Sylvie Cloutier

Recent social experience, body weight and initial patterns of attack predict the social status attained by unfamiliar hens in a new group

To enhance understanding of processes determining social dominance, we quantified the contributions of existing individual characteristics and experience, and information obtained during initial encounters with new group members, on social status attained by hens ( Gallus gallus domesticus ) in a new group. We hypothesised that previous social experience (either with strangers or flock mates), body weight and comb size would be good predictors of a hen′s aggressive behaviour and subsequent social status. Using structural equation modelling, we identified best-fit models to predict the outcome of combining unfamiliar individuals varying in these characteristics. In new triads of 150 red rock × light Sussex hens, hens with a relatively large comb and high body weight were more likely to have won a recent fight and performed more double attacks in their new group. Hens with recent experience of winning were more likely to attain the alpha position in the new group. In a second trial on new tetrads of 32 white leghorn hens, hens with a higher body weight performed more double attacks, leading to a higher rank in their new group. Hens that had recently been high ranking in their former social group also tended to perform more double attacks. Comb size and plumage condition were not good predictors of attack behaviour or rank in this trial. In both trials, a hen′s body weight had predictive value in determining her attack behaviour and subsequent social status when introduced to a small number of strangers. We suggest that the timing and quality of social experience obtained prior to regrouping, the relative difference in comb size between opponents, and the absolute size and carriage of the comb (upright or floppy), influenced the efficacy of previous social experience and comb size as predictors of behaviour and rank in a new group.

Cannibalistic behaviour spread by social learning

Abstract We hypothesized that social learning is involved in the spread of cannibalism in domestic fowl Gallus gallus domesticus . To investigate this hypothesis without harming birds, we used an inanimate chicken model as our cannibalism stimulus. We randomly assigned flocks of 12 White Leghorn pullets to one of two treatments: (1) flocks with two trained demonstrators ( N =9) and (2) control flocks ( N =8). Demonstrators were trained to pierce a membrane covering a dish of chicken blood and consume the blood. To assess the effect of access to the cannibalism stimulus during demonstrations, we randomly assigned observer pairs to one of two observer treatments: (1) observe stimulus through a wire mesh partition and (2) observe stimulus within the same enclosure. We conducted five 10-min demonstration sessions, each followed by a 10-min test of each observer pair in the absence of demonstrators, over a period of 15 days when the birds were 41–55 days of age, and two further tests at 63–64 and 91–92 days of age. Pairs that observed demonstrators piercing a membrane and consuming blood were more likely to perform this task when tested than control pairs. Learning of the task was enhanced by direct access to the cannibalism stimulus rather than observing it through a wire mesh partition. Blood consumption during tests was increased by direct access to the cannibalism stimulus during demonstration sessions. The birds made bigger holes in the membrane when tested after observing trained demonstrators and after having direct access to the stimulus. Our results provide the first experimental evidence that social learning can contribute to the spread of cannibalistic behaviour in domestic fowl. We suggest that stimulus enhancement and observational conditioning were the social-learning mechanisms involved. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .

Does pecking at inanimate stimuli predict cannibalistic behaviour in domestic fowl

