FOW Newsletter Content for Spring 2013
20 Years – 4 PHOTOS
May marks the 20th anniversary of moving from the Psychology Building’s 3rd floor space into the
Chimpanzee and Human Communication Institute building. It was a long road for Roger, Debbi and the
chimpanzees. The new building brought sunshine, fresh air, green grass and room to move to the
chimpanzees’ lives and subsequently, lots of foot stomping, hugging and smiles.
The new CHCI also provided more space for the humans and with the ability to reach out to the public.
In 1994 the Chimposium program began. Now nearly 6000 visitors come each year to CHCI to learn
about chimpanzees and hear Washoe’s message of compassion. For most people it is a life-altering
experience to meet the chimpanzees.
In addition, decades of undergraduate and graduate students from around the world have gone on to
become PhDs, lawyers, veterinarians and animal caregivers. They work in African field sites preserving
not just chimpanzees but the forests and all that live in them. They run sanctuaries providing homes
safe from abuse and exploitation. No matter where life takes them, their experience and training at
CHCI made them ambassadors of compassion and respect.
We’re very proud of the impact Washoe’s family has had on the world over the last 33 years. Most
buildings are just concrete and steel, but CHCI has a heart and it is the chimpanzees.
Easter Egg-travaganza – 2 PHOTOS
by Shannon Wallin
We celebrated Easter on April 1st, so as an April’s fool joke we put out a ton of plastic eggs, but only
2/3rds had treats in them! The eggs were mostly filled with nuts and raisins, a small handful had a
sweet treat in them. The chimpanzees spent a lot of time foraging all over the WEST room. After the
forage they spent some time outside enjoying the sunny day.
Memory Monday – 5 PHOTOS
by Shannon Wallin
Every Monday on our Facebook page we post an old photo of the chimpanzees. We call it Memory
Monday! We have shoe boxes of old photos, so I looked through the boxes and found a bunch of fun
pictures and scanned them onto the computer to share. It is fun to see pictures of when the
chimpanzees were younger, but most importantly, it keeps the memory of Moja, Washoe, and Dar alive.
If you are on Facebook and haven’t liked our page, please do so and you will get to share in the
memories as well as a lot other fun stuff!
There are __ misc. PHOTOS to sprinkle throughout the research articles.
Captive Chimpanzee Preference for Environmental Enrichment: Naturalistic vs. Artificial
Savannah M. Schulze, Jessica M. Mas, RyAnn Stafford, and Mary Lee Jensvold
Abstract
The cognitive abilities of chimpanzees are complex and require challenging environmental enrichment
that promotes well-being and species typical behaviors (Fouts, 1998; Lutz & Novak, 2005). We examined
the use and preference of two types of enrichment for three adult chimpanzees living at the
Chimpanzee and Human Communication Institute (CHCI). These enrichment types included (1) artificial
items: magazines, drawing material, brushes, cardboard, toys, etc., and (2) naturalistic items (typically
found in a free-living environment): foliage, branches, etc. (Davey, 2006). We predicted that the crossfostered chimpanzees would demonstrate a preference for artificial enrichment. A chi-square test of
independence revealed that the frequency of time intervals during which the chimpanzees touched the
enrichment varied in the conditions in all three individuals. Overall, the chimpanzees touched
enrichment more in the naturalistic enrichment condition. Naturalistic enrichment often was edible,
which may account for the differences in conditions. The implications of these results will be discussed.
Introduction
Newberry (1995) defines enrichment as “an improvement in the biological functioning of captive
animals resulting from modifications to their environment” (pp. 230), whereas Mellen and Macphee
(2001) argue that enrichment has no single definition and should be redefined for each species. Effective
enrichment programs for captive chimpanzees promote species-typical behaviors and provide for
individual preferences.
Enrichment is categorized as environmental, structural, material, edible, or social. Environmental
enrichment includes enclosure size, complexity, and design. Ideally, enclosures should encourage a
variety of behaviors and provide escape outlets, privacy refuges, and visual barriers (Jensvold, Sanz,
Fouts, & Fouts, 2001; Fouts, 1998). Structural enrichment includes climbing structures and semipermanent items, such as large tires or hanging fire hoses. Edible enrichment includes food puzzles and
diet diversity. Social enrichment provides opportunities for interaction with conspecifics or human
caregivers.
Material enrichment consists of manipulable and destructible items, such as cardboard boxes,
magazines, play clothes, branches, and foliage (Fouts, 1998). Previous studies revealed that
chimpanzees exhibit preferences for manipulable and destructible material enrichment items over
indestructible ones (Fouts, 1998; Videan, Fritz, Schwandt, Smith, & Howell, 2005). Additionally, material
enrichment items should be consistently varied and changed to reduce monotony and boredom (Fouts,
1998). For this study, we examined material enrichment preferences for a group of captive
chimpanzees.
Methods
Participants: The three chimpanzees (Pan troglodytes) in this study resided at the Chimpanzee and
Human Communication Institute (CHCI), located on the campus of Central Washington University in
Ellensburg, Washington. Two of the three chimpanzees, Tatu (female) and Dar (male), were crossfostered, being raised by humans and immersed in an American Sign Language environment, much like a
child is immersed in any language environment (Gardner & Gardner, 1989). The chimpanzee Washoe
was part of the original cross-fostering projects, and the third chimpanzee participant in this study was
her adopted son, Loulis. Loulis acquired his signs from Washoe and other signing chimpanzees (Jensvold,
Sanz, Fouts, & Fouts, 2001; Fouts, 1994). These three chimpanzees lived together as a social group since
1981.
Facility: CHCI consisted of a suite of four interconnected night enclosures, two indoor exercise rooms,
and a large outdoor enclosure. All of the enclosures contained a variety of structural enrichment, and
the outdoor enclosure included additional features, including tall grass and bushes.
