Faeces have a lot to teach us. They can reveal secrets about the lives of extinct animals, and the troubles of endangered ones. Eating dung can give animals a nutrient boost—while in the oceans, a deluge of plankton poo powers the entire carbon cycle.
Every year, New Zealand vessels drag trawl gear across nearly 100,000 square kilometres of our seafloor. We are the only nation still trawling on the high seas of the South Pacific. Can we make bottom trawling better? Or should we ban it altogether?
Some animals are ephemeral. Others are almost eternal. Some age gracefully, while others self-destruct. Why are some creatures here for a good time, and others for a long time?
If you sail west from California for nearly a week you’ll end up in the Great Pacific Garbage Patch. Then the plastic starts bobbing past—a buoy, a bucket, a net, a toothbrush, microplastics floating like bubbles—tens of thousands of tonnes of it spread over an estimated 1.6 million square kilometres.
One day in 2008, marine science student Kura Paul-Burke was diving in Ōhiwa’s murky waters when the grey-brown of the sea floor suddenly gave way to a brilliant orange. At first, she was struck by the beauty of it. Then she realised she was looking at hundreds of thousands of 11-armed sea stars—pātangaroa, a native species—stacked five or six layers deep. Behind them, the seabed was littered with empty green-lipped mussel shells. In 2007, the Bay of Plenty harbour was home to an estimated 112 million mussels. By 2019, only 78,000 were left. Paul-Burke’s Ngāti Awa elders had noticed signs of decline well before then. No-one knew why the mussels were dying. Was it overharvesting? Sedimentation? But they knew there used to be more mussel beds, and in 2006, they urged her to investigate—then helped her to map the old mussel beds using both traditional landmarks and scuba surveys. Researchers are still confirming the starfish are to blame, and figuring out what is causing the ecosystem imbalance in the harbour. In the meantime, Paul-Burke—now a professor of mātai moana (marine research) at the University of Waikato—wanted to see if it was possible to save the mussels and the harbour. The project wove together four iwi (Ngāti Awa, Te Ūpokorehe, Te Whakatōhea and Waimana Kaakū [Tūhoe]) and three councils, kaumātua and young people (pictured below, L-R: Megan Ranapia, Te Waikamihi Lambert and Cameron Phillips), mātauranga Māori and marine science. Together, they built four restoration stations where baby mussel spat could attach and grow. Instead of using commercial plastic spat lines, they experimented with natural fibres. The strongest were made from fallen tī kōuka leaves woven into rope by master weaver Rokahurihia Ngarimu-Cameron and her students. In late 2018, the team hung them on floats in midwater, out of the reach of clambering starfish. It worked. Mussels began growing in such numbers that they dragged the floats under the surface. When the tī kōuka lines eventually degraded, young mussels fell to the bottom “as a whānau”, Paul-Burke says, before reattaching to the sea floor. As the researchers describe in a new paper, by 2021, three new mussel beds had formed close to the restoration stations, and the mussel population had increased ten-fold—showing what can be accomplished, says Paul-Burke, when several knowledge streams and communities pull together.
Almost all animals sleep—insects, mammals, even jellyfish and sponges. Some of them even dream. But what is sleep for, and how has it shaped us?
At sea, the feasts are grand and impromptu—and everyone’s invited.
Sperm whales are tribal creatures—and they avoid interacting with those from other clans, even when they share the same waters. But how do they identify each other?
