Black or white? The effect of tank background on the welfare of laboratory frogs (Xenopus laevis)

The environment in which laboratory animals are kept profoundly influences their welfare and can affect research outcomes. The African clawed frog (Xenopus laevis) is a common model organism for developmental and genetic research, but few studies have investigated its welfare needs and current husbandry guidelines aren’t supported by quantitative evidence. The visual environment is particularly important for species such as X. laevis, because they are adapted to live in murky waters and use cryptic camouflage as a fundamental defence mechanism, where their mottled green and brown skin provides disguise from predators. In contrast to conditions in the wild, Xenopus in laboratories are housed in clear water that is regularly cleaned to maintain frog health and allow visual inspection.

A new study recently published in Applied Animal Behaviour Science has demonstrated that laboratory housed X. laevis kept in tanks with dark (‘ecologically relevant’) backgrounds show fewer signs of stress compared with those kept in tanks with white backgrounds. The work was led by Dr Lottie Hosie from the University of Chester and funded by the NC3Rs. These findings show for the first time that tank background is an important aspect of frog housing and welfare. This work is particularly important as X. laevis are long lived in captivity and may be housed in the same environment for many years, extending the impacts that refinements to captive housing can have on individual welfare.



Holmes AM, Emmans CJ, Jones N, Coleman R, Smith TE, Hosie CA (2016).  Impact of tank background on the welfare of the African clawed frog, Xenopus laevis (Daudin). Applied Animal Behaviour Science doi: