The common brown rat, Rattus norvegicus, is a species found across the globe. They are widely kept as domesticated pets and used in scientific research. Male and female rats exhibit distinct differences in their biology and behavior. Understanding the traits of male rats, called bucks, is helpful for proper care and handling.
Identifying Male Rats
Distinguishing male rats from females is straightforward, particularly in adults. The most significant difference is size, with males being larger and heavier than females. Adult bucks weigh between 450 and 650 grams, whereas females average 350 to 450 grams. This size difference results in a broader, bulkier body shape in males compared to the streamlined build of females.
Specific anatomical features also confirm a rat’s sex. Adult male rats have prominent testicles that are easily visible. In young pups, these may not have descended. In these cases, sex is determined by the anogenital distance—the space between the anus and genital opening. This distance is greater in males than in females and can be observed from birth.
Behavioral Traits of Male Rats
The temperament of male rats differs from that of females, which is a consideration for pet owners. Bucks are often calmer and more sedentary than females. This means they are more inclined to rest and cuddle with their owners. Females, by contrast, are more active and curious, spending more time exploring their environment.
Male rats engage in scent-marking as a form of communication and to establish territory. This testosterone-driven behavior results in males having a stronger, musky odor than females. They may leave small drops of urine on surfaces, a natural behavior that is more pronounced than in females. Male rats can be housed together successfully, especially if they are littermates or introduced at a young age. Hormonal changes can lead to dominance disputes or aggression that requires intervention.
Considerations for Keeping Male Rats
Proper care for male rats involves attention to their housing, social needs, and health. A spacious, well-ventilated wire cage is suitable, with enough room for sleeping, eating, and activity areas. The flooring should be solid or covered with a safe substrate, like recycled paper or shredded newspaper, to protect their feet and respiratory systems from dust and ammonia. Daily cage cleaning is recommended to maintain a healthy environment.
Male rats should be kept in pairs or small groups to satisfy their social needs. Introducing new males to an established group should be done gradually and with supervision to minimize conflict. A common health issue for bucks is “buck grease,” an oily, orange-tinted secretion from skin glands that can accumulate on the back and may require cleaning. Older male rats are also prone to hind-limb degeneration, a condition that affects their mobility.
Reproductive Aspects and Scientific Use
Male rats reach sexual maturity between 6 and 10 weeks of age. At this point, they are capable of reproduction. To prevent unwanted litters, males should only be housed with other males. If keeping a mixed-gender group, neutering the male is a common procedure that prevents breeding and can reduce hormone-driven behaviors like aggression and scent marking.
Male rats are also a fixture in scientific and medical research. Their physiological and genetic similarities to humans make them suitable models for many studies. They are used in neurological, behavioral, and pharmacological research to understand diseases and test new treatments. Their consistent biology allows researchers to conduct controlled experiments that yield data for human health applications.