According to the research, the levels of mercury found in Arctic foxes depend on their diets Scientists say that foxes in Arctic regions who feed on ocean prey are being exposed to dangerous levels of mercury. On one Russian island where the population of foxes has crashed, the researchers believe the toxin has played a key role in the decline. They say the findings could have important implications for conservation. The data is published in the Journal, PLOS ONE. Mercury levels in the world's oceans have doubled over the past 100 years, according to the UN, with more mercury deposited in the Arctic than on any other part of the planet. The Arctic Council says there has been a ten-fold increase in the levels of mercury found in top predators in the region over the past 150 years. Hair of the dog Now a team of researchers says it has found significant levels of mercury in different populations of Arctic foxes in different environments. On the small Russian island of Mednyi, part of the Commander Islands chain in the North Pacific Ocean, the foxes survive almost exclusively on sea birds with some also eating seal carcasses. The island's fox population declined mysteriously in the 1970s, and while the population is currently stable many of them are in poor condition, and have low body weight. They are listed as a critically endangered species with IUCN. Scientists at one time believed their shrinking numbers were caused by an infection, but they couldn't find the underlying cause.

World's reptiles at risk of extinction

Many lizards are under threat, including the mountain horned agama of Sri Lanka

Almost a fifth of the world's reptile species are at risk of extinction, according to scientists.

Research led by the Zoological Society of London found that the future of 19% of the world's reptiles are threatened. Conservation experts also confirmed that 47% are vulnerable and highlighted the possible extinction of three species. The figures are based on a random sample of 1,500 of the world's reptile species. "It's essentially an election poll set up - using this sample to give an example of how reptiles are doing as a whole," explained Dr Monika Bohm, lead author of the study published in the journal Biological Conservation. The study was made in conjunction with 200 experts from the International Union for the Conservation of Nature's Species Survival Commission.

Rhino poaching in South Africa reaches record levels

Figures from the South African government indicate that poaching for rhinoceros has increased substantially in the last year.

A record 668 rhinos were killed for their horns in 2012, up almost 50% on the number for 2011. The majority of the animals were killed in the Kruger national park, the country's biggest wildlife reserve.

Experts say that growing demand for rhino horn in Asia is driving the slaughter.

Rhinos and elephants: the secret lives of Africa's giants

Rhinos and elephants have a range of remarkable behaviours and adaptations, many of which we are only just learning. Emerging through the twilight, a beast lumbers forward, sniffing, snorting, searching for something. One of the largest animals to walk the earth, it is on a surprising mission. This black rhino is embarking on a midnight journey, seeking out other rhinos in the dark to socialise and mate with, sharing some never-before-seen tender moments.

Because despite their size, we are only just beginning to notice some remarkable behaviours and adaptations of elephants and rhinos. These two groups are the largest terrestrial animals. The three species of elephant range from 5.5 tonnes for an average male African bush elephant to 2.7 tonnes for female Asian elephants.

Rhinos, of which there are five species, can exceed 3.5 tonnes. Their size makes them relatively easy to spot and an easy target for poachers, who continue to hunt both groups of large mammal in significant numbers: elephants mainly for ivory in their tusks and rhinos for their horns. They have all been extensively studied by scientists, in the field and also in wildlife parks, breeding centres and zoos. But much about them, and what they get up to, remains a mystery, with many discoveries into their behaviour and adaptations only being made recently. We are still struggling to understand just how unique are different populations of these megafauna.