Phenological synchronization disrupts trophic interactions between Kodiak brown bears and salmon

Area of Science:

• Ecology
• Climate Change Biology
• Animal Behavior

Background:

• Climate change is shifting species' life cycle event timings globally.
• Asynchronous phenological shifts can alter species interactions and food web dynamics.
• Few studies examine climate-induced synchronization and its ecological consequences.

Purpose of the Study:

• To investigate how Kodiak brown bears (Ursus arctos middendorffi) respond to asymmetric phenological shifts in their key food resources: sockeye salmon (Oncorhynchus nerka) and red elderberry (Sambucus racemosa).
• To understand the ecological implications of climate-induced resource rescheduling on predator-prey interactions and food web structure.

Main Methods:

• Observational study documenting bear foraging behavior in relation to the phenology of salmon spawning and elderberry fruiting.
• Analysis of how variations in spring air temperatures influence the timing of resource availability.

Main Results:

• Anomalously high spring temperatures led to earlier elderberry fruiting, coinciding with salmon spawning periods.
• Kodiak brown bears shifted their diet, foraging on berries instead of salmon, thereby reducing predation on salmon.
• This prey switching attenuated a significant predator-prey interaction, impacting salmon populations and ecosystem functions.

Conclusions:

• Climate-induced phenological shifts can synchronize resource availability, leading to novel interactions and altered food web dynamics.
• The study highlights a mechanism beyond trophic mismatch through which climate change reshapes ecosystems.
• Understanding rescheduled resource availability is crucial for predicting climate change impacts on energy flow in ecosystems.