Inhibition of adult social behaviour in ducks induced by juvenile administration of gonadal hormones

This experiment was designed to study the long-term behavioural effects of gonadal hormone injections into domestic ducklings. Ten male and four female ducklings were injected daily from their 4th day onwards: the males with testosterone propionate and the females with oestradiol benzoate. Five males were injected for 40 days, the other ducklings (5♀ + 4♂) for 80 days. Behavioural effects of these treatments were assessed when the birds were six months old. Social displays were strongly inhibited in the injected males as compared with control birds but no general significant effect was observed for the aggressive and sexual behaviour. The inhibition of social displays is consistent with the view that these behaviour patterns are regulated by the pituitary-gonadal axis and the different levels at which the functional inhibition could have occured are discussed. Far fewer social displays were performed by the males presented with injected females which, on the other hand, showed less sexual behaviour than the control females. This supports the idea that the female plays an important part in the social display of ducks.     

The effects of pre-test conditions on social facilitation of drinking in ducks

The drinking and sieving of Khaki Campbell ducklings have been used as suitable behaviour patterns with which to study the social interactions in flock-living birds. Duckling from four-bird flocks were deprived of water for 3 hr, either in isolation or in groups of four. When the flocks were allowed access to water it was found that the isolated ducklings drank less than the non-isolated ducklings. Whilst both deprived and non-deprived birds engaged in sieving activity during the test, the sieving movements of the non-deprived birds were of longer duration than those of the deprived birds. Pre-test isolation of flock members was also shown to increase the duration of sieving movements. Re-introducing the isolated ducklings to each for the last 5 min of deprivation failed to eliminate the difference in either the drinking or the sieving behaviour between the isolated and non-isolated birds. The difference in drinking, but not sieving, could be eliminated by reuniting the birds for the last 30 min of deprivation. The disruption of flock ‘cohesion’ may lead to the failure of the mechanism of social facilitation despite a similar motivational condition in all flock members.     

Threat assessment by domestic ducklings using visual signals: implications for animal-machine interactions

There are increasing opportunities for robots to work amongst animals in agricultural systems. One potential application is in herding animals prior to catching or transportation. An effective herding robot must be able to interrupt ongoing animal behaviour without causing panic or flight reactions. The extent to which different approaching stimuli interrupted the feeding behaviour of pairs of domestic ducklings was examined to assess their suitability as herding stimuli. Experiment 1 assessed the responses of ducklings to an approaching human (the most likely current herding stimulus), a vertical cylinder (a stimulus with the minimum features of a simple robot) and a model fox (simulating the more natural features of a predator). Interruption of feeding was greatest in response to the human and least to the cylinder. Experiment 2 found no significant difference in the extent to which feeding was interrupted when facial appearance and head orientation of the model fox were manipulated. Experiment 3 examined whether biologically realistic features of the model fox affected duckling response. At a distance of 7 m, photographs of the model fox interrupted feeding behaviour as much as the model itself. However, at a distance of 1 m, the model fox caused significantly more feeding interruption than an intact photograph. A fragmented photograph caused the least interruption of feeding behaviour.     

Looking like mother makes mallard ducklings dominant over their siblings

Colour variation in time and space among animals may affect social relationships such as pairing and dominance interactions. For instance, some birds are naturally sensitive to leg colour, with some colours being more visible or attractive than others. The colour of the leg-rings used to mark birds may thus be related to behavioural and reproductive variables. Most studies have investigated this effect for adults during reproduction, but leg-ring colour may also affect the behaviour of young birds. We tested the potential effect of leg-ring colours on the within-brood dominance hierarchy of mallard (Anas platyrhynchos) ducklings while each brood formed a stable and exclusive family unit with its mother. Ducklings did not acquire a within-brood dominance rank according to the colour of their own ring. This result suggests that mallards may not have a sensory bias for a given colouration. However, ducklings wearing a ring of the same colour as one of the two rings of their mother were dominant over their siblings. We discuss the potential behavioural and methodological implications of this result.     

Spatial structure and parental aggression in eider broods

The spatial position of young animals within a brood affects their survival, so that marginal individuals are at greater risk of predation. Spatial brood structuring may be caused by differences in offspring size, age, hunger, or active parental manipulation through aggression. Nepotistic manipulation of brood structure would confer fitness benefits for parents accepting nondescendant young. However, insufficient kin recognition has often been considered to preclude such nepotism in birds, particularly in precocial waterfowl. We explored the spatial structure of ducklings within broods of eiders, Somateria mollissima, a seaduck with frequent brood amalgamation. We compared the distribution of ducklings of different origin relative to reference females whose kinship to the ducklings was known. We also observed female aggression towards ducklings, to evaluate the role of parental manipulation of brood structure. We found a nonrandom distribution of ducklings within broods; a female's own young were on average closer to her than unrelated young were. We also found evidence for parental nepotism: whether the brood contained unrelated young was the strongest predictor of female aggression towards ducklings. The spatial position, hatch weight and relative size of ducklings showed no significant correlations with each other, suggesting that active parental manipulation may be needed to explain the observed spatial structure. Our study conflicts with previous anecdotal evidence suggesting that brood amalgamation in eiders results in the disintegration of parent-offspring bonds, preventing parental exploitation of nondescendant young. It also opens up the possibility that the spatial position of ducklings depends on their mother's status in the female dominance hierarchy. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Post-hatching parental care behaviour and hormonal status in a precocial bird

In birds, the link between parental care behaviour and prolactin release during incubation persists after hatching in altricial birds, but has never been precisely studied during the whole rearing period in precocial species, such as ducks. The present study aims to understand how changes in parental care after hatching are related to circulating prolactin levels in mallard hens rearing ducklings. Blood was sampled in hens over at least 13 post-hatching weeks and the behaviour of the hens and the ducklings was recorded daily until fledging. Contacts between hens and the ducklings, leadership of the ducklings and gathering of them steadily decreased over post-hatching time. Conversely, resting, preening and agonistic behaviour of hens towards ducklings increased. Plasma prolactin concentrations remained at high levels after hatching and then fell after week 6 when body mass and structural size of the young were close to those of the hen. Parental care behaviour declined linearly with brood age, showed a disruption of the hen-brood bond at week 6 post-hatching and was related to prolactin concentration according to a sigmoid function. Our results suggest that a definite threshold in circulating prolactin is necessary to promote and/or to maintain post-hatching parental care in ducks.     

Social Behaviour of Individual Oval Squids (Cephalopoda,Teuthoidea, Loliginidae,Sepioteuthis lessoniana) within a Captive School

The social behaviour of individually identified squids was observed over a period of 4 mo. Squids were reared in captivity and maintained in a shoal of up to 18 animals. Distances between animals averaged 1.6 body lengths, similar to the 1.2 body lengths of wild teleost fish schools. Smaller animals schooled less frequently and were found at the periphery, and familiar and unfamiliar animals shoaled together. Eighty-six apparent reproductive events were observed. This species of squid, Sepioteuthis lessoniana, is not sexually dimorphic to the human eye and male squids copulated with both males and females but they directed their attention disproportionately towards females. Most copulations occurred more than a month before spawning, lasted only a few seconds and, unlike field observations on spawning grounds, were not followed by mate-guarding. Two body patterns are described that were used consistently in social interactions by both males and females; these patterns were both associated with reproductive behaviour but their exact function was unclear. A sister species, Sepioteuthis sepioidea, has been described as showing complex social behaviour; in S. lessoniana, no evidence for such behaviour was seen.     

The effect of dihydrotestosterone in combination with ovariectomy on intranuclear inclusions in mammotrophs of the Mongolian gerbil

Intranuclear vacuoles and membranes have been observed in mammotrophs of female Mongolian gerbils. Testosterone injection increases the number of cells containing inclusions (1·77±008 inclusions per field in testosterone-injected animals and 0·38±0·05 inclusions per field in controls). Testosterone may well be converted to some other compound which in turn induces the inclusions. Ovariectomy presumably prevented such a conversion inasmuch as testosterone was ineffective in increasing the number of inclusions in ovariectomized gerbils. Neither did the injection of dihydrotestosterone, the biologically active form of testosterone in some organs, increase the number of cells containing intranuclear inclusions.     

Social relations in a mixed group of mules, ponies and donkeys reflect differences in equid type

Donkeys and mules are frequently kept as companion animals for horses and ponies, with these different equids often being considered a homogenous group. However, the extent to which domestic equids form inter-specific bonds and display similar social behaviour when living in a mixed herd has not previously been studied. Here we compare the social organization of these three (sub)species when housed together, providing the first systematic analysis of how genetic hybridization is expressed in the social behaviour of mules. A group of 16 mules, donkeys and ponies was observed for 70h and preferred associates, dominance rank and the linearity of the group's hierarchy was determined. The different equids formed distinct affiliative groups that were ordered in a linear hierarchy with ponies as the most dominant, mules in the middle ranks and donkeys in the lowest ranks. Within each equid subgroup, the strength of the hierarchy also varied. Thus in the present study, the three (sub)species displayed different social organization and levels of dominance and preferred to associate with animals of the same equid type, given the opportunity. These results suggest that different domestic equid (sub)species display variations in social behaviour that are likely to have a strong genetic basis.     

Territorial Behaviour and Social Organization as a Function of the Level of Aggressiveness in Male Mice

Territoriality and social organization were examined in relation to different genetic dispositions for aggressive behaviour. The animals used in the study were male mice of the 51st and 52nd generation of selection for high (Turku Aggressive, TA) and low (Turku Non-Aggressive, TNA) levels of aggressiveness. The level of aggressiveness of the animals was assessed by means of individual tests with non-aggressive standard opponents, after which they were allowed to form individual territories in a 102 times 204 times 90 cm enclosure. TA and TNA males were placed in different enclosures. After 2 wk, when the partitions between individual pens were removed, the behaviour of the animals was observed for a 7-d period. Excessive fighting between the highly aggressive TA males occurred, resulting in the formation of dominant-subordinate relationships. A great number of attacks inflicted were found to be associated with dominance in the colony, and correlated with a high level of aggressiveness when the animals were individually tested for aggression after having been in colony environments. The level of aggressiveness of the TA males that had become subordinates had significantly decreased. The TNA males fought less and were more often found to stay in their original territory for the entire period of observation. The results suggest that different genotypes for aggression arc related to differences in territoriality and social organization in mice.     

Rearing other peoples' young; Brood-mixing in the shelduck Tadorna tadorna

The mixing of ducklings from different broods, in several species of waterfowl, involves care of offspring other than the parents' own. In the eider, Somateria mollissima, this behaviour appears to be of benefit, in terms of increased adult and duckling survival, to both donor and recipient parents, but in the shelduck, Tadorna tadorna, brood-mixing appears not to be advantageous. Dominant males tended to lose ducklings to more subordinate ones but there was no significant difference between donor and recipient parents in the number of their own offspring reared to fledging. The apparent lack of any advantage in brood-mixing suggests that the behaviour might be a consequence of high brood density and that in the shelduck brook defence is adapted to low density.     

The behaviour of calves under four levels of lighting

The object of the present paper was to examine the influence of light intensity on the behaviour of calves. For this purpose, 20 calves of both sexes and of the breeds German Friesian, Simmental and their cross-breeds were kept in groups of 5 animals at 4 different levels of lighting: 2, 20, 100 or 130 lx. The behaviour of the animals was observed once a week by video. For each behaviour pattern and each light intensity, duration, frequency and daily rhythm were calculated. Furthermore, the behaviour sequences were examined.At 2 lx, the lowest level of lighting, the longest duration and most frequent phases of resting behaviour were noted. The daily rhythm of resting behaviour was more distinct in the better-lighted stable than in that with less lighting.Differences also occurred in feeding behaviour, which lasted longer at the higher light intensity.The influence of the light was clearest on social behaviour, and mainly on playing behaviour. The duration and frequency of play-fighting and solitary play-running increased with higher light intensity.Licking of objects was also significantly influenced by the level of lighting. It lasted longest at 130 lx and was shortest at 2 lx.Examination of the behaviour sequences showed that grooming and licking of objects were present in the majority of sequences. Apart from their functions, these activities are also of importance as displacement or redirected activities.The differences in the behaviour due to different lighting could be the result of worse visual ability at the lower light intensities.     

Effects of exogenous gonadotropic and steroid hormones on the social behaviour and gonadal maturation of male domestic ducklings Anas platyrhynchos L.

Male domestic ducklings were injected during their first month of life with mammalian gonadotrophins (ovine LH or FSH, HMG) or gonadal steroids (testosterone or oestradiol). LH and testosterone stimulated sexual behaviour while oestradiol inhibited the increase of aggression observed in control birds during the experiment. The mammalian gonadotrophins did not increase plasma testosterone but nevertheless they all stimulated the testis growth. Several hypotheses which could explain this finding (stimulation of spermatogenesis without any apparent effect on testosterone) are discussed and the possibility of a direct action of LH on the sexual behaviour is analysed. Social displays were only moderately stimulated by testosterone and not at all by gonadotrophins. The hormonal controls of these behaviour patterns remains thus largely unknown.     

