Invasion of the Purple sea urchin

Purple sea urchin (Image courtesy of Laura Francis, NOAA)

In 2013, millions of starfish were wiped out by a mysterious disease. Populations of the sunflower sea star were also devastated.

Why is this important? The sunflower sea star is the only real predator for the Purple sea urchin other than humans.

It is almost like one of those ‘z’ science fiction movies.
There’s a monster with no head, wiping out precious resources,
that seemingly lives forever, and eats its own kind.
It could have been a story about the Purple sea urchin.

Where found

The Purple sea urchin lives on the Pacific coastline and is found from Alaska to Cedros Island, Mexico. They inhabit rocky low intertidal and nearshore subtidal communities.

In an intertidal zone, the urchin will camouflage or decorate itself with algae, rocks, and shells. Scientists suggest that this behavior might help protect the urchin from ultraviolet rays, from drying out, or perhaps being eaten.

They like areas of strong wave action and churning aerated waters which may also provide some camouflage and protection. Surprisingly, they are found in depths of up to 525 feet.

A disguise or just dressing up?

In the intertidal zone, a purple sea urchin will decorate itself with shells, rocks and pieces of algae. Scientists think this behavior protects the urchin from drying out, getting eaten by gulls or being damaged by the sun’s ultraviolet rays. 

They live solitary lives, often in crevices, just waiting for
a bit of kelp to drift by.

Subtidal urchins live together in hordes that can take down a giant kelp forest (as recently reported in California), especially when predator populations get out of sync. Eventually, a kelp forest becomes totally barren.


Purple sea urchins are a favorite food of Sea otters. When the number of Sea otters declined, there was a remarkable jump in urchin population in California.

               How to tell if a Sea Otter has been preying on the Purple sea urchin? Its mouth and teeth are totally purple, like a lipstick gone bad.  

Sea stars also prey on Purple sea urchins. As the sea star creeps near the urchin, the urchin moves its spines and lets the sea star get really close.

The Purple sea urchin patiently waits as the star closes in. Then launches a surprise attack with pincers chomping on the sea star’s tube feet. Most sea stars back off about this time.

The Sunflower sea star does not. When one of these stars get close, the urchin seems to panic, waving its spines and pincers, and attempting a retreat.

Physical aspects

Urchins don’t move very fast. It’s feet are tiny.
If it is not fast enough, the Sunflower sea star will
swallow the urchin whole, spines and all.

Small tubular suction devices extending from the spines help the urchin move. The tube feet are muscles that protrude from the spines.

The feet can attach to rocks or coral and move the urchin across the sea floor. The tubular feet help the urchin breathe and are used more often than gills for gas exchange.  

The mouth (located on the underside) has five toothlike plates. The teeth and spines are used to dig holes or depressions for the urchin to hid in. They can even drill through steel pilings by flaking away rust.


The spines help move food around to the mouth and support the feet. The spines will pierce human skin and cause minor problems.

If this happens to you, douse with vinegar. Vinegar will quickly dissolve the spine. Do not pull it out…it never entirely comes out…

The round body holds the spines and can measure up to four inches in diameter. Generally, adults are bright purple.

Juveniles may be pale green with some purple tinges. Eggs, or roe, are orange and are considered a delicacy.

Look ma – No Head?

The Purple sea urchin does not have a head structure.
But, it seems to have a head for business.

Sea urchins are big business and a high-valued fishery in California. In 2000, 20 million pounds were harvested and sold to Japanese markets. Sea urchin har­vest­ing has be­come one of the high­est val­ued fish­eries in Cal­i­for­nia, bring­ing $80 mil­lion in ex­port value per year.

The idea of ‘urchin ranching’ is popping up projects in Japan, Canada and California. Divers could transfer wild and starving urchins to on-land tanks where they could be fattened up for sale. The numbers available in the wild are astronomical.

The possibilities are endless almost like the life span of these critters. Most of the urchins have long lives, like 70 or more years. The potential for creating a sustainable aquaculture fishery along the Pacific coast is immense.

