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Animals can find food using information from the food itself or from conspecifics that are also looking for food. Social information can be actively communicated or based on unavoidable by-products of feeding activities. We present three experiments that explore the relative importance of odour gradients and social information as Bufo americanus tadpoles locate food sources. In the first experiment, tadpoles rapidly aggregated at food patches and discriminated between the qualities of two food patches spaced 15 cm apart in the field. In a second experiment, the initial presence of tadpoles at one food patch enhanced aggregation for 1 h, compared to an identical food patch without tadpoles spaced 114 cm apart. In a third experiment, the time required to initial contact with a single food patch did not change over a 16-fold range of food concentration, suggesting that B. americanus tadpoles have a limited ability to locate food from a distance using information from the food itself. Finding food and discriminating food patch quality from a distance is probably a major adaptive advantage of sociality in B. americanus tadpoles, although the presence or absence of active signalling remains to be determined.

We investigated how the behaviour of domestic foals, Equus caballus, living at pasture with their dams was associated with foal gender, mare rank and the development of abnormal oral behaviour, both during the preweaning period, and over a period of up to 4 years postweaning. A population of 186 foals belonging to private owners and commercial studs was studied. The behaviour of male and female foals hardly differed, but mare rank affected patterns of foal social interaction and suckling behaviour, with foals of subordinate mares involved in more affiliative interactions. These foals also spent more time in perisuckling activities such as teat nuzzling than foals of other mares. During the study, 18 foals developed abnormal oral behaviour before weaning and 42 foals developed abnormal oral behaviour after weaning. The development of abnormal oral behaviour was associated with suckling behaviour in a variety of ways. Foals that had already developed abnormal oral behaviour at the time of the preweaning observations were involved in more suckling terminations within bouts than normal foals or foals that developed future abnormal behaviour, and pushing the udder with the muzzle was most frequent in these foals. Foals that had no current abnormal oral behaviour, but that would develop this in the future, spent more time suckling and twice as much time teat nuzzling as other foals. The results add to the growing evidence of associations between digestive function and abnormal oral behaviour in horses.

Studies on vertebrate species in which the offspring obtain food only from their parents have shown that offspring begging conveys information on offspring hunger. It is unclear whether begging can also convey information on hunger in partially begging species, in which the offspring, from hatching, obtain food partly through begging for food from the parents and partly through self-feeding. In partially begging species, offspring hunger state could reflect the amount of food obtained by self-feeding in addition to the amount obtained from the parent, and the offspring could respond to hunger by self-feeding instead of begging. To test whether begging reflected the current hunger state of offspring in the partially begging beetle Nicrophorus vespilloides, we subjected larvae to two deprivation treatments: no access to any food for 2 h (i.e. food-deprived larvae) and no food provided by the parent (i.e. self-feeding larvae). Larvae of both treatments spent more time begging than did control larvae, which had access to food both from the parents and by self-feeding. Furthermore, the amount of begging differed between the treatments, with food-deprived larvae spending more time begging than the self-feeding ones. We conclude that, in partially begging species, food obtained through both foraging strategies, i.e. begging for food from parents and self-feeding, contribute to the offspring’s current hunger state, and that begging can convey information about it.

Self-grooming is a common behaviour among many species of ungulates, as it is among several other mammalian taxonomic groups. In goats, as in rodents and small felids, self-grooming appears to reflect an underlying endogenous timing mechanism, resulting in what has been referred to as programmed grooming. We tested the prediction from the programmed grooming model that newborn and young goats, Capra hircus, would groom more frequently than similarly maintained conspecific adults. This prediction was upheld in that goat kids, from 2 weeks of age, orally groomed and scratch-groomed significantly more frequently than adult females. When the body surface-to-mass ratio of young goats, which was initially about 230% that of adults, declined to about 150%, the difference in grooming rate of the young was no longer significantly elevated over that of adults recorded at the same time of year. We also tested the predictions that oral grooming in wool sheep, Ovis aries, is inherently programmed and will occur in adults after shearing and in lambs with undeveloped fleece at levels similar to those of ancestral hair sheep and lambs. When fully fleeced adult wool sheep were shorn, they engaged in grooming in a pattern and frequency not different from that of hair sheep with a pelage representative of ancestral sheep. Wool lambs also groomed at a rate similar to that of hair lambs. Therefore, the elevated rate of programmed grooming of newborn and young ungulates appears to reflect their developmental precociousness and consequent exposure, in nature, to ectoparasites.