In New Zealand, if you see a tree turning red or golden in autumn, it’s almost certainly exotic. Out of more than 500 native species of woody flowering plants, just 10 lose their leaves in winter—most notably the tree fuchsia, kōtukutuku. But northern hemisphere forests at similar latitudes are full of deciduous trees, and in South America, close relatives of our southern beech trees drop their leaves each year. So why do Aotearoa’s temperate forests stay green, and was it always this way? Geologists examined a hundred fossil leaves from four sites in Otago dating back to the middle Miocene—around 11-16 million years ago—and found multiple lines of evidence that some of our extinct beech species were deciduous. The leaves of several deciduous Chilean beech species appear corrugated, with deeply etched veins, and the scientists found the same patterns in some of the Otago fossils. The leaves were also large, comparatively light for their size, and poorly defended, as evidenced by insect attacks—all trademarks of deciduous trees. (If you’re going to keep your leaves for just six months, it makes sense to make them cheap and disposable.) But here’s the paradox. Otago in the Miocene was much, much warmer than it is today. There were crocodiles and palm trees. If the winters weren’t frigid, why were those ancient beeches shrugging off their leaves every autumn? Lead author Tammo Reichgelt from the University of Connecticut theorises that deciduousness is less about temperature than light. Central Chilean summers are practically cloudless, while westerly winds make winters cloudy and wet. In New Zealand, cloud cover is relatively constant through the year. In Miocene Otago, as in Chile, the beeches soaked up the abundant summer sunshine—“it was really worth it to photosynthesise a lot”, says Reichgelt—but there was little point to keeping green during the dark, wet winter. Then, at the end of the Miocene, the planet cooled dramatically. Zealandia got wetter, its seasons less pronounced. “It wasn’t worth it anymore to throw away your carbon in autumn,” says Reichgelt—so all our deciduous beeches disappeared.
Penguins traded in their wings for flippers more than 60 million years ago, long before there were icesheets in Antarctica. But aeons of evolution turned them into supremely adapted marine hunters, capable of diving deep and withstanding extreme cold.
The invasive seaweed Caulerpa brachypus was discovered in New Zealand just over a year ago, and it promises to ruin everything. On Aotea/Great Barrier Island, people are sacrificing their way of life in an attempt to contain the weed—and stop it reaching the mainland.
What does birdsong mean? Do other animals also sing? Or is song a uniquely human invention?
Sharks and rays are considered to be strong, silent types—they possess no voice boxes, or other anatomical structures associated with vocal communication. Or so we thought. Then Spanish photographer J. Javier Delgado Esteban filmed a juvenile mangrove whipray (Urogymnus granulatus) while he was snorkelling off Magnetic Island on Australia’s Great Barrier Reef. When Esteban approached, the ray made loud clicks. Each sound visibly coincided with a contraction of its spiracles—openings behind the eyes that rays use to aid breathing. Marine ecologist Lachlan Fetterplace saw the video on Instagram, contacted Esteban, and started investigating. They assembled anecdotal reports and two other recent videos from Australia and Indonesia showing an adult whipray and a cowtail stingray (Pastinachus ater) making similar tok-tok sounds. “These are widespread species, found off the coast in highly populated areas,” says Fetterplace. Yet researchers hadn’t noticed the sounds at all. Many mysteries remain: how the rays are making the clicks, exactly what they’re using them for, and how many other rays and sharks may also be capable of sound. “Is it a really widespread thing that they rarely do, or is it something that’s commonly done, but only in a few species?” says Fetterplace. He’s now questioning what else we might have missed—simply because we weren’t looking for it.
A study by the Pacific Islands Forum Fisheries Agency of illegal, unreported and unregulated tuna fishing has found that the problem may not be as bad as was feared. It estimated that between 2017 and 2019, 192,000 tonnes of tuna worth more than US$300 million was caught each year in the Pacific Islands region by people not following fisheries rules—down from 300,000 tonnes in the 2016 estimate. “The assumption that unlicensed fishing is rampant has been proven false,” says Auckland-based fisheries consultant Francisco Blaha, who contributed to the report. Only five percent of the dodgy dealings involved unlicensed fishing boats. Most—89 per cent—involved licensed operators misreporting which fish they caught, or how many.
