A new postgraduate programme will train researchers to understand life's origins, search for habitable planets and consider the most profound question of all: are we alone?

Local communities are not incentivised to protect tropical forests that are hugely valuable for global climate regulation, a new study has found. International funding could help smallholder farmers to boost yields on their existing land to incentivise long-term forest protection.

How new ways of shellfish farming could help meet future food needs.

A new study provides the first experimental evidence that the trumpetfish, Aulostomus maculatus, can conceal itself by swimming closely behind another fish while hunting – and reduce the likelihood of being detected by its prey.

In this ‘shadowing’ behaviour, the long, thin trumpetfish uses a non-threatening species of fish, such as parrotfish, as camouflage to get closer to its dinner.

This is the only known example of one non-human animal using another as a form of concealment.

The research involved hours of diving in the Caribbean Sea, pulling hand-painted model fish along a wire.

“When a trumpetfish swims closely alongside another species of fish, it’s either hidden from its’ prey entirely, or seen but not recognised as a predator because the shape is different,” said Dr Sam Matchette, a researcher in the University of Cambridge’s Department of Zoology and first author of the study.

Damselfish, Stegastes partitus, form colonies on the seafloor and are a common meal for trumpetfish. Working amongst the coral reefs off the Dutch Caribbean island of Curaçao, researchers set up an underwater system to pull 3D-printed models of trumpetfish on nylon lines past colonies of damselfish, and filmed their responses.

When the trumpetfish model moved past alone, damselfish swam up to inspect - and rapidly fled back to shelter in response to the predatory threat.

When a model of a herbivorous parrotfish, Sparisoma viride, moved past alone, the damselfish inspected and responded far less.

When a trumpetfish model was attached to the side of a parrotfish model – to replicate the shadowing behaviour of the real trumpetfish – the damselfish responded just as they had to the parrotfish model alone: they had not detected the threat.

Matchette said: “I was surprised that the damselfish had such a profoundly different response to the different fish; it was great to watch this happening in real time.”

The study, involving collaborators at the University of Bristol, is published today in the journal Current Biology.

“Doing manipulative experiments in the wild like this allows us to test the ecological relevance of these behaviours,” said Professor Andy Radford in the University of Bristol’s School of Biological Sciences, and coauthor of the study.

Matchette, along with his co-author and dive buddy Christian Drerup, spent hours underwater, barely moving, to conduct their experiment.

Their earlier questioning of divers working at dive shops in the Caribbean revealed that trumpetfish are commonly seen swimming alongside parrotfish and other reef fish – but the reason for this remarkable behaviour had not been tested.

In addition, divers were much more likely to have seen the shadowing behaviour on degraded, less structurally complex reefs.

Coral reefs around the world are being degraded due to the warming climate, pollution and overfishing. The researchers say the strategy of hiding behind other moving fish may help animals adapt to the impacts of environmental change.

 “The shadowing behaviour of the trumpetfish appears a useful strategy to improve its hunting success. We might see this behaviour becoming more common in the future as fewer structures on the reef are available for them to hide behind,” said Dr James Herbert-Read in the University of Cambridge’s Department of Zoology, senior author of the study.

Human duck hunters historically hid behind cardboard cut-outs of domestic animals - called ‘stalking horses’ - to approach ducks without being detected. But this strategy has received little attention in non-human animals and has never been experimentally tested before. 

The research was funded by The Whitten Programme in Tropical and Aquatic Biology, The Association for the Study of Animal Behaviour, and The Fisheries Society of the British Isles.

Reference

Matchette, S R et al.: ‘Predatory trumpetfish conceal themselves from their prey by swimming alongside other fish.’ Current Biology, August 2023. DOI: 10.1016/j.cub.2023.05.075

An experiment on coral reefs provides the first evidence that predators use other animals for motion camouflage to approach their prey without detection.

The shadowing behaviour of the trumpetfish appears a useful strategy to improve its hunting success.James Herbert-Read Stealth swimmers: the fish that hide behind others to hunt Sam MatchetteParrotfish model pulled across reef on a wire.

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African cuckoos may have met their match with the fork-tailed drongo, which scientists predict can detect and reject cuckoo eggs from their nest on almost every occasion, despite them on average looking almost identical to drongo eggs.

Butterflies with smaller or lighter coloured wings are likely to be ‘losers’ when it comes to climate change, with the Lycaenidae family, which contains over 6,000 species of butterflies, the majority of which live in the tropics, found to be particularly vulnerable.

Butterflies with larger or darker coloured wings are likely to fare better under increasing temperatures, but only to a point. Researchers say these butterflies could still experience dramatic declines if there were sudden heatwaves or if cool microclimates were lost through deforestation.

The results are published today in the Journal of Animal Ecology.

