Why McConaughey smeared dog?

Funny scene has recently witnessed paparazzi: Actor Matthew McConaughey was walking down the street, and walked beside spattered with mud dog star (once the dog was a white suit).

The most interesting is that this day was dry, sunny weather and no pools in Beverly Hills was not, therefore, doubly unclear where the dog found a quantity of mud up to their ears to be in the mud!

By the way, this dog lived with Matthew recently, he was still a puppy and named BJ.