Living World | Subject area | New Zealand Geographic

Building blocks

The wombat is the only species in the world capable of organically producing cubes. Thanks to the varying elasticity of its intestinal walls, wombats poop cubes, which they then stack up to mark their territory and attract the attention of other wombats. How they produce droppings in this shape has long been a biological mystery, solved only when Patricia Yang, a postdoctoral fellow in mechanical engineering at Georgia Institute of Technology, studied the digestive tracts of roadkill wombats from Tasmania. Cubes are rare in the natural world. “We currently have only two methods to manufacture cubes: We mold it, or we cut it. Now we have this third method,” said Yang in a presentation of her research. “It would be a cool method to apply to the manufacturing process—how to make a cube with soft tissue instead of just molding it.”

Geo News

Noise ages birds faster

Zebra finches exposed to the sound of traffic appear to age faster than those in quieter environments. In a study published in Frontiers in Zoology, birds were found to have shortened telomeres, which indicates accelerated ageing, if they were played recordings of street traffic once they had left the nest. The birds heard the noise from the age of 18 days until 120 days. But if birds were exposed to noises only while in the nest, their telomeres were of normal length. The authors suggest the birds are more sensitive to noise between 18 and 120 days of life—the time when they are learning song.

Geo News

The gannet diet

The Australasian gannet forages by plucking fish from the sea, then regurgitates food for its young—and sometimes its meals are interrupted by researchers studying gannet nutrition. A team of Australian and New Zealand scientists took a close look at what the gannets were providing their chicks. They found that the fish and squid they were eating had a lower ratio of healthy fats to protein when the sea was warmer than the 10-year average. In addition, GPS trackers showed the birds worked harder to get enough nutrition, increasing their foraging area by more than 200 square kilometres and their time spent feeding from more than 13 hours in duration to more than 21 hours. Study author Gabriel Machovsky-Capuska says the right proportion of healthy fats to proteins is crucial to gannets for good body function and healthy chicks.

Features

Tending the flock

New Zealand has only one endemic gull, the tarāpuka, and it’s more endangered than the takahē, the hoiho and all five species of kiwi. Its survival depends on the preservation of the South Island’s unique braided-river ecosystems.

Geo News

The long life of tortoises

Lonesome George was the last of his species, a Galápagos giant tortoise from the island of Pinta. Though he died in 2012, he continues to inform scientific research—his genome was sequenced and more than 3000 genes thought to be involved in ageing and cancer were analysed by an international team of researchers. Galápagos giant tortoises are among the longest-lived species, reaching up to 200 years, and it’s thought they have evolved mechanisms for preventing cancer. The researchers identified variants in several genes previously unassociated with ageing, opening up avenues for further research.

Geo News

Dolphin fingerprints

Ninety-five per cent of common dolphins have a unique ‘fingerprint’ of pigmentation on their dorsal fin that lasts a lifetime. Scientists hope machine learning could use the dolphin photographs taken by people all around New Zealand to track where the dolphins travel. Common dolphins occur around the globe, and it was thought they were too numerous and similar to tell individuals apart—there are thousands that swim in the Hauraki Gulf alone. Currently, dolphins are told apart by the nicks and notches on their dorsal fins—scars received socially or from boats or fishing lines. These accumulate over a dolphin’s lifetime. Bottlenose dolphins are very social and may acquire many scars, but 50 per cent of common dolphins have no scars at all. Scientists from Massey University and NIWA used 240,000 photos of nicks and notches to manually identify 2083 individuals in the Hauraki Gulf. Then they demonstrated that over ten years, the pigmentation on common dolphins’ dorsal fins doesn’t change, making it a reliable mark of identity. Lead researcher Krista Hupman is now developing an algorithm that will identify dolphins, and hopes that photos of individuals taken by recreational boaties and tourism operators could be used to get a better understanding of how many dolphins there are, where they go, and how they behave.

Virtual Reality / 360 Video - NZ 360

Snapper - Goat Island

Snapper congregate in the shallows of Cape Rodney-Okakari Point Marine Reserve at an abundance and maturity that may closely reflect the original snapper populations of the Hauraki Gulf. There are three to four times the number of snapper inside the reserve as outside and up to ten times the number of crayfish.

