Tests for sex differences in fitness-linked traits in the spiderAgelenopsis aperta (Araneae: Agelenidae)

The idea that traits linked to individual fitness may differ between males and females was tested in the desert funnel-web spider,Agelenopsis aperta. The study entailed comparison of juvenile male and female behavior with respect to three traits previously shown to be linked to female body mass and ultimately to individual female fitness: habitat discrimination, territorial behavior, and agonistic behavior. As juveniles, male and female spiders behave similarly: they utilize the same habitat cues in locating web sites, maintain similar territory sizes, and exhibit the same behavior patterns in territorial disputes. Like females, males that obtain the highest-quality web sites achieve a greater body mass and are more likely to survive to maturity.     

Coexistence of monogamy and polygyny in black-crested gibbon (Hylobates concolor)

All gibbons are monogamous and territorial with the exception ofHylobates concolor. This paper reports the coexistence of monogamy and polygyny in black-crested gibbons. Based on the fact of two adult females and two offspring of the same age category in one group and other reasons, we suppose that the two adult females have bred in a single group, i.e. a polygynous one. The other main reasons are: (1) a large home range makes it possible for more individuals to live in one group; (2) mutual tolerance among two females; and (3) selection pressure favouring polygyny.     

Intragroup and Intergroup Social Interactions in White-Handed Gibbons

One of the least studied aspects of the Hylobatidae is their social behavior. In the past, researchers have attributed this to a general lack of affiliative social interactions due to small group size and the hostile nature of intergroup encounters. Data collected on white-handed gibbons (Hylobates lar) in Khao Yai National Park, Thailand, indicate that gibbons engage in higher rates of social behavior than had previously been appreciated. In addition to relatively high rates of intragroup social contact, gibbons engaged in social behavior, including play and grooming, with members of neighboring groups. These findings obligate a renewed consideration of the nature and function of territoriality in primates.     

Interspecific spacing between gibbons (Hylobates klossii) and langurs (Presbytis potenziani) on Siberut Island,Indonesia

Spatial arrangement and social interactions of two sympatric and ecologically similar primate species, Hylobates klossii and Presbytis potenzianai, are described from field observations made between July 1972 and October 1974 on Siberut Island, Indonesia. Gibbon territories and langur home ranges overlap extensively. Because gibbons have the ability to supplant langurs at shared food sources, langurs are at a competitive disadvantage. To avoid or decrease the frequency of hostile interactions with gibbons, langurs locate their core areas on boundaries between adjacent gibbon territories, which permits langurs to retreat across these barriers in response to gibbon movements. Langurs further enhance segregration by leaving their sleeping trees earlier than gibbons, gaining additional feeding time on contested food sources. This form of interspecific spatial organization between gibbons and langurs resembles certain predator-prey spacing systems, where territorial boundaries between adjacent predators serve as sanctuaries for prey populations.     

Diurnal and seasonal changes in the mate-locating behavior of the satyrine butterfly <Emphasis Type="Italic">Lethe diana</Emphasis>

The time schedule of mate-locating behavior in the male satyrine butterfly Lethe diana was studied. Males displayed territorial behavior only in the afternoon, but it was not known whether they attempted to locate mates in the morning. In order for males of most butterfly species to mate with a virgin female, it would be most effective to initiate mate-locating behavior in the morning, when synchronous eclosions occur. Males of L.diana flew patrols in the morning and displayed territorial behavior in the afternoon. The cost of territorial behavior is probably less than that of patrolling, as territorial flights are shorter than those when patrolling. The temporal switching of mate-locating behavior is theoretically favored, since the reproductive value of females decreases later in the day, when males perform the less costly mate-locating behavior. Thus, the diurnal switching of male mate-locating behavior may be an adaptive strategy in response to the rapid decline in the reproductive value of females over the course of a day.     

