Living World | Subject area | New Zealand Geographic

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.

Geo News

The krill effect

A one-centimetre-long shrimp can’t create an ocean current when it swims, but en masse, these tiny creatures could be contributing to ocean mixing. A Stanford University study published in Nature watched brine shrimp, Artemia salina, as they swam in a tank. When they swim upwards, as a band just 50 centimetres deep, their wake mixes the water 1000 times more than it would mix naturally. Ocean krill are five times the length of brine shrimp, and twice a day they vertically swim hundreds of metres as a group in a band tens of metres deep—which the authors say means the krills’ downward jets could have a collective effect on ocean mixing.

Geo News

Shining a light on Zika

An old tool that has been used for decades to determine which chemicals are in foods, the human body and pharmaceuticals could now be used to see if a mosquito is carrying the Zika virus. The microcephaly-causing virus has spread by mosquito into many new countries in recent years, including Fiji, Samoa and Tonga. A major challenge in monitoring the situation has been the lack of fast, affordable tests. Currently, genetic material is analysed for the virus using the reverse transcription polymerase chain reaction (RT-qPCR). But a study published in Science Advances has found that near-infrared spectroscopy (NIRS) predicts Zika with between 94.2 and 99.3 per cent accuracy. NIRS simply involves shining a light at the head and thorax of the mosquito to read the chemical compounds within. It’s 18 times faster and 116 times cheaper than RT-qPCR, with no need for dissections or reagents.

Fact File

Ribbon halfbeak

Euleptorhamphus viridis

On Reflection

Good grief

What we can learn from albatrosses.

Features

The first test

If we’re serious about Predator Free 2050—about ridding New Zealand of every last rat, stoat and possum—then Fiordland poses its sternest backcountry test. If we can pull it off here, we can pull it off in any of our national parks. What makes this land so difficult—and so important?

Documentary - Our Big Blue Backyard

Stewart Island

Little Blue Penguins run the gauntlet to escape Great White Sharks – but they’re not the only species flirting with death on New Zealand’s famous Stewart Island.

Documentary - Our Big Blue Backyard

Open Bay Islands

On New Zealand’s remote Open Bay Islands, New Zealand fur seals protect their newborns from surging seas, starvation, and predation by Great White Sharks.

Documentary - Our Big Blue Backyard

Kaikoura

New Zealand’s Kaikoura peninsula is home to the world’s most acrobatic dolphin species, some of New Zealand’s most robust young Fur Seals, and an unconventional group of Red-Billed Gull families who defend their chicks from dangers both within and outside the colony

Documentary - Our Big Blue Backyard

Poor Knights Islands

New Zealand’s Poor Knights Islands is considered one of the world’s top dive sites and for good reason, with a rich collection of extraordinary characters and bizarre behaviors, including a unique congregation of stingrays and sex-changing Sandagers Wrasse.

Documentary - Our Big Blue Backyard

Goat Island

The creatures of New Zealand’s oldest marine reserve are safe from humans, but that doesn’t mean life is easy. They are under constant attack from marauding dolphins, diving cormorants, and the sharks and the marlin that live beyond the boundaries of the reserve.

Documentary - Our Big Blue Backyard

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