Behavioral Differences Between Male and Female Capuchin Monkeys
This scientific report examines behavioral differences between male and female tufted capuchin monkeys (Sapajus paella) housed in an outdoor artificial habitat at a North American zoo. Using time activity budget methodology, researchers observed a group of 15 animals — including adult males, adult females, a subordinate male, and juvenile males — for 2 hours and 15 minutes. Data were collected across six behavioral categories: resting, moving, feeding, foraging, grooming, and playing. Results indicate that males spent proportionately more time feeding and foraging while females spent more time resting. The findings support the hypothesis that sex-based differences in body size influence activity levels and energy expenditure within this captive population.
- Introduction: Species background, hypothesis, and study rationale
- Methods: Habitat description, group composition, and behavioral categories
- Results: Activity budget percentages by sex across six behaviors
- Discussion: Interpretation of findings, limitations, and future directions
- References: Cited sources in author-date format
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What makes this paper effective
- The paper follows a standard scientific report structure (Introduction, Methods, Results, Discussion, References), making it easy to navigate and appropriate for an undergraduate natural science course.
- The hypothesis is clearly stated and directly tied to a biological rationale — sex-based differences in body size and metabolic demands — grounding the predictions in established theory.
- Quantitative data are presented in a clear tabular format, allowing direct comparison of male and female activity percentages across six behavioral categories.
Key academic technique demonstrated
This paper demonstrates the use of an activity budget as a structured observational tool. Rather than describing animal behavior qualitatively, the student operationalizes behavior into discrete, timed categories and converts raw observation data into percentages. This technique, grounded in Altmann (1974), shows how systematic data collection transforms field observation into quantifiable, comparable evidence.
Structure breakdown
The paper opens with an abstract-style summary paragraph before moving into a formal Introduction that contextualizes the species, the research gap, and the hypothesis. The Methods section describes the habitat, group composition, and behavioral categories. Results present data in a table, followed by a brief interpretive note. The Discussion connects findings back to the hypothesis, acknowledges limitations (small sample size, single observation period), and proposes future directions. References follow APA/author-date conventions.
Introduction
The tufted capuchin (Sapajus paella) is a brown or black-furred primate from South America with a natural range that includes the Amazon basin (Groves, Wilson, and Reeder 2005). Behavioral differences between male and female capuchins in captivity are not well understood. The purpose of this study is to determine whether there are average differences between male and female groups within a captive population of capuchins. The hypothesis is that male capuchin monkeys will be more active in feeding and less at rest, due to differences in body size between the sexes. Studying the behavior of both sexes across specific time intervals and different activities will be used to create an activity budget. The data will then be analyzed to determine if there are notable differences between the two sexes.
The theory behind an activity budget is based on the amount of energy that an animal must expend to perform different activities. Metabolism places limits on how long an animal can remain engaged in a given activity — such as foraging, sleeping, traveling, or interacting with other animals (Bobick 2004). Factors that influence metabolism can include sex and relative physical size.
Tufted capuchins are small, brown to black primates with a head-body length of 30–60 cm and weights between 1.7 and 5 kg. Males are generally larger than females.
The association between food acquisition and sex in capuchin monkeys has been studied with regard to foraging and the share taken by the finder of food (di Bitetti 2001). In addition, the relationship between cooperation and pay-off for capuchin monkeys has been studied to determine energy and activity patterns for monkeys alone and in groups (de Waal 2002). The relationship between differences in activity for male versus female monkeys has not, however, been studied in an artificial zoo habitat. The assessment of tufted capuchin monkeys through an activity budget approach is used here to test the stated hypothesis for this population.
Methods
Time activity budgets were collected for a static, captive population of tufted capuchin monkeys. The population is housed within an outdoor habitat at the San Diego Zoo in San Diego, California. The habitat is an outdoor open facility with visibility through netting and windows for zoo visitors. The capuchin population is a single group within a habitat dedicated to them, with no other species of primates or other mammals present.
The capuchin habitat is approximately 10 meters long and 5–10 meters deep, roughly oval in shape. The group is provided with multiple areas for play and interaction, including ropes, real and simulated trees, platforms, and hammock structures. The group is fed on feeding platforms and has access to water at multiple locations. The habitat receives both sun and shade, and the group has access to an indoor facility. The entire site is visible from multiple viewing locations, and the animals are desensitized to observers through near-continuous observation by zoo attendees.
The tufted capuchin typically lives in social groups of two to twenty animals. Groups contain one dominant male and may include multiple subordinate males along with a group of females (Groves 2005). The capuchin diet is omnivorous, and feeding is often governed by a social hierarchy led by the dominant male and a select group of preferred females (di Bitetti 2001).
The group was observed for 2 hours and 15 minutes in a single observation period. Animals were counted and classified according to the following categories:
The following behavioral parameters were established for observation, and the relative time spent in each was recorded for individual animals:
Data were collected by visual observation and recorded manually. Averages were calculated and differences between male and female animals are presented below.
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