The United Nations Educational, Scientific and Cultural Organization (UNESCO), United Nations Environment Programme (UNEP), the Convention on Migratory Species (CMS) and the Whale and Dolphin Conservation Society (WDCS) have declared 2007 the international year of the dolphin as part of the UN Decade on Education for Sustainable Development.
All about dolphins
Cetaceans are a group of aquatic mammals, including whales, dolphins and porpoises. Within this group, dolphins are classified as odontoceti or 'toothed whales'. There are two families of dolphins, the oceanic dolphins (Delphinidae) is the largest of all cetacean families with 32 species and includes dolphins, killer whales, pilot whales and relatives. The other family, the river dolphins (Platanistidae), contains just 5 species.
Oceanic dolphins occur in all seas (and, despite the name, in some rivers). They range in size from 1.5m to around 10 m in length, have streamlined bodies and are fast, agile swimmers. They feed largely on squid and fishes, which they actively pursue. The largest dolphin species, the orca also takes seals and other marine mammals. Dolphins tend to have a bulging forehead caused by the presence of the 'melon', an oval-shaped fatty structure thought to be used as an acoustic lens in echolocation, focussing the clicks that dolphins produce into a narrow beam of sound. Some of the sound bounces back, allowing the dolphin to calculate distance and build up a 'sound picture' of the surrounding objects. Some species are thought to stun their prey with high intensity sound. Dolphins are highly intelligent mammals that live in complex societies, with some members of this family living in very large groups.
Very little is known about river dolphins. They are the only freshwater cetaceans and tend to be relatively small, measuring between 1 to 3 meters in length, with a very slender elongated beak and a definite neck. They typically inhabit muddy water and rely on echolocation more than vision; over evolutionary time their eyes have become reduced in size as a result.
Threats facing dolphins
Many dolphins are endangered and face a suite of threats, including accidental by-catch by fisheries, habitat destruction, pollution, over-fishing (which reduces the availability of prey), ship strikes, underwater noise pollution (for example from military sonars), deliberate hunting and climate change.
Earthwatch dolphin projects
Earthwatch runs 11 exciting dolphin projects in stunning locations around the world, all of which provide a unique opportunity for volunteers to understand and contribute to the conservation of these enigmatic mammals in the company of top dolphin researchers.
This project provides Earthwatch volunteers with the opportunity to join Dr. Giovanni Bearzi and Joan Gonzalvo Villegas in the unspoilt Amvrakikos Gulf on the west coast of Greece. The aim of the project is to study the unusually high numbers of bottlenose dolphins in the area and to discover the main threats they face.
The Spanish Dolphins project has been running for 14 years; the results from this research were used to designate marine protected areas in 2002. This follow-up project, based in the Alboran Sea, where the Mediterranean joins the Atlantic, allows Earthwatch volunteers to work with Dr Ana Cañadas and Ricardo Sagarminaga van Buiten to ensure that the protected areas are effective, by informing management plans and running a long-term monitoring programme. Volunteers carry out research on a wooden Norwegian sailing vessel, recording species information, assisting with photo identification and filming the underwater behaviour of the dolphins.
As a participant on Whales and Dolphins of the Hebrides you will become part of the research team on board the research vessel Silurian alongside Dr. Peter Stevick and other staff members from the Hebridean Whale and Dolphin Trust. You will undertake a range of monitoring activities including photo-identification and acoustic monitoring using the latest technology, helping the scientists to identify 'hot-spots' for whales and dolphins in the area, which may become protected areas in the future.
The waters of the Moray Firth are fed by warm and cold currents from the Atlantic and Arctic Oceans; as a result they are particularly productive and rich in marine wildlife, being one of the important areas for whales, dolphins and porpoises in the whole of Western Europe.
By taking part in Dolphins and Whales of Moray Firth, volunteers can help Dr Kevin Robinson and colleagues from the Cetacean Research and Rescue Unit to collect essential data on the whales and dolphins of the Firth. Cetacean species in the area have, until now, been poorly documented, but are of high conservation priority.
The Dolphins and Whales of Abaco Island expedition is a long-term project based in the northeastern Bahamas that has been tracking marine mammals since 1991and provides the only comprehensive data on marine mammals in this area. Diane Claridge and Charlotte Dunn of the Bahamas Marine Mammal Research Organisation run this Earthwatch project. Volunteers take part in detailed observations of marine mammals, including a study of the local population of Atlantic bottlenose dolphin (Tursinops truncatus), which, compared to populations in other parts of the world, is relatively healthy. Information from this part of the project will therefore provide a 'yard-stick' to compare other populations in less pristine environments to. Gathering information on abundance, distribution, and seasonality of the marine mammals in the area will help to set up a conservation and management plan for the region, and to help mitigate the effects of military sonar on vulnerable deep-diving whales.
On this project, Earthwatch volunteers work alongside Dr Marcos Santos to study the little-known Marine tucuxi dolphin (Sotalia fluviatilis) in the Cananéia Estuary, São Paulo State, Brazil. The tucuxi dolphin (pronounced too-koo-shee) occurs as two subspecies, one of which, (S.f. fluviatilis) is found only in freshwater. This project focuses on the marine subspecies (S.f. guianensis).
On this expedition, volunteers join Dr Richard Bodmer on a journey down the Peruvian Amazon either to the Samiria River of the Pacaya-Samiria National Reserve or the Lago Preto Conservation Concession on the Yavari River to help carry out a detailed survey of the local wildlife. Both areas have staggering levels of biodiversity.
Volunteers assist with counting various species including river dolphins, giant river otters, monkeys, turtles, fish, giant river otters, macaws and other birds. Dolphins are a good way of determining the health of the river, as they are the area's top predators of species of fish. Decreases in dolphin populations can indicate over-fishing, long-term monitoring of the dolphin population will be used to evaluate the overall health of the river ecosystem.
Dr Daniela Maldini and Dr. Thomas Jefferson have been studying the bottlenose dolphin population of Monterey Bay for ten years. The project aims to establish how many dolphins live in the area, the status of the population and how behavioural aspects and the social interactions affect movement patterns. The population is so close to the shore that these dolphins are very likely to be affected by human activities. This project also carries out research into sea otters. Both the sea otters and the bottlenose dolphins are important indicators of the quality of the local marine environment.
Did you know?
Orcas (also known as killer whales) and pilot whales are dolphins.
All dolphins have two small rod-like bones in the pelvis, believed to be the remnants of hind legs. These rudimentary limbs are visible in dolphin embryos as tiny limb buds that disappear later on in development.
Dolphins are born tail-first.
In Laguna, Brazil, a remarkable example of human-dolphin cooperation has developed. The fishermen work as a team with the local pod of bottlenose dolphins. The men wait on the shore with their nets while the dolphins round up the fish and drive them towards the beach. The dolphins then roll onto their sides, which the fishermen take as their cue to throw the nets. Any fish that escape the nets swim straight into the mouths of the waiting dolphins.
Bottlenose dolphins in Shark Bay, Western Australia, tear off pieces of marine sponges and wear them on their snouts during foraging as a protective covering against stings and scrapes. This behaviour has been shown to be passed on from mother to daughter through teaching/ learning. Some scientists believe that this tool use represents a type of dolphin culture.
Cetaceans: whales, dolphins and porpoises
Biodiversity: the variety of life on earth.
Echolocation: detecting objects by means of interpreting reflected sound. Used for orientation and detecting and locating prey by bats, some birds and cetacea (whales, dolphins and porpoises).