Dead Orca L-112 is Beginning to Reveal the Story of Her Death

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Update 3/9/12: Both eardrums  [were dislodged and may have been] fractured.  Official report will be out soon.

L - 112 with her mom.

On Saturday, February 11, 2012, a 3-year-old Southern Resident orca  known as L-112 was found dead on the beach near the Columbia River mouth.  A marine mammal “CSI” team got to work immediately measuring the body, taking samples, and examining the whale’s corpse for signs of what could have caused the perplexing suite of deep damage yet that showed no obvious broken bones or bite marks. They were able to determine that L- 112 had been dead 2 -4 days.
Their best guess was that she was killed by an underwater explosion of some type, but determining the nature of the explosive force would take more information – the answer, they thought, might be found in the delicate structures of the head. They removed the head from the body and transported it to a laboratory for a CT scan.
The head was then frozen until the team could assemble with other experts, and nearly a month later in the uncommonly cold early March 6th morning in Friday Harbor they began the meticulous process of gradually removing skin, blubber, and muscle from the skull.
As they worked the scientists talked among themselves, and occasionally turned and talked to the web camera that was streaming the necropsy live, in real time.  I watched in fascination as they showed the different parts of the whale’s sonar system, from the sound producing tissues to the complex array of structures that allowed L 112 to navigate and find fish when the sound signals returned to her jaw, thorax, and ears.  They explained the significance of their findings, but cautioned the viewers that it was too early to speculate on the cause of death.
At times the scientists would quietly murmur their thoughts to each other, and give each other meaningful glances, probably cautious about speculating on their findings.  And at times the video and sound stubbornly refused to operate, and those of us who signed in took the opportunity to chat among ourselves – all of us appreciative of the efforts to make the event public and no one complained about the inevitable glitches.
Although I have attended other necropsies and helped with the process of cleaning cetacean skeletons, this was different for several reasons. First, unlike random found animals, L -112 was well known – The Center for Whale Research has been following her and watching her grow since shortly after her birth.  Second, it was possible to see most of what was going on – usually it is hard to see without getting in the way. Finally, the fact that they took the time and made the effort to give everyone – anyone in the world who was interested – a window into their work was inspiring.
They have archived the video and will make it available in a week or so.  For more information on the issues and to learn more about sound and whales, please check out BeamReach, Scott Viers did an incredible job in bringing the webcast live.
I can share what the necropsy revealed, but out of respect for the request not to speculate I will just share my notes.  Below that are some links and excerpts from a publication that may help you make sense of the results:

Difficult to cut through the still partially frozen tissues.
From previous necropsy of the body they found: hemorrhage right side entire, left partial.
Took samples to check muscle for hemorrhage etc.
Inside right mandible lower jaw 16 cm long tissue shows hemorrhage, air, only on right inside mandible to middle of the tongue.
Brown green air pockets. tracks extending distally into muscles.  Bruising laterally forward of the melon.
Right side of the foramen magnum.hyoid (supports tongue aids swallowing) underneath skull (hemorrhage?).
Removed the upper jaw caudal aspect of left mandible might have hemorrhage. In order to determine whether or not damage by loud noise was a factor in her death, the ears were meticulously dissected out and the delicate bones were checked for fractures and separation.  The tissues were examined for blood and hemorrhage.
Tongue is tactile and mobile, like an elephant’s trunk.  (This is normal).
Hemorrhage left side of head, trachea.
No obvious fractures of jaw!!! Thin bone doesn’t interfere with sound. KB talking. [The jaw bone is very thin and delicate so if the orca had been hit by something such as a boat it would have been damaged given the amount of damage to the surrounding tissues].
Jugal (cheek) bone below eye socket was checked, don’t know how it turned out.
Left bulla cavity removed something ( ? I think it was nematodes).
Possible hemorrhage in brain, fluid in space between dura and cal—- (?), 10 cc sero fluid from brain. Bleed in brain. Right side (?). Here we identify a new acoustic portal into the ear complex, the tympanoperiotic complex (TPC) and a plausible mechanism by which sound is transduced into the bony components.
Figure 1. Left lateral view of the Atlantic Bottlenose Dolphin (Tursiops truncatus) from CT reconstructions.
Skull = ivory, maxillary teeth = orange, mandibles = ivory, mandibular teeth = salmon, left mandibular fat body = green, left TPC = red.
Figure 2. Ventral view of the sound reception anatomy in Tursiops truncatus, reconstructed from CT scans.
Skin = cyan, skull = ivory, teeth and mandibles = salmon, mandibular teeth = salmon, mandibular fat bodies = green, TPC’s = red.
Figure 3. Lateral view of the left TPC and corresponding mandibular fat body (MFB) in Orcinus orca.
This volume has been reconstructed from CT scans of a Killer Whale (Orcinus orca) from the region around the TPC (0.3662 mm cubic voxels). As a consequence, the anterior boundary of the MFB has been artificially terminated at the anterior limit of the scanned volume. The entire head of this specimen was scanned and, as in all other odontocetes in this study, the MFB is continuous from the enlarged foramen of the mandible to its bifurcated attachment to the TPC (shown in this figure). The mandibular fat body is displayed as semi-transparent (blue), outlined in white dots, and overlies the TPC (yellow). The mallear ridge is indicated by the red dotted line. Other structures are as follows: P = periotic bone; TB = tympanic bulla; sp = sigmoid process; msmr = medial sulcus of the mallear ridge (bony funnel); mfb = mandibular fat body. The ventral branch of the MFB attaches to the tympanic bulla and the dorsal branch fits into the medial sulcus of the mallear ridge.
Figure 4. Posteroventral view of the anatomy around the right TPC in Orcinus orca, from hand dissection.
TB = tympanic bulla, pbs = peribullary sinus, cp = conical process of TPC, sp = sigmoid process of TPC, fvp = fibrous venous plexus, dfb = dorsal branch of the mandibular fat body. The white arrows point to fibers that tether the periotic bone to the periotic fossa of the basicranium (skull).
In fact, the acoustic environment within the head of an odontocete undoubtedly contains many pathways (multipaths) through various tissue types that may eventually reach the TPC. The key distinction here is that the pathways we have described are those that the simulations suggest have the potential to carry the largest fraction of acoustic energy to the TPC from that which is incident upon the dolphin’s head.

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