Ecological correlates of blue whale movement behavior and its predictability in the California Current Ecosystem during the summer-fall feeding season

• Published in: Movement Ecology
• Main Authors: Daniel M. Palacios, Helen Bailey, Elizabeth A. Becker, Steven J. Bograd, Monica L. DeAngelis, Karin A. Forney, Elliott L. Hazen, Ladd M. Irvine, Bruce R. Mate
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2019
• Subjects: Satellite telemetry; State-space models; Movement behavior; Foraging behavior; Nonparametric multiplicative regression; Blue whale; Biology (General); QH301-705.5; Balaenoptera musculus
• Online Access: https://doi.org/10.1186/s40462-019-0164-6; https://doaj.org/article/aed75db1f1e04e14943c81ebaba1709f

Abstract Background Species distribution models have shown that blue whales (Balaenoptera musculus) occur seasonally in high densities in the most biologically productive regions of the California Current Ecosystem (CCE). Satellite telemetry studies have additionally shown that blue whales in the CCE regularly switch between behavioral states consistent with area-restricted searching (ARS) and transiting, indicative of foraging in and moving among prey patches, respectively. However, the relationship between the environmental correlates that serve as a proxy of prey relative to blue whale movement behavior has not been quantitatively assessed. Methods We investigated the association between blue whale behavioral state and environmental predictors in the coastal environments of the CCE using a long-term satellite tracking data set (72 tagged whales; summer-fall months 1998–2008), and predicted the likelihood of ARS behavior at tracked locations using nonparametric multiplicative regression models. The models were built using data from years of cool, productive conditions and validated against years of warm, low-productivity conditions. Results The best model contained four predictors: chlorophyll-a, sea surface temperature, and seafloor aspect and depth. This model estimated highest ARS likelihood (> 0.8) in areas with high chlorophyll-a levels (> 0.65 mg/m3), intermediate sea surface temperatures (11.6-17.5 °C), and shallow depths (< 850 m). Overall, the model correctly predicted behavioral state throughout the coastal environments of the CCE, while the validation indicated an ecosystem-wide reduction in ARS likelihood during warm years, especially in the southern portion. For comparison, a spatial coordinates model (longitude × latitude) performed slightly better than the environmental model during warm years, providing further evidence that blue whales exhibit strong foraging site fidelity, even when conditions are not conducive to successful foraging. Conclusions We showed that blue whale behavioral ...