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Thursday, April 2, 2015

Do they sting when they go down?

The numbers of Velella washing ashore have continued to increase.  The large concentrations appear to be attracting scavengers.  In the early evening I watched Western Gulls feeding on them!

It was hard to see exactly what was going on.  Sometimes it looked as if the gulls were swallowing them whole.  Other times it seemed as though the gulls were nibbling at the tentacles:

Frequently, the gulls would pick up the Velella by their sails and walk with them back to higher ground:

How common is this?  How often do gulls eat Velella?  At first I had trouble finding any references to gulls eating Velella.  When you read about predators of Velella, you'll see mention of pelagic nudibranchs (Fiona or Glaucus), pelagic snails (Janthina), and Ocean Sunfish (Mola mola).

When you read about gulls eating pelagic invertebrate prey, you'll see mention of krill, squid, pelagic gooseneck barnacles, and pelagic red crabs.

And then finally a search on the Internet brought up one line in a book The Natural History of Skokholm Island that mentioned gulls will eat Velella.  I had to go all the way to Wales for confirmation that this had been seen before!

It raises all sorts of questions, doesn't it?  Do Velella's tentacles sting the gulls?  If the gulls swallow Velella whole, do they cough up the sails in their pellets?  Do they only eat freshly stranded Velella?  Do they prefer larger Velella?  How nutritious are Velella?  And you thought you'd be bored by another Velella post...  ;)  

A few more of my favorite pictures from tonight: 

There are so many Velella washing up right now that they're starting to fill tidepools:


A shipwrecked Velella high on the rocks:

How many sizes do you see in the center of the picture?

There's the larger float below, the medium-sized dark blue Velella just left of center on the larger float, and two very small Velella on the right side of the larger float.


leafcutter said...

any fiona pinnata on these sailors?

Jackie Sones said...

:) I've been looking for Fiona among these Velella...none so far. Although we have seen Fiona (the brown form) among Lepas (pelagic gooseneck barnacles) on driftwood when the Velella first started washing ashore.

When we found the blue form of Fiona on Velella last year, I started wondering about which factors allowed that association to happen. That is, we often see Velella, but don't often see the blue form of Fiona. Do they require a certain size of Velella (last year's Velella were very large)? Do they require a high density of large Velella? Do they require a certain water temperature (i.e., warmer)? Lots of questions. But I'll admit, that blue form of Fiona is so beautiful that I won't stop looking for them and hoping to see them again.


leafcutter said...

yeah those blue fiona are something else. thanks for the thoughts. keep up the good work! great blog, love the daily posts!