Cetaceans (Whales) IUCN Status Category: Variable INTRODUCTION

Transcription

1 Cetaceans (Whales) Class: Mammalia, Order: Cetacea IUCN Status Category: Variable CITES Appendix: I and II INTRODUCTION Cetacea is an order of mammals, comprising over 80 species of whales, dolphins and porpoises. There are three Suborders: the Archaeoceti, the Mysticeti, and the Odontoceti. Cetaceans fall into two categories: mysticetes or baleen whales, and odontocetes, including toothed whales, oceanic and river dolphins, and porpoises. Of these, 13 species are commonly referred to as the great whales and include the bowhead, North Atlantic right, North Pacific right, southern right, blue, fin, sei, humpback, Bryde's, northern minke, southern minke, gray, and sperm whales. The only great whale with teeth is the sperm whale. Although predominantly marine mammals, some small cetaceans live in large river systems of Asia and South America. The Archaeoceti or "ancient whales" are extinct and known only by fossils. The Odontoceti or "toothed whales" have either no, few or numerous uniform and conical teeth, asymmetrical skull and single nasal passage. The Mysticeti or "baleen or whalebone whales" are named after their feeding apparatus; a series of transverse plates of comb-like baleen (made of similar material to that of the human fingernail) which descend from the roof of the mouth and serve to strain plankton and small fish. Other distinctive characteristics of the baleen whales include a symmetrical skull with no melon (the apparatus used by odontocetes for echolocation) and a pair of nasal cavities. Toothed whales, dolphins and porpoises are a diverse group of over 70 species. GENERAL BIOLOGY Cetaceans are mammals that spend all their lives in water, and have evolved many adaptations to this way of life. The body is streamlined, with no hind limbs, reduced forelimbs and a powerful horizontal tail for propulsion. The "nostrils" have become blow holes at the top of the head (except in the Sperm Whale, where it is at the front of the head) to facilitate respiration whilst travelling through water. The dentition of the toothed whales are also roughly related to feeding habits, with the squid eaters having few or no visible teeth, and those with a more varied diet, particularly those where schooling fish are included, having a generally longer snout and many teeth. The majority of the large cetacean species are baleen whales, including the Blue Whale (up to 30m), although there are smaller baleen whales, including the 10 meter Minke Whale and the 6 meter Pygmy Right Whale. Many baleen whales travel long distances every year, between summer feeding grounds in polar waters and winter breeding grounds in the tropics. In general, baleen whales seem to live in small social groups, although these can join to form large herds at rich feeding grounds. The range in size among toothed whales is wide, from the 18 meter (male) Sperm Whale to the smallest dolphins and porpoises at less than 2 meters. They have extremely varied habits; some travel long distances between summer feeding grounds and wintering areas every year, but others are relatively sedentary, perhaps only ranging over tens of kilometres in their lifetimes. Their social life is also highly varied; some species living in small groups or usually alone, and others in schools of several hundred (although these may be composed of a number of smaller social units). The fossil history of the cetaceans is incomplete and controversial. In general it seems that they evolved from land mammals which may have returned to the water some million years ago. The Archaeocetes flourished million years ago and the modern forms have been present for million years. Cetaceans have exploited all types of productive marine, estuarine, and major riverine habitat. They have adapted to be able to propel themselves through the water at speeds and to depths sufficient to escape predators and catch prey; exchange air without interrupting the smooth forward motion; maintain a fairly constant core body temperature in an environment that readily dissipates heat; and bear young in water. Vision in air and water varies with species. Some river dolphins which are nearly blind and can distinguish light from dark, while some dolphins appear to have excellent vision. Most species are vocal, producing calls and whistles that may have a social function, such as the "song" of the Humpback Whale, the individual "signature whistles" of Bottlenose dolphins and the "pod identity" call of the Orca. Many toothed whales are known to echolocate, using pulses of high frequency sound to explore their environment and seek and stun their prey. DISTRIBUTION Whales inhabit oceans and seas worldwide, inshore and pelagic. Some species such as minke or humpback 1