Adult cottontop tamarins are sensitive to the functionally relevant and irrelevant features of objects used as tools to gain access to food. We conducted four experiments designed to assess whether infant cottontop tamarins show comparable sensitivities to functionally relevant and irrelevant features. All subjects were reared in a species-typical social environment, but prior to the present studies had never participated in any experiments, and had no access to tools or other freely moving, manipulable objects with the exception of food. Despite their lack of experience, the pattern of object choice by infants precisely mirrored those obtained with adults. Specifically, having learned to use a hard blue cane to retrieve food (experiment 1), infant tamarins immediately generalized to other objects (experiments 2–4), recognizing that changes in colour and texture play no role in an object's functionality as a tool, whereas changes in size and shape do. These data suggest that for cottontop tamarins, a species that does not naturally use tools, and infrequently manipulates objects, that the capacity to distinguish between functionally relevant and irrelevant features develops in the absence of domain-specific experience. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .

The behaviour of house cats Felis silvestris catus from nine litters was recorded at 4 months, 1 year and 2 years of age, in their home environment immediately after meals fed by their owners. We extracted by principal components analysis four elements of 'behavioural style' that were consistent from one age to another: based upon behaviour patterns that were most heavily loaded on each component, these were labelled as Staying Indoors, Rubbing, Investigative and Boldness elements. The Staying Indoors and Rubbing elements are similar to two aspects of behavioural style identified in a previous study of adult cats; the Boldness element, possibly coupled with the Investigative element, may be similar to the shy/bold continuum identified in controlled studies of cats and other species. Four-month-old male cats were the most likely to Stay Indoors; the Rubbing element increased with age in the majority of individuals, both male and female. Littermates tended to be similar to one another in Rubbing (at 4 months) and Boldness (up to 1 year). A positive effect of handling received during the first 8 weeks of life was detected for Boldness at 4 months of age. Copyright 2001 The Association for the Study of Animal Behaviour.

The tiny harvest mouse, Micromys minutus, is skilled at climbing among grasses. Owing to the short lactation period of 15-16 days, young harvest mice need to achieve this climbing skill very rapidly. We examined the early development of five components of climbing behaviour and the final climbing pattern of harvest mice from birth to weaning. During the lactation period, the pups' climbing ability developed rapidly and they were able to climb a vertical bar by the time they first emerged from their nest. Climbing skills were acquired in the following order: hand grasping at 3-7 days; foot grasping at 6-9 days; quadruped stance at 6-11 days; tail prehension at 10-11 days; and righting at 10-12 days. The ratio of foot digit length to foot length was greater in harvest mice than in laboratory mice, Mus musculus, indicating a better grasping ability in the former. Copyright 1999 The Association for the Study of Animal Behaviour.

For begging to benefit chicks, parents must respond to increased begging by bringing more food. To investigate whether parents change their provisioning in response to begging levels, I enhanced the begging levels of broods of yellow-headed blackbirds, Xanthocephalus xanthocephalus, using recorded vocalizations. In a short-term experiment, females and males doubled their visits to broods without reducing their load sizes during 2 h of playback. Nestlings gained more mass during the playback period than during a 2-h control period. In a long-term experiment, nestlings gained more mass in nests from which begging calls were broadcast over a 5-day period than nestlings in nests without playback. Copyright 1998 The Association for the Study of Animal Behaviour.

In the past decade there has been widespread acceptance of the idea that the use of live, socially interactive tutors in song learning experiments produces results that differ dramatically from, and are more valid than, results obtained with tape tutors. The influential series of experiments by BaptistaPetrinovich (1984, Animal Behaviour, 32, 172-181, 1986, Animal Behaviour, 34, 1359-1371; PetrinovichBaptista 1987, Animal Behaviour, 35, 961-974) have promoted this view, and their results have been widely accepted. BaptistaPetrinovich's results have led them and others to question whether there are age-limited sensitive phases for song learning, as Marler's (1970, Journal of Comparative Physiology and Psychology Monographs, 711-25) early studies on the white-crowned sparrow, Zonotrichia leucophrys, suggested, and led them to argue that interactive tutoring produces essentially open-ended learning. I argue here that this view is mistaken, and that the sensitive phase for song learning in the white-crowned sparrow is identical for live and tape tutors and is restricted to the first few months of life. BaptistaPetrinovich presented live and tape tutors for different periods to their subjects. Type of tutor (live versus tape) is confounded with duration of exposure to tutors. As a consequence, their experiments confound two different forms of song learning that occur at different ages, and give the mistaken appearance of an extended sensitive phase when live tutors are used. Copyright 1998 The Association for the Study of Animal Behaviour

