Look and See – Charismatic Creatures of the Sea
Reading Time 3 minutes
A fellow fisherman recently told me a tale about his recent sightings of pods of dolphins or porpoises riding alongside the sportfishing boats of Southern California. However, he wasn’t sure how to identify these ocean companions or what distinguishes a porpoise from a dolphin. We’re all good at fish identification because we can examine them up close, but, marine mammal identification proves a more difficult task.
Dolphins and porpoise are both cetaceans, an order of animals that includes whales. Both dolphin and porpoise are toothed whales along with beluga, narwhals and sperm whales. Both animals use echolocation to sense the world around them, to hunt for prey and to communicate. Understanding their distribution and behavior provides an easy first step to differentiating these animals.
Porpoise prefer cooler waters than dolphins. While they’re both highly intelligent, dolphins exhibit more curiosity around humans than porpoises. Only two species of porpoise, Dall’s porpoise and Harbour porpoise, frequent Southern California waters, and of these, only the Dall’s porpoise are avid bowriders. Dall’s porpoise form small groups of up to 20 individuals and move into southern waters in autumn and winter.
Five species of dolphin inhabit these waters: Pacific White-Sided, Russo’s, Northern Right Whale, Common and Bottlenose. Common dolphins are the most plentiful dolphin in Southern California, form large groups of over 100 animals, and frequently engage in bowriding and aerial acrobatics. The Pacific white-sided dolphin is thought to be the second most abundant dolphin in our area, are commonly seen in groups of several hundred, and are also known for acrobatic and bowriding abilities. Bottlenose dolphins form smaller groups that also often ride the bow wave of vessels.
Given these characteristics, we can make a safe bet that when we see a large pod of bowriders, they are most likely dolphins, but we can’t rule out the Dall’s porpoise.
Confirmation requires a closer look at their physical characteristics. The difference starts at the head. Dolphins typically have a bulbous head and a clearly defined beak or long nose with a toothy “smile”. Porpoises usually have a rounder face will a dull beak.
Their size and fin gives us another clue. Dolphins are lean and long, averaging 6-12 feet and have curved dorsal fins. Porpoises are shorter and stouter, reaching just 7 feet, an have more triangular dorsal fins. If you get a really good look, examine the teeth. Dolphins’ teeth are cone-shaped, while porpoises’ teeth are spade-shaped.
These morphological differences reflect their different diets and feeding strategies, with dolphins using their longer beaks to catch faster-swimming fish which they swallow whole and porpoises using their blunter beaks to catch slower-moving prey like squid.
So the next time you are out fishing, take a closer look at the wild world around you. You just might be surprised by what you see.
Dall’s Porpoise
https://www.flickr.com/photos/
Common Dolphin
