Showing papers in "Behaviour in 1997"

Divergent Systems of Agonistic Behaviour in Lemurid Primates

Abstract: Two semifree-ranging groups of ringtailed lemurs (Lemur catta) and two co-ranging groups of redfronted lemurs (Eulemur fulvus rufus) were studied across a two-year period to characterise and contrast the adult agonistic behaviour these primates exhibit within groups. Temporal analyses of behavioural data distinguished agonistic from non-agonistic behaviour and aggressive from submissive behaviour. The ringtailed lemurs employed a diverse repertoire of behavioural elements to communicate agonistic intent. More than 50% of these elements were signals and nearly 50% of signals were submissive. The agonistic repertoire of the redfronted lemurs, by contrast, was relatively unelaborated: less than 40% of agonistic behaviour in this species comprised signals and less than 20% of signals were submissive. These structural differences underlay marked species differences in agonistic interaction and relationship. All pairs of ringtailed lemurs maintained dominance relations resembling those seen in many anthropoid primates: subordinates consistently signalled submissively to dominant partners, often in the absence of aggression. Dominance relations among members of each sex were seasonally unstable and not always transitive (hierarchical) during periods of stability, however. Redfronted lemurs, by contrast, did not maintain dominance relations, failing to respond agonistically to most aggression received (52% of interactions) and responding with aggression on many other occasions (12%). Even applying relaxed criteria, few adult redfronted dyads (14%) showed consistent asymmetries in agonistic relations and several never exhibited any asymmetry. Lacking dominance, E. f rufus relied heavily on alternate behavioural mechanisms to moderate social conflict as frequent and intense as that seen in study groups of ringtailed lemurs. These included a great inclination not to respond agonistically to aggression, a distinctive behavioural proposal to limit or terminate dyadic conflict (Look away), post-conflict reconciliation, and relatively frequent third-party aggression. The existence of such divergent systems of agonistic behaviour in partially sympatric, closely related and generally similar prosimian primates offers important opportunities for comparative study of the ecology, development, and evolution of mammalian social systems. Future research may reveal ecophysiological factors that promote the use of dominance behaviour among like-sexed ringtailed lemurs and show how the relative absence of dominance relates to other major elements of redfronted lemur biology, including 'special relationships' of variable duration between adult males and females.

Mortality risk of spatial positions in animal groups: The danger of being in the front

Abstract: We modified Hamilton's (1971) selfish herd model by introducing directional movement to the prey groups and the predators. The consequences of this modification with regards to differential predation risks are compared to Hamilton's original model (using stationary prey groups) and tested against empirical data. In model 1, we replicated Hamilton's original predator-prey system. In models 2 and 3, prey groups were mobile and predators were mobile (model 2) or stationary (model 3). Our results indicate that additional to the positive risk gradient from centre to periphery predicted by Hamilton's model for stationary groups, there might be another positive risk gradient from the rear to the front part in moving groups. Furthermore, models 2 and 3 suggest that moving groups should generally exhibit an elongated shape (longer than wide along the axis of locomotion) if risk minimisation is the only factor concerned. Also smaller inter-individual distances are predicted for front individuals than individuals elsewhere in the group. Empirical data based on the three-dimensional structure of fish shoals (using roach, Rutilus rutilus) were consistent with the above two predictions. A second experiment which involved lake chub, Semotilus atromaculatus, as prey and rock bass, Ambloplites rupestris, as predators, provided direct support for the hypothesis that individuals in front positions of groups incurred a significantly higher predation risk than fish in rear positions. Finally, we discuss the differential risks of different group positions in the context of potential foraging gains which provides the basis for a dynamic model of position preferences in group-living animals.

Male-Female Social Relationships in Wild White-Faced Capuchins (Cebus Capucinus)

Abstract: Male white-faced capuchins are expected to have tense, yet cooperative, relationships because they must compete for matings in an intragroup context, yet males of the same group need one another's support for intergroup competition for mates. In this paper, I examine in detail the social relationships of the 4 adult males in a single social group of wild white-faced capuchins at Lomas Barbudal Biological Reserve, Costa Rica. There was a clear alpha male, to whom all other males deferred; however, there was no obvious linear ranking among the subordinate males. Urine rubbing and branch displays were performed more often by the alpha than by subordinate males, though one subordinate male increased his rates of these behaviours when the alpha male was out of view. The alpha male formed coalitions with subordinate males against other males, but pairs of subordinate males never formed coalitions against the alpha male. The alpha male was not consistent with regard to which subordinate male he supported in triadic interactions. Affiliative interactions between subordinate males were consistently disrupted by the alpha male. Males cooperated with one another in the context of defense against predators and defense against males of other social groups. Relaxed affiliation and close proximity between males were rare, in comparison with male-female and female-female dyads. Tense affiliation (e.g. wheeze dances, play, and rough grooming) was most common following a change in alpha male, when aggressive interactions were also more common. Despite males' relatively low rates of affiliation and proximity, males actively searched for one another when a male was missing from the group for an extended period of time.

