Determinants of feeding performance in free‐ranging pit‐vipers (Viperidae: Ovophis okinavensis ): key roles for head size and body temperature

Feeding performance (handling time, capture success) in numerous animal species is well known to be influenced by a variety of ecological, functional, and physiological factors. Nonetheless, few studies have tested which factors are the strongest determinants of animal feeding performance in the wild. Using a field‐based experiment, we examined the relationships among a number of functionally important variables and the predatory behaviour of free‐ranging pit‐vipers ( Ovophis okinavensis ) from Okinawa Island, Japan. Our main findings were: (1) strike latency was negatively related to snake body temperature and, hence, hotter snakes struck at frogs more readily than colder snakes; (2) initial bite position was correlated with ingestion direction (headfirst versus hindfirst) but ingestion direction was not correlated with ingestion duration; and (3) both snake head length and body temperature were negatively related with ingestion duration and, thus, snakes with longer heads and higher body temperatures had shorter ingestion durations. In O. okinavensis , head size and body temperature are therefore likely to have direct ecological consequences in terms of its feeding rate on explosively breeding frogs. More generally, however, this field‐based study adds to the growing body of literature demonstrating that temperature has a pervasive influence on the feeding performance of ectotherms in general. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 53–62.