Many young animals, like human children, are born with temporary teeth that eventually fall out and are replaced by permanent ones. These initial teeth are known as deciduous teeth, often called “baby teeth” or “milk teeth.” The presence and shedding of deciduous teeth vary widely across the animal kingdom. Not all species develop or lose baby teeth, as diverse dental strategies suit different lifestyles and dietary needs. This transition is a significant developmental milestone for many young creatures.
Mammals: The Primary Tooth Shedders
Mammals are the primary group of animals that commonly shed deciduous teeth. Puppies develop their first set of 28 needle-sharp deciduous teeth around three to four weeks of age. These baby teeth typically fall out when a puppy is about four to five months old, making way for 42 permanent adult teeth by six to seven months. Kittens develop 26 deciduous teeth, which are replaced by 30 permanent teeth.
Horses also undergo a dental transition. Foals are born with some incisors or develop them shortly after birth. They shed approximately 24 deciduous teeth, often called “caps,” between two and a half and four and a half years of age. These are gradually replaced by 36 to 44 permanent teeth by the time a horse reaches five years old. Many marine mammals, such as harbor seals, shed their deciduous teeth either in the womb or shortly after birth. This provides them with a functional set of permanent teeth early on, important for their short suckling periods and transition to an adult diet.
Why Animals Lose Their Baby Teeth
Animals lose their baby teeth for several biological and evolutionary purposes. A primary reason relates to growth and development; young animals have smaller jaws that cannot accommodate the larger, stronger teeth needed in adulthood. As an animal grows, its jaw size increases, necessitating a new set of teeth proportional to its adult dimensions. This allows for proper spacing and alignment, crucial for efficient chewing.
The dietary needs of young animals also differ from those of adults. Baby teeth are suited for an initial diet, such as suckling or soft foods. As an animal matures and its diet shifts to more solid or abrasive foods, permanent teeth become necessary. These teeth are designed for tearing meat, grinding plants, or other specialized functions. Permanent teeth are stronger and more durable, built to withstand the rigors of an adult animal’s lifetime and its feeding habits. Baby teeth can be prone to damage during a young animal’s active and playful stage, making replacement beneficial.
Animals That Don’t Shed Teeth
While many mammals shed teeth, numerous animal groups and some mammals do not, employing different dental strategies. Most reptiles, including crocodiles, alligators, and snakes, are polyphyodonts, meaning they continuously replace their teeth throughout their lives. A crocodile, for instance, can replace each tooth up to 50 times over its lifespan. Sharks are also polyphyodonts, constantly replacing their teeth in a conveyor-belt-like fashion.
Birds do not possess teeth, having evolved specialized beaks adapted for their diets. Although some birds have serrated bill edges for gripping food, these are not true teeth.
Within mammals, exceptions to tooth shedding exist. Baleen whales, for example, develop tooth buds in the womb, but these are reabsorbed before birth, replaced by keratinous baleen plates used for filter feeding. Toothed whales, such as belugas and dolphins, develop only one set of teeth that they retain for their entire lives. Rodents like mice, rats, and rabbits have incisors that grow continuously, necessitating constant gnawing to prevent overgrowth. Elephants, kangaroos, and manatees are polyphyodonts that continually replace their grinding teeth, with new ones moving forward in the jaw as old ones wear out and fall away.