Why Hasn’t Evolution Made Another Platypus?

Snuffling through the underbrush, the shaggy little creature wanders through the sylvan night, sticking its nose in one place, then another, seeking the aroma of its soft-bodied dinner. The forest is dark and the pixie’s eyesight poor, but long whiskers and a keen sense of smell allow it to get around. Threatened, it takes off at breakneck speed, barreling through the vegetation, ducking through holes, soon lost from sight.

An entirely unexceptional lifestyle. Many animals spend their nights cruising the forest floor, searching for small prey in a similar fashion: Hedgehogs, shrews, weasels, to name a few, and bigger ones, too, like opossums and even pigs. The world is full of them.

But this one is different. All the others are hairy. This one’s pelage is also soft, made up of millions of thin strands. But they’re not hair. All the others move about on four legs and bear live young. Not this one.

Scratching, probing, sniffing, the animal often duets with its mate, calling back and forth, remaining in contact as they traverse their territory. And as the male calls, he identifies himself: “Kee-wee, kee-wee.”

We’re in New Zealand, and this nocturnal insectivore is a bird, one with nubbins for wings, catlike whiskers, soft feathers, and, unlike any other bird, nostrils on the tip of its beak. Many refer to it as an “honorary mammal.”

New Zealand is chockfull of unusual species. What is equally unusual, however, is what isn’t there: Mammals. There’s scarcely a patch of fur on the islands. Not counting the seals that haul out on New Zealand’s lovely beaches, the only native mammals are a trio of bat species, and even these are weird.

Islands provide a grand cookbook of evolution.

Halfway around the globe, Cuba has its own peculiarities. The owl that was as tall as a first-grader and that may have eaten juvenile giant ground sloths is sadly gone (as are the sloths, one species as big as a gorilla), but the island is still home to a hummingbird as small as a bumblebee; the solenodon, an archaic mammal straight off the pages of Dr. Seuss, with venomous saliva and a long, flexible, bewhiskered schnoz; and beagle-sized guinea pig look-alikes that climb trees and produce copious, banana-shaped, green poops.

Even tiny islands have their unusual curiosities. Lord Howe Island, a five-and-a-half-square-mile crescent lying in the Tasman Sea, is home to six-inch-long black “tree lobsters” that, moniker notwithstanding,