Photoperiod influences the development and the expression of personality traits and social behaviour in wild cavies (Cavia aperea)

Seasonality influences behaviour, physiology and life history of organisms, and photoperiod is a reliable and influential cue gearing individual adaptation to seasonal changes in the environment. Plastic phenotypic adjustments according to the prevailing season are a widespread, well-studied phenomenon. Less well known are effects on developmental trajectories of animals born into different seasons. By manipulating the photoperiod during pregnancy and lactation independent of food availability and temperature, we studied if maternal behaviour in the precocial wild cavy (Cavia aperea) responds to this seasonal cue and if maternal behaviour and photoperiod shape offspring development and behaviour. We repeatedly observed mothers before and after birth. We investigated if pups differ in risk-taking behaviours directly after birth (indicating direct prenatal effects) or only after gaining independence of the mother (indicating delayed prenatal or postnatal effects due to own cue sampling). Furthermore, we tested if different simulated seasons of birth affect social and aggressive behaviour of adult animals. While theoretical predictions according to risk-taking are quite clear, they are contradictory for social behaviours that are much less well studied. We predicted that animals born into spring photoperiods would be aggressive because of a need to gather enough resources for early reproduction and successfully establishing a territory at least in males. Spring-born males were more aggressive than autumn-borns, while females did not differ with respect to season. Spring-born females, however, lost more body mass when they had to integrate into an established group and autumn-born females initiated more aggressive interactions. Our data demonstrate flexible and long-term stable seasonal effects on behaviours that likely affect fitness outcomes under natural conditions.     

Effect of cold-acclimation on oxygen uptake and glucose production of perfused duckling liver

The control of hepatic metabolism by substrates and hormones was assessed in perfused liver from young Muscovy ducklings. Studies were performed in fed or 24-h fasted 5-week-old thermoneutral (25 degrees C; TN) or cold-acclimated ducklings (4 degrees C; CA) and results were compared with those obtained in rats. Basal oxygen uptake of perfused liver (LVO2) was higher after cold acclimation both in fed (+65%) and 24-h fasted (+29%) ducklings and in 24-h fasted rats (+34%). Lactate (2 mM), the main gluconeogenic substrate in birds, similarly increased LVO2 in both TN and CA ducklings and the effect was larger after fasting. Both glucagon and norepinephrine dose-dependently increased LVO2 in ducklings and rats, but cold acclimation did not improve liver response and liver sensitivity to norepinephrine in ducklings was even reduced in CA animals. Liver contribution to glucagon-induced thermogenesis in vivo was estimated to be 22% in TN and 12% in CA ducklings. Glucagon stimulated gluconeogenesis from lactate in duckling liver and the stimulation was 2.2-fold higher in CA than in TN fasted birds. These results indicate a stimulated hepatic oxidative metabolism in CA ducklings but hepatic glucagon-induced thermogenesis (as measured by LVO2) was not improved. A role of the liver is suggested in duckling metabolic acclimation to cold through an enhanced hepatic gluconeogenesis under glucagon control.     

Behaviour of the Indian social wasp Ropalidia cyathiformis on a nest of separate combs (Hymenoptera: Vespidae)

Observations were made on a nest of Ropalidia cyathiformis consisting of three combs. The number of eggs, larvae, pupae and adults were monitored at about 3-day intervals for a 2-month period. The behaviour of the adults was observed with special reference to the proportion of time spent on each of the three combs, the proportion of time spent away from the nest site and the frequencies of dominance interactions and egg laying. The adults moved freely between the three combs suggesting that all of them and all the three combs belonged to one nest. However, most of the adults preferred combs 2 and 3 over comb 1. Of the 10 animals chosen for a detailed analysis of behaviour, seven spent varying periods of time away from the nest site and oRen brought back food or building material. Five of the 10 animals laid at least one egg each but two adults monopolized most of the egg-laying. The animals showed a variety of dominance interactions on the basis of which they have been arranged in a dominance hierarchy. The dominant individuals laid most of the eggs and spent little or no time foraging, while the subordinate individuals spent more time foraging and laid few eggs or none. It is argued that R. cyathiformis is different from R. marginata , the only other Indian social wasp whose behaviour has been studied, in being at a more primitive stage of social organization.     

Protein synthesis in the critical periods of early postnatal ontogeny: its role in the development of the interspecific aggressive behavior of rats

Chronic administration of cycloheximide to young rats from 15-th to 30-th postnatal day before daily 3-hour seances of their contacts, disturbed the formation of animals intraspecies aggressivity. In adults it was manifested by hyperaggressivity and by changes of proportions of different reactions in the integral act of aggressive behaviour. By their character these disturbances were close to those observed in the young rats completely deprived of social contacts in this period of ontogenesis.     

Habituation of object contact in socially-reared and isolated rats (Rattus norvegicus)

Rats reared in social isolation were found to contact fewer novel objects in an open-field than their socially reared litter mates. They also contacted a smaller variety of objects, and contacted them in different ways. Social animals showed more manipulatory behaviour than the isolates, but there were no differences in sniffing. In a second experiment, employing a longer session, it was found that social animals showed more rapid habituation of object contact. This may account for previous claims that isolates show heightened levels of exploration.