There is some scientific evidence that shows dogs may suffer from depression just like humans, but can we really tell if a dog willingly committed suicide?
Regardless of which side of the road you stand on regarding doggy suicide consider this- there's a bridge in Scotland dubbed "Dog's Suicide Bridge" because more than fifty dogs have leapt off the bridge and died in the last 50 years.
One particular section of the Overtoun Bridge near Dumbarton seems to have a strange effect on dogs of a certain breed, causing them to heedlessly leap off the side and "commit suicide":
All of the deaths occurred at the very same spot on the right-hand side of the bridge. All of the dogs who died were long muzzle breeds like Collie, Labrador, or Greyhound. All of the deaths took place on bright, clear days.
Over six months in 2005, five dogs leaped to their deaths. One bereaved owner, Donna Cooper was out walking with her family when her dog, Ben jumped over the parapet and fell fifty feet onto the rocks below.
Some people think the bridge is haunted by an evil spirit, others think it's situated in a "thin place" where our world meets with the "Otherside" so dogs are trying to leap into this other world.
But animal behaviorist Dr. David Sands has posited the most popular theory- their leaping over the side because they smell mink:
Sands uncovered the most likely explanation for the dog deaths is the onset of mink farming in the area, which started fifty years ago:
Evidence of mink was confirmed in the area not only by a naturalist, who spotted droppings beneath the bridge, but also by [an angler], who explained that the top hill quarry had lakes that contained trout (perfect mink diet).
The intense scent of mink aroused each dog’s curiosity, leading to their fatal leap of faith.
https://skeptoid.com/episodes/4320