Showing papers in "Behaviour in 1992"

Sex Differences in Patterns of Association Among Indian Ocean Bottlenose Dolphins

Abstract: Patterns of association among bottlenose dolphins resident in Shark Bay, Western Australia were analyzed using party membership data. Parties contained an average of 4.8 individuals, but party size and composition were unstable. While these temporary parties often contained both males and females, long term consistent associations generally were between members of the same sex. The highest association coefficients, resulting from very frequent co-occurrence within parties were between males and between mothers and offspring. Males formed subgroups of two or three individuals who consistently associated with each other, and these were stable over periods of at least seven years in some cases. Male subgroups preferentially associated with particular other male subgroups. Females associated most consistently with other females, although not to the same extent as some males. Female associations were better described as a network rather than discrete subgroups. Male-female associations were generally inconsistent and depended in part on female reproductive state. Mothers and their offspring associated very consistently for at least 4 years.

Animal Grouping for Protection From Parasites: Selfish Herd and Encounter-Dilution Effects

Abstract: Grouping has been widely accepted as a mechanism for protection from predation. Just as has been apparent with predation, there is now ample evidence that parasites (biting flies, warble flies and parasitoids) can impact an animal's individual fitness. Some aspects of grouping, namely an encounter-dilution effect and the selfish herd effect, appear to apply as much to protection of animals from flying parasites as protection from predators. The encounter-dilution effect provides protection when the probability of detection of a group does not increase in proportion to an increase in group size (the encounter effect), provided that the parasites do not offset the encounter effect by attacking more members of the group (the dilution effect). The selfish herd effect provides protection from flying parasites to animals that are in the center of a group or more closely placed to other animals. Most of the quantitative evidence for the protection from flying parasites from grouping comes from studies on ungulates. Further investigation of these effects among a variety of taxa is needed for a full appreciation of the role of parasites in animal grouping and sociality.

Avian Movement Imitation and a New Form of Mimicry: Tracing the Evolution of a Complex Form of Learning

Abstract: [1. The spontaneous imitation of movements, previously known in two orders of mammals, is demonstrated in a psittacine bird. 2. The animal, a Grey parrot which has bonded to humans, utilizes its torso, legs, wings, head, beak, and tongue in the imitation of human movements. 3. A new form of imitation, ''non-vocal mimicry,'' is tentatively identified. It is defined by the use of skeletal movements to produce mimetic sounds. 4. Hierarchical relationships and phylogenetic patterns of occurrence suggest that imitative learning in birds may have evolved through the sequence: song/call learning → vocal mimicry → non-vocal mimicry→ movement imitation. 5. These relationships and patterns, and possible differences in function and incubation time, suggest that movement imitation in birds is not homologous to that in mammals., 1. The spontaneous imitation of movements, previously known in two orders of mammals, is demonstrated in a psittacine bird. 2. The animal, a Grey parrot which has bonded to humans, utilizes its torso, legs, wings, head, beak, and tongue in the imitation of human movements. 3. A new form of imitation, ''non-vocal mimicry,'' is tentatively identified. It is defined by the use of skeletal movements to produce mimetic sounds. 4. Hierarchical relationships and phylogenetic patterns of occurrence suggest that imitative learning in birds may have evolved through the sequence: song/call learning → vocal mimicry → non-vocal mimicry→ movement imitation. 5. These relationships and patterns, and possible differences in function and incubation time, suggest that movement imitation in birds is not homologous to that in mammals.]

Delayed breeding in avian social systems: the role of territory quality and "floater" tactics

Abstract: Summary In many avian societies, young birds delay breeding beyond the age of sexual maturity. Most previous hypotheses of delayed breeding have emphasized forces that keep young birds from becoming breeders. We develop a model of delayed breeding which includes the future acquisition of a high quality territory as a potential direct benefit of delayed breeding. Strong differences in territory quality, age-correlated asymmetries in resource holding potential, and territory site tenacity set the stage for young birds to either breed immediately on a poor territory, or obtain a high quality territory through reproductive delay on or near the site. A wide variety of species and social organizations reveal common patterns of breeding status acquisition through behaviours as nonbreeders with site tenacity on or immediately near the breeding site. A review of 'floater' strategies reveals that nonbreeders frequently have restricted home ranges that encompass one or more breeding territories, and prior experience at a site improves their chances of acquiring a territory in future years. This pattern of territory acquisition argues for incorporating direct benefits into models of delayed breeding. We discuss the potential applications to understanding delayed breeding in social systems as apparently different as cooperatively-breeding birds, migratory passerines, colonial breeding gulls, and lek-breeding grouse and manakins.

