<P> The word "kitten" derives from the Middle English word kitoun, which in turn came from the Old French chitoun or cheton . Juvenile big cats are called "cubs" rather than kittens; either term may be used for the young of smaller wild felids, such as ocelots, caracals and lynx, but "kitten" is usually more common for these species . </P> <P> A feline litter usually consists of two to five kittens born after a gestation lasting between 64 and 67 days, with an average length of 66 days . Kittens emerge in a sac called the amnion, which is bitten off and eaten by the mother cat . </P> <P> For the first several weeks, kittens are unable to urinate or defecate without being stimulated by their mother . They are also unable to regulate their body temperature for the first three weeks, so kittens born in temperatures less than 27 ° C (81 ° F) can die from hypothermia if their mother does not keep them warm . The mother's milk is very important for the kittens' nutrition and proper growth . This milk transfers antibodies to the kittens, which helps protect them against infectious disease . Newborn kittens are unable to produce concentrated urine, and so have a very high requirement for fluids . Kittens open their eyes about seven to ten days after birth . At first, the retina is poorly developed and vision is poor . Kittens are not able to see as well as adult cats until about ten weeks after birth . </P> <P> Kittens develop very quickly from about two weeks of age until their seventh week . Their coordination and strength improve . They play - fight with their litter - mates and begin to explore the world outside the nest or den . They learn to wash themselves and others as well as play hunting and stalking games, showing their inborn ability as predators . These innate skills are developed by the kittens' mother or other adult cats, who bring live prey to the nest . Later, the adult cats demonstrate hunting techniques for the kittens to emulate . As they reach three to four weeks old, the kittens are gradually weaned and begin to eat solid food, with weaning usually complete by six to eight weeks . Kittens generally begin to lose their baby teeth around three months of age, and have a complete set of adult teeth by nine months . Kittens live primarily on solid food after weaning, but usually continue to suckle from time to time until separated from their mothers . Some mother cats will scatter their kittens as early as three months of age, while others continue to look after them until they approach sexual maturity . </P>

When do kittens start regulate their body temperature
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