Friday, 10 July 2009

Quotes from Orwell and North American Mammals

I found this quote at the bottom of a daily news update, and I like it:
The aim of a joke is not to degrade the human being but to remind him that he is already degraded. -- George Orwell
I was never made to read George Orwell at school, or collage, and so I came to appreciate what a good author he was without the negative memories of time in Engrish class. Which is good, this way I like him!

Here's some more science from the Conference, this one being talk number 54, titled "What's killing North America's mammals? A meta-analysis of cause specific mortality." It was authored by Christopher Collins and Roland Kays, out of New York State Museum.

As they write in their Abstract, everything eventually dies. What we'd like to know is across all mammals, what are the major drivers of mortality? We can quantify this by `Collering and follering` - putting on GPS or radio collars to track animals until they die, and investigating the cause of death.

Any given study can only look at so many animals at one time. GPS and radio collars are expensive, and so are putting them on critters. It's also very time intensive. So any given study only gets so much information, and that information is generally most applicable to a given species, or a group of species in a similar area. However, people can go in after studies are published and collect lots of peoples' different studies and bring them together. This is called a Meta-analysis. Meta-analyses frequently need lots of boring mathematical treatment, because people invariably collect their data in different ways, but well done meta-analyses can be very informative about large scale patterns that no one study would reveal.

Collins and Kays gathered in all the studies they could find with mortality data, and after working with the data, they found that surprisingly, 43.8% of across-species mortality was caused by humans. Most of this was hunting, though not all; Road-kill accounted for 7.9% of all mammals' mortality reported. Now, natural causes accounted for 40.9%, and unknown causes accounted for 15.3%, which is very large indeed. Natural mortality is probably much larger, because that 15.3% of unknown is likely a lot of disease related death, and predation. However, in those cases, the researchers got to the bodies late, or just couldn't figure out how the animal died - it's harder to figure out what disease killed an animal than you'd think!

Still, even if all of the unknown mortality was caused natural causes, that still leaves 43.8% in the hands of humans. Where other factors used to dominate, now humans apply the "Natural Selection" in North America. This has very profound implications for the direction that evolution will take in the long-haul, as species slowly adapt to human presence. Well, either that or they'll go extinct. One of the two.

I once took a course in Urban Ecology, which is the study of natural systems in human areas - farms, villages, dockyards, and big cities. What really stuck in terms of animal resilience was that species that thrived around humans either had a long history around human cities (usually Europe or Asian weeds and vermin), or animals that are so behaviourally complex, and so plastic and amenable to changing conditions, that humans really couldn't disrupt them. Racoons in the lower 48 are the perfect example of this.

With this in mind, and knowing what Collins and Kays said about human-cuased mortality, what Alaskan Mammals do I see with the best chance at persistence in 200 -400 years?
  • Arctic Fox
  • Red Fox
  • Coyote
  • Feral Domestic dogs
  • Racoon - invade and expand.
  • Ermine
  • White Tail Deer - invade and expand
  • Snowshoe Hare
This isn't a comprehensive list, but species that are behaviourally plastic, and stick out in my mind as things that can dodge human-induced mortality to a sufficient degree. I don't include moose because they're highly susceptible to diseases carried by White Tailed Deer, who are slowly invading northward.

There's some hope for other species, though. According to Collins and Kays, when humans designate an area as protected, it seems to work by-and-large. There's still human caused mortality, but it becomes considerably less. There just needs to be the political will to do it, and the public support for the designation.

Easier said than done.


William B Swift said...

I don't know about Alaska, but I used to live inside the Capitol Beltway in Maryland and saw beaver, muskrat, and mink inside the beltway. Beaver, especially, had increased substantially in number during the 1990s.

William B Swift said...

Also oppossums are at least as common as raccoons and grey foxes as common as red, but I doubt either will make it to Alaska.

TwoYaks said...

Possibly! My list is highly unscientific navel gazing, and isn't terribly complete. I wouldn't think Mink would be stable in Alaska's future, though, because they're exploited and they're not terribly behaviourally diverse. But I look forward to being wrong. Muskrat can definitely live in some marginal habitat, so I'd wholeheartedly agree with you on those. But again, it's just me speculating.

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