Hedgehog jawbones (IMAGE) University of Oxford Caption Hedgehog jawbones which are used for age determination research. A hedgehog’s age can be worked out by counting year rings in sections of their jawbones. Credit: Sophie Lund Rasmussen Credit Hedgehog jawbones which are used for age determination research. A hedgehog’s age can be worked out by counting year rings in sections of their jawbones. Credit: Sophie Lund Rasmussen Usage Restrictions The image can only be used if credited. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.