Dolphins typically have between 100 and 200 identical teeth. Their teeth are typically shaped like cones to grab, grip, and secure prey before swallowing it whole. Dolphins may also use them to tear apart large chunks of flesh from their prey. Baby dolphins are born without teeth, and they gradually erupt from 2 to 5 months after birth. Once they erupt, these teeth will stay on for the dolphin’s life. In fact, scientists can age deceased dolphins based on the number of growth layers inside their teeth, the same way we can age trees. One dolphin species has a remarkably low number of teeth: 14 teeth maximum! This species is the Risso’s dolphin.
Between 4 and 14 teeth only!
Risso’s dolphins belong to the Delphinidae family, with bottlenose dolphins, killer whales, and pilot whales. Pilot whales are some of the closest relatives to Risso’s dolphins, and although their teeth count is pretty low compared to other dolphin species, they still have between 40 and 48 teeth. Risso’s dolphins’ low teeth count (between 4 and 14) is not the only particularity. Their teeth are also located on their lower jaw only, just like sperm whales, although up to two pairs of teeth may be found in the upper jaw (this is a rare case).
What do Risso’s dolphins eat?
With this low number of teeth, you might be wondering, “What do they eat?”. As we mentioned in the introduction of this post, dolphins do not chew their food. Instead, they tend to slurp their prey whole, which is the case here for Risso’s dolphins. Their teeth can be helpful, as they allow dolphins to secure the prey by pinching some of its soft tissue before slurping it.
Risso’s dolphins are medium to deep divers and like to forage along the continental shelf, where they target squids. Individuals stranded on the Mediterranean coast were found to have 25 different species of squid in their stomachs. To catch their prey, scientists believe Risso’s dolphins can hold their breath for over half an hour!
What is the other function of Risso’s dolphins theeth?
Risso’s dolphins are easily recognizable because of the number of scars on their body, so much that they look almost white. Scientists believe the scars are caused by the teeth of conspecifics and tentacles from their prey. There are two distinctive types of scars. The first type is round-shaped scars are typically caused by other species like squid, lamprey, and cookiecutter sharks, a small species of sharks known to steal chunks of flesh from bigger animals occasionally. The second type of scars we can find of Risso’s dolphins look like scratches.
These scratches come from other Risso’s dolphins; scientists call this phenomenon “raking.” Raking is the act of scraping their blunt teeth against the skin of another dolphin during fights, play, or mating. After the wound heals, it loses its pigments, causing the animal to turn white gradually. Older males are usually almost entirely white, which attests to their dominance and long fighting history.
Researchers also found bottlenose dolphins’ raking marks on juvenile Risso’s dolphins, which indicate that inter-species fights can happen too. Risso’s dolphins’ scars are really valuable to scientists because they allow them to identify individuals through photo-ID and understand the interactions between different species.
Sources and further reading
- Read more about cookiecutter sharks
- Paper on raking in Risso’s dolphins from the Mediterranean Sea
- Stunning infographic on Risso’s dolphins by the Cornwall mammal group
Did you like this post on Risso’s dolphins’ teeth? Check out our post on killer whales’ teeth next: