The polar regions are among Earth’s most unique environments 

Characterised by low temperatures, limited food availability, harsh climates and extreme seasonality, it’s challenging to live in the polar regions. Species inhabiting the Arctic and Antarctic have evolved various physiological, morphological (structural), and behavioural adaptations to survive in these challenging conditions.

Where is the Arctic? Where is the Antarctic? 

The Arctic is in the Northern hemisphere whereas Antarctica is in the Southern hemisphere.

Iconic Arctic species include the polar bear, Arctic fox, narwhal, walrus, and bearded seal.  

In contrast, the Antarctic is home to species such as the leopard seal, Emperor and Adélie penguins, and rock ptarmigan (a medium-sized game bird). 

Slow and steady is key to survival. 

Temperature has a major impact on how fast species develop. A pattern of slow development rates has been observed among Antarctic marine ectotherms (species that rely on the environment to regulate their body temperature). 

For example, the development rates of marine larvae are slower at low temperatures compared to those in temperate and tropical regions. This is likely due to lower temperatures reducing protein synthesis and folding, resulting in fewer functional proteins available for growth.  

With the close link between metabolism and development, polar species tend to have slower metabolic rates and use up minimal energy. Antarctic Nototheniodei fish, for instance, have evolved with reduced quantities of red blood cells and haemoglobin , the protein responsible for transporting oxygen throughout the body.

This reduction in haemoglobin reflects their lower metabolic rates and oxygen demands compared to species in warmer, temperate climates.  Slow metabolism and development are key to surviving with the limited food available in the polar regions.  

How species cope with food scarcity in the polar regions 

The polar regions experience dramatic seasonal shifts in solar radiation, with continuous daylight in the summer and nearly total darkness in the winter.  

This is accompanied by blizzards, freezing temperatures and limited food availability.  

During winter, reduced sunlight limits the growth of primary producers like phytoplankton and plants, which in turn affects the entire food chain. Additionally, the sea ice that forms over the Ocean restricts access to open water, where many marine animals feed. Snow cover makes it more challenging for land animals to access their food sources.  

For some animals, these harsh winter conditions are too extreme, and they migrate to more favourable areas. For those that remain, many build up fat reserves during the summer and early autumn to prepare for the limited food availability.  

In the Svalbard rock ptarmigan, for example, these fat reserves are primarily used during episodes of acute starvation rather than supplementing daily energy needs.

Some animals also exhibit surplus killing and hoarding behaviour in the summer, such as the Arctic fox. The fox has been observed storing food, with one cache containing as many as 136 seabirds.   

Many animals will limit physical activity to conserve their energy and reduce their resting metabolic rate. This refers to the amount of energy the body uses at rest to maintain basic physiological functions.

Adult King penguins can go without food for up to one month. Meanwhile, chicks can endure fasting for up to five months during the subantarctic winter, losing up to 70% of their body mass while relying mostly on stored fat reserves. 

Small invertebrates that live on the seafloor, or meiofauna, have adapted to polar environments by feeding on degraded organic matter, which remains available year-round.  

In many Arctic marine mammals, the milk produced for their young is exceptionally rich in energy and nutrients, which is vital for the pups to survive in the harsh, cold environment.  

How species cope with freezing temperatures 

Air temperatures in the polar regions can occasionally drop to -60°C, while Ocean temperatures are close to freezing. To maintain a stable core temperature, organisms must employ strategies to minimise heat loss through conduction, convection, radiation, and evaporation. 

One common adaptation is the evolution of a rounded body shape to reduce exposed surface area. For instance, walruses have a large, tubular body with minimal projecting extremities, such as visible ears or a tail, reducing heat loss through conduction and convection.  

Many polar species develop dense fur for insulation, such as reindeer and caribou (also a species of deer), whose hollow guard hairs provide air-filled cavities for additional warmth. In marine animals, where fur offers little insulation value, a thick layer of blubber becomes essential for protection against cold seas. It also serves as a food reserve.

Many species have evolved sophisticated blood flow regulation systems in body parts exposed to the cold. In marine mammals, a network of blood vessels in the flippers operates as a counter-current heat exchange system. This is when warm blood flows to the flipper transferring heat to cooler blood returning from it. This adaptation allows them to conserve heat in critical areas while maintaining functionality in their extremities. 

Moreover, both Arctic and Antarctic fish have independently evolved antifreeze glycoproteins, which are secreted into their blood to prevent the formation of harmful ice crystals. These compounds are produced during the cold winter months in Arctic fish and year-round in Antarctic fish. 

Behavioural adaptations also play a key role in survival 

Emperor penguins form large huddles in extreme Antarctic cold and wind, with groups consisting of hundreds of individuals. The penguins take turns occupying the warmer centre of the huddle, where ambient temperatures can reach 37.5°C, helping conserve energy and incubate eggs during the winter.  

Snow place like home 

Survival in the polar regions requires a combination of physiological, morphological and behavioural adaptations, enabling species to endure extreme cold, limited food availability and harsh climatic conditions.  

As climate change continues to alter these environments, the ability of polar species to adapt will be crucial for their ongoing survival in an increasingly warming world. 

Check out How Climate Change threatens polar species: Polar bears, Orcas and Narwhals, where we discuss the opportunities and challenges for animals in a changing world.  

Post by

Thi Nguyen

With torpedo-shaped bodies, forked tails, and dorsal fins, sharks belong to a group known as cartilaginous fishes (meaning their skeleton is made from cartilage, not bone).

As one of the oldest evolutionary groups, the earliest fossil evidence for sharks or their ancestors’ dates to 400 – 450 million years ago. 

This means that the earliest sharks may have been around before trees even existed (trees evolved around 360 million years ago).  

What makes sharks unique?  

