Monday, June 30, 2014

Cornucopia

Banana Slugs (Ariolimax columbianus)

One, two, three, four, five, six.  "Cornucopia" is the collective noun for slugs.  I had to look this word up since I had never seen slugs in a group.  In fact, during all the treks I have taken in the woods, over all the years, I have never seen anything quite like this.

One week ago, I was in the newly opened Kukutali Preserve which comprises Kiket and Flagstaff Islands in Skagit Bay.  Near the west end of the South Trail is a heap of fallen trees, rotten wood and bark.  It appears to be windfall that was cut up and piled next to the trail.  The stuff was swarming with Banana Slugs (Ariolimax columbianus).  Most seemed to be resting with their antennae pulled in under their mantles.

Banana Slugs (Ariolimax columbianus)

Banana Slugs (Ariolimax columbianus)

Banana Slugs are familiar forest denizens in the Pacific Northwest.  What we usually see are solitary individuals here and there along a trail.  There might be one or two of these reclusive creatures seen on a hike.  If it has rained overnight, we could see several the next morning.  They will be spaced out along the trail, going about their sluggy business recycling 11% of the forest biomass every year.

Banana Slugs (Ariolimax columbianus)

Searching the net, I was not able to find a specific reason for such an aggregation.  I can only venture a guess.  I think the gathering might have had something to do with slug reproduction.

Slugs are hermaphroditic which means that each individual is both male and female.  Every slug is equipped to produce both eggs and sperm.  Mating is usually a mutual affair, each partner inseminating the other.  There didn't appear to be any of that going on during my visit.  What I may have stumbled upon was the aftermath following a night of courtship.

Slugs find mating partners with pheromones broadcast in their slime trails.  These are chemical signals that call in the troops, so to speak.  That may explain why there were so many grouped together.  It stands to reason that such an aggregation of individuals would increase reproductive success.

Finally, there's that apophallation thing.  After mating, the pair is sometimes unable to separate.  They resort to chewing off their own or their partner's penis to make separation possible.  Too much information, I know, but never fear.  The altered Banana Slug will continue a happy life as female.  And I am sure we'd all need to take a rest after that experience.

Banana Slug (Ariolimax columbianus)
Banana Slug (Ariolimax columbianus)

Banana Slug (Ariolimax columbianus)
Banana Slugs (Ariolimax columbianus)

The next question I had was why they were congregated around all this rotted wood.  I found one reference that indicated they like to lay their eggs in rotted wood or bark.  This will insure the eggs will stay constantly moist.

When I returned to the Kukutali site last Friday, only about half of the group remained.  On today's visit, all of this cornucopia of slugs was gone.  I was again seeing only single individuals here and there along the trails.  I wonder if I will ever see such a spectacle again.

As usual, I would enjoy hearing from anyone who has information about why these slugs had gathered together like this.

If you go down to the woods today
You're sure of a big surprise.
If you go down to the woods today
You'd better go in disguise!

For ev'ry slug that ever there was
Will gather there for certain, because
Today's the day
Banana Slugs have their picnic.

If you go down to the woods today,
You'd better not go alone!
It's lovely down in the woods today,
But safer to stay at home!

For ev'ry slug that ever there was
Will gather there for certain, because
Today's the day
Banana Slugs have their picnic.

With appreciation to all Teddy Bears and Jimmy Kennedy

Saturday, June 21, 2014

Black Oystercatcher at Kukutali Preserve

Black Oystercatcher

Just across Skagit Bay from my home is Kiket Island and the smaller Flagstaff Island attached to it by a tombolo.  The islands now comprise the Kukutali Preserve.  It is owned and operated jointly by the Swinomish Tribal Community and Washington State Parks.  Until this week, access to the Preserve was limited to small guided groups by reservation only.  It is now open to the public and I made my first unescorted visit last Tuesday.  You can read about my visit and the history of this newly opened nature preserve at Fidalgo Island Crossings.

With a good low tide, I returned this morning with a specific objective.  I wanted to see if the Black Oystercatchers (haematopus bachmani) I first met three years ago are still living at Flagstaff.  I spotted a pair calling and flying low over the bay towards Skagit Island on Tuesday.

Sure enough, today I was rewarded by another encounter with one of my old friends.  Oystercatchers are non-migratory, form long-term pair bonds, and are known to live 15 years or more.

Kukutali Preserve at Deception Pass

This is the Oystercatchers' habitat.  Isolated rocky islets in northern Puget Sound are some of the few places they are found inland from the Pacific coast.  Flagstaff on the right is a flat piece of volcanic stone surrounded by a rocky beach.  The beach provides mussels, limpets and clams which make up their diet.  I photographed their clam opening technique for a previous post.  They nest at the edge of the island above the tide line in a simple scrape on the ground.

Looking west, the Deception Pass Bridge can be seen from here.  Flagstaff Island itself is a fragile lowland meadow habitat with thin soil.  It is protected and off-limits to visitors.  Check the information posted at the Preserve entrance to find the red zones where visitors are not allowed.  Note that only Swinomish tribal members and the Oystercatchers are permitted to harvest shellfish on these beaches.

Black Oystercatcher

I first spotted him while hiking along the south beach.  He was casually walking up the beach towards Flagstaff Island.  With my 18-200 mm lens, I was able to keep my distance.

Black Oystercatcher

Suddenly, he took wing and flew towards me.  So much for keeping my distance.  I have remarked before how laid back and affable these birds seem to be.  They don't act like they care about the presence of people in their territory.  Living in isolated places, they may have never developed a strong fear of humans.

Black Oystercatcher

He sauntered up to within 10 feet of me and decided to take a rest.  This was not my first close encounter, but I was still astonished.  Although they don't appear disturbed, people should never try to approach them.  Remain still and quiet and let the birds come to you if they feel comfortable.  Always stay well away from their nesting sites.

Black Oystercatcher

Apparently, this was not quite the right spot.  He got up and continued his trek towards Flagstaff coming even closer to me.  While they are strong fliers, these are shorebirds that never swim.  Their feet have long, stout toes specifically designed for walking on rocks and barnacles.

Black Oystercatcher

He continued up to the edge of Flagstaff Island.  Notice how well camouflaged he is there.  Now this looks like a good spot to rest for a while.  The stones have been warmed by the morning sun and he can keep an eye on that silly human taking his picture.