2 whales may be found in all oceans and seas, but most have a more restricted range. Some dolphins are restricted to specific rivers. Most baleen whales are migratory, feeding in colder waters that are rich in plankton, and travelling to lower latitudes to bear their young so that the calves can live in warmer water until they develop a sufficient insulating layer of blubber. Gray whales and humpbacks undertake the longest migrations of all whale species. For example, eastern North Pacific gray whales feed in the Bering Sea between Alaska and Russia and travel all the way to Baja California to have their calves, a distance of 12,000 to 20,000kms. POPULATION The methods traditionally used to assess the status of exploited whale populations were based mainly on data from catches. These included: the use of catch per unit effort (CPUE) as an index of abundance; data on pregnancy rates and age of sexual maturity as measures of productivity; age data to estimate recruitment and mortality; and the re-capture of marked animals to estimate population size and define separate stocks. Analyses by the International Whaling Commission (IWC) Scientific Committee over the past few years have shown many of these methods to be unreliable both in principle and in practice. Following the moratorium on commercial whaling in 1986, there has been an increase in efforts to survey whale populations directly. Despite the increased research on some of the directly exploited species, quantitative population estimates are still only available for a minority of species and almost all have wide margins of error. Population estimates of the great whales, where known, are given in Table 1. Table 1. Current status of the great whales Species Status Approx. Estimated Total Northern Atlantic right Eubalaena glacialis Endangered Western North Atlantic Eastern North Atlanticnear extinction North Pacific right Eubalena japonica Endangered Under 1,000 Southern right Eubalaena australis Conservation Dependent About 7,000 Bowhead Balaena mysticus Conservation Dependent and Critically Endangered in Svalbard, Endangered in Okhotsk and Davis Strait/Baffin Bay Probably under 8,500 Blue Balaenoptera musculus Endangered Probably under 5,000 Fin Balaenoptera physalus Endangered Around 50,000-90,000 Sei Balaenoptera borealis Endangered Roughly 50,000 Bryde's Balaenoptera edeni Data Deficient Roughly 40,000-80,000 Gray Eschrichtius robustus Conservation Dependent Critically Endangered in Western North Pacific Around 27,000 Humpback whale Megaptera novaeagliae Vulnerable Around 28,000 Northern Minke Balaenoptera acutorostrata Low risk-near Threatened 610,000-1,284,000 Southern minke Balaenoptera bonarensis Conservation Dependent No current estimate Sperm whale Physeter macrocephalus Vulnerable Unknown: maximum 1-2 million THREATS Seven out of the 13 great whale species are endangered. Years of overhunting drove the Atlantic population of gray whales into extinction, and so severely depleted the blue whale in the Antarctic that its original estimated 2

3 numbers of 250,000 whales have dropped to between 400 and 1,400 animals. Over the past few decades, the great whales and other cetaceans have suffered from new and ever-increasing dangers. Collisions with ships and entanglement in fishing gear threaten the North Atlantic right whale with extinction, while the critically endangered Western North Pacific gray whale is at serious risk probably exacerbated by intensive oil and gas development in its feeding grounds. Scientists estimate this population numbers between 100 to 200 animals. Concern is growing over other hazards including toxic contamination, the effects of climate change and habitat degradation, and marine and river pollution. The Cetacean Specialist Group consider seven species of great whale endangered or vulnerable (see Table 1), and 10 species of small cetacean are endangered or vulnerable, including most of the river dolphins. Three populations of great whales are near extinction: the Svalbard bowhead, Western North Pacific Gray, and the Eastern North Atlantic right. Bycatches in Fisheries: Entanglement in fishing gear or by-catch kills more cetaceans worldwide each year than any other mortality factor. Estimates of total kill and kill rates can only be approximate. Technical approaches, such as employment of warning devices in netting and modification in floats, weights and characteristics of the netting are unlikely to eliminate the bycatch problem, however the closure of certain critical areas to coastal gillnetting could help. Concern about the expansion of large scale driftnet fishing during the 1980s led the United Nations General Assembly to establish an indefinite global moratorium on the use of large-scale driftnets outside the exclusive economic zone (EEZ) or the 200 mile limit of any country after Discarded drift nets ("ghost nets") are also capable of entangling cetaceans and can remain "active" for several years. Numerous individuals and groups on the east coast of Canada and the United States have mounted effective rescue operations directed mainly at large whales that become entangled in cod traps and ground fish gillnets. Habitat Degradation and Chemical Pollution: Coastal, riverine and estuarine cetacean species are particularly affected by this factor. Coastal developments can destroy fish nurseries leading to a reduction in food supply; damming of rivers can result in the isolation and fragmentation of populations, and the prevention of seasonal migrations. For example, the Indus River Dolphin is now extinct in parts of its former range through illegal hunting, and fragmentation of the species range from the construction of dams. Pollution is also believed to be a potential threat to the survival of many marine and freshwater organisms. From the introduction of pollutants into waterways, toxic substances can enter the food chain and become concentrated in aquatic organisms, such as the cetaceans. The evidence for a link between chemical pollutants and the health of cetaceans is growing, and there is concern that large contaminant loads can increase susceptibility to disease and affect reproductive performance. Polychlorinated biphenyls (PCBs) are of particular concern. Accidents and Disturbance: Ship strikes or accidental collisions have been blamed for nearly 90 per