There's a rat in my room! now what? Mice show no chronic physiological response to the presence of rats.

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.

Assessment of the use of two commercially available environmental enrichments by laboratory mice by preference testing.

In the field of biomedical research, the demand for standardization of environmental enrichment for laboratory animals is growing. For laboratory mice, a wide variety of environmental enrichment items are commercially available. Most of these comply with the demands for standardization, hygiene and ergonomics. Whether these items also comply with their actual purpose, to enhance the well-being of the mice, is often not assessed scientifically. In this study, we tested the preference of mice for two commercially available nest boxes differing in shape and material: the Shepherd Shack/DesRes (SS/DR) and the Tecniplast Mouse House (TMH), in a simple preference test. To indicate strength of preference, both nest boxes were also tested against a highly preferred nesting material. Preference for the most preferred nest box was investigated further. Our results indicated a strong preference by mice for the SS/DR, but not for the TMH. Furthermore, nesting material was almost always combined with the SS/DR, but not with the TMH. More elaborate testing of the SS/DR in an automated preference test system confirmed that mice spent significantly more time in a cage in which an SS/DR is provided. Differences between both nest boxes are discussed with regard to their attractiveness to mice. It is also argued that enrichment should primarily be developed in concordance with the animals' needs prior to the marketing of enrichment tools.

Urinary corticosterone levels in mice in response to intraperitoneal injections with saline.

The concept of refinement is an important issue in the field of laboratory animal science. Refinement-based research aims to improve animal welfare, to increase the reliability of experimental outcome, and to diminish variation. In search of refinement of experimental techniques, this study investigated whether urinary corticosterone can be used as a noninvasive measure of acute stress in mice.

Anticipation is differently expressed in rats (Rattus norvegicus) and domestic cats (Felis silvestris catus) in the same Pavlovian conditioning paradigm.

In rats (Rattus norvegicus) anticipation to an oncoming food reward in an appetitive Pavlovian conditioning procedure is expressed as an increase of behavioural transitions, i.e. hyperactivity. This behaviour might be related to the spontaneous appetitive behaviour of animals in relation to oncoming food rewards. To deepen our insight into anticipatory behaviour we decided to study anticipation in rats and cats (Felis silvestris catus) using the same paradigm, as they show different types of spontaneous appetitive behaviour in relation to oncoming food rewards: 'search behaviour' and 'sit-and-wait behaviour' respectively. Using exactly the same Pavlovian conditioning paradigm in rats and cats it turned out that individuals of both species learned the association between conditioned stimulus (CS) (a tone) and unconditioned stimulus (US) (a food reward) as judged by their conditioned approach to the food dispenser. However, rats showed an increase in behavioural transitions whereas as cats a decrease during the 3 min interval between the offset of the CS and the onset of the US. Under extinction conditions the number of transitions of the rats decreased towards that of controls, whereas that of cats increased towards that of controls. This suggests that the same internal psychological process-anticipation to a coming reward-leads to different anticipatory behaviour in different species.