Conditions: There were two conditions: naturalistic and artificial enrichment. In the naturalistic
enrichment condition the chimpanzees received items typically found in a free-living environment, such
as foliage and branches (Davey, 2006). In the artificial enrichment condition the chimpanzees received
items such as magazines, drawing material, brushes, cardboard, and toys.
Data Collection: Data collectors were members of CHCI’s 2010 Summer Apprenticeship Program. They
collected data in 20-minute sessions using focal time sampling at 30-second intervals. For each time
signature, data collectors scanned each chimpanzee and marked T for touch, X for not touching, and NV
if the chimpanzee were not visible.
160
140
Frequency
120
ARTIFICIAL
ENRICHMEN
T
100
80
60
NATURALIST
IC
ENRICHMEN
T
40
20
0
TATU
LOULIS
Particpants
DAR
Figure 1. Enrichment Preference. This graph shows the number of times each chimpanzee touched the
two different forms of enrichment. Tatu spent the most time touching enrichment overall and
touched artificial enrichment the most. Loulis and Dar touched the naturalistic enrichment more than
the artificial enrichment.
Discussion
The three chimpanzees demonstrated individual preferences with regard to enrichment type with two
of the three preferring naturalistic to artificial forms of enrichment. In accordance with our hypothesis
that cross-fostered chimpanzees would demonstrate a preference for artificial enrichment, Tatu
interacted with artificial enrichment more often than naturalistic. Dar and Loulis demonstrated a
preference for naturalistic enrichment. As a cross-fostered chimpanzee Tatu was raised by humans in a
Western home setting since infancy. Tatu had the opportunity to use items similar to those used by
human children such as magazines, toys, and clothing items. This may explain her inclination to interact
with forms of enrichment that are more familiar. Her tendency to interact with enrichment on a more
regular basis may be indicative of individual preference.
Because our data was collected during intervals where visitors were present for educational workshops,
Dar and Loulis’ preferences for naturalistic enrichment may be attributable to species-typical display
behaviors often used by males (Goodall, 1986). In the wild, chimpanzee societies are philopatric and
territorial. Display behaviors are used to assert dominance and individuals often incorporate objects
found in their natural environment into these displays (Muller, 2002).
Naturalistic enrichment is also characteristically manipulable and destructible which supports previous
findings demonstrating that chimpanzees prefer these items over those that cannot be manipulated or
destroyed (Videan et. al, 2005). Naturalistic enrichment is often edible which could further explain a
preference for this type of enrichment over artificial enrichment. Our findings demonstrate that
individual preferences for enrichment types exist, and that the provision of a wide variety of enrichment
is integral to the well-being of captive chimpanzees.
Results
A chi-square test of independence revealed that the frequency of intervals with touching enrichment
varied with enrichment condition. Tatu touched enrichment more often in the artificial condition than
the natural condition, X2(df = 1, n = 779) = 40.75, p < 0.001. Dar and Loulis touched enrichment more
often in the naturalistic condition than the artificial condition, Loulis X2 (df = 1, n = 799) = 48.31, p <
0.001 and Dar X2 (df = 1, n = 799) = 24.98, p < 0.001. Figure 1 shows the number of times each
chimpanzee spent touching the two different forms of enrichment. Loulis and Dar interacted with
naturalistic enrichment significantly more than artificial enrichment.
References
Davey, G. (2006). Relationships between exhibit naturalism, animal visibility and visitor
interest in a Chinese zoo. Applied Animal Behavior Science, 96, 93-102.
Fouts, R. (1994). Transmission of human gestural language in a chimpanzee mother-infant relationship.
In R.A. Gardner, B.T. Gardner, B. Chiarelli, and F.X. Plooij (Eds.), The ethological roots of culture, (pp. 257270). Netherlands; Kluwer Academic.
Fouts, R.S. (1998). On the psychological well-being of chimpanzees. Journal of Applied Animal Welfare
Science, 1(1), 65-73.
Gardner, R.A., & Gardner, B. T. (1989). Teaching sign language to chimpanzees. Albany: State University
of New York Press.
Goodall, J. (1986). The chimpanzees of Gombe. Cambridge, MA: Harvard University Press.
Jensvold, M.L.A., Sanz, C.M., Fouts, R.S., & Fouts, D.H. (2001). Effect of enclosure size and complexity on
the behaviors of captive chimpanzees (Pan troglodytes). Journal of Applied Animal Welfare Science, 4(1),
53-69.
Lutz, C.K., and Novak, M.A. (2005). Environmental enrichment for nonhuman primates: Theory and
application. ILAR Journal, 46(2), 178-190.
Mellen, J., and Sevenich Macphee, M. (2001). Philosophy of environmental enrichment: Past, present,
and future. Zoo Biology, 20, 211-226.
Muller, M. (2002). Agonistic relations among Kanyawara chimpanzees. In C. Boescsh, G. Hohmann, and
L. Marchant (Eds.), Behavioural Diversity in Chimpanzees and Bonobos, (pp. 112-124). Cambridge, UK:
Cambridge University Press.
Newberry, R.C. (1995). Environmental enrichment: Increasing the biological relevance of captive
environments. Applied Animal Behavior Science, 44, 229-243.
Videan, E.N., Fritz, J., Schwandt., M.L., Smith, H.F. & Howell, S. (2005). Controlability in environmental
enrichment for captive chimpanzees (Pan troglodytes). Journal of Applied Animal Welfare Science, 8,
117-130.
Nighttime Enrichment Preferences of 3 Captive Chimpanzees (Pan troglodytes)
Amanda L. Carner, Kaeley Sullins, Lisa Wilding, Bonita Hendrickson M.S. and Mary Lee Jensvold Ph.D.
