasingly recognized” (Trayford & Farmer, 2012). Challenges have revolved around locating primates, lacking human and financial resources, and tracking limitations due to geography.

One study from 2012 utilized questionnaires in order to survey various primate centers, including those with future plans to liberate species (questionnaire A), and those that have historically or are currently involved in releasing primates (questionnaire B). Significantly, results demonstrated that 60% of the respondents use, or have used, telemetry devices to assist with monitoring released primates. Interestingly, “In sanctuaries from the Americas, significant importance is placed on the problem of identifying the individual primates (17%) after release, more so than sanctuaries from other continents (Africa 6%, Asia 0%). This may be explained by larger numbers of small, often arboreal, primates released at one time that makes identification harder in comparison to primates released singly or in smaller social groups…” (Trayford & Farmer, 2012). Ultimately, technological advances and the long-term monitoring of primates collectively improve various challenges that are encountered by reintroduction programs.

Conclusively, the study conducted from April 14 to May 4 on Sumak Allpa indicates that a favorable population of approximately 55 to 60 individuals of the common squirrel monkey currently inhabits the island, resulting from healthy reproduction and a constant growth rate. As indicated by Vargas, this allows for the final goal of liberating a third of the population in approximately one year, maintaining a sufficient genetic bank on the island to avoid inbreeding. Such a liberation process highly depends on the success of telemetry methods (tracking devices), in addition to increased funding. The monkeys are only to be released to protected areas such as Yasuni National Park and other surrounding reserves. After reintroducing the primates, it is essential to analyze whether or not the primates are truly able to survive in the wild, reflecting the success of the Sumak Allpa Foundation (Vargas, personal communication, 2014). Fortunately, due to its unique conservation practices with species existing in a near-wild environment, it is expected that the primates of Sumak Allpa will thrive and enrich their ecosystems after being released into the wild.


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