Blue sharks swim in all the world’s oceans, and a new study reveals surprising stories about their migrations and behaviour. For his doctoral research at the University of Auckland, Riley Elliott carefully attached satellite tags to 15 blue sharks—11 males and four females—in the waters off northeastern New Zealand between 2012 and 2015. With limited funding available for the expensive tags, Elliott turned to community groups and individuals, the sponsors following the animals’ movements online. In some cases, the tag stayed attached for at least a year. One shark travelled more than 14,000 kilometres from New Zealand to the Pacific Islands and Indonesia and back. Another dived to more than 1364 metres below the surface—a record at the time for blue sharks—and a third swam all the way to the equator. “We were all kind of cheering for him,” says Elliott. “The scientific theory is they don’t cross the equator.” One kilometre from the line, as though the shark had sensed it, he turned and swam south. “Unfortunately, he went through a real hotspot of tuna fishing, and we stopped hearing from him.” These long-distance travellers were all males. The tagged females remained in and around New Zealand waters all year round—a surprise, given fisheries data had suggested there were few mature females here. In a shark fairy tale, Elliott tagged a male and a female off Aotea/Great Barrier Island in 2014. The female had fresh mating scars (shark romance is not gentle), and there were young pups close by. In late summer, the male swam north to the tropics, while the female stayed around Northland. The following spring, they reunited—returning to the same spot near Aotea at the same time. Blue sharks are declining almost everywhere, as they’re caught more often than any other shark in longline fisheries. In 2019, surface longline fishers in New Zealand caught almost as many blue sharks as they did southern bluefin, the species they were actually targeting. About three-quarters of the sharks caught were killed and processed for their fins or meat.
The steep underwater walls of Fiordland’s sounds are home to a lush ecosystem of sponges, corals, and algae in camouflage shades of green and brown. Last summer, divers in Te Puaitaha/Breaksea Sound working to control the spread of the invasive seaweed Undaria noticed something unusual: the Cymbastela lamellata sponges dotted all over the cliffs were bleached a bright white. “Once you see one, you just see them everywhere—as far as you can see,” says diver Millie Mannering. It’s the first time sponge bleaching has been observed in New Zealand, affecting millions or even tens of millions of individual animals. It’s likely the result of last summer’s marine heatwave, when ocean temperatures in Fiordland reached up to five degrees warmer than usual. By chance, sponge ecologists Francesca Strano and Valerio Micaroni from Victoria University of Wellington, who study the effects of climate change on sponges, were also on the trip, and were horrified by what they saw. “We were really worried they would all die,” says Strano. But when the pair returned to Fiordland in June to assess the damage, they found that most of the bleached sponges were still alive—even though the symbiotic green algae that live inside them were mostly gone. These algae give the sponges their colour and supply them with extra food. But there were enough algae remaining that the scientists are hopeful that the cooler waters over winter may allow them to regrow, and the sponges to recover.
Dan Burgin was holding the flesh-footed shearwater chick when it vomited a hard white square of plastic—and stinky stomach oil—over Simon Lamb. The two ecologists, from the consultancy Wildlife Management International, were on predator-free Ohinau Island, off the eastern side of the Coromandel Peninsula, collecting data on the shearwater breeding season. They couldn’t help noticing the plastic scattered around the seabird colonies, especially near the shearwaters’ burrows. The rubbish wasn’t jettisoned by humans—Ohinau Island requires a permit to visit—but by the birds themselves. Seabirds perform a vital ecosystem role of bringing nutrients from the ocean to the land. Now, they’re transporting plastic, too. They’re even feeding it to their young. Burgin and Lamb autopsied 11 flesh-footed shearwater chicks they found dead in their burrows or on the ground, and found that they all had plastic in their stomachs. In one decomposing chick, they discovered 114 miscellaneous particles weighing 35 grams: five per cent of the body weight of a chick roughly the size of seagull, or the equivalent of a human swallowing three kilograms of the stuff. “To see plastics having such a tangible impact on this species was very hard-hitting,” says Burgin. “I had a very heavy heart coming off that trip.” Because of the complexity of ocean currents, the plastic could be coming from both local and international sources, he says. “The problem is probably more acute than we’re aware of.”