Introduction
• The goal of providing enrichment to captive animals, especially captive non-human primates is
to provide environmental stimuli that will be sufficient enough to provide optimal psychological
and physiological well-being. Many facilities accomplish this by providing animals with a variety
of items and the opportunity to make choices about the items provided. (Mellen & MacPhee,
2001)
• There are multiple types of enrichment techniques that can be used to enrich captive animal’s
lives. These include environmental enrichment devices, habitat enrichment, sensory
enrichment, and food enrichment as described by the Association of Zoos and Aquariums
(Association of Zoos and Aquariums [AZA], 2009). Our study focused on all types of enrichment
noted above.
• A successful enrichment plan and a clear sign of good welfare includes the animals appearing to
be relaxed, inquisitive, having a diverse non-stereotypic behavioral repertoire and spending time
engaged in grooming, play, and foraging. (Buchanan-Smith, 2011)
• According to Buchanan-Smith (2011) for enrichment to be successful it must be holistic and
must account for all aspects of a primate’s behavioral repertoire including physical, social,
dietary, cognitive and sensory well-being and must take into account their natural adaptations.
• Many people would assume that chimpanzees and other non-human primates need enrichment
only in daytime hours however, according to Videan et al. (2005) although chimpanzees may
rest between 8-12 hours each night, this is not a continuous, unencumbered slumber.
• With this in mind, we designed a study to not only observe if chimpanzee’s used enrichment
during the night, but also get a better understanding of the types of enrichment items they
preferred.
Methods
Participants
We studied two adult male chimpanzees (Dar and Loulis) and one female adult chimpanzee (Tatu)
socially housed at the Chimpanzee and Human Communication Institute (CHCI) located on the Central
Washington University campus in Ellensburg Washington. Tatu and Dar were cross-fostered by humans
and immersed in an American Sign Language environment. They were raised as if they were deaf human
children. (Gardner & Gardner, 1989). Loulis, was adopted by a chimpanzee named Washoe (the first
non-human primate to acquire a human language) and acquired his use of signs from Washoe and his
chimpanzee family. (Fouts, Fouts, & Schoenfeld, 1984; Fouts, Fouts, & Van Cantfort, 1989; Fouts, Hirsch,
& Fouts, 1982)
Data Collection Procedures
Night-vision cameras recorded the chimpanzees during the hours of 6:00pm-8:00pm and 6:00am8:00am. Each chimpanzee had access to various enrichment items including blankets, toys, containers,
tubes, clothes, and magazines. Table 1 shows the categories of enrichment that the chimpanzees
received during the night. From these video files, data collectors coded the chimpanzee’s use of
enrichment items using a focal animal time sampling technique for a 2-hour session. Sessions were from
18:00hr to 20:00hr and 06:00hr to 08:00hr Tuesdays, Wednesdays, and Thursdays from July-August
2012. Every 15 sec, the data collector recorded whether the focal chimpanzee contacted an item and
the category of the item.
Results
•
•
•
•
Data collectors recorded 57,715 observations. From those observations, 11,466 (20%) included
contact with an enrichment item.
The chimpanzees used blankets in 11,347 observations; this is 99% of all contact with
enrichment.
Due to the high use of blankets, this item category was not included in subsequent analyses.
Figure 1 shows the frequency that the chimpanzees contacted all categories of items except
blankets. The chimpanzees used food items with the next highest frequency (31%) after
blankets. This was followed by dress up other (24%) and then groom (14%).
Figures 2 shows each individual chimpanzees’ pattern of enrichment use again with blankets
eliminated (since blankets were the most used item for each chimpanzee). Dar used food items
most often while Tatu used Dress-up other most often. Overall this shows variation with
individual enrichment preference.
Discussion
• Consistent with previous data on captive chimpanzee sleep patterns (Videan, 2005), the 3 focal
chimpanzees in this study used enrichment items during the beginning and end period of night
time indicating they did not sleep continuously through the night; indicating that enrichment
provided during the evening is as important as enrichment provided during the day
• Blankets were by far, the most used enrichment item. However, when we take into
consideration the importance of nest building in free-living apes, it is not surprising that
blankets were used so often. Free-living chimpanzees, in particular pay very close attention to
size, location and construction of nests (Koops, 2012). Given the inherent limitations of captivity,
blankets are one of the few items that can be used to build a proper nest.
• Though not all enrichment items were used at the same frequency, providing a variety of
different enrichment items may contribute to the overall psychological well-being of captive
apes. Previous research suggests that providing an environment rich in choices, can reduce
stress, as well as, stereotypic behaviors, which are so often seen in captive animals (Lutz &
Novak, 2005).
Conclusion
Nighttime is a critical time to offer enrichment to chimpanzees as this study shows they use these
items and they have patterns of waking and sleeping during the night (Videan, et al., 2005). The 3
captive chimpanzees in this study preferred blankets over every other enrichment item offered.
However, they used other items as well. They displayed individual preferences for those other items.
Furthermore, offering captive apes a variety of enrichment items, during evening hours, increases the
choices they have in their environment and may contribute to their overall psychological well-being.
References
• Association of Zoos and Aquariums. (2009). Enrichment. Retrieved March 25, 2013, from Animal
Care and Management: Enrichment: http://www.aza.org/enrichment/
• Buchanan-Smith, H. M. (2010). Environmental enrichment for primates in laboratories.
Advances in Science and Research , 5, 41-56.
• Fouts, R. S., Fouts, D. H., & Schoenfeld, D. (1984). Sign language conversational interactions
between chimpanzees. Sign Language Studies , 42, 1-12.
• Fouts, R. S., Hirsch, A., & Fouts, D. H. (1982). Cultural transmission of a human language in a
chimpanzee mother/infant relationship. In H. E. Fitzgerald, J. A. Mullins, & P. Gage (Eds.),
Psychobiological perspectives: Child nurturance series Vol. III (pp. 159-193). New York: Plenum
Press
•
•
•
•
•
•
Gardner, R. A., Gardner, B. T., & Van Cantfort, T. E. (1989). Teaching Sign Language to
Chimpanzees. New York: State University of New York.
Koops, K., McGrew, W. C., de Vries, H., & Matsuzawa, T. (2012). Nest building by chimpanzees
(Pan troglodytes verus) at Seringbara, Nimba Mountains: antipredation, thermoregulation, and
antivector hypotheses. International Journal of Primatology , 33, 356-380.
Lutz, C. K. (2005). Environmental enrichment for nonhuman primates: theory and application.
Institute for Laboratory Animal Research Journal , 46 (2), 178-191.
Mellen, J., & MacPhee, M. S. (2001). Philosophy of environmental enrichment: past, present,
and future. Zoo Biology , 20, 211-226.
Videan, E. N. (2006). Sleep in captive chimpanzees (Pan troglodytes): the effects of individual
and environmental factors on sleep duration and quality. Behavioral Brain Research , 169, 187192.
Videan, E. N., Fritze, J., Schwandt, M. L., Smith, H. F., & Howell, S. (2005). Controllability in
environmental enrichment for captive chimpanzees (Pan troglodytes). Journal of Applied Animal
Welfare Science , 8 (2), 117-130.
Tables & Figures
Table 1. Item categories and descriptions
Enrichment Enrichment descriptions
Categories
Blankets
Large blankets, towels, comforters, etc.
Towels
Full-sized bath towels
Containers Objects that can contain something (bowls, bags, purses, etc.)
Grooming
Personal hygiene items (hairbrushes, combs, toothbrushes, mirrors, etc.)
Tubing
Any type of tubing (hoses, drinking straws, etc.)
Dress-up
clothes
Clothing of any type
Dress-up
other
Accessories such as jewelry, shoes, scarves, etc.
Paper/visual
Drawing
materials
Magazines, laminates, books
Paper, crayons, pencils, chalk, etc.
Toys
Misc. toy items (dolls, plastic figures, balls, stuffed animals etc.)
Food/water
Food or liquids let from dinner service or water from spigots
Figure 1. Frequency of item category use except blankets for all chimpanzees
50
40
30
20
10
0
39.50%
23.53%
10.08%
0.84%
14.29%
5.88%3.36%
2.52%
Figure 2. Frequency of item category use except blankets for Dar, Tatu & Loulis
Dar
Containers
Dress-Up
Dress- Up Other
Food
Groom
Paper
Toys
Tubes
Loulis
Containers
Dress-Up
Dress-Up Other
Food
Groom
Paper
Toys
Tubes
Tatu
Containers
Dress-Up
Dress-Up Other
Food
Groom
Paper
Toys
Tubes
Chimpanzee Auditory Communication
by Lisa Wilding
Communication is the transfer of information and requires a sender and receiver. Animals can
transfer information within a species (intraspecific) or between species (interspecific). Chimpanzees can
communicate by body postures, facial expression, gestures, touching, and through sounds and calls.
Group harmony, safety, and reproductive success of chimpanzees depend on intraspecific
communication, both in close and distant audibles.
Auditory communication
Acoustic communication is closely adapted to environmental conditions and the function of the
signal. Low-frequency audibles are required in dense vegetation and other audibles must be able to
travel over long distances. Chimpanzee audibles are no exception.
Food abundance and distribution, the presence of estrous females (Goodall, 1986), and
predation pressure influence community size (Boesch, 1991). Chimpanzees exhibit a flexible, fissionfusion social system whereby smaller parties or subgroups of the community will splinter off during the
day (Goodall, 1986). Subgroups consist of foraging parties, nursery groups of females and offspring, all
male or mixed sex hunting parties, consortships of one male and one female, male patrols, and social
groups (Goodall, 1986; Pepper, Mitani, & Watts, 1999). This fission-fusion social strategy coupled with
the highly territorial behavior of chimpanzees creates the importance of distinct close and distant calls.
Dispersed subgroups commonly use auditory contact between other subgroups, emphasizing the
importance of communicating geographic position, age, sex, and identity. Individuals direct calls at
other individuals in the same party, community members in another subgroup, individuals of another
community, non-living environmental stimuli, and animals of another species.
The emotional state of a chimpanzee greatly influences vocalization (Goodall, 1986); however,
research has found that chimpanzees are able to control the use of audibles. Field studies indicate that
chimpanzee communication signals vary with the social context in which they occur (Crockford &
Boesch, 2003). Chimpanzee calls occur within a graded system, meaning that each discrete call type
links to another call allowing the transition from one vocalization type to another (Marler, 1976).
A description of auditory chimpanzee communication will concentrate on each known
vocalization, separated into close intraparty calls that take place between chimpanzees that are in the
same group and distant interparty calls that are made between groups that are separated. Non-vocal
sounds, suppression of audibles, and semanticity will also be discussed
Intraparty close calls
Intraparty calls take place between chimpanzees within the same subgroup or party. This group
may be a foraging party and intraparty close calls are a means for individuals who may be temporarily
out of sight of others due to thick foliage to maintain cohesion with the other group members. The
following chimpanzee intraparty close call fundamental frequency values range between 20-2000 Hz
(Crockford & Boesch, 2005). To make a comparison, human vocalization has a fundamental frequency
range of 75-300 Hz, including both male and female.
Pant-grunts are a series of submissive noisy grunts (100-200 Hz) joined together by voiced
inhaled elements (Crockford & Boesch, 2005; Goodall, 1986). Captive chimpanzees have been able to
recognize individuals by pant-grunt vocalizations alone (Kojima, Izumi, & Ceugniet, 2003). A subordinate
when approaching or approached by a higher-ranking individual gives pant-grunt calls. Pant-grunts
maintain friendly relations between members of the community. Greetings between friendly individuals
will result in a soft pant-grunt; however, if the subordinate is apprehensive, the pant-grunt is louder
matching the level of apprehension. Pant-grunts, in this instance, often grade into pant-barks, which are
much louder (Goodall, 1986).