Behavioural Indicators of Anxiety: an Empirical Test in Chimpanzees

Abstract: Behavioural, pharmacological, and physiological evidence supports an association between displacement activities and anxiety in macaques. Information is scarce in other primate and non-primate species. This study contributes to the understanding of the relation between displacement activities and emotional states by investigating the correspondence between self-directed behaviour and an inherently stressful situation in chimpanzees (Pan troglodytes). Data were collected on 81 captive chimpanzees housed in conditions varying from indoor single caging to indoor/outdoor enclosures containing up to 14 individuals. Observation of gentle and rough scratching, self-grooming, and yawning were used to test predictions concerning the response of individuals to neighbour vocalisation (i.e. the calls and noisy displays produced by neighbouring groups of chimpanzees), which has been previously demonstrated to increase the likelihood of intragroup agonistic behaviour. In socially-housed chimpanzees rough and gentle scratching and yawning were significantly more common after neighbouring individuals vocalised or displayed than before, but the effect lasted longer for rough-scratching. In addition, during periods characterised by higher levels of neighbour vocalisation, socially-housed chimpanzees performed rough scratching at higher rates. Self-grooming was not affected by the level of neighbour vocalisation. Single-caged chimpanzees, for whom neighbour vocalisation carries no risk of aggression by group members, showed no increase in self-directed behaviour when neighbour vocalisation level was high, suggesting that the risk of intra-group aggression, rather than neighbour vocalisation itself, elicits anxiety. While our study suggests that rough scratching is the most reliable indicator of anxiety in chimpanzees in the context of neighbour vocalisation, it also provides evidence that gentle scratching and yawning can be considered displacement activities in this species.

Ontogeny of Diving Behaviour in the Galápagos Fur Seal

Abstract: We studied the ontogeny of diving behaviour in the Galapagos fur seal (Arctocephalus galapagoensis, Heller 1904). Six-month-old seals spent less than 12% of observation time at sea and were entirely dependent on maternal milk for nutrition. Maximum dive depths for this age group averaged 5.6 m, maximum durations 50 s (N = 12). Modal swim speeds averaged 0.55 m/s; maximum observed swim speeds ranged from 0.9-2 m/s (N = 5). Six-month-old seals swam distances of 2.9 km/24 hrs on average (N = 5). No diel patterns were apparent in their diving behaviour. One-year-old fur seals were the youngest age group to show substantial diving activity, reaching maximum depths of 47.5 m and durations of 2.4 min on average (N = 21). Modal swim speeds averaged 0.9 m/s, maximum speeds ranged from 1.4-2.3 m/s (N = 6). Total distances traveled averaged 15.4 km/trip to sea. Yearlings spent 23.9% of observation time at sea, the majority (> 95%) of that at night. This corresponds to the activity pattern of adult females who dive exclusively at night. Yearlings were the youngest age group to contribute to their own nutrition through independent foraging, but were still dependent on their mothers: no yearlings were successfully weaned in this study. 18-month-old seals were better divers, spending 27.6% of observation time at sea, mostly during the night. Maximum dive depths for this age group averaged 61.1 m; durations 3.1 min (N = 11). Modal swim speeds averaged 1.4 m/s (N = 4), and were comparable to modal speeds of two adult females of 1.2 and 1.6 m/s. Maximum speeds for these juveniles ranged from 2.2-2.7 m/s (N = 4); the two adult females reached 2.8 and 4 m/s respectively. Total travel distances averaged 42 km/trip to sea (N = 4 juveniles). These distances corresponded to those covered by two adult females, 43 and 45 km/trip. Two-year-old fur seals included the youngest that were successfully weaned in this study. They spent 35% of observation time at sea, primarily at night. Maximum dive depths averaged 69.7 m, durations 3.4 min (N = 20). Adult females were the best divers in this study, spending 49.5% of observation time at sea, almost exclusively at night. Maximum dive depths averaged 106.5 m, durations 4.5 min (N = 32). During ontogeny, age was the best predictor of time spent at sea. For animals older than six months, body mass was the best predictor for maximum dive depth as well as maximum and median durations. The physiological maturation process precludes weaning before the age of one year. After that, the diving capacity of young fur seals takes a central role in the weaning process, in conjunction with the temporal patterns of relative prey accessibility.

Female Dominance Relationships and Food Competition in the Sympatric Thomas Langur and Long-Tailed Macaque

Abstract: Aggressive interactions can serve to secure resources. These interactions determine female dominance relationships, which have been related to the monopolizability of food patches. Patches of medium size, relative to group size, cause within-group contest competition which is hypothesized to produce linear, nepotistic and formalized dominance relationships. Small dispersed or very large and abundant patches lead to reduced within-group contest competition which should lead to egalitarian and individualistic dominance relationships without a formal hierarchy. This relation was investigated in two sympatric primate species at Ketambe, Northern Sumatra: the Thomas langur (Presbytis thomasi) and the long-tailed macaque (Macaca fascicularis). The female dominance relationships of the two species differed as predicted. Both species engaged in competitive interactions for food. The Thomas langurs competed in small patches, but not in large patches. These large patches could be considered abundant. About two-thirds of their food patches incited contest competition. Long-tailed macaques were aggressive in fruit patches, irrespective of size. Most food patches incited contest competition. Contest competition was probably more important for macaque females than for langur females. Outside food patches macaque females were more aggressive than langurs, whereas inside food patches aggression rates were similar.

