Risso's Dolphin: a two-minute wildlife lesson

Dolphins · day 6 of 7

Five facts

1. Long white lines from rough play with other dolphins slowly cover its body. The marks do not darken again, so they pile up.
2. At 300 to 500 kg, it is the heaviest of all the animals that we call dolphins.
3. To reach squid more than 600 m down, it breathes out, then spins several times to plunge almost straight down.
4. Most have only two to seven pairs of teeth, and every one of them sits in the lower jaw.
5. Since at least 2017, these dolphins have been turning up off the coast of subarctic Norway. Their range seems to be growing.

The quiz

1. Where do most of a Risso's dolphin's white scars come from?

• Sunburn
• Contact with other Risso's dolphins (correct)
• Rubbing on ice
• Shark bites

The scars come mostly from social contact with other dolphins.

2. How much does a Risso's dolphin weigh?

• 5 to 10 kg
• 30 to 50 kg
• 300 to 500 kg (correct)
• 2,000 to 3,000 kg

It weighs 300 to 500 kg, the most of any species called dolphin.

3. How does it dive deep after squid?

• It holds a stone to sink
• It rides a current down
• It swims backwards
• It breathes out and spins (correct)

It empties its lungs and spins to descend almost vertically.

4. Where are a Risso's dolphin's teeth?

• Only in the lower jaw (correct)
• Only in the upper jaw
• In both jaws, over 50 pairs
• It has no teeth at all

Its two to seven pairs of teeth are all in the lower jaw.

5. Where have Risso's dolphins started showing up since at least 2017?

• In the Black Sea
• Off subarctic Norway (correct)
• In the western Pacific off Asia
• In the Amazon River

They now appear regularly off the subarctic Norwegian coast.

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