There's a Rat in My Room! Now What? Mice Show No Chronic Physiological Response to the Presence of Rats

Abstract

In general, guidelines on housing and care of animals in the laboratory state that rats and mice should not be housed in the same room. Mice may perceive rats as predators. Although one theory says this can cause stress, there is little scientific evidence to support this theory. In the wild, rats and mice usually do not share the same microhabitat, but this appears to be true for most small rodent species. Furthermore, reports of predatory behavior of rats toward mice mainly originate from experimental settings using rats with high inbred levels of aggression. This experiment measured heart rate (HR), body temperature (BT), activity (AC), and urinary corticosterone in female C57BL/6 mice before, during, and after introducing Wistar rats into their room. The study found no chronic effects of rat introduction on any parameters. The study concluded that housing rats and mice in the same room is at least less disturbing than cage cleaning, which caused a temporary increase of HR, BT, and AC. Current results do not support legislation based on compromised welfare.

Temporal behaviour profiles of Mus musculus in nature are affected by population activity

“…Previous research indicates that in the laboratory, mice ignore the activity of rats [44], and in the field, rats do not influence the behaviour of wild mice [55]. Nevertheless, in our study, we believe that the presence of the rats may have repelled the mice.…”

Effects of Housing Density in Five Inbred Strains of Mice

“…Adrenal weight is often used as a measure of stress, reflecting degree of chronic stress hormone production [28]–[30], and the trend in decreased adrenal weight we observed suggests that mice housed more densely were less stressed; however we recognize that changes did not reach statistical significance. Heart rate, another commonly used measure of stress [31]–[33], decreased as density increased. This observation may indicate that these mice were less stressed.…”

Physiological effects of housing density on C57BL/6J mice over a 9-month period1

“…Heart rate is often used as a measure of stress (Bernberg et al, 2009; Gilmore et al, 2008; Meijer et al, 2009) and was therefore chosen for evaluation in our study. Our results confirm previous studies that demonstrated reduced heart rate with increased housing density (Nicholson et al, 2009; Van Loo et al, 2007).…”