Male vs. Female Rat

Rats are highly intelligent and social creatures that thrive in stimulating environments. It’s recommended that pet rats be kept in pairs or groups. Unless you’re planning on taking on the responsibilities of breeding you’ll want to ensure that you stick to either all males or all females for your pairs or groups. If you’re considering pet rats, you may want to learn some differences between the sexes. We’ll dive into the details of a male vs. female rat including how to tell them apart, which lives longer, and which makes for a more cuddly companion.

Comparing a Male and Female Rat

Key Differences Between a Male and Female Rat

Both male and female rats are social, curious and intelligent rodents that can be excellent additions to the family. Key differences between a male and female rat are their size, sexual characteristics, behavior, odor and role in reproduction.

Male vs. Female Rat: Size

The difference in size is subtle between male and female rats, but females do tend to be smaller than males. Generally, male rats have a broader body shape while females are more streamlined and narrow. Adult females weigh an average of 12-16 ounces and males weigh in at 16-23 ounces. Both males and females are 9-11 inches long in body length.

Male vs. Female Rat: Sexual Characteristics

As adults, rats can easily be identified by sex but as babies it will be more of a challenge. To sex baby rats you can check the distance between their anus and urethra. From birth, this distance will be smaller on females than it will be on males. At about 13 days old teat marks will begin to show on females. Small testicles will be visible on male rats at around 19 days.

By the time rats reach maturity, the physical differences between males and females will be quite obvious. Large testicles become clearly visible by 3 weeks on male rats and you can check for nipples on an adult female rat. Although rare, nipples will sometimes be visible on male rats.

Male vs. Female Rat: Lifespan

Rats have an average lifespan of 2-3 years both as pets and in the wild. In rare cases, pet rats may live to be 6-7 years old. The oldest rat ever recorded was a male who lived to be 7 years and 4 months of age. Many studies have suggested that female rats actually tend to live a bit longer than males but the difference is not significant. 

Male vs. Female Rat: Behavior

Male rats tend to be quite cuddly and affectionate pets with a mellow temperament. They are likely to enjoy snuggling up with you for some head scratches. If you want a more independent and adventurous companion, a female rat may be the pet for you. Female rats are quite active and like to get busy exploring. These behavioral traits are only generalizations and independent personalities will vary wildly.

Male vs. Female Rat: Odor & Marking

Rats sometimes get a bad rap, but they are actually extremely clean companions and can be litter trained. Female rats don’t have any odor when they’re cared for properly with adequate stimulation and space. Male rats do tend to have a distinct odor. Rats have a biological need to mark their environment with small amounts of urine. These droplets are generally odorless and simple to clean. Both males and females mark but female rats may mark a bit less than males. Marking frequency is related to hormone levels and will fluctuate with males testosterone levels and with females when they go into heat.

Male vs. Female Rat: Sexual Maturity & Reproduction

Female rats reach sexual maturity at 8-12 weeks and male rats at 6-10 weeks of age. If you have males and females they should be separated at about 5 weeks unless you are intentionally breeding them. Female rats go into heat every 4-5 days year round. Their heat cycle will typically begin in the evening and last through the night. Although female rats can get pregnant at 5-6 weeks old, it’s recommended that they are not bred until they reach 3-4 months of age. Their gestation period is 21-23 days and a pregnant rat will typically wait until the day before or the day of birth to build a nest. She will give birth to an average of 8-12 babies per litter.

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