The hoo is a distinctive part of a whimpering sequence, occurring at 200-700 Hz (Crockford &
Boesch, 2005; Goodall, 1986). Produced by both infant and mother when physical contact needs to reestablished, the chimpanzee repeats the hoo several times. An adult will also give a hoo audible, often
with pouted lips, when begging for food or grooming. If this vocalization occurs in rapid succession,
rising and falling in pitch, it grades into a whimper (Goodall, 1986).
The whimper, most commonly heard in infants, reflects distress and need; however,
whimpering can also be heard in subordinate, older individuals when refused food by a higher-ranking
individual (Goodall, 1986). Produced at 250-1300 Hz frequency, whimpers can grade into screams by
infants and juveniles during weaning or separation from the mother (Crockford & Boesch, 2005;
Goodall, 1986).
In response to threats made by a higher-ranking individual, subordinates will produce a short,
shrill squeak occurring two to five times in succession at 800-2000 Hz (Crockford & Boesch, 2005;
Goodall, 1986). As fear increases, squeaks can grade into screams, which again grade back to squeaks
when the subordinate eventually becomes less agitated (Goodall, 1986).
High-pitched, loud screams, emitted most often in a series (800-2000 Hz), occur when an
individual is highly stressed, fearful, frustrated, or excited (Crockford & Boesch, 2005; Goodall, 1986).
Due to the frequency of this audible, screams travel at a distance and may serve to bring help from
other members of the community to an individual in trouble. Captive chimpanzees have been able to
identify individuals by hearing their scream vocalization (Kojima et al., 2003). Intraparty screams occur
in three subtypes: victim scream, tantrum scream, and copulation scream. The victim scream,
produced when the caller is attacked, is harsh and prolonged and is accompanied by the sounds of the
actual beating (i.e., hitting and stamping sounds). An infant rejected during weaning or an adult
indecisive if he/she should retaliate after an attack, emits a tantrum scream. Females emit a copulation
scream during mating, which consists of a clear, high-pitched sound of variable length (Goodall, 1986).
Barks, usually given in long sequences, are loud and sharp, varying in pitch. Females tend to
bark more than males. Waa-barks occur during agonistic encounters or witnessing an agonistic
encounter, accompanied by an arm-raise threat or arm waving, bipedal running, etc. After an attack,
the victim's screams will change to waa-barks, if he receives support from allies. A soft bark or coughthreat is a grunt made with a slightly open mouth by a higher-ranked individual to a lower-ranked
individual, serving as a mild warning to not approach or to prevent an unwanted action (Goodall, 1986).
Chimpanzee laughter or play panting is a soft, repetitive, breathy, guttural sound of low
intensity panting noises produced through repetitive sequences of air being drawn into the lungs and
then exhaled (Ruch & Ekman, 2001). Laughing occurs more often in infants and juveniles and results
most frequently during tickling encounters, but also in other physical contact play, such as wrestling or
play biting (Vettin & Todt, 2005). Chimpanzee laughter travels over a distance of more than 10 m and
does not differ from human laughter fundamental frequency when only considering the exhalation.
Vettin and Todt (2005) found that chimpanzee laughter has crucial acoustic features of human laughter
and is similar in occurrence and acoustic parameters with human laughter during tickling, supporting the
view that human laughter evolved from a play signal in nonhuman primates.
Although similar to chimpanzee laughter, panting consists of rapid, shallow breathing, and
occurs during a greeting, grooming session by one or both partners, or feeding excitement. Typically, an
open mouth presses against the body or face of the partner. Copulation pants can be mistaken for
laughing; however, a sound spectrograph analysis reveals that not only are copulation pants more rapid,
but it lacks the voiced inhalation phase of laughter (Goodall, 1986).
Family members use soft grunts among friendly individuals when traveling or foraging together
as a means of regulating movement and keeping cohesion. The extended grunt occurs during rest
sessions and consists of a long, drawn-out sound composed of two syllables. Another grunt composed
of two syllables is the nest grunt, which is made when an individual is looking for a suitable nest area, is
making a nest, or is settling down for the night. Soft food grunts draw the attention of party members
to a food resource and accompany the first minutes of feeding on a highly desired food item (Goodall,
1986). Slocombe, Kaller, Turman, Townsend, Papworth, Squibbs, & Zuberbuhler (2010) report that
males were significantly more likely to produce food-associated calls if a close ally was near, regardless
of the size of the group or the presence of any estrus females. Since calling is likely to increase
competition, the benefit of strengthening relationships with important social partners must outweigh
the costs. Calling occurred more in the largest feeding patches, indicating that chimpanzees assess the
costs and benefits of their calling behavior, producing food calls for the benefit of reinforcing social
bonds as long as the food source was plentiful.
Captive chimpanzees produce a bronx cheer (raspberry) vocalization, not reported in any wild
chimpanzee group, used as a means of manipulating the attentional state of a human caregiver
(Marshall, Wrangham, & Arcadi, 1999). They found that bronx cheer incorporated with pant-hoots, a
novel variant, were introduced by one male and subsequently spread to at least five other individuals,
suggesting that vocal learning may play a role in the acquisition of chimpanzee vocalizations.
Made in a situation of surprise, slight anxiety, or puzzlement, chimpanzees do not direct the huu
vocalization toward other individuals. Small snakes and unknown sources of sounds can invoke the huu
vocalization, even when the chimpanzee is alone. Sounding much like the hoo vocalization, the huu
does not have the characteristic pouting lips (Goodall, 1986).
