Epaulette sharks, known for their unique ability to “walk” on fins, are now rewriting the rules of reproduction. Scientists at James Cook University recently discovered these fascinating creatures can lay eggs and create new life without any measurable increase in their energy expenditure, a finding that upends long-standing biological tenets about the high cost of reproduction.
This groundbreaking insight, detailed in a study by JCU’s shark physiology team, led by Professor Jodie Rummer, was published in Biology Open. The research, highlighted on ScienceDaily on January 21, 2026, revealed that the metabolic rate of these sharks remained remarkably stable throughout their reproductive cycle, a phenomenon previously thought impossible for complex egg-laying species.
For most animal species, the act of reproduction is considered one of the most energetically demanding processes. Building new life from scratch, as Professor Rummer noted, typically requires a significant uptick in metabolic activity. The epaulette shark’s ability to maintain a flat energy profile during this crucial phase suggests an exceptional evolutionary adaptation.
The unusual efficiency of epaulette shark reproduction
Researchers meticulously tracked five female epaulette sharks before, during, and after egg case formation. Housed in temperature-controlled tanks at JCU’s Marine and Aquaculture Research Facility Unit, the sharks allowed for precise measurements of oxygen uptake rates, a direct proxy for metabolic rate. Lead author Dr. Carolyn Wheeler, a JCU PhD graduate, confirmed that blood chemistry and hormone levels also remained stable.
This stability challenges fundamental assumptions about chondrichthyan fishes, a group that includes sharks, rays, skates, and chimaeras. Unlike many species that must choose between survival and reproduction under environmental stress, epaulette sharks appear capable of continuing egg production even when facing external pressures. This resilience is a critical discovery.
Professor Rummer emphasized the implications of this efficiency: “These sharks appear to have adapted their physiology to be able to optimize their energy use.” This optimization could be a key factor in their survival, particularly in the context of warming ocean temperatures. The study suggests that reproduction might not be the first biological process to falter when conditions become challenging for these specific sharks.
Implications for a changing marine world
The findings from the epaulette shark study offer a glimmer of hope and a new perspective on marine resilience. While many scientists anticipate that climate change will severely impact species’ reproductive capacities due to increased energy demands, the epaulette shark presents an alternative scenario. Its unique metabolic strategy could make it more robust against environmental shifts than previously imagined.
Understanding how these sharks achieve such reproductive efficiency could inform broader conservation strategies. If some species can evolve mechanisms to buffer the metabolic costs of reproduction, it opens avenues for exploring similar adaptations in other vulnerable marine life. However, Prof Rummer cautions that determining the exact limits of their resilience to warming oceans remains crucial.
The continued health of shark populations, including the highly adaptable epaulette shark, is vital for the overall well-being of coral reefs. As the marine environment faces unprecedented changes, these insights into the remarkable reproductive biology of walking sharks provide valuable data for future ecological models and conservation efforts.
