Determining the age of a wild rabbit can be tricky. A lot depends on the type of rabbit, its sex and health. The cottontail is the most common small rabbit in the U.S. A tuft of white fur beneath the tail of an adult rabbit gives the cottontail its name. Females can have multiple litters a season, with three to six babies in each litter. Babies are weaned at 15 days, are independent in 28 days and reach breeding maturity at 125 days.
Examine the rabbit's eyes, ears and fur. A newborn is almost furless. Its eyes are closed and its ears folded. At five to seven days, the animal's eyes open. At nine days, its ears perk. The rabbit is covered with fur in 14 days. Cottontails leave the nest at 15 to 20 days.
Prepare the digital scale. If it doesn't have a tray, place an empty berry basket on top to hold the rabbit.
Turn on the scale. Let it calibrate with the tray or berry basket in place, if you are using one. The readout will blink.
Place the rabbit in the tray or basket and read the weight. Newborns weigh about 1 to 1.4 oz. Weaned babies weigh about 4 oz. Newly independent cottontails range from 4.5 to 5.5 oz. Mature adults weigh 28 to 43 oz. Rabbits gain 90 percent of their adult weight in the first four months. Females weigh more than males.
Measure the length of one of the cottontail's hind feet from ankle to toe with the measuring tape. Babies measure 21 to 32 mm. Adults average 95 mm.