What do the animals feel?

There are many animal behaviorists who will tell you that animals do not grieve for the lost master or an animal companion.  Perhaps some may not.  Circumstances,  such as what happens to them immediately following the loss, can create differing senarios.   For example, the dog, immediately introduced to a new home, may not have time to wonder where
the previous owner has gone or why he was removed from his familiar surroundings. Instead he adjusts to the new environment.  That is his means of survival.
Human grieving is for the most part  the sense of loneliness,
missing the voice, the presence, the warmth, the loss of the familiar and dear.
Why couldn't it be the same for the dog or cat who waits at the door for their person to come in?  Are they simply put out because the person is late-forgotten to fill the bowl?  They do not understand death  as humans do.  As far as we know,
they do not hope for eternal life.  
Whatever our religious leaning, we humans all have some expectation of  life continuing after earthly death.  Again-
as far as we know, animals do not. 
But grieve, in the sense of an absence  from their life, I have seen evidence that many definitely do.
My daughter had two cats, one an older, wise, mellow tiger."Ollie"
The second, a tuxedo feral female kitten, adopted at a very young age.   Mia,The kitten, grew to  adore her senior companion, following him about.  When they had been together several years, age and disease caught up with the
older cat and he was released from his suffering.
The little female was lost.  Always a sensitive, needy personality, she resorted to inappropriate behaviors.  My daughter tried the plug-in pheromones which helped a bit, but were not a permanent solution.  As long as she was home with Mia, holding, playing with her, things went well.  Left alone the cat relieved her stress by urinating on my daughter's bed.  YES- she had made trips to the Vet, been treated for possible urinary tract infections etc.  It was not her bladder
that needed attention.
So my daughter adopted another cat--a young, very active tuxedo male kitten.  She thought a companion to be the solution.  Max, the new-comer, quickly made himself at home.
It has been many months now, Max has yet to win over Mia.
Of course he plays very rough whereas Mia's former pal was
older and gentle, so perhaps that is the issue.
Or maybe Mia is still feeling a bit lost without her former mentor and idol.  Perhaps Mia is still grieving in her own
feline way?
You doubtless know of many cases of dogs who appeared to grieve-Hatchi,  and the little terrier in Scotland.  I knew a
Scotch Collie  once who came to our veterinary clinic regularly.  He knew us well and was always happy to "visit".
So when his owner made plans for a lengthy stay in Europe,
he left Sandy to board with us.  Sandy would not eat the first few days though the owner had brought the food which he was
used to, even his own bowl and bed.  Sandy just lay curled in
misery.  I took Sandy out in the grassy yard.  Tried to get him to play ball.  Sandy just kept staring off into the distance.
Now we began to be concerned for his health.  The Vet gave him a complete check.  Other than the obvious weight loss,
Sandy was fine.  Sandy was lonely-not just for company, but
for his personal companion.  Was he grieving?  
And then there was Hal -short for Hallelujah.  He was a barn kitty I had adopted when he was thrown out of a passing vehicle. (Named Hallelujah because he was saved).  Hal was
lonely, so my husband brought home a lovely golden female
whom he named Glory, glory.  (Not hard to figure where that came from.)  They became a bonded couple, living happily in the barn, sharing a nest in the hay and mice. There came a sad day when GG stepped into the road at the wrong moment.
I buried her under the lilac with Hal watching.  He never left her grave site--through days of rain and cold nights.  Until he too passed away to where ever the good animals go. Hal
grieved.
I love the Rainbow bridge story.  The child in the heart of me believes it, because it is a balm to human grief.
How exciting to think we will meet our dear human friends again and be surrounded by those pets we have loved on earth.
And  I do believe that animals understand grief too, in their
own way, but just as deeply, as we humans.

photo: Ollie, the wise old cat