Webinar: Climate change induced resource synchronization disrupts Kodiak brown bear and salmon food webs

Climate change is altering the seasonal timing of life-cycle events in organisms across the planet, but the magnitude of change often varies among taxa. This can cause the temporal relationships among species to change, altering the strength of interaction. A large body of work has explored what happens when co-evolved species shift out of sync, but virtually no studies have documented the effects of climate-induced synchronization, which could remove temporal barriers between species and create novel interactions. We explored how a predator, the Kodiak brown bear (Ursus arctos middendorffi), responded to asymmetric phenological shifts between its primary trophic resources, sockeye salmon (Oncorhynchus nerka) and red elderberry (Sambucus racemosa). In years with anomalously high spring air temperatures, elderberry fruited several weeks earlier and became available during the period when salmon spawned in tributary streams. Bears departed salmon spawning streams, where they typically kill 25-75% of the salmon, to forage on berries on adjacent hillsides. This prey switching behavior attenuated an iconic predator-prey interaction and likely altered the many ecological functions that result from bears foraging on salmon. We documented how climate-induced shifts in resource phenology can alter food webs through a mechanism other than trophic mismatch. The current emphasis on singular consumer-resource interactions fails to capture how climate-altered phenologies reschedule resource availability and alter how energy flows through ecosystems.