Mice are the most commonly used animals in vivisection around the world, yet there’s generally less recognition and regulation of their welfare when compared to other species. When their welfare is assessed, one measurement that’s often used is the Time to Integrate to Nest Test (TINT). Based on the premise that mice are highly motivated to build their own nesting place, this test measures how long it takes for them to engage in nesting after a new piece of nesting material has been introduced to their cage. Less than 10 minutes on a TINT is considered to be good, while more than 10 minutes is viewed as abnormal or an indication of poor welfare.

In this study, scientists found that nesting material isn’t consistently provided to lab mice, and that there’s a wide range in the amount and type of material provided. Further to this, the authors state that the results of TINTs varied greatly depending on whether the mice were housed individually or in groups, with solo mice sometimes lagging behind by several minutes. Perhaps most interesting for lab animal advocates is the conclusion of this paper. It outlines ways that corners can be cut in the welfare assessment process: the nature of the TINT means that mice don’t require constant observation for the whole 10 minutes of the test, and the observer doesn’t even need to have a good understanding of mouse behavior. They simply need to check to see if the TINT material has been integrated into a nest. Though the authors of this study try to spin these points to show how following these tips allows lab mouse welfare to be assessed and addressed quickly, it’s clear to advocates that the welfare of these animals, already a low priority, is getting even less attention than scientists may have us believe.