Study Notes on Rhesus Monkey Commensalism in India

Population Surveys: 88% of sampled rhesus monkeys in commensal or semi-commensal habitats in 1959-60 and 86% in 1990-91.
Significant Shifts: Notable increase from semi-commensal to commensal habitats, minor increase in forest, non-commensal populations.
Group Size Change: Group sizes increased in five habitat categories, but declined in village and urban habitats.
Population Recovery: Rhesus populations in India are increasing post-decline, adapting to human pressures through increased commensalism.

Definition: Commensalism refers to organisms living closely with others for support without harming them.
Rhesus as "Weed" Macaques: Evolved in connection with people; excel in disturbed habitats (Goldstein & Dewar).
Habitat Preference: Found predominantly in agricultural zones, villages, towns, cities, temples, and near human infrastructures (roads, canals).
Human Dependency: Confirmed through studies showing high reliance on human-provided food sources (e.g., food handouts, agricultural crops).

Habitat Classification:
- Commensal Habitats: Close, frequent human contact (villages, towns, temples).
- Semi-Commensal Habitats: Intermittent human contact (roadsides, parks).
- Non-Commensal Habitats: Isolated forest areas, shy of people.
30-Year Comparison: Surveys conducted in 1959-60 and again in 1990-91 in different habitats, with varying methodologies due to environmental changes and population shifts.
Population Growth Factors: India’s population growth, urban expansion, agricultural changes.

1959-60 Survey Findings:
- 97% of rhesus in commensal habitats; reclassification showed 31.3% commensal, 56.7% semi-commensal, 12% non-commensal.
1990-91 Survey Findings:
- 3,059 monkeys surveyed; distribution changed to 48.5% commensal, 37.1% semi-commensal, 14.4% non-commensal.
- Table I: Habitat distributions for both years presented data on population density in various habitats.

Stability Across Time: 88% in commensal or semi-commensal habitats in both surveys, stability noted despite population dynamics.
- Increased commensalism reflects ecological adaptability.
Changes Observed:
- Shift from semi-commensal to enhanced commensal lifestyles due to urban pressure, increased agricultural production.
Impact of Environmental Changes:
- Rhesus adapted to urban sprawl and agricultural settings due to lack of trapping and closer ecological associations with humans.
Group Dynamics: Larger group sizes in forested and semi-commensal environments, smaller sizes in highly urbanized spaces due to human disturbances.

Commensal Living: 85-88% of rhesus live in commensal or semi-commensal habitats.
- Shifts over time indicate adaptability and evolving human-monkey interactions leading to greater commensalism.
Overall Increase in Population: Benefits from the ban on trapping for export and economic improvements contribute to population growth despite urbanization.
- Continued research necessary to understand dynamics and impacts of urban development on rhesus

Study supported by various U.S. Public Health Service grants and local institutions in India, acknowledging contributions from many researchers and assistants.

Numerous studies cited outlining previous research on rhesus monkeys and their ecology across various habitats in South Asia.