Comparisons of Suspensory Behaviors Among <Emphasis Type="Italic">Pygathrix cinerea</Emphasis>, <Emphasis Type="Italic">P. nemaeus</Emphasis>, and <Emphasis Type="Italic">Nomascus leucogenys</Emphasis> in Cuc Phuong National Park,Vietnam

In our study at the Endangered Primate Rescue Center of Cuc Phuong National Park, Vietnam, we aimed first to assemble a positional behavioral profile of captive gray-shanked (Pygathrix cinerea) and red-shanked (P. nemaeus) doucs that relates to the use of forelimb suspensory postures and arm-swinging locomotion. The profile is of interest because researchers have documented that red-shanked doucs more frequently use suspensory postures and locomotions than other colobines do. We confirmed that red-shanked doucs commonly use suspensory positional behaviors and also that gray-shanked doucs use suspensory behaviors at similar or even higher frequencies than those of red-shanked doucs. Our second goal was to assemble a preliminary kinematic profile of suspensory locomotion in Pygathrix within the context of the arm-swinging locomotion exhibited by northern white-cheeked gibbons, Nomascus leucogenys. Mean forelimb angles at initial contact and release of arm-swinging behaviors were remarkably consistent among gibbons and doucs despite the fact that gibbons typically used more continuous brachiation. Doucs also exhibit a greater range of forelimb angles than gibbons do. In addition, trunk orientation tends to be less vertical at initial contact for doucs than for gibbons, perhaps owing to the frequent use of quadrupedal sequences directly before or after forelimb suspension. Our behavioral and kinematic analyses add to the emerging realization that Pygathrix is capable of, and frequently expresses, a range of suspensory positional behaviors, including brachiation.     

Seasonal changes in territorial behaviour of hazel grouse ( Bonasa bonasia) in a temperate forest of South Korea

We studied the seasonal changes in territorial behaviour of hazel grouse (Bonasa bonasia) from December 1999 to July 2001 in a temperate forest of South Korea. The study was based on the use of radio telemetry. Territory size and degree of overlap increased after the breeding period, and index of advertisement and border disputes decreased. In spring, the territory was defended by both males and females. During autumn and winter, this behaviour was relaxed to such a degree that hazel grouse cannot be considered territorial, but as forming a home range.     

The yellow-cheeked gibbon (Hylobates gabriellae) in nam bai cat tien (southern vietnam) revisited

Data concerning the status, habitat, and vocalizations of yellow-cheeked crested gibbons (Hylobates gabriellae) were collected during a short field trip to the Nam Bai Cat Tien National Park (southern Vietnam). Nam Bai Cat Tien may be the southernmost locality where crested gibbons (i.e. theHylobates concolor group) still survive. Fewer songs were heard at Nam Bai Cat Tien National Park than at other crested gibbon sites visited by the author. At least two gibbon groups appear to have been greatly reduced in number since previous surveys in the park. There is some evidence that both the gibbon population and the gibbon habitat in Nam Bai Cat Tien are disturbed. The first case of a great call solo song in wild gibbons of theconcolor group is reported. Great calls ofH. gabriellae are described and documented with sonagrams for the first time. They differ from those previously described forH. leucogenys.     

Predation on giant flying squirrels (Petaurista philippensis) by black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China

Predation on vertebrates is infrequent in gibbons. In a 14-month field study of the central Yunnan black crested gibbon (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China, we observed gibbons attacking, killing and eating giant flying squirrels (Petaurista philippensis). During 845 h of observation on one study group, the gibbons attacked giant flying squirrels 11 times, and succeeded in 4 cases. Although all members of the group attempted to attack the squirrels, all four successful attacks were made by the same adult female. The victims were infants in three cases and a juvenile or sub-adult in one case. Black crested gibbons also attacked adult giant flying squirrels by grabbing their long tails and throwing them from the canopy, but they failed to catch or kill the prey in three cases observed. Passive meat sharing occurred in three out of four successful cases. Besides hunting giant flying squirrels, the black crested gibbons also ate eggs or chicks in two birds’ nests and one lizard.     

