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Revisiting tōhora

A year of wandering the southern oceans, following ancient migration routes in search of food—that’s the tantalising glimpse of whale life that a tohorā/southern right whale nicknamed Bill has given University of Auckland researchers. Thanks to a satellite tag deployed by a team led by Emma Carroll in 2020, Bill has now provided the longest record of tohorā migration ever captured. Usually, satellite tags stop working after around six months. Bill’s tag, however, is still transmitting more than a year later. Bill left the Auckland Islands in August 2020 and travelled thousands of kilometres into waters south of western Australia, before moving far off into the Indian Ocean, almost halfway to Africa. Then, he turned south and swam thousands more kilometres to the Antarctic ice edge. Over several months, he worked his way back along the edge of the pack ice, finally returning to the Auckland Islands in June, having traveled well over 15,000 kilometres. Another tagged whale, Tahi, also travelled far into the Indian Ocean before returning to the Auckland Islands. “We had no idea that they were going so far west,” says Carroll. “Bill and Tahi went a third of the way around the world and back. That’s unprecedented. [caption id="attachment_432915" align="alignnone" width="600"] Photographer Richard Robinson floats above the seafloor holding a VR camera, waiting. The 80-tonne whales, curious and confident, are ideal subjects—approaching slowly, orbiting gracefully and drifting away when they’re satisfied they’ve got to know you.[/caption] “It’s showing that these whales are using far more of the ocean than we thought. Which is great, because if one area isn’t that productive, but the other is, they’re still getting a lot of kai. It suggests the population has resilience.” Carroll and her team have just returned from the Auckland Islands, where they deployed another 11 satellite tags. “We want to be able to match their satellite tracks against currents, productivity, marine heatwaves, and all kinds of things. At the moment, we can see what they’re doing, but we need more data to understand why they’re doing what they’re doing.” As for Bill, well, at the time of writing, he is still transmitting—currently halfway back to western Australia, off on another lap of his extraordinary life. His progress, and that of this years’ tagged whales, can be seen at tohoravoyages.ac.nz
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Where do shags come from?

Reconstructing the family tree of New Zealand’s blue-eyed shags has enabled scientists to unravel their past—and may help determine their future. The blue-eyed shag family includes bird species from all around the country: the rare king shag from the Marlborough Sounds, the Otago shag, the Foveaux shag, the extinct (but recently discovered) kōhatu shag from Northland, and species on the Chatham, Auckland, Campbell and Bounty islands, plus more-distant relatives on other subantarctic islands and in South America. Nic Rawlence from the University of Otago set out to track the evolution of the entire group, and his team’s genetic research revealed the birds evolved in South America. This is unusual for New Zealand birds, which most often arrive from Australia on the westerly winds. Blue-eyed shags were probably blown off course into the Southern Ocean and island-hopped around the subantarctic before arriving here around 2.5 million years ago and rapidly diversifying. That there are so many different species here is because of a paradoxical personality trait of blue-eyed shags. Though shags are obviously prone to accidental oceanic travel, once they find somewhere they like, they don’t stray far from home. That meant each small population was isolated from the rest and evolved independently. Then the ice ages struck, and Antarctic sea ice expanded all the way up to the more southerly subantarctic islands, spelling the end for the blue-eyed shags living there (the birds feed in shallow waters near their colonies, and when those froze over, they would have starved). When the ice retreated during a warmer period, blue-eyed shags recolonised the Southern Ocean from South America—but that later wave of migrants couldn’t get a foothold in New Zealand, as shags on the mainland had survived. “There were already blue-eyed shags that were happy, that were filling the job vacancy for blue-eyed shag,” says Rawlence. Genetic evidence confirms what biologists already knew about the family: “They are very, very prone to disturbance,” says Rawlence. “Whether that is human disturbance, polluting the oceans, or overfishing.” That makes them sentinels for the health of the Southern Ocean. “Working out how they evolved and how they’ve responded to past climate change can help us think about how they will respond into the future.”
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Plant colony

