Researchers sink listening devices 1,100m deep off the Louisiana coast and hear the sounds of an elusive animal
Efforts to understand some of the ocean’s most elusive inhabitants – beaked whales – are gaining momentum thanks to a novel approach: listening. New research utilizing passive acoustic monitoring is providing unprecedented insight into the foraging behaviors of these rarely observed marine mammals.
The Challenge of Studying Beaked Whales
Beaked whales present a significant challenge to traditional study methods. According to Héloïse Frouin-Mouy, a bioacoustics expert at the University of Miami, these whales are “extreme deep divers that spend most of their lives at depth and surface only briefly, making them particularly challenging to study using traditional visual surveys or animal-borne tagging approaches.” This deep-diving lifestyle necessitates innovative techniques to gather data.
Acoustic Tracking Reveals Hidden Behaviors
Researchers circumvented the difficulties of direct observation by deploying specialized underwater listening systems off the coast of Louisiana, at a depth of approximately 1,100 meters. These sensors recorded the echolocation clicks emitted by the whales. By analysing the minute differences in the arrival times of these clicks at each sensor, scientists were able to reconstruct the whales’ movements in three dimensions.
Species-Specific Foraging Patterns
The study focused on three species of beaked whale: goose-beaked, Gervais’ and Blainville’s. Researchers were able to differentiate between the species based on the unique characteristics of their echolocation clicks, much like identifying bird species by their songs. This allowed them to map the specific behaviors of each species.
The data revealed variations in foraging dive durations. Goose-beaked whales spent approximately 20 minutes on each foraging dive, while Blainville’s beaked whales dove for nearly 14 minutes and Gervais’ beaked whales for just under 13 minutes. Goose-beaked whales also consistently dove almost to the seafloor during their foraging expeditions.
the research suggests that the different species target different prey at varying depths. Frouin-Mouy notes that this aligns with existing stomach content analyses, which indicate that goose-beaked whales consume larger cephalopods typically found at greater depths.
Human Impact and Future Research
The study underscores the vulnerability of these elusive creatures to human activities. Researchers believe the Deepwater Horizon oil spill in 2010 led to an estimated 83 percent decline in beaked whale populations. This finding highlights the urgent need for continued research and conservation efforts.
Understanding the diving behavior of beaked whales is crucial for estimating their population sizes and monitoring their response to stressors such as noise, chemical pollution, overfishing, and habitat loss. Further research could focus on expanding acoustic monitoring to other regions and investigating the long-term effects of environmental changes on these deep-diving mammals.
Frequently Asked Questions
What methods were used to study the beaked whales?
Researchers used passive acoustic monitoring, deploying underwater listening systems to record the whales’ echolocation clicks and reconstruct their movements.
Which species of beaked whales were studied?
The study focused on three species: goose-beaked, Gervais’ and Blainville’s beaked whales.
What was found regarding the foraging depths of the different species?
The data revealed that the different species appeared to be foraging at different depths, suggesting they feed on different prey items.
Given the demonstrated impact of events like the Deepwater Horizon oil spill, what further steps might be taken to protect these vulnerable marine mammals?