1 3 Oecologia DOI 10.1007/s00442-014-3190-5 PHYSIOLOGICAL ECOLOGY - ORIGINAL RESEARCH The interactions between temperature and activity levels in driving metabolic rate: theory, with empirical validation from contrasting ectotherms L. G. Halsey · P. G. D. Matthews · E. L. Rezende · L. Chauvaud · A. A. Robson Received: 28 July 2014 / Accepted: 10 December 2014 © Springer-Verlag Berlin Heidelberg 2015 on total MR estimated from RMR–temperature measure- ments can be misleading when the contribution of activ- ity to total MR is neglected. A simple conceptual frame- work illustrates that since the relationship between activity levels and temperature can be different to the relationship between RMR and temperature, a consistent relationship between RMR and total MR cannot be assumed. Thus the thermal effect on total MR can be considerably different to the thermal effect on RMR. Simultaneously measured MR and activity from three ectotherm species with dif- fering behavioural and physiological ecologies were used to empirically examine how changes in temperature drive changes in RMR, activity level, AMR and the Q 10 of MR. These species exhibited varied activity– and MR–tem- perature relationships, underlining the difficulty in pre- dicting thermal influences on activity levels and total MR. These data support a model showing that thermal effects on total MR will deviate from predictions based solely on RMR; this deviation will depend upon the difference in Q 10 between AMR and RMR, and the relative contribution of AMR to total MR. To develop mechanistic, predictive models for species’ metabolic responses to temperature changes, empirical information about the relationships between activity levels, MR and temperature, such as reported here, is required. This will supersede predictions based on RMR alone. Keywords Oxygen consumption · Energy expenditure · Activity · Accelerometry · Cockroach Introduction The total metabolic rate (MR) of an organism is the sum of its resting and active energy costs, the former represented Abstract The rate of change in resting metabolic rate (RMR) as a result of a temperature increase of 10 °C is termed the temperature coefficient (Q 10 ), which is often used to predict how an organism’s total MR will change with temperature. However, this method neglects a poten- tially key component of MR; changes in activity level (and thus activity MR; AMR) with temperature may signifi- cantly alter the relationship between MR and temperature. The present study seeks to describe how thermal effects Communicated by Sylvain Pincebourde. L. G. Halsey (*) · E. L. Rezende Department of Life Sciences, Centre for Research in Ecology, University of Roehampton, Holybourne Avenue, London SW15 4JD, UK e-mail: l.halsey@roehampton.ac.uk P. G. D. Matthews School of Biological Sciences, University of Queensland, Goddard Building 8, St Lucia, QLD 4072, Australia Present Address: P. G. D. Matthews Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada L. Chauvaud Laboratoire des Sciences de L’Environnement Marin (UMR CNRS 6539), Institut Universitaire Européen de la Mer, Technopôle Brest Iroise, 29280 Plouzané, France A. A. Robson LabexMER, UMS 3113 CNRS, Institut Universitaire Européen de la Mer, Université de Brest, Rue Dumont D’Urville, 29280 Plouzané, France A. A. Robson Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK