Friend Feature: Harbor porpoise

Harbor Porpoise (Phocoena phocoena)

By Sarah Teman

A very rare swim-by of a harbor porpoise by diver, Florian Graner in the deep. Photo by Florian Graner, Salish Sea In Focus

Did someone just sneeze?

Hey, did you hear that? If you’re out by the water and you hear what sounds like a short, loud sneeze, scan the water and see if you can find a harbor porpoise. Called “puffing-pigs” for their distinctive “puff” of breath at the surface, harbor porpoises might be heard before they are seen – they are a cryptic and shy species that tend to surface for short intervals before diving.

Bigg’s killer whale (T123C) flips a harbor porpoise into the air. Photo by Melissa Pinnow, Flickr Creative Commons

Their short, triangular dorsal fin hardly raises out of the water when they surface, and, unlike dolphins or even more closely related Dall’s porpoises, harbor porpoises are not known for high-activity surface behaviors – that is, unless a male is putting on his best moves for a female, or a male or female is caught in a high-speed chase by their main predator, a Bigg’s (formerly called “transient”) killer whale!

Countershading

The harbor porpoise blends in perfectly with its environment. It is dark grey on its dorsal surface so that if a predator is above the porpoise and is looking down, the porpoise will blend in with the depths. Similarly, the porpoise is light grey on its ventral surface so that if a predator is below the porpoise and is looking up, it will blend in with the light shining through the water. This effect is called countershading.

This baby harbor porpoise was injured in the wild and discovered by the Marine Mammal Rescue Centre of Vancouver Aquarium in 2011. Can you see the light colored belly and dark back? How could that help this porpoise in the wild?. Photo by Esther Lee, Flickr 2.0

Think like a porpoise

Imagine you live in the cool, dark, nutrient-rich waters of the Salish Sea, where prey could be hiding – or predators lurking – from any point in three-dimensional space. How do you navigate this complex ecosystem, like finding food and shelter, and avoiding mammal-eating killer whales? What would be your primary “sense” of interacting with the world? For a porpoise, it’s echolocation.

HELLO..HEllo..hello..hello

Echolocation allows porpoises and other toothed whales to “see” underwater by producing a series of intense, ultrasonic clicks that travel underwater and bounce back when they hit an object. The clicks are produced by the porpoise’s phonic lips (not the kind on our mouths, but just inside of their blow holes!). Clicks are directed and beamed at an object via the melon, or the fatty tissue in the forehead. When the sound waves are reflected from an object and return, they are absorbed by the porpoise’s lower jaw and conducted to the inner ear.

Echolocation is crucial for harbor porpoises to not only stay vigilant against predators, but to find prey. Harbor porpoises in the Salish Sea have been documented eating a variety of organisms, including (but not limited to) Pacific herring, Pacific sand lance, Pacific hake, Walleye pollock, other fishes, cephalopods, and crustaceans. While harbor porpoises tend to forage in areas less than 100 meters deep and with high tidal mixing (swirly waters), they can hold their breath for 5 minutes, 21 seconds and reach greater depths – one individual was recorded diving up to 740 meters! How deep can you hold your breath and dive?

Sound might be important for social interactions, too. While harbor porpoises don’t produce whistles for communication like their more talkative dolphin cousins, their high-repetition clicks might also be used to chat with family and friends, usually those in their social groups of between 2-8 individuals.

What’s the porpoise?

How canyou be sure that the fin you glimpsed for 2 seconds above the water belongs to a porpoise? We’ve got your back (so you can identify theirs). Porpoises have a few key differences from dolphins:

Hybridization

Harbor porpoise have even been found to hybridize with another species of porpoise in the Salish Sea – the Dall’s porpoise (Phocoenoides dalli). The Dall’s porpoise differs from the harbor porpoise in that it is larger and more robust, starkly black-and-white (compared to the harbor porpoise’s shades of grey), and generally displays more surface activity behaviors – Dall’s porpoises are known to ride the bow wake ahead of fast boats and zip through the water, creating a “rooster tail” effect in the waves.

Interspecies hybrids can survive and make babies. Interestingly, all known Dall’s-harbor hybrids have resulted from a female Dall’s and a male harbor porpoise. Scientists think this is because of the species’ different breeding strategies: male harbor porpoises attempt to mate with as many females as possible during the breeding season, whereas male Dall’s porpoises will “guard” one reproductive-age female during the breeding season.

Harbor porpoise in the Salish Sea

An adult harbor porpoise investigates diver, Florian Graner in the central Salish Sea. This occurrence is very rare. To keep porpoises safe, they should not be approached by people within 100 yards or meters. Photo by Florian Graner

Harbor porpoises prefer nearshore waters within 200 meters of land and thus live close to human development and its associated threats. Harbor porpoises decreased in abundance in the Salish Sea from the 1970-1990s, and while the reasons behind this decrease are not entirely understood, scientists believe it was likely due to a combination of human mistakes.

In the past, accidental catch and entanglement from fisheries was likely a large contributing factor to harbor porpoise mortality. To reduce this, acoustic alarms, or pingers, were attached to nets to deter harbor porpoises; current research is needed to measure harbor porpoise bycatch and entanglement rates today.

Other past and current challenges for harbor porpoise include habitat changes, like development of quiet bays into busy ports, pollution, bioaccumulating contaminants, decrease in prey species, and increases in vessel presence, noise, and traffic. You might notice that these are similar threats to those facing the harbor porpoise’s larger cousin, the fish-eating southern resident killer whale. This goes to show that our actions tend not to impact just a single species, but can have ecosystem-wide effects. The same goes for our positive actions, too – what we do to help one part of the Salish Sea can have a positive effect on the entire ecosystem! There is hope!

Luckily, since the 2000s, harbor porpoise numbers in the Salish Sea have been on the rise. Now, they are one of the most common species of cetacean to see in the Salish Sea!

Here is what you might see from shore or a boat after hearing that distinctive “puffing pig” breath. You have a great chance of seeing them as their numbers have increased and they are now one of the most common cetaceans in the Salish Sea! Photo by NOAA

The story of the harbor porpoise is one of continued and cautious optimism and hope. This small, shy porpoise is resilient and capable of rebounding, with your help! As Junior SeaDoctors, your mission to help us all heal the Salish Sea is critical to help protect species like the harbor porpoise. Helping protect marine and estuarine habitat, reducing pollution, and promoting policies and legislation geared towards healing the Salish Sea are just some ways that you can help have a direct impact on the harbor porpoise and all other species that call the Salish Sea home.

Hungry for more porpoise-full knowledge and ways you can help? Visit The Marine Detective’s Porpoise-full Blog.