Marine Biology

Hypothesis

Climate-driven collapse of Arctic copepod and amphipod populations is triggering a maladaptive navigation response in gray whales (Eschrichtius robustus), causing them to deviate from ancestral migration routes and enter high-risk coastal zones (e.g., San Francisco Bay) where they suffer elevated mortality from ship strikes, predation, and starvation.

Mechanism

Gray whales rely on chemosensory cues (krill/copepod density gradients) and geomagnetic landmarks established over evolutionary timescales. As Arctic food sources collapse due to warming and sea ice loss:

1. Sensory mismatch: Whales fail to detect expected prey density peaks, disrupting route-initiation signals
2. Desperation feeding: Whales enter alternative coastal basins seeking secondary prey (small fish, benthic amphipods)
3. Ecological trap: Coastal areas offer brief nutritional gains but impose lethal predation/collision risks that exceed migratory benefits

Testable Predictions

• Whales entering San Francisco Bay show depleted blubber reserves and elevated stress hormones (cortisol, CRH) compared to whales completing traditional routes
• Genetic analysis of stranded whales reveals reduced ROBO1 and CRY1 expression (navigation-associated genes) in individuals that deviated from traditional routes
• Satellite tagging of diverted whales shows shorter inter-dive intervals and increased surface time, indicating active prey search behavior
• Mortality risk in Bay entrants is >3× higher than traditional migrants, but is offset by temporary caloric gains in spring months

Known Limitations

• Sample sizes for stranded whale necropsies remain small; larger datasets needed
• Chemosensory cue mechanisms in cetaceans are poorly characterized
• Alternative hypotheses (magnetic anomalies, ship noise disruption) remain plausible and untested

Broader Implications

This pattern may generalize to other migratory megafauna (caribou, wildebeest, sea turtles) experiencing climate-driven food-web disruption, suggesting a widespread phenomenon of "ecological desperation navigation" in response to anthropogenic environmental change.