Butterflies rely on the sun’s warmth to give them the energy they need to function. They use ‘thermoregulation’ strategies to maintain a balanced body temperature against changing air temperatures.

Generally, strategies to keep cool involve adaptive behaviours like flying to a shady spot or angling wings away from the sun (thermal buffering). But when this is not possible or temperatures become too hot, species have to rely on physiological mechanisms such as the production of heat shock proteins to withstand high temperatures (thermal tolerance). Both of these strategies are needed to cope with climate change.

Researchers collaborated with the Smithsonian Tropical Research Institute (STRI) to study the thermal buffering and thermal tolerance strategies of tropical butterflies. They collected data from multiple habitats in Panama.  

Equipped with hand-held nets, ecologists took the temperature of over 1,000 butterflies using a tiny thermometer-like probe. They compared each butterfly’s temperature to that of the surrounding air or the vegetation it was perched on. This gave a measurement of thermal buffering – the ability to maintain a steady body temperature against fluctuating air temperatures.

A second experiment was conducted at STRI Gamboa facilities and involved assessing butterflies’ thermal tolerance – their ability to withstand extreme temperatures, such as those they may experience during a heatwave. This was assessed by capturing a subset of butterflies and placing them in glass jars within a water bath – the temperature of which was steadily increased. Thermal tolerance was assessed as the temperature at which butterflies could no longer function.

Butterflies that had large wings tended to have greater thermal buffering ability but less thermal tolerance than smaller butterflies. Indeed, in a further study conducted by the same research team, butterflies with larger, longer and narrower wings were found to be better at thermal buffering.

Thermal buffering abilities were found to be stronger in darker-winged butterflies who could also tolerate higher temperatures than paler-winged butterflies.

Butterflies from the Lycaenidae family which have small, bright, and often iridescent, wings had the poorest thermal buffering and low thermal tolerance. If temperatures continue to rise at the current rate, forests continue to be cut down, and cool microclimates are lost, there is a very real threat that we could lose many species in this family in the future, say the researchers.

A trade-off in terms of butterflies’ cooling strategies was observed: those that were good at thermal buffering were less good at thermal tolerance and vice versa.

Scientists say this suggests that tropical butterflies have evolved to cope with temperature changes using one of these strategies at the expense of the other, and that this is likely to be due to selective pressures.

Lead author Esme Ashe-Jepson, a PhD student at Cambridge’s Department of Zoology, said: “Butterflies with physical characteristics that may help them to avoid the sun’s heat, like having large wings that enable them to fly quickly into shade, rarely experience high temperatures, and so have not evolved to cope with them. On the other hand, species which can cope with higher temperatures physiologically have experienced less selective pressure to evolve heat-avoiding behaviours.

“As temperatures continue to rise, and forest fragments get smaller and further apart because of deforestation, butterflies which rely on their surroundings to avoid high temperatures may not be able to travel between forest fragments, or cope with increasingly common heatwaves.”

The researchers say this means that species with large dark wings that are good at thermal buffering may initially be unaffected by warming temperatures, as they can continue to thermoregulate effectively using behaviour and microclimates, but their survival could be at risk if there are sudden heatwaves, or they can no longer escape to cool vegetation.

“Ultimately all insects, including butterflies, the world over are likely to be affected by climate change,” said Ashe-Jepson. “Adaptation to climate change is complex and can be impacted by other factors such as habitat destruction. We need to address these two global challenges together.”

Further research is needed to investigate the effect a warming climate may have on other life stages of butterflies, such as caterpillars and eggs, and other insect groups.

Senior author Greg Lamarre, at the Czech Academy of Science and Research Associate at STRI said: “Worldwide, most entomologists are observing drastic declines in insect biodiversity. Understanding the causes and consequences of insect decline has become an important goal in ecology, particularly in the tropics, where most of terrestrial diversity occurs.”

The research was funded by the GACR Czech Science Foundation, an ERC Starting Grant, a Smithsonian Tropical Research Institute short-term fellowship, and the Sistema Nacional de Investigación (SENACYT), Panama.

Reference:

Esme Ashe-Jepson et al. Tropical butterflies use thermal buffering and thermal tolerance as alternative strategies to cope with temperature increase. Journal of Animal Ecology DOI: 10.1111/1365-2656.13970

The family, wing length and wing colour of tropical butterflies all influence their ability to withstand rising temperatures, say a team led by ecologists at the University of Cambridge. The researchers believe this could help identify species whose survival is under threat from climate change.

Ultimately all insects, including butterflies, the world over are likely to be affected by climate change.Esme Ashe-JepsonEsme Ashe-JepsonEsme Ashe-Jepson conducing fieldwork in Panama, with a Juditha caucana butterfly from the Riodinidae family.

