As you’ve probably heard, it’s Groundhog Day, the one day a year where it’s fine for everyone in the country to obsess over a big ol’ rodent.
It’s become a running joke here at Earther that I’m a bit rodent-obsessed. In my (totally correct) opinion, there’s nothing cooler than an urban animal, which means rats and squirrels are high up on my list.
So, in the spirit of Groundhog Day, I thought I’d introduce you all to some of the coolest rodents that also deserve their day in the sun—or not, because some of these guys are definitely nocturnal.
In college, I took a class called Mammalian Ecology where the lab portion involved learning how to identify any mammal by just its skull and dentition. The TA for the class is doing on his Ph.D on rodent morphology and the biomechanics of rodent chewing, and we spent a lot of time focusing on this group of mammals, so please bear with me.
Rodents (Order: Rodentia) are a part of the mammalian superorder Euarchontaglires, which also includes rabbits/hares (Order: Lagomorpha), flying lemurs (Order: Dermoptera), tree shrews (Order: Scandentia), and primates (Order: Primates, duh).
Our friend the groundhog, Marmota monax, is also commonly referred to as a whistlepig, woodchuck, or a marmot. They’re widespread across North America and are actually a kind of ground squirrel!
I learned about these guys in a biogeography class I took. The professor studies them and other mammals in the Philippines, which, due to the way the islands formed, has some pretty unique mammals.
According to arkive.org, these furballs are shy, nocturnal creatures that live in the trees in the mountainous Northern region of the Filipino island of Luzon. They’re also about the size of a house cat, with a long tail. They kind of remind me of opossums, which are marsupials and not rodents.
Degus might be familiar to people because they’re often kept as pets, but they’re native to southwestern South America. They’re a part of the suborder Hystricomorpha, which includes some porcupines, the much-loved capybara, and a bunch of other really cool rodents. But degus are super cool to me because of their teeth, which is one of the best ways you can differentiate rodents when you only have their skulls to go by. Their teeth form figure eight-like wear patterns which are pretty neat looking, and also explain why this family of rodents is called Octodontidae (“eight teeth”).
Because of the biomechanics of how they chew, degus, like many other hystricomorphs, have some of the most remarkable teeth in the animal kingdom.
First things first: mountain beavers ARE NOT BEAVERS! These lil babes are the only living species in both the Family Aplodontiidae and the Genus Aplodontia, neither of which are a part of the beaver family. They don’t even live in the water or build dams!
What I love about them is the way that they chew. They’re the only species of rodents who’s jaw musculature and skull shape can be described as protrogomorphous. This just means that the animal’s three masseter, or jaw, muscles connect to its skull in a different way than in any other rodent. You can see in this diagram how the lateral masseter muscle attaches differently on the mountain beaver (top left) versus our friend the groundhog (top right).
Mountain beavers are the last species left whose muscles connect this way: as rodents diversified into different niches and started eating different kinds of food, their jaws changed to accommodate those lifestyles. They’re basically living fossils.
Anyway, there are tons more rodents and Fun Rodent Facts where this comes from, but I could go on for days about rodents and still not be done. Have a good six more weeks of winter (if you trust Phil’s judgement) and remember: there’s more good rodents out there than just Pizza Rat and capybaras.