I have had many pets in my life, and I perfectly know that animal behavior can be explained by the laws of physics without the hypothesis that they are conscious.
Now we know that it is possible to simulate with a computer every feature of the behavior of animals, including their capacity to learn and their apparent capacity to recognize their image in a mirror.
An adequate software can allow the computer to record input data, analyze them and give specific outputs; all these operations occur automatically, without any consciousness, any sensations, any emotions, any thoughts. For example a computer, connected to a camera, can analyse the external images; this occur automatically through some mathematical algorithms, and the computer has no visual sensations. This proves that the fact that a dog can distinguish a bone from a stick, does not imply that the dog has a visual sensation.
Therefore it is not possible to exclude from a scientific and rational point of view, that the life of animals is only a purely biological/chemical process without any kind of consciousness (neither sensations or emotions).
In other words, science cannot exclude the possibility that the animal is only a biological robot, feeling nothing at all, which actions and reactions are uniquely determined by a chemical software implanted in its brain.
It is also possible to explain those behaviors of animals, which are usually considered as an indication of emotions.
For example, the dogs which, because of some genetic mutations, presented some affectionate behaviors, had a greater probability to be adopted by man, and consequently, to survive. It was sufficient that the animal presented those behaviors also towards only a member of the family (even not the one who gave it food) to be accepted by the family. It would be only a case of natural selection, even if unawares induced by man, who has programmed the behavior and the reactions of the dog.
Since we have no way to observe directly the existence of any kind of consciousness in animals, and the hypothesis of existence of consciousness in animals is not necessary to explain the observable phenomena in animals, we can conclude that there is no experimental or scientific evidence of the existence of any kind of consciousness in animals, neither sensations or emotions.
The idea that animals have sensations and emotions is then only an arbitrary hypothesis, without any scientific or rational foundations.
Such an hypothesis can be considered only a reminiscence of childhood, since all children tend to ascribe to animals thoughts, sensations and emotions. Besides, primitive peoples were used to anthropomorphize many natural elements; the sun, the moon, the mountains, animals, etc.
During history man has then understood that natural phenomena occur automatically because of specific natural laws: man has understood that nature is only an object and not a person. The anthropomorfic concept of animals is then only the last residue of this inclination to anthropomorphize natural processes. Now the technological and scientific progress allow us to explain the behavior of animals without ascribing them any anthropomorphic features.