Abstract: We present an experiment showing that New Caledonian crows are able to choose tools of the appropriate size for a novel task, without trial-and-error learning. This species is almost unique amongst all animal species (together with a few primates) in the degree of use and manufacture of polymorphic tools in the wild. However, until now, the flexibility of their tool use has not been tested. Flexibility, including the ability to select an appropriate tool for a task, is considered to be a hallmark of complex cognitive adaptations for tool use. In experiment 1, we tested the ability of two captive birds (one male, one female), to select a stick (from a range of lengths provided) matching the distance to food placed in a horizontal transparent pipe. Both birds chose tools matching the distance to their target significantly more often than would be expected by chance. In experiment 2, we used a similar task, but with the tools placed out of sight of the food pipe, such that the birds had to remember the distance of the food before selecting a tool. The task was completed only by the male, who chose a tool of sufficient length significantly more often than chance but did not show a preference for a matching length.

Abstract: An overview of mechanistic and functional accounts of stimulus generalisation is given. Mechanistic accounts rely on the process of spreading activation across units representing stimuli. Different models implement the spread in different ways, ranging from diffusion to connectionist networks. A functional account proposed by Shepard analyses the probabilistic structure of the world for invariants. A universal law based on one such invariant claims that under a suitable scaling of the stimulus dimension, generalisation gradients should be approximately exponential in shape. Data from both vertebrates and invertebrates so far uphold Shepard's law. Some data on spatial generalisation in honeybees are presented to illustrate how Shepard's law can be used to determine the metric for combining discrepancies in different stimulus dimensions. The phenomenon of peak shift is discussed. Comments on mechanistic and functional approaches to generalisation are given.

Abstract: The aim of this study was to investigate social behaviour in differently reared stallions in their respective environments; one group of stallions was reared under typical domestic conditions whereas the other group was reared and lives under natural conditions. The domestic group consisted of 19, 2-year-old stallions (Equus caballus), which were all weaned at 4 months of age and experienced either individual or group housing facilities before being pastured with the other similarly aged stallions. The natural living and mixed age group of Przewalski stallions (E. przewalskii) consisted of 13 stallions, most of which were juveniles (n=11, <=4 years; n=2, >9 years). The domestic group was studied in a 4-ha enclosure at the Danish Institute of Agricultural Sciences and the Przewalski group under free-ranging conditions in a 75-ha enclosure in the Askania Nova Biosphere Reserve, Ukraine. Behavioural data was collected during 168 h of direct observation. The occurrence of 14 types of social interactions was recorded and group spacing behaviour was studied using nearest neighbour recordings. In spite of very different environments, reflecting domestic and natural rearing conditions, many similarities in behaviour was found. Play and play fight behaviour was very similar in the two stallion groups. Quantitative differences were found in social grooming since Przewalski stallions groomed more frequently (P=0.004), and in investigative behaviours, since domestic stallions showed more nasal (P=0.005) and body sniffing (P<0.001), whereas Przewalski stallions directed more sniffing towards the genital region (P<0.001). These differences may, however, be attributed to environmental factors and in the period of time the stallions were together prior to the study period. Quantitative differences appeared in some agonistic behaviours (kick threat, P<0.001; and kick, P<0.001), but data do not support earlier findings of Przewalski horses being significantly more aggressive than domestic horses. In general, Przewalski stallions engaged in more social interactions, and they showed less group spacing, i.e. maintained a significantly shorter distance between neighbours (P<0.001). The study indicates that also domestic horses, which have been reared under typical domestic conditions and allowed a period on pasture, show social behaviour, which is very similar to that shown by their non-domestic relatives.

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.