Penguins come in all shapes and sizes, from the curiously named Macaroni Penguin to the unrelentingly adorable Gentoo penguin. They are found in a range of habitats; not just the Antarctic but South Africa, New Zealand and even the Galápagos Islands are home to a variety of the aquatic, flightless, waddling birds. Penguins are fairly unique, but they do have something unfortunate in common with many other animals: they are likely to be detrimentally affected by man-made climate change. A new study in Nature Communications reveals that the king penguin will find it more difficult to forage for food if the planet continues to warm.
Climate change is an incredibly complex phenomenon, with hundreds of inputs and an almost indeterminate number of effects on the planet, from environmental to the socioeconomic. Animal populations experience the rapidly changing climate in very different ways, but the take home message is that the climate is changing too quickly for them to be able to adapt to it. Consequently, many species are dying out, with every one in six on the planet threatened by man-made climate change. King penguins appear to be no exception.
The king penguin is a key marine predator, and thus any reduction in its numbers can lead to the destabilization of a marine ecosystem. These penguins are accomplished divers: they are able to reach depths of more than 240 meters (790 feet), and although they appear similar to their slightly larger relatives – the emperor penguin – they live in the warmer regions of the subantarctic.
Between 1992 and 2010, the researchers tagged a range of king penguins and followed their every movement, from their colonies to the open ocean, in order to investigate the effect climate extremes have on their lives.
The climate in both the subtropical and subantarctic regions is primarily controlled by cyclical events called “subtropical dipole events”. Essentially, climatic zones are described by poles: one side of the region (one of the “pole” points) is temporarily warmer than the opposite side (or “pole” point), which at some point recedes. There are multiple subtropical dipole events that can occur simultaneously in different parts of the world, including the subantarctic, the king penguins’ habitat.
These large-scale climate variabilities normally cause significant fluctuations in the sea surface temperatures of the Southern Indian Ocean. However, particularly strong events drive these warmer waters farther south towards the polar frontal zone, the area the king penguin prefers to forage in.
Their food source, a variety of fish, tends to accumulate at a water depth known as the thermocline, the layer at which the temperature difference between the upper and lower sections of the water column is most extreme. During strong climate events, the thermocline deepens, meaning that the penguins sometimes have to dive nearly 31% deeper than normal at greater distances from the colony. This entirely unfavorable altered marine environment has a powerfully negative effect on the king penguin colonies: they spend more time and energy finding less food. On one occasion, the king penguin breeding population experienced a decline of 34%.
Although the study focused on natural climate anomalies, the researchers state that the current trend of warming sea surface temperatures caused by recent climate change will only serve to further hamper the king penguins’ effort to forage for food.