You can buy a staghorn fern at any garden centre and grow it like a pot plant. But in the wild, the ferns grow in a way that’s changing our understanding of biological complexity. Latched onto branches of rainforest trees, staghorn ferns (Platycerium bifurcatum) evolved to live in colonies on Lord Howe Island off Australia’s east coast, with individual ferns fitted like puzzle pieces and working together to collect water for the benefit of all colony members. The level of job division is such that about 40 per cent of individuals forgo reproduction. Social colonies, with strict division of labour and reproduction, are nothing new in the animal kingdom, says Victoria University of Wellington biologist Kevin Burns. Social insects—bees, ants, termites and some wasps—are the best-known examples of colony-building behaviour, but it has also evolved independently in crustaceans (certain species of shrimp) and even mammals (naked mole rats). But Burns’ research describes the first time it’s been observed in plants. Colony-building behaviour, or eusociality, is the most recent of eight major evolutionary transitions to more complex life. Burns says eusociality is defined by colonies that include several generations of adults, and dividing labour and care for offspring co-operatively. Staghorn ferns may not fit the strictest definition, and are unlikely to have rigid job division like termites. “I suspect they go through a succession, starting off being a reproducer, then maybe a collector, and they shift as the colony develops,” he says. But the important point is that colony life is not restricted to animals. “Plants can walk that evolutionary path in the same way, without a brain—and that’s a huge leap forward.”
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Seabird oddity

Tubenose seabirds—albatrosses, petrels, shearwaters and storm petrels—pretty much always follow the rules. Breed in the summer, when there’s more kai to catch. Mix up the length of foraging trips when feeding a chick: a few short foraging sessions for every long-distance feed. Mum and Dad pick different fishing spots and strategies, diversifying their options. Westland petrels break all the rules. They breed in the winter. Their foraging trips are always the same length—short, even though their wing structure means they’re capable of longer flights. And both parents fish in the same old spot. (Only 12 tubenose species are known to adopt these non-conformist habits.) To understand why and how Westland petrels successfully raise chicks with such an unusual approach, researchers tracked their movements using GPS loggers and accelerometers. The international team, including scientists from Te Papa, found that the Westland petrels were fishing around 150 kilometres off the coast, where the continental shelf slopes into submarine canyons: a reliable, local prey field that shapes their behaviour. Fishing peaks during the first few hours of darkness, suggesting that the petrels target bioluminescent fish and squid species that migrate daily up and down the water column. Westland petrels are endangered, and the small size of their foraging range—which coincides with a hoki trawl fishery—could pose problems in a food shortage, while their nesting burrows in the hills have previously been threatened by human development.
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Kiwi need more bugs

For many kiwi, there’s little chance of survival unless a ranger plucks them from the wild while they’re still in the egg. These birds hatch and grow up in captivity, then are returned home once they’re big enough to fight off stoats and rats. This system has saved the lives of hundreds of kiwi, but may have some unintended consequences: the microbes in the gut of kiwi raised in captivity are very different from those of birds which hatched in the wild. Kiwi chicks hatch ready to forage, says Manaaki Whenua microbial ecologist Manpreet Dhami. “From the very beginning they are digging around in the soil and foliage, looking for food and thus acquiring their first microbes.” Captive kiwi, on the other hand, are fed a mix of ox heart, cat biscuits and rolled oats—food that is “nutritionally appropriate but microbially a far cry from their natural diet”. If a bird catches an infection, it’s treated with antibiotics and then given probiotics to help restore its microbiome. Dhami and her team analysed faeces from wild birds and kiwi hatcheries, and found the microbiomes of wild birds were more similar to each other than those of captive birds—even when the wild kiwi were from different locations. The wild microbiome includes bacteria that may have a protective role against illness or help with food digestion, while the captive kiwi microbiome is simpler and less diverse. Studies on other birds—parrots, chickens and ostriches—have found a connection between less diverse microbiomes and a higher risk of disease. “As more and more birds go through the captive rearing process, we are creating a population of birds that are lacking that exposure to microbial diversity, and perhaps undercutting the development of natural defences,” says Dhami. Captive rearing is essential to the survival not just of kiwi but many other threatened birds, kākāpō and takahē among them. The team is now working on a new diet for captive kiwi—one that’s more natural and has more bacteria.
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Singing test

