«Activity Budgets of Two Captive White-Handed Gibbon (Hylobates lar) Populations Housed in Different Types of Environments by Sara Warren Faculty ...»
McNair ScholarS JourNal ▪ VoluMe 11
Activity Budgets of Two Captive
White-Handed Gibbon (Hylobates lar)
Populations Housed in Different Types of
by Sara Warren
Faculty Mentor: Dr. Elizabeth Strasser
Housing captive primates in environments representative of their wild habitat in many cases
can be challenging. Captive white-handed gibbons can be housed in a caged environment or
on an island surrounded by a moat. It has been hypothesized that the quality of the captive environment can affect gibbon behavior, as expressed in (or by) their activity budgets. The researcher observed the activity budgets of captive white-handed gibbons at two Northern California zoos. The captive primates’ activity budgets were compared against those of wild gibbons to gauge similarities or differences between captive and wild animals. Both captive populations’ activity budgets were similar, but varied from those of wild populations, as the captive animals have no need to travel for food.
Recreating any wild animal’s habitat in a zoo environment is always going to be a challenge (Hosey 2005). Zoo visitors will sometimes comment on how captive animal exhibits are small or cage-like. There are regulations on animal enclosures and health laid out by United States Department of Agriculture’s (USDA 2010) Animal and Plant Health Inspection Service (APHIS), though many zoos follow the guidelines of the Association of Zoos and Aquariums (AZA), which, according to its Web site, are more stringent about animal well-being. The “activity budgets” of animals, or the time an animal devotes to various activities, such as traveling, resting, eating, and socializing, are indicators of the quality of an enclosure.
Although it is important for all captive species to have high quality enclosures to live in, the impact of the relatively small enclosures on the activity budgets of two captive white-handed gibbons populations is the focus of this study.
The white-handed gibbon, Hylobates lar, is an ape of the family Hylobatidae (Rowe 1996). In the wild, these arboreal, or tree dwelling, primates are found in the deciduous and evergreen rainforests (Roonwal and Mohnot 1977;
Rowe 1996) of Northern Sumatra, in parts of Malaysia, Burma, and Thailand (Groves 2001). Within their natural environments, white-handed gibbons live 201 califorNia STaTe uNiVerSiTy, SacraMeNTo in small monogamous groups, consisting of an adult female-male pair and their offspring (Chivers 1972; Crandall 1964; Rowe 1996). In captive settings, white-handed gibbons are usually paired similarly (Geissmann 1995), though it has been noted that two adult female gibbons can cohabitate peaceably, although adult male gibbons are far too aggressive to be housed together in a captive setting (Crandall 1964; Geissman 1995).
Gibbons are classified in the same superfamily as humans and other apes and are the smallest of the living apes. The behavior of our fellow apes provides a window to understanding our evolutionary past. For example, it has been suggested by Geissmann (2000) that gibbon “dueting,” the songs adult gibbons engage in to strengthen their relationship and to secure their territory, could be linked to the human capability for music and singing. Because it is easier to study captive apes than those in the wild, it is imperative that we provide environments that support healthy activity budgets.
As of March 2010, there were approximately 478 white-handed gibbons in zoos worldwide, according to the Gibbon Network Web site. Given the large number of captive gibbons, it is important for zoo management and staff to know what kind of environment the animal originates from and, therefore, is adapted to. A diet similar to their wild diet should be provided for the captive animals, and the space in which they are kept should take into account their activity budgets and travel needs. Enrichment, such as the introduction of novel items, can also be provided to captive animals to stimulate their activity levels.
Newberry (1995, 229) defines “environmental enrichment” as “an improvement in the biological functioning of captive animals resulting from modifications to their environment.” Enrichment items can be novel foods, cardboard boxes, mirrors, browse (a straw-like substance), old clothing, stuffed toys, or virtually anything with which the primate can interact that is not commonplace in their captive habitat. Enrichment can also be provided to captive animals to stimulate their brains and encourage interaction with their environment (Vick et al. 2000).
