A new study indicates that Americans gained up to 15 IQ points after the addition of iodine to salt became mandatory. In an effort to prevent goiter related to iodine deficiency, authorities ruled that iodine be added to U.S. salt products in 1924. The iodine, in addition to eliminating goiter, appears to have had an unexpected result: smarter Americans.
At peak lactation a black bear cub consumes about 30 ounces of milk a day, and a brown bear cub takes about 45 ounces. Thatâs per cub, so a mom with a litter of two or three cubs could be producing three or four quarts per day â a difficult metabolic feat to sustain.
Frequency of Birth. 1  Most adult females give birth once every three years. In populations with access to abundant food, birth occurs once every two years. 2  The most frequent litter size is two, followed by litters of one. Litters of three are less common than twins or singles, and litters of four are rare. Polar bears usually give birth to two cubs per litter. Cubs at Birth. At birth, polar bear cubs weigh about 454 to 680 g (16-24 oz.) and are about 30 cm (12 in.) long. Males are born slightly larger than females. Polar bear cubs are born small and helpless, with their eyes closed. The fur is very fine at birth, making the cubs look hairless. Care of Young