Lip smacking and tooth clacking are not vocalizations, but sounds made by the tongue, teeth,
and mouth and frequently accompany social grooming sessions. Yawning when accompanied by a loud,
breathy exhalation is more indicative of tense individuals versus the tiredness of an individual. Coughs,
sneezes, hiccoughs, and loud lip smacking during feeding may function to locate party members
(Goodall, 1986).
Interparty distance calls
In fission-fusion societies, subgroups make distance calls between other groups, separated
oftentimes at great distances. Distance calls serve to draw attention to the location of food resources or
danger, announce the specific location of individuals, keep members within vocal contact, and indicate
when group members are in need of help from other groups (Goodall, 1986).
Pant-hoots, the most studied call, are adult calls that distinguish individuals by sex, age-class,
and individual identify (Marler & Hobbett, 1975). Kojima et al. (2003) found that a captive chimpanzee
was able to identify the vocalizations of pant-hoots, pant-grunts, and screams in community members.
Pant-hoots are comprised of four phases: introduction, build-up, climax, and let-down. The call begins
with a brief introduction consisting of a series of unmodulated elements. A progressively louder buildup follows, containing elements that are shorter and produced at inhalation and exhalation. The climax,
uttered only by males, is one or a series of long, frequency-modulated elements resembling a scream.
The conclusion is the let-down, which is similar acoustically to the build-up. The climax is the most
stereotyped part of the pant-hoot sequence (Marler & Hobbett, 1975). Higher-ranking males have
shorter pant-hooting sequences. Produced with vocalization on both exhalation and inhalation, panthoots occur in a number of different contexts. Chimpanzees pant-hoot most often in the morning and
overall pant-hoots increase with a rise in the numbers of males per party, and high-ranking males call
more often than low-ranking males (Wilson, Hauser, & Wrangham, 2007). Pant-hoots occur when
arriving at a new food source, when two parties meet, during travel, after returning from patrolling the
territorial boundaries, during social excitement, spontaneously during feeding, and especially at night
during nesting. Chimpanzees exchange pant-hoots with other individuals sleeping within earshot.
Ecological factors related to differences in habitat acoustics may account for geographic variations.
Researchers have identified four distinctive pant-hoots (Goodall, 1986).
The inquiring pant-hoot, which often accompanies tree drumming, occurs by an individual,
usually male, on a high ridge or at intervals during travel. It occurs in a series, rising in pitch toward the
end. There is a pause as the caller listens for a response, which can be a pant-hoot, waa-bark, or
scream. Individuals who have lost contact with other members may issue pant-hoots on 10-minute
intervals, waiting and listening for a reply (Goodall, 1986).
The arrival pant-hoot, which ends with deep roar-like sounds or high scream-like calls depending
on the individual, is typically given when coming across a good food source or joining another party
(Goodall, 1986). Clark and Wrangham (1993) looked at the let-down phase, which occurred most in the
first 5 minutes after arrival at food trees. They found that although the let-down pant-hoots were
associated with finding food, they also occurred during other periods of the feeding bout, indicating that
these pant-hoots conveyed information about something other than the arrival at a food source.
Furthermore, calling did not correlate with the amount of ripe fruit and did not influence the probability
of other parties arriving. High-ranking males emitted arrival pant-hoots at unoccupied trees suggesting
the these pant-hoots may provide information about status. Arrival pant-hoots announce the return of
adult males in camp, which also proclaim the identity of the caller. It allows chimpanzees located
elsewhere to have knowledge of who is there (Goodall, 1986).
Roar pant-hoots, most commonly given by highly aroused males, are continuous and lowpitched in nature. After a male has encountered a stranger or during intense social excitement within
the community, he emits roar pant-hoots, always accompanied by charging displays (Goodall, 1986).
The spontaneous pant-hoot, typically high pitched, is given by individuals feeding or resting and
does not necessarily require a response, although it is likely to elicit a chorus response from other
members. Adult or late-adolescent males are usually the ones that initiate spontaneous pant-hoots.
Nearby females usually only respond to this type of pant-hoot (Goodall, 1986).
Chimpanzees vocalize screams in both close and distant calls at a frequency of 800-2000 Hz
(Crockford & Boesch, 2005). The SOS scream is a clear, drawn out high-pitched call, which repeats
many times. Chimpanzees, recently attacked or severely threatened, will make this vocalization in an
attempt to get aid from an absent ally. Infants and juveniles cry in distress in a combination of loud
whimpering and tantrum screaming. Crying becomes louder and more frenzied matching the level of
distress especially in situations when the infant separates from his mother. Alarm calls, consisting of a
long drawn-out wraa occur when a chimpanzee encounters a potential dangerous animal or abnormal
behavior in a community member. Wraa serves as a distant call, alerting other members of danger,
and also to intimidate the dangerous intruder (Goodall, 1986).
When approaching a desirable food source or feeding, large parties of chimpanzees emit panthoots, barks, grunts, and a loud, high-pitched sound called the loud aaa at a frequency of 500-700 Hz
(Crockford & Boesch, 2005; Goodall, 1986). The loud aaa occurs only in the context of feeding and
most commonly by males. Food calls implies an individual or party has come across a rich food source.
A male may attract other individuals with whom he can interact socially with to benefit himself, such as
females in estrus, male grooming, etc. After a kill, screaming and waa-barks accompany food calls, and
quickly attract other chimpanzees to take part in sharing the meat (Goodall, 1986).
Rival males from different communities will exchange loud pant-hoots, roar pant-hoots, waabarks, barks, and screams. Their vocalizations have an intensity matching the heightened excitement
and apprehension. Intercommunity calls can continue for more than an hour until one or both sides
retreat (Goodall, 1986).
