Tuesday, May 3, 2011

The Invaders (Part Three of Three)

The third entry in our environmental "Axis of Evil" goes by many names.  The Brown Rat, the Wharf Rat, the Common Rat, the Norway Rat (even though his species probably originated in Asia), the Hanover Rat, and probably more.  Officially, he is  rattus norvegicus and with the possible exception of human beings, he and his kin are the most widely distributed and successful mammals on the planet.  

Rrattus norvegicus likes to forage close to his burrows and will use the same paths so frequently that visible paths develop on the ground.

There happens to be one rattus norvegicus (at least one) living under the fence in my front yard.  If you can get past the instinctive animosity some people feel toward his kind, he is actually a pretty handsome fellow.  A close relative of hamsters, gerbils, true mice and other rats, he belongs to the murroid superfamily of rodents, and collectively they occupy a wide range of habitats and have prospered on every continent except Antarctica. 

Lab rats and mice have been shown to be capable of some degree of empathy.
The Norway Rat (no one seems to be quite sure where he got that name) is the ultimate example of the creature who has learned to prosper in the world that man has built.  They have been our nemesis for as long as we've been settled, crop growing animals (it was undoubtedly the threat that rats and mice posed to grain stores that led to the unlikely alliance between humans and cats in ancient Egypt -- an alliance which is not without its own environmental costs in today's world).  He has been blamed for disease and plague and is almost the symbol of cringing, dirty lowlifes.  ("You dirty rat!")  And though living in close proximity to rats -- especially rats nurtured on the refuse of human civilization -- can be unhealthy, I don't think rattus norvegicus really deserves his unsavory reputation.  When you come right down to it, he has a lot in common with us.

Rats build elaborate systems of burrows which they like to line with shredded paper, leaves or other fibrous materials.  Depending on their population density they can be polygamous (one male rat monopolizing many females) or polyandrous (each female when she comes into heat mates with as many males as can manage).  They are highly adaptable, changing their behavior and social structure to meet changing situations.  Rats, and their cousins mice, had been shown to possess something that looks like empathy, an ability to recognize and respond to the suffering of others, especially individuals they are closely acquainted with.

Rrattus norvegicus is highly adaptable and social.
Rats are mostly nocturnal, although like the rest of their behavior they can adapt to being active in the daytime, if population densities are high, if food in plentiful and if there is little danger of predation.  They usually don't wander more than a few hundred yards from their burrows, and they favor the same paths so much that they form visible trails on the ground.  

Wherever humans have gone, rats have followed.
If you look up the Common rat on the Internet -- no matter which of his many names you use -- you will find that way more than half of the hits you find involve ways to eliminate and control rattus norvegicus. He has followed us everywhere around the world, and we have used him as a scapegoat, a lab animal, a metaphor, and even a pet.  We have crated environments in which rats thrive, but in which they also become carriers of disease.  We often seem to blame rattus norvegicus for the squalor he sometimes lives in -- which is, after all, only our refuse.  We built the dumps, the wharfs and the slums.  He only learned to live there.

The rat in my front yard, though, is living in clean dirt and eating the seed that falls from my bird feeders.  For the moment, I'm enjoying having him around.

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