Changing the Housing Standard for Monkeys in Laboratories

Biomedical and psychological testing conducted with monkeys is often tainted by unresolved ethical questions. Although animal advocates tend to focus their concerns on cruel experimental procedures, the resultant suffering from a particular test is usually of a relatively short duration. The sum total of suffering inflicted is much more pervasive when one examines the monkeys’ housing conditions prior to the experiment—conditions which may cause continuous suffering lasting for years on end.

The standard monkey cage is so small that the imprisoned animal cannot take a few normal steps in either direction, let alone run or jump. Usually, cages are devoid of high perches that would at least enable a monkey to make use of the vertical dimension of the cage. Permanent confinement in such extremely small, barren enclosures causes many individuals to develop the monotonous habits of stereotypically pacing back and forth, running in circles, somersaulting or bouncing up or down. These movement patterns reflect a frustrated need for exercise and become deeply ingrained over time. Ironically, scientific investigators label these behaviors—rather than the cage size—as abnormal.

Further, in order to minimize housing expenses, monkeys are commonly kept in doubletier cages, with one row stacked on top of another. This doubles the number of animals that can be accommodated in one room, but involves serious adverse welfare implications for the individual animals. Those relegated to the lower rows are restricted to a quasi-terrestrial lifestyle for which they are not adapted biologically. They are unable to withdraw in alarming situations and retreat to a safe place above the human “predator” who periodically captures them and subjects them to uncomfortable, painful, distressing, life-threatening, or even deadly procedures. Moreover, they are forced to live in a shady, depressingly dark environment with light often so dim that caretakers have to use flashlights to identify and inspect them.

The striking difference of illumination between upper and lower cage rows belies the scientific principle that environmental variables must be controlled strictly to ensure the validity of collected research data. Biomedical investigators presumably should be adamant that research animals be kept in a standardized environment in which extraneous variables such as illumination (which can affect almost all functions of the body) are as uniform as possible for all research subjects. Nonetheless, there seems to be a tacit agreement among primatological researchers to exempt this variable from rigorous scientific methodology since, in order to meet a uniform standard, all cages would have to be arranged at the same level of the room and the number of available animals, therefore, would be cut in half.

Both human and nonhuman primates are distinguished by a high degree of sociality, which is a basic condition for their survival in the wild. They possess an inherent need for social contact and interaction. Laboratory monkeys, however, are commonly kept in single-cages, thus being deprived of direct contact with conspecifics.

Permanent solitary confinement is extremely distressing for human and nonhuman primates alike. As is the case with incarcerated humans, individually caged monkeys show signs of boredom, depression, frustration and anger, resulting in unmistakable signs of mental disturbance. Distinguished scientists recently acknowledged that “approximately 10% of captive, individually housed monkeys have had some veterinary record of self-injurious behavior within their life-time.” This means that 10 out of every 100 research monkeys bite themselves to the point of serious injuries when being housed in the traditional, single-caging system.

What prompts investigators to imprison innocent nonhuman primates under living conditions that are regarded as a cruel form of punishment for convicted human primates?

For one, many investigators are seemingly unaware of how their research animals are housed. A well-known biomedical scientist made the following observation in a professional journal: “Most investigators think only briefly about the care and handling of their animals and clearly have not made it an important consideration of their work.” If scientists don’t care enough to verify that the research animals they use are housed in accordance with sound scientific methodological principles, there is little hope that they will support efforts to refine current housing practices.

Another consideration is money— some would say greed. It is certainly true that upgrading cheap monkey housing conditions requires additional financial investment, but this initial investment will quickly yield important returns. Better housing conditions will lead to more valid scientific data, therefore reducing the number of animals needed to obtain the information. Money is saved and animals’ lives are spared.

—Viktor Reinhardt, Adam M. Roberts and Annie Reinhardt

Photo, The traditional double-teir caging system for laboratory monkeys relegates 50% of the animals to a cave-like housing environment as well as permanent solitary confinement. (photo by Viktor Reinhardt/AWI)