Nico can walk the shelter hallway without much trouble.

The six-year-old Belgian Malinois mix notices doors opening, people moving, and dogs watching from neighboring kennels. His ears turn toward sounds. His eyes scan ahead. He keeps moving.

Then he reaches the glass door at the end of the corridor.

Nico stops.

There is another dog standing directly in front of him.

At least, that is what the glass appears to show.

Nico's body stiffens.

The dog in the glass stiffens too.

He steps forward.

So does the other dog.

Then Nico explodes.

He lunges at the reflection, barking and growling as his muzzle strikes the glass. He snaps directly toward the reflected dog's face.

A second later, Nico recoils.

He races backward, putting as much distance as possible between himself and the glass.

It looks as though the encounter is finished.

But within seconds, Nico turns around.

He stares down the hallway.

The reflection is still there.

Slowly, he walks back toward it.

And the entire sequence begins again.

Nico Doesn't Simply Bark at the Glass and Move On

That is what makes the behavior unusual.

Plenty of dogs react to reflections.

Some investigate.

Some bark.

Some lose interest once they discover there is no scent or physical dog behind the image.

Nico cannot seem to reach that conclusion.

He attacks.

Retreats.

Then voluntarily returns.

His First Approach Can Look Completely Normal

Nico walks toward the end of the hallway.

His body is loose enough.

Then he notices movement in the glass.

His head lifts.

His ears come forward.

His pace slows.

He stares.

For a few seconds, neither “dog” moves much.

Then Nico shifts his weight.

The reflection does exactly the same thing.

Every Signal Comes Back at Him

When Nico becomes rigid, the reflected dog becomes rigid.

When he moves forward, it approaches.

When his head rises, its head rises.

When Nico bares his teeth, he sees another dog baring its teeth directly back at him.

That visual feedback can escalate extremely quickly.

Nico cannot create distance by intimidating the image.

Everything he does is returned perfectly.

Then He Lunges

His bark hits the glass at close range.

His paws may slide forward.

His muzzle reaches the surface.