Entries in antarctic (3)
Photo courtesy of Ashley Coates
That’s right, David is back on our screens on the 26th of this month to bring us another stunning wildlife series; Frozen Planet. Little snippets of this series have been released to the media and general public over the past few days and it looks to be just as cool as the locations it's set in! A few species have already made an appearance in wildlife news recently such as crafty killer whales and thieving penguins. To get us all in the mood for the new series, here is a mini food chain detailing why some species make good predators and why some make tasty prey!
Polar bears are one of the apex predators within this food chain. Males are very large and can reach up to 350 – 680 kg and 7.9 – 9.8 ft. in length, with females measuring half that length. Because of their large size, it makes it possible for them to smash into ice dens of seals and tear into prey easily. This is assisted by shorter claws on their feet and their extremely large paws, which can measure approximately 30cm across! Their keen sense of smell also helps them when hunting prey. Polar bears are able detect unburied seals from nearly 1 mile away and buried seals under 3 ft. of snow!
Killer whales are another apex predator that drift in and out of the icy waters surrounding Antarctica and the Artic. They have a varied diet depending on which subspecies they are and their geographical location. Killer whales make excellent predators due to their high intelligence and ability to work as a team. Just recently, new images of killer whales working together to knock a seal off of an ice float have been released. A team of killer whales will rush towards an ice float causing a wave to appear that is powerful enough to knock an unsuspecting seal into the mouth of another member of their pod. They work together like this in many clever hunting situations displaying team work that some think is reinforced by their own ‘culture.’
Weddell seals are the preferred prey of apex predators as they are not as aggressive as crabeater and leopard seals, so the chance of injury by them is not as likely. Weddell seals measure between 8.2 - 11.5 ft. long and can weigh between 400 – 600kg. They are insulated with a thick layer of blubber which not only keeps them warm, but also attracts predators. Their energy rich blubber is vital for them to stay alive because food is so hard to come by. The weddell seal does have a few tricks for avoiding gaping jaws, which are also used when hunting for their own prey. They can dive to depths of approximately 2,300 ft. and can hold their breath for around 80 minutes! That’s a very long time to play hider or seeker!
The Frozen Planet team filmed the Adélie penguin stealing stones from neighbour’s nests to put in their own. Unfortunately for them, penguins make a tasty snack for seals and killer whales (but without the wrapper and bad joke – if you exclude that one!) Penguins may make up the bulk of a predators diet perhaps due to their sheer numbers, making them easier to locate. In the Ross Sea region of Antarctica, there are currently around 5 million Adélie penguins! This may make them an attractive option for many in such a harsh environment.
With these species featured (and I’m sure a lot more) together with the great camerawork from the BBC, I know what I will be doing on Wednesday nights!
By Haley Dolton
A new study has found that killer whales, also known as orcas, may be facing greater threats than previously thought. However, their cosmopolitan distribution, predatory nature and deep sea lifestyle have so far restricted accurate population size estimates.
The research suggests that killer whale populations are facing pressures from an invisible substance that has been building since the Second World War, at a time when industries were extensively using chemical flame retardants such as PCBs (polychlorinated biphenyls).
Killer whales feed on a variety of different organisms such as fish, seals, sharks and even juvenile whales. Despite their position as an apex predator at the top of the food chain, they are extremely vulnerable to changes in their prey. The main concerns to killer whale health stem from their prey being polluted by PCBs either by absorbing it from the water or by consuming polluted prey themselves.
According to Alex Rogers, a Professor in Conservation Biology at the University of Oxford, UK, studies have identified high levels of flame retardant chemicals in killer whales from both the Southern Hemisphere and Northern Hemisphere but particularly places such as Canada and the Arctic. Killer whales located near heavily populated areas and industrialised nations are most at risk from the effects of flame retardants such as PCBs.
Although PCBs were banned in the 1970's, their effects are still being observed. Dr Paul Jepson from the Zoological Society of London puts this down to PCBs being insoluble in water, only dissolving and accumulating in fatty tissues. This is a considerable issue for female cetaceans such as killer whales who feed their young for up to a year on high fat milk. It has been estimated that lactation in whales and dolphins transfers around ninety percent of the mothers PCBs especially into the first calf. Other effects of PCBs range from interference with thyroid function and vitamin A metabolism, to impairment of neurological and immune functions.
Despite the fact that PCBs have been identified as toxic it is still difficult to determine the actual cause of killer whale death and whether there are any pollutants in their bodies. Consequently, Marine Biologist Dr Ingrid Visser, has been studying a 200 strong population of killer whales around New Zealand which is under threat. This research hopes to reveal information on their behaviour and health which can be implemented in to a long term conservation strategy for the species. This study is vitally important as it will provide evidence on the extent of the PCB problem and whether killer whale populations are in decline.
By Anthony Kubale