Economical defence of resources structures territorial space use in a cooperative carnivore

Ecologists have long sought to understand space use and mechanisms underlying patterns observed in nature. We developed an optimality landscape and mechanistic territory model to understand mechanisms driving space use and compared model predictions to empirical reality. We demonstrate our approach using grey wolves ( Canis lupus ). In the model, simulated animals selected territories to economically acquire resources by selecting patches with greatest value, accounting for benefits, costs and trade-offs of defending and using space on the optimality landscape. Our approach successfully predicted and explained first- and second-order space use of wolves, including the population's distribution, territories of individual packs, and influences of prey density, competitor density, human-caused mortality risk and seasonality. It accomplished this using simple behavioural rules and limited data to inform the optimality landscape. Results contribute evidence that economical territory selection is a mechanistic bridge between space use and animal distribution on the landscape. This approach and resulting gains in knowledge enable predicting effects of a wide range of environmental conditions, contributing to both basic ecological understanding of natural systems and conservation. We expect this approach will demonstrate applicability across diverse habitats and species, and that its foundation can help continue to advance understanding of spatial behaviour.

Evidence of economical territory selection in a cooperative carnivore

As an outcome of natural selection, animals are probably adapted to select territories economically by maximizing benefits and minimizing costs of territory ownership. Theory and empirical precedent indicate that a primary benefit of many territories is exclusive access to food resources, and primary costs of defending and using space are associated with competition, travel and mortality risk. A recently developed mechanistic model for economical territory selection provided numerous empirically testable predictions. We tested these predictions using location data from grey wolves ( Canis lupus ) in Montana, USA. As predicted, territories were smaller in areas with greater densities of prey, competitors and low-use roads, and for groups of greater size. Territory size increased before decreasing curvilinearly with greater terrain ruggedness and harvest mortalities. Our study provides evidence for the economical selection of territories as a causal mechanism underlying ecological patterns observed in a cooperative carnivore. Results demonstrate how a wide range of environmental and social conditions will influence economical behaviour and resulting space use. We expect similar responses would be observed in numerous territorial species. A mechanistic approach enables understanding how and why animals select particular territories. This knowledge can be used to enhance conservation efforts and more successfully predict effects of conservation actions.

Prey, management and landscape requirements of an endangered population of the Woodlark Lullula arborea in Southwest Germany

Vineyards can be valuable habitats for biodiversity conservation. For example, in Rhineland-Palatinate (Germany) over a third of the state’s critically endangered Woodlark (Lullula arborea) population breeds in vineyards along the western margin of the Upper Rhine Valley. We here aim to elucidate how local ground cover management, food availability and the proximity to settlements affect territory selection by this bird species in the region. As climate, site conditions and management differ greatly from more continental or Mediterranean wine-growing areas, conditions for Woodlark conservation may differ as well.We compared 26 Woodlark territories in vineyards with 26 nearby reference areas from which Woodlarks were absent. We recorded vineyard ground cover in the inter-rows (% cover) as well as vegetation height and composition (forbs vs. grasses). Arthropods were sampled using pitfall traps, since they are the main food resource of Woodlarks during the breeding season. In addition, the distance to built-up areas was measured. The vegetation in Woodlark territories was shorter (mean 14.2 vs. 19.6 cm) and more dominated by forbs (39% vs. 27% cover) than in absence areas. The vegetation cover in the inter-rows had no effect on Woodlark territory presence or absence. Woodlarks also favoured areas with a higher abundance of arthropods (mean abundance 69.1 vs. 57.5) and a greater distance to built-up areas (mean distance 554 vs. 373 m). We conclude that to promote the Woodlark in wine-growing areas, short, forb-rich swards should be created, facilitating arthropod detectability. This is likely to require low levels of nitrogen fertilization since fertilizers favour tall-growing grasses that outcompete forbs. Pesticide applications should be kept at a minimum to enhance arthropods as the main food source for Woodlarks and their chicks. In addition, the expansion of settlements into breeding areas of Woodlarks should be avoided.

Advantages of social skills for contest resolution

Animal contests are natural interactions that occur to obtain or defend resources such as food and territory. Selection should favour individuals that can win contests with minimal costs in terms of energy expenditure or injuries. We hypothesized that social skills contribute to animals' assessment abilities in a contest situation and thereby will shorten contest duration. Animals were either raised in early life conditions stimulating the development of social skills, termed socialization or not (control). Contests between 342 pigs at eight weeks old (171 dyads) were studied for opponent assessment ability (using a game theoretical approach), examining duration and escalation, social behaviours performed, injuries and outcome. Contesting dyads were from the same treatment group and varied in body weight, a validated measure of resource holding potential (RHP). Socialized animals had shorter contests that were resolved with fewer injuries and they showed more ritualized display behaviour, consistent with mutual assessment. Furthermore, there was evidence of a novel form of opponent assessment in the socialized group revealed by a positive relationship between winner RHP and fight duration. In conclusion, social skills enabled more rapid establishment of dominance relationships at lower cost. Besides its evolutionary relevance, these findings may also contribute towards improving animal welfare.

Non-adaptive territory selection by a bird with exceptionally long parental care

High-quality territories are expected to provide greater fitness return for breeding individuals and, thus, are likely to have higher long-term occupation rate in comparison to low-quality territories. However, if environmental and ecological cues used for territory selection cannot reliably predict true territory quality, a mismatch between preferences and fitness may occur. We suggest that this kind of non-adaptive territory selection is more likely in species with long reproductive cycles, as a long time interval between territory establishment and young fledgling should reduce predictability of conditions during the critical stages of brood care. In this study, we investigated adaptiveness of territory selection in a migratory bird with exceptionally long parental care, the mute swanCygnus olor, which requires over four months to complete the entire reproductive cycle from egg laying to young fledging. For this purpose, we collected information on the long-term (10–19 years) occupancy of 222 swan breeding territories and correlated it with reproductive performance (n = 1,345 breeding attempts) and body condition of breeding adults. We found that long-term occupancy positively correlated with the timing of breeding, suggesting that individuals settled earlier in the attractive, frequently occupied territories. By contrast, we found no relationship between territory occupancy and reproductive output (hatching and fledging success) or adult body condition. The results indicate that at the time of territory selection swans might not be able to reliably assess territory quality, likely due to: (1) exceptionally long period of parental care, which reduces temporal correlation between the conditions at the time of territory selection and conditions during chick rearing; and (2) unpredictability of human-related activities that had a major impact on reproductive output of swan pairs in our population.