Proboscis monkey (Nasalis larvatus) social organization: Nature and possible functions of intergroup patterns of association

Proboscis monkey (Nasalis larvatus) socioecology was studied at the Natai Lengkuas Station, Tanjung Puting National Park, in Kalimantan Tengah, Indonesia. Data on the nature of intergroup interactions were collected on ten one-male groups and two all-male groups using event sampling during follows and also through evening census surveys. Proboscis monkeys form stable one-male groups, with specific groups regularly associating at their sleeping sites (band members). Both intraband and interband high-intensity agonistic displays (slapping, chasing, biting) were rare. Lower intensity agonistic displays (vocalizations, leaping-branch shaking, and erect penis and open-mouth displays) occurred frequently. Temporal avoidance between bands may have been mediated by early morning vocalizations and branch shaking displays by the adult males. Associations between groups may play a role in displacement avoidance and/or predation avoidance.     

Deferred agonistic behavior in a long-lived scincid lizard Eumeces laticeps

Summary A laboratory experiment with the broad-headed skink (Eumeces laticeps) involving staged agonistic encounters demonstrates that larger males have an advantage over smaller ones in agonistic bouts. Field data on head wounds produced by intraspecific fighting during the breeding season show a much higher frequency of new wounds among males over 100 mm in snout-vent-length than in smaller males. The significant difference in new-wound frequency strongly suggests avoidance of fights by the small males, which is corroborated by laboratory and field observations. Access by males to reproductively active females depends on the ability to defeat other males in aggressive contests virtually always involving head biting if the males are of nearly equal size. Because the probability of winning agonistic encounters increases with size, young males avoid fights with older males. Aggressive contests with larger males and reproductive attempts other than courtship in the absence of larger males are deferred.Aggressive behavior in E. laticeps may be employed in direct defense of females, but might also be expressed in defense of specific sites and/or territories. In the laboratory, males in their home cages were significantly more likely to win encounters with males of similar size than were males fighting in the home cages of opponents. This suggests that encounter site could be important in determining encounter outcome and that field study of possible site defense or territoriality is needed.     

Aggression among sea urchins on Caribbean coral reefs

The existence and nature of intra- and interspecific aggression were examined for five species of sea urchins inhabiting Caribbean coral reefs. The studies took place in the San Blas Islands of Panama and involved the following species: Echinometra lucunter (Linnaeus), E. viridis Agassiz, Diadema antillarum Phillipi, Lytechinus williamsi Chesher, and Eucidaris tribuloides (Lamarck). An intruder was placed next to an undisturbed resident and the behaviors and responses of both individuals were followed. All pairwise combinations of resident species and intruder species were tested except for combinations involving D. antillarum as intruder.

For E. viridis and E. lucunter, agonistic interactions occurred commonly (46–79% of trials) between conspecifics and congeners. Almost all of the agonistic encounters involved pushing. Additionally, biting occurred in 8–25 % of the trials. Residents were most often the aggressors and usually succeeded in retaining their location. Intruders only succeeded in forcing residents out of their positions if the intruder was equal to or larger in size than the resident. Surveys of an undisturbed population of E. viridis during the daytime indicated that 16% of the individuals were engaged in intraspecific agonistic interactions at any one time.

D. antillarum exhibited biting behavior against both species of Echinometra in 23–24% of the trials. Biting attacks against L. williamsi and E. tribuloides occurred rarely. L. williamsi only once demonstrated pushing behavior and never was observed biting another sea urchin. E. tribuloides occasionally exhibited pushing and biting behaviors, both as residents and as intruders, and was twice observed biting Echinometra.

These studies suggest that two kinds of agonistic interactions may commonly occur among Caribbean reef-dwelling sea urchins: (1) intraspecific and interspecific aggression among Echinometra, and (2) predatory/aggressive attacks against Echinometra by D. antillarum. The former may result in greater dispersion of Echinometra relative to food and shelter resources and control the spatial distribution and concentration of Echinometra grazing pressure within an area. The attacks by D. antillarum may result in the restriction to, or higher densities of, Echinometra in crevices and rugose microhabitats that provide shelter from the larger-bodied D. antillarum.     

