Water temperature is one of the most powerful environmental factors determining where a shark lives, influencing nearly every aspect of its life from metabolism to migration. Because most shark species are ectotherms, meaning their internal body temperature mirrors that of the surrounding water, they must remain within specific thermal boundaries to function properly. The distribution of over 500 shark species worldwide reflects their individual physiological tolerance limits to ocean temperatures. Sharks represent a spectrum of species adapted to habitats ranging from the tropics to the polar seas.
Categorizing Shark Thermal Preferences
Tropical Species
Sharks can be broadly classified into groups based on the range of temperatures they prefer and tolerate, which dictates their global distribution. Tropical or warm-water species, such as the Nurse Shark and the Tiger Shark, thrive in consistently warm seas, typically between 21°C and 30°C (70°F and 86°F). These species often remain in their warm-water comfort zone year-round. The Bull Shark also favors warm conditions, generally between 20°C and 28°C (68°F and 82°F), but shows a greater adaptability that allows it to venture into various coastal environments.
Temperate and Cold-Water Species
In contrast, temperate and cold-water species are adapted to much cooler conditions, with some preferring waters in the range of 10°C to 21°C (50°F and 69.8°F). The Spiny Dogfish, for example, is a cold-temperate shark often found in waters between 7°C and 24°C, spending much of its time in deep, offshore locations. At the extreme end is the Greenland Shark, a polar species that lives in frigid waters consistently below 5°C (41°F) and is adapted to exist under ice floes.
Eurythermal Species
A third group consists of eurythermal species, which tolerate a wide range of temperatures, often because they are highly migratory. Many of these species, like the Blue Shark, move vast distances to follow seasonal temperature gradients. These migratory sharks, including the Great White Shark and Shortfin Mako, often pass through both warm and cool regions, demonstrating a flexibility in their thermal habitat.
Temperature’s Impact on Shark Biology
The direct link between water temperature and a shark’s body temperature fundamentally governs its internal biology, particularly its metabolic rate. For most sharks, an increase in surrounding water temperature leads to a significant rise in their metabolic demand, meaning they require more oxygen to sustain basic functions. This means a tropical shark in 30°C water must consume more energy than a cold-water shark at 10°C.
This temperature-driven increase in metabolic rate can create a challenge because warmer water holds less dissolved oxygen than cooler water. Coastal sharks with high metabolic rates, such as the Blacktip Shark and Bull Shark, are particularly susceptible to this balance between their rising oxygen demand and the decreasing environmental supply. This combination of warm water and low oxygen can restrict the usable habitat for highly active species.
Regional Endothermy
A small number of highly active sharks, including the Shortfin Mako and Great White Shark, possess a physiological advantage that allows them to maintain a core body temperature several degrees warmer than the surrounding water. They achieve this by using a specialized network of blood vessels that conserves the heat generated by their swimming muscles. This “warm-bodied” trait allows them to sustain higher muscle power and faster swimming speeds, even when hunting in cooler waters. The ability to keep their internal temperature relatively stable makes these species less dependent on external temperature shifts, giving them a wider foraging range.
Thermal Regulation and Migration Patterns
For the majority of sharks, large-scale movement is the primary strategy for maintaining an optimal thermal environment. Seasonal migration is a behavioral response to temperature gradients, with many temperate species moving poleward toward cooler waters in the summer and equatorward to warmer waters in the winter. For instance, the annual migrations of Tiger Sharks have been observed to expand further poleward as ocean temperatures rise, indicating a shift in their distribution to keep pace with their preferred habitat.
Sharks also use vertical movements in the water column to regulate their temperature on a daily basis. This behavioral thermoregulation involves diving to cooler depths or ascending to warmer surface waters. Oceanic whitetip sharks, for example, frequently oscillate in the upper water column, but when surface temperatures become very high, they increase the amplitude of their dives to spend more time in deeper, cooler water.
This vertical movement strategy is also employed by warm-bodied sharks like the Shortfin Mako, which may dive to cooler depths to avoid overheating in extremely warm surface layers. Other species, like the Whale Shark, exhibit “thermal diving,” briefly plunging into colder, deeper layers. Researchers believe this may help them regulate their body temperature while accessing prey-rich zones before returning to the warmer surface. These depth changes allow sharks to exploit a wider range of the ocean while minimizing the physiological stress of prolonged exposure to suboptimal temperatures.