Biometrics, Testosterone, Cortisol and Antler Growth Cycle in Iberian Red Deer Stags (Cervus elaphus hispanicus) E Gaspar-Lo´pez 1,2 , T Landete-Castillejos 1,2,3 , JA Estevez 1,2,3 , F Ceacero 1,2,3 , L Gallego 1,2,3 and AJ Garcı´a 1,2,3 1 Seccio ´n de Recursos Cinege ´ticos, IDR; 2 Departamento de Ciencia y Tecnologı´a Agroforestal y Gene ´tica, ETSIA, Universidad de Castilla-La Mancha; 3 Instituto de Investigacio ´n en Recursos Cinege ´ticos, IREC (CSIC, UCLM, JCCM), Campus Universitario s ⁄ n, Albacete, Spain Contents In this article, we aimed to describe the changes related to mating season in red deer, especially those related to antler growth, body condition score, testosterone and cortisol. Antler growth was studied in 17 Iberian red deer males, including body weight, antler length, biometric measures and testoster- one and cortisol determination during 15 months. Body weight, body condition score, thoracic perimeter (TP), neck perimeter (NL) and testicular diameter (TD) showed the highest values immediately before mating season (autumn), decreased during it and remained constant at winter. Antler growth lasted 158 days and produced antlers with a final length of 80.8 ± 2.0 cm. Testosterone and cortisol showed seasonal changes with maximum values at September and May, respectively. Final antler size was related positively to cranial longitude, TP, NL, TD and body weight at casting time. No relationship between weight loss during precedent mating season and current antler size was found, but spring recovery weight was positively related to final antler size. Final length was related to the descent in testosterone values during previous mating season and to body weight before it. Spring recovery weight was related to relative weight loss during previous mating season. These results suggest that there is no relationship between the reproductive effort performed during one season and the next year size of the antler. In contrast, antler size was positively related to spring recovery weight, in the sense that those deer that recover a higher percentage of body weight at the early stages of antler growth develop higher antlers. Introduction Deer is considered by some authors as the last tamed species (Anderson 1992; Hamilton 1994; Diverio et al. 1996), which farm management is increasing, as it is considered an environmental safe stockbreeding (Milne 1994). The event that characterize mating season in red deer is the occurrence of fights among stags to gain access to a high number of hinds (Clutton-Brock 1982). In these fights, males use antlers as weapons, which are bony structures that grow by modified endochondral ossification (Banks and Newbrey 1982), at a growth rate of 1 cm ⁄ day (Goss 1983). Antlers are the only mammal structure that regenerates physiologically every year (Suttie et al. 1991). This process is under the control of androgen hormones (Lincoln 1971; Bubenik 1982; Go´mez et al. 2006a) that synchronize antler cycle to male reproductive status through changes in their secretion (Rolf and Fischer 1996). Testosterone is at low values during antler growth at spring, and at early summer, it rises inducing the end of antler growth and velvet shedding (Goss 1968). This high testosterone levels affect the hypothalamic-pituitary-adrenal axis, inhibiting cortisol secretion by the adrenal cortex (Ingram et al. 1999). Antler growth is one among a group of male characteristics that are affected by the approaching of mating season (Rolf and Fischer 1996), as a conse- quence of the increase in androgens (Suttie et al. 1992). It is accompanied by a weight gain that increases the ability of fighting against other males (Clutton-Brock 1982). These fights condition not only short-term reproductive success, granting access to a higher number of hinds (Clutton-Brock 1982), but also long-term success, through injuries (Clutton-Brock et al. 1979) or even death (Wilkinson and Shank 1976), forcing them to reach their best condition for mating season that, at the Iberian Peninsula, takes place during autumn, i.e. during September and October (Garcı´a et al. 2002). At this time, deer suffers an intense decrease in food intake (Rhind et al. 1998) that causes a weight loss. This weight loss has been used as a measure of male mating effort and to assess its consequences in terms of male survival (Yoccoz et al. 2002; McElligott et al. 2003; Forsyth et al. 2005). However, death is not the only adverse consequence of an excessive effort so that some males could not totally recover for next mating season, and this may lead them to develop smaller antlers that reduce their next year reproductive success. This, to our knowledge, has not been studied so far. The aim of this study was to describe testosterone, cortisol and morphometrics seasonal changes and to assess their relationship to antler cycle. It was performed on adult Iberian red deer stags, a subspecies has only been studied in younger animals (Go´mez et al. 2006b; Gaspar-Lo´pez et al. 2008a,b). Special attention was paid on body condition score on a seasonal-based scale, because this parameter, to our knowledge, has not been studied to date in male red deer. Additional aims were to analyse the relationship between some biometric mea- sures taken at casting time and final antler measure- ments and to assess the effect of the precedent mating season effort and extent of recovery at spring over the current antler measurement. Material and Methods Antler growth was studied in 17 Iberian red deer stags (Cervus elaphus hispanicus) aged 6 years. Deer were kept at the Experimental Farm of Castilla-La Mancha University in Albacete, Spain (38°57¢10¢N, 1°47¢00¢W, 690 m altitude). Animals were kept in a 10 000 m 2 fenced enclosure and were fed following suggestions by Reprod Dom Anim 45, 243–249 (2010); doi: 10.1111/j.1439-0531.2008.01271.x ISSN 0936-6768 Ó 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag