‘YOU’RE SEEING SOMETHING pretty special here,’ our guide said, and led us down a darkened path. If our sleepover at the zoo was an Agatha Christie novel – and there were undeniable Christie elements: thirty strangers in close proximity, atmospheric lighting, lions waiting to be fed – the first victim was surely about to fall. My wife nudged in closer. Our crowd grew hushed. Possums breathed heavily nearby.

We were using red-light torches to navigate Melbourne Zoo after dark. Red light doesn’t startle animals or hurt their eyes, but it has the curious effect of flattening the landscape it reveals, turning everything into shades of grey and tan. As a result, the enormous stick insects we were looking for seemed to be invisible and then suddenly there all at once: clinging to the window of their private enclosure, some larger than my hand. Antennae flickered with gentle indifference. Our group took turns squeezing forward to the small window to peer at them in squeamish delight.