We assessed the pecking behaviour of caged White Leghorn hens towards feather-shaped stimuli varying in colour (red or blue), material (paper or feather) and movement (stationary or movable) attached to a board placed in the feed trough. Each of the eight stimulus combinations was presented to two replicate groups of 5 young hens for 15 min at 45 and 57 days of age. We predicted that the birds would be especially attracted to red movable feathers simulating a live bird with bloodstained feathers. Severe (forceful) pecks were directed more frequently at feather than paper stimuli (P<0.05) and at movable than stationary stimuli (P<0.01) but there was no differential response to red and blue stimuli. We reassessed responses to the stimuli by a subset of the original birds, now in 16 groups of four hens, at 696 and 710 days of age. We found no significant effects of colour, material or movement on the latency to peck the stimuli, or the frequency of gentle and severe pecks at the stimuli, indicating that responses to the stimulus characteristics were not consistent between young and old hens. There was a positive correlation between the frequency of severe feather pecking at flock mates and the frequency of cannibalistic behaviour (P<0.01), consistent with reports that bleeding resulting from feather pecking can lead to cannibalism. We found no significant correlation between the frequency of pecking at the inanimate stimuli and the frequencies of pecking at the flesh and feathers of flock mates. This analysis does not take into account possible behavioural differences between primary cannibals that drew blood and secondary cannibals that joined a cannibalistic attack once blood had been drawn. We conclude that the frequency of pecking at inanimate stimuli was not a good predictor of future cannibalistic behaviour by the hens in this study. However, a tendency for future cannibals and severe feather peckers to have longer latencies to peck the inanimate stimuli warrants further investigation. It will be possible to use responses to specific types of inanimate stimuli to predict cannibalistic tendencies only if future cannibals are found to have stable responses to those stimuli over time.

Differences in skeletal and ornamental traits between laying hen cannibals, victims and bystanders

Abstract We compared the size of skeletal and ornamental traits, and asymmetries in bilateral skeletal traits, between victims of cannibalism, cannibals and bystanders within small groups of caged female White Leghorns at the time of cannibalistic attacks (i.e. injurious pecks resulting in bleeding). We hypothesised that victims of cannibalism have discernible morphological traits that predispose them to cannibalistic attack. We predicted that victims would have smaller skeletal traits (body length, ulna length, metatarsus length and width, toe length), lower body weight, poorer body condition, smaller combs and more asymmetrical bilateral skeletal traits than their flock mates. Contrary to our prediction, victims of cannibalistic attacks to the head/neck area ( N =23) tended to have larger combs than their flock mates (Wilcoxon matched-pairs signed-ranks test, S =59, P =0.037, NS after sequential Bonferroni adjustment). Their cannibals were more asymmetrical than non-cannibalistic bystanders (metatarsus length, S =48, P =0.011 and composite asymmetry, S =62.5, P =0.002, significant after sequential Bonferroni adjustment). In agreement with our prediction, victims of cannibalistic attacks to other body parts ( N =27), including the back, wings, rump, tail, cloaca, abdomen and toes, were more asymmetrical (composite asymmetry, S =78, P =0.022, significant after sequential Bonferroni adjustment) and tended to have lower body weights ( S =79.5, P =0.029, NS after sequential Bonferroni adjustment) than their flock mates. Their cannibals did not differ in skeletal or ornamental traits from the non-participating bystanders. The results suggest that large combs either elicit attacks to the head and neck area or increase vulnerability to injury during such attacks. Attacks to other body parts appear to be directed towards birds with signs of weakness relative to their flock mates. In these attacks, there were no distinguishing features separating cannibals from bystanders, suggesting that the bystanders could all be potential cannibals.

A note on aggression and cannibalism in laying hens following re-housing and re-grouping

Abstract We examined effects of being moved and mixed with strangers on the incidence of aggression and cannibalism in caged White Leghorn hens with intact beaks. We predicted that mixing of strangers would increase rates of aggression and cannibalism. Hens were reared in 16 stable groups of four birds together since hatch. At 18 months of age, eight groups were moved intact to new cages (unmixed). The remaining hens were moved to new cages and combined into eight new groups of four unfamiliar hens (mixed). Data on aggression and cannibalism were collected during the 7 months before and after mixing. Aggression was higher in mixed than unmixed groups during the first week after mixing. By contrast, the frequency of aggression in unmixed groups was depressed on the day of moving but returned to pre-moving levels within 1 week. Contrary to our prediction, mixing with strangers had no effect on cannibalism. However, the incidence of cannibalism was altered during the first month after moving hens to new cages, being higher than pre-moving levels for injuries to the head and neck and lower for injuries to other body parts.

