Stress Assessment, Reduction, and Science | 543 stomach or paws This caused these mice to writhe in pain When a writhing mouse could be observed by another mouse, the witnessing mouse became more sensitive to pain, but only if the writhing mouse was a familiar individual This result suggests that mice can show empathy for another whom they know, such as a mate, a social companion, or a sibling In summary, routine procedures commonly performed in laboratories are stressful to the animals being used It may be concluded that significant fear and stress are predictable consequences of routine laboratory procedures Animals can remember past events that were painful or unpleasant, and they can anticipate and fear a repeat performance As science reveals more about the sensitivities and emotions of animals once dismissed as unfeeling things, whether or not humans should be deliberately harming animals in laboratories is likely to come under closer scrutiny Further Reading Balcombe, J P., Barnard, N., Sandusky, C 2004 Laboratory routines cause animal stress Contemporary Topics in Laboratory Animal Science 43: 42–51 Balcombe, J P 2006 Laboratory Environments and Rodents’ Behavioural Needs: A Review Laboratory Animals 40: 217–235 Berdoy M 2002 The laboratory rat: A natural history Film 27 minutes: www.ratlife.org Carbone L 2004 What animals want: Expertise and advocacy in laboratory animal welfare Policy Oxford: Oxford University Press Jennings M., Batchelor G R., Brain, P F., Dick, A., Elliott, H., Francis, R J., et al 1998 Refining rodent husbandry: the mouse Laboratory Animals 32: 233–259 Langford, D J., Crager, S E., Shehzad, Z., Smith, S B., Sotocinal, S G., Levenstadt, J S., et al 2006 Social modulation of pain as evidence for empathy in mice Science 312: 1967–1970 Jonathan Balcombe STRESS ASSESSMENT, REDUCTION, AND SCIENCE What Is Stress? Evidence is gradually accumulating that the majority of mammalian research animals, particularly rodents, are mentally stressed by their living conditions Stress in rodents will be specifically addressed because they account for about 90 percent of all research animals Stress is generally defined as a state in which an individual perceives that the needs for adaptation to a new or excessive demand or to a different environment exceed the personal resources that they have available Thus psychological as well physical components play a role in the stress response, at least in the more complex animals The physical aspect of the stress response is fuelled by stress hormones that flow through the body, altering every organ and biochemical function, with wide-ranging effects on metabolism, growth, and reproduction These changes may not necessarily result in a reduction in physical fitness, at least initially In addition, the animals’ physiological systems will be affected to a varying degree according to the threshold of the stress response for each individual animal Why Care If Laboratory Animals Are Stressed? If animals are under stress, they can have permanently raised concentrations of stress hormones In the case of rodents, those that cope by increasing their physical activity show high stimulation of the sympathetic autonomic nervous system and consequent release of epinephrine