飼い主が自分の名前を呼ぶまでゲート前で待機していて、呼ばれるとゲートを通る犬たちの様子です。
きちんと待つことを覚えて、自分の名前も理解していてる賢い犬たちです。エコー（Echo）と名付けられた犬は、その名の通り2回名前を呼ぶ必要があるみたいです。
Translated from Japanese by Google
It is a state of dogs waiting in front of the gate until the owner calls their name and passing through the gate when called.
“They’re smart dogs who know how to wait and know their names.” A dog named Echo needs to be called twice.
[reddit] They named him Echo because you have to say his name twice.