Against the flow: chemical detection of downstream predators in running waters

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T1 - Against the flow: chemical detection of downstream predators in running waters

AU - Dahl, Jonas

AU - Nilsson, Anders

AU - Pettersson, Lars

PY - 1998

Y1 - 1998

N2 - In running waters, chemical cues have generally been assumed to always come from upstream locations. Here, we present ¢eld and laboratory evidence that Gammarus pulex can use chemical cues from down- stream predators to adaptively adjust drifting behaviour. In the ¢eld, signi¢cantly fewer Gammarus migrated into stream enclosures where brown trout (Salmo trutta) were present than into control enclo- sures. In a subsequent laboratory experiment, Gammarus actively avoided live trout and trout chemicals placed downstream in an arti¢cial stream, whereas no e¡ects were found in response to control or visual cues.We suggest that the mechanism explaining the ability of Gammarus to detect downstream predators is use of back£ows, which locally transport ¢sh chemicals against the main £ow. Such back£ows are both created by the Gammarus itself and by surrounding substrate heterogeneity. These results profoundly a¡ect the way in which we view the chemical environment of running waters and have important implications for empirical and theoretical work evaluating predator e¡ects in running waters, as they demonstrate that prey immigration rates can depend on downstream predator densities.

AB - In running waters, chemical cues have generally been assumed to always come from upstream locations. Here, we present ¢eld and laboratory evidence that Gammarus pulex can use chemical cues from down- stream predators to adaptively adjust drifting behaviour. In the ¢eld, signi¢cantly fewer Gammarus migrated into stream enclosures where brown trout (Salmo trutta) were present than into control enclo- sures. In a subsequent laboratory experiment, Gammarus actively avoided live trout and trout chemicals placed downstream in an arti¢cial stream, whereas no e¡ects were found in response to control or visual cues.We suggest that the mechanism explaining the ability of Gammarus to detect downstream predators is use of back£ows, which locally transport ¢sh chemicals against the main £ow. Such back£ows are both created by the Gammarus itself and by surrounding substrate heterogeneity. These results profoundly a¡ect the way in which we view the chemical environment of running waters and have important implications for empirical and theoretical work evaluating predator e¡ects in running waters, as they demonstrate that prey immigration rates can depend on downstream predator densities.

KW - chemical communication

KW - predator^prey interaction

KW - £uid dynamics

KW - drifting behaviour

KW - migration

KW - Gammarus pulex

U2 - 10.1098/rspb.1998.0439

DO - 10.1098/rspb.1998.0439

M3 - Article

VL - 265

SP - 1339

EP - 1344

JO - Royal Society of London. Proceedings B. Biological Sciences

T2 - Royal Society of London. Proceedings B. Biological Sciences

JF - Royal Society of London. Proceedings B. Biological Sciences

SN - 1471-2954

IS - 1403

ER -