Predation Risk and The Foraging Behavior of Competing Stream Insects

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. Invertebrates that graze periphyton growing on stones in coldwater streams in Michigan are at greatest risk of predation from a benthic-feeding fish (the mottled sculpin, Cottus bairdi) while on the top surface of substrates, where periphyton is most abundant, and during the day, when sculpin feed most actively. We conducted laboratory experiments with larvae of two strong exploitative competitors for periphyton (the mayfly Baetis tricaudatus and the caddisfly Glossosoma nigrior) to test if and how their foraging behavior was affected by presence of sculpin when sculpin were not allowed to attack prey. We incorporated four experimental factors in a factorial design: sculpin presence/absence, the abundance (low, high) of food that was patchily distributed on the top surface of substrates, grazer hunger level (fed, starved), and time of day (day, night).In feeding trials, Baetis was much more vulnerable than Glossosoma to sculpin predation. Similarly, only the foraging behavior of Baetis was strongly affected by the presence of sculpin. Baetis larvae responded to the presence of sculpin by: (1) significantly reducing the time spent on the top surface of substrates, and their movement rate while moving within and between food patches, and (2) significantly increasing the proportion of time spent in food patches, and the proportion of individuals that left the substrate by drifting downstream. Baetis larvae accepted greater risk of predation (by spending more time on top) when food abundance on top was high and when larvae had been starved for 27 h. Also, Baetis behavior was strongly affected by sculpin presence during the day but not at night. Collectively, these results suggest that Baetis larvae made adaptive compromises between feeding and avoiding sculpin. In contrast, Glossosoma behavior was not affected by the presence of sculpin. Glossosoma responded most strongly to alterations in food density and their own hunger level.Our results suggest that the presence of sculpin, even though the fish consumed no larvae, might indirectly affect the outcome of competitive interactions between Baetis and Glossosoma through the grazers' differential behavioral responses to the predator.

Diet of DippersCinclus cinclusduring an early winter spate and the possible implications for Dipper populations subjected to climate change

“…These latter two taxa are known to inhabit stone surfaces in shallow fast flowing water (Kohler & McPeek 1989, Scullion et al 1982. Even during spate the water in some marginal microhabitats may still be shallow enough for insects on stone surfaces to remain accessible to Dippers.…”

Glossossoma nigrior (Trichoptera: Glossosomatidae) respiration in moving fluid

“…Glossossoma nigrior larval behavior in the laboratory at the slower fluid flow velocities or in stagnant fluid may have been associated with drifting behavior in the field. Kohler and McPeek reported that drift increases at night because of casebuilding activity and associated vulnerability to erosion (Kohler and McPeek, 1989). However, under certain fluid flow conditions we observed that larvae arched their backs and extended their legs upward, behavior that would possibly increase the risk of larvae being swept up into the current.…”

“…The risk of predation by predominantly day-feeding sculpin was not a factor in Glossosoma positioning, but larval hunger level and food density were (Kohler and McPeek, 1989). Regarding food availability, G. nigrior inhabited fast riffles to exploit the diatoms that colonize siltfree surfaces (Scott, 1958).…”

Seasonal feeding selectivity of brown trout Salmo trutta in five groundwater-dominated streams

“…For example, other studies documented avoidance of Baetis by brown trout, despite being active and abundant in many streams (Mathooko 1996;Fochetti et al 2003;. Baetis has been documented to alter behavior in response to predation risk thereby reducing vulnerability to benthic feeding fish, including brown trout (Kohler and McPeek 1989).…”