The effects of food level and conspecific density on biting and cannibalism in larval long-toed salamanders, Ambystoma macrodactylum

Previous studies have examined abiotic and biotic factors that facilitate agonistic behavior. For larval amphibians, food availability and conspecific density have been suggested as important factors influencing intraspecific aggression and cannibalism. In this study, we examined the separate and combined effects of food availability and density on the agonistic behavior and life history of larval long-toed salamanders, Ambystoma macrodactylum. We designed a 2Ƕ factorial experiment in which larvae were raised with either a high or low density of conspecifics and fed either a high or low level of food. For each treatment, we quantified the amount of group size variation, biting, and cannibalism occurring. Additionally, we examined survival to, time to and size at metamorphosis for all larvae. Results indicated that differences in both density and food level influenced all three life history traits measured. Moreover, differences in food level at which larvae were reared resulted in higher within-group size variation and heightened intraspecific biting while both density and food level contributed to increased cannibalism. We suggest that increased hunger levels and an uneven size structure promoted biting among larvae in the low food treatments. Moreover, these factors combined with a higher encounter rate with conspecifics in the high density treatments may have prompted larger individuals to seek an alternative food source in the form of smaller conspecifics.     

Agonistic behavior in crayfish in relation to temperature and reproductive period

Summary I examined the relationship between temperature and agonistic behavior in the crayfish Cambarus latimanus LeConte a species which is reproductively active in winter. Crayfish were acclimated for 2 wks at 9.5, 14, 22 and 30°C in summer and at 9.5 and 22°C in winter. Agonistic behavior of pairs of the same sex was recorded for 1 h following acclimation. The entire acclimation, testing, and temperature-readjustment procedure was repeated until all crayfish pairs had been tested at each acclimation temperature.Published information on lobsters and catfish indicate that agonistic behavior is directly related to temperature. In contrast, for C. latimanus in the present study, duration of total agonistic behavior, maximum duration of a single agonistic interaction, and average length of a agonistic encounter were all inversely related to acclimation temperature. I hypothesized that for ectothermic species whose agonistic behavior is closely associated with reproductive processes (including competition for mates) the level of agonism will vary either directly or inversely depending upon whether the reproductive period is cued by increasing or decreasing seasonal temperatures, respectively.     

Temporal Pattern of Agonistic Interaction in Two Gerbil Species (Rhombomys opimus and Gerbillus perpallidus) Differing in Resistance to Social Pressure

This study compares temporal patterns of intraspecific agonistic interactions in two gerbil species in order to indicate interspecific differences in levels of social resistance. Both cross-sex and same-sex pairs of great gerbils (Rhombomys opimus Licht., 1823), and only same-sex male pairs of pallid gerbils (Gerbillus perpallidus Setzer 1958) were observed during staged encounters on a neutral arena. Analysis of three latency measures—latency to first agonistic interaction; latency to overt aggression (attack and/or ‘arrested’ fight); and latency to establishment of a stable winner-loser asymmetry among opponents—revealed both similarities and differences among the species. Latencies to first agonistic interaction were similar (did not differ significantly) among species and sexes. However, great gerbil males showed significantly more long latencies to establishment of a stable asymmetry among opponents, than great gerbil females or pallid gerbil males. So, the periods of symmetrical struggle in agonistic conflict last longer in great gerbil males, than in great gerbil females or pallid gerbil males. These differences in temporal pattern of agonistic interaction may reflect sex and species differences in resistance to social stress.     

Territorial behaviour of the red-backed salamander: Expulsion of intruders

Red-backed salamanders, Plethodon cinereus, were paired in laboratory chambers where they defended areas against each other by threat display and biting. Difference in sizes of paired individuals was not correlated with which one would enter the other's area or be more aggressive after an intrusion. We also found no sexual differences in agonistic behaviour. Both defenders and intruders assumed a threat posture for about 50% of the invasion periods, but defenders exhibited a higher rate of biting. Defenders expelled intruders in 74% of all encounters, while intruders expelled defenders in 18%, with 8% of the encounters a draw. Intruders frequently left the contested area even in the absence of biting or threat display by the defender, apparently in response to the defender's pheromones or to the high potential cost of an escalated aggressive contest (damage to the chemosensory structures). These data provide behavioural evidence that a salamander can evict intruders from a defended area and thus support the hypothesis of territoriality among terrestrial salamanders.     