Non-vocal sound signals
In rainforests, visual contact is strictly limited, increasing the importance of vocalizations or
sound audibles. Chimpanzee buttress drumming is analogous to gorilla chest-beating and shows similar
spectrogram patterns. Males, primarily, will use a low-frequency drumming audible heard up to 1 km,
which entails pounding with hands and feet against the buttress of a large, resonant tree accompanied
by pant-hoots. Chimpanzees may stand on the ground and hit both sides, strike a single side in passing,
or sit on top of the tree's length. One to thirty rapidly delivered beats occur during drumming with 2-13
beats per minute at frequencies of less than 20 Hz. Chimpanzees will use this when traveling in large
mixed-sex parties. Pant-hoots are omitted when passing through dangerous areas, such as when
community ranges overlap. Given the distinct acoustic cues, chimpanzees may be able to recognize
unseen males by their drumming performance alone due to differences in mean beats per bout, mean
bout duration, and mean duration of interbeat intervals (Arcadi, Robert, & Boesch, 1998).
During courtship displays, a male will shake a small branch, audible only to a nearby female. By
scratching the arm or side of the body loudly, signals a partner to groom or informs an infant to cling to
his mother. Loud scratching can also serve to inform others of frustration or uneasiness (Goodall, 1986).
Suppression of sound signals
Typically, chimpanzees remain silent during patrols and consortships. Silence is also used during
some hunts and when startled by an alarming object (Goodall, 1986).
Call combinations
By combining different call types, chimpanzees have the potential to increase the complexity of
information transmitted to receivers. Chimpanzees produce both singular calls and call combinations
and use screams, pant-hoots, drumming, and whimpers more often in combination calls. Of the 16 call
types, laughter was the only vocalization not used in a combination. Pant-hoots accompany other long
distance calls, but rarely combine with a short distance call. With the use of call combinations, signalers
can transmit more precise information (Crockford & Boesch, 2005).
Semanticity
Traditionally, primate vocalizations have been associated as by-products of emotional states
primarily controlled by the limbic system. Are vocalizations produced to provide environmental and
social information to others or are they simply a reflected internal state of arousal of the caller?
Captive chimpanzees produced vocalizations as their first communicative behavior to gain the attention
of human caregivers (Hostetter, Cantero, & Hopkins, 2001). This study demonstrates that chimpanzees
have some voluntary control over vocalizations and use them in a functionally meaningful way.
Randolph and Brooks (1967) demonstrated that chimpanzees could be conditionally trained for vocal
behavior.
Slocombe and Zuberbuhler (2005) analyzed scream acoustic structures of both aggressor and
victim during agonistic conflicts. They looked at bout length, duration, frequency modulation, peak
frequency, relative transition, and absolute transition onset and offset temporal parameters. Six of the
10 parameters were significantly different depending on the social role suggesting that screams
function as referential signals. By using agonistic scream playback stimuli of congruent and
incongruent dominance scenarios, Slocombe, Kaller, Call, and Zuberbuhler (2010) found that
chimpanzees showed more orientation responses to incongruent or unexpected scream sequences.
This suggests that chimpanzees are extracting information about unseen social interactions based on
dominance status.
Slocombe and Zuberbuhler (2005) used food rough grunt playback stimuli that mimicked the
discovery of food by another group member and observed captive chimpanzee responses. Formants, a
concentration of acoustic energy around a particular frequency, appear in spectrograms as dark bands.
The darker a formant, the more audible it is. Rough grunts emitted when given apples were of a low
fundamental frequency, a high level of non-periodic sound, a low first-formant frequency, and a high
second- and third-formant frequency. Upon the discovery of bread, a higher valued food, rough grunts
were of a high fundamental frequency, a low level of non-periodic sound, a high first-formant
frequency, and low second- and third-formant frequency. Call duration was not changed. Apples and
bread were each placed in tubes under specific trees associated with each food item. The participant
adjusted foraging behavior, searching longer after hearing grunts given to bread compared to grunts
given to apples and searched under the tree associated with that particular food item. This study
demonstrates that a chimpanzee can extract specific information about food sources by listening to the
food grunt calls of other members. Slocombe and Zuberbuhler (2006) continued research into
functionally referential chimpanzee communication expanding the number of captive participants, as
well as including a group of free-living chimpanzees and using different levels of preference foods
instead of playback stimuli. Spectrograms indicated significant differences in duration and intercall
duration between calls given to foods of low and high preference. Furthermore, the acoustic structure
of captive chimpanzees varied subtly, but significantly, in first formant frequencies and call duration
between food types within the high-preference foods. There was no significant difference between
food types for the low- or medium-preference food items. Free-living chimpanzees emitted food
grunts similar to captive chimpanzees, but only the intercall duration differed significantly between the
grunts given to the food types. For captive chimpanzees, rough grunts become meaningful labels for
referring to specific food items.
References
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123-125.
SIGN LOGS – 8 PHOTOS
4/19/2013 Savannah Schulze
Loulis was sitting in the tunnel in the night enclosure looking toward the kitchen. We had prepared fruit
for breakfast and there were two bananas sitting on the counter. Loulis signed THAT BANANA THAT,
gesturing at the bananas.
4/18/2013 Bonnie Hendrickson
I sat with Tatu this afternoon and we looked through magazines together. As she looked through the
pages she would point at the pictures and sign. Tatu signed THAT CHEESE and THAT RICE. I showed her a
picture in my magazine of pudding and asked WHAT THAT? Tatu reached out her hand and I gave her
the magazine. I signed SWEET as she looked at the photo. Tatu signed SWEET, more to herself than to
me. She continued to look at my magazine. She signed THAT BLACK while pointing at black Easter eggs,
THAT PAINT while pointing at a photo of a boy covered in paint and holding a paintbrush, and THAT
CORN while looking at a photo with a plate full of vegetables.
