In autumn we often have an increase in calls about rodents; the cold weather and decrease in food sources outside make moving indoors an attractive option for urban rodents. The rodents we encounter are predominately House Mice (Mus musculus), Norway Rats (Rattus norvegicus), and Roof Rats (Rattus rattus), with the occasional squirrel to keep things interesting.
There are over a thousand species of rodents in the order Rodentia, and they all possess teeth specialized for gnawing, which provides the order's Latin name (from rodere, to gnaw). Below are some of our favorite species that we don't tend to encounter (fortunately or unfortunately).
Beaver (Castor canadensis)
The beaver had a profound impact on the exploration and settlement of North American by Europeans as its dense fur was prized by trappers. They can still be found in much of this Beaver State, and ODFW has strict rules regarding their trapping and relocation. This is in part because of the profound impact they can have on forests--beavers fell trees to create dams, so dramatically altering wetland habitats that they are often called "ecosystem engineers."
Naked Mole Rats (Heterocephalus glaber)
Naked mole rats spend their entire lives underground below the East African deserts, where they use their powerful incisors to gnaw tunnels and devour tubers. As the temperature in their tunnels stays constant, they have lost the ability to regulate their body temperature. These fascinating creatures have a host of other unusual adaptations including incredible longevity and resistance to cancer. They can live over thirty years, whereas most Norway rats don't make it past two. Perhaps the weirdest thing about them is that they live in eusocial colonies similar to ants or termites, where one female reproduces and the rest act as a worker caste. The individual pictured above is a pregnant queen.
Porcupine (Hystricidae and Erethizontidae Families)
The most amazing thing about porcupines is that they evolved twice! The porcupines in North and South America are more closely related to Guinea pigs and Capybara than they are to the species from Africa and Asia, though they both have the characteristic quills as a defense. The video clip above from the Oregon Zoo shows one of the keepers taking an African Crested Porcupine for a walk around the zoo. Neither the New World or Old World porcupines are capable of throwing their quills, though they are loosely attached and can fall out like any other hair (especially when embedded in the nose of a potential predator). North American porcupines are found in Oregon, but are seldom seen due to their nocturnal and arboreal nature.