Dolphins have been a mystery and a source of fascination for humanity for thousands of years.
These amazing animals are members of the order Cetacea or toothed whales.
They may belong to the more commonly known family Delphinidae, including all oceanic dolphins, or the family Platanistidae, including the river dolphins.
More than 40 species of dolphins live throughout the world’s oceans and rivers.
These mammals vary greatly in size, ranging from 4 to 30 feet and their weight ranging from 88 lbs. up to 22,000 pounds.
The largest dolphin families are referred to as whales.
This includes the killer whale, false killer whale, and pilot whale.
Conversely, the world’s smallest dolphins, commonly called Hector’s dolphins, include a subspecies called Maui’s dolphin.
These dolphins live off the coast of New Zealand, and the average adult weight of these small mammals is 88 to 132 pounds (40 to 60 kilograms).
They have an average adult length of 3.8 to 5.3 feet (1.2 to 1.6 meters).
Other small dolphins include Heaviside’s dolphins, which weigh 132 to 154 pounds (60 to 70 kilograms) and are about 5.6 feet (1.7 meters) long when they reach adulthood, and acrobatic spinner dolphins, which weigh 130 to 170 pounds (59 to 77 kilograms) and measure about 6.6 feet (2 meters) in length as adults.
Another small dolphin is the Indus river dolphin; as an adult, this dolphin weighs about 150 to 200 pounds (70 to 90 kilograms) and measures 7.5 to 8.5 feet (2.3 to 2.6 meters) long.
The bigger, more moderate-sized dolphins include the popular bottlenose dolphin, which as an adult weighs 331 to 442 pounds (150 to 200 kilograms) and measures 6.6 to 12.8 feet (2 to 3.9 meters) in length, and the striking Pacific white-sided dolphin, which weighs 300 to 400 pounds (135 to 180 kilograms) and measures 5.5 to 8 feet (1.7 to 2.5 meters) in length when it reaches full maturity.
The Atlantic spotted dolphin, which as an adult weighs 200 to 315 pounds (100 to 143 kilograms) and measures 5 to 7.5 feet (1.6 to 2.3 meters) in length, is another dolphin in the middle-weight class.
One of the larger marine mammals is Risso’s dolphin, also known as Grampus.
This animal, which has been spotted offshore in warm temperate and tropical waters worldwide, weighs 660 to 1,100 pounds (300 to 500 kilograms) and measures from 8.5 to 13 feet (2.6 to 4 meters) long when it has reached adulthood.
Among the dolphins that are called whales is the short-finned pilot whale.
An adult can weigh anywhere from 2,200 to 6,600 pounds (1,000 to 3,000 kilograms) and can measure from 12 to 18 feet (3.7 to 5.5 meters) in length.
Finally, the largest dolphin is the killer whale or orca.
An adult female orca can weigh in at a whopping 16,500 pounds, and the male can weigh up to about 22,000 pounds (a range of 7,500 to 10,000 kilograms).
Female orcas measure about 28 feet (8.5 meters) in length, and males are about 32 feet (10 meters) long at their largest.
What about the size?
As with determining their weight, determining the overall size of dolphins can be a difficult task because there are numerous species, and each species of dolphin has characteristics that make them unique from other dolphin species.
However, we can look at a couple of dolphin species to give you a general idea of these differences in regards to size and weight.
The smallest known dolphin is Maui’s dolphin, known to grow to lengths of around 5 1/2 ft. long at full maturity and weigh slightly over 100 lbs.
This dolphin is a rare dolphin species that can be found near the shore of North Island in New Zealand. In comparison, the largest known dolphin is the killer whale, which can grow up to 30 ft. long and weigh as much as 12,000 lbs.
Unlike Maui’s dolphin, the killer whale can be found throughout various oceans worldwide.
While not always the case, size can directly influence where dolphins can live throughout the world.
For example, some smaller species of dolphins can be found traveling in and around coastal waters where they are less likely to face threats from potential predators.
In contrast, larger dolphins may venture out further into the offshore ocean, far from coastal waters.
Predators for the dolphin species may include killer whales and sharks, and yes, killer whales hunt other dolphin species for food.
Size can also play a role in the dolphin’s ability to stay warm in cold climates.
Larger species of dolphins are better able to displace heat throughout their body while using fewer calories to do so.
Killer whales, for example (the largest of the dolphin species), can be found traveling throughout the Arctic and Antarctic waters.
In contrast, Maui’s dolphin and the popular bottlenose dolphin prefer to stay in warmer climate waters.
In addition to staying near coastal environments, small dolphins are also known to travel in large groups to protect themselves from predators.
Depending on the dolphin species, dolphins are known to consume anywhere from 2% – 10% of their body weight in food daily.
Lastly, size does not always determine the types of food a dolphin is likely to eat.
While it is true that the killer whale can consume a variety of marine mammals as well as fish and squid, most dolphins stick to a diet that consists of fish, squid, octopus, and various crustaceans regardless of their size.
Since all dolphin species possess echolocation, they can use this essential ability to navigate the ocean, search for prey and get an early warning sign for nearby predators looking to turn them into a meal.
By combining their excellent sense of hearing with the use of echolocation, dolphins are both excellent hunters and navigators, making them one of the most advanced aquatic animals alive today.