Timing is everything: Drivers of interannual variability in blue whale migration.

Blue whales need to time their migration from their breeding grounds to their feeding grounds to avoid missing peak prey abundances, but the cues they use for this are unknown. We examine migration timing (inferred from the local onset and cessation of blue whale calls recorded on seafloor-mounted hydrophones), environmental conditions (e.g., sea surface temperature anomalies and chlorophyll a), and prey (spring krill biomass from annual net tow surveys) during a 10 year period (2008-2017) in waters of the Southern California Region where blue whales feed in the summer. Colder sea surface temperature anomalies the previous season were correlated with greater krill biomass the following year, and earlier arrival by blue whales. Our results demonstrate a plastic response of blue whales to interannual variability and the importance of krill as a driving force behind migration timing. A decadal-scale increase in temperature due to climate change has led to blue whales extending their overall time in Southern California. By the end of our 10-year study, whales were arriving at the feeding grounds more than one month earlier, while their departure date did not change. Conservation strategies will need to account for increased anthropogenic threats resulting from longer times at the feeding grounds

Using new tag attachments to study humpback whale fine-scale spatiotemporal dive behavior, habitat use, and reaction to ships off Northern California

Understanding the foraging behavior of humpback whales (Megaptera novaeangliae) is important for ethology and monitoring ecosystem-level health. Because humpback whales are generalist foragers, regional dive differences should reveal information about prey preference and availability. Any external influences of foraging behavior has important conservation implications because disruptions to foraging may impact individual fitness. From 2013 to 2014, I opportunistically tagged 22 humpback whales and 12 blue whales (Balaenoptera musculus) to test eight tag attachments, which were used to study the fine-scale dive behavior of humpback whales in four regions off California, and when they encountered ships. Four-barb tag configurations remained on the longest with no difference in reaction and no infection; however, some breakage occurred. Whales in Bodega Canyon and on the continental break/slope made deeper, longer foraging dives to feed on krill, while whales in Monterey Bay and on the continental shelf foraged in shallow waters on more fish species. Encounters between ships and whales showed changes to overall dive behavior depending on dive type, but responses varied. Whales, mostly juveniles and injured whales, were more at risk in the upper 50 m of the water column during the daytime. This study provided insight into how humpback whale dive behavior differenced among regions and how ship encounters affected dive behavior

Timing is everything: Drivers of interannual variability in blue whale migration.

Blue whales need to time their migration from their breeding grounds to their feeding grounds to avoid missing peak prey abundances, but the cues they use for this are unknown. We examine migration timing (inferred from the local onset and cessation of blue whale calls recorded on seafloor-mounted hydrophones), environmental conditions (e.g., sea surface temperature anomalies and chlorophyll a), and prey (spring krill biomass from annual net tow surveys) during a 10 year period (2008-2017) in waters of the Southern California Region where blue whales feed in the summer. Colder sea surface temperature anomalies the previous season were correlated with greater krill biomass the following year, and earlier arrival by blue whales. Our results demonstrate a plastic response of blue whales to interannual variability and the importance of krill as a driving force behind migration timing. A decadal-scale increase in temperature due to climate change has led to blue whales extending their overall time in Southern California. By the end of our 10-year study, whales were arriving at the feeding grounds more than one month earlier, while their departure date did not change. Conservation strategies will need to account for increased anthropogenic threats resulting from longer times at the feeding grounds

Blue whale call detections and determinations data from Context-dependent variability in blue whale acoustic behaviour

The 'BmCallDeterminations' workbook contains 42 tabs, each logging the occurrence of all blue whale calls detected from an individual deployment and used in the analysis based on caller determination. A more detailed description of the call data is included on the first tab

Blue whale dive profile analyses from Context-dependent variability in blue whale acoustic behaviour

The 'BmDiveProfileAnalyses' workbook contains 121 tabs, each describing the blue whale dives recorded from an individual deployment. A more detailed description of the dive profile data is included on the first tab

Blue whale GEE - R code from Context-dependent variability in blue whale acoustic behaviour

The R-code used to assess variability in blue whale call and phrase production rates using Generalized Estimating Equations (GEEs)

Supplemental Table: Tag Deployment Details from Context-dependent variability in blue whale acoustic behaviour

Deployment details for all tags deployed on blue whales between 2002 - 2016 with data used in this stud