Comments & suggestions  should be directed to jroese@lssu.edu Visit my website Behavior Unlike their wild counterparts, domestic rats are not aggressive and are easy to work with. Aggression may be strain related, and the Long-Evans and Fischer 344 strains are said to be more aggressive.  Frequent and gentle handling reinforces non-aggressive behavior tendencies.  Rats make excellent pets, are intelligent, and easily trained.  These traits have made them an excellent choice for behavior and learning studies.  Rats are nocturnal animals, and are most active at night and in the early morning.  If given a choice, rats prefer small, dark confined spaces.  This is not surprising as wild rats reside in burrows.  Rats are social and communal creatures, and several males and females grouped together can coexist peaceably if cage space is adequate.  Male rats housed together do not show the same aggressive tendencies towards one another that male mice exhibit.  Same sex pairs can be housed together to allow social interactions without the production of young.  Females with young will sometimes be intolerant of the presence of other females.  Unlike mice, escaped rats will often return to their cages. Diet and Nutrition Rats in research facilities are generally fed a pelleted rodent diet ad libitum.  Maintenance diets generally contain 5% protein.  Young animals and females used for breeding require 15% protein.  An adult rat will consume about 5 - 6 grams of feed per 100 grams of body weight per day.  Young rats may not be able to reach the food, so it is acceptable to put food on the floor of the cage until they are able to eat from the hopper.  Food should not be used more than 6 months after the milling date.  Rats are extremely cautious about ingesting foods they are unaccustomed to.  If a switch to an entirely different type of diet must be made (e.g. chemically defined diet), it is probably best to introduce the new diet slowly in combination with the old ration. Water may be provided by bottles and sipper tubes or by automatic watering systems.  Cages should be checked daily to ensure that water is not leaking into the cage and soaking the bedding. An adult rat will consume about 10 - 12 ml of water per 100 grams of body weight per day.  Young rats may require a longer sipper tube in order to reach the water source. Animal Identification Identification schemes vary according to the needs of the researcher.  Cage card identification may be adequate for many circumstances, however, more precise methods may be required when individuals within a cage need to be readily identifiable.  Ear notching is probably the most commonly used technique.  Appropriately sized, numbered  metal ear tags may also be used.  Toe clipping may only be used to identify neonates.  Temporary identification of a rat may be accomplished by dying or clipping the fur, or marking the tails with an indelible marker.  Hooded rats may be identified by their coat color pattern using photographs or drawings.  Subcutaneously implanted microchips can also be used to identify individual animals. Acclimatization Transportation of animals is stressful and leads to physiologic changes such as increased cortisol levels, which may potentially alter research results.  Rats received from another site need to have adequate time to recover from shipping stress.  The length of time required depends on the distance and time involved in transporting the animals.  A quarantine/holding period allows the rats to adapt to their new surroundings and also permits observation for any signs of infectious disease.