Composition and Dynamics of Humpback Whale Competitive Groups in the West Indies

Abstract: It has been hypothesized that humpback whale, Megaptera novaeangliae, competitive groups represent intrasexual competition by males for access to a mature female The composition and dynamics of these groups was studied between 1989 and 1991 in Samana Bay, West Indies The sex of group participants was determined by molecular analysis of skin biopsies Groups showed similar characteristics of size and movement as those described from other breeding areas, except that only one group contained a calf The sex was determined of 141 participants in 44 competitive groups In 21 of these groups, we were able to biopsy all participants No group contained more than one female, but seven of the wholly sampled groups (all of them small) consisted entirely of males Of 22 animals who were ''positively'' assigned the role of Nuclear Animal, 17 were female, and five were male Similarly, of 24 biopsied Principal Escorts, 23 were male and one female All 24 biopsied Challengers were male Of 55 animals who were either classified as Secondary Escort, or whose role could not be categorized, 51 were male and four female In 8 cases, associated pairs of males exhibiting no aggression towards each other were observed to either enter or leave a competitive group together Of 16 individuals resighted on more than one day, all but one were males These data suggest that: 1 While most groups (as predicted) represent male-male competition for a single female, observers should be cautious in their assumptions; 2 All-male groups may represent dominance sorting by unfamiliar conspecifics; 3 Females may occasionally aggressively repel advances by unwanted males; 4 While unlikely in light of present knowledge, the possibility that males form coalitions cannot be dismissed We suggest that competitive groups may be asymmetrical contests in which a female Nuclear Animal is of more value to the Principal Escort than to a Challenger, particularly if the former's defence of her represents mate-guarding

Song Function in Gibbons

Abstract: This paper examines variation in the singing behaviour of male and female gibbons in an attempt to construct a consistent framework to describe the function of both solo and duet song bouts. Functional hypotheses are described and tested with the available data. The song bouts of mated females are shown to be strongly associated with the pressure of territorial defence. Conversely, the solo song bouts of mated males show no relationship with territorial behaviour, but are associated with the (estimated) density of floating unmated males in the population. In accordance with the hypotheses under test, these results indicate that mated females sing to defend their territories, whilst mated males sing to repel males in defence of their mate and offspring. Contrary to previous hypotheses, the production of coordinated duets by male and female pairs is found to be unrelated to pairbonding. However, duetting is shown to be associated with encounters and aggression at the territorial boundary, in support of the claim that duetting advertises pairbond presence in order to intimidate neighbours and reduce the costs of territorial conflicts. The implications of these analyses for territorial and mating strategies in gibbons are discussed.

Mother-Offspring Separation and Acoustic Stereotypy: a Comparison of Call Morphology in Two Species of Pinnipeds

Abstract: I have compared structural variation of the primary vocalizations used between mother-offspring pairs in two species of pinnipeds that differ fundamentally in their breeding behaviour: northern elephant seal (Mirounga angustirostris) mothers and offspring normally are together throughout the nursing period; northern fur seal (Callorhinus ursinus) females regularly separate from their offspring while nursing. Two predictions were tested: (1) these vocalizations should be individually-distinct (stereotyped) in females and pups of both species if they serve to function for recognition, and (2) because individuality should be more pronounced in a species where separations and reunions are common, the vocalizations used between northern fur seal mother-offspring pairs should be more individually-stereotyped than those of the northern elephant seal. Principal components analyses revealed structural differences between the calls of females and pups in both species. Analysis of variance showed the calls of individual seals to be acoustically distinct in all cases. The calls used between mother-offspring pairs of northern fur seals were more stereotyped than those of northern elephant seals. These calls had less within-individual variation, greater among-individual variation and were more often correctly predicted in discriminant analyses. The results indicate that selective pressure to develop vocal recognition exists in both species but is greater in the northern fur seal.

Influence of Male Competition and Female Mate Choice On Male Mating Success in Barbary Macaques (Macaca Sylvanus)

Abstract: To evaluate the importance of male competition and female mate choice for male mating success in Barbary macaques, focal female observations during the conceptional estrus were conducted in a large semifree-ranging group. Analysis of sexual behaviour included 121.7 h of observation of 19 focal females. In addition, ad libitum recorded male agonistic interactions, occurring in the vicinity of the focal females, were analyzed. Both sexes initiated sexual associations, and females were found almost always in contact (within 2 m) with a male. Most matings took place within 1 min after contact establishment, and the proportion of these quick matings was especially high for subadult males, which mainly "sneaked" copulations during moments of distraction of adult males. Mating contacts were longer than non-mating contacts, and varied in duration from a few seconds to more than 2 hours. Mating contacts with adult males did not differ in length with respect of the initiating sex. Females were considerably more active in terminating than initiating contacts. Females mated, on average, once every 30 min, and had 1-10 different partners (out of 37 sexually mature males) during a 4 h observation session. Females mated with 40-100% of their contact partners. An absence of mating with specific males was due to interference by other males, improper timing of contact, or (temporary) lack of attractivity of the female rather than related with a rejection of these males in almost all cases. Similarly, a highly significant positive correlation between mating frequency of a male and time spent in the vicinity of the focal females revealed that females did not discriminate among potential mates, and, hence, did not exercise mate choice. The majority of matings (71 %) were accumulated by 7 out of the 9 oldest males and additionally 2 young adults. One indicator for sexual competition among males was the peak of male injuries during the mating season. Aggressive interactions between adult and subadult males, indicating a clear-cut dominance of the adults, occurred frequently, while dyadic agonistic interactions between adult males were rare and inconsistent. The available data indicated age-inversed rank relations and were not predictive for mating success. A highly significant positive correlation was, however, found between male mating success and the participation as ally in polyadic agonistic interactions. The oldest males gave and received most support and were rarely victims of coalitions while the reverse was found for young adult males. All males followed an "age rule", after which the older of 2 males was supported during a conflict. Consequently, male power asymmetry in polyadic conflicts ran counter that in dyadic situations, and could change quickly depending on the presence of potential allies. Chances for dyadic solutions of conflicts were rare on the ground where most estrous females and the old males spent their time. Although females did not reject potential mates, they nevertheless influenced male mating success by inciting male competition. Females often tried to contact a new partner after a mating, thereby actively putting both males into conflict. The creation of such encounters was possible only between males with low power asymmetry, and only males which got successfully through these frequent female-initiated tests of their power had a high mating success. Incitation of male competition was discussed as a female mating tactic in species with a high sexual dimorphism. Compared with other macaques, the Barbary macaque belongs to such species.

