The emperor penguin – caring parent, extreme survivor and unwitting movie-star – could be marching to extinction by the turn of the next century. In its Antarctic home, the penguins frequently have to deal with prolonged bouts of starvation, frosty temperatures of -40 degrees Celsius, and biting polar winds that blow at 90 miles per hour. And yet this icy environment that so brutally tests the penguins’ endurance is also critical to their survival. This is a species that depends on sea ice for breeding and feeding.
So what will happen to the emperor penguin as Antarctica’s sea ice shrinks, as it assuredly will in the face of a warming globe? Stephanie Jenouvrier from the Woods Hole Oceanographic Institution have tried to answer that question by combining the forty years of census data on a specific emperor colony with the latest models from the Intergovernmental Panel on Climate Change (IPCC).
The results are not encouraging. They suggest that the number of emperors in a large colony at Terre Adelie (where March of the Penguins was filmed) will fall from about 6,000 breeding pairs at the moment to a mere 400 by 2100. There’s even a one in three chance that the population will drop by 95%- a level described as “quasi-extinction”, when the population is so small that it’s unlikely to sustain itself.
Image copyright of Samuel Blanc
Some of us have enough trouble finding the food we want among the ordered aisles of a supermarket. Now imagine that the supermarket itself is in the middle of a vast, featureless wasteland and is constantly on the move, and you begin to appreciate the challenges faced by animals in the open ocean.
Thriving habitats like coral reefs may present the photogenic face of the sea, but most of the world’s oceans are wide expanses of emptiness. In these aquatic deserts, all life faces the same challenge: how to find enough food. Now, a couple of interesting studies have shed new light on the tactics used by predators as large as sharks and as small as bacteria.
At a large scale, predators like sharks and tuna rely on chemical cues to give away the location of their prey. Sharks are particularly expert trackers, but powerful though their super-senses are, they can only come into play within a certain range. Over the large distances of the open ocean, they are more like blind hunters, hoping to stumble across some telltale sign of food.
David Sims from the UK’s Marine Biological Association found that many large marine predators use a search strategy called a ‘Levy walk’, although in this case it’s more of a swim. The strategy is formally described by a mathematical equation, but in simple terms, it means that an animal makes several short moves in its search for food, interspersed with a few long ones. The longer the ‘step’, the more infrequent they are.