Dolphins are part of a group of marine mammals called Cetaceans, which also include whales and porpoises. Apart from the Sirenians (commonly known as sea cows), that include the dugongs and manatees, Cetaceans are the only group of wholly marine mammals that never come on to land. There are at least 39 known species that form part of the suborder Odencti; meaning toothed whale and the family Delphindae. Within Delphindae, there are six species commonly thought of as ‘whales’ such as the killer whale (Orcinus orca); but in fact, killer whales are dolphins. They are descendants of land-living mammals that returned to the sea some ten million years ago and have since adapted well to their marine environment.
Whales and dolphins are sentient, social and intelligent animals. Their wild behaviour demonstrates high intelligence through their ability to communicate with each other in the form of a ’language’. For example, bottlenose dolphins (Tursiops truncates) studied in the wild, have demonstrated the ability through individual ‘whistles’ to recognise other members in their group. This is so they can address each other individually; a form of communication that no other non-human animal has demonstrated.
One of the biggest threats to the marine environment is man; the human population is growing at a rapid rate and is consequently becoming increasingly industrialised. Worldwide ocean habitats are being modified either by removing organisms for food, releasing toxic waste through development, or direct habitat destruction. Anthropogenic (human induced) noise from vessels and military procedures are thought to disrupt the hearing of a number of species as well as the effectiveness of echolocation (biological sonar used to locate and identify objects in the water). Potentially, this could affect aspects of their lives such as finding food, navigating or socially interacting. Vessels also increase the risk of damage through collisions, causing injuries or disease via release of pollutants. Inappropriate disposal of toxic human products on coastlines has also caused concern. For example, exposure to polychlorinated biphenyls (PCBs are chemicals found in coolant fluids, cement and paint), have been linked to health and reproductive problems in dolphins. In 2011, a study undertaken in Cornwall, England, linked a decline in bottlenose dolphins with the increase use of PCBs, causing a lowering in the immune system, with one dolphin possessing the highest PCBs levels ever recorded in the species within the UK over the last 20 years.
Destruction of suitable habitat through the building of coastal resorts or altering the water flow of rivers, results in local species becoming increasingly vulnerable due to their minimal distribution. In China, the Baiji Dolphin (Lipotes vexillifer), is now believed to be extinct due to its limited range and development on the Yangtze River banks, coupled with increased fisheries in the area. Fisheries are an increasing threat for all marine species and incidental intakes of up to 27 million tons of non-target marine life is recorded each year. As well as being caught as by-catch (accidental catch), dolphins are also susceptible when commercial fisheries are fishing for tuna. This is because some species of tuna congregate with dolphins for protection from sharks, and are therefore caught with the target catch.
The impacts can be both directly through bycatch and indirectly, through loss of prey species. Despite a lack of extensive scientific research, the assumption that dolphins compete with fisheries for prey has prompted many culls, including a commissioning by the Icelandic government in 1956 to use explosives to cull local populations of killer whales.
Despite the seemingly positive relationship humans have with dolphins, every year more than 20,000 small whales, dolphins and porpoises are killed off the coast of Japan and the Faroe Islands. One of the methods used is drive hunts, where large groups of animals are rounded up using boats and driven towards the shore and trapped in a bay using nets, before being killed for their meat or sold to marine parks. The consumption of dolphin meat is not a huge market in the UK, but many other countries have a black market in the sale of chancho marino, fresh dolphin meat that is very red with white fibre. After the meat has been exposed to air and dries out, it turns black, known then as muchame; this is served as a salty delicacy in many South American countries and especially prevalent in Peru. With buyers offering around $17 a kilogram for the meat, an average-sized dolphin can fetch approximately $340 and this is around the same amount as a Peruvian schoolteacher or police officer makes in a month.
Along with demand for dolphin meat, there are also a growing number of facilities holding whales and dolphins in captivity for display to the public in entertainment style shows and interaction programmes such as ‘swim-with-dolphins’ and also Dolphin Assisted Therapy (DAT). The public display industry, known as ‘Dolphinaria’ has asserted for many years that the display of marine mammals serves a necessary educational purpose, and furthermore promote themselves as conservation enterprises. These facilities maintain that the animals’ welfare is not compromised, however, there is a growing amount of evidence to suggest that captive Cetacea are adversely affected by their captive environment, causing stress, aggression, and reduced life expectancy.