Do forests fall silent after a drop of the poison 1080? Scientists recorded birdsong in the Wairarapa’s Aorangi Range before and after 1080 operations in 2014 and 2017, as well as in the Northern Remutaka Ranges, which didn’t receive the poison. (1080 is intended to kill possums.) Analysing the hundreds of recordings, researchers from Victoria University of Wellington found birdsong levels were the same, or higher, in areas treated with 1080, compared to untreated areas of forest. The majority of birds were judged to be unaffected by 1080 on the basis of their calls, but two species were heard from less following the drops: chaffinches and tomtits. The researchers believe chaffinches, an introduced species, may have consumed 1080—the birds normally eat grain—and say further research is needed about how native tomtits may be affected by the poison.
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Bored or hungry

Can you stop a cat from hunting? University of Exeter researchers tested whether improving a cat’s nutrition or exercise reduced its number of kills. Over three months, the researchers trialled different options on 219 households involving 355 cats in southwest England, focusing on interventions that increased the cats’ quality of life. Introducing high-meat protein food reduced the number of animals cats killed by 36 per cent, which supports the theory that cats hunt to compensate for micronutrient deficiencies in their diet. Cats who played with a feather toy for five to 10 minutes a day hunted 25 per cent less. Meanwhile, cat bells had no effect on hunting, while brightly coloured collars reduced the number of birds hunted, but not the number of mammals. (The cats didn’t like the collars, noted the researchers.) Use of a “puzzle feeder”, where cats had to solve a problem to access food, increased the cats’ hunting efforts by 33 per cent. To reduce the impact of domestic cats, write the study’s authors, “Owner behaviour is as important as cat behaviour.”
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Storms ahead

In the middle of July, a deluge dumped 690 millimetres of rain on Westport in 72 hours—more than three times the West Coast town’s monthly average. Houses flooded waist-high. More than 2000 people had to be evacuated and at least 100 homes remain uninhabitable. The downpour was driven by an atmospheric flow—warm air saturated with moisture. It’s the kind of event that’s becoming more frequent across the world, according to the latest climate update by the Intergovernmental Panel on Climate Change (IPCC), released in early August. It doesn’t make for cheerful reading. The report confirms that the world has now surpassed 1°C of warming since pre-industrial times, and that all emission scenarios will exceed 1.5°C sometime in the next 20 years. In the most optimistic scenario, warming will only surpass 1.5°C briefly, and temperatures will eventually drop back below 1.5°C later this century. To live in that scenario, we’ll have to bring carbon dioxide emission to net zero by mid-century, make deep cuts in methane emissions and then continue to strip carbon dioxide from the atmosphere. The report also confirms that climate change is now obvious across all lands and oceans, and that it’s our own doing. In its most strongly worded statement of culpability yet, it describes human influence on Earth’s climate as unequivocal and unprecedented. It says that 98 per cent of the warming observed since 1979 can be attributed to our global emissions. Atmospheric carbon dioxide concentrations are now higher than at any time in at least two million years. “Each of the last four decades has been successively warmer than any decade that preceded it since 1850,” it says. If temperature goes up, so will the world’s oceans, and the risk of extreme heat waves, rain and drought, the intensity of  tropical cyclones, and the loss of ice, snow and permafrost. Sea level rise is one of a number of changes we can limit, but no longer reverse. Globally, we are committed to 0.4 metres by the end of this century, on top of 0.2 metres that have already happened, even in the best scenario. Beyond 2100, the process will roll on for centuries. For the first time, the report also includes regional updates. New Zealand is in line with global average trends and has warmed by 1.1°C, while Australia has warmed by 1.4°C. It’s perhaps no surprise that Australia can expect more intense and longer wildfires, but New Zealand, too, has recorded more days with extreme fire risk. The warming of the atmosphere is changing the global water cycle, with shifting storm tracks and wind patterns. One of the consequences for New Zealand is a strengthening of the weather divide: the West Coast will see more extreme wet weather like the Westport floods, while Northland can expect more drought and more intense ex-tropical cyclones. If there’s any consolation in the report, it’s the clarity with which it spells out what we need to do to stay close to 1.5°C of warming.
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Bon Voyage