cent of all North Atlantic right whale deaths for which the cause is known (excluding natural factors such as old age). Direct exploitation: Until recently, this was the greatest threat to the survival of the large cetaceans. The declining status of the great whales was so desperate by the early 1960s that it was among the reasons for the foundation of WWF in late The highest ever number of whales reported caught was 66,090 in the Antarctic whaling season. These were mostly fin and sperm whales, since the blue whales had by then been hunted close to extinction. Despite a number of conservation victories for the whales, including the moratorium on commercial whaling and the declaration of virtually the whole of the Southern Ocean as a whale sanctuary in 1994, whales are still hunted and this remains a potential threat. Since the International Whaling Commission (IWC) moratorium on commercial whaling came into effect in , by April 2001, 21,573 whales had been caught, mainly by the former USSR, Japan and Norway. As of 2001, Japan has killed over 5,620 minke whales for so-called scientific purposes, mainly in the Southern Ocean Whale Sanctuary. Norway, which lodged an official objection to the moratorium, has caught 287 whales for "scientific purposes", and hunted over 4,000 Northern minkes for commercial purposes from a depleted population. Norway has continued whale hunting, in spite of the repeated requests by the IWC urging them to stop, and the growing popularity of whale watching in Norway. Competition and Culls: The belief that cetaceans compete for resources has prompted the initiation of culling operations in some instances, such as Orca or Killer whales in Iceland and Greenland and various toothed whales in Japan. Some resource managers maintain that culling of cetaceans and some other marine mammals will improve fisheries yields. This argument is considered simplistic and invalid by fisheries and marine mammal scientists due to the complexity of the marine ecosystem. Global climate change: As the evidence accumulates that global climate changes is causing severe perturbations in ocean currents, whales, like other marine species, are likely to be affected. Global warming is already causing polar ice to melt. This could destabilize the ecology of the Arctic and Antarctic feeding grounds of many large whales and acutely jeopardize the bowhead, narwhal, and beluga, which live in Arctic waters yearround. Changes in ocean temperature could also shift the distribution of plankton and fish species, disrupting the feeding patterns of cetaceans that consume them. 3

4 Depletion of whales' food supply: Antarctic krill: There are worrying indications that climate change is also resulting in a drop in the population level of krill. A reduction in supplies of this small, shrimplike crustacean, a key source of food for many marine species, could now be the greatest threat facing Southern Hemisphere baleen whales. A dramatic decrease in krill could be catastrophic, especially for the endangered blue whale. There is evidence that krill is already in short supply at least in parts of the Southern Ocean, with seals, penguins and albatrosses being unable to rear as many young in the 1990s as they did before. The supply of Antarctic krill is crucial to the whole Southern Hemisphere marine food chain, including all the whales that migrate to the Antarctic to feed. It appears that the main food supply for krill consists of algae which overwinter in the sea ice and are released and begin reproducing when the ice melts, so there is very high productivity close to the ice in summer. WWF's CONSERVATION AND RESEARCH ACTIVITIES WWF is developing an ambitious conservation programme for endangered whale species and populations. WWF's long term vision for whales is for: * All populations of whales to have recovered to viable numbers and to be thriving throughout the oceans In the medium term, WWF is working for a significant reduction of threats to endangered populations of great whales as well as some smaller cetaceans. The threats that WWF will focus on include: *reducing ship collisions and decreasing entanglement in fishing gear *protecting whales and other cetaceans from chemical contaminants *reducing greenhouse emissions and wasteful consumption that contribute to climate change *bringing whale hunting under the strict control of the International Whaling Commission (IWC) WWF is reducing threats to whales through field research, training and capacity building, conservation education, and by securing improved national and international action and agreements. In addition, WWF is working to reduce the threats to endangered small whales, dolphins and porpoises. Conserving Endangered and Threatened Species: WWF is supporting long-term monitoring of the North Atlantic right whale in Canada's Bay of Fundy, where 50 to 75 per cent of the population gathers every summer to feed. This is the largest concentration or gathering of the species anywhere in the world. Research here is helping to refine strategies for reducing right whale deaths from ship strikes and fishing gear entanglements. In Canada, WWF is contributing to the preparation of a long-term conservation plan for the endangered bowhead whale populations of the eastern Arctic by experts from Nunavut communities, co-management and wildlife boards, the federal fisheries department, and international bowhead whale scientists. The goal of this partnership is to produce a long-term, ecosystem-based plan for continued recovery and conservation of these endangered whales. The