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18 September, 2010

Rattus Amongus

Olympia has rats, or some kind of giant gerbil. My family concocts, consumes, and disposes of various euphemisms for these creatures. And no doubt they drag the remains back to their lairs.

And attempted lairs, like in the bottom of our trash can, where they chewed a channel through the bottom and started setting up house. The weird thing is that they brought a Cheeto bag from somewhere else. Which just goes to show: them critters have networks of runs from lair to food to water to the secret escape tunnel to...everywhere. I live in great habitat--enriched with the offal flow of a dense human population--and the most I can reasonably expect without major interspecies warfare is to keep them out of the house. When we moved in I literally had to mortar in places under the house to keep them from coming in via the fireplace.

Granted, our rodents are as adorable as they get: big soulful eyes, healthy clean fur, that perky hop-run they do across the moonlit yard, not too big,...they're not so bad. The girls shudder at the suggestion of just killing them. Poison could kill our dog and rats eventually figure out how to avoid every trap anyway, which over the course of a few of their generations puts you right back where you started, except with fitter rats. So as an archaeologist, I'd have to classify any period of rat-free existence I could achieve as "ephemeral."

Anyway, the rat population is what it is because of humans. They are commensal species with us, and when you have a 2-week trash pickup cycle and a large percentage of composters in a fecund climate with yards providing cover and food, they flourish. We create habitat, they fill it. Whenever I've excavated in sites where small bones can survive, some species or another of genus Rattus has been found. Polynesians ended up transporting them everywhere they sailed, to the extent that one of the ways used to recontstruct their ancient migrations is through comaprison of rat DNA on all the far-flungislands of the Pacific. Really.

What remains unknown is how a rat could survive in tight quarters, with a crew of humans you would think would be intent on guarding their food stores and all the planting materials destined to start life on a new island. Archaeologists in Polynesia argue about this all the time. One camp says rats are just good stowaways. The other side scoffs, and says they were alloowed to survive, maybe even intentionally brought along, because they are edible. Imagine that you are setting out to colonize an island with unknown food resources, but you pretty much know there are not going to be any land animals worth eating. Would you maybe bring along something that subsists on scraps and seeds, multiplies rapidly, and tastes good roasted on a stick? From a survival perspective, it makes a lot of sense. After a while, when you've got your pig operation rolling, you pretend you never ate rat.

But if you're not in the mood for roasted rat (or tarts, or sorbet, or any of those other Monty Python dishes), how exactly does this coevolution benefit humans? I mean, they poop in our food caches, chew holes in everything, harbor diseases,... Well first of all, don't be so damn simple-minded and literal. Species that live and evolve together don't typically have altruistic thoughts about each other--they just have to co-occupy the same space without making the other extinct. The Plague, in the cold light of evolution, only made the European human population stronger. Thanks for the favor, rat.

To find the benefit on a more immediate scale, set back your clock a century or so, before trash collection and widespread urbanization. You tossed rubbish over the fence or into a pit, where rats were maong the creatures and microbes that broke it all down. Rats are incessant gnawers and poopers (dropping 200 turds a day, I've read), so they must be a significant factor in soil formation around human settlements. Through several varied attempts at composting here, I dealt with rodent incursions; they would sneak in and haul off whatever they liked best. They even ate or drove away worms I'd bought for composting, the rat bastards. Eventually, I just opted for a bin on the ground, nothing to prevent their tunneling in. Now I throw in the scraps, and they disappear down the bottom, eventually to become dirt somewhere.

All those tunnels aerate said soil, and provide habitat for all sorts of other critters. And of course when the starving times come calling on the large bipeds, the rats start looking like food again...

So if I were somehow able to eliminate rats from the neighborhood, more stuff would either pile up here or end up in landfills. The soil wouldn't be as good, and seeds would not be so widely distributed within it. I'd have less protein in the end times.

And plus, I cannot help but wonder if, facing extinction, the rats would up the level of their activity from annoyance to truly fighting back. What if the rats, sensing real trouble, started to systematically attack our food supply? Or gnaw through our infrastructure, contaminate us and maximize their disease vector behaviors? Yeah, where would we be then?

It remainds me of that Charles Darwin quote, attributed by some to Stephen J. Gould, but in fact made up by me, "Once the rats figure out how to do agriculture, we are toast."

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