Functional and numerical responses of predators: Where do vipers fit in the traditional paradigms?

Erika M. Nowak, Tad C. Theimer, Gordon W. Schuett

Research output: Contribution to journalReview articlepeer-review

52 Scopus citations


Snakes typically are not considered top carnivores, yet in many ecosystems they are a major predatory influence. A literature search confirmed that terrestrial ectotherms such as snakes are largely absent in most discussions of predator-prey dynamics. Here, we review classical functional and numerical responses of predator-prey relationships and then assess whether these traditional views are consistent with what we know of one group of snakes (true vipers and pitvipers: Viperidae). Specifically, we compare behavioural and physiological characteristics of vipers with those of more commonly studied mammalian (endothermic) predators and discuss how functional and numerical responses of vipers are fundamentally different. Overall, when compared to similar-sized endotherms, our analysis showed that vipers have: (i) lower functional responses owing primarily to longer prey handling times resulting from digestive limitations of consuming large prey and, for some adults, tolerance of fasting; (ii) stronger numerical responses resulting from higher efficiency of converting food into fitness currency (progeny), although this response often takes longer to be expressed; and (iii) reduced capacity for rapid numerical responses to short-term changes in prey abundance. Given these factors, the potential for viperids to regulate prey populations would most likely occur when prey populations are low. We provide suggestions for future research on key issues in predator-prey relationships of vipers, including their position within the classical paradigms of functional and numerical responses.

Original languageEnglish (US)
Pages (from-to)601-620
Number of pages20
JournalBiological Reviews
Issue number4
StatePublished - Nov 2008


  • Crotalus atrox
  • Ectotherms
  • Endotherms
  • Functional response
  • Numerical response
  • Predator-prey dynamics
  • Prey regulation
  • Reptiles
  • Viperidae

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences


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