From a NYTimes article about White God, a prize-winning Hungarian film with a cast of 200+ dogs who have to act in sophisticated ways:
It took more than five months to prepare the dogs: training them and dismissing dominant ones from the pack.
Dozens of trainers took part, forming small packs to allow the animals to acclimate to one another, then increasing the size of the packs as the dogs grew friendlier with one another.
“It’s unheard-of in the typical modern-day film industry to take that much time to put this together instead of quickly just using special effects,” Ms. Miller said.
“A lot of the introverted or depressed dogs involved really found a sense of purpose,” she added. “You started to see their confidence built in having this routine. They had something to look forward to.” All the dogs were adopted after shooting was completed, according to the filmmakers, and Ms. Miller said the shift in their demeanor probably helped.