What the scientists are saying…
Do cod have regional accents? Cod being driven north by global warming may find they can’t understand the accents of the fish they meet there – and this matters, scientists have warned, because if they can’t communicate, how will they attract mates? Like many fish, cod vibrate their swim bladders to produce a variety of sounds – thumps, drumming noises and long growls – which allow males to coax females into releasing their eggs. Previous studies have shown that the mating calls of American cod differ significantly from European cod. Now, scientists at Exeter University are recording cod sounds in waters around the UK, to find out if there are regional variations too. “This species is highly vocal, with traditional breeding grounds established over hundreds or thousands of years, so the potential for regionalism is there,” said Dr Steve Simpson, the study’s leader. Cod may already be having trouble communicating, owing to noise pollution from ships and marine engineering. Simpson and his colleagues fear that if males cannot woo females, due to dialect differences, this will cause further serious problems in the future, when rising sea temperatures are likely to lead to many cod seeking out new breeding grounds. “If we value our fish stocks – or our Friday-night fish supper – we need to understand this,” he said.
A Swiss snow shortage Ski resorts in Switzerland are experiencing almost 40 fewer days of snow cover a year than four decades ago, new research shows – raising fears about the country’s viability as a Christmas-to-easter skiing destination. The study, by a team at the University of Neuchâtel, found that snow is arriving, on average, 12 days later than in the 1970s, while the melt is occurring around 25 days earlier. Although previous studies have documented such falls at lower altitudes, this one found the pattern at altitudes of up to 2,500 metres, suggesting ski areas at resorts such as Zermatt could be affected. “Skiing won’t die out in the Alps – the winter snowfall is assumed,” Professor Martine Rebetez told The Daily Telegraph. “But we’ll have fewer and fewer days when you can be sure the skiing will be good.”
Pill linked to depression A Danish study has produced arguably the best evidence yet that taking the pill increases a woman’s chances of developing depression. Researchers analysed medical data of a million women aged between 15 and 34, and found that those on the combined pill – which contains artificial versions of the hormones oestrogen and progesterone – were 23% more likely to be prescribed an antidepressant than those not taking hormonal contraception. For those on the progestin-only pill, the figure rose to 34%. And it increased still further for girls aged between 15 and 19 on the combined pill: they were 80% more likely to be treated for depression. The findings only show a correlation between the pill and depression, and do not establish a causal link. However, the researchers suspect that depression can be triggered by hormonal changes caused by going on the pill; and that raised levels of progesterone – linked to a lowering of mood by some previous studies – is the most likely culprit.
The meerkat and other murderers They may look cute, but meerkats are, by one measure at least, the most vicious of all mammals. The burrowing carnivore, which lives mainly in the deserts of Southern Africa, has topped a list of more than 1,000 mammals ranked according to their tendency to commit lethal violence against their own species. In a recent study, researchers at Granada University found that 19.4% of all meerkat deaths are the result of an attack by another meerkat; at the other end of the scale, tigers (0.88%), African forest elephants (0.29%) and zebras (0%) are pretty nice to each other. The researchers identified living in social groups and maintaining territory as the two factors most associated with violence. Meerkats live in packs of between 20 and 50. As for humans, the researchers calculated Homo sapiens had an overall own-species kill rate of 2% – lower than chimps (4.5%) but higher than bonobos (0.68%). However, the archaeological evidence suggests the human rate has fluctuated significantly over time: it was about 2% when we lived in small hunter gatherer groups, rose to 12% in medieval Europe and Asia, then fell to 1.3% in the modern era, when the rule of law was established.