Research

Since 2000, Dr. Davis has led an integrated research program on the behavioral ecology of sea otters in Prince William Sound, Alaska, with Simpson Bay as a focal natural area. This work has progressed from detailed field studies to synthetic treatments, where Dr. Davis and colleagues framed sea otters as marine specialists but diet generalists whose foraging, reproductive behavior, and maternal strategies are tightly constrained by extreme energetic demands and nearshore habitat structure (Davis and Bodkin 2021; Pearson and Davis 2021; Cortez and Davis 2021).

At the foraging level, his program has shown that sea otters are durophagous predators that locate epibenthic and infaunal invertebrates by combining tactilely guided forepaw search with underwater vision during short, shallow dives that are usually <30 m and ~2 min in duration, close to their aerobic dive limit (Wolt et al. 2012; Davis and Bodkin 2021). In Simpson Bay, males and females exploit nearly the full bathymetric range but preferentially forage in 5–15 m water over soft and mixed sediments, where clams dominate the diet and foraging success averages ~87% (Wolt et al. 2012). Time-budget and energetic analyses showed that adult males devote only ~14% of the day to foraging, yet require a daily food intake of ~30% of body mass to meet energetic demands (Finerty et al. 2009). Comparable analyses of females with dependent pups indicate similarly high energetic costs, with daily clam intake approaching ~29% of body mass in early lactation (Wolt et al. 2014; Cortez et al. 2016a,b). These findings demonstrate that even in a food-replete system, sea otters operate near the upper limits of their metabolic capacity, and they contributed centrally to the book’s broader treatment of how carrying capacity, prey depletion, and individual specialization modulate foraging effort and diet across the North Pacific (Davis and Bodkin 2021). Complementary work on females and pups quantified the costs of reproduction in an altricial mammal that gives birth at sea. Using continuous focal follows and activity–energy budgets, Dr. Davis and colleagues showed that neonatal pups are entirely dependent: during the first month they rest and nurse >90% of the day, while females devote ~50% of their time to resting with the pup on their abdomen, ~13% to pup grooming, and only ~9% to foraging (Cortez et al. 2016a,b). As pups grow from ~1.8 to ~5.8 kg over three months, they progressively develop swimming, self-grooming, and shallow diving, while females transition from relying on gestational energy reserves to full income breeding, increasing daily food intake to ~39% of body mass, and foraging up to one-third of the day. These results underpin the broader conclusion that females operate near the limits of their energetic capacity and that small reductions in prey availability or adverse weather can precipitate declines in maternal condition, pup abandonment, or early weaning (Cortez and Davis 2021).

Dr. Davis’s work has also clarified how resource defense polygyny shapes male sea otter reproductive behavior. Long-term observations and photo-identification in Simpson Bay revealed that adult males defend non-overlapping aquatic territories whose quality depends on size, shoreline configuration, accessibility, and prey-rich areas used by females, and that some males hold the same territory for multiple years with 16–34% interannual overlap (Pearson and Davis 2005; Pearson et al. 2006; Finerty et al. 2010). These territorial males invest substantial time in patrolling and aggressive defense while attempting to monopolize estrous females through short (~3-day) consortships involving frequent aquatic copulations, but provide no parental care—features explicitly linked to resource-defense systems in other marine carnivores (Pearson and Davis 2021).

As a capstone to this 20-year research program, Dr. Davis produced the first mechanistic estimate of sea otter carrying capacity in Simpson Bay by integrating two decades of population surveys with detailed measurements of prey availability and consumption (Davis et al. 2021). They found that the adult population has remained stable at ~110 otters (5.2 km⁻²) while consuming ~22% of annual bivalve biomass—an amount fully replaced each year based on clam age structure. The distribution of butter clams and stained macomas, which make up ~71% of total bivalve biomass, closely matched observed foraging patterns, confirming that prey resources are sufficient to support the long-term population. This integration of behavioral ecology, energetics, and prey dynamics demonstrates that sea otters in Simpson Bay have reached carrying capacity based on food availability.

Since 2000, Dr. Davis’s research has significantly deepened our understanding of sea otter natural history by showing how energetic demands and the constraints of nearshore habitats govern their foraging, reproductive behavior, and maternal strategies. His studies demonstrated that sea otters are highly efficient, tactile predators in soft-sediment systems; that territorial males use resource defense polygyny to monopolize receptive females; and that females rear altricial pups while operating near the limits of their metabolic capacity. Together, this work provides a detailed, integrative picture of how sea otters balance energy acquisition, reproduction, and pup care, and how these processes shape population dynamics in coastal ecosystems.