'Food' Calls Produced By Adult Female Rhesus (Macaca Mulatta) and Japanese (M. Fuscata) Macaques, Their Normally-Raised Offspring, and Offspring Cross-Fostered Between Species

Abstract: We tested a recent claim that rhesus and Japanese macaque offspring cross-fostered between species exhibit vocal learning by producing 'food' calls typical of their adoptive rather than their genetic species (MASATAKA & FUJITA, 1989). Our study population consisted of four groups of socially-reared animals housed outdoors - two of each species. Food calls produced by adult female rhesus and Japanese macaques did not differ at the species level, although individual differences were clearly present. Food calls produced by normally raised offspring differed both between individuals and between species. In spite of statistically significant differences, however, immatures in the two species still showed substantial overlap on every acoustic feature that was measured. Evidence from four cross-fostered offspring was equivocal. Two rhesus macaques raised in Japanese macaque social groups produced calls that were typical of their own species. Some measurements from calls produced by two cross-fostered Japanese macaques fell closer to mean values for normal rhesus than for those of their own species. However, these measurements were still within the observed range of variation shown by normally raised Japanese macaques. We conclude that food calling behavior of cross-fostered Japanese macaques may have shown modification, but that any such effect was not based on a species-specific adult model. Given the variability of these sounds and the lack of species differences in adult female vocalizations, food calls do not present a good opportunity to test for vocal learning in cross-fostered rhesus and Japanese macaques.

Reactions of Four Passerine Species To Threats of Predation and Cowbird Parasitism: Enemy Recognition or Generalized Responses?

Abstract: Four host species of the parasitic brown-headed cowbird (Molothrus ater) were exposed to taxidermic mounts of a female cowbird, fox sparrow (Passerella iliaca), and common grackle (Quiscalus quiscula) at their nests during their egg-laying or nestling stage. Red-winged blackbirds (Agelaius phoeniceus), a species that accepts cowbird eggs laid in their nests, responded more aggressively to cowbird models early in their nesting cycle, indicating that they recognized the unique threat the cowbird posed. Gray catbirds (Dumetella carolinensis), northern orioles (Icterus galbula), and cedar waxwings (Bombycilla cedrorum) can remove cowbird eggs from their nests and for the most part they responded similarly to cowbird models and the "nonthreatening control," i.e. a fox sparrow. Cedar waxwings were nonaggressive to all the models and may rely on concealment to protect their nests from enemies. Removal of cowbird eggs by puncture ejection is more risky than grasp ejection. Despite this, orioles and waxwings (puncture ejectors) were not significantly more aggressive to cowbird models at egg laying than catbirds (grasp ejectors). Responses of the three rejector species toward the cowbird model did not change over the nesting cycle, indicating further that they do not recognize cowbirds as a unique threat. Rejector species may not recognize cowbirds because they have little experience with them. With the exception of waxwings, all of the hosts recognized the grackle as an enemy and increased their levels of defence from the laying to nestling stages. Three of the host-species did not simply respond in a generalized manner to any intruder at their nests but indeed recognized specific enemies. Considerable interspecific variability exists amongst the four species in defensive behaviours, which may reflect their different nesting habitats.

Seafinding By Hatchling Sea Turtles: Role of Brightness, Silhouette and Beach Slope as Orientation Cues

Abstract: Upon emerging from underground nests, sea turtle hatchlings immediately crawl toward the ocean. The primary cues used in orientation are visual but the nature of the visual cues was a matter of speculation. Hatchlings might also respond to secondary cues, such as beach slope. Experiments were carried out in an arena where specific visual and slope cues, simulating those present at nest sites, could be precisely controlled and manipulated. Subjects were green turtle (Chelonia mydas L.) and loggerhead (Caretta caretta L.) hatchlings. Both species oriented toward the more intensely illuminated sections of the arena. They also oriented away from dark silhouettes which simulated an elevated horizon, typical of the view toward land. Turtles responded primarily to stimuli (both silhouettes and photic differences) at or near eye level. When presented simultaneously with a silhouette and a photic gradient located in different directions, hatchlings oriented away from the silhouette and ignored photic stimuli. Under infrared light, both species oriented down slopes. However in the presence of nocturnal levels of visible light loggerheads ignored slope cues and responses of green turtles to slope were weakened. The data suggest that loggerhead and green turtle hatchlings usually find the sea by orienting away from elevated silhouettes. This is a prominent and reliable cue for species which typically nest on continental beaches.

