Exotic rat at Point Reyes

This week I shot a rat. With my camera, that is. To be precise, I photographed a roof rat foraging under a flowerpot for stray birdseed. It was a lucky shot, for an instant after I snapped the picture, the rat was gone.

For 30 years, I have been aware of roof rats on this hill, for they have sometimes made themselves known in a particularly disruptive fashion.

It typically happens this way; every few years, a resident of Campolindo Drive turns on the dishwasher only to have soapy water spread across the kitchen floor. (If memory serves, it happened to my late neighbors Ben and Charlotte Glading twice, to my neighbors Dan and Mary Huntsman once, and to me twice.)

Inverness applicance repairman Dave Brast this week explained what’s been going on: “There’s one hose that drains a dishwasher, and usually it goes through a hole in the cabinet wall that separates the dishwasher nook from the space under the kitchen sink. If the sink drain goes through the wall under and behind the sink and if that hole is overly large for the drainpipe (thereby leaving a gap), a rodent can crawl from inside the wall through the gap into the under-sink space and then through the hole in the cabinet wall over to the dishwasher nook…”

(For roof rats to “enter homes and buildings,” The New York Times-owned website About.com notes, “they only need a hole the size of a quarter.”)

Brast further explained, “To do damage by gnawing through the dishwasher drain hose, the rodent can gnaw the portion of the hose under the sink or under or behind the dishwasher.

“I think the hose in the nook is the favorite target because there the rodent is completely protected from being disturbed by cats, dogs and humans….

“In the last few weeks I’ve had to repair two rat-gnawed dishwasher-drain hoses in Bolinas, one at the home of Aggie Murch and the other at the home of Charles and Veronique Fox. The two houses are on opposite sides of the road just a few hundred yards apart. The first gnawing was in the Murch house and days later in the Fox house.

“This made us wonder if it wasn’t the same rat doing the gnawing. After it gnawed through the first hose, it thought, “Well, no more to gnaw here at Murch’s. Guess I’ll mosey on over to Fox’s and see what there is to gnaw there…. Another dishwasher-hose gnawing I remember happened to Herb and Gina Kutchins’ [Inverness Park] dishwasher.”

Why do roof rats do this? “My understanding is that rodents gnaw because they have to,” Brast told me. “If they didn’t, the front teeth, which never stop growing, would get so long the animal wouldn’t be able to open its mouth wide enough to eat.” In short, it’s a dental procedure.

And there are more serious reasons for not wanting roof rats in our kitchens than periodically sudsy floors.

As reflected in their grating scientific name Rattus rattus, roof rats are notorious creatures. I’m reminded of Nabokov naming Lolita’s stepfather “Humbert Humbert” to emphasize that rat’s ugly nature.

“The roof rat… is an introduced species of rat [that is] native to southern Asia,” the University of Florida Institute of Food and Agricultural Science notes. (Florida has a particular problem with roof rats in citrus groves.) “It was brought to America on the first ships to reach the New World….

“The rat is the same species that carried the bubonic plague around the world [killing half the people in Europe during the late 1340s] and is also the host for murine typhus” in the South.

Cats kill roof rat “pups” but seldom the adults. Charlie cat seen here fence sitting belongs to neighbors Jay Haas and Didi Thompson, whose dishwasher has thus far escaped rat damage. Whether Charlie should get the credit, however, is unclear.

Because roof rats (which like to gnaw their way into attics) are arboreal — traveling along branches, utility lines, and fence tops — they seldom fall prey to cats except when the “pups” are young and still “dispersing,” the University of Florida notes.

000_0111.jpgTraps are more effective in controlling roof rats.

Hawks, such as this redtail on my hill, and owls (especially barn owls) are even better, the University of Florida reports.

A female roof rat can have as many as five litters a year of up to eight pups each. And each generation is ready to begin reproducing in three to four months.

For the past two centuries, rats have been a fact of life on every continent but Antarctica.

The so-called Norway rats or “sewer rats” (Rattus norvegicus) are actually native to northern China. They reached Europe and the Americas from Asia much later than roof rats. The University of Michigan Museum of Zoology reports they were inadvertently carried on ships to Europe in the early 1700s and the New World in the 1770s.

“In Asia, Rattus norvegicus was native to forests and brushy areas,” the museum notes. “Today, however, Norway rats find preferred habitat to be alongside the rapid expansion of the human population. Nearly every port city in the world has a substantial population of these rodents.”

I happened to have been reporting for the old San Francisco Examiner back in 1982-83 when the City of San Francisco reconditioned its cable car tracks and — while it was at it — replaced antiquated sewer lines underneath.

A supervising engineer on the sewer project told me at the time that he and another employee had recently gone into a sewer tunnel under Market Street at the edge of the Financial District. The tunnel opened into a large chamber, he said, and as the two of them shone their flashlights around the tiered vault, they saw reflections from eyes of hundreds of rats. The two men beat a hasty retreat. A typical city, the engineer noted, has one rat for every human.

In case you have your own encounter with a representative of the genus rattus and wonder just what species you’re dealing with, the easiest way to distinguish between Norway rats and roof rats is by the length of their tails.

Norway rat tails are shorter than their bodies while the tail of a roof rat is noticeably longer than its body. Norway rats have bald ears. The ears of roof rats are furry. Norway rats are only slightly longer than roof rats; in fact the rattus rattus above would probably measure more than a foot from the tip of its nose to the tip of its tail. In general, however, Norway rats are far heftier.