The importance of dolphins and why we should care
Dolphins are one of the most intelligent animal species on Earth. They are curious and playful and have impressive communication skills. Dolphins enable us to relate to nature in an incomparable way. The history of dolphin-human interactions is long standing, complex and unique in the animal world. Even without the enticement of food, it’s not unusual for dolphins to initiate social contact with humans. Few wild animals are featured so prominently, or so positively, in human mythology, art, architecture, literature, anthropology, history and also in the media. There are well documented cases of dolphins rescuing humans and defending them against shark attacks. In some areas, they have been known to help traditional fishermen locate and net their catch. In recent years, an exponential rise in dolphin ecotourism has occurred, with more people prepared to spend time and money on watching these extraordinary animals in their natural environment. This has proven to be an essential income for the tourist sector of many countries. A small village in Tanzania has seen a huge increase in ecotourism over the last seven years. Whereas they previously hunted dolphins for use as bait, they now recognise the long economic worth of conserving dolphin populations, rather than the short term harvest profits.
Dolphins are one of the top long-living predators, but sensitive to human disturbance and environmental change. Therefore, they can be a significant indicator species for the health of marine ecosystems. As top-level predators, dolphins play a part in the control of fish and squid; therefore keeping the ecosystem in balance. Also, contaminants can be concentrated in their bodies from the water which could endanger other marine life, including that of human health. It has been suggested that the consumption of dolphin meat is like eating poison due to the bioaccumulation (highly concentrated levels) of the heavy metal mercury, which dolphins are able to store in their muscle.
The solution: what we can do
Although not all dolphins are endangered, many individual populations have seen a decline in recent years. To survive, dolphins need clean and quiet oceans, protected areas and enough people to care. Furthermore, it is essential that there is co-operation between the public and conservation. In countries with poor economies, financial incentives to protect dolphins must be greater than the incentives are for killing them for meat, or for the dolphinaria trade. There is a great potential for whale and dolphin watching as an alternative source of income for local fishermen. Eco-tourism is a sustainable way for fishermen to make a living; with the average life-span of a dolphin being over 50 years (and 80-years for a killer whale).
There also needs to be increased regulations for many dolphinariums which do not hold the same standards as many modern facilities in Western countries. Some are successful at engaging with the public and increasing their awareness of conservation, as well as providing a platform to conduct scientific studies which cannot easily be done in the wild. However, when visiting such facilities, it is important to consider that it’s largely impossible to maintain an environment adequate enough to meet the complex needs of large marine mammals compared with those living in the wild. Generally, the contribution to conservation from any captive animal facility is limited and these facilities raise more issues in relation to welfare, than provide any real benefit to conservation.
A lot of western countries have higher standards when it comes to protecting marine mammals, however, this is not always the case in other parts of the world, as these animals may not be perceived in the same way. Increasing media awareness of their plight is essential. In 2009, a critical documentary on the drive hunts in Japan titled ‘The Cove’ was released by former Flipper dolphin trainer, Ric O’Barry. The film highlighted for the first time the main method of acquiring dolphins and whales for the dolphinaria industry. Dolphins not selected are killed for their meat. Awareness can be raised through effective campaigning and petition signing, or even as little as discussing these issues with friends and family. Raising awareness of an issue has become a very effective conservation tool, as it’s often pressure from the public put on governments through campaigning, where we have seen some of the most positive results. An example includes the ‘dolphin-friendly’ tuna campaign started in the United States in 1986. The International Marine Mammal Project sponsored by the Earth Institute, organised a consumer boycott in response to ever increasing dolphin by-catch from industrial purse seine fishing. A few years later, images and video footage started to appear of dolphins caught in nets and the call for the boycott expanded to other parts of the world. Eventually, in 1992, the world’s three biggest Tuna companies (StarKist, Bumblebee and Chicken of the Sea), pledged to employ specific dolphin-friendly fishing methods.
Written by Charlotte Goodayle
“Knowledge of the marine environment and its mysterious organisms, fills me with not only great curiosity, but also invaluable fulfilment”