Virtual Reality / 360 Video - NZ 360

Kina barren -Three Kings

Fishing effort, day after day, century after century, has changed the shape of this place. It’s still heaving with reef fish, but the predators are gone. It’s still resplendent with sargassum weed, but kina that were once devoured by snapper and other reef predators are tearing holes through the fabric of the ecosystem.

Virtual Reality / 360 Video - NZ 360

Stingray - Northern Arch

Northern Arch is a 40-metre-deep cut in a sheer rock wall at the northern end of the Poor Knights. Like a busy city alley it attracts hoards of life—thousands of fish,

Virtual Reality / 360 Video - New Zealand Journeys

Tie Dye Arch - The Pinnacles

South of the Poor Knights stand a crop of rocky spires called The Pinnacles. Under the largest is a cathedral-like cavern called Tie Dye Arch, named for the kaleidoscope of colours that clad every surface like graffiti.

Geo News

The biggest bird brain

Birds that evolved on islands, such as the North and South Island, tend to have bigger brains than those that evolved on large continents, even if the species are close cousins. A study published in Nature Communications in July compared brain size relative to body size in more than 1900 bird species, spanning 91 per cent of bird families. The researchers then analysed several bird lineages that had relatives on both islands and continents. Having a large volume in some areas of the brain enables adaptability—the pallial regions, for instance, help with pattern-finding and planning. Because island environments are unpredictable, say the authors, adaptive capability is a significant advantage. “For instance, the Galápagos finch uses tools, instead of the more frequent gleaning technique, when there are droughts and insects are only found in wood crevices,” says lead author Ferran Sayol. The New Zealand tomtit, Petroica macrocephala, has a much larger brain than its closest mainland relative, and the kea has an unusually large brain for a parrot.

Geo News

Aerial roots

If a root is above ground, how can it take in water? The Lord Howe pandan has evolved a solution: it has developed grooves that function like aqueducts, according to Victoria University researcher Matt Biddick. Pandans are found on tropical and subtropical coasts around the Pacific. They have weak trunks, but grow tall by sending roots down from the canopy that form stilts when they reach the ground. Most pandans grow to less than five metres high, but a Lord Howe Island species, Pandanus forsteri, grows to more than 15 metres, so it takes years for the aerial roots to reach the ground. Without being able to draw moisture from the earth, the roots gather it by other means. The leaves of P. forsteri are shaped like gutters, and funnel water toward the trunk. Then, grooves on the top surface of the roots channel the water to the roots’ tips, where spongy absorptive tissue carries the collected rainwater to the rest of the plant.

Geo News

Why did the penguin swim to the subantarctic?

Tawaki, or Fiordland crested penguins, have plenty of food along the coastline where they breed, yet every year they make a trip to the Subtropical and Subantarctic Fronts and back to feed—a swim of nearly 7000 kilometres. “One would think that the birds try and conserve as much energy on this trip as possible,” says researcher Thomas Mattern from the University of Otago. “But what we found is, simply put, crazy.” In 2016, Mattern and his team put GPS trackers on 17 adult tawaki and watched them travel from their rainforest colony to the subantarctic, an eight-week trip during November and December—a time when the availability of food on the Fiordland coastline is at its peak. The birds must gain weight during the journey because they undergo a ‘catastrophic moult’ immediately following their return, shedding and replacing their entire plumage at once, which requires them to stay on land for three weeks without going out to sea to feed. Mattern thinks this trip is undertaken by instinct—an impulse left over from ancestors that bred on islands close to the Subantarctic Front. Most other crested penguins still breed on those islands.

Geo News

Fatal memory fail

It took just 13 generations for quolls to forget about their major predator, the dingo, according to Australian research published in Biology Letters in June. After noticing that northern quolls were eating toxic cane toads, with lethal results, researchers moved a group of quolls to a toad-free, dingo-free island in 2003. The quolls were trained to avoid cane toads and reintroduced to their native territory in 2016, where they were promptly eaten by dingoes. They had forgotten how to identify and avoid the dingoes’ scent.

