Acoustic study links Omura’s whales to warm, productive waters

Omura’s whales were more likely to occur in warm, food-rich waters off northwest Australia, according to an observational study that analyzed nearly two decades of underwater acoustic recordings. The results provide a baseline for understanding the habitat of a species that is rarely seen in the wild and is classified as Data Deficient on the International Union for Conservation of Nature Red List, meaning there is currently insufficient information to assess its extinction risk accurately. Researchers from Curtin University’s Centre for Marine Science and Technology analyzed recordings collected at 35 sites across roughly 1,800 kilometres of ocean between 2005 and 2023.

The long-term dataset captured Omura’s whale calls throughout the year, but detections were more frequent from September through May, when waters were warmer. Because visual sightings of Omura’s whales are rare, their vocalizations provide an important way to identify where the animals occur and how their distribution changes with seasonal ocean conditions. The researchers associated the presence of whale calls with sea-surface temperatures above 27.5°C, stronger winds and higher concentrations of chlorophyll-a, an indicator of microscopic marine life that forms the base of the ocean food web.

Their analysis also found that acoustic presence increased about one month after periods of elevated chlorophyll-a. This delayed pattern suggests that the whales may respond to increases in ocean productivity and prey availability that follow changes in ocean conditions, although the study does not establish that these environmental factors directly cause whale movements. The findings identify conditions associated with the species’ presence rather than measuring abundance: they show where and when calls were recorded, not how many individual whales produced them.

Lead author Ciara Browne said listening for the animals’ calls provides an important way of understanding where they occur because visual sightings are notoriously difficult. The results showed that the whales were acoustically present year-round, but that their distribution shifted with the seasons, with a greater likelihood of presence during warmer months. Co-author Christine Erbe said the findings provide an important baseline for understanding how Omura’s whales use Australian waters and how they may respond to environmental change.

That baseline may help inform marine planning, including assessments of potential impacts from shipping, offshore industry and other sources of underwater noise. It may also improve understanding of how future climate change could affect the whales’ behavior, but the acoustic study does not quantify future climate effects or establish specific threats facing the species. Long-term datasets such as this one can reveal patterns that would otherwise remain hidden and provide decision-makers with evidence about where marine species occur and the environmental conditions associated with their presence.

For an elusive species such as Omura’s whale, identifying the habitats and ocean conditions it favors is an important first step toward protecting it and informing future conservation efforts.

Subject of Research: Seasonal acoustic habitat associations of Omura’s whales off northwest Australia

Article Title: Listen up: 18 years of whale calls reveal key habitat of mysterious species

Article References: Listen up: 18 years of whale calls reveal key habitat of mysterious species. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: Omura’s whale, underwater acoustics, marine habitat, northwest Australia, ocean temperature, chlorophyll-a, seasonal distribution, marine conservation, Listen, years, whale, calls