Weekly round-up: June 13

Snowflake moray eels are able to feed on land due to a quirk of evolution (Steve Dunleavy)

Ever considered the mechanics of eating underwater? Most fish rely on suction to hoover up prey, but a wonder of evolution presented the moray eel with a second set of jaws to grab and swallow its meals – which one species has just been found to do on land.

Rita Mehta, associate professor of ecology and evolutionary biology at UC Santa Cruz, investigated the phenomenon after hearing reports of snowflake eels emerging from the water to take crabs on the shore.

However, it took Mehta and her team five years to train seven of the eels to slither up a ramp and eat a piece of fish before returning to the water, instead of snatching the bait and disappearing back into the water. This allowed the team to film both sets of jaws in action, proving their effectiveness in the open air.

“Most fishes really need water to feed,” said Mehta. “This is the first example of a fish that can feed on land without relying on water.”

She added that even apparently amphibious fish previously seen eating on land use the same suction mechanism.

“Mudskippers come up onto mudflats and grab prey like small crabs and insects. They get around the challenge of swallowing on land by sucking up water and then using the water they have reserved in their mouth to swallow.”

Metha, who first recorded the eels’ remarkable second jaw operating underwater in a 2007 paper, paid special thanks to her co-author Kyle Donohoe for his expertise in training marine life.
Publication Journal of Experimental Biology

Harbour porpoises have been seen as primarily solitary animals (Erik Christensen)

Divide, confuse, eat – the new motto of harbour porpoises seen hunting in groups for the first time off the coast of Denmark.

Porpoises have long been thought of as largely solitary animals, but drone footage captured by a team at the University of Southern Denmark revealed extraordinarily sophisticated and coordinated hunting techniques.

From over 44 hours of footage and 159 hunting sequences, researchers recorded between two and six porpoises working together and fulfilling particular roles, including ‘gatherers’, which keep the school of fish close by, and ‘the splitter’, which swims through the school to confuse the fish. Finally, ‘the spear’ swims directly at the school at high speed to snatch fish. 

The discovery raises myriad more questions, including whether the behaviour is seen in all populations and species of porpoise, and if the groups remain static or disband and reform.

“Drones have truly changed the possibilities of studying marine animals, and it will be exciting to see if they can surprise us again,” said co-author Sara Torres Ortiz.

Group hunting behaviour has previously been recorded on land and by other marine mammals, including killer whales which have teamed up to create waves big enough to knock seals off ice floes.

Watch a video of the porpoises in action here
Publication Canadian Journal of Zoology

Abandoned elegant tern eggs on the Bolsa Chica Ecological Reserve (California Department of Fish and Wildlife)

Around 3,000 elegant terns abandoned their nests last month following a drone crash on the Bolsa Chica Ecological Reserve in California, leaving behind more than 1,500 eggs.

The beach, 30 miles south of Los Angeles, is one of only four known breeding grounds for the birds, which are particularly sensitive to perceived threats. Nesting in vast numbers to provide protection from predators, they also display strict “group adherence”, meaning if a few individuals take off, the rest of the flock will follow.

While the airspace above the reserve is restricted, it appears the FAA’s drone mapping app did not accurately show where operators could and could not fly in the area.

However, given the incident occurred relatively early in the breeding season, it is hoped the terns will relocate to one of the other three sites and nest again. Around 14,750 new breeding pairs have arrived at the San Diego Bay National Wildlife Refuge since the end of May, some of which may be from Bolsa Chica.

Before the 1950s elegant terns were known only to nest on the Isla Rasla in the Gulf of California, but due to warming temperatures have gradually moved up the coast in search of feeding grounds.

Staff at Bolsa Chica are developing a land management programme in the hope the birds return next year.
Source National Audubon Society

Seabirds use sea wrack for nesting, food – and air conditioning (USA)

Sea wrack – seaweed washed on shore by the tide – serves as an air conditioner for migratory seabirds and should be left on beaches according to a new study.

Tangled masses of brown seaweed are a common sight on beaches around the world, but are often cleared to encourage tourists or for industrial use in agriculture and other industries.

However, a study from the University of South Australia has revealed that, in addition to providing food and shelter, sea wrack helps keep birds cooler in warm weather and warmer in cooler conditions, assisting in temperature regulation.

“Australian beaches are renowned for stretches of golden sand – it’s one of the main draw cards for tourists – so it’s not altogether surprising that beachside destinations tend to favour a seaweed-free coastline,” said co-author Tim Davis. “The challenge is, however, that while people may see beach-cast sea wrack as an eye-sore, it actually has an ecological role to fulfill, particularly for migratory shorebirds. 