Biology and behaviour of reintroduced gibbons

We observed and recorded the behaviours of gibbons undergoing rehabilitation, before and after release, to document the behavioural and social changes of gibbons in the rehabilitation program and develop criteria for determining the suitability of a pair of gibbons for release. Hylobates albibarbis were observed at the Kalaweit Gibbon Rehabilitation Project in Kalimantan, Indonesia. Data were collected on animals both pre- and post-release and on wild gibbons for comparison. Data presented here show that reintroduced gibbons are capable of surviving without human intervention. In addition, their behaviour is similar to that of wild gibbons in terms of activity budgets, position in the canopy, body posture, pair association (PA) and diet. Prior to this study, no attempt has been made to quantify the rehabilitation process for gibbons, and rehabilitation project personnel require data reporting all aspects of a release so that improvements can be made. It is important to report these data for the benefit of future releases. Criteria, based on the behaviour of wild gibbons, are proposed to assist rehabilitation centers in assessing the suitability of gibbon pairs for release.     

Gibbon foraging decisions and the marginal value model

We use data from an observational field study of frugivory in two sympatric gibbons, lar (Hylobates lar) and siamang (H. syndactylus), to test assumptions and predictions of the marginal value model (MVM). A key prediction of the MVM is that marginal gain rates at the time of leaving the patch are equal across patch types. We found that this is not the case for gibbons: rates of energy intake at the end of feeding sessions were significantly different for different types of fruit, and we could not attribute this to temporal variation in fruit availability. Initial and final caloric intake rates were highly correlated. This suggests that gibbons do not adjust the time spent in patches in order to maximize the average rate of energy intake. Similar results were obtained for all other currencies considered. Gibbon foraging appears to satisfy several, but not all, assumptions of the MVM. As required by the model, fruit patches occur as discrete units, patches are encountered sequentially, travel time between patches exceeds search time between items within a patch, search for and search within patches are incompatible activities, and intake rates decline over time spent in a patch. However, the declining rates we detected may be an effect of satiation instead of patch depletion, patches probably are not encountered at random, and group members may not forage independently. Thus, our results suggest that the MVM is not an adequate model of gibbon foraging behavior, but they do not invalidate the MVM per se.     

Preliminary observations of wild black-crested gibbons (Hylobates concolor concolor) in Yunnan province,people's republic of China

Black-crested gibbons (Hylobates concolor concolor), which inhabit the subtropical forests of southern China and northern Vietnam, have until now never been the subject of any systematic behavioral or ecological field study. This report presents the findings of a three-month field study of wild black-crested gibbons in the Wuliang and Ailao Mountain Game Reserves in Yunnan Province, People's Republic of China. The sites visited consisted of temperate, subtropical, broadleaf evergreen forests, with trees belonging to the families Elaeocarpaceae, Fagaceae, Lauraceae, Magnoliaceae, and Theaceae. Black-crested gibbons were documented from four sites visited and were found to be polygynous, with an average group size of seven to eight animals. The family groups were observed to comprise one adult male, from one to four adult females, and numerous offspring of various ages. Both sexes of this species emit interactive songs, and various features of this loud vocal behavior were analyzed and are discussed here. Since all other gibbon species were found to inhabit only tropical rain forests and live in strictly monogamous family groups, some of the ecological and evolutionary implications of these findings are also presented.     

Song Functions in Nonduetting Gibbons: Evidence from Playback Experiments on Javan Gibbons (<Emphasis Type="Italic">Hylobates moloch</Emphasis>)

