First, did you know that goshawks (Accipiter gentilis; the Northern Goshawk) can fly through extremely small spaces? This bird wasn’t trained to do it; they fly through dense woods and have to negotiate quickly on the wing.
(For an earlier post on goshawks hunting, go here.)
And this fascinating fact, which will make you a hit at cocktail parties, came from the University of London’s John R. Hutchinson, a big name in vertebrate anatomy and biomechanics:
You’ll want to see the proof, of course (that semicircular, whitish-blue bulge in the hole is the back of the eye):
[EDIT FROM MATTHEW COBB: I sent John’s tweet to Jerry and I was so amazed I chatted about it with various colleagues this morning. Amazement all round. Then someone asked: ‘how do they hear?’ This led to a lot of googling and thinking – ‘hey, what about the ear drum?’ And the answer is (it appears) – this is a picture of a dead owl that has had its ear drum removed/sectioned so you can see into its eye socket. Which is still pretty cool, just not as cool as we all thought. My excuse? I know about maggots and that’s about it. John didn’t realise that we would all misinterpret the picture (which he didn’t take). IF ANYONE KNOWS ANY BETTER PLEASE WRITE IN THE COMMENTS BELOW!]
Hutchinson has pinned a gazillion great animal/anatomy picks at his Pinterest site, Mucho Morphology. Here are two as lagniappe, but go over and see for yourself:
A leucistic (not albino) echidna, from All Albino Animals (some of them aren’t true albinos, but show leucism):
Originally pinned by Judy Shelton onto Albino Anomilies
The eye of a giant Humboldt squid:
EDIT from Matthew Cobb:
Given that the d*g has no bone to the back of its eyesocket (as you can see in this skull), I asked John Hutchinson on Twitter whether you could do the same trick with a d*g as he did with an owl. He replied as follows:
h/t: SGM, Matthew Cobb
That is extraordinary!! You can see the optic nerve and everything. At least I assume that’s what that is. That really is bizarre.
The squid eye reminds me of when this happened: http://www.dailymail.co.uk/news/article-2216580/Florida-eyeball-Washed-eye-belonged-swordfish-giant-squid-experts-say.html
It must be very thin skin covering the eyeball.
It is a very common feature in mammals to lack the bony bridge that we have between the lateral margin of the eye socket and the temporal fossa (the depressed area on the side of the head where large muscles attach to the lower jaw). Primates and hooved mammals are examples of mammals that still retain the ‘primitive’ feature of the bony bridge. My guesses for why it is often missing is that it (a) might provide some more surface area for muscle attachment, and/or (b)it makes the head a little easier to squeeze into tight spaces.
I can understand that the eye ball doesn’t need much of support, it could be inflated by inner pressure, and seeing the ball barely held in position isn’t too much of a surprise. (But COOL!) Among reasons could be less mass, which would be a premium in birds and especially in birds with a flexible neck.
But you would think evolution would put a fitness weight (so to speak) on protecting the eyes. Is the skull open around the eyes because dogs have to accommodate large skull stresses as they evolved to be bone crushing specialists earlier? I checked its evolutionary parallel, the hyena, and its skull has the same features. [ https://commons.wikimedia.org/wiki/File:StripedHyenaSkull.jpg ]
But of course, some null hypothesis samples gives the same result, say tiger. [ http://www.boneclones.com/BC-008.htm ]
Still, I would suspect that a tiger has to take large stresses around the jaw parts of the skull in the way it hunts. Domestic cats seems to have more or less fused the bones around the orbit. [ http://minotaur-queen-stock.deviantart.com/art/Domestic-Cat-Skull-Stock-177553201 ]
So, a dud hypothesis or fud for biology thoughts? I believe I have seen people work on stresses in bones, does anyone know what were the evolutionary conclusions? I can’t find any on that.
And if the previous comment makes it through moderation:
Yes, I am procrastinating today.
And I was struck by the ease of finding sites that sell actual bones from all sorts of animals. That doesn’t feel right.
Interesting ideas. The loss of the bony bridge around the eye orbit is very common in mammals. Carnivores, rodents, bats, and lots of other very successful groups have lost that bony bridge. For whatever reason there is for losing the bridge, there must be compensation of the stresses by bony reinforcement nearby, perhaps inside the cranium.
Thanks for the info!
Meanwhile, at Cornell, the first hawklet fledged on June 4, and seems to be getting the hang of flying. It is currently back at the nest. The third hawklet has yet to fledge. #2 had an awkward, and perhaps accidental, fledge on June 5, catching a claw and hanging upside down for about a minute before getting free. It has not yet been able to get back to the nest.
Cool! A parent is feeding one of the chicks now by standing on the prey, ripping out a piece, then giving it to the chick. I always imagine a mom T. rex doing the same for her young ‘uns.
I’d have expected the owl’s eye to be better protected. I can’t imagine any advantage to such easy access. Light from the back side of the eye is going to degrade vision, and there’s plenty of opportunity for dirt and debris to collect back there which can’t be at all good.
b&
Never clean your owl’s ears with a q-tip 😉
I loved the goshawk video and I think maybe I’m suffering from leucism (but I get lots of vitamin D easy) 🙂
Kink was fascinated. We watched Ellie at full screen 3 times!
Although the translucent tympanum prevents seeing clearly what’s on the other side, you can look straight through a lizard’s head through it’s ears. For example, you can detect your finger moving back and forth beside the left ear by looking into the right ear.
I’m sure many of you are aware of this by now, but that is NOT a picture of the ear of a dead owl! The species is a Northern Saw-whet Owl, and the hand belongs to Kelly Williams, who just received her PhD at Ohio University. She and I are partners in a saw-whet banding project in southern Ohio, since 2003. The picture was taken by Jim McCormac, one of Ohio’s premier field naturalists and bloggers. Kelly routinely shows the ear of saw-whets to our visitors before we release the bird.