ADULT WEIGHT: 1-5.5lbs (500g-2.5kg). Varies considerably according to time of year (up to 40%).
ADULT DIMENSIONS: 17-24" (44-60cm) including tail. Male can be twice as large as female.
AVERAGE LIFESPAN: 5-6 years in laboratory. Up to 10 years pets (older have been known).
CHROMOSOME COUNT: 40
RESPIRATORY RATE: 30-40 per minute.
HEART RATE: 220-250 beats per minute.
RECTAL TEMP: Average 38.8C (101.8F). Range 37.8-40C (100-104F).
TEETH: Incisors 3/3, canines 1/1, premolars 3/3, molars 1/2. Supernumary incisors common.
TOES: 5 on each foot.
NIPPLES: 8 (male and female).
VERTEBRAE: C7, T14, L6, S3, COL14-18. 14 pairs of ribs.
OTHER ANATOMY: No caecum, appendix and male prostate gland. Sweat glands not well developed.
ENVIRONMENT: Optimum 15-20C (60-70F max.). Heat prostration likely at 32C 90F).
SEXING: Ano-genital distance of male at least twice that of female.
PUBERTY: 240-250 days.
SEXUAL MATURITY: 9-12 months, or the spring following birth.
AGE TO BREED: Male 365 days, female 275 days.
BREEDING SEASON: Photoperiodically triggered - possibly 16 hours daylight. Main breeding season March - August in Britain (male testes begin to descend December/January and regress by July, female in oestrus any time from March to October.
SEASON SIGNS: Female has swollen vulva, male has swollen testes.
DURATION OF OESTRUS: Continuous until mated or until end of season and very prolonged if unmated. Ovulation induced by male stimulus (behaviour and coitus).
DURATION OF MATING: 10 minutes to several hours - probably 1 hour on average.
OVULATION: 30 hours after mating.
REDUCTION OF VULVA: 7-10 days, complete within 2-3 weeks of mating.
PALPATION: 10 days after vulva reduced.
GESTATION: Average 42 days. (Range 38-44 days; at 45 days kits die.)
LITTERS PER YEAR: Two possible (up to 5 under controlled photoperiod).
NESTING: Starts building 10-12 days before birth.
OTHER BIRTH SIGNS: Mammary glands.
POST-NATAL OESTRUS: 1-2 weeks after weaning.
LITTER SIZE: 2-17 (average 8, norm. 6-9) - more in first litter of season than in second.
BIRTHWEIGHT: .5oz (5-15g).
DECIDUOUS TEETH: Begin to erupt at 10-14 days.
CANINES: 47-52 days.
EYES/EARS OPEN: 21-37 days.
FUR: Almost naked at birth, some by 9 days, good woolly coat by 4-5 weeks.
OUT OF NEST: First ventures usually 3-4 weeks.
WEANING WEIGHT: 10.5-17.5 oz (300-500g).
ATTAIN ADULT WEIGHT: 4 months.
1st POSSIBLE MATING: 6 months.
1st NORMAL MATING: 12 months.