Memory Does Not Constrain Individual Recognition in a Bird With Song Repertoires

Abstract: Summary We tested the hypothesis that memory or perceptual limitations imposed by song repertoires contrain the ability of song birds to recognize their neighbours by song. Using operant conditioning procedures, we trained male song sparrows (Melospiza melodia) (median repertoire size = 8) to discriminate between two artificial song sparrow repertoires of 32 songs each (64 songs total). Both song sparrows learned to discriminate concurrently between all 32 song pairs. The birds learned later songs as quickly as they learned earlier songs. These results suggest that song sparrows are capable of memorizing the full song repertoire of their neighbours under natural conditions. In a second experiment we found that song sparrows readily generalize from one exemplar of a song type to other variations of that song type. We conclude that the evolution of song repertoires of song sparrows have neither constrained nor been constrained by individual recognition of neighbours by song.

Song Features Essential for Species Discrimination and Behaviour Assessment By Male Blackbirds (Turdus Merula)

Abstract: The present study tested the signal value of different parameters of the blackbird song by comparing territory owner's responses to unmodified motif parts. Parameters were modified with reference to their natural limits of variation which were known a priori for some of the parameters. Those for the frequency of occurrence of the three types of motif sound figures (unmodulated and/or complex toned FM-figures, and compound MIX-figures composed of pieces of both the CF- and the FM-type) and their modulations, and the relative sound pressure (SP) of their harmonics, were determined in this study. The following results were obtained: The frequency of occurrence of the sound figure types is essential for species discrimination in the sense that motif parts must contain CF-pieces with a relatively constant frequency (either as CF-figures or as parts of MIX-figures), and it communicates additional information: a high proportion of FM-figures giving a gurgling sound character communicates a high arousal and vice versa. The ratio of SP of the fundamental to that of the 1 st and the 2nd overtone is also essential for species discrimination. The ratio must be greater than about 1:0.2:0.2 making the motif parts relatively pure toned. Above this value the SP ratio may communicate additional information: a relatively low ratio giving a hoarse sound character seems to represent a high arousal and vice versa. Also, a high sound pressure level of the motif parts communicates a high arousal and vice versa. Neither the order of sound figures, nor the specific variation across the motif part of the sound figures' frequency level, duration and amplitude is essential for species discrimination. So is, however, a certain variation per se of each of the three features across the motif part. The results fit in with the 'room for variation hypothesis' on the principles of coding information into bird song. Thus the species-essential parameters seem to be 'tuned' to their natural limits of variation in the sense that species discrimination ceases when they are changed beyond these limits; within these limits some of them convey additional behavioural information; and they include all sorts of parameters, e.g. basic as well as higher order syntactical and sound type parameters, and invariant as well as variable ones.

Individual Variation and Alternative Patterns of Foraging Movements in Recently-Emerged Brook Charr (Salvelinus Fontinalis)

Abstract: Recently-emerged juvenile brook charr foraging in relatively homogeneous, clear, still-water pools displayed significant interindividual variation in the proportion of search time spent moving, the average speed during search, the average speed during periods of moving search, and the distance moved during pursuit of prey. The frequency distribution for interindividual variation in the proportion of time spent moving was bimodal, but distributions for the other movement parameters were not. Thus, in the field, young charr tended to specialize at one of two alternative movement patterns differing primarily in the proportion of time spent moving. The movement parameters were all positively correlated, but correlations between the proportion of time spent moving, the speed while moving, and pursuit distance were small enough (r2's < 0.30) to suggest that different aspects of search mode may vary relatively independently. Our findings have three implications for studies of search mode. First, intraspecific variation in search mode need not be only a response to environmental change, but can occur in the same environment at the same time. Second, frequency distributions of movement parameters offer a more objective base than do arbitrary classifications for determining how many types of foragers are present. Third, studies using different movement parameters to distinguish between alternative search modes (e.g. sitting-and-waiting and actively searching) may not be directly comparable.

The reproductive behaviour of α-, β-, and γ-male morphs in Paracerceis sculpta, a marine isopod crustacean