plan will address the threats to the population including disturbance, pollution, seismic activities, and over-hunting, while taking into account the traditional interests of the Inuit people of Nunavut. WWF is also very active in the Babuyan Islands area of the Philippines, one of the few breeding grounds for the humpback whale, and possibly the southernmost recorded in the western North Pacific. In 1999, WWF scientists discovered a population of humpbacks in this area and practically nothing is known about them. Initial investigations suggest they may be threatened by dynamite fishing, natural gas explorations, and Taiwanese fisheries. A WWF team is studying these whales to determine the population's abundance, distribution and stock identity. They are characterizing the whale's habitat use and assessing the seasonality of their presence, as well as documenting threats and involving the local community in conservation efforts through an education and outreach programme. Promoting Whale Watching: In the Andenes and Tysfjord areas of northern Norway, where sperm whales and orcas are commonly seen, WWF is working to improve and expand whale watching operations. Whale watching in these areas has grown steadily since the first trips began in 1988 and has helped boost the tourism trade, providing substantial income to the local communities. The Andenes Whale Centre (Hvalsenter) was established with WWF support. In Tysfjord, WWF is funding a long-term study of the orcas and the researchers work with the whale watching operators. A report with information on over 70 whale watching operations all around the Arctic has been produced (available from WWF-Norway at info@wwf.no). In Iceland, WWF has been providing funding for The Whale Centre, an interactive museum devoted to whales and the history of whaling in Husavik, the country's most popular whale watching town. In the Pacific, WWF has been supporting efforts to monitor whale populations and assess the impact of whale watching in Colombia's Bahia Malaga, one of the principal breeding sites. WWF is also assessing the potential for establishing a new protected area around Bahia Malaga 4

5 and has joined other NGOs to hold a yearly festival along the Colombia coast to raise awareness about humpbacks and other migratory species in the Pacific. Helping create marine protected areas: In 1999, a 10-year effort led by WWF and other conservation groups, resulted in the creation of the Ligurian Sea Whale Sanctuary. Covering an area twice the size of Switzerland, it is the largest marine protected area in the Mediterranean and is the first Northern Hemisphere marine protected area to be established by several countries and include international waters. The treaty creating the sanctuary commits the three signatory governments France, Italy and Monaco to coordinate monitoring activities and to intensify actions to prevent land-based and marine sources of pollution affecting the sanctuary. Intensive advocacy efforts by WWF and other conservation groups helped influence a decision by the Mexican government to cancel plans for the construction of a giant salt producing facility near the San Ignacio Lagoon, the last undisturbed winter sanctuary of the gray whale. Many countries, including Argentina, Ecuador (including the Galapagos Islands), Australia, Brazil, Chile, India, New Zealand, Oman, South Africa, the European Union, USA and Ireland, have declared cetacean species occurring within their waters as protected. In addition, the IWC designated the whole of the Indian Ocean and most of the Southern Ocean as whale sanctuaries. WWF was key in the campaigns to establish the sactuaries. Lobbying the International Whaling Commission (IWC): WWF is closely involved in trying to make sure that the IWC operates as much as possible as a whale conservation body. A small team of WWF observers attends the annual meetings of the IWC, consulting with scientists, lobbying government delegates, and commenting on the results to the media and the public. International trade legislation: The Order Cetacea is listed on Appendix II of the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which regulates and monitors trade in these species and their related products. However, some species are listed separately under Appendix I, a classification that strictly regulates trade in the species or its products, and bans trade for commercial purposes. All large whale species and the Indus and Ganges River dolphins are listed on Appendix I. Investigating whale-meat trade in East Asia: Japan's legal domestic whale meat market remains an attractive potential for whaling countries. TRAFFIC's 1999 research, funded by WWF, found that prices for whale meat in Japan have risen significantly over the past 20 years, and the supply of whale meat is below 5 per cent of its premoratorium level. The retail price of whale meat ranges from US$ per kilo, at least three times as high as in Norway. All baleen whales are listed under CITES Appendix I, but Norway, which has reservations on several listings, is attempting to reopen international trade. Recommended Information Sources: The 2000 IUCN Red List of Threatened Species at: Evans P G H The Natural History of Whales and Dolphins. Christopher Helm, London, UK. 343pp. Carwardine M, Hoyt E, Ewan Fordyce R and Gill P Whales and Dolphins. Harper Collins, London UK. 288pp. Kemf E, Phillips C, and Baragona, K Wanted Alive! Whales in the Wild - A WWF Species Status Report. WWF-World Wide Fund For Nature, Gland, Switzerland. On WWF International's website: 5