The Sacramento Zoo in Sacramento, California, houses many animals including a fair number of primates. The exhibit for the chimpanzees is much more naturalistic than those for many of the other primates in that it has an earthen floor and a variety of flora. In addition, there is plenty of space for the chimps to move about. Before the 1980s, these same chimpanzees lived in a smaller cage-like enclosure (Sacramento Zoo 2010). The exhibit that houses the two white-handed gibbons is similar to the pre-1980’s chimp enclosure in that it is a medium-sized cage with a concrete slab on the ground and seven 4x4 metal bars located along the top to simulate a “canopy” for the gibbons to swing in. The chimpanzees appear to interact more with their larger, lush 202 McNair ScholarS JourNal ▪ VoluMe 11 environment than the gibbons do in their smaller cage-like environment, suggesting that the type of enclosure each primate is housed within might affect their activity budgets.
Located two hours south of Sacramento, California, the Oakland Zoo also boasts many primate species, two white-handed gibbons being among them. The captive environment for the gibbons at the Oakland Zoo is very different from that at Sacramento Zoo. The gibbons at the Oakland Zoo are situated on an island habitat with a moat around it, which they will not attempt to traverse because gibbons cannot swim (Carpenter 1941; Keeling and McClure 1972). The island has many towering trees, ropes, vegetation and no cages. The Oakland Zoo’s white-handed gibbons perform ricochetal brachiation (e.g., like a ball ricocheting in a closed court), and they appear to be very interactive with their naturalistic environment. The Oakland Zoo’s exhibit is a veritable forest, with no bars, cages, or glass employed to keep the animals from the public, while the captive gibbons at the Sacramento Zoo are housed in an exhibit with no trees and minimal foliage.
reSearch queSTioN Perhaps the size and scope of captive white-handed gibbon enclosures affects their activity budgets, as might be seen in a comparison of the activity budgets of the gibbons in two contrasting zoo environments. This research seeks to answer the question: Do both groups of gibbons show similar activity budgets regardless of their different captive environments? If it proves to be the case that the white-handed gibbons at the Sacramento Zoo are less active than those at the Oakland Zoo, more research can be conducted in order to provide a more expansive and foliage-rich environment for the Sacramento gibbons. This study takes into account the variation in the habitat provided for the captive white-handed gibbons at the two California zoos described previously, in order to discern if habitat size and offered environmental enrichment have an effect on the activity budgets of their inhabitants.
liTeraTure reView Much of the current literature on gibbons comes from research on wild populations, as more field studies have been conducted in the wild than in captivity. According to Melfi (2005, 102), “It would appear that most primatologists do not conduct research in zoos. The number of research projects undertaken on zoo-housed primates is surprisingly low,” hence, the need for research on captive primates such as the white-handed gibbons.
20 califorNia STaTe uNiVerSiTy, SacraMeNTo Wild vs. Captive Gibbon Diet The diet of most primates comprises solids as well as water. White-handed gibbons are frugivorous primates (Bartlett 2009; Carpenter 1940) with 50% to 75% of their diet consisting of fruit (Chivers 1972; Rowe 1996). According to Rowe (1996), the rest of their diet consists of leaves (29%), insects (1%), and flowers (7%).
Both the zoos in the present study provide their captive white-handed gibbons at different times throughout the day a variety of greens, fruits, vegetables and leaf-eater chow (“monkey biscuits”). A captive gibbon drinks in one of two ways: they either dip their hands into a water source to lick it off, or they put their lips to the source and suck up the water. While these methods were not thought to be common in wild gibbon populations (Carpenter 1941), recent evidence shows that some wild gibbons will dip their hands into river water for a drink (YouTube 2010).
Locomotion and Travel In the wild, white-handed gibbons travel mainly to find food resources (Bartlett 2009), which is not necessary in captivity as food is regularly provided. The ways in which a gibbon can travel are varied. The most widely used mode of travel is brachiation with bipedal walking coming in second (Carpenter 1941; Crandall 1964; Rowe 1996; Tuttle 1972). “Brachiation” employs the gibbon’s long arms to swing from branch to branch. With its shortened thumbs and strongly curved fingers, the gibbon’s long, hook-like hands allow brachiation to be skillfully executed (Groves 1972; Tuttle 1972).