The Hamilton and Zuk Hypothesis Revisited: a Meta-Analytical Approach

Abstract: The Hamilton & Zuk (1982) hypothesis of parasite-mediated sexual selection has been the subject of both inter- and intraspecific tests. Past reviews have used vote counting to determine whether this hypothesis is supported by empirical evidence. This study reanalysed 199 separate quantitative assessments of a central prediction of the Hamilton & Zuk hypothesis using meta-analytical techniques. Overall, our meta-analysis showed that there was a significant negative effect of parasites on male showiness as predicted. However the magnitude of this effect varied between host taxa and between endo and ectoparasitic taxa. As a whole intraspecific correlations between parasite load and male showiness provided very little support for the hypothesis with only the effect of parasites on fish morphology matching the Hamilton & Zuk prediction. There was more support for the hypothesis from interspecific studies especially those based upon the original Hamilton & Zuk (1982) data set, although other bird studies provided weaker support. The generality of the Hamilton & Zuk hypothesis in respect to parasite mediated sexual selection across taxa is thrown into doubt by these results. However, in some specific host-parasite systems the role of parasites appears important and future intraspecific tests of parasite-mediated sexual selection should perhaps focus on such systems.

Group encounters in wild gibbons (Hylobates lar) : Agonism, affiliation, and the concept of infanticide

Abstract: 1. Gibbons are the least studied apes and traditionally thought to live in nuclear families of 2-6 individuals including a pair of breeding adults who maintain lifelong, sexually monogamous relationships and vigorously defend territories against neighbours. The present paper challenges this view. 2. During a long-term study on white-handed gibbons (Hylobates lar) in Thailand's Khao Yai rainforest, 162 encounters were recorded between 3 habituated and 8 non-habituated groups. Encounters characterized 9% of the activity day (mean 8.31 h). Those between habituated groups were nine times more frequent (0.7/day) and lasted significantly longer (median 70 min) than encounters with non-habituated neighbours (median 38 min). It was also found that gibbon group home ranges (mean 24 ha) overlap extensively (64%) with neighbours', all of whom were met. However, most previous studies centered on single groups surrounded by unhabituated neighbours. This produced underreporting of the importance of inter-group interactions, particularly the affiliative aspects observed presently. 3. Encounters included many elements which seem to have a 'defensive' function. Chases occurred during 61%, contact aggression during 8-9%; each adult and subadult male chased all others and was chased by all others. Moreover, encounters occurred often in or near food trees and rates peaked during the early morning when ripe fruit were most abundant. However, a seasonal correlation between the rate of encounters and (crude) measures of resource availability could not be detected. 4. The study indicates that gibbon groups are structured by female resource-defense and male mate-defense because adult females led 76% of all travels into and out of fruit trees, whereas males moved to the front as soon as neighbours were encountered. Male-male interactions constituted 90% of all inter-group chases. This pattern is compatible with the idea that conflicts over food sources (which can be shared) will rarely provoke contact aggression. Control of mate access, on the other hand, has a much higher relative value for males. These explanations are more parsimonious than the traditional concepts of 'pairbonding' and 'territoriality'. 5. Contrary to earlier assumptions, encounters were nevertheless not always dominated by aggression. Groups fed, traveled or rested together for prolonged times (35% of encounters). Inter-group play between immatures was likewise common (21 % of encounters; 55% dyadic, 45% triadic and quartetic play). Same-aged play partners are not present in a gibbon's natal group. However, gibbon youngsters clearly preferred age-mates during inter-group play which may indicate that play is ontogenetically important. 6. The adult female of one group copulated not only with her pair-mate, but also with two neighbouring males. The overall proportion of extra-pair-copulations (EPC) was 12% and they occurred during a period when the female conceived. Encounters thus provide opportunities for alternative mating strategies. However, philandering males are faced with the dilemma to lower their mate guard which creates a risk of cuckoldry for themselves. This could explain why subadults are often tolerated in natal groups beyond sexual maturity, because they assisted the resident adult male during agonistic encounters. Moreover, females gave solo great calls during a quarter of all encounters. These calls increase the costs of philandering for the paired male (who cannot answer without giving away that his female is unguarded) and may at the same time attract neighbouring males. 7. For the first time, close spatial proximity and body contact between intruding adult males and infants of neighbouring groups are reported, including play (during 6% of all inter-group play sessions). Immatures were at times relaxed but at other times frightened in the presence of neighbouring males. A near-zero mortality of infants at Khao Yai shows that infanticide is absent or at least not a regular occurrence. EPCs and a long period of pre-conception copulations could be strategies of females to confuse paternity and forestall infanticide. In any case, the non-monogamous mating pattern makes it likely that kin-relationships extend well into neighbouring groups. A reduced level of inter-group competition and aggression is therefore not surprising.

A Comparative Study of Aggression and Conciliation in Three Cercopithecine Monkeys (Macaca Fuscata, Macaca Nigra, Papio Papio)

Abstract: Patterns of aggression and reconciliation were studied in three captive groups of monkeys belonging to different species: Japanese macaques (Macaca fuscata), crested macaques (M. nigra) and Guinea baboons (Papio papio). Consistent differences were found comparing same dyads of individuals in the three groups. Aggression was often followed by retaliation and reconciliation in the group of crested macaques, such responses occurred less frequently in the group of Japanese macaques, more variable results were found in the group of Guinea baboons. Aggressive manual contacts occurred more frequently in crested macaques than in the other two groups. Rates of biting did not differ consistently among groups but bites could induce bleeding in the group of Japanese macaques. The use of peaceful interventions in conflicts was common in crested macaques, rare in Guinea baboons and unobserved in Japanese macaques. Data from other studies indicate that the contrasts found between groups could be due to interspecific variation. The present results suggest that the covariation between conciliation rates, degree of symmetry in conflicts and level of intensity in aggression may stem from phylogenetic constraints.

