Thread by @HomarusHannah

Tonight I attended the inaugural "Whale School" public lecture at #DalhousieU in Halifax, given by Canadian wildlife pathologist Dr. Pierre-Yves Daoust on the 2017 #RightWhale Mortality Crisis. Thread:

For context, 2017 was a year of unprecedented North Atlantic right whale mortality, with 12 confirmed deaths in Canada and an additional 5 in the USA. Most of these deaths were known or assumed to have been caused by human activity, namely entanglement and ship strikes.

For such a small population (about 450 animals), losing 17 individuals is a huge blow. Especially when there were no calves born in the 2017 calving season. In response, there has been a huge increase in conservation efforts in 2018.

North Atlantic right whales have been huge news items in the last year, and the 2017 mortality event is a major topic of discussion among both scientists and laypeople.

So, with that said, here is some of what I learned at #WhaleSchool:

1.0 It's very difficult to ascertain cause of death in large whales. Duh, right, but even large animal vets don't have the answers, because we have no baselines. We don't know what a healthy whale carcass looks like, so we don't know what an unhealthy carcass looks like.

1.1 Sometimes you can tell when a whale dies from entanglement, or starvation, or ship strike, but even those mortalities, which from an outside perspective seem like they should be easy to tell, aren't always clear.
(Photo c: Sea to Shore Alliance under NOAA, shared by @CBCNews)

1.2 That's partly due to an incomplete understanding of whale anatomy and pathology, and partly due to the logistics nightmare that is large whale necropsy. Beyond the difficult working conditions, specialized equipment, and trained manpower, you also need a fresh carcass.

1.3 After about a week, the organs and tissues are decomposed beyond a particularly useful point. And the carcass may have been subject to scavenging, or mechanical damage from wave action, or mechanical damage from the act of moving it to a workable location.

1.4 Not to mention the bombastic nature of whale carcasses, in which the insulating blubber retains the heat of decomposition in the body cavity, creating a pressure-cooker that can force the organs to spill out of the orifices.

Or, more dramatically, this:

2.0 Of the North Atlantic right whale mortalities in Canada for which cause of death is known, prior to 2010 there was a fairly even split between entanglement and ship strikes. Now, the ratio has skewed heavily towards entanglement, with over 80% of deaths after 2010.

2.1 Over 85% of right whales are estimated to have been entangled at least once, and many have survived - or haven't - multiple entanglement events.
(Photo c: @NOAAFish_GARFO, shared by the Marine Animal Response Society [MARS])

2.2 Fishing gear has, in the last decade or so, gotten heavier, the rope has gotten stronger, and there's been more of it in the water. All of which is bad news for a species of whale that swims slowly with its mouth open through heavily fished environments.

2.3 There may be a bias, in that entanglement leaves obvious scars on the body (and carcasses may be found with gear still attached) and is therefore likely easier to diagnose than blunt trauma or disease, but the fact remains that it causes a lot of unnecessary death.

3.0 On a related note, there's almost no understanding of infectious disease in right whales, because it's incredibly difficult to study the live animals, and incredibly difficult to get a usable sample from dead ones.

4.0 Even the anatomy and normal post-mortem changes are kind of a blurry subject. You can't dissect a healthy whale, and often can't necropsy a freshly-dead whale. So how do you know what's considered "normal" or not?

4.1 Whale biologists and wildlife pathologists can make comparisons to known anatomy of other cetaceans, or look for similar post-mortem presentation in terrestrial animals, but there's a dearth of experience that can make it difficult to understand what's happening in a carcass.

4.2 So never mind cause of death, apparently sometimes it's hard to even know what you're looking at, even as a subject expert. This lack of knowledge makes it even more important to perform necropsies at every opportunity - it's the only way to establish a baseline.

4.3 Here's a cool video from a right whale necropsy that took place in Gaspesie, QC in 2015, posted by @CWHCRCSF
Video: bit.ly/1QPZjVQ

Hopefully, the data and experience gained by scientists, veterinarians, and technicians during the 2017 right whale mortality crisis will give greater understanding to the post-mortem anatomy and help discernment of cause of death for right whales in the future.

Maybe that can be a small silver lining in such a tragic and unnecessary event. Who knows. At least with the drastic conservation efforts enacted in response to last year's crisis, there have been fewer right whale entanglements and deaths this year.

So far, there have been no confirmed deaths of North Atlantic right whales in Canadian waters. The third in American waters was confirmed this week.

https://twitter.com/NOAAFish_GARFO/status/1051945484032647168

Still, even three mortalities is a lot for a small population with no current calves, and who knows if any females will give birth this winter or not. I sincerely hope that what we're doing now will actually help, and won't be a case of too little, too late.
/thread

For convenience: unroll @threadreaderapp