Ever bought a pocket pet, named him Henry, and a week (and six babies) later, discovered that “he” was actually a Henrietta?  Sexing small animals is not an easy task, especially if they’re very young.  Below are some general tips on sexing your small pet and detecting pregnancy if she’s a Henrietta.  Note: In order to prevent a population explosion, babies should be separated from their mother shortly after they are weaned.


 MICE:  The distance between the anus and the urinary/genital opening is much longer in males than in females.  Females also have nipples that become apparent by ten days of age and then become covered with fur as the mouse matures.  Testicles in adult males can be felt at the base of the tail. See photos at: www.peteducation.com.

 Pregnant?  A pregnant mouse may begin showing at 14 days.  She may spend her time building a nest and / or take offense to being handled, or she may look like she’s swallowed a golf ball!  After a typical gestation period of 17 to 21 days, she will give birth to a litter that averages between 8 and 12 young.  Weaning occurs at approximately four weeks of age.


 RATS:  Rats are similar to mice in that the location of the male genitals is farther up the abdomen than that of the female. Females also have nipples, and the male’s testicles will have descended by five weeks of age.

 Pregnant?  Again, similar to mice, a pregnant rat may show at 14 days.  She will display a bulging midsection, may take to building a nest and be reluctant to be held.  Her gestation period is a bit longer, perhaps 21 to 23 days, and she will give birth to a litter between 6 and 12.  Young rats will be weaned at two weeks.


 HAMSTERS:  As with both mice and rats, the distance between the anus and the urinary/genital opening is much longer in males than in females.  Females will have nipples, which may be more difficult to see in dwarfs or if the hamsters have acquired a thick coat.  At four weeks, Syrian males will have noticeable testicles.  Dwarfs’ testicles are less obvious because of their size; however, male dwarfs have a scent gland located near their navel. See diagrams at: www.hamsterific.com

 Pregnant?  A female hamster will typically begin showing at approximately ten days.  You may be able to spot a bulging belly when she stands up on her hind legs, and her behaviour may change.  Pregnant hamsters also may begin hoarding food or bedding.  She will give birth to between six and eight young after a gestation period of 16 to 18 days, and then wean her young at 21 days.


 GUINEA PIGS:  The traditional “i” (male) and “Y” (female) determiners can often be confusing.  Pressing gently, but firmly, around the genital area will either extrude a male’s penis or display a Y-shaped opening to indicate a female.  The inner part of the shaft underneath the male’s skin can also be felt as a “ridge” over the penis.  In addition, young males exhibit a donut shape around their rectum where their testicles are. Photos can be accessed at: www.cavyspirit.com

 Pregnant?  The female guinea pig may start drinking more water and look heavier at five weeks.  You may notice that her abdominal muscles feel tighter to the touch and may even be able to discern an outline of the babies in utero.  A litter of three to four will be born after 60 to 70 days, and will be weaned somewhere in the 14 to 28 day range.


 RABBITS:  Attempting to sex young rabbits requires close examination.  Gentle pressure in the genital area will cause either a slit banded in pink (indicating a female) or a blunt white tube (indicating a male) to appear.  As rabbits mature, the male will be distinguished by his more angular appearance and descending testicles. Photos are available at: www.rabbitnetwork.org

 Pregnant? It is nearly impossible to observe pregnancy in a rabbit as she may not show until she’s about to deliver.  Gestation will last from 28 to 31 days.  She may pluck out her fur and collect hay for nesting, or exhibit more aggressive behaviour than usual during this time period.  The only reliable method to confirm pregnancy in a rabbit is to have a veterinarian, or qualified breeder, palpate her abdomen.  She will carry from four to eight young and wean them at five to seven weeks