Wild white-handed gibbons do not often come down from the safety of their arboreal habitat (Crandall 1964), but captive gibbons have been seen in many instances walking bipedally, either on the ground or on wide, sturdy branches (Crandall 1964; Napier and Napier 1967; Tuttle 1972). Though wild gibbons do travel bipedally, Carpenter (1941, 74) writes that, “brachiation predominates over walking” and that “in the forest where supports are mainly flexible branches, brachiation is used approximately nine times as frequently as walking.” Like a tight-rope walker, gibbons use their hands and arms to keep balance while walking bipedally (Carpenter 1941); they also possess welldeveloped thigh muscles (Groves 1972) that assist in any bipedal travel.
Wild Gibbon Activity Budgets A large portion of a wild gibbon’s day is taken up with eating and traveling to feeding trees (Bartlett 2009; Carpenter 1941). Gibbons are “diurnal primates,” in that they are active during the day time (Carpenter 1941; Crandall 1964), and have been observed waking at 5:30 a.m. in Doi Dao, Thailand (Carpenter 1941). After traveling from tree to tree and feeding for a large portion of the day, the wild gibbons of Doi Dao would move to a sleeping tree 204 McNair ScholarS JourNal ▪ VoluMe 11 where they were asleep by sundown, resting anywhere from 10 to 11 hours (Carpenter 1941). Bartlett (2009) most recently published research on wild gibbon activity budgets in Khao Yai, Thailand. Table 1 shows the average frequencies of the activities engaged in by the Khao Yai gibbon study groups (Bartlett 2009), where it is apparent that feeding occupies much of these gibbons’ time, with resting and traveling as close seconds. While vocalizing is considered by many to be a form of social activity, Bartlett (2009) recorded it as a separate activity (Table 1).
Type of activity % time engaged per day Feeding 32.6 Resting 26.6 Traveling 24.2 Social activity 11.3 Vocalizing 4 Table 1. Activity budgets of white-handed gibbons in Khao Yai, Thailand (Bartlett 2009) The most important form of social interaction among gibbons is grooming (Bartlett 2009). For his research in Khao Yai, Bartlett divided the social interactions of gibbons into sub-classes, two of which are groom and play (Table 2). Most of the grooming was performed by adult members of the group (Bartlett 2009).
Type of social activity % time engaged per day Groom 6.2 Play 4.1 Table 2. Two types of social activity Play behavior occurs in both wild and captive gibbon populations, though it is restricted mainly to juveniles (Bartlett 2009; Carpenter 1941; Chivers 1972).
Chivers (1972, 12) described the playful behaviors of juvenile gibbons as, “modifying their locomotion and…elaborations of usual postures.” Bartlett (2009, 50) employs the colorful language of “chasing, wrestling, slapping and biting” to describe the behavior of playful gibbons. Play behavior decreases in juvenile gibbons as they approach sexual maturity (Carpenter 1941).
Captive Gibbon Activity Budgets There has not been much of a record on captive white-handed gibbon activity budgets, aside from the work of Ng (2004). The research done by Ng focused on the activity budgets of captive gibbons in a Thailand sanctuary before and after implementing an environmental enrichment program. Ng (2004) found that the gibbons were resting 70% of the day prior to the introduction of an enrichment program. After enrichment was provided, Ng
205califorNia STaTe uNiVerSiTy, SacraMeNTo
reports an increase in “species-typical” activity, in that the gibbon’s activity budgets were closer to those seen in wild populations.
Captive Environment There are two main types of captive gibbon environments: island and caged.
Whether captive or wild, gibbons do not like to be in water and cannot swim (Carpenter 1941; Napier and Napier 1967). Carpenter’s research (1941) demonstrated the gibbon’s lack of swimming capabilities when he placed a female gibbon into a pool of water, and after some time of her failing to stay afloat, he retrieved her. With their aversion to water, gibbons will stay within a designated enclosure surrounded by a moat (Crandall 1964). Based on a survey of gibbon exhibits at zoos in China and Vietnam, Geissmann (1995, 6) wrote that, “Island settings with natural vegetation are not only extremely attractive to visitors but also come closer to imitating a naturalistic environment than most indoor enclosures.” The only problem that could occur in an island habitat would be if a gibbon were to accidentally fall into the water it would definitely drown, without human assistance (Crandall 1964).