A variety of vertebrate and invertebrate animal species has been used in research in the lab. All the species used so far are listed here.

Posted values of body mass, body temperature, and circa- dian period are means only. Since some species exhibit more variability than others, the accuracy of the posted values is variable. Most values were measured in our lab, but some were obtained from the scientific literature. (Body temperature values for ectothermic animals are indi- cated as N/A, meaning "not applicable".)

Samples of data obtained from individuals of some of these species are available in the Data Repository section of this web site.

Links to abstracts or full-text articles describing the re- search that involved these animals in our lab can be found in the Research and Publications sections.

The Nile Grass Rat

As a diurnal rodent of small body size, good tempera- ment, and short breeding cycle, the Nile grass rat (Arvicanthis niloticus) is an attractive laboratory animal for biomedical research. Like the standard laboratory rat, it is relatively insensitive to variations in photoperiod and does not hibernate. Unlike the laboratory rat, it reaches asymptotic body mass early in life and does not exhibit marked sexual dimorphism.

The genus Arvicanthis, tra- ditionally believed to contain five species including A. niloticus, belongs to the family Muridae, the large rodent family that includes the domestic mouse (Mus), the laboratory rat (Rattus), the hamster (Cricetus and Mesocricetus), and other rat-like rodents. The exact number of species within the genus Arvicanthis is still under debate.

The Nile grass rat, some- times also called unstriped grass mouse or Kuzu rat, is a chunky rodent with coarse, grayish brown fur. Adult head- and-body length is appro- ximately 13 cm, tail length is 10 cm, and body weight in captivity is 120 g. Females are slightly (6 g) lighter than males. The species' natural geographic distribution is restricted to the northern half of Africa, particularly the Nile Delta of Egypt, and to the southwestern Arabian Penin- sula, where it inhabits mostly grasslands and savannahs but also forests and scrubby thickets. Regular use of nests or burrows, particularly at night, has been observed both in the wild and under semi-natural laboratory con- ditions.

In temperament, the Nile grass rat is slightly more agitated than a laboratory rat but considerably more sedate than a squirrel. When group- housed from weaning, it can be easily handled as an adult. Single-housed indi- viduals tend to become hostile towards conspecifics and aversive to human handling. In the wild, Nile grass rats form social groups with several adult males and females. Longevity has been reported to be as long as 6 years for healthy individuals, although in our colony most animals have not lived past 2 years of age.

Laboratory colonies of Nile grass rats in North America are descendant of 29 in- dividuals trapped at the Masai Mara National Reserve in southwestern Kenya in 1993 by the research team headed by Professor Laura Smale at Michigan State University. The species breeds easily in captivity, particularly if pro- vided with plenty of bedding and a small refuge (such as a hollow PVC pipe) in the cage. The ideal ambient tempe- rature is 20-25 °C, and a short photoperiod (L11:D13) is recommended for proper gonadal function. Gestation lasts 23 days on average, and a new pregnancy can be initiated within a few hours of delivery of the previous litter if the male breeder is kept in the same cage as the female. Litter size varies from 5 to 9 pups. The pups are born with fur and can be weaned by 21 days of age. Infanticide and killing of the female by the male are occasionally observed, perhaps with a frequency higher than that encountered in the breeding of standard laboratory rats and mice, but they can be minimized by close moni- toring of the breeding pairs.

Much of biomedical research is conducted with non-human animal subjects. Although a small fraction of this research is directed at improvements in veterinary care, the major goal is to improve human health. Vivisection, or ex- perimentation with living organisms, is performed in animals for the benefit of humankind. Simply put, some research procedures are too harmful to be conducted on human sub- jects; so, we use animals instead. Of course, we also use animals (and plants and fungi, for that matter) be- cause they provide the opportunity for the study of complex human processes in simpler, more manageable "models". However, it cannot be denied that we often use animals in research because it would be inhumane to use human subjects for the same purpose.

The conduct of research with animals is strictly regulated in most of the world. In the United States, the use of animals in research is re- gulated by the Department of Agriculture (USDA) and, in all projects that receive federal funding, it must conform to detailed guidelines set out by the Public Health Service. Intentional infliction of pain is extremely rare and limited to research on the physiology of pain itself. Importantly, whe- ther pain is expected or not, every research project must be pre-approved by an ethics committee. The task of the various Institutional Animal Care and Use Committees (IACUCs) is to decide, based on the scientific and ethical values of the community, whether the discomfort cau- sed to the animals is justified by the expected benefits of the research project. Autho- rization to perform the project is denied if the justification is unsatisfactory.