This morning, anticipating a run to the store to get dog food, I caught myself calculating whether I should purchase a smaller bag than usual.

Maple, our 12-year-old chow mix, is showing multiple signs of aging, and those larger bags of dry food are pretty expensive. I never know when I might wake up and find her dead.

Weird, I know. But many pets have come and gone in my life. Death is inevitable.

After years of running and leaping, she has slowed down. Way down. We thought this last summer was the end for her, until she perked up in the fall as the temperature cooled down.

Now, though, it’s winter and she spends about 20 hours a day sleeping.

We’ll miss our dog when she dies, that’s for sure. Our sons named this stray mutt Mabel when she first came to our house, amid a pack of similarly free-range dogs. Once she stayed, the label Mabel somehow morphed into Maple, a description matching the color of her deeply golden fur.

This forty-pound canine will be even more missed, I speculate, by her pet companion, Ambrose. Ambrose is our male, jet-black cat, and he too went through a name transition in his early existence.

Ambrose came to us about 10 years ago with his sister Pearl. Our sons named them, except Ambrose was initially called Ambrosia. When we figured out he was a male cat, Ambrosia easily became Ambrose, not the least because Ambrose Bierce was a great writer with an Indiana tie.

Last year, Pearl died abruptly, with no forewarning. We found her upstairs on the carpet, stricken by something, possibility a rogue hairball. Her claws were tightly gripped to the carpet’s fibers and lifting her was like pulling on the Mother of all Velcro. By night, she was buried in the yard, like so many of our pets before her.

Ambrose, already bonded to Maple, has really missed his sister, and so it’s easy to surmise that bond has grown deeper. Aesthetically, they are quite the pair, both richly hued in their fur color. They trot around together, Ambrose caressing Maple with his tail, Maple nosing Ambrose with her muzzle.

They are an especially apt partnership in their ability to get in and out of the house, a kind of domestic circus act.

Our back door, if not dead-bolted, presents opportunity for entrance and exit, and each animal is specialized in their talent.

Maple is a bit of a brute. When she’s outdoors and wants to come in, she just bulldozes the door open, with Ambrose often exploiting this break to enter the house as well. Ambrose’s talents are more refined. Again, unless the door is latched, Ambrose can get his claws between the door and the jam, and — incrementally — pull the door open.

It’s something to behold, the torque this cat can muster.

Maple waits patiently behind him as Ambrose works the crevice until it’s ajar and the two can then spring their way to the backyard.

These orchestrated comings and goings are on the wane. Maple would rather sleep, dreaming of a more athletic youth when she would chase after cars and squirrels, and bark at anything that moved.

Her barks are few and far between: thus my calculation of the size of the dog food bag.

I trust I’m not being so much heartless about it as I am preparing my heart for her inevitable, final exit.

Ambrose is not engaged in any mathematics. He just enjoys the feel of a body right beside him, matching his gait, a four-legged creature he can touch with his tail.

I don’t know how he’ll get back into the house once Maple’s gone. I guess he’ll just sit there and wait. And then wait some more.