Roberto Bonanni

Free-ranging dogs assess the quantity of opponents in intergroup conflicts

In conflicts between social groups, the decision of competitors whether to attack/retreat should be based on the assessment of the quantity of individuals in their own and the opposing group. Experimental studies on numerical cognition in animals suggest that they may represent both large and small numbers as noisy mental magnitudes subject to scalar variability, and small numbers (≤4) also as discrete object-files. Consequently, discriminating between large quantities, but not between smaller ones, should become easier as the asymmetry between quantities increases. Here, we tested these hypotheses by recording naturally occurring conflicts in a population of free-ranging dogs, Canis lupus familiaris, living in a suburban environment. The overall probability of at least one pack member approaching opponents aggressively increased with a decreasing ratio of the number of rivals to that of companions. Moreover, the probability that more than half of the pack members withdrew from a conflict increased when this ratio increased. The skill of dogs in correctly assessing relative group size appeared to improve with increasing the asymmetry in size when at least one pack comprised more than four individuals, and appeared affected to a lesser extent by group size asymmetries when dogs had to compare only small numbers. These results provide the first indications that a representation of quantity based on noisy mental magnitudes may be involved in the assessment of opponents in intergroup conflicts and leave open the possibility that an additional, more precise mechanism may operate with small numbers.

Social variables affecting mate preferences, copulation and reproductive outcome in a pack of free-ranging dogs.

Mating and reproductive outcome is often determined by the simultaneous operation of different mechanisms like intra-sexual competition, mating preferences and sexual coercion. The present study investigated how social variables affected mating outcome in a pack of free-ranging dogs, a species supposed to have lost most features of the social system of wolves during domestication. We found that, although the pack comprised multiple breeding individuals, both male copulation success and female reproductive success were positively influenced by a linear combination of dominance rank, age and leadership. Our results also suggest that mate preferences affect mating outcome by reinforcing the success of most dominant individuals. In particular, during their oestrous period bitches clearly searched for the proximity of high-ranking males who displayed affiliative behaviour towards them, while they were more likely to reject the males who intimidated them. At the same time, male courting effort and male-male competition for receptive females appeared to be stronger in the presence of higher-ranking females, suggesting a male preference for dominant females. To our knowledge, these results provide the first clear evidence of social regulation of reproductive activities in domestic dogs, and suggest that some common organizing mechanisms may contribute to shape the social organization of both dogs and wolves.

The Social Organisation of a Population of Free-Ranging Dogs in a Suburban Area of Rome: A Reassessment of the Effects of Domestication on Dogs’ Behaviour

Domestication is thought to have reduced dogs’ ability to form organised packs with conspecifics. Here, we investigated the social organisation of a population of free-ranging dogs living in a suburban area of Rome. Almost all animals were not socialised to humans, although they subsisted on food provided by people, and lived in stable social groups whose organisation appeared more similar to that of wolves than previously reported. In all groups studied, a linear dominance hierarchy could be detected based on the directionality of submissive behaviour. Social regulation of reproductive activities was also observed. Affiliative relationships appeared to promote both leader–follower relationships and cooperation in conflicts against stranger packs. Larger packs outcompeted smaller ones in contests for food and space. A reduction in both cooperative breeding and territorial aggression relative to wolves can be reasonably interpreted as an adaptation to the domestic environment. We suggest that dogs are more likely to form stable packs when they are not socialised to humans and can subsist on abundant and clumped food resources.

Condition-Dependent Nocturnal Hypothermia in Garden Warblers Sylvia borin at a Spring Stopover Site

Migratory birds have evolved physiological and behavioural adaptations for crossing large ecological barriers through the accumulation of large amounts of fat and protein during the pre-migratory phase. Nevertheless, most migrant passerines usually need several stopovers en route to replenish their energy reserves and to rest. Migratory decisions at a stopover site strongly depend on body condition at arrival. Previous studies showed that lean birds prolong their stopover compared with fat birds that leave after a very short time. During the stopover, lean birds may reduce their metabolic costs by lowering body temperature (adaptive hypothermia hypothesis). However, it is not clear whether hypothermia can be an active economising strategy or just an unavoidable consequence of bad condition to avoid starvation. We used temperature loggers to measure skin temperature of 19 Garden Warblers Sylvia borin caught at a spring stopover site (Ponza Island, Tyrrhenian Sea) and kept overnight in cotton bags. We found that both body condition and activity were positively correlated with skin temperature during the night. The data showed a gradual nocturnal temperature drop of more than 3°C in lean birds, particularly in the central part of the night, followed by a recovery to normothermic levels. Overall, birds in worse physical condition lost more body mass during the night than birds in better condition, but this was especially true for birds that lowered their body temperature the least. These results indicate that hypothermia is associated with low body condition and that it may be functional by reducing body mass loss during migration.

Age-graded dominance hierarchies and social tolerance in packs of free-ranging dogs

Lay SummaryContrary to the view that social dominance is a wolf feature that was lost by dogs during domestication, we found that Italian free-ranging dogs live in packs with a stable membership and with a clear hierarchical social structure. Moreover, as in wolves and other cooperative animals in which group members rely on the guidance of experienced companions, high social status in dogs was mainly held by elders, and agonistic interactions were highly ritualized.