Whales exhibit remarkable diversity in their feeding structures. Their methods of acquiring food vary significantly, leading to distinct dental anatomies. Some species possess true teeth, much like land mammals, while others have evolved a filter-feeding system composed of specialized plates. This variation reflects different dietary needs and hunting strategies that have developed over millions of years.
The Composition of Toothed Whale Teeth
Toothed whales, or odontocetes, include species like dolphins, orcas, and sperm whales. These whales possess teeth structurally similar to those of many other mammals. Whale teeth are primarily composed of dentin, a calcified tissue that provides strength and resilience. Surrounding the dentin is a layer of cementum, which anchors the tooth to the jawbone.
Unlike human teeth, the presence and thickness of enamel in whale teeth can vary considerably. In many toothed whales, the outer layer is primarily cementum, with enamel often thin or absent. For instance, sperm whale teeth are largely composed of dense dentin, often referred to as ivory, with a thin or absent enamel layer. Killer whale teeth, however, do have an outer enamel layer protecting the crown. This composition provides durability for gripping and holding slippery prey.
Baleen Plates: A Different Structure
In contrast to toothed whales, baleen whales (mysticetes) do not possess teeth as adults. Instead, they have evolved baleen plates, a filter-feeding apparatus that hangs from their upper jaw. These plates are composed primarily of keratin, the same protein found in human hair and fingernails. Baleen grows continuously from the whale’s gum tissue, similar to how human nails grow, and is constantly worn down by feeding activities.
Each baleen plate consists of layers of keratin. Hundreds of these plates, often ranging from 150 to 400 per side, line the upper jaw, forming a comb-like structure. The inner edge of each plate frays into fine, hair-like bristles that interlock, creating a dense mat. The length and fineness of these bristles vary depending on the whale species and its diet, with some, like bowhead whales, having baleen plates up to four meters long.
How Whale Feeding Structures Function
The distinct compositions of whale teeth and baleen plates are directly related to their specialized feeding strategies. Toothed whales, such as orcas and dolphins, use their durable, conical teeth to grasp and hold prey. Their teeth are not used for chewing, but for seizing fish, squid, or marine mammals, which are then swallowed whole or in large pieces. The strength provided by their dentin and cementum, along with varying degrees of enamel, allows them to secure fast-moving and slippery prey.
Conversely, baleen whales employ their keratinous plates to filter small organisms from the water. Species like blue whales and humpbacks are “gulpers,” taking in mouthfuls of water and prey, then using their tongue to force the water out through the baleen plates, trapping krill and small fish against the fibrous fringes. Other baleen whales, like right whales, are “skim feeders,” swimming with their mouths open to continuously filter prey as water flows through their baleen. The flexibility and strength of keratin enable baleen plates to efficiently sieve food while withstanding pressure and constant wear of filter feeding.