Geo News

How rats shape coral reefs

When rats consume the eggs and chicks of coastal-nesting seabirds, this affects fish and coral reefs offshore, according to a letter published in Nature in July. If birds are killed, this prevents their droppings from reaching marine ecosystems, meaning that underwater species miss out on the boost of nutrients provided by this natural fertiliser. The Chagos Archipelago in the Indian Ocean, south of the Maldives, is an ideal place to study the effects of rat populations—18 of its 55 islands are rat-free, while rats have been in residence on the others for centuries. An international team of researchers found seabird densities were 760 times higher on rat-free islands, which also had 251 times more nitrogen deposited from seabird droppings. Tracking nitrogen isotopes on the coral reefs around the islands, the scientists found nitrogen from birds present in seaweed, sponges and turf algae. They observed that herbivorous damselfish grew faster, and fish communities in general had 48 per cent more biomass, compared to the rat-covered islands next door. This suggests rat eradications could alleviate pressure from climate-stressed coral reefs.

Geo News

The brand-new seabird of Whenua Hou

Whenua Hou, a tiny island off the coast of Stewart Island, is most famous for its population of kākāpō, but it also has a one-kilometre strip of beach where diving petrels breed. These have just been identified as a unique species, the Whenua Hou diving petrel, Pelecanoides whenuahouensis. While there are 15 million diving petrels around the world, Johannes Fischer of Victoria University in Wellington concluded that this tiny colony was a different species for a variety of reasons: their feather colours, DNA, deeper bills, longer heads, and different species of feather lice. They’re also the only diving petrel to breed entirely within a sand-dune environment. The species numbers about 150 birds, making it critically endangered. Its entire population nests in this fragile, changeable place.

Features

Photographing the bizarre night life of the ocean

By night, a menagerie of species rises to the surface of the ocean—rarely glimpsed, and in some cases never photographed.

Geo News

The ferocious plant that went rogue

First introduced in the 1870s for hedges, African boxthorn soon went rogue. It thrives in coastal areas, as it can handle dry, salty, sandy, windy, hot and cold conditions. Up to six metres tall, it crowds out other plants with its 13-millimetre spines. Thorns can get stuck in cattle hooves, pierce gumboots, and puncture tyres. ‘Lycium’ means ‘thorny shrub’ and ‘ferrocissimum’ means ‘ferocious’. Seabirds can get tangled up in clumps of boxthorn as they land or take off, and quickly die of starvation and exposure. The Department of Conservation is battling boxthorn on the predator-free island Motunau, a place teeming with seabird burrows. In Taranaki, boxthorn was once in demand. Seeds and seedlings were sold by nurseries and locals, and sheep-proof hedges were planted. Boxthorn honey and boxthorn jam were popular, and boxthorn wood was good firewood. Now, hedges are more likely to be bulldozed and burned.

Geo News

How long can penguins hold their breath?

A new record has been set for the longest dive by an emperor penguin. In a study led by NIWA marine ecologist Kim Goetz during the penguin breeding season, 20 birds that hadn’t paired up were tagged and tracked in the eastern Ross Sea. These birds dived 96,000 times over six months, and while most dives were around the five-minute mark, one lasted a record-breaking 32.2 minutes. (Previously, the longest dive was 27.6 minutes.) Penguins dive in order to catch fish, krill and squid, and the study found they dived deeper and longer during the day and at twilight, consistent with using eyesight to hunt.

Geo News

When plants avoid their neighbours

Plants are social beings. When leaves from different plants touch each other, their roots send out signals, telling the other plant to get lost. New research from the Swedish University of Agricultural Sciences, published in PLOS One in May, found that maize seedlings whose leaves were touched give off chemicals via their roots, which cause non-touched maize seedlings to grow away from them. Study co-author Velemir Ninkovic says the chemicals signal a crowded environment, so other plants choose environments with less competition and therefore more resources. Later on, seedlings exposed to these root chemicals also grow more leaves—a typical plant response to avoid being left in the shade.

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