Dolphin Research Around the World

The Franciscana or La Plata dolphin (Pontoporia blainvillei) is among the world's smallest and most endangered dolphins. Adults are roughly 5 feet long and weigh about 100–120 pounds. Native to the coastal waters of Argentina, Uruguay, and Brazil, they usually travel in groups of one, two, or three animals. They face many human-caused threats, such as death from entanglement in fishing nets, habitat degradation, and fragmentation by pollution and overfishing.

Defining population units is crucial for appropriate, effective management. Such definition can come from repeated observations of distinctive individuals, or from tracking individuals. Franciscana dolphins lack the distinctive natural markings that would allow photographic identification, so radio tracking was determined to be the best starting point.

It is a member of the river dolphin group and the only one that actually lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems.

Dr. Janet Mann has studied dolphins that live in the Monkey Mia area of Shark Bay, Australia, a World Heritage Site. She has concentrated her studies on more than 115 calves born to 81 mothers in the region. She is generally interested in why bottlenose dolphins have such slow life histories, why females invest substantially in each calf, and what factors predict female reproductive success.

Social experience is obviously important, but before a calf can be weaned, the calf must learn to hunt for itself. This is no easy task. Calves begin foraging in the first year, but must develop highly specialized skills for finding, capturing, and processing prey. More than 13 foraging types have been identified, and each adult female has a distinct foraging profile.

Monkey Mia is a behavioral research site for bottlenose dolphins and tiger sharks and often works in collaboration with the West Australian government. Dolphin research includes male association, female to calf association, and juveniles.

A freshwater dolphin found only in China is now "likely to be extinct," a team of scientists has concluded. The researchers failed to spot any Yangtze river dolphins, also known as baijis (Lipotes vexillifer), during an extensive six-week survey of the mammals' habitat. The team blamed unregulated fishing as the main reason behind their demise. If confirmed, it would be the first extinction of an aquatic mammal for over half a century, and the first large mammal made extinct by environmental degradation.

August Pfluger, head of the Zurich-based Baiji.org Foundation, which co-sponsored the six-week, 2,000-mile survey of the Yangtze without finding a single remaining member of the critically endangered species, told Time magazine: "The main reason is overfishing. The Chinese still use unsustainable fishing methods like dynamite. There's still a lot of illegal fishing, so the dolphins were competing with humans for food."

Damming on the river and noise from heavy boat traffic may have contributed by disorienting the dolphins, which are mostly blind and use echolocation to find food.

Dr. Sam Turvey of the Zoological Society of London, one of the paper's co-authors, described the findings as a shocking tragedy. "The Yangtze river dolphin was a remarkable mammal that separated from all other species over 20 million years ago," Dr. Turvey explained. "This extinction represents the disappearance of a complete branch of the evolutionary tree of life and emphasizes that we have yet to take full responsibility in our role as guardians of the planet."

The white-beaked dolphin (Lagenorhynchus albirostris) is one of the least studied cetaceans in the North Sea, and very little is known about it.

The research area is an area between Skagen Reef and the Norwegian Trench, also called the Orion Belt. The Orion Belt is a very important ecological area. The depth in the Orion Belt varies between 50 and 700 meters. It is an extremely fertile area, where winter storms press the cold and relatively salty North Atlantic currents into the warmer and less salty waters of the North Sea.

This process brings water from the bottom layers toward the surface, where photosynthesis is the basis for the growth of plant plankton, which is the basis for animal plankton, which is the basic food supply for fish, which are eaten by dolphins.

The Orion Belt is the area, within the Danish waters, where most sightings of cetaceans are registered; many of them are sightings of white-beaked dolphins.

Russian researchers have recorded the sounds audible only inside the right part of the dolphin's nasal passage. Animals produce them during echolocation. This research can shed light on how the cetacea produce ultrasonic signals.

Researchers of the Severtsov Institute of Ecology and Evolution Problems, Russian Academy of Sciences, have obtained the confirmation of the hypothesis that the cetacea, dolphins in particular, produce sounds with the help of some pneumatic mechanism, i.e., by driving air under pressure in the depths of the organism. It is assumed that the animals' right nasal passage is involved in the production of sounds.

The point is that dolphins turn out to be capable of producing special internal sounds, but the sounds can be heard only during echolocation. These sounds are called "internal," as they are not heard on the outside (the researchers have managed to make out the sounds only with the help of special internal sensors). They can be heard only in a single location—in the right part of the dolphin’s nasal passage.

According to the researchers, these sounds resemble whistles or meowing. The frequency and other properties of these sounds differ significantly from the so-called communicating whistle, which the dolphins use to communicate with each other.

For nearly 40 years, Dr. Randy Wells, senior conservation scientist for the Chicago Zoological Society, and his team have studied the resident population of bottlenose dolphins (Tursiops truncates) in Sarasota Bay, Florida. This is the longest-running wild dolphin study in the world.

The team has learned what it takes for this coastal population to survive and thrive despite the pressure of expanding human activities in the coastal ecosystem.

Recent harmful algae blooms impacted fish populations, which, in turn, impacted the dolphins. The Sarasota research team is working with local communities to prevent disastrous interactions between dolphins and recreational boats and fishing gear.

» Read about dolphin research at the National Aquarium here.