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Yes

The extensive study assessed the movements of 7,137 individual birds from 77 species of petrel, a group of wide-ranging migratory seabirds including the Northern Fulmar and European Storm-petrel, and the Critically Endangered Newell’s Shearwater.

This is the first time that tracking data for so many seabird species has been combined and overlaid onto global maps of plastic distribution in the oceans.

The results show that plastic pollution threatens marine life on a scale that transcends national boundaries: a quarter of all plastic exposure risk occurs in the high seas. This is largely linked to gyres - large systems of rotating ocean currents - where vast accumulations of plastics form, fed by waste entering the sea from boats, and from many different countries.

Seabirds often mistake small plastic fragments for food, or ingest plastic that has already been eaten by their prey. This can lead to injury, poisoning and starvation, and petrels are particularly vulnerable because they can’t easily regurgitate the plastic. In the breeding season they often inadvertently feed plastic to their chicks.

Plastics can also contain toxic chemicals that can be harmful to seabirds.

Petrels are an understudied but vulnerable group of marine species, which play a key role in oceanic food webs. The breadth of their distribution across the whole ocean makes them important ‘sentinel species’ when assessing the risks of plastic pollution in the marine environment.

“Ocean currents cause big swirling collections of plastic rubbish to accumulate far from land, way out of sight and beyond the jurisdiction of any one country. We found that many species of petrel spend considerable amounts of time feeding around these mid-ocean gyres, which puts them at high risk of ingesting plastic debris,” said Lizzie Pearmain, a PhD student at the University of Cambridge’s Department of Zoology and the British Antarctic Survey, and joint corresponding author of the study.

She added: “When petrels eat plastic, it can get stuck in their stomachs and be fed to their chicks. This leaves less space for food, and can cause internal injuries or release toxins.”

Petrels and other species are already threatened with extinction due to climate change, bycatch, competition with fisheries, and invasive species such as mice and rats on their breeding colonies. The researchers say exposure to plastics may reduce the birds’ resilience to these other threats.

The north-east Pacific, South Atlantic, and the south-west Indian oceans have mid-ocean gyres full of plastic waste, where many species of threatened seabird forage.

“Even species with low exposure risk have been found to eat plastic. This shows that plastic levels in the ocean are a problem for seabirds worldwide, even outside of these high exposure areas,” said Dr Bethany Clark, Seabird Science Officer at BirdLife International and joint corresponding author of the study.

She added: “Many petrel species risk exposure to plastic in the waters of several countries and the high seas during their migrations. Due to ocean currents, this plastic debris often ends up far away from its original source. This highlights the need for international cooperation to tackle plastic pollution in the world’s oceans.”

The study also found that the Mediterranean Sea and the Black Sea together account for over half of petrels’ global plastic exposure risk. However, only four species of petrel forage in these enclosed, busy areas.

The study was led by a partnership between the University of Cambridge, BirdLife International and the British Antarctic Survey, in collaboration with Fauna & Flora International, the 5 Gyres Institute, and over 200 seabird researchers in 27 countries.

It is published today in the journal Nature Communications.

To get their results, the researchers overlaid global location data, taken from tracking devices attached to the birds, onto pre-existing maps of marine plastic distribution. This allowed them to identify the areas on the birds’ migration and foraging journeys where they are most likely to encounter plastics.

Species were given an ‘exposure risk score’ to indicate their risk of encountering plastic during their time at sea. A number of already threatened species scored highly, including the Critically Endangered Balearic Shearwater, which breeds in the Mediterranean, and Newell’s Shearwater, endemic to Hawaii.

Another Endangered species, the Hawaiian Petrel also scored high for plastic exposure risk, as did three species classified by the IUCN as Vulnerable: the Yelkouan Shearwater, which breeds in the Mediterranean; Cook’s Petrel, which breeds in New Zealand, and the Spectacled Petrel, which only breeds on an extinct volcano called Inaccessible Island, part of the Tristan da Cunha archipelago, a UK Overseas Territory.

“While the population-level effects of plastic exposure are not yet known for most species, many petrels and other marine species are already in a precarious situation. Continued exposure to potentially dangerous plastics adds to the pressures,” said Professor Andrea Manica at the University of Cambridge’s Department of Zoology, a co-author of the study.

He added: “This study is a big leap forward in understanding the situation, and our results will feed into conservation work to try and address the threats to birds at sea.”

The research was funded by the Cambridge Conservation Initiative’s Collaborative Fund for Conservation, sponsored by the Prince Albert II of Monaco Foundation, and the Natural Environment Research Council.

Reference

Clark, B.L. et al.: ‘Global assessment of marine plastic exposure risk for oceanic birds.’ Nature Communications, July 2023. DOI: 10.1038/s41467-023-38900-z

Analysis of global tracking data for 77 species of petrel has revealed that a quarter of all plastics potentially encountered in their search for food are in remote international waters – requiring international collaboration to address.

