Elderly pets: Time to go, or perhaps not? The Last Walk: Reflections On Our Pets at the End of Their Lives. By Jessica Pierce. University of Chicago Press; 263 pages; $26 and £17. JESSICA PIERCE, a bio-ethicist with a particular interest in animal welfare, poses complex questions about our moral responsibilities towards our pets as they reach the end of their lives. What constitutes a "good death"? A bad death is relatively easy to define - a death in pain, fear or distress - but a good one is harder to pin down. For most pet owners a good death means painless euthanasia in either a veterinary surgery or at home. The author of "The Last Walk" is edgy about this. "Why is it," she writes, "that we have such a revulsion against euthanasia for human beings, yet when it comes to animals this good death comes to feel almost obligatory?" She goes on to ask whether for some animals a natural death is preferable to euthanasia and wonders at what point life for our pets becomes burdensome. More to the point she questions where that burden falls: on the pet itself or on ourselves, the pet owners who are challenged, frustrated, and often annoyed by the decline of a once vigorous animal. Ms Pierce's musings on the ethics and morals of how we, as humans, judge the quality of life of our animals is interspersed with the "Ody Journal," which she began keeping in the autumn of 2009. The diary, about the physical and mental decline of Ody, her 13-year-old Vizsla who joined Ms Pierce's family in 1996 as a "ten-week-old wriggling sack of loose red skin" pulls no punches. She writes honestly and movingly about how his ageing and health problems increasingly take centre stage. As with most pet owners, she is comfortable talking about uncomfortable facts: the shit and the bad breath, the weakened back legs and falls, the night-time barking, the vomiting and general confusion. Underlining this is her own distress at Ody's ageing: "changes are so gradual I almost don't see them happening" but which add to her growing concern about what will happen to him when his time comes. "How do I judge the quality of his daily life, as he experiences it?" she asks. It is an uneasy question that millions of pet owners around the world will have to ask of their pet one day.