Last week during my volunteer shift at Marine Mammal Center I was checking on all the animals before preparing for the first feed and I came upon a sleeping Northern Elephant Seal named Annabellini. I lingered awhile waiting for him to breathe so I knew he was okay, but I guess I disturbed him somehow. He stirred a little, moved a flipper and then opened his eyes. And that's when it happened: Two streams of water, one from each eye, shot out about 18 inches each -as if they came from a fat, hairy, double-barrelled squirt gun! A new volunteer was with me and said "Wow! What just happened?". In my (almost) year of experience I had never seen anything like that before, so I just said "Well, I guess he's well hydrated!".
After we finished feeding the animals on site I asked some fellow volunteers about what I had seen and in their (up to 20 years') experience none of them had ever seen an elephant seal shoot water from it's eyes. As we talked, Dr Lorraine passed by and she had no explanation either. At this point I started to feel a little silly and began doubting what I saw. But, Dr Francis Gulland came by later, so I explained what I saw one more time and asked if she had any idea what had happened. Of course she did. Seals lack nasolachrymal ducts! -I passively knew this, but not how it related to what I saw. Before I explain it any further, let me back up:
Anyone who has observed seals knows that when they are dry they often have a ring of wetness around their eyes. It is part of what makes them so cute -it often looks like they were crying. At Marine Mammal Center we recognize this as a sign of good hydration, but why do the tears spill out of the eyes in seals?
Most land mammals produce tears constantly, but the excess tears drain through a duct in the corner of the eye called the nasolacrymal duct which drains into the nose. This is why a person tends to get a runny nose when they cry! But, seals lack that duct so their tears just seep from their eyes constantly. (This is probably because they spend most of their time in the ocean where the draining of tears is not important.)
Here's a diagram of tear production in humans which is the same for most land mammals:
So, back to the dramatic event of an elephant seal shooting water from its eyes: Dr Gulland said that this was a sign that the seal was severely DEhydrated! She said that in his sleep, due to a decrease in tears, his eyelids likely sealed shut. The slow production of tears allowed the fluid to build up behind the eyelids. When I disturbed him and he opened his eyes the pressure was released causing the fluid to shoot out.
How cool is that?
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