Using field experiments, we investigated the development of parent-offspring recognition in the thick-billed murre, Uria lomvia. Cross-fostering experiments (N=73) showed that the likelihood of parents accepting a foreign chick decreased with chick age. Simultaneous-choice playback experiments demonstrated that chicks discriminate between the calls of their parents and both strange and familiar adult conspecifics from as early as 3 days old. In presentation experiments with chicks of fledging age (/=14 days), adults responded more strongly to the calls of their own chicks than to other familiar chicks from the same breeding ledge. Results are consistent with those of earlier studies of parent-offspring recognition in the congeneric and ecologically similar common murre, U. aalge, which were among the first to suggest that parent birds and their chicks can identify each other's calls. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

To determine the factors that cause the development of stereotypic digging, features in the captive environment of young Mongolian gerbils,Meriones unguiculatus, were varied. It was hypothesized that stereotypic digging develops because stimuli that control digging motivation are lacking. A regulatory model of motivation was used to examine whether digging motivation is decreased by the performance of the motor pattern ‘digging’ or by the consequences of digging. Young gerbils that could dig in a sand area developed stereotypic digging. In contrast, young gerbils that could not dig in sand but had access to an artifical burrow, which was presumed to be the consequence of digging, showed less non-stereotypic digging than gerbils from the sand treatment and did not develop stereotypic digging. Therefore, the mere perception of the stimulus ‘burrow’ by a retreating animal decreased digging motivation. The complexity of the artifical burrow was reduced to a few elements to analyse in detail the stimuli that control digging motivation. A dark and narrow chamber at the end of a tube connected to the cage provided the stimuli that elicited retreating and prevented the development of stereotypic digging. The tube was a necessary feature: a chamber alone did not prevent the development of stereotypic digging. Such a stimulus situation seems to match the stimuli of a natural burrow which is built to buffer climatic fluctuations and to provide shelter from predators. The results show that stereotypic digging develops when a young gerbil cannot achieve a stimulus situation that is efficient in decreasing digging motivation.

Larvae ofDrosophila melanogasterinfest necrotic fruit, which the sun can heat to temperatures warm enough to kill or damage in-dwelling larvae. This study examined whetherDrosophilafemales could recognize and avoid ovipositing on necrotic fruit that had previously been heated to lethal temperatures but was at moderate temperatures at the time of oviposition. Neither previous heating of necrotic fruit nor the presence of heat-killed larvae deterred oviposition. Females do not use evidence of prior heating to avoid potential oviposition sites, and thus apparently behave non-optimally with respect to temperature.

This study investigated whether pigtail macaque mothers encourage their infants' independent locomotion by increasing distance from them and displaying a retrieval signal, the pucker face. Fifteen mother–infant pairs living in a large captive social group were focally observed during the first 12 weeks of infant life. Mothers puckered to their infants only when out of contact with them, and the pucker was followed by reduction in distance by the mother or the infant. The pucker was significantly associated with an increase in distance initiated by the mother, and mothers that frequently puckered to their infants were also those that frequently left them. Multiparous mothers puckered to their infants more than primiparous mothers. The infant's initiative in reducing distance after the pucker increased with its age, and the latency of its response gradually decreased in the first 6–7 weeks of life. Infants that received more puckers from their mothers spent less time in contact with them and approached and left them more frequently than infants that received fewer puckers. The evidence is insufficient to assess unequivocally whether developmental changes in infant responses to the pucker reflect social learning or maturation of motor skills.

