If I had not witness it for myself they would be doubts in my mind, especially when there is a loss be it a human being or animal no matter where it took place especially if it is your pet who became a mother for the first time this loss took placed on a farm.
I had the opportunity of helping a good friend of mine, I grew up with, my vacation was spent on his farm helping him do some chores he needed to complete. on this particular sunny morning as I entered the pasture one of the cows ( Miserable) gave birth to a beautiful black and white (bull) calf weighing around a hundred pounds.
I witnessed first hand the interaction between mother and son whenever she came to be milked both morning and evening with the rest of the herd, on the fifth day after giving birth on a rainy morning while doing some gardening one of the cow in the herd butt the young bull in the midsection which let out a loud moo, and within seconds slump to the ground lying helpless and not moving.
Within a couple of minutes the calf died. The mother (Miserable) came over where her son (the Calf) laid, started mooing loud and constantly for a long time, sensing something was wrong stood at the side of her son licking him as if to say get up it's time for your milk.
This mooing went on for three days during the milking period she (the mother cow) would walk over to the spot each time and stand where her son died and mooed until it was time for her to join the rest of the herd and return to the pasture.
This type of behavior expressed by a mother cow for the loss of her calf showed me that animals do mourn whenever their young dies, regardless of what people might say, they do not believe animals grieve take it from me seeing it first hand they do.
The doubts that I had about animals mourning or grieving call it what you want for their young is in fact true, in the animal world we may not see it ourselves but when we hear stories of people saying that their pets mourn when there is a loss of a young do not doubt them at all.