Introducing the inaugural New Zealand Geographic & Heritage Expeditions reader voyage: Hauraki Gulf and Bay of Islands

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Baby boxers

The mantis shrimp subdues its prey by punching it with a blow that’s strong enough to crack a glass aquarium and generates enough heat to boil water. So when do baby mantis shrimp develop this super-smash prowess? To find out, Duke University researcher Jacob Harrison headed to Hawai‘i with a high-speed camera in search of Gonodactylaceus falcatus larvae—one of the world’s 450 species of mantis shrimp. First, he had to catch a four-millimetre-long larva. “It can be incredibly challenging to sift through a bucket teeming with larval crabs, shrimp, fish and worms to find the mantis shrimp,” says Harrison. Then he had to position the larva in front of his high-speed camera—a task that ended up taking a year to perfect (and involved supergluing the larva to a toothpick). But the effort was worth it. The high-speed footage revealed the mantis-shrimp punch in action: the limb bending back like a spring, before a tiny latch is released that flings the appendage forward with impressive acceleration and speed—around 38 centimetres per second. While the larva was slower than full-grown adults, the jabs were still five to ten times faster than the swimming speed of similar-sized organisms, and 150 times speedier than their prey. After raising some larvae from eggs, Harrison observed that they first began to hunt with their forelimbs between the ages of 9 and 15 days. Although young mantis shrimp go through six to seven transformations from hatching to fully grown, Harrison’s footage showed that the spring-and-latch mechanism is the same in young and old. And while the larva’s punch may be scaled down, the transparent exoskeleton of larvae revealed remarkable detail previously unseen: the tiny muscles contracting as the mantis shrimp wound up for another devastating blow.
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Not an alpine parrot after all

Kea are the mischief-makers of the mountains, but a genome study shows they are not tied to alpine areas. As rising temperatures shrink their habitat, they could return to lowlands—if they can find suitable places to live. Fossils suggest that kea once occupied low-lying areas throughout the South Island and even in the North Island. In fact, there’s nothing “to stop kea from living at lower altitudes”, says University of Otago evolutionary geneticist Michael Knapp. The research scoured the genomes of kea and its sister species kākā, which is adapted to life in the forest, for any genes known to be involved in adaptation to life in the mountains. The commonly held theory was that kea and kākā went their separate ways about two or three million years ago, when the Southern Alps were still rising and opening up new alpine habitats. But Knapp says an ice age was redrawing the landscape at the same time, reducing forests in its wake. “For the ancestors of kea and kākā, their forest habitat shrank, and that made it more likely that some populations ventured into new habitats. That’s what distinguishes them—the kea is the species that went into the open.” The kea’s later retreat to alpine altitudes may have had more to do with avoiding people—including a bounty-hunting scheme that lasted more than a century, from 1867 to 1970, and killed some 150,000 birds. Thankfully, the genome doesn’t show a genetic bottleneck, which suggests the bounty-hunting period was short enough to avoid denting the birds’ genetic diversity, says Knapp. But the study has found a significant difference between the two parrot species. Kākā respond quickly to improved living conditions. When forest cover expanded in the past, so did kākā populations. In contrast, the kea population remained relatively constant, regardless of habitat changes. “Is the kea better at buffering bad habitats, or not so good at responding to good conditions?” asks Knapp. Both species may struggle to adapt to a warming world, says University of Otago PhD candidate Denise Martini. “If native forests begin to suffer from warmer conditions, it is very likely that kākā will suffer, too. Kea might be able to adapt to new conditions, but that depends on whether new conditions are available in the first place. My recommendation for conservation programmes would be to focus on restoring and preserving as much of the existing habitat of both species as possible.”
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The moa diet