Post-weaning mother-daughter associations are typical of many ungulates, but their existence among sheep is controversial. In bighorn sheep, Ovis canadensis , at high population density, strong mother-yearling associations were found involving mostly ewes whose lamb-of-the-year died at or soon after birth. At low population density, there were no mother-yearling associations regardless of maternal reproductive status. Non-lactating ewes and most ewes caring for a new lamb did not associate with their yearlings. The mother-yearling bond appeared stronger for female than for male yearlings, while maternal age had no effect. Associated yearling females had a nearly significant trend towards greater mass gain and greater body mass by the end of the summer compared with independent yearling females, but no trend was found when comparing associated and independent yearling males. Mothers that associated with their yearlings gained mass faster over the summer than mothers that nursed lambs, and by the end of the summer they were heavier than non-lactating ewes. Therefore, post-weaning association did not appear to be very costly for mothers. This study demonstrates how changes in ecological circumstances can lead to drastic changes in social organization.

Attempts to repeat the original reports by Lorenz (1939, Zool. Anz. Suppl. , 12 , 69–109) and Tinbergen (1948, Wilson Bull. , 60 , 6–52) that goslings respond more to moving hawk silhouettes than to moving goose shapes have yielded mixed results. The combination of rearing and testing conditions was critical in obtaining a difference between reactions to the two models. In particular, group-reared birds tested in groups responded primarily by crouching, whereas individually tested birds (regardless of rearing) reacted mostly by running and calling. The response to goose models habituated faster than the reaction to hawk models.

Abstract. This report describes a field study of tail flagging by young California ground squirrels, and compares their behaviour to that of adults. Focal and scan samples of marked animals were used to determine the context of signalling, and to establish the behavioural concomitants of flagging in the signaller and potential perceivers. Both pups and adults invariably use this signal when encountering a snake, but both tail flag more often when there is no obvious elicitor (Hersek & Owings 1993, Anim. Behav., 45, 129-138). When no snake was present, pups used tail flagging in tonic communication, as adults did. Although tail flagging by adult females was related to the vulnerability of pups, signalling by both adult males and pups reflected their own vulnerability. Tail flagging by adult mates and pups differed, however, in its effects on perceivers. Adult males induced nearby animals to maintain higher levels of snake vigilance, while tail flagging by pups induced others to remain nearby. Pups distinguished more clearly between contexts of tail flagging than did adults. Both pups and adults tail flagged more frequently on days when snakes were on the site (than when snakes were absent), but this difference was greater for pups than for adults. Pups were also more likely than adults to pair tail flagging with calling while dealing directly with snakes (as contrasted with flagging when no snake was present). Overall, the differences between pups and adults appear to fit an age-specific interpretation of ontogeny. Pup use of tail flagging seems appropriate for their developmental stage, and does not simply reflect an incompletely developed signalling system.

Abstract. Female garibaldi damselfish, Hypsypops rubicundus , preferentially spawn with males guarding eggs in early development, and always lay near the youngest eggs already present in nests containing multiple clutches. Field observations and experiments of H. rubicundus during the mating phase showed that brood-guarding males usually cannibalized older clutches if they had been exposed to empty nest space. Mating males rarely cannibalized younger clutches, regardless of their position, and rarely cannibalized older clutches that were surrounded by younger eggs. When peripheral older eggs were cannibalized, the newly exposed and adjacent empty space was covered with new eggs. When exposed older eggs were not cannibalized, the surrounding nest space remained empty. These data suggest that male filial cannibalism during the mating phase is an adaptive response to female spawning-site preference; selectively cannibalizing exposed older eggs minimizes the amount of empty nest space by ensuring that only younger, more attractive eggs are exposed to empty nest space. Such filial cannibalism provides a further adaptive explanation for the tendency of females laying in empty nests to deposit their eggs near the periphery of the nest where they are more likely to be surrounded by younger eggs.

Abstract. It is commonly suggested that the principal function of allogrooming is to reduce social tension between group members, but direct evidence of the physiological consequences of grooming at particular sites is lacking. By filming allogrooming sequences in a herd of Camargue horses, Equus caballus , their preferred grooming site, which lies on the lower neck, was identified. Experimental imitation of grooming at this site reduced the heart rate of the recipient while grooming on a non-preferred area did not, in both adults and foals. This preferred site lies close to a major ganglion of the autonomic nervous system.