Barking pigs: differences in acoustic morphology predict juvenile responses to alarm calls

Alarm calls given by adults and juveniles sometimes elicit different responses in receivers, with the alarm calls of adults being more provocative than those of juveniles. We examined this possibility in the domestic pig, Sus scrofa domesticus . We hypothesized that alarm barks given by adults and juveniles would differ acoustically, and that weaned juvenile pigs would respond more strongly to the barks of adult sows than they would to the barks of peers. In support of our hypothesis, we found that the barks of adult sows were louder and had lower values for peak frequency parameters than those of juveniles. We conducted a playback experiment and found that juvenile pigs responded as if the barks of unfamiliar sows were more alarming than the barks of unfamiliar juvenile pigs or ambient noise (control sound), even after controlling for playback volume. We conclude that differences in acoustic morphology enable domestic pigs to discriminate between barks of adult sows and juveniles, with the former evoking a stronger response.

Computer-aided method for calculating animal configurations during social interactions from two-dimensional coordinates of color-marked body parts.

In an experiment investigating the impact of preweaning social experience on later social behavior in pigs, we were interested in the mutual spatial positions of pigs during paired social interactions. To obtain these data, we applied a different colored mark to the head and back of each of 2 pigs per group and videotaped the pigs’ interactions. We used the EthoVision tracking system to providex,y coordinates of the four colored marks every 0.2 sec. This paper describes the structure and functioning of a FoxPro program designed to clean the raw data and use it to identify the mutual body positions of the 2 animals at 0.2-sec intervals. Cleaning the data was achieved by identifying invalid data points and replacing them by interpolations. An algorithm was then applied to extract three variables from the coordinates: (1) whether the two pigs were in body contact; (2) the mutual orientation (parallel, antiparallel, or perpendicular) of the two pigs; and (3) whether the pig in the “active” position made snout contact in front of, or behind, the ear base of the other pig. Using these variables, we were able to identify five interaction types: Pig A attacks, Pig B attacks, undecided head-to-head position, “clinch” resting position, or no contact. To assess the reliability of the automatic system, a randomly chosen 5-min videotaped interaction was scored for mutual positions both visually (by 2 independent observers) and automatically. Good agreement was found between the data from the 2 observers and between each observer’s data and the data from the automated system, as assessedusing Cohen’s kappa coefficients.

Consumption of alcohol by sows in a choice test.

The domestic pig (Sus scrofa domesticus) has been proposed as an animal model for human alcoholism because pigs have been observed to consume alcohol voluntarily to a state of intoxication and to exhibit tolerance and physical dependence. However, it has not been established whether pigs can develop psychological dependence on alcohol. We hypothesised that feed-restricted, stall-housed pregnant sows fed alcohol non-voluntarily for 5 weeks would develop a preference for alcohol and retain this preference after removal of alcohol from the diet. We fed crossbred commercial sows (n=10) 280 ml of 95% ethanol mixed with 0.91 kg of feed and 720 ml of water twice daily for 5 weeks during the first trimester of pregnancy. Control sows (n=7) received dextrose in their feed as a caloric control, and water was added to give the feed a consistency similar to that of the alcohol-treated feed. Immediately before and after 5 weeks of alcohol or dextrose treatment and 3 weeks later, after termination of alcohol or dextrose treatment, we evaluated sow diet preference by comparing the amount of alcohol-supplemented, dextrose-supplemented and plain feed consumed during a 5-min choice test. Contrary to our hypothesis, there was no treatment effect on sow diet preference. Both alcohol-treated and control sows ate less of the alcohol diet than the other two diets in all choice tests. They did not discriminate between the plain and dextrose diets. We conclude that 5 weeks of non-voluntary consumption of alcohol in feed did not produce a preference for alcohol in pregnant sows, either during treatment or after withdrawal, thus providing no evidence for the development of psychological dependence on alcohol under these conditions.