Gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) throughout the year

This study provides novel information about gregariousness and intraspecific aggression in Iberian bullfinches (Pyrrhula pyrrhula iberiae) in northwestern Spain. Small monospecific parties never exceeding 10 individuals were seen throughout the year, larger in winter on average. Males considerably outnumbered females within the groups. Adult flocks were frequent only in winter. In spring, many of the adult groups were mixed-sex assemblages composed of pairs plus supernumerary males. Sightings of juvenile groups, up to seven individuals, were common in summer–autumn. The vigilance role in mixed-sex assemblages, including pairs, appeared to be the responsibility of males based on sex-specific vigilance rates. The highest frequency of aggressive encounters, mainly male against male, occurred during the breeding season, associated with mate defence. Females attacked males, not the contrary, which supports reversed sexual dominance in bullfinches. Gregariousness probably acted as an anti-predatory and foraging strategy.

Intraspecific facial bite marks in tyrannosaurids provide insight into sexual maturity and evolution of bird-like intersexual display

Intraspecific aggression, or agonism, is a widespread intrasexual selective behavior important to understanding animal behavioral ecology and reproductive systems. Such behavior can be studied either by direct observation or inferred from wound/scar frequency in extant species but is difficult to document in extinct taxa, limiting understanding of its evolution. Among extant archosaurs, crocodylians display extensive intrasexual aggression, whereas birds show extreme visual/vocal intersexual display. The evolutionary origin of this behavioral divergence, and pattern in non-avian dinosaurs, is unknown. Here we document the morphology, frequency, and ontogeny of intraspecific facial bite lesions (324 lesions) in a large sample of tyrannosaurids (202 specimens, 528 elements) to infer patterns of intraspecific aggression in non-avian theropods. Facial scars are consistent in position and orientation across tyrannosaurid species, suggesting bites were inflicted due to repeated/postured behavior. Facial scars are absent in young tyrannosaurids, first appear in immature animals (~50% adult skull length), are present in ~60% of the adult-sized specimens, and show aggressor:victim size isometry. The ontogenetic distribution of bite scars suggests agonistic behavior is associated with the onset of sexual maturity, and scar presence in approximately half the specimens may relate to a sexual pattern. Considered in a phylogenetic context, intraspecific bite marks are consistent and widely distributed in fossil and extant crocodyliforms and non-maniraptoriform theropods, suggesting a potential plesiomorphic behavior in archosaurs. Their absence in maniraptoriform theropods, including birds, may reflect a transition from boney cranial ornamentation and crocodylian-like intrasexual aggression to avian-like intersexual display with the evolution of pennaceous feathers.

Cost of a deprived environment – increased intraspecific aggression and susceptibility to pathogen infections

ABSTRACTA lack of environmental enrichment can be severely detrimental to animal welfare. For terrestrial species, including humans, barren environments are associated with reduced cognitive function and increased stress responses and pathology. Despite a clear link between increased stress and reduced immune function, uncertainty remains on how enrichment might influence susceptibility to disease. For aquatic vertebrates, we are only now beginning to assess enrichment needs. Enrichment deprivation in fish has been linked to increased stress responses, agonistic behaviour, physiological changes and reduced survival. Limited data exist, however, on the impact of enrichment on disease resistance in fish, despite infectious diseases being a major challenge for global aquaculture. Here, using a model vertebrate host–parasite system, we investigated the impact of enrichment deprivation on susceptibility to disease, behaviour and physiology. Fish in barren tanks showed significantly higher infection burdens compared with those in enriched enclosures and they also displayed increased intraspecific aggression behaviour. Infections caused hosts to have significantly increased standard metabolic rates compared with uninfected conspecifics, but this did not differ between enriched and barren tanks. This study highlights the universal physiological cost of parasite infection and the biological cost (increased susceptibility to infection and increased aggression) of depriving captive animals of environmental enrichment.

The frequency of body scarring in Caspian Whip Snakes (Dolichophis caspius Gmelin, 1789) in south-western Hungary

Animals can suffer injuries due to diseases, intraspecific aggression and, most of all, predation events. We present field data to provide numerical information about the injuries found in the largest Caspian Whip Snake (Dolichophiscaspius) population in Hungary, near the northernmost portion of the species’ distribution range.

The Human Animal

This chapter turns to the work of Konrad Lorenz. Primarily interested in the scientific study of animal behavior, Lorenz believed that understanding how and why animals behave the way they do would shed light on the predicament of human behavior and the problem of nuclear escalation. Whereas Ardrey had lumped together hunting, cannibalism, and murderous rage into a single entity that defined humanity, Lorenz carefully distinguished the hunger associated with the killing of other species for food (an interspecific behavior) from (intraspecific) aggression inherent to killing a member of one's own species. Hunters and warriors were not the same thing—and between them, Lorenz was interested in only the latter. One of the deepest intellectual splits between Ardrey and Lorenz concerned the timing and causality of man's relationship with tools of war: whereas Ardrey insisted that the accidental discovery of weapons drove our intellectual and social development as humans (the weapon made the man), Lorenz flipped these, asserting the far more commonly held belief that early humans self-consciously developed weapons as tools for hunting.