Second-hatched chicks in two-chick broods of the blue-footed boody, Sula nebouxii , usually remain subordinate to their siblings throughout the nestling period, even those that outgrow the firsthatched chick. Initially, the superior size and maturity of the first-hatched chick enable it to dominate, but subsequently other factors could be involved. The idea that a chick's own social experience determines whether it behaves aggressively or submissively was tested by pairing unfamiliar chicks in the field. In brief trials, dominants (chicks with a history of dominance) tended to behave aggressively and subordinates (chicks with a history of subordination) tended to behave submissively, whatever the prior social experience of the partner. However, in chicks lacking prior social experience with a sibling, direction of dominance depended on relative size or age. When experience was pitted against size, eight of 12 experimental subordinates permanently paired with younger and smaller dominants initially behaved aggressively, although only one subordinate succeeded in becoming dominant. None of the nine control subordinates that were paired with older and larger dominants showed aggressive behaviour. In conclusion, the results of this study demonstrate that agonistic roles are determined by experience, although subordinates may become aggressive when they detect a personal advantage. When subordinates do become aggressive they are competitively inferior to smaller dominants.

To assess temporal and spatial variations in the emission of the odour guiding them to the nipples, we exposed newborn rabbits, Oryctolagus cuniculus, to lactating females in a series of simultaneous olfactory choice tests. They showed a clear preference for females in early, rather than late, lactation, and in the prenursing, rather than postnursing, phase. Furthermore, the female's abdominal, and specifically nipple, regions were more attractive to pups than the back and non-nipple abdominal areas. Finally, the surface odour cues from the abdomen of lactating females were as attractive as the odour of rabbit milk itself. These data suggest that the source of the active compound eliciting preferential orientation is located on the nipple, a site allowing simultaneous evaporation in air and dissolution in milk. Copyright 2001 The Association for the Study of Animal Behaviour.

Owners have often been found to have an advantage in animal contests. One explanation of this is that the resource under dispute is of greater value to the owner than to the intruder (nonowner). Such 'resource value asymmetries' may be caused by intrinsic factors, such as the physiological state of the contestants. Females of the bethylid wasp Goniozus nephantidis fight for possession of paralysed hosts. A recent study found that larger females tend to win but owner status also confers an advantage. We tested the hypothesis that ownership advantage is linked to differences in egg load (the number of unlaid ripe eggs) between contestant females. Egg loads were highly variable and positively influenced by age, nutrition, body size and host ownership. Owners almost always won owner-intruder contests. The outcomes of owner-owner contests (in which size and status asymmetries were absent) were strongly influenced by differences in egg load. Copyright 2000 The Association for the Study of Animal Behaviour.

Individual birds are expected to maximize their fitness by directing their chick-feeding effort only towards broods containing closely related nestlings. We tested this prediction using data from the cooperatively breeding Arabian babbler, Turdoides squamiceps. Individual chick-feeding effort, in the form of visit rates and load sizes delivered to the nest, was compared with three measures of relatedness: (1) band-sharing coefficients derived from multilocus minisatellite DNA fingerprints; (2) coefficients of relatedness based upon pedigrees inferred from observed group histories; and (3) observed information on relatedness that was available to the birds themselves. There was little effect of any of the three measures of relatedness on individual visit rates or load sizes delivered to the nest, both across individuals and within each group separately. In the majority of cases, we conclude that individual birds did not have access to sufficient information concerning their relatedness to the brood. As in certain other group-territorial cooperative breeders, Arabian babblers may best direct their effort towards relatives by simply feeding any nestlings that appear on their territory. Copyright 1999 The Association for the Study of Animal Behaviour.

Studies of kin recognition in birds have usually examined parent-offspring recognition, while studies of sibling recognition are relatively rare. Using choice experiments, we studied the development of sibling recognition among common tern, Sterna hirundo, chicks and tested the cues used for recognition. We collected newly hatched common tern chicks and raised them in a laboratory in 10 artificial broods of three. Chicks showed a significant preference for broodmates ('siblings') over familiar nonsiblings (nonsiblings from neighbouring broods) when first tested at 4 days posthatching, earlier than previously reported. Preferential approach to siblings was most common in broods with low levels of intrabrood aggression. Responsiveness of test chicks was highest when test chicks and stimulus chicks could both see and hear each other and lowest when they could only hear each other. Sibling-biased approach did not depend on stimulus and test chicks seeing each other, only on test chicks seeing (and probably hearing) stimulus chicks. Surprisingly, no preference was shown for siblings over strange nonsiblings, suggesting that a preference for siblings may involve learning the identity of not only siblings, but also of chicks from neighbouring broods. Copyright 1999 The Association for the Study of Animal Behaviour.

