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MEASUREMENT AND WEIGHT- Editorial Comment

Editorial Comment

(Editorial Overview Text Replicated on Overall Species page - Ursus maritimus - Polar bear)

LENGTH
Adult: 
Males reach about 2.0 - 2.6 m (79 - 102 inches) nose tip to tail tip; females are slightly shorter at 1.8 - 2.0 m (71 - 79 inches). 
Newborns: Cubs have been measured as 24 - 30.5 cm (9.5 - 12 inches) nose to tail base, and one was 34 cm (13.4 inches) nose to tail.

HEIGHT
Adults and sub-adults: Adult polar bears may measure 1.3 - 1.6 m at the shoulder (51 - 63 inches).
Juveniles: --

WEIGHT
Adult: 
Weights of males vary from 300 to 730 kg (660 - 1,610 lb), with some estimated up to 800 kg; females weigh 150 to about 400 kg (330 - 880 lb).
Newborns: Newborn cubs weigh about 0.6 kg (1.3 lb) at birth.

GROWTH RATE: Cubs may reach 3.5 kg at one month, 5.5 kg by two months and 11 kg by three months (based on zoo data). When they leave the maternity den in March or April, wild cubs weigh 10 - 15 kg (22 - 33 lb). At one year old, yearlings weight 90 - 160 kg (98 - 353 lb) and at two years old, 170 - 200 kg (375 - 441 lb). Females reach adult weight by about five years, males not until eight to twelve years of age.

(References are available in detailed literature reports below)

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Length

Adult

SUMMARY: Males reach about 2.0 - 2.6 m (79 - 102 inches) nose tip to tail tip, large males may reach 2.85 m; females are slightly shorter at 1.8 - 2.1 m (71 - 82.6 inches) with large females to 2.47 m. 
  • Head and body length 2.0 - 2.5 m. (B147)
  • Length 2.13 - 3.35 m (7 - 11 ft). (B180.w4)
  • Males 2.41 - 2.51 m (8 - 8.4 ft); females 1.8 - 2.1 m (6 - 7 ft). (B144)
  • Males up to 285 cm. (B490.27.w27)

Nose tip to tail tip:

  • Males 2.0 - 2.5 m. (D244)
  • Females 1.8 - 2.0 m. (D244)
  • Males 2.0 - 2.5 m (6.5 - 8.3 ft). (B285.w4)
  • Females 1.8 - 2.0 m (58 - 6.5 ft). (B285.w4)
  • Males 200 - 260 cm (79 - 102 inches) nose tip to tail tip. (B406.37.w37)
  • Females 180 - 200 cm (71 - 79 inches). (B406.37.w37)

Neonate / Young

SUMMARY: Cubs have been measured as 24-30.5 cm nose to tail base, and one was 34 cm nose to tail.
  • A new-born cub was 34 cm nose-to-tail. (J462.236.w1)
  • Two cubs were measured at 10.25 and 9.5 inches nose to tail base. (B288.w11)
  • A hand-reared cub grew as follows: day 1, 30.5 cm (snout tip to root of tail); day 36, 50.0 cm; day 64, 57.0 cm; day 85, 64.0 cm; day 106, 76.0 cm; day 134, 101.5 cm; day 292, 135 cm. (J46.117.w1)

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Height

Adult

SUMMARY: Adult polar bears may measure 1.3 - 1.6 m at the shoulder (51 - 63 inches), even 1.7 m for large males.
  • Shoulder height up to 1.6 m. (B147)
  • Shoulder height about 1.2 m (4 ft). (B180.w4)
  • Shoulder height 1.3 - 1.6 m. (D244)
  • Up to 1.6 m (5.3 ft). (B144)
  • 130 - 160 cm (51 - 63 inches). (B406.37.w37)
  • 1.7 m for large males. (B490.27.w27)

Neonate / Young

  • --

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Weight

Adult

SUMMARY: Weights of males vary from 300 to 730 kg (660 - 1,610 lb), with some estimated up to 800 kg; females weigh 150 to about 400 kg (330 - 880 lb).
  • This species shown a cline in size: smallest at Spitzbergen and largest in the Bering Strait. (D244)
    • Note: this is no longer accepted. (V.w100)
    • Reports of a cline in size may be due to nonstandardized collection methods. (B490.27.w27)
  • Variations between populations are probably due to population density, ecosystem productivity and recent climatic conditions affecting feeding success. (V.w100)
  • In western Hudson Bay, a decrease in body mass was noted for most age and sex classes of polar bears for the period from before 1980 to 1992; for females, mass declined by about 1.92-3.25 kg per year over a period of ten years. (J30.73.w2)
  • Weight about 420 - 500 kg (925 - 1,100 lb). (B180.w4)
  • 320 - 410 kg (704 - 902 lb). (B144)
  • Males:
    • 300 - 800 kg. (B147, D244)
    • 400 - 600 kg (880 - 1,320 lb). (B285.w4)
    • Usually 420 -500 kg. (B147)
    • Males can reach 1,000 kg (2,200 lb). (B144)
    • The average of nine males was 900 lb, with the heaviest being 1,028, although a male of more than 1,600 lb has also been recorded. (B288.w11)
    • 300 - 730 kg (660 - 1,610 lb). (B406.37.w37)
    • Mean weight of 94 males more than five years old in Hudson Bay was 489 kg, with the largest 654 kg; in Alaska the heaviest male was 610 kg. Males too heavy to be lifted have been estimated to weight 800 kg. (B490.27.w27)
  • Females:
    • 150 - 300 kg. (B147, D244)
    • 200 - 350 kg, exceptionally to 500 kg plus (440 - 770 lb, exceptionally to 1,100 lb plus). (B285.w4)
    • The average of seven females was 700 lb. (B288.w11)
    • 150 - 400 kg or more (330 - 880 lb). (B406.37.w37)
    • Peak weight usually do not exceed 400 kg. (B490.27.w27)