Abstract: [Males occur as three distinct morphotypes in Paracerceis sculpta, a marine isopod inhabiting the Gulf of California. Alpha-males are largest in body size (x ± SD = 6.55 ± 0.72mm, N = 63) and defend breeding sites in intertidal sponges. Beta-males are smaller (x ± SD = 4.34 ± 0.43 mm, N = 59) and resemble sexually receptive females in behaviour and body form. Gamma-males are tiny (x ± SD = 2.65 ± 0.73 mm, N = 23) and are capable of rapid movements. All three male morphs are sexually mature and successfully sire young in the field (SHUSTER, 1989a). Using artificial sponges to simulate natural breeding habitats, I examined (a) competitive interactions among α-males for access to breeding sites and sexually receptive females, (b) behaviours used by β- and y-males to enter spongocoels, and (c) the tendency for β- and γ-males to discriminate breeding site quality in terms of the availability of sexually receptive females. I found that: 1. Resident and intruder α-males used their walking legs, uropods and body positioning to retain or gain access to breeding sites. 2. Intruders were consistently more aggressive than residents in contests, except when breeding sites containing sexually receptive females were limited. 3. Despite their relative quiescence, residents retained their spongocoels in most contests, apparently due to the positional advantage residents gain when situated in the spongocoel. 4. When interacting with α-males, β-mates imitated female courtship behaviour, and, Males occur as three distinct morphotypes in Paracerceis sculpta, a marine isopod inhabiting the Gulf of California. Alpha-males are largest in body size (x ± SD = 6.55 ± 0.72mm, N = 63) and defend breeding sites in intertidal sponges. Beta-males are smaller (x ± SD = 4.34 ± 0.43 mm, N = 59) and resemble sexually receptive females in behaviour and body form. Gamma-males are tiny (x ± SD = 2.65 ± 0.73 mm, N = 23) and are capable of rapid movements. All three male morphs are sexually mature and successfully sire young in the field (SHUSTER, 1989a). Using artificial sponges to simulate natural breeding habitats, I examined (a) competitive interactions among α-males for access to breeding sites and sexually receptive females, (b) behaviours used by β- and y-males to enter spongocoels, and (c) the tendency for β- and γ-males to discriminate breeding site quality in terms of the availability of sexually receptive females. I found that: 1. Resident and intruder α-males used their walking legs, uropods and body positioning to retain or gain access to breeding sites. 2. Intruders were consistently more aggressive than residents in contests, except when breeding sites containing sexually receptive females were limited. 3. Despite their relative quiescence, residents retained their spongocoels in most contests, apparently due to the positional advantage residents gain when situated in the spongocoel. 4. When interacting with α-males, β-mates imitated female courtship behaviour, and]

Clans and Harems in a Colony of Hamadryas and Hybrid Baboons: Male Kinship, Familiarity and the Formation of Brother-Teams

Abstract: Three features of the hamadryas society, Papio hamadryas, which are quite unique among Old World monkeys, are its multileveled structure (i.e. harems, clans, bands, troop), the reported pattern of female dispersal (i.e. males tend to remain in their natal clans whereas females tend to move between clans and bands), and the special bonds that develop between adult males. It has also been hypothesized that the males of a clan are genetically related. In this paper a causal approach is adopted in order to investigate the proximate factors which can account for the structure/dynamics of socio-spatial group organization observed over two years in a large colony of hamadryas and hybrid baboons housed in an outdoor enclosure in the Madrid Zoo, containing 18 adult males with known kin relations. I first examined the types of grouping observed in the colony and the alternative social strategies used by the different male individuals during their ontogenetic trajectories for acquiring, and maintaining, females. Since the hamadryas baboon is considered a female-transfer species, I studied whether the sex that stays, that is, the males, developed some kind of mutual affiliative relationship, as one would predict, and whether their inter-male bonding preferences were based on genetic relatedness or on familiarity (i.e. sharing the same developmental environment during socialization).

Frequent copulations despite low sperm competition in white storks (ciconia ciconia)

Abstract: White Storks Ciconia ciconia paired for ca. 30 days before laying a clutch. During this period, mates copulated frequently (160 copulations/pair; 0.4 copulations/daylight h), but copulation rate was drastically reduced a week before laying of the eggs. Both fewer copulation attempts by males and lower female receptivity accounted for this reduction. This pattern was the same regardless of whether pairs nested solitarily or in colonies. Colonial as well as solitary males spent more time at the nest before egg-laying while the opposite trend was found for females. Consequently, females were more likely to remain alone at their nests while ovulating. Colonial birds had ample opportunities for engaging in extra-pair copulations (EPC) during the female fertile period, but these were very infrequent (0.4% of all successful copulations) and involved recently-paired birds exclusively. This suggests that sperm competition in this species is of little relevance for explaining patterns of pair copulations. Accordingly, males did not guard their female mate and the timing of copulation was poorly tuned to chances of fertilizing the female's eggs. However, it remains to be explained why storks copulated so much and for a prolonged period when the risk of EPC was so low. It is suggested that copulations may be part of a signalling system by which males advertise and females assess the physical condition of the male, which is likely to correlate with the ability of males to forage efficiently for them and their offspring. In support of this possibility, males who copulated frequently fed chicks at a higher rate during the nestling period.

Inherited Population Differences in Avoidance Conditioning in Three-Spined Sticklebacks, Gasterosteus Aculeatus

Abstract: Laboratory-reared predator-naive three-spined sticklebacks from two sites, one with abundant predatory fish (the high-risk site) and the other essentially predator-free (the low-risk site), were given a passive avoidance conditioning task in which they received a simulated attack from a model avian predator whenever they entered a previously-favoured feeding patch. 15/16 fish learned to avoid the dangerous patch within 15 days, but those from the high-risk site did so significantly faster and received fewer attacks in the process. The two categories of fish did not differ either in active avoidance of the attack stimulus or in the rate at which they started to re-exploit the dangerous patch once negative reinforcement ceased. It is argued that fish from high- and low-risk sites differ in the negatively reinforcing properties of the same, standardised attack.