In the summer of 2015, in a remote valley of Fiordland National Park, two scientists discover fossil poo fragments underneath a limestone overhang. Analysis suggests the fragments are from moa and are thousands of years old, so a team returns—three years later—to excavate. What they find is a rich deposit of moa poo—called coprolites—that accumulated over a period of two millennia, probably between 6800 and 4600 years ago. But what use is old poo? Scientists can carefully examine the pollen, seeds, DNA and plant microfossils in coprolites to determine what kind of food fuelled the nine moa species that roamed the country. The team determined that these nuggets of dietary information were from little bush moa (Anomalopteryx didiformis), a mid-sized species between 50 and 90 centimetres tall and weighing 26 to 64 kilograms that inhabited lowland forests. This made it an exciting find. “Until now, only five little bush moa coprolites have previously been identified, all from Central Otago,” says lead researcher Jamie Wood from Manaaki Whenua–Landcare Research. The poo contained very few seeds, suggesting that little bush moa were not important seed dispersers. But the fossils were rich in ground-fern spores and fronds, suggesting that fern foliage played an important role in this species’ diet, and that the moa spread the plants around. Because the coprolites were deposited over a period of 2000 years, the researchers were able to trace how the plant matter contained within changed over time. This revealed a shift in the prevailing vegetation from conifers such as miro, mataī and tōtara to the silver beech trees that dominate today.
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Pandemic in the wings

Over the past year, at least 46 countries have recorded outbreaks of the bird flu strain H5N8 among both poultry and wild waterfowl. As a result, millions of birds across Europe, Asia and Africa have been culled. In December 2020, the first H5N8 infections in humans were recorded, with seven Russian poultry workers testing positive for the virus. Although the people did not display any symptoms, the chickens did not fare so well. More than 100,000 from the 900,000-strong flock died. Bird flu comes in a variety of different subtypes, with H5 and H7 particularly concerning due to their potential to affect humans and other animals (there was an outbreak of H5N1 bird flu in captive tigers in 2004). Although rare in humans, bird flu can be deadly. Since 2003, there have been 862 cases of H5N1 bird flu worldwide. More than half of the people who caught H5N1 died. Fortunately, human-to-human transmission has occurred in only a handful of cases. Most infections arise from contact with sick birds. But the ease with which influenza viruses can mutate means that the threat of a bird-flu pandemic looms large. In June, China reported the first confirmed human infection of H10N3 bird flu, a rare strain. Scientists are calling for increased surveillance of poultry farms and wild birds—to find strains with pandemic potential, before they find us.
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The next spillover

The emergence of a new coronavirus is not a question of if, but when and where—and a new study has answered the latter by mapping global regions most likely to produce the next outbreak. The research used horseshoe bats as a model, because they carry several coronaviruses from the same group that caused COVID-19, SARS, and a pig disease known as SADS. The study then connected the dots between several details: where the bats lived, forest fragmentation caused by expanding farmland, human population growth, and increasing numbers of livestock. Where all these things overlap, they “form a nexus where you might have really high risk”, says David Hayman, a Massey University infectious disease ecologist who was part of the international research team. The map—a swathe of horseshoe bat habitat from Spain in the west to the coast of Australia in the east—identifies China as a global hotspot, as well as Bhutan, east Nepal, northern Bangladesh and Thailand, all places where the next spillover event is most likely to transmit a virus from animals to people. In host animals, such viruses usually cause no harm; in other species, such as humans, the viruses can lead to severe and highly contagious disease. We know that if people encroach on wildlife, the risk of spillover increases, says Hayman. Our best chance of preventing such animal-human transmissions from growing into major outbreaks is to increase disease surveillance in high-risk areas. Heightened surveillance could also help contain outbreaks of existing spillovers, such as Ebola, which now re-emerges almost annually. But with a viral universe that likely includes millions of different strains, we need to think beyond pandemic preparedness. “If we really want to reduce the risk, then we need to look at the bigger things—what is causing forest fragmentation, and should we be putting another intensive farm with livestock in this area,” says Hayman, “because the same things that increase the risk of disease emergence also contribute to biodiversity loss and climate change.”
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The size of the COVID problem