Territorial, pair-living primates usually perform long-distance calls as duets in which adult males and females coordinate their calls. Previous studies using playback experiments have shown that gibbon duets convey information about the status of the caller (location, familiarity, sex of the caller, and paired status) and gibbons use this information to respond to achieve several nonmutually exclusive functions, including intragroup contact, territorial defense, and pair-bond advertisement and strengthening. However, not all pair-living gibbons duet, and it is unclear whether the same results should be expected in nonduetting species. We conducted song playback experiments (N = 47 trials) to test hypotheses about song functions in nonduetting gibbons on two groups of wild Javan gibbons (Hylobates moloch) in the Gunung Halimun-Salak National Park, Indonesia. Javan gibbons initiated movement toward the speaker more quickly in response to songs broadcast in the center of the territory, stranger songs, and songs of unpaired individuals than to songs at the border, neighbor songs, and songs from paired individuals. These results suggest that Javan gibbons can localize songs, and that Javan gibbon songs transmit information about the identity and paired status of the caller. Our results imply that Javan gibbon solo songs are likely to function for territorial defense and pair-bond advertisement like duets in other primates.     

Non‐territorial Macaques Can Range Like Territorial Gibbons When Partially Provisioned With Food

Human food supplementation can affect components of animal socioecology by altering the abundance and distribution of available food. We studied the effect of food supplementation by comparing the ranging patterns and intergroup interactions of two groups of northern pigtailed macaques (Macaca leonina), a non‐territorial primate species. One group was partially reliant on food provisioning, whereas the other group foraged wild food. We also compared the macaques’ movement with that of a group of white‐handed gibbons (Hylobates lar), a territorial species inhabiting the same site. Home range, core area, and daily path lengths were significantly smaller for the semi‐provisioned group than for the wild‐feeding group. In contrast to wild‐feeding macaques, supplemented macaques showed higher fidelity to home range, core area, and particularly to the region where human food was most accessible and abundant. The relationship of daily path length and home range indicated a low defendability index for wild‐feeding macaques; the higher index for the semi‐provisioned group was consistent with the territorial pattern found in gibbons. Semi‐provisioned macaques showed further traits of territoriality with aggression during intergroup encounters. These findings indicate that human modification of food availability can significantly affect movement patterns and intergroup competition in macaques. The observed ranging dynamics related to food provisioning may decrease the efficiency of macaques as seed dispersers and increase predation on their home range, and thus have important consequences for plant regeneration and animal diversity.     

Are <Emphasis Type="Italic">Hylobates lar</Emphasis> Extirpated from China?

The Nangunhe Nature Reserve in Southwest Yunnan (PRC) has long been presumed to be the last stronghold of lar (or white-handed) gibbons (Hylobates lar) in China and the likely last place of occurrence of Hylobates lar yunnanensis. We conducted a comprehensive survey to assess the status of lar gibbons at Nangunhe. We found no visual or auditory evidence of them still residing at the reserve and therefore tentatively conclude that lar gibbons have become extinct in China. It appears that large-scale destruction of primary forests in the 1960s and 1970s brought about an initial decline in their numbers, and subsequent uncontrolled hunting has resulted in their extirpation. The situation for the six Chinese ape taxa is nothing less than disastrous, with 1 taxon assumed to have become extinct during the last few years, 1 taxon not having been confirmed since the 1980s, and 2 species at the very brink of extinction with only tens of individuals remaining in China.     

Boldness,Dominance, and Territoriality in the Color Polymorphic Tree Lizard,Urosaurus ornatus

Social dynamics in territorial species often reflect underlying variation in aggression and other aspects of social dominance among individuals. In ornate tree lizards (Urosaurus ornatus), males differing in dewlap color differ in social dominance: while blue males are the dominant, aggressive morph and always territorial, yellow males tend to exhibit a less‐aggressive satellite behavioral tactic. However, in habitats with fewer available territorial resources, yellow males defend territories and increase in relative abundance. These observations suggest that consideration of social dominance alone may be insufficient to explain U. ornatus' territorial dynamics in the wild. Here, we tested how both dominance and another important behavioral trait, boldness, contribute to the outcome of territorial disputes in tree lizards. We recorded the territorial behavior of blue and yellow male tree lizards (entered in pairs) in an experimental arena. At the end of each trial, we then approached each male and recorded whether it fled (shy) or not (bold) in response to our approach. As expected, dominant blue males exploited the higher quality perch more often than yellow males. However, when approached by a simulated predator, blue males were more likely to flee than yellow males. Thus, while blue males are more dominant, yellow is likely the bolder morph. As a result, this morph may be better equipped to defend territories in riskier environments. We conclude that although dominance asymmetries may predictably drive initial territorial interactions among competing males, variation in other behaviors (like boldness) may perturb the long‐term outcome of these interactions across variable environments.     

