Woolly Monkey Research


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Vocalizations & Displays in the Common Woolly Monkey (Lagothrix lagothricha): 

Vocalizations & Displays in the Common Woolly Monkey (Lagothrix lagothricha) Lindsey Hughes Senior Research Fall 2002


Introduction Lagothrix lagothricha is also known as Humboldt’s Woolly Monkey Found only in South America in the Amazon River Basin of Brazil, Columbia, Ecuador, Peru, and Venezuela Range in all canopy layers of primary forest, in rain forests, in gallery forests, and have been found in mountainous areas and cloud forests up to 3,000 meters




Morphology The largest monkey in South America with the female weight averaging 11 pounds and the male weight averaging 15 pounds Have a prehensile tail that can support their full weight and is used for feeding and locomotion Have dark brown, pale brown, dark gray, pale gray, reddish-brown, or black fur with a black face and pink palms of the hands and feet Sexual dimorphism exists: the canines, body, and head are longer in males; the tail of the female is longer than the male; and the female’s clitoris is longer than the male’s penis, which makes it difficult to determine sex in the wild


Ecology Primarily frugivorous, but also feed on leaves, seeds, flowers, and some invertebrates and small mammals Group size averages 10-12 group members, but groups up to 70 members are known to exist Not territorial; allow group ranges to overlap (known to forage alongside other groups as well as other species in their family Travel through the forest quadrupedally using its tail as a 5th arm Rarely come down to the ground, almost totally arboreal; when on ground, they walk bipedally

Social Structure: 

Social Structure Multi-male-multi-female group with hierarchy between the males determined by play-fighting & age Polygamous mating system; most dominant male gets most copulations; only one female is copulated with at any given time Most dominant male receives most social grooming & are known to protect mothers and their infants from others in the group Adult and subadult males are dominant over all others in group

Social Structure Con’t: 

Social Structure Con’t Males are philopatric (they remain in the group in which they were born, called natal group) while females leave their natal group Female dispersion usually occurs between the ages of 5 1/2 & 6, the same ages that females begin to mate Females remain sterile & do not conceive until 1-3 years after leave natal group Gestation period averages 7 ½ months, or about 223 days Female gives birth to 1 young every 2-3 years; infants nurse from 16-20 months & travel independently by 6 months

Previous Research: 

Previous Research Little research on woolly monkeys exists, with research on behaviors & vocalizations being almost nonexistent Behavioral and vocalization research was done by M. Ramirez in 1988; made a “dictionary” of behaviors & vocalizations that explained the behavior or reason behind each vocalization, which he spelled out using human phonetics (English language) Also explained some of their visual communication Something about his research not having anything to do with mine

Research Methods: 

Research Methods Conducted at the Louisville Zoo, which is one of only 2 places in the world with a captive family troop; the other is London Before beginning the data collection process, I spent a few weeks just observing the 2 troops to become acquainted with the individuals Became familiar with their behaviors and vocalizations During those weeks I compiled a list of observed behaviors

List of Behaviors: 

List of Behaviors Eat Play Chestrub Swing Walk Quadrupedally Fight Groom Walk Bipedally Teeth Chatter Jump Climb Cage Climb Rope Cage Shake Rub Grasp With Tail Stare Hump Copulation Attempt Run Yawn Lick Masturbate Feel On Genitals Reach For Me Rest Sneeze Drink Scratch Hang Reach Out Of Cage

Data Collection Methods: 

Data Collection Methods 8 mm video camera to record behaviors Mini disk recorder to record vocalizations Proprietary Palm Pilot program to record the movement and behavior of each individual was Pen Recorder & program for data analysis was Pen Reviewer.

Research Difficulties: 

Research Difficulties First, videotaped monkeys individually; not effective because could not see behavior of other monkeys and they move too fast to follow around the cage Then, videotaped sections of the cage; not effective because could not differentiate between individuals due to bad video camera resolution Mini disk recorder would not work, then it made extremely poor quality recordings that could not be used for analysis Palm Pilot program difficult because could not keep up with the behaviors while trying to remember the corresponding letter to write Certain monkeys were more active than others and this caused me to start and stop recording which did not heed good results

Data Analysis: 

Data Analysis Video recordings were digitized & transferred to compact disk for later analysis Could be analyzed at 1/10 of a second, giving ability to record the behavior at set intervals which allows the viewer to record the behavior of all monkeys in view Used sounds from video recordings for analysis with Sound Forge, which makes sound spectrographs, or sonograms of the monkey vocalizations Palm Pilot program data was analyzed in Pen Reviewer in the form of graphs, time lines, and matrices

Troop I: 

Troop I Family troop consisting of 4 related individuals Corey Sissi Sara Tomas

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