Anti-Predator Responses To Conspecific and Heterospecific Skin Extracts By Threespine Sticklebacks: Alarm Pheromones Revisited

Abstract: Under laboratory conditions, we investigated the presence of chemical alarm signals in the threespine stickleback (Gasterosteus aculeatus). We exposed individual threespine sticklebacks to skin extract of conspecifics originating from either the same or a different population, fourspine sticklebacks (Apeltes quadracus; a member of the same prey guild as the threespine stickleback) or swordtails (Xiphophorus helleri), a species not known to possess alarm pheromones and which is phylogenetically distant and allopatric from the threespine stickleback. Threespine sticklebacks exhibited significant increases in anti-predator behaviour patterns when presented with skin extract from both populations of conspecifics and from fourspine sticklebacks, but not to swordtail skin extract. These results suggest, contrary to previous reports, that threespine sticklebacks possess chemical alarm signals, which appear to be similar to those of Ostariophysan fishes.

The Function of Green Plants in Nests of European Starlings (Sturnus Vulgaris)

Abstract: European starlings add fresh green plants to their dry nest material. Male starlings of our 60-nest-box colony carried 68 different plant species into their nests. Some males were polygynous and had 3-6 clutches, others were monogynous and had 1-2 clutches per reproductive season. The 'nest protection hypothesis' proposes that insecticidal compounds in green plants reduce the parasite load of the nests. The 'courtship hypothesis' predicts that carrying nest greenery is a courtship activity to attract females. The aim of this study was to collect field data suitable for distinguishing these two hypotheses. 1. Some plant species occurred more often in the nest-boxes than expected from their frequency in the nest-box environment. A significant number of these preferred plants were rich in volatiles, some of which are said to be insecticidal. But volatiles could also attract females and/or influence their breeding activity and the chicks' development directly. 2. The males carried greenery into their nest boxes maximal around 5 days before the onset of laying, when pair formation took place, and ceased this behaviour with egg deposition. The total amount of greenery deposited in a nest-box was a function of the number of days of courtship a male needed to attract a female. 3. Polygynous males deposited the same amount of greenery in their first nest as monogynous males. In additional nests polygynous males deposited more greenery. However, this was due to the fact that these additional nests were advertised for a longer time.

Agonistic interventions in wild mountain gorilla groups

Abstract: Data on a large sample of interventions that individuals in two mountain gorilla (Gorilla gorilla beringei) groups made in agonistic interactions between others corroborate and extend earlier analyses in several ways. Related females supported each other as often as those in some female-bonded primates and maintained alliances while they resided together. Most unrelated females rarely supported each other, but some developed alliances. Females mostly supported other females with whom they had affinitive relationships against those they often engaged in dyadic aggression. They showed reciprocity in support, and often intervened against individuals who, in turn, often intervened against them. But even female coalitions that outnumbered their opponents by more than two-to-one had limited effectiveness, largely because males intervened in many female contests to control aggression. By rendering coalitions ineffective, males contribute to a combination of factors (e.g. low potential to gain from cooperation in contest feeding competition) that limit the benefits of female philopatry. Male curtailment of female aggression may influence female mate choice. Co-resident mature males in the study groups competed to control female aggression. High-ranking males curtailed aggression to females by subordinates, although two males formed an alliance against two others in their group. Immature animals mostly received defensive support against larger individuals and did not receive support from adults that could lead to a nepotistic dominance system.

Female Activity Profile of a Polygynous Lizard (Anolis Carolinensis): Evidence of Intersexual Asymmetry

Abstract: 1. The activity profile of free-ranging individuals should reflect how females and males are optimizing their respective reproductive efforts. By using the polygynous, sexually dimorphic lizard, Anolis carolinensis, we expected to find an example of pronounced intersexual asymmetry in daily activity patterns. 2. In contrast to males who should focus on blocking consexual access to resident females, we expected females to strategically facilitate egg production by minimizing conspicuous and unnecessary behavior, while feeding frequently from a defended food resource optimal to their needs. 3. During a 56 day period, we made a 90 h record of focal animal observations on 22 unmanipulated, reproductive females; then we compared this activity profile to a known profile for males. We found the following. 4. Females were 1.6 times more stationary (82% of day), moved 1/7th the distance (< 40 m/day), displayed at 1/8th the overall rate (< 14 displays/h), and used < 1/35th the number of displays in non-directed advertisement (1.6 displays/h) as males. 5. Females spent 1/30th the time (0.3% of day) in overt defense of territories 1/9th the volume (8 m3) as males. 6. However, both females and males had equivalent feeding rates (1.2 times/h), suggesting that the energetic needs of female egg production and male territorial maintenance are comparable. 7. The small, lightly defended territories and low feeding rates of females (along with their reptilian metabolism and insectivorous diet) indicate that females have a wide latitude in which to meet their energetic costs. 8. As expected, the proportion of intersexual contacts was similar between female and male profiles. Courtship and copulations occupied 3.2% and 3.9% of the females' day, respectively, with copula averaging 26 min in duration. 9. In a female activity profile which de-emphasized conspicuousness, we found little evidence for a pheromone-based alternative to visual signalling. 10. Predation, as an immediate threat to lizard activities, was not seen during three months of observations. We noted only four instances of avoidance behavior.

