Influence of wind on movement behaviour in Arctic grizzly bears

Odours are emitted from organic matter and can contain important information about an animal's surroundings, including the presence and location of other organisms. Wind acts as a conduit of olfactory information, affecting the spread and direction of odour dispersal across terrestrial landscapes. To increase the likelihood of detecting an odour molecule, individuals may exhibit anemotaxis - orientation bias to wind during movement - where the theoretical optimal olfactory search strategy is to move crosswind. We tested for biased movement relative to wind in Arctic grizzly bears (Ursus arctos) during the spring hypophagic period in the Mackenzie Delta, Northwest Territories, Canada using modelled winds and satellite-linked telemetry data (n = 12,430 locations) from 40 Arctic grizzly bears monitored between 2003 and 2010. Our results show that orientation relative to wind varied with movement rate, a proxy for active search effort. During steps where bears had high movement rates (> 90th percentile), bears predominantly oriented crosswind. We also found a positive relationship between movement rate and crosswind orientation: as bears moved faster, they increased their crosswind component of orientation. These results suggest an adaptive pattern of movement in response to wind, where bears oriented relative to the wind in a way that increased the likelihood of odour detection during active search. We suggest that future studies could include wind data in habitat selection and foraging models to examine its influence on habitat selection and use.

The environment to the rescue: can physics help predict predator-prey interactions?

Understanding the factors that determine the occurrence and strength of ecological interactions under specific abiotic and biotic conditions is fundamental since many aspects of ecological community stability and ecosystem functioning depend on patterns of interactions among species. Current approaches to mapping food webs are mostly based on traits, expert knowledge, experiments, and/or statistical inference. However, they do not offer clear mechanisms explaining how trophic interactions are affected by the interplay between organism characteristics and aspects of the physical environment, such as temperature, light intensity or viscosity. Hence, they cannot yet predict accurately how local food webs will respond to anthropogenic pressures, notably to climate change and species invasions. Herein, we propose a framework that synthesises recent developments in food-web theory, integrating body size and metabolism with the physical properties of ecosystems. We advocate for combination of the movement paradigm with a modular definition of the predation sequence, because movement is central to predator-prey interactions, and a generic, modular model is needed to describe all the possible variation in predator-prey interactions. Pending sufficient empirical and theoretical knowledge, our framework will help predict the food-web impacts of well-studied physical factors, such as temperature and oxygen availability, as well as less commonly considered variables such as wind, turbidity or electrical conductivity. An improved predictive capability will facilitate a better understanding of ecosystem responses to a changing world.

Understanding Trophic Interactions in a Warming World by Bridging Foraging Ecology and Biomechanics with Network Science

Climate change will disrupt biological processes at every scale. Ecosystem functions and services vital to ecological resilience are set to shift, with consequences for how we manage land, natural resources, and food systems. Increasing temperatures cause morphological shifts, with concomitant implications for biomechanical performance metrics crucial to trophic interactions. Biomechanical performance, such as maximum bite force or running speed, determines the breadth of resources accessible to consumers, the outcome of interspecific interactions, and thus the structure of ecological networks. Climate change-induced impacts to ecosystem services and resilience are therefore on the horizon, mediated by disruptions of biomechanical performance and, consequently, trophic interactions across whole ecosystems. Here, we argue that there is an urgent need to investigate the complex interactions between climate change, biomechanical traits, and foraging ecology to help predict changes to ecological networks and ecosystem functioning. We discuss how these seemingly disparate disciplines can be connected through network science. Using an ant-plant network as an example, we illustrate how different data types could be integrated to investigate the interaction between warming, bite force, and trophic interactions, and discuss what such an integration will achieve. It is our hope that this integrative framework will help to identify a viable means to elucidate previously intractable impacts of climate change, with effective predictive potential to guide management and mitigation.

Something in the wind: the influence of wind speed and direction on African lion movement behavior

Olfaction is a key sense, enabling animals to locate forage, select mates, navigate their environment, and avoid predation. Wind is an important abiotic factor that modulates the strength of olfactory information detected by animals. In theory, when airflow is unidirectional, an animal can increase odor detection probability and maximize the amount of olfactory information gained by moving crosswind. Given energetic costs inherent to activity and locomotion, behavioral search strategies that optimize the benefit-cost ratio should be advantageous. We tested whether African lions (Panthera leo) modify their movement directionality and distance according to wind speed and direction during hours of darkness when they are most active. We tracked 29 lions in southern Zimbabwe using GPS collars and deployed a weather station to collect detailed abiotic data. We found that when wind speeds increased lions were more likely to move crosswind. We also found that female lions, which tend to hunt more often than males, traveled farther when wind speeds were stronger. The results of our analysis suggest that lions adjust their movement behavior according to wind speed and direction. We inferred that this was a behavioral decision to maximize the amount of olfactory information gained per unit of energy spent. Our findings not only offer one of the first detailed insights on large carnivore anemotaxis (movement direction relative to wind) but also make an important contribution towards understanding the influence of wind on predator ecology in general which remains understudied to date.