Sharks are one of the most diverse groups of predators in the animal kingdom. They come in all shapes and sizes. Sharks can have huge, gaping mouths (like the basking shark), long whip-like tails (like the thresher shark) or flattened, club-like heads (like the hammerhead shark).  

The largest species is the whale shark, reaching lengths of 20m. The smallest is the dwarf lanternshark which grows to just 20cm long. 

It’s this diversity in shape, size, feeding mechanism and habitat that has enabled sharks to persist throughout all parts of the Ocean over millions of years.  They even live in some freshwater environments.

Why are sharks important?  

Sharks can play many roles in ecosystem functioning: from predators to prey, competitors, and nutrient transporters.  

Some species of shark are apex predators, meaning that they’re at the top of their food chain and exert a top-down control on food webs. Others can sit further down the food chain, yet still play an important role as food for other predators and transporting energy through ecosystems. 

Large scale movements and migrations of sharks also connect even the most widely spaced food webs, transporting nutrients across the open Ocean system.  

Unfortunately, sharks are heavily misunderstood. 

Media and popular culture often demonise sharks, portraying them as senseless killers through sensationalistic headlines and striking imagery. This is designed to incite fear, leading us to believe that the threat posed by sharks is greater than it really is.   

Did you know? Our fear of sharks originates from the ‘Jaws Effect’. It’s the powerful influence of the famous 1975 Hollywood thriller on our human perception of risk from sharks. 

Put simply: Few animals are feared more than the shark.

But in reality, sharks have much more to fear from us than we do them.  

The probability of a shark biting a human is very low compared to many other risks that people face in their everyday lives. According to the International Shark Attack File, there were 69 unprovoked shark bites, including 10 unprovoked shark-related deaths globally in 2023.

To put this into perspective, on average, 500 people are killed by elephants each year.  

Sharks don’t actively hunt humans. The most common shark incident is known as a ‘test bite’. It means sharks swim away after a single bite once they realise it’s not their preferred prey. Surfers and other board sports make up 42% of reported incidents, as the shape of their boards can bear a resemblance to seals and other prey from below.  

When we do encounter sharks, it’s often because their natural behaviour clashes with our activities, from fishing to recreation.

In contrast, the global population of sharks and rays have plummeted by over 70% over the past 50 years. 

The pressure on shark populations continues to rise. At least 80 million sharks are killed each year and over 1/3 of all shark and ray species now threatened with extinction. 

To put that into perspective, there are only 19 countries in the world whose population is greater than 80 million. As of 2024, the number of sharks killed each year exceeds the total population of Thailand (71.8 million), the UK (68.3 million), and France (68.1 million).  

Sharks are particularly vulnerable to overexploitation.  

They grow slowly and take a long time to reach sexual maturity.

Shark mothers put a significant amount of energy and time into the development and care of their offspring. They also take extensive rest periods between pregnancies.  

This makes sharks far less resilient and slower to recover from disturbance and overexploitation than other fish species.

Overfishing is the greatest threat to shark populations worldwide.  

The 70% decline in shark and ray populations is largely attributed to an 18-fold increase in fishing pressure over the past 50 years.

A key incentive for shark fishing is the Shark Fin Trade. This is the practice of removing the fins from a captured shark and discarding the rest back into the Ocean. Shark fins have become one of the most valuable seafood products worldwide, and this globalised market exists largely to meet the demand for the traditional dish: shark fin soup.

However, despite widespread legislation designed to prevent shark finning in recent years, fishing pressure and shark mortality continues to rise.  

Restrictions surrounding the practice of shark finning has driven up the appetite for shark meat. It’s because it’s often only illegal to land fins with the shark removed, not the whole animal. As a result, largely unregulated fisheries in the high seas continue to put pressure on global shark species. 

These markets are muddied by misidentification (often of protected or endangered species). For example, in Brazil, the meat is labelled “cação”: an umbrella term under which both shark and ray meat are sold. 

This lack of transparency leads to consumers being poorly informed, and they often aren’t aware that the animals on their dinner plate are at risk of extinction.

Scientists used satellite tracking to discover that about 24% of the area sharks use each month overlap with large-scale industrial fishing zones. This means that many shark species in the open Ocean spend almost ¼ of their time under the looming shadow of large-scale fishing fleets. 

Climate change compounds these threats.

The Ocean’s oxygen minimum zones (naturally occurring areas of open Ocean low in oxygen) have expanded horizontally and vertically. This is due to higher temperatures and changing circulation patterns associated with climate change.  

The expansion of these oxygen minimum zones has caused the habitat of oceanic sharks to be compressed towards the surface, since they can’t survive in low oxygen conditions.  

Species like the blue shark are being pushed closer towards intense surface fisheries as a result, making them more vulnerable to being caught as bycatch.

Despite the alarming statistics, it’s not all bad news for sharks. 

In the northwest Atlantic, the white shark appears to be recovering after a 70% decline over the past 50 years, and hammerhead shark populations are also rebuilding here. This success is owed to strictly enforced fishing bans and quotas throughout their range.

This gives us hope that the successful implementation and enforcement of science-backed management across a species range can reverse shark population declines. 

To protect sharks, we need to change the way we think about them.  

Our irrational fear of sharks is limiting support for their conservation. 

When we portray sharks in a negative light, our sense of risk becomes heightened. This leads people to believe that extreme mitigation measures such as culling are not only appropriate, but necessary.  

This fear also diverts our attention away from the species which are at the highest risk of extinction and ignores the ongoing threats to sharks and their habitats.  

Sharks have survived all five previous mass extinction events. For them to survive the sixth, we must re-evaluate our perceptions of them and show our support for the conservation of these magnificent creatures.  

Post by

Jemma Sargeant