Courtship song, male agonistic encounters, and female mate choice in the house cricket,Acheta domesticus (Orthoptera: Gryllidae)

Whether female crickets choose among males based on characteristics of the courtship song is uncertain, but in many species, males not producing courtship song do not mate. In the house cricket,Acheta domesticus, we examined whether a female chose or rejected a male based on his size, latency to chirp, latency to produce courtship song, or rate of the high-frequency pulse of courtship song (“court rate”). We confirmed that females mated only with males that produced courtship song, but we found no evidence that the other factors we measured affected a female’s decision to mate. In addition, we investigated whether the outcome of male agonistic encounters affected the subsequent production of courtship song. In one experiment, we observed courtship and mating behavior when a single female was placed with a pair of males following a 10-min interaction period between the two males. Winners of male agonistic encounters had higher mating success. However, winners and losers of agonistic encounters were not different in their likelihood or latency to produce courtship song or in the number of times they were disrupted by the other male in the pair. In a second experiment, we allowed two males to interact for a 10-min period, but following this interaction period, we placed a female with each male separately and observed courtship and mating behavior. The mating success of winners and losers was not different under these circumstances, and we found no differences between winners and losers in any subsequent courtship or mating behavior examined. We conclude that winning agonistic encounters influences a male’s mating success in ways other than his production of courtship song and this effect is lost when winning and losing males are separated and each is given an opportunity to mate.     

An ethological analysis of types of agonistic interaction in a captive group of Java-monkeys (Macaca fascicularis)

The primate literature provides many indications not only that the nature of dyadic interactions is to a large extent determined by the relations of the interacting animals with others and between these others, but also of the existence of polyadic interactions in which more than two individuals are simultaneously involved. The objectives of the present study are to obtain a quantitative categorization of the agonistic interaction types of captive Java-monkeys and an analysis of their dynamics. After having described the agonistic behaviour patterns of Java-monkeys we shall discuss the categorization of agonistic interaction types (depending on the number of involvees: “dyads”, “triads” and “polyads”), the way in which these types can be further differentiated on the basis of the nature and the direction of the behaviours shown (e.g., different types of alliances), and the existence of so-called “sub-directed” behaviours (i.e., non-agonistic behaviours which are shown towards a dominant third animal more or less simultaneously with aggressive behaviour directed towards an opponent). The analysis indicates that agonistic behaviour is different both in its form and its regulation in interactions of different complexity. This research was supported in part by a government grant (i.e.: Beleidsruimte project: 16-21-06, “Brain and Behaviour”) to the first author. The investigation was supported by a grant from the Beleidsruimtemiddelen Hersenen en Gedrag to the first author.     

EVOLUTION OF SOCIAL BEHAVIOR IN A RESOURCE-RICH,STRUCTURED ENVIRONMENT: SELECTION EXPERIMENTS WITH MEDAKA (ORYZIAS LATIPES)

Schooling and aggression in fish are known to be partially inherited traits. Their genetic relationship to growth rate and to each other is, however, not fully understood. In this study we present evidence that schooling, social tolerance, and agonistic behavior in medaka (Oryzias latipes) are altered as an indirect result of selection on growth in two environments that differed in the intensity of social interactions required to obtain access to food. In the high interaction environment food was provided to excess inside a floating cork ring, which limited access to the food and allowed fish to attempt to monopolize it. In the low interaction environment the same amount of food was spread over the container's surface. After two generations of selection on growth the correlation of agonistic behavior and mean growth of broods was negative in the line selected for fast growth, when selection took place in a high interaction environment, but not when it took place in a low interaction environment. School cohesion was higher in the lines selected for fast growth than in those selected for slow growth when selection and rearing environments were both the same, either high or low interaction, but not when they were different. The correlation of social tolerance with growth was significantly more positive in the line selected for fast growth than in that selected for slow growth, but only when selection took place under high social interaction. It appears from these experiments that when resources are aggregated, but unlimited in quantity, competition favors individuals that avoid wasting time and energy on unnecessary and ultimately futile attempts to monopolize food and that also exhibit higher tolerance of nearby conspecifics. The results are interpreted in terms of a hypothesized stimulus-response threshold level for agonistic responses to conspecifics. We suggest that this threshold, which is altered by selection on growth, could provide a common causal (genetic) link between growth and the observed aspects of social behavior. By combining the probabilities from the separate behavioral experiments to obtain an overall significance of our hypothesis we conclude that the probability of no change in threshold is in fact low (P < 0.01).     