“Our research shows that sea wrack provides important microclimates to help seabirds regulate their body temperatures – they mostly forage, rest and roost in the older, dryer wrack, which is warm throughout most of the day. However, they also seek refuge among fresh wrack in the early mornings when it is the warmest habitat available. 

“Shore birds move between the different wrack types depending on the prevalent weather conditions. This helps them conserve and build sufficient energy stores for successful migration and reproduction in overseas breeding grounds. 

“When sea wrack is removed, then so too are the habitats of these sea birds, and this can have a devastating impact on their populations.”
Publication Journal of Applied Ecology

Antler moths in Norway are now distributed further north than 20 years ago (Helmut Diekmann)

Around 40 per cent of butterflies and moths in Norway have been unable to adapt to warming temperatures caused by climate change, resulting in decreasing population numbers.

Changing conditions have prompted roughly 45 per cent of species to spread northwards or begin flying earlier in the year, with the remaining 15 per cent showing both adaptive behaviours.

Researchers from the University of Helsinki, who studied data over a 20-year period in collaboration with the Finnish Environment Institute, stressed the importance of extensive, interconnected high-quality habitat that enables species to adapt and migrate in response to climate change.

“For organisms to be able to respond to climate change by shifting their range further north, sufficient amounts of suitable habitats of high-quality are needed,” said Mikko Kuussaari, senior researcher at the Finnish Environment Institute. “Declining populations are usually not able to provide a sufficient basis for the species to spread to new areas. Small populations also contain less genetic diversity that could help the local populations adjust by changing the timing of their flight.”

The team also noted that the 27 per cent of species to have advanced their flight time was lower than seen elsewhere in Europe, suggesting increasingly daylight in the spring plays a bigger role than temperature alone.
Publication Ecology Letters

Climate change and biodiversity loss must be tackled together if both crises are to be averted, according to the first joint report between the IPCC and IPBES.

Accelerated rates of global warming and species depletion are both due to human activities, and both reinforce the other. As climate change continues to transform environments, plant and animal species are losing habitat, while the loss of terrestrial and marine ecosystems capable of storing carbon reduces the planet’s ability to manage excess greenhouse gases.

The report notes previous policies have generally only tackled one issue or the other, but policies designed to mitigate both can maximise benefits and are more likely to meet global development goals.

“Human-caused climate change is increasingly threatening nature and its contributions to people, including its ability to help mitigate climate change,” said Professor Hans-Otto Pörtner, co-chair of the scientific steering committee. “The warmer the world gets, the less food, drinking water and other key contributions nature can make to our lives, in many regions. Changes in biodiversity, in turn, affect climate, especially through impacts on nitrogen, carbon and water cycles. 

“The evidence is clear: a sustainable global future for people and nature is still achievable, but it requires transformative change with rapid and far-reaching actions of a type never before attempted, building on ambitious emissions reductions. 

“Solving some of the strong and apparently unavoidable trade-offs between climate and biodiversity will entail a profound collective shift of individual and shared values concerning nature – such as moving away from the conception of economic progress based solely on GDP growth, to one that balances human development with multiple values of nature for a good quality of life, while not overshooting biophysical and social limits.”

Among the recommendations, the report highlights halting the loss and degradation of species- and carbon-rich ecosystems and increasing sustainable agriculture and forestry practices, while moving away from climate change mitigation measures that damage biodiversity such as the planting of monocultures for biofuels and carbon capture.

“[The] land and ocean are already doing a lot – absorbing almost 50 per cent of CO2 from human emissions – but nature cannot do everything,” said IPBES chair Ana María Hernández Salgar. “Transformative change in all parts of society and our economy is needed to stabilize our climate, stop biodiversity loss and chart a path to the sustainable future we want. This will also require us to address both crises together, in complementary ways.”

It’s a science-fiction writer’s dream come true. Bdelloid rotifers – microscopic multicellular animals – have been recovered and revived from the Siberian permafrost after spending 24,000 years in a state of suspended animation known as cryptobiosis.

Previously the longest reported survival of the tiny organism was ten years, some way short of the 24 millennia since recorded – placing the animals on Earth at the same time as woolly mammoths and giant deer.

In addition to reanimation after thawing, the rotifers were also able to reproduce. 

“The takeaway is that a multicellular organism can be frozen and stored as such for thousands of years and then return back to life,” said co-author, speaking to the Press Association.

The research team is now examining how the animals achieve this time-stopping feat, freezing and thawing the ancient rotifers in the laboratory.
Publication Current Biology

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