Sound production and reproductive ecology of strongly acoustic fish in Africa: Pollimyrus isidori, Mormyridae

Abstract: [We have studied the reproductive ecology and bioacoustic signals of weakly electric mormyrid fish in Africa in order to discover the natural conditions under which acoustic signals are used and to gain insight into the evolution of their acoustic behaviour and hearing. Pollimyrus isidori migrated from a tributary of the Niger River (Mali) into a shallow (2-3 m) flood plain during the onset of the flooding seasons (August, 1991 and 1994). The fish were fully primed for reproduction upon entering the plain, females were significantly larger than males, and the sex ratio was skewed toward males (about 2 males per female). Males established territories (d ~ 1 m) within the roots of floating rafts of grasses, about 0.5 m below the water surface. Males produced conspicuous acoustic displays consisting of Grunts and Moans during the night (130 dB peak re 1 μLPa at approximately 10 cm). These sounds had a fundamental of 340 Hz, but the band-width of the grunt extended to over 3 kHz. Experiments at the field site with captive animals showed that male sound production was stimulated by the presence of conspecific females. The P. isidori repertoire included 3 additional sounds. Analysis of environmental noise showed that these communication sounds fall within a distinct spectral window, thereby minimizing potential interference from other aquatic animals and abiotic noise sources. Waveform analyses showed that the sounds remained coherent over short distances (0.5 m) but lost amplitude more rapidly than would be predicted in a deep water free-field., We have studied the reproductive ecology and bioacoustic signals of weakly electric mormyrid fish in Africa in order to discover the natural conditions under which acoustic signals are used and to gain insight into the evolution of their acoustic behaviour and hearing. Pollimyrus isidori migrated from a tributary of the Niger River (Mali) into a shallow (2-3 m) flood plain during the onset of the flooding seasons (August, 1991 and 1994). The fish were fully primed for reproduction upon entering the plain, females were significantly larger than males, and the sex ratio was skewed toward males (about 2 males per female). Males established territories (d ~ 1 m) within the roots of floating rafts of grasses, about 0.5 m below the water surface. Males produced conspicuous acoustic displays consisting of Grunts and Moans during the night (130 dB peak re 1 μLPa at approximately 10 cm). These sounds had a fundamental of 340 Hz, but the band-width of the grunt extended to over 3 kHz. Experiments at the field site with captive animals showed that male sound production was stimulated by the presence of conspecific females. The P. isidori repertoire included 3 additional sounds. Analysis of environmental noise showed that these communication sounds fall within a distinct spectral window, thereby minimizing potential interference from other aquatic animals and abiotic noise sources. Waveform analyses showed that the sounds remained coherent over short distances (0.5 m) but lost amplitude more rapidly than would be predicted in a deep water free-field.]

The interpretation of animal psychology : Anthropomorphism or behavior reading ?

Abstract: A perennial problem in the study of behavior has been the basis for anthropomorphic psychological terminology. Research has suggested that people use a nonhuman animal's perceived similarity to humans based on physical likeness, familiarity, phylogeny, and/or cultural stereotype to characterize it psychologically. One further hypothesis is that people use an animal's behavior-in-context to determine its psychological characterization. These diverse hypotheses were evaluated by providing undergraduates with narratives depicting mammalian (including human) behavior suggestive of jealousy or deception, and asking them to evaluate their degree of agreement or disagreement with particular psychological characterizations of the animal described. Narratives varied the species, the context in which a mammal's behavior occurred, and how strongly it was emphasized that the narrative was about a nonhuman (or human) organism. Species varied in their physical similarity, phylogenetic closeness or familiarity to humans, and/or cultural stereotype as human-like; behavior remained constant in all narratives. In general, variations in the context in which behavior occurred influenced psychological characterization, but variations in species and emphasis did not: psychological characterizations of all species were almost always similar. Nonscientists (and some scientists as well) apparently use a mammal's behavior-in-context (whether human or not) as evidence of its psychological nature, regardless of the mammal's physical similarity, familiarity, or phylogenetic closeness to humans, or the mammal's cultural stereotype; psychological terms are not used specifically for humans, but rather are depictive of behavior-in-context. Psychological terms set the stage for further investigation into an organism's psychological abilities; calling such terms 'anthropomorphic' inaccurately implies that they are extrapolated from human behavior, when they appear to be applicable to particular behavior-in-context, independent of the species behaving.

Artificial visual obstruction, antipredator vigilance, and predator detection in the thirteen-lined ground squirrel (Spermophilus tridecemlineatus)

Abstract: Antipredator vigilance behaviour is affected by a number of variables, but studies reporting experimental manipulation of visual obstructions are generally lacking in the literature. We examined the individual antipredator behaviour of free-ranging thirteen-lined ground squirrels in 7 city parks in Lincoln, Nebraska, USA as they fed on peanut butter within small plexiglass boxes. Boxes differed in the position and amount of visual occlusion for a squirrel feeding in it: opaque, clear, opaque-sides, and opaque-top (also opaque on the end). We experimentally controlled environmental and contextual variables that have been identified as affecting vigilance behaviour. We filmed 38 ground squirrels as they fed in the boxes, and the results indicate that ground squirrels treat lateral occlusion as functionally identical to complete occlusion. Additionally, there were no significant differences in the squirrels' behaviours in the clear versus the opaque-top box. In 35 approach tests, a person walked toward individual ground squirrels as they foraged in one of the 4 box types. The distance at which the squirrels reacted did not differ among the 4 box types. The results of these two experiments suggest that thirteen-lined ground squirrels compensate for visual occlusion, primarily through increased withdrawals coupled with low-level vigilance postures and that the position of visual occlusion can be of greater importance than the absolute amount of occlusion.

Female Choice of Males in Cuttlefish (Mollusca: Cephalopoda)

Abstract: In captivity, male cuttlefish use visual displays to establish size-based dominance hierarchies and larger males obtain most of the copulations. This experiment was performed to determine if females prefer the larger, more dominant males and whether females use male visual displays to evaluate males. Twenty sexually mature, virgin female cuttlefish were given up to six opportunities to approach one of two males out of a pool of ten adult males, or to approach neither. Females did have significant preferences between males, but they were not related to male dominance. Females showed a consistent and significant preference for the more recently mated male. These preferred males were also more likely to mate again, when given the opportunity, than were less-preferred, less-recently mated males. Females also preferred males that showed fewer zebra displays. Viewing male-male interactions did not affect their choices. Results suggest that female preference could be based on chemical cues, while visual displays may function primarily as agonistic signals. Females who mated did so repeatedly before laying eggs, providing opportunity for sperm competition.

Song Tutoring Influences Female Song Preferences in Domesticated Canaries

Abstract: Laboratory experiments were designed to examine the influence of previous acoustic experience on later song preferences in female domesticated canaries (Serinus canaria). Young females were reared in acoustic isolation (five groups). In these five groups, one was reared without tutoring and four were exposed to taped tutoring songs (playbacks of three different songs, two conspecific and one heterospecific). One of the four tutored groups was exposed to all three songs, while each of the remaining groups was exposed to one of the three songs. When adult, all females were tested using copulation solicitation displays as an index of their song preferences. We demonstrated that females reared without tutoring were especially responsive to a particular domesticated canary song. This song contained a special song phrase type (Vallet & Kreutzer, 1995) that elicits high levels of sexual response. In general, a similar preference was also observed in the groups reared with tutoring. In addition, the females' preferences in tutored groups were also positively and strongly affected by conspecific songs, when these songs had been heard during the previous tutoring. In fact, females seemed to be able to selectively respond to a song containing a special song phrase, but were also able to learn conspecific songs.

Pattern of Movement By Summer Tanagers (Piranga Rubra) During Migratory Stopover: a Telemetry Study

Abstract: How well migratory birds meet en route contingencies depends on their ability to locate resources and avoid sources of stress in an unfamiliar setting. Exploration is a means by which migrants could collect information about the kinds, distribution and abundance of available resources and places safe from predators. We used radio-telemetry to study the movements of 24 summer tanagers (Piranga rubra) during stopover on a barrier island following migration across the Gulf of Mexico. The movement of some individuals was characterized by high linearity and low turn bias (i.e. alternating left and right turns). The combination of left- and right-hand turns while maintaining an overall linear track represents an efficient way of exploring an unfamiliar area. Other summer tanagers restricted their movements to a particular area (e.g. low directionality and high meander ratio), which may reflect less time spent in exploration. Birds that had been on the island for a day and a night displayed a pattern of movement less consistent with exploration than did 'newly arrived' birds. Given pressure to minimize migration time, the time a migrant spends in exploration probably depends on the cost of acquiring information and the benefits to be gained, the ratio of which surely varies among individuals.

Social interactions in two sympatric salamanders: effectiveness of a highly aggressive strategy

Abstract: In terrestrial plethodontid salamanders, aggressive behaviour is thought to function in the spacing of territorial residents among contested cover objects on the forest floor. Such behaviour, when exhibited toward heterospecifics, plays an important role in the competitive interactions between species. We compared levels of aggressive behaviour in intra- and interspecific contexts in two species of sympatric salamanders (Plethodon ouachitae and P. albagula) that have similar ecological requirements but differ in adult size. We also tested the effectiveness of such behaviour in holding cover objects (territorial foci) in the laboratory and on the forest floor. We predicted that if one species were more aggressive than the other, then that species would have greater success in obtaining and holding cover objects. In laboratory trials, residents of P. ouachitae (the smaller species) were extremely aggressive in both intra- and interspecific contexts. Individuals of P ouachitae delivered bites at a rate 14 times that of previously studied species of Plethodon and were significantly more likely to escalate to biting when tested as territorial residents (in intra- and interspecific trials) and as intruders (in interspecific trials). Plethodon albagula exhibited a lower level of aggression, similar to other species of Plethodon. In laboratory trials, in which salamanders competed for cover objects of differing quality, residents of P. ouachitae were effective in expelling conspecific intruders, and they were marginally effective at expelling intruding P. albagula. Residents of P. albagula were less effective in expelling conspecific intruders and did not expel intruding P. ouachitae. We conclude that the extreme aggression exhibited by P. ouachitae enabled it to expel intruders from artificial cover objects and to invade cover objects held by larger heterospecific residents. Field data supported intraspecific defence of cover objects by P. ouachitae, but results for P. albagula were inconclusive. These results are consistent with the geographic distributions of these species (P. ouachitae typically outnumbers P. albagula in the Ouachita Mountains) and provide an example of a behavioural mechanism overcoming a size-related disadvantage.

