From the perspective of prey, movement synchrony can represent either a potent anti-predator strategy or a dangerous liability. Prey must balance the costs and benefits of using conspecifics to mediate risk and the emergent patterns of risk-driven sociality depends on the spatial variation and trait composition of the system. Our literature review outlined the prevailing, but not universal, trend of animals using sociality as an antipredator strategy. Empirically, we then used movement synchrony as a measure of social antipredator response of two ungulates to spatial variation in predator and prey habitat domains. We demonstrated that these responses vary based on prey vulnerability and predator hunting modes. Prey favored asynchrony when calves were present and within habitat domains of ambush predators but not pursuit predators. By unifying community ecology concepts such as habitat domains with movement ecology we provided a comprehensive evaluation of factors mediating prey social response to predation risk.

Resource selection analysis (RSA) is a cornerstone approach for understanding animal distributions, yet there exists no rigorous quantification of sample sizes required to obtain reliable results. We provide closed-form mathematical expressions for both the number of animals and relocations per animal required for parameterising RSA to a given degree of precision. Required sample sizes depend on just two quantities: habitat selection strength and an index of landscape complexity, which we define rigorously. We validate our solutions using 5,678,623 GPS locations from 511 animals from 10 species (omnivores, carnivores, and herbivores from boreal, temperate, and tropical forests, montane woodlands, swamps, and tundra). Our results contradict conventional wisdom by showing that environmental effects on distributions can often be estimated with fewer animals and relocations than assumed, with far-reaching implications for ecologists, conservationists, and natural resource managers.