Number 90 Baba Penguin talking to mamma penguin

The polygamous polar bears mate in the spring (March to May); pairing only lasts for the actual mating with few permanent bonds observed. Testosterone levels increase in the spring for the males and the testicles increase in size.[citation needed] Once fertilized the females ova undergoes a delayed implantation, which takes hold in September or October. The gestation period is between 195 and 265 days (about 8 months) with the cubs born soon after the ova implant in early winter (November to December). The mother digs a two-chambered cave in deep snow for the birth in October after a period of heavily feeding. Usually, two cubs are born, less often one or three; litters of four cubs have been recorded. Like other Ursus bears, the new cubs are tiny, typically 30 cm long and weighing 700 g (a pound and a half), compared to their sometimes 300 kg (660 lb) mothers. The helpless and blind cubs open their eyes after about a month, emerge from the den at about 10 kg (22 lb), are able to walk at 1.5 months, and start eating solid food at 4-5 months. They remain with their mother, learning to hunt and protect themselves against adult males, which sometimes cannibalize cubs. Females nurse their young for up to two and a half years on milk that contains approximately 33% fat, higher than that of any other species of bear and comparable to that of other marine mammals.[8] The bears farther north tend to stay longer with their young, with weather conditions and age of the female affect this time as well. Sexual maturity is reached at 3-4 years. Adult polar bears are known to live over 30 years in captivity with average around 25. In the wild this is likely much shorter. Polar bears do not hibernate, though lactating females go into dormancy during denning. The female can control urea cycling so she can endure a long fast during this time[citation needed]; they often go without eating for a period of nine months and rely on stored body fat (also known as blubber) to keep themselves and their cubs alive. Once the cubs mature they go their separate ways.
The 2004 National Geographic study found no cases of cubs being born as triplets, a common event in the 1970s, and that only one in twenty cubs were weaned at eighteen months, as opposed to half of cubs three decades earlier.[21]
In Alaska, the United States Geological Survey reports that 42 percent of cubs now reach 12 months of age, down from 65 percent 15 years ago.[27] In other words, less than two of every three cubs that survived 15 years ago are now making it past their first year.

Some penguins mate for life, others for just one season. They generally raise a small brood, and the parents cooperate in caring for the clutch and for the young. During the cold season on the other hand the mates separate for several months to protect the egg. Usually, the male stays with the egg and keeps it warm, and the female goes out to sea and finds food so that when it comes home, the baby will have food to eat. Once the female comes back, they switch roles. Not all mating pairs of penguins are male and female.[4][5] When mothers lose a chick, they sometimes attempt to "steal" another mother's chick, usually unsuccessfully as other females in the vicinity assist the defending mother in keeping her chick. As the young grow, they assemble in large groups called crèches in some species, such as Emperor Penguins.