Dear MARMAM colleagues, We are pleased to announce a new publication that describes and compares in detail two on-animal sensing methods sensors that can track biomechanical swimming parameters including changes in gait during cetacean diving, enabling studies of swimming energetics in wild animals. Martı́n López, L. M., Aguilar de Soto, N., Miller, P. and Johnson, M. (2016). Tracking the kinematics of caudal-oscillatory swimming: a comparison of two on-animal sensing methods. J. Exp. Biol. 219, 12103-2109. *Abstract* Studies of locomotion kinematics require high-resolution information about body movements and the specific acceleration (SA) that these generate. On-animal accelerometers measure both orientation and SA but an additional orientation sensor is needed to accurately separate these. Although gyroscopes can perform this function, their power consumption, drift and complex data processing make them unattractive for biologging. Lower power magnetometers can also be used with some limitations. Here, we present an integrated and simplified method for estimating body rotations and SA applicable to both gyroscopes and magnetometers, enabling a direct comparison of these two sensors.We use a tag with both sensors to demonstrate how caudal-oscillation rate and SA are adjusted by a diving whale in response to rapidly changing buoyancy forces as the lungs compress while descending. The two sensors gave similar estimates of the dynamic forces, demonstrating that magnetometers may offer a simpler low-power alternative for miniature tags in some applications. The article can be found at: http://dx.doi.org/10.1242/jeb.136242 If you do not have access to the journal, please contact me for a PDF at: lmml2@st-andrews.ac.uk Kind regards, Lucía Martina Martín López and co-authors. -- Lucía Martina Martín López, PhD student Sea Mammal Research Unit Scottish Oceans Institute University of St Andrews KY16 8LB, Fife Scotland, UK lmml2@st-andrews.ac.uk http://soundtags.st-andrews.ac.uk/people/lucia-martin-lopez/