Puncture versus capture: which stresses animals the most?

Abstract

The prerogative of animal welfare science includes wild species and ecological studies. Yet, guidance enshrined in legislation is narrowly derived from studies involving laboratory rodents; legitimacy for non-mammalian free-ranging species is thus debatable. The European directive 2010/63/EU illustrates this problem. It includes this key statement: “Practices not likely to cause pain, suffering, distress or lasting harm equivalent to, or higher than, that caused by the introduction of a needle…” which determines if the directive shall apply. Protocols involving surgery clearly fall within the scope of the directive: procedures are scrutinized, investigators and technicians must be qualified and various agreements are required (e.g. issued by an ethical committee). By contrast, non-invasive procedures, like mark-recapture population studies, merely need a permit from wildlife authorities (at least in most countries). Yet, blood sampling that implies the introduction of a needle—one of the most common practices in animals—could shift any study on the constraining-side of the directive, on the grounds that puncture impacts individuals more severely than capture. We examined the validity of the needle-threshold using the stress response of free-ranging snakes. Our results based on physiological markers show that blood sampling does not add any stress to that triggered by capture, and thus questions the usefulness of the needle-threshold to gauge welfare in wild animals. The specificities of studying wild species should be considered to redress captivity biased animal welfare policy.