Humpback whales use entire ocean basins as their habitat, moving thousands of kilometers each season between feeding and breeding grounds. Because these animals have such large ranges, researchers often use satellite tagging to monitor the movements of individuals over the course of weeks or months. These tags are deployed at close range with an air gun, which propels the metal tag and anchors it into the whale’s blubber. The tags transmit location information each time the tagged animals surface to breathe, giving researchers valuable insight into the animal’s movement patterns over time. 

Dr. Botero-Acosta and her colleagues at the Bio-telemetry and Behavioral Technology lab conducted two different satellite tagging operations in Monterey Bay: one in spring 2024 to study humpback whale movement patterns during the feeding season and one in the fall of the same year to track the migration to their Mexican breeding grounds. 

In April, 2024, satellite tags were deployed to track the foraging and movement patterns of five humpback whales found in Monterey Bay. These patterns varied considerably among individuals. Some whales traveled broadly, while others remained relatively centralized; some stayed near the coast, while others moved far offshore. One clear pattern emerged: foraging occurs primarily on continental shelf waters and within the boundaries of the Monterey Bay National Marine Sanctuary, a federally protected marine area along California’s central coast that prohibits activities like oil drilling, ocean dumping, and seabed mining within its boundaries. However, overlaying this with ship traffic data shows that the protected areas are heavily trafficked by cargo and tanker vessels, raising concerns about ship strikes and noise pollution. Currently, the most effective means for minimizing the risk of ship strikes is through voluntary measures from the industry to reduce speed. The most promising and established program currently active is the Blue Whales and Blue Skies initiative led by the California Marine Sanctuary Foundation.

During the fall operation, a second set of satellite tags was deployed six months later to map the migration route of humpback whales from California to their breeding grounds in Mexico. While the destinations of their migrations are well-known, the routes the whales take are not. In contrast to the patterns observed during the feeding season, when migrating, the whales followed a fairly uniform path, moving swiftly within the narrow continental shelf to reach the breeding grounds.  

This information on their migratory corridors is essential for conservation and management planning as it can now be used to better quantify where and to what extent migrating whales overlap with activities such as industrial-scale fishing, large-vessel shipping, and chemical runoff from agriculture. The data about when and how whales navigate areas like the Port of Los Angeles and the adjoining Port of Long Beach, which have some of the highest incidences of ship strikes, can inform marine area management and aid in the establishment of new marine sanctuaries with more effective restrictions on human activity. 

Historically, conservation efforts have focused on the end points of whale migration: breeding and feeding grounds. However, migratory corridors and pathways are critical for the survival and recovery of these animals and may pose even greater risks to the animals because they include such large areas, a myriad of poorly known threats, and various levels of protection.