The world has a big COVID-19 problem. But just how big? Each infected person carries between one billion and one hundred billion virus particles at the peak of infection. This equates to no more than 0.1 milligrams of virus per infected person—about the same as a single poppy seed. Multiplying by the number of infected people around the world, researchers estimate that our COVID-19 problem can be chalked up to between 0.1 kilograms and 10 kilograms of virus.
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Volcanic fever

Atop the great snow-laden hulk of Ruapehu, the bluish crater lake acts as a barometer for volcanic unrest. Colour changes, rising temperatures and gas emissions measured at this active vent could all point to the possibility of eruption. Now, scientists have another symptom to keep an eye on: sustained, subtle increases in the surface temperature of the whole mountain. Three United States researchers used infrared satellite data to examine five volcanoes around the world: Ruapehu in New Zealand, Ontake in Japan, Calbuco in Chile, Redoubt in Alaska, and Pico do Fogo in Cape Verde. Across 16 years of records, they found that surface temperature increases of up to 1°C preceded eruptive episodes. This slight warming may be a symptom of hydrothermal activity and underground gasses diffusing across large areas, resulting in a change in temperature on the mountains’ flanks that can be detected from space. Sometimes, the warmer temperature lasted for years. The precise warning signs of an imminent eruption remain elusive—crater lakes aren’t crystal balls—but this new method of keeping tabs on volcanic unrest may help anticipate eruptive phases.
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Glow-in-the-dark sharks

In January 2020, Jérôme Mallefet went looking for glowing sharks on the Chatham Rise, off the east coast of the South Island. As researchers on the NIWA ship Tangaroa hauled up trawl nets full of hoki for their annual fisheries survey, Mallefet kept his eyes peeled for bycatch. He and colleagues collected more than 600 deep-sea sharks, representing three species, and transferred 24 into tanks in the wet lab. As the ship pitched and rolled, they photographed the sharks in the dark. They discovered that all three shark species had the ability to glow: two small lanternsharks, and the kitefin shark, Dalatias licha, which reaches up to 1.8 metres in length. That makes the kitefin shark the largest light-producing creature—with a spine—that has ever been found. Mallefet, an expert in bioluminescence from the Catholic University of Louvain in Belgium, says other studies suggest that around ten per cent of the Earth’s approximately 540 shark species can glow. So why do they do it? Partly to recognise each other in their deepwater home, as each species lights up in a particular way. It may help males and females align for reproduction. And glowing can also make the sharks invisible. “These guys are living in the twilight zone, where there is a bluish faint light coming from the surface,” says Mallefet. Seen from beneath, the animals’ bodies appear as silhouettes against the light. But when the kitefin shark illuminates its entire belly with a blue glow, it blends into the light from above. “Suddenly you disappear—that’s how counter-illumination works.” Their dorsal fin also glows—but why remains a mystery. Other recent studies have shown that as many as three-quarters of marine animals in the water column have the ability to make their own light. “Bioluminescence is so widespread, it must have a really critical role for the survival of these organisms down there,” says Mallefet. “The way they communicate, the way they reproduce—bioluminescence plays a role in it, and we are only just discovering that now. “It must be glowing Christmas trees everywhere down there, that’s for sure.”
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Fish dine by moonlight

