Aggression is one of the most serious hazards to the welfare of captive animals, with the potential to cause pain, injury, and mortality. Physical enrichment (PE), defined as the provision of physical structures and objects such as shelters, is widely used to improve welfare, yet it can also facilitate aggression by creating defendable resources. This perspective integrates insights from behavioural ecology and animal welfare science to develop a conceptual framework for understanding how PE shapes aggression and well-being in captive animals. We propose that combining resource defence theory with detailed behavioural analysis provides a powerful tool to interpret how PE influences the expression of aggression and how it is distributed among performers and recipients within the group. We identify mechanisms through which specific attributes of enrichment (complexity, distribution, size, materials used, placement) may mitigate adverse welfare outcomes, including reducing contest intensity, providing opportunities for conflict avoidance, and diverting behavioural motivation away from direct competition. We conclude by proposing targeted experimental approaches to isolate the effect of specific enrichment attributes on behaviour and welfare. Applying this framework can inform the design of enrichment strategies that enable animals to express natural behaviours, including aggression, while minimising negative welfare outcomes.

Understanding the types of movements exhibited by a threatened species is paramount for creating conservation and management strategies. The Campo Miner (Geositta poeciloptera) is a threatened obligate grassland bird endemic to the South American Cerrado. Literature disagrees about its movement ecology, with authors suggesting strategies as contradictory as residency and nomadism. The species requires short and sparse grass cover to breed and seems to be associated with fires, tracking recently burned grassland patches. We studied the movement ecology of marked Campo Miners for seven years, integrating our results with information from citizen science data, museum specimens, and the literature. After investigating every main movement strategy exhibited by bird populations, we found no evidence of regular migration in the species (e.g. altitudinal, short- or long-distance). The Campo Miner is a resident species with territorial behaviour restricted to the breeding season, which apparently results in seasonal variation in its detectability, biasing our perception about its seasonal abundance and distribution. We propose a theoretical framework for understanding local movements in the species, which predicts that Campo Miners: (1) establish their territories at the beginning of the breeding season in patches of suitable habitat; (2) stop defending their territories after the breeding season; (3) stay during the non-breeding season in their home ranges, also wandering across neighbouring home ranges; (4) abandon their home ranges if the grass cover becomes high and dense or when a better quality habitat patch becomes available, using fires as a cue for locating recently burned patches that will soon

Male common chameleons Chamaeleo chamaeleon actively followed the female closely as a typical mate guarding behaviour during the mating season. Guarding behaviour and spatial organization were studied in 34 radio-tagged males in a population in southern Spain during three summers. Timing and extent of guarding were highly variable among males. Overall, guarding started on 16 August (range 28 July–5 September, n=34) and ended on 4 September (range 21 August–15 September, n=24) lasting 13.4 days (range 0–46 days, n=30). Males showed a polygynous serial-type mating system where males sequentially guarded (and mated) several females during the breeding season but only one at a time. The number of guarded females (mean 2.8, range 0–8, n=34) and number of mates per male (mean 0.7, range 0–3, n=34) were also highly variable among males. In general, guarding males abandoned the females soon after mating in association with clear signs that females were no longer receptive. Males showed a remarkably complex spatial organization in close association with the home range of guarded females. Guarding behaviour resulted in territorial behaviour, and ‘stable’ as well as ‘mobile’ territories were recorded. In ‘stable’ territories, males defended non-overlapping areas where the home range of one female or more was included. Although monogamy was the predominant mating system recorded in this population, social polygyny occurred in all study years. Polygynous groups were only feasible because females aggregated in small-sized areas without apparent symptoms of intrasexual competition. Breeding asynchrony of females seems to influence this complex mating system as more competitive (large) males mated with large (early reproducing) females and small (late reproducing) ones (cf. Cuadrado, 1999). Most aggressive interactions were male–male chasing of a solitary intruder by a guarding male. A removal experiment of guarding males revealed that newcomers were small-sized males, suggesting that an important fraction of males were acting as floaters searching for mating opportunities. Male characteristics (especially size and body weight) were the main factors influencing the spatial organization and the reproductive success of males in this population.