If you suspect an unplanned gerbil pregnancy, you'll know for sure in less than a month. The average length of gerbil gestation is 25 days. You can expect between four and six little gerbils, or pups, in a single litter. Constant reproduction is how gerbils form colonies in the wild, but that's probably not something you want going on in your house.
Female gerbils can become pregnant when they're between the ages of 2 months and 3 months old, or between 65 and 85 days days of life. Males are capable of breeding just a few days later, between days 70 and 85. Females go into their estrus, or heat cycle, for four to six days at a time. Unlike mammals that breed only in certain seasons, gerbils breed year-round. If you leave them unchecked, you could have a new litter nearly every month. Your female gerbil can keep cranking out litters monthly until the age of 2. Gerbil life span ranges between three years and five years.
Mating and Gestation
Gerbils breed at night. The entire breeding session can take a couple of hours, as they go through a specific gerbil mating ritual. Make sure you never have two breeding females in the same cage. They will fight, possibly to the death, over the male gerbil. The gestation period can be much longer than the typical 25 days if the female is bred again while nursing an earlier litter. Gerbils fertilized while simultaneously lactating can have a gestation period as long as 42 days.
Pregnancy and Birth
Gerbil mothers-to-be don't require much special care. If you don't know that your gerbil is pregnant, you might not realize it until a couple of days before the babies are born. Then you'll notice a swelling in her belly. Leave her alone when she starts giving birth. She'll clean each pup as they're born, then eat their placenta. Warning: If the male is in the cage with her during the birth, the pair might mate between deliveries. The already-born babies will be just fine during this two-hour love fest. It's quite likely that by the time she delivers the last of this litter, she's already got the makings of the next one within her, although egg implantation in her uterus could be delayed. Gerbil birth control isn't as simple as keeping the male and female apart, as gerbils mate for life and become depressed if separated. Your vet can solve the concern by neutering the male.
After the pups are born, leave the mother alone with them and make no changes to her living area, including replacing bedding, for a few days. You can start gently and briefing handling the pups when they are about a week old. By the age of 3 weeks, they're able to eat solid food. They won't be fully weaned until about the age of 5 weeks.
- gerbille image by jÃ©rÃ´me caffin from Fotolia.com