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Why do male ICR(CD-1) mice perform bar-related (stereotypic) behaviour?
C M Nevison1, J L Hurst2, C J Barnard3
1Animal Behaviour Research Group, Division of Animal Husbandry, Department of Clinical Veterinary Medicine, University of Liverpool, Leahurst Veterinary Teaching Hospital, Neston, South Wirral, CH64 7TE, UK; School of Biology, University of Nottingham, Nottingham, NG7 2RO UK.
Mice in laboratory cages showed stereotypic bar-interaction behaviors driven by environmental cues and escape motivation. Their stress physiology, indicated by corticosterone levels, was influenced by bar location and physical development.
Area of Science:
- Animal behavior
- Laboratory animal welfare
- Ethology
Background:
- Stereotypic behaviors in captive mammals, such as prolonged interaction with cage bars, are often indicators of poor welfare.
- These behaviors may stem from a motivation to explore the environment or to escape confinement, but these hypotheses lack direct testing.
Purpose of the Study:
- To investigate the motivational drivers behind bar-related behaviors in laboratory mice (Mus musculus).
- To test whether environmental exploration or escape motivation influences bar interaction.
- To examine the relationship between physical development, stress physiology, and bar-related behaviors.
Main Methods:
- Mice were housed in modified cages with bar sets offering potential escape routes and varied external cues (Perspex backing).
- Bar interaction, body weight, and serum corticosterone levels were monitored throughout development.
- Behavioral responses were analyzed in relation to environmental cues, escape route accessibility, and physical development.
Main Results:
- Mice showed a preference for interacting with bars offering detectable external cues.
- Adult mice exhibited increased interaction with bars providing a potential exit, with response modulated by exit location.
- Higher corticosterone levels were observed in mice with a top cage exit, and bar interaction was limited by physical development, especially for top exits.
Conclusions:
- Bar-related behaviors in mice are influenced by both environmental exploration and escape motivations.
- The location of an escape route and physical development significantly impact these behaviors and associated stress physiology.
- These findings provide insights into the welfare implications of cage design and environmental enrichment for laboratory mammals.