Reproductive Behaviour of Sea Trout (Salmo Trutta) - the Consequences of Sea-Ranching

Abstract: Reproductive behaviour and factors associated with male and female mating success were studied in sea trout (Salmo trutta) in a stream water aquarium, during three successive years. We compared a sea-ranched and a wild-produced strain, both of the same genetic origin. In general, dominant males courted females more often, spent more time on the spawnable areas, and had higher mating success than lower ranked males. Body mass explained about 18% of the males' position in the dominance hierarchy. Sea-ranched males, however, achieved on average fewer matings than wild ones. Wild males courted the nest-preparing females and chased away other males more frequently than did the sea-ranched males. Females were observed to be aggressive towards males, especially when the females were preparing a nest. The males that were more frequently the target of female aggression had smaller adipose fins and were more often aggressive towards females. In general the females spawned just once in each nest. Sea-ranched females defended and tested their redd less frequently than the wild females did. Digging activity by wild females diminished closer to spawning time, but not that of the sea-ranched females. To what extent the observed differences were due to the environmental conditions or to genetic differences is not known at present. However, the results of previous studies have revealed that behavioural and morphological differences exist between the strains, despite being reared under the same conditions. Thus, the behavioural changes noted in the sea-ranched sea-trout might have a genetic element.

Carib Grackles Imitate Conspecific and Zenaida Dove Tutors

Abstract: In Barbados, Carib grackles (Quiscalus lugubris) forage in opportunistic aggregations that include territorial Zenaida doves (Zenaida aurita) and flocks of conspecifics. In searching for and handling food, grackles use complex beak movements and modulate priority of access with a mixture of postural signals and intra- and interspecific scramble (unaggressive) competition. We show in two experiments that wild-caught grackles learn as readily from a Zenaida dove as they do from a conspecific tutor, whether tutors use similar or different food-finding techniques. Grackles also imitate the technical variant that the hetero- and conspecific tutors were shaped to demonstrate: those who observed a Zenaida dove used the dove's closed beak pecking technique, while those who observed a conspecific used the grackle's open beak pulling, probing or prying. Our findings suggest that imitation, like other forms of social learning, is strongly influenced by a species' foraging ecology. In particular, the ability to imitate novel motor skills should be favored in opportunistic species which exhibit scramble competition and which use complex searching and handling techniques to forage on embedded foods.

The Organisation of Behaviour in Hermit Crabs: Responses To Variation in Stimulus Strength

Abstract: Chemical stimuli were presented to individuals of the hermit crab Diogenes avarus to determine the nature of the interactions between stimuli that elicit conflicting responses. The odour of degraded snail flesh (a signal associated with potential empty shells) elicited an increase in both locomotion and the rate of grasping of gastropod shells. The odour of a visual predator (Matuta lunaris) elicited a cessation of locomotion by the hermit crabs. When snail flesh odour was presented in combination with various strengths of the predator odour (5% to 100%), the responses tended to show a step-function relationship to stimulus strength. Predator inhibition of snail-induced grasping dominated until predator strength was just 5% of full strength odour. However, 5% predator odour alone induced a response similar to full strength predator odour. In the case of locomotion, snail-induced increases predominated no matter what the strength of the predator odour. For both behaviours, responses of hermit crabs tended to be hierarchical rather than graded.

Incomplete Female Knowledge of Male Quality May Explain Variation in Extra-Pair Paternity in Birds

Abstract: We present and discuss an hypothesis to explain inter- and intraspecific variation in levels of extra-pair paternity (EPP) in birds. In species with biparental care, females may be willing to engage in extra-pair copulation (EPC) to improve the genetic quality of the offspring. However, it may be costly to sample males and difficult to assess their genetic quality. Hence, we suggest that variation occurs in the extent of such knowledge between females, causing variation in the extent to which they are willing to engage in EPC. From the hypothesis we present nine predictions on occurrence of EPP in birds, e.g. cuckolders should mainly be resident, close neighbours; rate of EPP should be positively related to breeding density, to rate of male intrusion, to female opportunity to assess male quality from competitive interactions between males, to early arrival time of females relative to time of egg laying, and to breeding synchrony. Finally, we discuss implications on male behaviour. We suggest a new function of male mate guarding, namely that mate guarding is a means to prevent the social mate from obtaining essential information about the quality of potential extra-pair mates.

The importance of different paternity guards in the polygynandrous penduline tit (Remiz pendulinus)

Abstract: It is well documented that extra-pair copulations are a strategy by which males can increase their reproductive success and females may obtain genetic benefits. Whereas in monogamous species extra-pair copulations are the only way for both sexes to increase their reproductive success, in polygamous systems both partners can benefit from mating with several individuals. Here we examine the intensity of sperm competition and the rate of extra-pair fertilizations in relation to male anti-cuckoldry tactics in a small passerine, the polygynandrous penduline tit (Remiz pendulinus), where both sexes have the opportunity to become polygamous. The results revealed rather low rates of extra-pair paternity for this species: 6.9% (14 out of 201) of young being sired by an extra-pair male. Males build elaborate nests to attract females and because of this high initial investment, one would expect males to evolve anti-cuckoldry tactics to ensure paternity. However, male mate guarding intensity as well as within-pair copulation frequency were rather low in comparison to other polygynandrous species, and hence both strategies are unlikely to ensure paternity. In fact our results show that those males which deserted their females early in their fertile cycle (already before the second egg is laid) did not lose paternity, whereas those males which tended to guard their females throughout their whole fertile period were more likely to be cuckolded. Thus, although no obvious anti-cuckoldry tactics exist in this species, extra-pair paternity is very low. This indicates a tendency in females to cooperate with their pair-males rather than seek extra-pair copulations.