Variable Leadership in Bar-Headed Geese (Anser Indicus) : an Analysis of Pair and Family Departures

Abstract: This paper reports quantitative leadership differences in semi-captive bar-headed geese (Anser indicus) at different times of the year, and in different types of groups. Leading is defined here as causing the departure or determining the direction of movement of the whole group. No permanent and exclusive leader of a pair or family group was found, rather relative leading frequencies of male, female and young showed a definite shifting pattern. Females led more often than their mates prior to breeding, and on nest pauses during the incubation period, but less often in summer, autumn and early winter. In families there was no difference between the frequencies of male and female leading. Family females led relatively more often than those of pairs without offspring. This difference was related to the presence, not the number, of young. Goslings led the family about as often as the parents during the rearing period in early summer, less often in autumn, winter and next spring. Such differences and changes are to be expected where competence in particular tasks and dependence on partners vary between group members, and where different situations require different abilities. For the geese, the results can be related to the different options of group members and to the different benefits they derive from leaving (or 'staying put') or following (or waiting for the others) in different situations.

The Ontogeny of Food-Storing and Retrieval in Marsh Tits

Abstract: Marsh tits, Parus palustris, store food and rely on an accurate spatial memory to retrieve their caches. This study considers the ontogeny of storing and the spatial memory involved in retrieving these caches in juvenile hand-raised marsh tits. Preliminary work showed that these birds began storing and retrieving their caches around the time of feeding independence, suggesting that juveniles do not need to learn from adults. However, storing gradually improved over the first few trials, in terms of the appropriateness of items stored, the efficiency of choosing suitable storage sites and the rate of storing seeds. To answer the question of whether the behavioural improvement is a function of age, experience or both, the retrieval performance of two groups of birds were compared. During the first eight trials (24 days) after nutritional independence from the parents, the two groups were exposed to two different kinds of experience: experienced birds were provided with seeds which they could store and retrieve two hours later, whereas the naive birds were exposed only to the storage sites but they could not store. In the following eight trials, both groups were allowed to store and retrieve their caches. If the improvement was merely a consequence of age (maturation) no difference should be found between the two groups on trial 9. In contrast, if improvement was purely a function of experience then the pattern of improvement in the naive group should follow that of the experienced group, but showing an eight-trial time lag. The results suggested a pattern intermediate between these extremes, indicating that either the development of food-storing was a function of both age and experience or that other differences between the two groups, such as differences in motivation to store and/or experience at handling seeds, were important. In contrast, retrieval performance was better than expected by chance on the first trial it occurred and showed little, if any, improvement.

Monogamy in the european starling

Abstract: Recent theoretical and experimental studies appear to provide a comprehensive explanation for the evolutionary, and short-term, stability of biparental care in birds. However, much of the intraspecific variation in the absolute and relative contribution by the male and female remains to be explained. Most studies of the natural variation across pairs reveal positive correlations between the level of male and female nest defence or brood provisioning, but some species show negative relations, or between-season variability in the direction of the relationship. This study examines the determinants of male and female provisioning rate in monogamous European starlings (Sturnus vulgaris), in terms of the patterns of male display, pairing patterns, laying phenology and clutch attributes. There was assortative pairing by body size and, controlling for female body size, larger males attracted relatively fecund mates. Males that sang relatively more, controlling for these body size effects, were paired with females that laid earlier. Female nest provisioning rates to experimentally standardized broods were positively correlated with female size, but male provisioning rates were unrelated to either song or any other attributes of themselves or their mates.

The effects of a trade-off between foraging and brood defense on parental behaviour in the convict cichlid fish, cichlasoma nigrofasciatum

Abstract: Parental convict cichlids, Cichlasoma nigrofasciatum, responded to the presence of a potential brood predator by decreasing net energy gains (food intake decreased and energy expenditure increased) while increasing parental effort (large allocation of time to brood defense). These behaviours are important factors in the life-history trade-off between current and future reproductive investments. The allocation of energy into defense behaviours and elevated activity levels, combined with a voluntary reduction of food consumption, represent an investment in the current brood which could (in nature) reduce future reproduction. Contrary to parental investment theory predictions, consistent increases in parental effort with brood age were not evident.

Consequences of joint-territoriality in a mixed-species group of tamarin monkeys

Abstract: Groups of saddle-back (Saguinus fuscicollis) as moustached tamarins (Saguinus mystax) in a western Amazonian forest jointly defended home ranges larger than 100 ha, which were held in common throughout the year. Resources were defended by direct exploitation in extensive areas shared with other groups, or through intensive and frequent intergroup interactions along territorial boundaries. These interactions were expressed primarily during intergroup encounters, and affected the use of space, movements, time budget, and foraging success of tamarins. During encounters, animals of both species spent more time in energetically costly activities, such as rapid travel and intergroup chases, and less time in energetically positive activities, such as feeding and foraging. In addition, foraging success per unit of foraging effort within overlapping areas of the range periphery was lower than in exclusive areas of the range centre, particularly for saddle-back tamarins. The time and energy allocated by moustached tamarins to boundary contests was considerably greater than that of saddle-backs, despite the fact that only the latter species increased its foraging efficiency by shifting from exclusive areas in the group's range to those shared by other groups. This is probably because of saddle-back's greater use of depletable food supplies, such as small fruit patches and small microhabitats containing embedded prey items. These benefits are likely to justify the substantial amount of time and energy invested in territorial defence for both saddle-backs and moustached tamarins, but appeared to be highly asymmetric between species.