Seasonal variation in abundance and diversity of eavesdropping frog‐biting midges (Diptera,Corethrellidae) in a neotropical rainforest

1. In the tropics, precipitation patterns result in seasonal fluctuations in the abundance and distribution of plant and animal species. Tropical predators and parasites are therefore faced with seasonal changes in prey and host availability. 2. This study investigates the seasonal interaction among a specialised ectoparasite, eavesdropping frog‐biting midges (Corethrella spp.), and their anuran hosts, examining how the abundance and diversity of the frog‐biting midge community fluctuate between the rainy (host abundant) and dry (host sparse) seasons. 3. Midges were captured in both the rainy and dry seasons using acoustic playbacks of calls from a common frog species that breeds during the rainy season, the túngara frog (Engystomops, Physalaemus, pustulosus). During the dry season túngara frog choruses are absent. To explore seasonal shifts in host preference or changes in the midge community due to host specificity, midges were also captured using playbacks of calls from a frog that breeds during the dry season, the pug‐nosed tree frog (Smilisca sila). 4. While the overall abundance of midges decreased in the dry season, only slight differences in the relative abundance between midge species were found. These results suggest that midge populations can shift between hosts as they become available across seasons, allowing adult populations of frog‐biting midges to persist year‐round. To overcome the challenge of detecting and localising different host species, it is proposed that frog‐biting midges have evolved a generalised acoustic template, allowing them to respond to a broad range of available hosts, regardless of seasonal host composition.     

Postconflict affiliative contacts between former opponents among wild moor macaques (Macaca maurus)

Agonistic interactions and postconflict behavior of moor macaques (Macaca maurus) were studied in their natural habitat, South Sulawesi, Indonesia. Individuals were involved in 0.28 agonistic interactions per hour. Forty-two percent of agonistic interactions were followed by affiliative contacts between the former opponents. Such affiliative contacts occurred within 2 minutes of the agonistic interaction and were most often initiated by the victim's approach to the aggressor. The most common postconflict behavior was grooming of the aggressor by the victim. The present study provides further evidence of a positive correlation between a high tendency for postconflict affiliative contact and a relaxed dominance style. Captivity might not alter the expression of postconflict behavior. The present study suggests that it is possible to demonstrate the occurrence of reconciliation a posteriori by using data obtained by general focal observation protocols. © 1996 Wiley-Liss, Inc.     

The expression of aggression in old world monkeys

The expression of agonistic behavior in adult and juvenile members of both sexes was studied in groups of from 23 to 93 animals representing Macaca mulatta, M. arctoides, M. nemestrina, M. nigra, and Cercocebus atys. Data were collected using focal animal techniques over a period of 1 year for each group. Adult male biting was notably infrequent in all cases, and adult male participation in agonistic encounters was less frequent than for any other age-sex class, especially in the groups with the highest agonistic rates. Adult male agonistic behavior was often expressed as aggression but seldom involved contact forms of aggression, and biting constituted the smallest proportion of contact aggression for all age-sex classes. Adult males were also seldom the targets of aggression and had the highest rates for shaking of objects and bouncing displays. A tendency for the most severe forms of aggressive expression to be most frequent in those animals least capable of inflicting injury was noted in all groups, along with a tendency for aggression to be directed toward immature animals. Sex differences in aggressive expression and responses to aggression were noted, but the frequency of receipt of aggression was not directly reflected in the wounding noted. Different means to achieve the same consequence, infrequent adult male damaging attacks, are suggested to operate in the several groups studied.     

