Slim pickings in safe areas

Posted on March 10, 2014

Prey species typically make use of refuge habitats to reduce the risk of predator attack. Although refuges offer clear survival advantages to prey, they’re not necessarily the best places to find food. How big a problem is this? American researchers examined the results of 170 refuge-related studies involving 233 distinct pairs of predator and prey species in aquatic (mainly freshwater) systems. Predators included species of fish, dragonflies, beetles, midges and rotifers, and prey included amphibians, water fleas, isopods and snails. Comparisons of data collected in the presence and absence of refuges revealed that refuge use significantly reduced the activity, growth rate and reproductive capacity (fecundity) of prey species. Of these indicators, prey activity was the least, and fecundity the most, affected.
Impacts on growth were intermediate, growth rates showing a steady downward trend as the refuge level increased from zero to total. Therefore, there was evidence from across a wide range of species of a clear trade-off between survival and production, which supports the idea that refuge availability can influence population dynamics and the transfer of energy through the food web. The authors note that human impacts, such as habitat destruction, climate change and invasions of exotic plants, can have profound effects on the quantity and quality of refuges, and therefore on freshwater ecology more broadly.

Reference: Orrock, J.L. et al. 2013. The cost of safety: refuges increase the impact of predation risk in aquatic systems. Ecology 94(3), 573–579.