Many marine mammal species are remarkably deep divers. Beaked whales, sperm whales, and elephant seals regularly dive to depths greater than 1 km, and some species, such as the Cuvier’s beaked whale, have been recorded at depths of 3 km on a single breath that lasted over two hours! We know very little about these species other than that they are diving to great depths to exploit unique food resources that are not available in other areas. Their foraging strategies, energy expenditure, and communication at depth are all mysteries that scientists seek to learn more about.
Marine mammals are difficult to study because they spend the majority of their lives underwater, and away from the surface where they are easily available for observation. There are two main techniques that scientists use to study marine mammals at depth: passive acoustic monitoring and archival tagging.
Passive acoustic monitoring is a simple system for detecting, monitoring, and sometimes localizing marine mammals at depth by recording their vocalizations with a hydrophone. Archival tags are small tags that are attached to the animal to record fine-scale movements (ex. direction, roll, pitch, speed) and environmental data for the surrounding water column including depth, temperature, and salinity. The data recorded by these two systems are complimentary, and as a result, are often collected at the same time to provide a wide breadth of information on animal behaviour.
Our colleagues at CREEM are experts in analyzing these types of data and have developed numerous techniques for calibrating and deploying these systems. Be sure to check out their most recent blog post on their approaches for tracking and modeling marine mammals in 3D.