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Saturday, February 15, 2014

Formidable

Last night I was helping Eric wrap up some field work in the rocky intertidal zone when a Western Gull (Larus occidentalis) landed nearby.  It started walking around on the rocks and definitely looked as if it had a purpose — it was focused on finding something to eat.

A few minutes later we were both surprised to see the gull emerging from a shallow plunge-dive with an octopus!

The Western Gull flew to a ledge and dropped the octopus at its feet:


The gull then proceeded to manipulate the octopus with its bill, stabbing it, and picking it up and dropping it several times before finally swallowing it whole after about a minute and a half.

These pictures aren't greatI didn't have the right lens, and it was getting dark.  But it's an interesting behavior and I don't think you'll have any trouble appreciating this predator-prey interaction.



Pretty soon after swallowing the octopus the gull started searching for food again.  It dropped into a nearby channel and was fairly close to me so I decided to take a picture of the searching behavior as the gull swam along and scanned the rocks and crevices.



I was tracking the gull while looking through my camera and I couldn't believe it when it caught another octopus!  This was ~5 minutes after swallowing the first octopus, and ~1 minute after entering the water!



Once again, the gull flew to a nearby ledge and dropped the octopus a few times. 



And then it flew off to a more distant location.


I must admit, this was both fascinating and difficult for me to watch.  I'm so fond of octopus that it was a little hard for me to see them appearing so vulnerable.  But I also have great respect for predators and their hunting skills and their importance in food webs.  

I've heard a few other reports of gulls eating octopus, but it was interesting to see that octopus were not mentioned as food items for Western Gulls in the Birds of North America account.  The authors list many fish and other marine invertebrates (including squid), but octopus are not among the documented prey in that account.  

It made me wonder whether feeding on octopus happens occasionally among many individual gulls, or whether just a few individual gulls specialize and learn to find octopus?  Although it's a very small sample size, this particular gull seemed especially good at it!

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