This started out as lighthearted banter between two Twitter celebrities, author Neil Gaiman and composer Lin-Manuel Miranda. But there was a question about the species of the animal in the picture. Luckily, a public forum will attract Those Who Know. One response began,
As a rodent biologist, I couldn’t resist putting in my two cents. I have no idea how old this thread is, but here goes. So, it’s hard to see in the original tweet if the rodent of interest is a vole or a muskrat. Now, I think we’ve all adequately described why it isn’t a beaver (though I didn’t see mention of the pronounced lids over a beaver’s eyes, or the high positioning of the eyes on the head, or the almost invisible ears, all of which I find more reliable than the big naked nose).
Tumblr member badhandful goes on to explain more differences between the critters. A lot more. You can see the whole exchange at Gaiman’s blog. Now I will be able to distinguish between the three rodents when they invade my backyard, but we still don’t know where Lin-Manuel Miranda gets his creativity. -via Metafilter