Fecal Glucocorticoid Measurements and Their Relation to Rearing,Behavior, and Environmental Factors in the Population of Pileated Gibbons (<Emphasis Type="Italic">Hylobates pileatus</Emphasis>) Held in European Zoos

Pileated gibbons (Hylobates pileatus) are rated as endangered according to the International Union of Conservation of Nature (IUCN) Red List. The captive population suffers from poor breeding success and is threatened to become overaged. Although several factors are likely to contribute to the poor breeding success, one in particular may be chronic stress associated with prolonged periods of high glucocorticoid (GC) output. We investigated fecal GC levels of pileated gibbons (Hylobates pileatus) and their relationship to specific life-history variables and environmental factors. After validation of an enzyme immunoassay for the measurement of 5-reduced 3α,11β-dihydroxy cortisol metabolites to assess GC output reliably in pileated gibbons, we collected fecal samples over several days from all 36 European adult pileated gibbons located in 11 institutions and compared GC levels to intrinsic individual parameters, husbandry, behavior, and breeding history. Age, sex, and origin (wild vs. captive born) had no effect on GC levels. However, unnaturally reared gibbons had higher GC levels and showed more behavioral abnormalities than parent-reared individuals. Further, nonreproducing gibbons living in a pair without infants had higher GC concentrations than gibbons living in a family, bachelor group, or as singletons. With respect to environmental factors, a large size of the inside enclosure and the existence of visual protection from visitors was associated with lower fecal GC output. The data indicate that rearing and housing conditions appear to correlate to GC levels in pileated gibbons housed under captive conditions. It is hoped this knowledge will support the future management of the species in captivity and thus lead to a more successful breeding of this endangered primate.     

Lek Behavior as the Mating Strategy of Setellia sp. (Diptera: Richardiidae)

A field study revealed that the mating system of the richardiid Setellia sp. meets even the most stringent definition of lek behavior. Males remain on the upper surface of the leaves of Saranthe aff. klotzchiana (Maranthaceae), where they perform ritualized displays related to courtship and territorial behavior. Correlational data support the existence of reproductive dominance hierarchies, which are based on both male vs. male and female vs. female agonistic interactions. Curiously, the behavioral acts performed by Setellia sp. show remarkable similarities to other nonrelated dipteran lekkers. Aspects of evolution and convergence of these behaviors in the Acalyptratae are considered.     

Inter- and intra-specific variation in the facial colours of <Emphasis Type="Italic">Perisesarma eumolpe</Emphasis> and <Emphasis Type="Italic">Perisesarma indiarum</Emphasis> (Crustacea: Brachyura: Sesarmidae)

The colour of the characteristic facial bands in the mangrove crabs Perisesarma eumolpe (De Man) and Perisesarma indiarum (Tweedie) were investigated in relation to species, sex and size. Quantitative red/blue/green (RBG) values extracted from close-up digital photographs of 27 P. indiarum and 48 P. eumolpe specimens revealed significant differences between species and sexes. Males of both species possessed facial bands characterized by a greater intensity of blue, whereas green was more pronounced in female facial bands. It is postulated that these colour differences play a role in intra-specific sexual recognition. There existed a significant positive relationship between size and the intensity of blue in the facial bands of females of both species, suggesting these traits function as an indicator of their maturity (and possibly body condition). In large males, facial band colours contrast strongly against the surrounding mudflat and may play an important role in conspecific signalling during territorial disputes or contests over access to females. Handling editor: K. Martens