We studied mate choice in the wandering albatross, Diomedea exulans, using data from 32 years of banding returns in the population of the Crozet Islands. We studied mating choices in a single year, when the Crozet Islands population was male biased (8:5, males:females). Thus, we expected that females might show great flexibility of choice of partners. Because age and experience might influence mate choice, we tested the expectation that females would choose the oldest and most experienced males for pair bonding. Pair bonds usually last until one member of the pair dies (0.3% of the birds 'divorce'), so mate choice should be especially important. We found that the ages of males and females in both displaying and bonded (breeding) pairs were significantly correlated. These age-associated pairings were not a passive phenomenon, but appeared to be due to an active process of selection of mates of similar age. First-time breeders sought mates of similar age, but preferred those with the most experience. Remating, experienced birds whose mates had died did not pair with individuals of significantly similar age, but predominantly paired with other widowed birds that, on average, were also relatively old. Mate fidelity in wandering albatrosses may be due to the cost of finding and bonding with a new mate. Pair bonds, and thus breeding, took an average of 3.2 and 2.3 years to establish, for males and females, respectively. Thus, remating exerts a potential average reproductive cost of about 15% of lifetime reproductive success. Copyright 1999 The Association for the Study of Animal Behaviour.

Chilled embryos of pelicans, Pelecanus erythrorhynchos, begin to vocally solicit parental heat at the pipped-egg stage. Honest signalling models predict that if vocal heat solicitation is a true reflection of need, then solicitation should be costly and costs should increase with the embryo's need for warmth. Using open-flow respirometry, we measured the metabolic costs associated with vocal heat solicitation by exposing embryos to either a decreasing or increasing series of body temperatures, ranging from 25 to 37.8 degrees C. We measured baseline costs (stable temperature, embryo silent) and costs associated with cold-induced calling at each temperature. At natural incubation temperature (37.8 degrees C), call rates and costs associated with calling were negligible, as was thermal need. Metabolic costs relative to baseline costs and costs per call increased with thermal need as body temperature declined. Absolute metabolic costs increased between 37.8 and 35 degrees C, then remained stable down to 25 degrees C. Call rates increased as embryos were chilled within the range of temperatures most frequently experienced in nature (35-37.8 degrees C), then decreased significantly for all lower temperatures, probably owing to reduced overall metabolic rate at lower temperatures (25-37.8 degrees C). The results generally support the honest signalling prediction that vocal heat solicitation is metabolically costly, and that costs increase with need. Copyright 1999 The Association for the Study of Animal Behaviour.

The evolved functions, if any, of infant handling (IH) by female primates remain unclear for many species. I tested a new hypothesis, that IH tests social bonds between adult females, using data on a group of wild white-faced capuchins. I also tested the nonadaptive, learning-to-mother, reciprocity, harassment and alliance-formation hypotheses. Focal subjects were the mothers of 10 infants that ranged in age from 0 to 90 days. The behaviours comprising IH (inspecting, nuzzling, sniffing, and a distinctive vocalization) differed from typical maternal behaviour. Nulliparous females engaged in no more IH than did parous females. The median frequency of rough handling was zero, kidnapping was not observed, and maternal restraint of infants was extremely rare. Infant handling rate was unrelated to the relative dominance ranks of the mother and the handler. Females tended to handle the infants of females with which they groomed and formed aggressive coalitions more frequently. Dyadic IH rates were not correlated with rates of allonursing when the infants were older than 90 days of age. There was no evidence for reciprocal exchanges of IH between females. Mother-terminated IH bouts were longer when the mother had groomed the handler more frequently before the infant's birth. Based on these findings, the learning-to-mother, reciprocity and harassment hypotheses are unsupported for this species. Some support exists for the nonadaptive hypothesis. Contrasting predictions of the bond-testing and alliance-formation hypothesis are presented for future testing. Copyright 1999 The Association for the Study of Animal Behaviour.