The phases of the moon affect how fast baby fish grow, a new study has found. Ecologist Jeffrey Shima from Victoria University of Wellington and colleagues found sixbar wrasse larvae grew fastest during the last quarter of the moon—when the first half of the night is dark, and the second part is bright. That’s because when reef fish release their larvae, these float out into the open ocean to feed. There, they meet the mass migration that takes place every night as millions of fish and plankton rise from the deep to feed, then sink before dawn to hide in the dark. Baby sixbar wrasse feed on plankton, which rise more quickly than their predators. But when predators such as lanternfish arrive at the surface, they use their bioluminescent tummies to camouflage themselves against the moon’s light and sneak up on the wrasse. Shima’s hypothesis is that when the moon is full, it’s too bright for plankton to feel safe and for predators to properly conceal themselves, so neither rise all the way to the surface. That leaves the wrasse hungry, but safe. On dark nights, there’s plenty of food—and plenty of lanternfish. But during the last quarter, when the moon rises at midnight, the plankton have already reached the surface, and by the time the predators join them, it’s too bright for them to hunt successfully. The wrasse larvae feed freely and grow more quickly. “This has really big implications for explaining why we see a lot of variation in the survival rates of baby fishes,” says Shima. “If you have months that are more cloudy than average, that might have serious consequences.” Artificial lights from cities may also disrupt these natural cycles.
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All in the mind

Could taking tiny, regular doses of psychedelic drugs enhance your mental health? Not any more than a sugar pill, according to the largest placebo-controlled study on “microdosing” to date. Microdosing involves taking substances such as LSD or psilocybin (the hallucinogenic compound in magic mushrooms) a couple of times a week, at around 10 per cent of a typical recreational dose. It has recently surged in popularity, as the dose is too small to cause hallucinations, but is purported to improve mood, creativity and psychological wellbeing. One hundred and ninety-one people volunteered for the study, administered by researchers in the United Kingdom. Over four weeks, the participants either took drugs or a placebo, without knowing which they were ingesting. After four weeks, those taking psychedelics reported significantly improved wellbeing and life satisfaction. So did the people taking inactive capsules. There were no significant differences between the two groups—both experienced the same positive effects. The researchers suggest the benefits of microdosing arise not from drugs, but from the power of our own expectations.
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Ears on the ocean

The ocean is awash with noise. The clicking of shrimp snapping their claws, the crunching of reef fish grazing, the rumble of a vessel passing overhead—sound travels fast underwater, and in all directions. For animals that rely on sound for communication, such as whales, a cluttered soundscape can be stressful, causing them to change their behaviour. To hear what whales hear—and map where they go—researchers deployed four acoustic recorders in the waters around central New Zealand, collecting soundwaves at various frequencies. The recorders detected the ethereal calls of four whale species: pygmy blue, Antarctic blue, humpback and Antarctic minke whales. Pygmy blue whales were abundant in the South Taranaki Bight, with some visiting Kaikōura in autumn. The other species passed by New Zealand on their annual migration between the tropics and Antarctica. The sound recorders also captured the whooshing ambient background of rain, tides, waves and wind, even earthquakes. Human-generated noises from seismic surveying and ships were also common, and at times overlapped with the whales’ calls. The researchers say this audio information helps identify places in the ocean where human noise might be limited for the whales’ benefit. Whales aren’t the only animals facing hearing problems. Growing up in acidic waters can cause hearing damage in snapper, according to a different study by New Zealand and Australian researchers. Young snapper raised in conditions with elevated carbon dioxide levels were significantly less sensitive to low-frequency sounds. This diminished ability was attributed to changes in the structure of their ear bones and brain chemistry resulting from increased acidity. Hearing is critical for many fish species, playing an important role across their lives: from larval fish deciding where to settle, to individuals synchronising for spawning, to making contact with others.

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