rspb.royalsocietypublishing.org Research Cite this article: Ruiz-Aravena M, Jones ME, Carver S, Estay S, Espejo C, Storfer A, Hamede RK. 2018 Sex bias in ability to cope with cancer: Tasmanian devils and facial tumour disease. Proc. R. Soc. B 285: 20182239. http://dx.doi.org/10.1098/rspb.2018.2239 Received: 4 October 2018 Accepted: 1 November 2018 Subject Category: Ecology Subject Areas: ecology, evolution, physiology Keywords: host–pathogen, cope with infection, tolerance to infection, DFTD Author for correspondence: Manuel Ruiz-Aravena e-mail: m.ruiz.aravena@gmail.com Electronic supplementary material is available online at https://dx.doi.org/10.6084/m9. figshare.c.4294445. Sex bias in ability to cope with cancer: Tasmanian devils and facial tumour disease Manuel Ruiz-Aravena 1 , Menna E. Jones 1 , Scott Carver 1 , Sergio Estay 3,4 , Camila Espejo 2 , Andrew Storfer 5 and Rodrigo K. Hamede 1 1 School of Natural Sciences, and 2 School of Medicine, University of Tasmania, Hobart, Australia 3 Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia, Chile 4 Center of Applied Ecology and Sustainability, Facultad de Ciencias Biolo ´gicas, Pontificia Universidad Cato ´lica de Chile, Santiago, Chile 5 School of Biological Sciences, Washington State University, Pullman, WA, USA MR-A, 0000-0001-8463-7858 Knowledge of the ecological dynamics between hosts and pathogens during the initial stages of disease emergence is crucial to understanding the poten- tial for evolution of new interspecific interactions. Tasmanian devil (Sarcophilus harrisii) populations have declined precipitously owing to infec- tion by a transmissible cancer (devil facial tumour disease, DFTD) that emerged approximately 20 years ago. Since the emergence of DFTD, and as the disease spreads across Tasmania, the number of devils has dropped up to 90% across 80% of the species’s distributional range. As a result, the disease is expected to act as a strong selective force on hosts to develop mechanisms of tolerance and/or resistance to the infection. We assessed the ability of infected devils to cope with infection, which translates into host tolerance to the cancer, by using the reaction norm of the individual body condition by tumour burden. We found that body condition of infected hosts is negatively affected by cancer progression. Males and females pre- sented significant differences in their tolerance levels to infection, with males suffering declines of up to 25% of their body condition, in contrast to less than 5% in females. Sex-related differences in tolerance to cancer pro- gression may select for changes in life-history strategies of the host and could also alter the selective environment for the tumours. 1. Background Host and pathogen populations are entangled in ongoing conflicts of interest which result in complex eco-evolutionary dynamics. Pathogens exploit host resources to replicate and transmit, a process that imposes fitness costs on the host [1,2]. Hosts express two distinct defence strategies to cope with infection and decrease the effects of pathogen burden: resistance and tolerance [3,4]. Resistance is a mechanism by which hosts directly attack the pathogen, redu- cing pathogen burden and therefore negatively affecting pathogen fitness. Tolerance, on the other hand, is a mechanism by which the host can buffer the negative impact of infection on its health without reducing the pathogen fit- ness [4–6]. There are epidemiological and ecological costs and benefits for a host investing in either of these energetically expensive defence mechanisms [7,8], and hosts are expected to display the strategy, or combination of both, that pro- vides the best cost–benefit balance [7,9–11]. Tolerance, which translates to host ability to cope with infections, is proposed to be more beneficial to hosts than resistance when the risk of becoming infected is high as a result of high disease prevalence [11,12]. This strategy may increase the infectious period in hosts, and therefore may also benefit the pathogen in the long term by increasing pathogen prevalence, and with it the benefits of hosts carrying genes able to buffer the impacts of infection in the population [11]. On the other side, resistance & 2018 The Author(s) Published by the Royal Society. All rights reserved.