3/5/2013 Meg Mas
Tatu and I were having quality time looking at magazines and I asked her WHO YOU? Tatu replied TATU.
I asked WHO THAT? pointing at a guy in an Old Spice advertisement. Tatu replied BOY. I asked WHO
ME? Tatu replied FRIEND. I signed THANK YOU FRIEND!
3/18/2013 Susie Keenan
I was wearing my bright blue jacket on berm this morning. My colorful plaid sweatshirt was peeking out.
Tatu watched as I buttoned and unbuttoned my jacket. When I stopped she looked up at me and signed
COLOR.
3/14/2013 Kaeley Sullins
Tatu and I had been playing baseball in the night enclosure area. I was the pitcher and Tatu was up to
bat. Tatu had two bats: one red and one black. Tatu had one foot on the red bat and the black one was
sitting on the bench in front of her. She signed THAT BLACK on the bat.
3/25/2013 Rozsika Steele
Lisa and I were serving lunch to Tatu and Loulis. We each had a smaller bowl so that we could eat some
soup with them. Tatu signed to Lisa GIMMIE THAT gesturing to Lisa’s little bowl of soup. The bowls were
too tall to pass under the enclosure to Tatu so Lisa told her that she was SORRY. Tatu signed THAT more
emphatically. Lisa verbally said “Tatu this one is mine”. Tatu quickly corrected her signing MINE while
looking at Lisa sternly. Lisa said “It’s the same as yours” and let Tatu try a spoonful of her soup. Once
Tatu was satisfied that Lisa did not have anything special she was content to eat soup from her own
bowl.
3/5/2013 Meg Mas
I was cleaning the EAST room and Loulis approached me. I asked WHAT WANT? Loulis replied DRINK. I
asked WHO DRINK? Loulis replied DRINK. I asked YOU DRINK? Loulis replied DRINK. I asked YOU WANT
DRINK? Loulis replied ME DRINK! I served Loulis a drink.
3/1/2013 Rozsika Steele
I was interacting with Tatu in the human cage. Tatu signed HUNGRY. I signed HUNGRY? WHAT WANT?
with a raised brow. Tatu answered NUT. I served Tatu nuts.
2/23/2013 Rozsika Steele
I asked Tatu WHAT WANT EAT? Tatu answered FRUIT. I asked WHICH FRUIT? Tatu answered FRUIT. I
asked NAME FRUIT WHAT? Tatu answered FRUIT! I signed SIGN NAME PLEASE. Tatu replied TATU! I
signed NOT YOUR NAME! WHAT FRUIT NAME?! Tatu answered BANANA.
2/19/2013 Kaeley Sullins
I walked into the night enclosure area to greet the chimpanzees this morning. I signed to Tatu GOOD
MORNING FRIEND. Tatu looked at me and signed KISS and put her lips up to the fencing. I offered her
my wrist and she gave me a kiss.
2/16/2013 Kaeley Sullins
Tatu and I were interacting in the West human cage. I asked Tatu WHO YOU? Tatu signed TATU. I asked
WHO ME? Tatu signed LAUGH.
3/6/2013 Meg Mas
This morning Tatu was very interested in one of the nighttime enrichment items: a little blue lizard toy.
She carried it around with its tail in her mouth. She sat down and put the lizard toy on the ground in
front of her. I asked WHAT THAT? Tatu signed THAT. I asked again, WHAT NAME THAT? Tatu signed
BUG. She then folded the bug-lizard in half and bit down on it. I signed THAT BUG HURT. Tatu put the
bug-lizard back down on the ground and pushed it to me.
INTERACTION LOGS
2/25/2013 Glee Larsen
I spent some time looking through a fashion magazine with Loulis today. It seemed like he was pretty
interested. He would sign HURRY THAT pointing at a page until I turned it to the next one.
4/1/2013 Amanda Carner
I came into the night enclosure area this morning to greet the chimpanzees. Loulis greeted me with a
kiss and then started to tickle my wrist. I started to breathy pant. Loulis head nodded and started to
laugh with me while he was tickling my wrist.
4/3/2013 Lisa Wilding
Loulis and I played a game with the window blinds in the classroom. I opened the drapes and blinds and
then let the blinds close slowly. He tapped on the glass where he wanted them to be and I opened them
to that spot. He had a huge playface! I call this the “blinds game”.
3/1/2013 Rozsika Steele
Today is inflatables day. Tatu threw a large beach ball at Loulis while he was eating his snack (a bag of
nuts). She was attempting to get him to play a game of chase. Loulis ignored her and walked into the
other room to finish eating his snack in peace.
3/2/2013 Kaeley Sullins
Tatu and I were interacting on berm. I said to Tatu “Can you sign bug?” Tatu didn’t signed bug, instead
she started to frantically look around her for the bug. I imagined her thinking “oh no! where’s the
bug?!”
From the Archives:
3/31/92 Wendy Shaw
(an example of how a chimpanzee who can sign teases a friend)
Washoe: GUM
Wendy: YOU FINISH EAT?
Washoe: EAT
Wendy: FOOD FINISH?
Washoe: GUM
Wendy: YOU FINISH EAT? (FINISH was emphasized)
Washoe: GUM
Wendy: YOU FINISH EAT? YOU SIGN FINISH?
Washoe: GUM
Wendy: YOU SIGN FINISH? I WANT SEE YOU SIGN FINISH
Washoe: LAUGH/SMILE
Wendy got gum for Washoe.
10/29/93 Michelle Haislip and Jennifer Beaucher
We were sitting on the floor facing Room 2. Washoe was sitting in Room 2 facing us. Interns were in the
East Room getting ready for a Halloween party.
MH: WASHOE HAPPY?
JB: HAPPY? WASHOE HAPPY?
W: HAPPY HUG (HAPPY was signed very emphatically with large movements)
JB: GOOD! WASHOE HAPPY!