Project leader: Henrik Birkedal, Aarhus University
Project duration: 2021-2026
Participating countries: Denmark, Greenland and Sweden
Funding from NordForsk: 14,359,011 NOK
Project website: Narwhal tusks: a tale with a twist
What can we learn of the changing Arctic environment through narwhal tusks? The researchers have studied the mysterious helical structure of narwhal tusks and each individual layer of growth in the tusks of narwhals in Greenland, to find answers to what the tusks can tell us about living and climate conditions in the Arctic.
Impact story
The narwhal’s spiral tusk has annual rings, and they can reveal past changes in the climate. Researchers from the project have discovered how the tusk is built and what is the origin of the spiral tusk structure and that there also appear to be rings within the annual rings, which can provide even more details about living conditions in the Arctic.
“We have realised that the tusk structure is more complicated than we had imagined. We have uncovered how the arrangement of the molecular-scale building blocks of the tusk result in its evocative spiral morphology. Additionally, we have developed a model of the annual growth bands that we hope will enable revealing variations in living conditions in the Arctic over the life of narwhals,” says project leader Henrik Birkedal.
Key Findings
- Narwhal tusk has a puzzling spiral morphology – always forming a helix with the same handedness. The researchers have been able to determine how the molecular building blocks arrange in a hierarchical structure that results in the overall cm-scale helix of the tusk. This involved a tour-de-force set of advanced experiments using synchrotron X-ray facilities across Europe, including the MAX-IV synchrotron in Lund, Sweden.
- The tusk contains annual growth bands that mark how fast the tusk has grown per year – like rings in a tree. The researchers have studied these using many different methods and found that the elemental composition of tusk and tooth is related to where whales live around Greenland, that the position of the growth bands can be mapped to determine the narwhals age and that the growth bands impact some but intriguingly not all of the narwhal tusk structural features.
- Furthermore, they have refined methods for analyzing tooth material for hormones, including the stress hormone cortisol, providing insights into how individual narwhals respond over time to environmental change and ocean warming. The results provide deep insights into the structural design of this enigmatic tusk and provide the basis for relating tusk annual growth band structure to whale growth conditions and thereby to the living and climate conditions in the Arctic.
Key outputs
Interdisciplinary training of young talents in the project resulted in prestigious Marie Curie individual postdoc fellowships to two employees in the project.
New knowledge on the relationships between or variations of chemical composition, hormones, structural features of narwhal tusks and teeth – as well as statistical models of these – that will form the basis for mapping living conditions in the changing Arctic.
Improved methods for analysis of complex structural and compositional data from tissues like bone and teeth have been established – these will be openly available for other researchers.
Publications from the project: https://inano.au.dk/about/research-centers-and-projects/narwhal.