Are head cues necessary for goats (Capra hircus) in recognising group members?

In this study, we investigated whether goats can distinguish a member of their own group from one belonging to a different group even when the head of the goat in question cannot be seen. In the experiment, a total of 45 adult female goats (walkers) were trained to walk along a passageway at the end of which they learnt to expect food (trial run). Walking down this corridor, they passed another adult female goat (stimulus goat) whose trunk and hind legs alone were visible. Using 19 individuals, ten pairs of stimulus goats consisting of one goat from the walker's group and one from a different group were matched in terms of body size, constitution, colour and coat length. In addition, the stimulus goat from the same group as the walker had to be higher ranking than the latter to avoid being attacked. The walkers completed two, four or six trial runs depending on the number of pairs suitable for a given walker. The walker's exploratory behaviour (observing and sniffing at the stimulus goat) was recorded. Data from 109 trial runs were analysed using generalised linear mixed-effects models with crossed random effects. On average, the walker spent a total of 8.7 s exploring the stimulus goat visually and olfactorily if the latter was from a different group and only about half as long (4.2 s) if it was from her own group. In particular, the time a walker spent observing a stimulus goat whilst approaching the latter was significantly longer if the stimulus goat belonged to a different group than to her own (2.5 s as opposed to 1.4 s). Moreover, a stimulus goat from a different group was sniffed at significantly longer (4.6 s) than one from the same group (1.9 s). Results suggest that goats can easily discriminate between members of their own group and those of a different group even when the latter's heads are hidden. Olfactory and visual cues are probably important for identifying group members.

Cardiac activity in dairy goats whilst feeding side-by-side at two different distances and during social separation.

When loose-housed dairy goats feed in close proximity to each other, frequent social conflicts are often reported. The aim of this study was to investigate whether the cardiac activity of dairy goats is affected when they are obliged to feed side-by-side in close proximity. In five dyads of goats each stemming from eight groups (8x5 dyads) differing in terms of grouping age and presence of horns, heart rate (HR) and root mean square of successive beat-to-beat differences (RMSSD) as a parameter of heart-rate variability were measured in two experimental situations differing in distance during feeding. Dyads were allowed to feed for 5 min at two hayracks set-up side-by-side at a "far" or a "near" distance. Before goats were exposed to these test situations, baseline values of cardiac activity were measured. The differences of the baseline and test values (Delta) for HR and RMSSD were used for statistical analysis with linear mixed-effects models with crossed random effects. They were tested for dependence on feeding distance, rank within the group, dyadic rank relationship, grouping age, and presence of horns. In addition, cardiac activity was measured in a social-separation experiment conducted with the same goats. Baseline cardiac activity depended on the goat's rank within the group, with higher/lower levels of RMSSD/HR found in high-ranking than in low-ranking goats. In the feeding experiment, a significant interaction (feeding distance*rank within group, p=0.01) was found for Delta RMSSD: Low-ranking goats had lower Delta values at the far than at the near feeding distance. By contrast, high-ranking goats had lower Delta values at the near than at the far distance. In the separation experiment, Delta HR increased significantly compared to the feeding experiment (p<0.05), whereas Delta RMSSD did not differ significantly. Our results show that cardiac response is context-specific in dairy goats (feeding vs. separation), and that the individual's rank within the group must be taken into account in any future studies of their cardiac activity.