Preserved shark jaws can reveal diet history

Teeth from sharks and rays can be used to study their diet, but one of the biggest challenges in shark science is collecting samples from rare or protected species.

Now, researchers have found that jaws in museums and private collections can serve as an untapped resource for shark teeth that provide valuable scientific information.

This can be done using biochemical techniques such as stable isotope analysis, which examines the isotopes within a shark's tooth.

A new Flinders University-led research paper, published in Marine Environmental Research, shows that chemicals used to preserve shark jaws do not affect the isotopes, enabling preserved jaws to be used for revealing what sharks eat and where they feed.

“The chemicals in teeth provide a story of what the shark has eaten and from where, whether that be sea lions in South Australia, or tuna in New South Wales,” explains lead author Laura Holmes, from the Southern Shark Ecology Group in the College of Science and Engineering at Flinders University.

Working with the Isotope Ratio Mass Spectrometry Laboratory in the University of Tasmania, the researchers examined three species with different tooth structures: cownose rays, gummy sharks, and broadnose sevengill sharks. Despite the different tooth structures, none were altered by ethanol, bleach, or hydrogen peroxide, the chemicals often used to clean shark jaws and whiten the teeth.

“Most shark jaws in museums and private collections are chemically treated, so understanding if, or how these treatments affect tooth isotopes is crucial,” says Flinders University research associate Dr Lauren Meyer.

“Finding that preservation chemicals had no impact on isotope values opens the door for the use of jaws from historic collections across Australia and globally.”

This study contributes valuable insights to the field of stable isotope analysis in shark and ray teeth, offering practical recommendations and expanding the range of available samples for investigation.

“This is especially useful for rare or threatened species, for which standard tissue samples may not be readily available, but for which trophy jaws have been collected, such as white sharks, tiger sharks, and makos” says Dr Meyer.

“Now we can begin to use museum collections and jaws from the 1970s and 1980s to explore the historic diet of shark species that now face a myriad of anthropogenic pressures.”

Insights from this study also opens pathways for diet investigations of other animals such as killer whales, sperm whales and fur seals, for which teeth from historic jaws are available in museum collections.

“This study opens the door to use a tremendous resource of samples to untangle the current and historic diet and foraging habitats of complex predators – making the most exciting finding from this study the capacity for new research that is now possible,” says Dr Meyer.

The research – “δ 13C, δ 15N, and δ 34S isotope values from preserved elasmobranch jaws: Implications for ecological studies from existing collections”, by Laura Holmes, Charlie Huveneers, Vincent Raoult, Thomas Clarke, Christain Dietz and Lauren Meyer – has been published in Marine Environmental Research. doi.org/10.1016/j.marenvres.2025.107063

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