I found this photo (along with another) here, where we're told that it was taken on January 19th in Hanam City near the Paldang Bridge. The animal is a jokjebi, or weasel. I've seen weasel-like animals in fields near Gimpo Airport and in Magok-dong, but I'm not sure if this is the same animal, as both times they appeared only briefly at dusk. It's always nice to run into mammals in Seoul, as they're not so easy to see here (despite the wild boar 'invasion' three years ago). To the west of Seoul, along the Han River, barbed wire put in place by the military decades ago has created a nature reserve, where even elk can be found. As this Donga Ilbo article reveals, however, this area will soon see the barbed wire removed, so the fate of this accidental preserve is up in the air at the moment.
To finish off, here's a little wisdom from Homer Simpson: "Weaseling out of stuff is what separates humans from the animals. Except the weasel."