The Development of a Behavior System: Dustbathing in the Burmese Red Junglefowl. Iii. Effects of Experience On Stimulus Preference

Abstract: Two experiments were designed to study the development of the perceptual mechanism that recognizes dust. We examined the effects of early experience with a variety of substrates on the choice of a substrate for dustbathing. In the first experiment, chicks were given experience with one substrate: black or white sand or a skin of junglefowl feathers. In a choice test, there was an overwhelming preference for the black sand both as a dustbathing and a pecking substrate, regardless of early experience. Nonetheless, some of the birds exposed to white sand or feathers as the training stimulus did become entrained to dustbathe on these substrates. In the second experiment, chicks were given equal experience with each of four substrates: white, normal, and dark sand, and sawdust. In the choice tests, the birds dustbathed in the substrates in the same proportion that they dustbathed during training when only one stimulus was available at a time. The birds preferred to dustbathe in the normal sand, but preferred to peck at sawdust. The experiments show that both the stimulus properties of a substrate and the kind of experience a bird has dustbathing in a substrate determine whether a bird develops a tendency to find that substrate suitable for dustbathing.

Influence of Prey Movement On the Performance of Simple Detours By Jumping Spiders

Abstract: The influence of prey movement on the performance of simple detours by salticids was investigated. Seven species were studied. Two subject species, Portia fimbriata and Portia labiata, are specialized web-invading species that eat other spiders. The other five species investigated (Euryattus sp., Euophrys parvula, Marpissa marina, Trite auricoma and Trite planiceps) are more typical cursorial hunters of insects. We provide evidence that: 1) salticids will initiate detours toward motionless prey; 2) salticids are more inclined to initiate detours toward moving than toward motionless prey; 3) salticids tend to complete detours even when prey that had been moving at the start remains stationary during the detour; 4) prey movement makes the salticid more likely to stalk and attack when prey is only a few centimetres away and in a position from which it can be reached by a straightline pursuit; 5) Portia is more inclined than the other salticids to initiate detours to motionless prey, then to stalk and attack motionless prey when close, than the other salticids are. Mechanisms that might account for Portia being different from the other salticids are discussed.

Optimal Foraging in Peromyscus Polionotus: the Influence of Item-Size and Predation Risk

Abstract: Predictions of optimal foraging theory were tested for Peromyscus polionotus in the laboratory and in two field experiments in which seed item-size was manipulated. In the laboratory, handling times for millet, sunflower seeds, and peanuts were determined. Additionally, energy/handling (E/h) time values were calculated and seed preference experiments were conducted. Mice showed a clear preference for the seeds more profitable in terms of E/h. Seed preference experiments were also conducted in the field to determine the relative influence of optimal foraging and predation risk in diet choice. In the first of the two field experiments, behavioral strategies to reduce predation vulnerability could not influence differential seed selection. As predicted, the mice again showed a preference for the more profitable seed type. In the second experiment, animals were presented with conflicting demands because foraging on a more abundant, but less preferred, seed type afforded the animal an increased ability to avoid predators. Presented with this opportunity to reduce the risk of predation, the animals shifted their preference to the safer, but less profitable food. This shift in seed preference was accompanied by predation-risk-reducing changes in spatial foraging patterns.

Correlates of Agonistic Display By Great Tits Parus Major

Abstract: This study examined physical and social correlates of agonistic display performance by wild great tits Parus major competing over food and territorial space. All behavioural data were collected at winter feeding stations from individually colour-ringed birds for which data on physical characteristics, current social status and individual history were available. At feeders, competitive interactions between males were more frequent than those involving females, and birds not present in previous winters (mostly first-winter birds) interacted more frequently than prior residents (locally territorial adults). Interactions away from food sources usually involved at least one male, increased in frequency over the course of the winter, and often involved chasing of one bird by another. These interactions are thought to reflect competition for territorial space. Males were almost always dominant over females in competitive interactions. Simple supplants were most frequent in intersexual interactions, with display being more often seen in interactions between birds of the same sex. In intrasexual interactions, there were no consistent differences between the sexes in frequency of use of displays, but there was a general trend for postural display elements to be performed more often by eventual dominants than by eventual subordinates. Displays based on 'head-up' tended to be performed by prior resident, locally dominant, territorial males. Their incidence increased over the course of the winter, and they were especially associated with non-feeder interactions. Displays based on 'wings-out' and 'tail-fanning' were associated with non-territorial, first-year birds that were less frequently occurring at the study site, and tended to occur in cases where the opponents had little prior experience of each other. Displays based on head up were performed almost exclusively in intraspecific interactions, whereas those based on wings out and tail fanning were also common in contests over food with blue P. caeruleus and coal tits P. ater, in which the great tit was usually dominant.