Electric eels are living batteries that taser their prey with 860-volt jolts. Sharks use electricity like an extra sense to see fish and sneak up on them. Spiders fly using the atmosphere’s electric charge, and bumblebees and flowers communicate through their personal electric fields. How else does the natural world use electricity?
This past summer was a scorcher, not just on land but in the sea, too. In some of New Zealand’s coastal waters, temperatures reached four degrees higher than normal, while in the Bay of Plenty, a marine heatwave began in November and continued into March. Globally, marine heatwaves have bleached coral, flattened kelp forests, changed whales’ behaviour, wiped out fisheries, and allowed invasive species to spread. They can also cause problems for aquaculture, says MetOcean’s João de Souza, director of The Moana Project, which tracks ocean temperatures around New Zealand and forecasts marine heatwaves one week ahead to help companies farming salmon, mussel and oysters to prepare. (A marine heatwave takes place when temperatures reach a certain level above baseline averages for at least five days in a row.) The abnormally toasty conditions were already evident last winter and intensified over summer, de Souza says, the result of both atmospheric and marine conditions working together. Worldwide, the ocean’s average temperature has increased by nearly 1°C in the past century. On top of that, “the Southern Blob”—an Australia-sized patch of overheated water to the east of New Zealand—has lifted sea temperatures even higher for at least the past decade. This summer, the warm air and clear skies brought by La Niña contributed too, making it New Zealand’s most extreme marine heatwave since records began in 1981. The problem is, once-rare events are becoming normal, says Kisei Tanaka from the US National Oceanic and Atmospheric Administration in Hawaii. “What we once considered extreme is not extreme anymore—because it’s happening every year.” In a recent study, Tanaka and his colleagues used two 150-year datasets tracking sea-surface temperatures worldwide. In each place, they identified the hottest month between 1870 and 1919—a once-in-50-year heatwave. By 2014, more than half of the ocean’s surface was hitting or exceeding that threshold. Tanaka’s study showed that in New Zealand, too, marine heat events have significantly increased in frequency since the 1980s. Between 2010 and 2019, more than half of the country’s exclusive economic zone exceeded the historical ‘once-in-50-years’ temperatures during at least six months of every year. For Tanaka, it’s a stark reminder that climate change is not just “waiting for us on the horizon”, he says. “It’s happening now, as we speak, and it has been happening for quite some time.”
Where do Tamatea/Dusky Sound’s dolphins go? Starting in 2009, researchers spent a decade trying to find out, setting out 178 times in small boats in all seasons to track and identify the sound’s resident bottlenose dolphins—around 120 of them. They found that the animals preferred to hang out in certain parts of the vast waterway, and that they particularly liked Te Puaitaha/Breaksea Sound (the long fiord at the north end of Dusky Sound) and the Bowen Channel (between Resolution and Long Islands). However, from 2016 to 2018, the dolphins began to leave Breaksea Sound. Fiordland may be one of the wildest places in New Zealand, but human presence is increasing. The researchers suspect that increased boat traffic, the depletion of blue cod by recreational fishers, or the spread of the invasive weed undaria in Breaksea Sound could have something to do with the change. As large predators, bottlenose dolphins are a critical part of the Fiordland marine ecosystem. Nearby Doubtful Sound/Patea and Milford Sound/Piopiotahi have special safeguards in place for dolphins, but not Dusky. The researchers suggest a number of options to protect them: extend the boundaries of existing marine reserves to include dolphin hotspots, restrict vessel traffic in those areas, and lower recreation catch limits within the entire sound. These ecosystem-based approaches would be more effective than another suggestion, the creation of a marine mammal sanctuary, says the University of Auckland’s Rochelle Constantine, who was not involved in the paper. “It’s better to look after the whole area so all the marine life is taken into consideration.”
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