This story turns totally weird when comparing human and urchin DNA. Using the strictest measure, the purple sea urchin and humans share 7,700 genes.

That explains the purple spikey hair perfectly don’t you think?  A story for a different day.

More urchin anyone?

–Oregon State University (
–US News (
–Fun Facts, Monterey Bay Aquarium (
–How Stuff Works, Sea Urchins are the edible Purple Pincushions of the Ocean (
–Wikipedia, Strongylocentrotus purpuratus  (
–Animal Diversity (

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If the call of the loon “were of human origin,” author John McPhee once wrote, “it would be the laugh of the deeply insane.”

Loons in our Lakes by J. McPhee
Common Loon (Unsplash Royalty free by Kevin Crosby)

Common Loons have deeply insane diving and underwater skills and some wildly crazy vocalizations.

Loons capture fish by swimming through through water. This torpedo-like attack is fueled by short, strong legs and webbed feet that provide excellent underwater speed and maneuverability.

Olympic swimmers would envy the Loons ability to make abrupt 180-degree flip turns in seconds. They would also be amazed at how the birds are able to dive without a splash and reach depths of over 200 feet. Even newly hatched chicks are able to make shallow dives to escape predators.  

How do Loons swim like that?

To start with, Loons have web feet that are placed far back on their bodies. Four hundred different species of birds have webbed feet, as well as, otters, frogs, and salamanders. Web feet spread out to push the water backwards. The toes fold together minimizing water resistance on the forward stroke.

Webbed-feet are hard to walk with. In the case of the Loon feet are placed near the back of the body making it even more difficult, some say comical, for the bird to walk on land. To experience this problem, slide on a pair of large swim fins and try to walk across the lawn. Now you know why loons spend so much time in the water and only come near shore for nesting.

Loons are less buoyant than most flying birds. Loons have heavy, solid bones that serve as underwater ballast and help them dive deep. The bones of most other flying birds are hollow and filled with air.

These birds expel air out of their lungs and plumage when diving. This reduces water resistance and buoyancy and creates a very streamlined body shape. At the same time, their heart slows down to conserve oxygen and they are able to maintain the dive for several minutes.

What are they eating?

These extraordinary swimming skills are needed to capture fish, their diet mainstay. Some fish have erratic swim patterns and are easily caught by the Loon (this includes Bluegill and Yellow Perch). Fish that swim straight ahead (like salmon and trout) are more difficult.

Fish are caught underwater and often swallowed head first. Sometimes larger fish may be brought to the surface. Other prey may include crustaceans, crayfish, snails, leeches, lobsters, insect larvae, mollusks, frogs, worms, and occasionally aquatic plants.

Adult loons may eat up to two pounds of fish per day, and a loon family with two chicks may consume over 900 pounds of fish over the course of a breeding season.

How well do they fly?

Loons can fly ~70 mph and routinely migrate. They are like a jumbo-jet—they need a lot of space to take off and land. At times, a Loon can become stranded and unable to take-off if the pond is too small. They are not able to take-off and fly from land.

Loons are fast flyers and have a wide territory in the coastal U.S., and northern U.S. and southern Canada. Many migrate and over winter in coastal areas. Some migrate south into Baja California. In all cases, they will only stay in waters that are crystal clean and well populated with fish.  

Loon call

Loons are often identified by their eerie, and unusual calls. They use a tremolo call (that sounds like crazy laughing) when alarmed or to announce their presence and soft hoots to keep in contact with their young and each other. Each male loon also has a unique yodel used to identify territory.

To hear these calls see the Loon Preservation Committee website ( There is a good chance that you will have heard these calls in the movies (such as “On Golden Pond,” “Finding Dory,” and several others.

–Loon Preservation Committee (
–Oregon Dept. of Fish and Wildlife, Loons and Grebes (ODFW
–The Cornell Lab, Cornell University, (
–Audubon Society (
–Wikipedia, Common Loons (
–”Loons in our Lake” (