Escaping peril: perceived predation risk affects migratory propensity

Abstract

Although migratory plasticity is increasingly documented, the ecological drivers of plasticity are not well understood. Predation risk can influence migratory dynamics, but whether seasonal migrants can adjust their migratory behaviour according to perceived risk is unknown. We used electronic tags to record the migration of individual roach (Rutilus rutilus), a partially migratory fish, in the wild following exposure to manipulation of direct (predator presence/absence) and indirect (high/low roach density) perceived predation risk in experimental mesocosms. Following exposure, we released fish in their lake summer habitat and monitored individual migration to connected streams over an entire season. Individuals exposed to increased perceived direct predation risk (i.e. a live predator) showed a higher migratory propensity but no change in migratory timing, while indirect risk (i.e. roach density) affected timing but not propensity showing that elevated risk carried over to alter migratory behaviour in the wild. Our key finding demonstrates predator-driven migratory plasticity, highlighting the powerful role of predation risk for migratory decision-making and dynamics.

Winter activity of common bream (Abramis brama L.) in a European reservoir

“…Consistent with the "metabolic slowdown", outlined above is an increase in predation risk, prompting fish to shoal or seek out refuge habitats, for example smaller habitats in tributaries, to lower the risk (Bajer et al, 2011;Hulthén et al, 2015;Lian et al, 2017). (Lian et al, 2017), the increased aggregation during the day would also be consistent with reducing predation risk.…”

“…Species such as common bream Abramis brama (L.), roach Rutilus rutilus (L.), silver bream Blicca bjoerkna (L.) and rudd Scardinius erythrophthalmus (L.) have been frequently observed migrating out of lakes and into connecting rivers or streams in winter (e.g. Both aggregation (Bajer et al, 2011) and migration to specific refuge habitats (Hulthén et al, 2015;Jepsen & Berg, 2002) most likely represent predator defence strategies at a time when fish metabolism is greatly reduced due to cold temperatures and a lack of food. Both aggregation (Bajer et al, 2011) and migration to specific refuge habitats (Hulthén et al, 2015;Jepsen & Berg, 2002) most likely represent predator defence strategies at a time when fish metabolism is greatly reduced due to cold temperatures and a lack of food.…”

Habitat predicts local prevalence of migratory behaviour in an alpine ungulate

“…Studies accounting for population‐level differences in migratory prevalence remain relatively rare. In roach Rutilis rutilis , where partial migration is maintained as a conditional strategy, Hulthén et al () demonstrated that individual‐level migratory propensity increased in response to experimentally introduced cues of predation risk. This suggests that population‐level declines in migration may result from behavioural changes to perceived risk (rather than differential reproduction or mortality).…”

Divergence of developmental trajectories is triggered interactively by early social and ecological experience in a cooperative breeder

“…To concurrently simulate predation risk, we presented an L. elongatus twice weekly for 30 min visually and chemically to half of the rearing tanks (+P treatment), whereas the other half of experimental groups received nonpredator control cues (−P treatment; see SI Appendix for details on cue presentation). We used a predator-absence treatment as control for the +P treatment, because as for the earliest life stages of several other fish species (40,58), using "harmless" heterospecific fish to mimic a low-risk environment is not possible in N. pulcher. In nature, virtually every heterospecific represents a potential predation risk to N. pulcher young in their earliest life stage, and N. pulcher young respond by specific antipredator responses ("freezing") toward piscivore, herbivore, and conspecific cichlids (SI Appendix, Fig.…”