Polar bear diet switches from seals to eggs

Polar bear diet switches from seals to eggs

For daily news stories, visit newscientist.com/news POLAR bears may be ditching seafood in favour of scrambled eggs as the heat rises in the Arctic, ...

233KB Sizes 0 Downloads 24 Views

For daily news stories, visit newscientist.com/news

POLAR bears may be ditching seafood in favour of scrambled eggs as the heat rises in the Arctic, melting sea ice. A changing coastline has made it harder for the predators to catch the seals they favour and is pushing them towards poaching goose eggs. This is according to a team led by Charmain Hamilton of the Norwegian Polar Institute that monitored polar bears and seals before and after a sharp decline in sea ice in 2006 in the Norwegian archipelago of Svalbard. The team attached tracking devices to 60 ringed seals as well as 67 polar bears, which allowed them to see how the ice loss affected their movements. Before the melt, when they were hunting on stable sea ice, the polar bears had a big advantage over their favoured prey. However, on a melting coastline punctuated by broken-up icebergs, the odds become stacked in the seals’ favour. In response, the bears are retreating from the coast – and away from the seals. The tracking devices show them wandering greater distances in search of alternative land-based food. The bears also spend a lot more time near bird nesting grounds, which suggests eggs have become a significant food source. This shift could devastate nesting bird populations (Journal of Animal Ecology, doi.org/b63h). “It takes on average 30 seconds to locate a nest and 60 seconds to eat the eggs,” says Jouke Prop at the University of Groningen, the Netherlands. Previous research found that affected bird populations can slump by up to 90 per cent. As the bears move on to eating bird eggs, any drop in geese populations could bring wider ecological changes. “If numbers decline – which is to be expected – this will have an impact on the whole terrestrial ecosystem,” says Prop. “For example, Arctic foxes depend on young geese as food; reindeer food intake is facilitated by geese grazing the tundra.” Thom Hoffman n

MARK GARLICK/SCIENCE PHOTO LIBRARY

Polar bear diet switches from seals to eggs

Hazael, or they may use certain chemicals or fats in a way that safeguards their delicate interiors. The rigid glass-like state is similar to what happens in a nonNewtonian fluid like oobleck, says Barry Herschy, an astrobiologist at the University of South Florida who studies extremophile bacteria. This mixture of flour and water hardens into a cohesive shape when thrown against a wall, but simply looks like wet flour when at rest. However, he notes that the recent experiments were conducted at low temperatures, whereas the normal conditions that would cause a sudden shock compression would also cause extreme heating. It’s unclear how –Home sweet home– heat would have changed the microbes’ survival, he says. “It does indicate that survival of bacteria would be possible on a meteorite or a comet,” Herschy says. “It actually shows life would be able to survive on a planet even if it was under bombardment.” Hazael found that the called shock compressions. microbes not only survived short Rebecca Boyle To find out, Hazael and her blasts of pressure, but went on BACTERIA riding on an incoming colleagues subjected a hardy, to reproduce in colonies (Icarus, meteorite may be able to survive metal-eating microbe called doi.org/b66b). This implies that the violent shockwave created Shewanella oneidensis to varying this type of bacteria may have when it crash-lands on a planet. levels of sudden, extraordinarily thrived on Earth prior to and Their cell walls have been seen high pressures. After each blast during the Late Heavy to rapidly harden and relax after in increasingly high-pressure Bombardment 3.8 billion years a sudden shock compression, ago, when the planet was “When you are exposing enabling them to bounce back hammered by meteorites. life to extreme conditions, even after an extreme collision. This also means that bacteria it is a surprise when they “When you are exposing might survive a spacecraft survive quite well” life to such extreme conditions, landing – or even crashing – on it is a surprise when they survive other planets. That would lend quite well,” says Rachael Hazael at experiments, the team cultured weight to the panspermia theory, University College London. the microbial survivors and found in which comets or meteorites Microbes can withstand they fared better in a sudden could potentially deliver life to extreme environments on Earth, high-pressure environment than otherwise sterile planets. It is also including the crushing pressures in long-lasting high-pressure something to keep in mind for found in the deep ocean and far conditions. space agencies and private beneath the ground. This suggests To withstand these conditions, companies exploring the solar that life forms could thrive on the microbes adjusted the system and beyond. distant worlds in similar highrigidity of their cell, says Hazael. “Every time we explore a new pressure environments. “They adopt this glassy cellular environment, we find life is But few people have studied behaviour, which allows them already there, so I’m never what happens to microbes to maintain their integrity.” surprised when I find out these under the very short-lived The bacteria could have small things,” Herschy says. “Any niche high-pressure conditions genetic mutations that would that becomes available, life finds formed during collisions, enable them to survive, says a way to adapt to it.” n

Bacteria survive asteroid crashes

20 May 2017 | NewScientist | 9