From 300 to 15,000: Whale Poop Study Offers Climate Survival Clues

As Antarctic waters warm and sea ice retreats, the southern right whale’s primary food source—krill—is dwindling, threatening a species that has only recently recovered from near-extinction. A new analysis of whale feces reveals that these massive mammals have a surprisingly adaptable diet, offering a glimmer of hope for their resilience in a changing ocean.

In a study that turns an unlikely substance into a scientific treasure, researchers have analyzed southern right whale feces to uncover surprising dietary breadth that may prove critical for the species' survival as climate change reshapes its Antarctic feeding grounds. The research, led by Macquarie University and the University of Auckland, leverages samples collected by citizen scientists like Rod Keogh, who for years stored grapefruit-sized, clay-like whale poo found on South Australia's Eyre Peninsula in his freezer. Together with samples from South Africa and New Zealand, the analysis reveals that these 16-meter, 100-tonne marine mammals consume a far wider variety of small marine animals than previously assumed—crabs, shrimp, and lobsters—while krill, long considered their staple, appears to play a more subtle microbial role.

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Relentlessly hunted during the 19th and 20th centuries, the global population crashed from an estimated 100,000 to as few as 300 individuals before international protections enabled a slow recovery to roughly 15,000 today.

The southern right whale is often framed as a conservation success. Relentlessly hunted during the 19th and 20th centuries, the global population crashed from an estimated 100,000 to as few as 300 individuals before international protections enabled a slow recovery to roughly 15,000 today. But that recovery faces a new, more diffuse threat. Antarctic waters are among the fastest-warming on Earth, and the retreat of sea ice is diminishing the abundance of Antarctic krill, a cornerstone of the Southern Ocean food web. Some whale populations have already shown reduced birth rates linked to these changes. In this context, the discovery that southern right whales are not picky eaters—and that their gut microbiomes retain a signature of krill even when it is not the dominant prey—offers a critical window into how large marine predators might weather ecological disruption.

The study’s methodology is straightforward but powerful. DNA metabarcoding of fecal samples allowed scientists to identify prey species, while microbial analysis mapped the gut bacteria associated with different diets. The most commonly detected food items across all locations were small, likely juvenile, crustaceans such as crabs, shrimp, and lobsters. Krill, by contrast, was rarely found directly in the fecal samples, yet it remained a key driver of gut microbiome composition. Macquarie University PhD student Aashi Parikh noted that this lingering microbial signature suggests krill remains an important, perhaps seasonal, dietary component that shapes the whales’ overall health. This dual finding—dietary flexibility and microbial resilience—may help explain how some populations are coping better than others with changing food availability.

From a climate adaptation standpoint, the research has immediate policy and conservation relevance. If southern right whales can switch prey without sacrificing gut health, marine protected areas and fisheries management strategies can be designed to safeguard a broader range of prey species, not just krill. This might mean protecting coastal nurseries for lobsters and shrimp off Australia and South Africa, or adjusting krill fishery quotas in the Southern Ocean to ensure that even occasional krill feeding remains possible. The study also underscores the value of longitudinal fecal sampling—a low-cost, non-invasive tool—to monitor diet shifts over time and detect early warning signs of nutritional stress in recovering whale populations.