Individual recognition of nestling distress screams by european starlings (sturnus vulgaris)

Abstract: Individual recognition of nestling distress screams by European starlings (Sturnus vulgaris) was assessed by comparing the responses of free-living parents to playbacks of screams recorded from their own young or from neighbouring chicks. Individual variation in the acoustic structure of distress screams was analysed to assess whether they were likely to afford an acoustic basis for individual recognition. Parents hearing screams of their own young were significantly more likely to make diving attacks on the speaker than parents hearing the screams of neighbouring chicks. Thus nestling screams appear to function as individually indentifiable calls for aid. Multivariate analysis of variance employing 9 acoustic parameters of nestling screams revealed significant differences among groups of screams recorded from different chicks, suggesting that screams could afford a suitable basis for individual recognition. Post-hoc F-tests suggest that the period and extent of rapid frequently modulations would provide the best cues to the identity of the caller.

Foraging strategies of American white pelicans

Abstract: Foraging strategies employed by American white pelicans were studied at a riverine site in Manitoba, Canada, during the breeding season in 1985 and 1986. Six strategies were identified during both diurnal and nocturnal foraging periods. Sit-and-wait was the least common strategy (four instances). Mobile individuals were common but had low rates of bill dipping and prey capture, as did relatively rare and uncoordinated aggregations. A degree of flock coordination occurred in following flocks, characterized by foragers following one after the other, with occasional synchronization of bill dipping among flock members. The largest number of pelicans foraged within more or less circular groups called nuclei. Synchronous bill dipping and apparent herding of prey towards shore were common within nuclei. The most highly coordinated strategy, semicircles, involved small numbers of foragers (2 to 30 birds) that maintained their positions relative to one another, usually in a semicircle but sometimes moving to a closed circular pattern. The greatest degree of synchronized bill dipping occurred in semicircles. Small inter-bird distances and synchronized bill dipping in nuclei and semicircles may enhance their effectiveness in driving or herding clumped fish prey. Foraging strategies could be arranged along a continuum based on degree of coordination, ranging from mobile individuals, then uncoordinated aggregations, through increasing degrees of coordination in following, nuclei, and semicircles. Along this continuum, prey size and capture rats were greatest for the more highly coordinated strategies, while less coordinated strategies appeared to be involved primarily in searching. Switching among strategies fit along the same continuum, with a tendency to switch from less to more coordinated strategies when prey were located and to return to less coordinated search when capture rates declined. Video analysis of captures within large nuclei and observations of positional shifts among foragers in nuclei and following flocks indicated that all individuals within a coordinated group potentially benefited from the presence of others, supporting the view that coordinated foraging strategies in this species are examples of true cooperative foraging. The range of strategies, and interplay among them, appear to provide the American white pelican with a highly effective group foraging system for harvesting mobile, clumped fish prey.

Escape gaits of white-tailed deer, mule deer and their hybrids: gaits observed and patterns of limb coordination

Abstract: 1. The escape gaits of white-tailed deer, mule deer and hybrid white-tailed x mule deer from Alberta were examined to investigate two hypotheses: 1) that the distinctive security patterns of white-tailed deer and mule deer underly their traditional habitat segregation, and 2) that interbreeding between white-tailed deer and mule deer results in disrupted security patterns for hybrid progeny. The first step is investigating these hypotheses, and the goals of this paper, were to identify gaits used by each type of deer and to compare characteristics of limb coordination in these strides. 2. High speed cinematography was used to record the fast escape gaits to captive white-tails, mule deer and hybrids. HILDEBRAND'S (1977) method for analyzing asymmetrical gaits were adapted to examine characteristics of limb coordination. 3. All groups galloped at times, but only white-tails galloped for escape when most alarmed. Mule deer stotted and F1 hybrids (with white-tail and with mule deer mothers) bounded when seemingly most alarmed. Gaits of F1 hybrids were similar among individuals. Although gaits of 3/4- and 7/8-mule deer were variable, these backcrosses largelyfailed to reproduce the specialized mule deer gaits. The consistency of white-tail, mule deer and FI hybrid gaits indicates that these patterns have a strong genetic basis and could have evolved in response to different selective pressures. 4. Galloping white-tails tend to have two brief suspensions in their strides, whereas galloping mule deer tend to have prolonged suspension after the hind limb departure and more overlap between the hind and fore limbs. In part due to these characteristics, galloping white-tails attain faster speeds than galloping mule deer or hybrids. Hybrids are intermediate, but much more similar to mule deer. 5. Limb timing data were plotted on three-dimensions with the axes fore lead, hind lead and midtime lag to consider the range of strides employed by deer. Strides of the purebred gallops and mule deer stott fell into discrete regions of this figure, indicating these gaits are qualitatively distinct for contemporary white-tails and mule deer. liule deer strides that were intermediate between the gallop and stott had large overlap between the fore and hind limbs (i.e. small midtime lag) relative to the amount of overlap between the right and left fore limb (i.e. fore lead), perhaps reflecting gait forms that were evolutionary transitions to the stott.