Holding my pet rat Molly one evening in my lap as she devoured a chip of dried banana, her little heart pumping against my thigh, I wondered how many beats she had left.
She was by now just over two years old and beginning to show her age (rats live until three if they are lucky). Normally so immaculately groomed, her soft grey fur was increasingly unkempt. Her tail drooped behind her like a loose shoelace.
Her sister, Ermintrude, was also visibly ageing. A few months previously she had developed a small lump on her chest. Female rats are prone to fibroadenomas (benign tumours in their mammary glands), which are also common in humans. The lump was giving her no obvious discomfort and she was as energetic and affectionate as before, still able to groom.
