Assessment of restraining devices, according to the Agreement on International Humane Trapping Standards, for capture of wild animals, at present is reliant on injury data. This standard was developed and agreed over 10 years ago, and there was hope at that time that further developments in the area of using behaviour and physiology for welfare assessment, would allow these to be incorporated into the Standards. In this paper we review the scientific studies carried out to date in wild animals to determine if sufficient advances have been made to allow such use. Although it may seem straight-forward to transfer knowledge gained from domestic species into wild species, it is very difficult. Firstly, in contrast to many domestic animals, the normal behavioural repertoire and physiological profile, of many of the species under investigation is unknown. Secondly, the presence of the human observer and experimental set up has a profound impact on the species under investigation, impacting on the behaviour and physiology to a much greater degree than with domestic animals. Thirdly, the logistics of obtaining statistically robust data from the field to enable an assessment to be carried out. An insurmountable problem with the Agreement on International Humane Trapping Standards is that it encompasses a diverse range of species, from large predatory mammals e.g. wolf, to small herbivorous mammals e.g. muskrat. For the purposes of an International Standard, injury data, that can be compared across species may be the only option to judge humaneness, however this does not mean that behaviour and physiology should not be used for comparison of control methods within a particular species.