Mad about Science: Kiwi

By Brenden Bobby
Reader Columnist

We’re ringing in the new year with an ambitious experiment! In a Mad About Science first, we’re going to be learning about two completely different subjects under a single umbrella, and it will be up to you, dear reader, to figure out which one you’re learning about at any given moment: the bird or the fruit.

Kiwi is a Maori word used to describe the ratites, or flightless birds without a keel bone, endemic to the islands of New Zealand. It has also grown to describe a fuzzy-skinned fruit native to China that has made its way to the islands. It also is a term used to describe the people of New Zealand, all calling back to the strange chicken-sized bird.

What do kiwi and moose have in common? They’re both brown and they’re both irregular plurals. That means that if you see two moose or two kiwi, you refer to them identically as though you’ve seen only one. Sorry transplants, but multiple moose aren’t mooses or meese. As the word kiwi is of Maori origin, this applies to any form of kiwi, whether you’re talking about the bird, the fruit or the people.

There are five species of kiwi: the brown kiwi, the great spotted kiwi, the little spotted kiwi, the rowi and the tokoeka. The great spotted kiwi is the largest of the bunch with a maximum standing height of about 18 inches and weight up to six pounds, comparable to a large chicken. The little spotted kiwi is the complete inversion and is much closer to a bantam with a maximum height of around 10 inches. There are likely fewer than 100,000 total kiwi left in the world between all five species, as many have been pushed out by invasive mammals such as hogs and cats.

Kiwi are flightless birds that are related to ostriches and cassowary. They are the smallest of ratites and surrounded by a host of genetic curiosities. Despite having shared an island with the extinct moa bird — another and much larger ratite — kiwi are more closely related to the extinct elephant bird of Madagascar. You may be left wondering how two flightless birds separated by more than 7,000 miles of ocean may be more closely related than two birds that shared an island.

The last common ancestor between the elephant bird and kiwi was likely at least 180 million years ago during the break up of the continent of Gondwana. Despite millions of years of genetic distance and completely different island environments, these animals evolved into remarkably similar forms through something called convergent evolution, which we’ve explored before. The environment in which the elephant bird’s ancestors and the kiwi’s ancestors lived was similar enough in their requirements that the two lifeforms evolved into relatively similar flightless birds with no need for wings. Interestingly, these two deviated dramatically when it came to their size, as elephant birds could reach a height of nearly 10 feet and laid the largest eggs of any bird that we’ve found. Kiwi lay eggs that are proportionally huge for their body type, plopping out an egg nearly a quarter of their size once a year.

Unlike most other birds, kiwi chicks are curiously born completely feathered, though they do retain the yolk sac for up to 10 days after hatching and are capable of foraging on their own. This is in stark contrast to something like a baby chick, which requires thermal regulation from a hen’s feathers or a heat lamp to avoid freezing to death for the first several weeks of its life.

Kiwi are edible, and it’s likely that you can find two types of edible kiwi at the grocery store. The green Hayward kiwi and the SunGold kiwi are both commonly found in grocery stores. Despite having a fuzzy brown rind that I personally find unpalatable, the skin is completely edible. Slicing the kiwi up into rings and sprinkling it with sugar makes for a tasty treat.

The green flesh of the kiwi is rich in vitamin C, with each kiwi packing nearly triple the vitamin C to an orange. Interestingly, kiwi has some molecular compounds that mimic latex, so people who have latex allergies may also be allergic to kiwi.

Kiwi are nutrient-dense and high in fiber while also remaining low in calories. They tend to preserve for longer than other food due to the fuzzy brown rind that keeps bacteria and insects out. Despite preserving fairly well in comparison to something like lettuce, keeping them in the refrigerator can help preserve your kiwi for longer periods of time.

Despite its name and similar appearance to the flightless bird, kiwi fruit originated in China and was only imported into New Zealand in the 1900s. Its former name was Chinese gooseberry, but the term kiwi was found more attractive to wider audiences.

A final bit of kiwi trivia is that the fruit contains enzymes that help it tenderize meat, making it a great addition to tropical marinades. The fruit ripens in the Northern Hemisphere between October and November, while it ripens between April and September in places like New Zealand and Australia — often, American demand for Kiwi is highest during the summer months due to its light tropical flavors that pair well with melon and strawberries.

Stay curious, 7B.