Anopheles gambiae gonotrophic cycle duration, biting and exiting behaviour unaffected by permethrin-impregnated bednets in The Gambia

Abstract. Permethrin-impregnated bednets protect children against malaria in The Gambia, where Anopheles gambiae complex mosquitoes are the main vectors of malaria. However, no effect has been found on mosquito density, parous rates or sporozoite rates in An.gambiae sensu lato populations; only a reduction in the numbers of mosquitoes resting indoors in rooms with treated bednets. A possible explanation for this paradox is that exposure to treated bednets leads to changed vector behaviour such as a shift in biting time, a diversion to biting outdoors instead of indoors, to biting animals instead of humans, or to increased duration of the gonotrophic cycle. To investigate these possibilities, we observed the biting and exiting behaviour of An.gambiae in ten pairs of villages, in half of which the residents used permethrin-treated bednets. The possible influence of treated bednets on the gonotrophic cycle length was evaluated by mark-release-recapture experiment. No significant difference was found between villages with treated and untreated bednets in the indoor/outdoor ratio of human biting, in mean biting times or in human blood indices of An.gambiae females found resting indoors in the mornings. The proportions of unfed, fed or gravid An.gambiae females collected in exit traps, and the number of females exiting showed no significant differences between rooms with treated and untreated bednets. Indications for a gonotrophic cycle length of 2 days were found. No evidence for any change in duration of the gonotrophic cycle in relation to exposure to treated bednets was found, although the number of recaptures was low in the villages with treated bednets. Since equal numbers of infective An.gambiae were found in villages with treated or untreated bednets, and no changes in mosquito behaviour were detected, we cannot account for how children are protected against malaria by treated bednets. One possibility is that mosquitoes divert to bite other hosts, including adults.     

Coprophagy-related interspecific nocturnal interactions between Japanese macaques (<Emphasis Type="Italic">Macaca fuscata yakui</Emphasis>) and sika deer (<Emphasis Type="Italic">Cervus nippon yakushimae</Emphasis>)

The influence of sympatric large animals on the sleeping behavior of primates in the wild is still largely unknown. In this study, we observed behaviors of wild Japanese macaques (Macaca fuscata yakui) at their sleeping sites, using a highly sensitive video camera. We found evidence of nocturnal interspecific interactions, such as agonistic interactions, between Japanese macaques and sika deer (Cervus nippon yakushimae). Deer approached sleeping clusters of macaques, which slept on the ground, to eat their feces or unidentified materials near the sleeping clusters, and as a result, the macaques were often quickly displaced from their sleeping site. There was a significant difference in the occurrence of macaque–deer agonistic interactions between seasons. Our results suggested that the size of the sleeping cluster, the number of adult macaques in the cluster, and the existence of adult males in the cluster did not influence the occurrence of the agonistic interactions. Finally, we discuss the influence of this interaction on macaques and speculate on the influential factors leading to nocturnal coprophagy of macaques’ feces by deer.     

The variability of some motor components of social play and agonistic behaviour in infant eastern coyotes, Canis latrans var

The duration and stereotypy (in terms of duration) of three actions, stand-overs (SO), generalbites (GB), And scruff-bites (SB), were measured during social play and agonistic interactions in infant eastern coyotes (Canis latrans). The rate of biting was also calculated. We found: (1) SO's and GB's lasted a significantly shorter time during play; (2) when performed during playful interactions, all three acts showed more stereotypy; (3) there was no significant difference between the rates of occurrence of biting during the two situations. A discussion of the 'exaggerated' nature of play behaviour is presented, particularly concerning the form of motor actions that are used during this activity.     

Seasonal dynamics of agonistic behavior and hormones in an ex situ all‐male colony of large flying foxes

Large flying foxes (Pteropus vampyrus) are a socially complex species. In situ colonies typically comprise thousands of individuals in small harems of one male to many females. In ex situ environments, all‐male colonies are becoming more common due to a surplus of males in the population. There is limited information describing the hormonal and behavioral patterns of all‐male colonies during the breeding season. We assessed seasonal changes in hormones and behavior in an all‐male colony of 12 large flying foxes at Disney's Animal Kingdom^®. We validated hormone assays using morning urine and fecal samples to assess seasonal changes in excreted immunoreactive testosterone and glucocorticoid metabolites. We collected behavior data using an all‐occurrence method, recording agonistic behaviors related to territorial defense (hooking, biting, wing flexing, vocalizing, and wrestling), and sexual behavior (mounting and frontal grabbing). Results indicated that (i) we could reliably measure testosterone and glucocorticoid metabolites concentrations from fecal and urine samples collected from individual bats; (ii) there were distinct relationships between changes in levels of agonism and hormone concentrations throughout the year; and (iii) three agonistic behaviors (chasing, wrestling, and open‐mouth threat) peaked prior to the increase in testosterone and glucocorticoid hormones measured during the breeding season. These three behaviors could potentially be used as early indicators to signal the onset of the breeding season and allow time to implement ex situ management changes to reduce the incidence of agonism between individuals.     

