Well, I have been forced to eat my words with respect to the Wild Dog in Island of Happiness. With only a stone pen but with my dog at 10 hearts, I had been able to leave my chickens outside overnight throughout the Summer season without one incident where any of them developed the telltale stress signs that indicate 'damage' from an attack. Now, however, to my dismay, I have experienced betrayal from my canine pet.
It was a sunny day yesterday and all my chickens sunned themselves in their pen throughout the day, falling asleep peacefully at night as usual...
I went fishing in order to keep my shipments of fish at a level that would keep all the Fishing characters on the Island, returning home only at 11.40 p.m.
There had been no barking to indicate the presence of the Wild Dog anywhere, but when I entered my field, I saw the creature slinking about silently near the Chicken Pen.
The Chickens continued to sleep peacefully... but then I found my DOG sleeping as well! He could not be roused to do his duty either. I picked him up, but as soon as I put him down, he fell asleep again, ignoring the continuing threat of the Wild Dog!
I equipped a tool but by now it was 1.00 a.m., the time when the Wild Dog leaves of his own accord. He departed as silently as he had appeared.
This morning, rather to my dismay, I found that three of my Chickens were stressed. How could my Dog betray me so, after all the Pet Food, petting and holding I did to bring him to 10 hearts!
So I guess you can't count on your Dog to keep the Wild Dog at bay, even if he has done so dozens of times in the past. I must add here that my Dog certainly has demonstrated the ability to go after the Wild Dog. On many occasions, he has sent him howling from the field... so what happened last night???
In many Harvest Moon games, a pen made of stones or branches is not sufficient to protect chickens or livestock. Perhaps Island of Happiness is the same. I simply didn't have the heart to rebuild the pen with better materials, as it takes so long to position each item on the ground in this game.
The other possibility is that the Dog is not fully trained until his title reaches that of Gold Medal Dog, which would occur when he has participated in three Dog Contests. (Apparently, an animal does not have to Win the Contest to gain a higher title. A Chicken who lost the first Chicken Contest nonetheless was given the title of Copper Medal Chicken. When she won the 2nd, she was given the title of Silver Medal Chicken. My Cow who won her first Contest was given the title of Copper Medal Cow, even though she won first prize. So the title depends on participation rather than winning, evidently.)