Ocean currents cause big swirling collections of plastic rubbish to accumulate far from landLizzie PearmainBeth ClarkNorthern Fulmar bird in flight

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The tale of two charismatic species cooperating for mutual benefit has captivated naturalists for centuries – but evidence has been patchy. Researchers have now carried out the first large-scale search for evidence.

These ‘Green’ farming policies risk worsening the global biodiversity crisis by reducing how much food is produced in a region, driving up food imports and increasing environmental damage overseas.

In an article published today in the journal Nature, Professor Andrew Balmford at the University of Cambridge, and Professor Ian Bateman at the University of Exeter, urge policy-makers to consider a bolder approach known as ‘land sparing’ - which they argue is cheaper, more effective, and avoids displacing food production and worsening the loss of wildlife habitats overseas.

Land sparing involves finding lower-impact ways to boost yields in farmed areas, and allow larger, non-farmed areas of the landscape to be put aside for nature - without increasing imports and damaging overseas wildlife.

The researchers say the approach has been overlooked by policymakers because of a failure to consider the wider consequences of changes in land management. They argue that changes that boost wildlife locally seem superficially attractive, but if food production is reduced there are unavoidable knock-on effects elsewhere that must also be taken into account.

They also cite the influence of the ‘Big Farm’ lobby in maintaining the status quo in agricultural policy, with land-sharing subsidies allocated using a flat rate per hectare, which disproportionately benefits the biggest farms – resulting in the largest 12 per cent of farms taking 50 per cent of all UK taxpayer subsidies.

Their article debunks some of the benefits to biodiversity of three widely-advocated green farming approaches.

They argue that while policy funded measures such as reducing the use of pesticides and fertilisers can sometimes increase populations of more common animals and plants on farms it does little for endangered birds, invertebrates, plants and fungi species that need larger stretches of non-farmed habitat – and by lowering yields can also make matters far worse for overseas biodiversity.

Rewilding initiatives, where large areas of land are taken out of farming, can indeed benefit locally endangered species. But unless other areas see compensating increases in food output then this reduces local production, increases demand for food imports, and so damages biodiversity overseas.

They also argue that organic farming, where crops are produced without manufactured fertilisers and modern pesticides, is even more likely to be damaging. Relatively few species will benefit in the farmed area, and the substantially lower yields from this type of farming risk greatly increasing the need for food imports, and hence a country’s impacts on biodiversity elsewhere.

Land sparing, in contrast, involves retaining or creating sizeable blocks of unfarmed land containing larger populations of the many species that depend on natural habitats, as well as boosting farm yields elsewhere in the region so that overall production is maintained or even increased.

Promising methods to boost crop and livestock yields more sustainably than current high-yield practices include genomic screening and gene editing to accelerate animal and crop breeding; using new advances in aquaculture to produce high value foods with much lower environmental impacts; and, in tropical countries, greater access to improved pasture and veterinary care.  

The researchers point to field studies on five continents that consistently show how land sparing delivers far greater biodiversity gains than conventional ‘nature friendly farming’ policies.

They say it is likely to cost a great deal less as well: a survey of UK farmers last year found that land sparing could deliver the same biodiversity outcomes for birds as conventional approaches but at 48 per cent of the cost to taxpayers, and with a 21 per cent lower impact on food production.

Professor Bateman, a Professor of Environmental Economics at the University of Exeter Business School who has advised seven UK secretaries of state for the environment in the past decade, said:

“The stakes are too high for policymakers to continue to ignore the promise of land sparing when so much research demonstrates that it is a far more effective approach than many of the strategies being deployed.

“Unless researchers and policymakers assess the overall, global effects of interventions aimed at addressing biodiversity loss and climate change, poor decisions that are unsupported by the data will at best under-deliver, and at worst exacerbate existential threats posed by the extinction and climate crises.”

Andrew Balmford, a Professor of Conservation Science at the University of Cambridge who has led 20 years’ work investigating how to reconcile food production with biodiversity conservation, added:

“This issue has become even more urgent since last December when many countries agreed to help meet the Convention on Biological Diversity’s goal of protecting 30 per cent of the planet’s land and oceans by 2030.

“Exactly how this 30 per cent will be put aside - and how we meet humanity’s growing needs on the rest of planet - will in large part determine the biodiversity consequences of this ambitious commitment.”

Reference

Bateman, I. and Balmford, A.: ‘Current conservation policies risk accelerating biodiversity loss.’ Nature, June 2023.

Adapted from a press release by the University of Exeter.

Rewilding, organic farming and the so-called ‘nature friendly farming’ measures included in some government conservation policies may accelerate global biodiversity loss, say two leading researchers.

Joyce G on Unsplash

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Should we be worried about frequent news reports of flu being detected in birds and other animals?