Two-chick broods of the blue-footed booby, Sula nebouxii, ordinarily exhibit stable dominance-subordinance, with the senior (first-hatched) chick habitually aggressive and the junior one habitually submissive (Nelson 1978, The Sulidae: Gannets and Boobies. London: Oxford University Press). But are both the subordinate and the dominant chick affected in their agonistic tendencies by early social experience? To answer this, we permanently paired subordinate and dominant chicks, 2-3 weeks old, with singletons (chicks lacking experience with a nestmate) by cross-fostering. During the first 4 h after pairing, subordinate chicks were seven times less aggressive than singletons and twice as likely to be submissive; dominant chicks were six times as aggressive as singletons. Although most subordinates consistently lost agonistic encounters during the first 10 days after pairing, the proportion of dominants that won decreased progressively until, by day 6, only about half of dominant chicks were winning. Early social experience has a strong but reversable training effect on both subordinates and dominants. Training as a subordinate showed more persistent effects than training as a dominant, possibly in part because our testing situation perpetuated subordinate training and counteracted dominant training. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Domestic animals that are socialized to humans are often more easily managed and less timid than those that are not. We examined whether increased handling and artificial feeding of domestic sheep, Ovis aries, at an early age would decrease their subsequent timidity towards people. Forty-eight lamb twin sets were divided into four treatment groups for 2 days of treatment at ages 1-3, 3-5, 5-7 or 7-9 days. Treatment lambs were fed milk replacer and were handled four times/day for 5-min periods. Their twins, used as controls, were left with their dams. Two 5-min tests of lamb temperament were conducted at ages 2, 4, 6, 8, 10, 15 and 25 days. Testing consisted of a stationary human encounter, in which lambs' responses to a sitting person were recorded continuously, and a moving human encounter, in which lambs' responses to a person walking at 0.5 m/2 s were recorded by instantaneous scans. Measures included latency to proximity (2 m) and arm's reach (1 m) of the person, time spent in proximity and within arm's reach, average distance (m), mean number of human contacts, number of lambs contacting a person and following/approach/avoidance. Treatment lambs showed significantly greater affinity for humans than their twin controls. The 1-3-day treatment group showed the greatest response to treatment, consistently outperforming controls in all of the above measures. These results suggest that 40 min of positive human contact at age 1-3 days reduces lamb timidity to people. Socialization of lambs to humans need not disrupt the primary lamb-dam bond, and it may have positive management as well as welfare implications.\C 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour Copyright 1998 The Association for the Study of Animal Behaviour.

The establishment of mixed broods in populations of Canada geese, Branta canadensishas been a subject of controversy. The possible adaptive significance of this behaviour was evaluated as it relates to the survivorship of goslings. Distance of goslings from the adults, gosling status (i.e. natural or adopted) and survivorship to 5 years were measured to predict the value of aggregation behaviour. Spatial data indicated that adopted goslings were further from female adults than natural goslings. Recapture data indicated that mixed broods improved the survivorship of natural goslings.1997The Association for the Study of Animal Behaviour

During the spawning season, male garibaldi, Hypsypops rubicundus (Pomacentridae), defend algal nests within permanent territories on which females deposit eggs. Eggs in the early stages of development are bright yellow and turn grey as development proceeds. Field observations indicated that females preferentially approached nests with eggs in the early stages of development prior to or in the absence of male courtship and were more likely to spawn in such nests than in empty nests or nests with only eggs in the advanced stages of development. Field experiments involving pairwise manipulations of nests with eggs revealed that, between nests, those that retained eggs in the early stages of development were significantly more likely to receive new eggs before nests that were completely stripped of such eggs or retained only eggs in the advanced stages of development. Within nests containing eggs in both the early and advanced stages of development, females deposited eggs only among other eggs in the early stage. The presence of eggs in the early stage is at least one factor influencing the observed choice pattern. Female preference to deposit eggs among other eggs in the early stages of development is predicted by theoretical and empirical studies on male care strategies and the sources of egg mortality among fishes with paternal egg-care.

Summary Simultaneous recordings were made of sounds and movements produced by avian embryos of six precocial and two passerine species during the final developmental stage before hatching when lung ventilation has begun. Sounds and movements occurred in all live embryos almost without a break. Characteristic rhythms occurring in all species were those of clicking and hatching.