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The Mysterious Case of the Plantar Tubercles

The bottom of Eek's hindfootEek's feet have unexpectedly knobby bottoms. Those familiar with pet rats often comment in wonder about her unusual feet. In researching them, I learned that those knobs are called "plantar tubercles", and that they are useful in identifying various rodent species. The Florida mouse, for example, has five plantar tubercles on each hind foot, while the Hispid Cotton rat has six on each hind foot.

While researching plantar tubercles on rats, Google kept suggesting pages about plantar tubercles identifying woodrats. Then I came across a picture of a woodrat...

It has always been obvious that Eek is not a "regular" pet rat; meaning she is not a brown rat also known as a Rattus norvegicus. The conclusion drawn was that she therefore must be a black rat, also known as a ship rat, roof rat and Rattus rattus. However, there have always been aspects of Eek that didn't fully fit that specific identification. Black rats do have larger ears, but every picture of a black rat has quite small ears in comparison to Eek. Black rats are smaller than brown rats, and Eek is indeed smaller. But black rats are described as having sleek and graceful bodies. Eek's body is, instead, very round and compact. Black rats have a "conical" head shape in comparison to the more blunt nosed brown rats. But the shape of Eek's head is blunter and more boxy than Scribble, our resident Rattus norvegicus or brown rat. Black rats are usually one solid color. Eek has a strikingly white underbelly. Black rats have scaled tails. Eek's tale is furred. And then there were the tubercles. Neither black nor brown rats are known to have particularly pronounced tubercles on their feet.

It is the tubercles that lead to the woodrat, which, unlike the black and brown rat, is a native species to this area. The Neotoma fuscipes, also known as the Dusky-footed Woodrat, lives throughout coastal California. Known for huge ears, enormous whiskers, industriousness and charming personalities, they have round compact bodies, very blunt shaped heads, and furred tails. Dusky-footed Woodrats have unusually soft buff colored fur, with black guard hairs and white underbellies. As several web pages about the Dusky-footed Woodrat note, they are often misidentified as black or brown rats, especially when young. And they have pronounced tubercles on the bottoms of their dusky colored feet.

These type of woodrats are known to be mostly solitary and territorial. Mainly nocturnal, they like to build enormous and often complex well-built houses out of sticks and debris. And they are dedicated food hoarders. Woodrats are known to thump their tails in warning. This is sounding more and more like a dear well-known little rodent who is currently living in my house. An email was sent to our vet for further confirmation. Check out the WikiPedia pages for brown rat (like Scribble), black rat and woodrat, especially one of a Dusky-footed Woodrat, then look at a picture of Eek. The conclusion seems inescapable.

For comparison, an image of the bottom of one of Scribble's hind feet can be found here.

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Blog_post | by Dr. Radut