This is Sir Edwin Landseer’s 1837 painting Old Shepherd’s Chief Mourner.
The Encyclopedia Britannica has an amusingly evident bias on the topic of Landseer: “His paintings of animals were based on sound anatomical knowledge and, at first, were marked by healthy animation. His later works were marred, however, by anthropomorphism that lapsed into sentimentality.”
The V&A seems not to mind the anthropomorphism as much, writing that this work embodies “his speciality, the accurate and almost anthropomorphic representation of dogs and other animals. Its mixture of pathos and realism appealed to all sections of society, and the critic Ruskin praised the fine technique and the subtle choice of details.”
As for me, I’m not surprised to learn from the Tate that he “painted a number of Scottish highland subjects and, like Turner, illustrated the works of the novelist, Sir Walter Scott”—he shares, to my eye, Scott’s ability to portray sentiment with just enough wry self-awareness to remain carefully this side of mawkish.
You might disagree—perhaps he’s maudlin, perhaps he’s moving, and perhaps he’s both—in any case, his attention to detail is unambiguous.