I can never find a ballpoint pen when I need one, but somehow Angus has no trouble.

Four times in the past month I have found him lying contentedly on the landing of our stairs, gnawing away, surrounded by tiny bits of plastic, ink stains all over the carpeting.

I take the pen away (or what’s left of it), shake it in his face, and say sharply, “What’s this? What’s this?”

That always worked with my first dog, Toby, who learned pretty quickly that whatever prompted that question was contraband and should either be hidden or avoided but not chewed out in the open.

Angus never seems to learn this. He looks startled by my sharp tone, sinks down until he is flat, gives me the big eyes. His expression says, Don’t beat me again, please! (As if I ever would.) And then a few days later, he finds another pen (Where? Where is he getting these?) and trots up to the landing, lies down, and chews.

It is not a surprise, I guess, that the way I chastised Toby doesn’t work on Angus — they are not very similar dogs. Nor is Rosie, our seven-year-old Lab mix, much like Riley, Angus’ predecessor. And Riley wasn’t anything like Boscoe, our second dog. In fact, in 25 years of living with dogs, I think I can safely say that the lessons I learned from one dog can only rarely be applied to the next dog.

Rosie is a rescue from Missouri, and any temperature below 30 degrees makes her unhappy; in deep winter, she shivers so hard (even with a fleece jacket) that the whole leash trembles. When we walk, she barks at the cold.

Angus is a rescue from the rez, born at the beginning of winter, and he loves snow. Boscoe had the thick double coat of a border collie and in summer he would trudge so slowly we worried that he was sick — and then when the heat broke, he was fine.

Rosie and Angus both went through leash-training class. Rosie has been perfect ever since, walking at our side, leash loose, matching her pace to ours.

Angus? Not a prayer. He aced the class and the minute it was over he forgot everything he had learned. That was in August, which means that for four months now I’ve been working with him daily, stopping him when he pulls, making him sit, saying, “Walk” in a brisk tone, and within seconds he’s dragging me down the block again. He stares at squirrels, or potential squirrels, or places where squirrels once were, and he strains against the leash.

Our dogs’ personalities were apparent from puppyhood: Rosie was stubborn. Riley was nervous. Toby was tennis-ball-obsessed. Boscoe was as good as gold.

And Angus? Angus is — oblivious. Cheerful. Good-natured to the core. He bumbles around and rears up on his hind legs to see what we’ve got on the table, and he grabs the dish towel and trots off with it, and we take it away from him, and he hops up on the couch and kind of languidly, absently, opens his mouth and starts chewing a big damp hole in the pillow.

And each time, when I say “No!” or “Stop!” or “What’s this?” he looks abashed, astounded, worried — Don’t beat me again! And then a few seconds later he’s rearing up on those hind legs again because, gosh darn it, maybe there’s something entirely new on the table, and —

All dogs are different. Angus is not like Rosie, he’s not like Toby, he’ll never be as perfect as Boscoe. He’s just exactly like himself, and that’s OK — it’s all we want. (But please leave my pens alone.)

Laurie Hertzel is documenting a year with a rescue puppy on these pages. Follow along at startribune.com/puppy

Coming Dec. 29: Tips from Angus on how to raise a puppy.