History of the Sprague Dawley Rat

The Sprague Dawley breed of rat, like those used in the current Psychology 381 class, is used widely throughout medical and psychological research.  Like other rat breeds used in research, the Sprague Dawley makes for a good general model for the study of human toxicology, reproduction, pharmacology, and behavioral research. The Sprague Dawley rat was first produced at Sprague Dawley farms, now a corporation called Harlan Sprague Dawley, and is widely used due in part to its calmness and ability to be handled easily.  However, characteristic of the species, the rat will still use its sharp incisors to bite if it is handled improperly. 

Sprague Dawley rats can live up to 3.5 years and grow to an adult body weight of 250-300 grams for females and 450-520 grams for males.  The breed also possesses a number of remarkable anatomical features. First, these rats are unable to vomit due to the placement of the esophagus as it enters the stomach.  Furthermore, these rats have no gall bladder, as well as a peculiar lung arrangement: the left lung has one lobe, while the right lung has four.  Most interestingly, Sprague Dawley rats produce secretions from their eyes when stressed that contain a pigment which, when dry, has the appearance of dried blood. These “tears” glow fluorescently under UV light.

Another advantage to using Sprague Dawley rats in research is the efficiency of their reproduction.  Both females and males become sexually mature at about 65 days old and the rats can breed throughout the entire year. The gestation period of the Sprague Dawley is only 22 days and litters can consist of up to 12 pups.  Pups can be weaned at around 3 weeks and females can begin cycling again only 2-4 days after weaning.

The tiny Sprague Dawley pups are born naked, blind, and entirely dependent on their mother for survival. However, the first couple weeks of a rat’s life are full of changes. The pup’s eyes begin to open around 2 weeks and they begin to eat an adult rat’s diet at around 3 weeks of age.  By 4 weeks they are completely independent.

It is important to mention that as a rat grows, health issues can overtake the animal quickly. One must understand the normal behavior and appearance of one’s rat in order to spot illnesses quickly, as rats do not usually shows signs of health issues until there is an emergency. It is a good idea to check rats for illnesses anytime there is an opportunity to handle them. One very important part of a body check is to look out for respiratory infections; one must pay attention to any abnormal breathing such as wheezing or congestion. It is also beneficial to check for lumps or swelling on all parts of the body. The eyes, ears, feet, and tail of the rat also tend to be prone to infection and should be checked regularly. Additionally, as in humans, a rat’s body temperature is a good indicator of illness and health changes.

On the whole, healthy, adult rats are fast learners and can be very easily trained with persistence, consistency, and patience. Rats are extremely smart creatures that are very capable of learning a wide variety of tricks, performing behaviors for research, and being loving, intelligent pets.


Ace Animals, Inc. (2006). Sprague Dawley. Retrieved September 9, 2008, from  http://aceanimals.com/SpragueDawley.htm.

RatGuide.com. (2000). Rat Guide: A Layman’s Guide to Health, Medication Use, Breeding, and Responsible Care of Pet Rats. Retrieved September 10, 2008, from http://ratguide.com/

Sprague Dawley Rat. (2008). Retrieved September 9, 2008, from the Wikipedia Wiki: http://en.wikipedia.org/wiki/Sprague_Dawley_rat

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