FROM MY TREE, I can almost make out José's rebuilt lodge, a bankside mound of twigs roughly three feet high and concealed under small trees, along with a few of the saplings he's felled. (So far, the garden's caretakers don't mind.)

Nothing really happens for three hours. Daylight twinkles through the leafy canopy. Songbirds chirp like R2–D2. The noise of cars on Fordham Road, only a couple hundred yards away, plays a low B–flat, cut through by the farting of an 18–wheeler's Jake Brake. Squirrels wrestle and tumble through the dried oak leaves. Four mallards with emerald–green heads paddle downstream in peloton formation. It's not exactly Walden, but in a city with one resident per five square feet, your own tree, even one full of ants, feels luxurious.

Experts warned that I wouldn't be able to discern much. Beavers must be trapped to determine their age and sex, a trauma–inducing tactic best avoided. As for where José came from, they can only guess. Most likely he was beavering away upstate near Valhalla when a flood washed him some 18 miles downstream. Now he's alone in the Bronx.

At dusk, just as I'm beginning to lose faith, he appears.

Hooray!

He looks healthy, almost gordo. Forty pounds, I'd guess. A streak of khaki fur under his syrupy eyes darkens to chestnut on his sleek, half-submerged back. His tail looks like a fraternity paddle, and it isn't chewed up from what could have been a wild ride through the Bronx River's Kensico Dam. City life appears to be treating him well.

He lazily munches branches, typewriter style, scratches his funnel–shaped ear with his paw, then drifts away as I take pictures in the fading light. A canvas satchel of oranges floats by. (Later, I'll learn that the oranges were set adrift upstream as part of a ritual performed by practitioners of Santería, a fusion of tribal West African and Christian beliefs.) José taps the fruit with his glistening nose, then grabs a few twigs from a logjam, kick–turns, and dives toward the lodge, trailing leaves on the surface.

His appearance brings the river to life. A snapping turtle with vicious claws run–walks for cover in murkier water, apparently causing a carp the size of a child to breach. From the cover of creeping vines, this flushes out … a baby beaver?! He's right underfoot, small enough to fit in a shoe box, same nose and ears as José's but with a thin, scaly tail. Spooked, he paddles for the opposite bank, tacks upstream, then down, and then disappears.

Hmmm. Maybe the scientists are wrong. Maybe José has found a mate.