Behaviour of Arctic charr Salvelinus alpinus during an induced mating season in captivity: how male relative size influences male behavioural investment and female preference over time

The behaviour of sexually mature Arctic charr Salvelinus alpinus specimens (fifth farm generation) was observed in captivity for four consecutive days. Only agonistic interactions between males of different size were facilitated on the first 2 days, while both agonistic and courtship interactions were possible from the third day up to the end of the experiment. The reliability of behavioural analysis was assessed in order to reduce the possibility of observer errors within the generated datasets. The behavioural investment of big males, small males and females was analysed using general linear models (two‐way repeated measures ANOVAs with time and male size as factors). A peak in the agonistic interactions between males occurred during the first day of interactions, where the agonistic investment of big males was significantly higher than that of small males. This resulted in an increased investment in submissive behaviour by the small males, who consistently performed submissive behaviours from the second day of interactions up to the end of the trial. Big males were found to invest significantly more than small males in courtship behaviours for the duration of the trial. Even though females performed inter‐sexual behaviours towards both big and small males for the entire observation period, female interaction rate towards big males was higher than towards small males. This study suggests that both male investment in mating behaviour and female preference might be related to male characteristics such as body length and that S. alpinus behavioural patterns and mate choice cues might be strongly context‐related and characterized by high levels of behavioural plasticity (i.e. presence–absence of certain behavioural units or potential reversal of a mate choice cue) within the same species. Finally, in light of this, some conservation measures are discussed. In particular, effective management plans should take into account the high level of behavioural plasticity likely to be occurring in this species.     

Social relations in family-groups of wood miceApodemus sylvaticus under laboratory and enclosure conditions

Two family-groups of wood miceApodemus sylvaticus (Linnaeus, 1758) were observed: one in the laboratory (terrarium 100 × 60 × 60 cm) and the other under enclosure conditions (outdoor enclosure 200 × 100 × 100 cm). Three consecutive periods in the social relations of the family-groups were described: the linear hierarchy, the multidirectional social relations, and the variable dominance-subordination relations. The linear social hierarchy was reflected in the subordination behaviour of family members in relation to the dominant male, the father of the family. During the period of coexistence of a pair of parents with two litters of juveniles, both in the laboratory and under enclosure conditions, amicable relations between individuals occurred. Advanced forms of social care (paternal care, allomaternal lactation, transportation and licking by relatives) were also observed. In the laboratory, agonistic interactions were lacking during the linear hierarchy period, but the attainment of sexual maturity by individuals of the first two litters, accompanied by an increase in the number of mice, resulted in aggression between mature males and competition for dominance. Further, under increasingly crowded conditions, agonistic behaviour prevailed over other types of social interaction, and the survival rate of juveniles decreased. Under enclosure conditions a seasonal variation in agonistic interaction between mature individuals was recorded, similar to that observed in the wild. Despite the systematic increase in population density, no attacks by mature males on juveniles were observed.     

Analogs of a superacidic NMDA receptor agonist, N-phthalamoyl-L-glutamic acid (PhGA): Activity and mode of interaction with the receptor recognition site

Studies of the effects of analogs of N-phthalmoyl-L-glutamic acid (PhGA, experiments on freshly isolated hippocampal neurons of rats and on mice using intracerebroventricular injection) were compared with the molecular modeling studies. Transmembrane currents evoked by applications of NMDA receptor agonists were recorded using a patch-clamp technique. Interaction of phGA derivatives with the NMDA receptors was examined by comparing their agonistic activity with that of L-aspartate. It was found that the derivatives (iso- andtere-PhGA), which contain three carboxylic groups, display a strong agonistic activity. The absence of carboxylic groups in the molecule of an agonist and lengthening of the methylene chain in the aliphatic part of the molecule result in a drop in agonistic activity.