Flaws in the housing and handling of macaques used for research (2004)

Perretta, G., Reinhardt, V.

Abstract

Macaques are often caged individually regardless of their social disposition. The National Research Council of the United States admonishes that the common practice of housing rhesus monkeys [the predominant species used in biomedical research] singly calls for special attention. Approximately 10% of individually housed macaques engage in self-injurious biting. In single-caged rhesus macaque colonies the incidence of this behavioral pathology may be as high as 39%. Affected animals are severely distressed and, therefore, of little or no value for biomedical research. -- Macaques are commonly kept in double-tier systems to accommodate maximal numbers in one room. This creates differences in terms of terrestrial vs. arboreal and crepuscular vs. diurnal living environments for subjects caged in bottom vs. top rows. These differences are often overlooked or ignored in scientific articles in spite of the fact that they may influence research data in uncontrolled ways.-- Perches are a basic furniture of macaque cages. For convenience reasons, they are often placed at a height of only about 20 cm. Most cages, however, barely provide the occupant enough floor space to turn around without touching the walls of the cage. A too low perch further reduces this minimum space, thereby making it impossible for the animal to make species-typical postural adjustments with freedom of movement. -- Macaques are traditionally restrained with force during procedures such as drug administration and blood collection. This method of handling introduces avoidable stress as an extraneous variable into research data. The Appendix A of the European Convention for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (EST 123) is now under revision. How this new legislative document addresses the flaws outlined in this paper will be presented and discussed.