Neonate / Young 

SUMMARY: Newborn cubs weigh about 0.6 kg (1.3 lb) at birth.
  • About 0.6 kg. (D244)
  • About 600 g at birth. (B147)
  • About 0.6 kg (1.3 lb). (B285.w4)
  • About 0.9 kg (2 lb). (B180.w4)
  • Two cubs were weighed at 1 lb 3 oz and 1 lb 10.75 oz and were measured at 10.25 and 9.5 inches nose to tail base. (B288.w11)
  • Zoo data: 440 - 775 g. (D247.6.w6)
  • 1.25 lb (567 g). (J23.4.w1)
  • Two cubs weighed 570 g and 706 g at birth. (J23.14.w3)
  • Two cubs weighed 673 g (at two hours) and 580 g (at two days). (J462.236.w1)
  • About 0.6 kg (1.3 lb). (B406.37.w37)
  • Weights of 610g and 600 g for two cubs at a few hours old at Denver Zoological Gardens. A cub which did not survive but appeared fully developed weighed 750 g. For ten hand-reared cubs in zoos, range 570 - 750 g, mean 657 +/- 53.7 g. (J23.39.w1)
  • About 600-700 g at birth. (B490.27.w27)

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Growth Rate

SUMMARY: Cubs may reach 3.5 kg at one month, 5.5 kg by two months and 11 kg by three months (based on zoo data). When they leave the maternity den in March or April, wild cubs weigh 10 - 15 kg (22 - 33 lb). At one year old, yearlings weight 90 - 160 kg (98 - 353 lb) and at two years old, 170 - 200 kg (375 - 441 lb). Females reach adult weight by about five years, males not until eight to twelve years of age.
  • The individual cub growth rate (birth to weaning) is 120.2 g/day, with a litter growth rate of 228.4 g/day. (P17.57.w2)
  • At the time of emergence from the den (March or April), 10 - 15 kg (22 - 33 lb). (B147, B406.37.w37, D244)
  • Cubs in Alaska, from a birth weight of about 600-700g, average 13 kg at the time of den emergence (late March to early April), some being 22 kg, and may exceed 100 kg approaching one year of age. They can double their weight from one year old to two years old. (B490.27.w27)
  • Zoo data: Average weight at one month 3.5 kg, at two months 5.5 kg and at three months 11.0 kg. (D247.6.w6)
  • Two cubs gained weight from 570 g and 706 g at birth to about 2.25 kg by one month and about 5.25 kg by two months. (J23.14.w3)
  • At one day, 1 lb (567g) ; at 36 days, 6 lb (2.72 kg); at 64 days, 12 lb (5.44 kg); at 85 days, 18 lb (8.16 kg). (J23.4.w1)
  • Cubs at Denver Zoological Gardens, some mother-reared, some hand-reared, weighed 1340 - 1550 g at two weeks, 1160 - 2600 g at four weeks, 2300 - 4410g at six weeks, 3400 - 6160 g at eight weeks, 4390 - 8100 g at ten weeks and 5580 - 10000 g at twelve weeks. It was noted that cubs could double their weight in two weeks on their mother's fat-rich milk. In two sets of male-female twins, the growth rate of the male was detectably greater than that of the female as they approached ten weeks of age. A singleton mother-reared cub was not significantly larger than twins at two eeks of age, but by 12 weeks it was 5-44% larger than a single hand-reared cub, twin hand-reared cubs and twin mother-reared cubs. (J23.39.w1)
  • A hand-reared cub from Prague Zoo gained weight as follows: day1, 648g; day 36, 2.84 kg; day 62, 5.62 kg; day 85, 8.66 kg; day 106, 13 kg, day 134, 19.47 kg; day 162, 31.4 kg; day 190, 42.4 kg; day 219, 54.5 kg; day 247, 67.5 kg; day 267, 72.0 kg; day 292, 79.7 kg. (J46.117.w1)
  • At one year, 45 - 80 kg. (D244)
  • Two-year-olds, 70 - 140 kg. (D244)
  • In spring, at the time families first emerge from maternity dens, cubs weigh 10-15 kg (22 - 33 lb), yearlings about 45 - 80 kg (100 - 176 lb), while two-year-olds weigh 70 - 140 kg (154 - 309 lb). By August, cubs-of-the-year weigh 50 - 110 kg (110 - 40 lb), yearlings 90 - 160 kg (198 - 353 lb), two-year-olds 170 - 200 kg (375 - 441 lb). Note: weights vary with area and year. (B406.37.w37)
  • Females reach adult weight by about five years, males by eight to ten years. (D244)
  • Female reach adult weight by about five years, males not until 10 - 11 years old. (D244)
  • Growth rates may vary between populations. Female polar bears in western Hudson Bay were found to have higher growth rates than those from several other populations; they also had an earlier age at first breeding. (J46.245.w1)
  • A cub caught in Alaska on 29th March (about the time of usual emergence of cubs from the den) weighed 8.9 kg. (J462.236.w1)

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Authors & Referees

Authors

Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)

Referee

Andrew Derocher (V.w100)

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