Mate Choice and Aerobic Capacity in Red Junglefowl

Abstract: In 'good genes' models of sexual selection, females choose mates whose genes confer increased survival value to offspring. One possible index of male quality is aerobic capacity (the metabolic basis of sustainable exercise), which is likely to be important for fitness. If it is both heritable and ecologically valuable, high aerobic capacity would be a direct signal of male genetic quality. If aerobic capacity is phenotypically plastic but dependent on health, it may provide an indirect index of male quality in other heritable traits (e.g. pathogen resistance). We examined the relationship between courtship behaviour, aerobic capacity (measured as maximum rates of oxygen consumption), and mating success in red junglefowl (Gallus gallus). We also tested the effects of intestinal parasites (the nematode Ascaridia galli) and plasma testosterone levels on aerobic capacity and behaviour. We found no relationship between testosterone and behaviour, mating success, or aerobic capacity. A. galli infection changed the relationship between mass and aerobic capacity; infected males had lower aerobic capacity than uninfected males, but only for small males. Discriminant function analysis suggested that aerobic capacity and display behaviour, together with male ornaments (comb size and colour), were the most important factors determining the mating success of males. However, aerobic capacity and display rate were not strongly correlated, and the manner by which females can discriminate among males with differing aerobic capacity is unclear.

Does Reproductive Synchrony Limit Male Opportunities or Enhance Female Choice for Extra-Pair Paternity?

Abstract: Breeding synchrony has been suggested as one factor that might explain the variation in frequency of extra-pair paternity, both between and within species. Reproductive synchrony might limit the opportunities for males to engage in extra-pair copulations (EPCs), because males face a trade-off with guarding their own fertile partner. Alternatively, breeding synchrony may promote extra-pair paternity, because of reduced male-male competition for EPCs or because of enhanced possibilities for females to assess male quality. In this study, I investigated the influence of synchrony on the occurrence of extra-pair paternity in the blue tit Parus caeruleus. Over four years, breeding synchrony and extra-pair paternity were positively related. Within a season, extra-pair paternity occurred independently of the timing of breeding. The fertile period of the extra-pair male's social mate and that of the extra-pair female often overlapped considerably. However, males who performed EPCs during the fertile period of their social mate were not more likely to lose paternity than males who performed EPCs after the fertile period of their mate. These data suggest that breeding synchrony has little influence on the occurrence of extra-pair paternity in the blue tit.

Song rate correlates with paternal care and survival in willow tits : Advertisement of male quality ?

Abstract: Dawn song in birds may advertise male quality in terms of parental care and/or survival. Males who sing most may also be the best parents, and eager singing may also reflect good chances of a male's or his mate's survival. These relationships were studied in the willow tit Parus montanus, a species with a simple and relatively non-variant song. Song output was expressed as the proportion of time a male spent singing at dawn. Later in the breeding season, two aspects of parental care, nest defence and feeding effort, were measured in the same males. High song output was associated with more intense nest defence behaviour (eager singers attacked the predator model more often and approached closer to it) and high nestling feeding effort. However, reproductive success was not associated with song output, although males with high song rates tended to be more likely to produce recruits. Males who survived to the next year had higher song intensity than males who did not survive, while female survival was not correlated with song output of her mate. The results suggest that dawn song in the willow tit advertises male quality. Some aspects of honest advertisement and female choice are discussed.

An Experimental Study of Cache Recovery By Hoarding Willow Tits After Different Retention Intervals

Abstract: We allowed seven willow tits, Parus montanus, to store and retrieve with retention intervals of 1, 7, 21 and 56 days, in four experimental rooms. Retrieval success decreased over time, indicating a decaying memory for cache locations. Compared to what could be expected by chance, retrieval success was better after all retention intervals. Our results suggest that - after the longer retention intervals - this might depend on preferences for certain types of caching locations rather than memory. If both general and individual preferences are controlled for, birds retrieved significantly better than expected one and seven days after storing, but not later than that.

Vocal-Postural Co-Ordination of a Sexually Dimorphic Display in a Monomorphic Species: the Barbary Dove

Abstract: In the Barbary dove (Streptopelia risoria L.), communication involves visual and vocal signals. In this species, behavioural interaction between sexual partners leads to changes in the reproductive hormonal condition of both sexes. At the beginning of courtship, male doves perform the bowing display. This display is composed of a stereotyped movement pattern (bowing) combined with an acoustic pattern (bow-call). In this paper, we studied the individual temporal patterning of bowing and the bow-call and how they are integrated in the display. The co-ordination between bowing movements and bow-call was analysed using a digital system for the synchronous analysis of acoustic-visual signals. Bow-calls differ between individuals in both temporal and frequency characteristics, and in their repetition rate. The bowing movements do not differ between individuals in their temporal structure but the repetition rate is individually different. The repetition rates of the vocal and postural motor patterns are highly correlated. However, the two signals are not synchronised and the phase delay between them is individually different. We suggest that in the bowing display the gender and the identity are signalled respectively by the bowing pattern and the bow-call. The integration of the two signals generates a third signal, the integrated bowing display rate. The role of the three signals during male-male encounters and during courtship behaviour is discussed.