Gambian pouched rat

But first, a bit more about the Gambian pouched rat, which is, for the record, among the largest rodents out there.

It's actually not a rat, but more like a gigantic hamster, with cheek pouches big enough to hoard several pounds of food at a time.

Capybara

Behold, the largest rodent in the world: the capybara, a South American denizen that can grow to a size of nearly 4.5 feet long. (As far as weight, they can tip the scales at more than 145 pounds.)

Here, a capybara walks with a squirrel monkey on its head at Tobu Zoo in Saitama, Japan. Tobu Zoo is the only zoo in Japan that raises capybaras and squirrel monkeys in the same cage, which is called "capybara taxi" with good reason.

Little big rodents

At birth, capybaras already weigh 2 to 3 pounds.

Giant flying squirrels

Didn't know flying squirrels came in Boeing size, did you? Well, meet the red and white giant flying squirrel, also known as the Chinese flying squirrel, the largest flying squirrel on Earth.

As a matter of fact, they do grow on trees...

...and they can grow to more than 3 feet long, including their tails.

Cape porcupine

You're looking at the largest rodent in southern Africa...and the world's largest porcupine. Cape porcupines can weigh more than 60 pounds.

They'll eat your plants

They're a common sight in southern Africa. A favorite delicacy: bulbs, including types that are poisonous to other animals.

Maned rats

These African rats might look like porcupines (more on those later) but they aren't. They're rats. The wild rats you might see in big-city sewers might grow to an average of 20 inches long (including tail), but maned rats...

Larger than what you've got at home

...can grow even bigger than that. Their bushy coats, which make them look even bigger, can make themselves known on baby maned rats as young as 20 days.

Nutria

They look at bit like beavers with little tails, or large rats, but in reality, nutria, or coypu, are neither. They're semiaquatic rodents that can grow to about 2 feet long.

Nutria

This nutria, nibbling on vegetables in a Swiss zoo, shows off its back feet, which, like many aquatic rodents', are webbed.

Hoary marmot

When it comes to North American ground squirrels, their largest cousin is...this, the hoary marmot, also known as the whistle pig. They've been known to grow up to 30 pounds (if they're really huge), and are similar in size to the alpine marmot, which sometimes also claims the title of largest ground squirrel.

Here's one on Mount Edith Cavell, in Jasper National Park, Canada.

Variable sizes

If you run into a runty-looking hoary marmot weighing in at only, say, 8 pounds, that's also normal; their weights ebb and flow throughout the year.

North American beaver

If you were wondering about the largest rodent in North America, here it is. This beaver typically weighs about 44 pounds, though its kind can grow much larger.

Heavier than a human child

One North American beaver was catalogued at weighing 110 pounds. The breed has been a source of meat to several populations over the centuries...but nowadays, the BeaverTails you get in Canada are more like donuts.