Despite what many think, animals cannot feel emotions. They are driven completely by instinct.
Elephants, monkeys, dogs, cats, etc. Do not feel emotions. They do not love you or hate you, you are a liter mate and they respond to you as one of the pack. Licking is a natural response, just like barking, and purring in a cat.
Your dog and cat know you provide the food, just like their mothers did.
If you die in your house and no once finds you, your cat will start eating you within two days; it usually take the dog about three days. But, both will eat you when they are hungry.
It is well documented that animals suffer grief; in fact, perhaps their grief, like their other emotions, is even more pure than humans. Perhaps it might seem that humans suffer grief more deeply simply because their feelings and emotions are extremely complex, but that does not mean that it is any less painful.
No its not because animals can also feel grief I know this from personal experience I had a chicken who lost a baby chick and she got pretty stressed and grieved for quite a while I think also its a parental instinct a little bit because parents grieve really badly if they lose a child etc.
Grief is caused by a lot of other animals. For example when a close family member leaves a Gorilla they are upset and feel grief, same with other herds. Also when we sin then God also feels grief - If you believe in him. Grief is for any being with feelings - which is a lot.
There have been studies in the the symptoms of animal depression already. We know that they can have the same or similar emotional and physiological responses as humans do.
As for the unique response of grief, many animals can have emotional responses similar to humans. Examples include the following:
"King tells of elephants surrounding their matriarch as she weakens and dies, and, in the following days, attending to her corpse as if holding a vigil. A housecat loses her sister, from whom she's never before been parted, and spends weeks pacing the apartment, wailing plaintively. A baboon loses her daughter to a predator and sinks into grief. In each case, King uses her anthropological training to interpret and try to explain what we see—to help us understand this animal grief properly, as something neither the same as nor wholly different from the human experience of loss."
Also from personal experience, I have seen my dog grieve from the loss of my other dog. One day, my two dogs ran away together for about two days. We later got a call from the pound explaining how one of the was hit by a car, and my other dog was at the pound. Not only did this make me sad, but it devastated my dog. You could tell that her whole attitude changed completely for a few days. Instead of running around and being hyper, she walked around slowly and didn't show any signs of being happy. She also didn't eat as much, from a loss in appetite.
There is ample evidence that animals can have grief, just as many other responses humans can have to their environment.
Grief is not a uniquely human trait. There are many documented cases in which other species demonstrate the traits characteristic of grief. One such example are elephants. Elephants are well-known for their familial attachment -- some studies acknowledging that young elephants who witness the death of a parent commonly wake to screaming fits, indicating that they continue to be haunted by grief-stricken dreams. It has also been noted that some primates go so far as to perform wake-like 'ceremonies' for other primates in their group.