Cetaceans - An Introduction

Whales, dolphins and porpoises are collectively known as cetaceans. There are approximately 79 species currently recognised and it is very likely that new species will be discovered in the future.

The variety in shape and size is wide, ranging from tiny dolphins just over 1m in length to the Blue whale (Balaenoptera musculus), which is typically 25m long and is one of the largest animals ever to have lived on earth.

What is even more interesting is that their variety does not stop there. In fact variations in their behaviour, social life, feeding habits, distribution and abundance, life histories, habitats have been observed.

The cetacean diet is an excellent example. Diet often depends on their size, whether or not they have teeth, and various other factors. Most of the larger whales feed on huge shoal of fish or tiny shrimp-like creatures such as krill, while dolphins and porpoises tend to catch individual fish or squid. Other less common, prey items include octopuses, molluscs, polychaete worms, crabs, turtles and marine mammals, including other cetaceans.

An other important feature of cetaceans apart from their variety, is their affinity to man!

First of all they are not fish but a totally distinct group of animals which have evolved from terrestrial mammals with four legs. The first real whale-like animal is thought to have appeared around 50 million years ago. Cetaceans have lost most of the external traces of their terrestrial ancestry and are all supremely adapted to underwater life.

As all mammals, including humans, they are warm blooded, breathe air, and give birth to live young. Also cetaceans usually give birth to just one young at a time. The little new-born is immediately assisted by the mother or an 'assistant' in order to swim toward the surface for its first breath. Indeed the mother will supervise and teach the young for many years. Apart from these basic biological characteristics, cetaceans show other features which reflect this affinity with man.

1. They have a large brain to body ratio (0.25 to 1.5 % in dolphins depending on the species which compares well with the 1.9 % in humans and is significantly higher than other mammals), which is reflected in their complex social and communicative abilities. Furthermore, the neo-cortex of the brain, the part with which we create, innovate and reason covers 98 per cent of the dolphin's cortex higher even than man. However it is also much thinner. Also brain features show great variation between cetacean species (Evans, 1987). (Jerison, 1983, 1978 and 1980) considers that the encephalisation quotient, EQ (the ratio of the brain volume to body surface area) is a better measure for comparing the development of mental processes between species. These show an increase both evolutionarily (from approximately 1 for Eocene cetacean skulls to 2 for Miocene toothed whale fossils) and between living taxa from 1.5 in a river dolphin to 5.6 in the bottle-nosed dolphin. The EQ of humans is approximately 7.4 that of chimpanzees is about 2.5 but almost all other mammals are substantially lower than 2.

Cetaceans rapidly learn tasks. They are playful and appear to have a sense of humour. However, even more importantly, they show to be able to learn through experience. For example: In tuna fishing areas of the Eastern Tropical Pacific (ETP), dolphins with little experience of fishing operations tend to panic when they are trapped inside the nets. But in heavily fished areas, where they are more used to this activity, they frequently wait patiently in the knowledge that they will eventually be released (Beddington et al 1985).

2. Cetaceans normally show extraordinary interest in and at times even friendliness towards humans whether swimming in the sea or on boats, as is well experienced by many local fishermen, which are often kept company by dolphins. Unfortunately, their company may not always be appreciated but I hope that through a greater awareness any negative local attitude will change to a positive one. In fact there are many true life stories of dolphins saving humans in danger: either directly by helping a drowning person close to shore or indirectly by attacking approaching dangers such as sharks. An example of each of these situations follows: 1) John Koorey, a long-distance swimmer, describes how a school of dolphins escorted him across New Zealand's Cook Strait. At one point, they suddenly disappeared, only to reappear few moments later as if nothing had happened. According to observers on Koorey's safety boat, the dolphins had driven away a potentially dangerous group of sharks that were swimming around nearby. 2) One night in November 1988, two sailors were shipwrecked in rough seas off the coast of Indonesia. As soon as their ship had sunk, a group of dolphins appeared. The animals nudged and guided the two men throughout the night, until they finally reached the safety of dry land by morning. 3) Little Bahama Bank, north of Grand Bahama Island, in the North Atlantic, is soon becoming a touristic area since it is visited on a daily bases by a population of Atlantic spotted dolphins. Denise Herzing, who has studied these dolphins for many years, describes a remarkable occasion when a human mother entered the water with her baby. One particular dolphin watched the youngster very closely and then swam off. Minutes later it returned with a calf of its own (Carwardine 1996)!

3. Dolphins' behaviours toward man has more than one advantage. Two quick examples of this are the following: 1) Near the town of Laguna, in southern Brazil, wild bottlenose dolphins cooperate with thirty or forty local fishermen in a way that pays off for both parties. The fisherman stand in the shallow, murky water, poised with their circular throw nets, while a couple of dolphins station themselves a few metres away. As soon as one of the dolphins make an abrupt, stereotyped surface roll, the fishermen cast their nets. while they are hauling them in, the dolphins snatch any fish that try to escape in all the confusion. This remarkable fishing system- initiated and controlled by dolphins rather than humans - has operated almost daily for over 100 years. There are similar human-dolphin fishing co-operatives in Mauritania, West Africa (with Atlantic hump-backed dolphins), south-east Queensland, Australia (with bottlenose dolphins); Burma (with Irrawaddy dolphins); and several other parts of the world. 2) Dolphins have also been found to be able to trigger the healing process in people. There are now so many accounts of dolphins alleviating cases of chronic depression or anxiety, enhancing recovery from life-threatening illnesses such as cancer, and even speeding up the learning potential of handicapped children, that biologists and doctors around the world are beginning to take it seriously. For example: On American study involved two groups of autistic children who were believed to be 'beyond hope'. One group was allowed to play with plastic dolphins on a beach, while the other was taken into the water to swim with some real dolphins. The beach children showed no improvement in their condition, but the water children improved dramatically soon afterwards. Other studies have demonstrated that dolphins can help handicapped children to learn four times more quickly than is possible with other teaching methods and to retain the information for a longer period of time. No-one know exactly how or why, but 'dolphin-therapy' is found to be effective and thus a whole new line of research is developing in order to understand the mechanisms of this healing process (Carwardine 1996).

4. Cetaceans have been found to associate with other marine organisms. In particular they have been found to associate with other species of cetaceans, fish and seabirds. While more research work will elucidate how these associations are formed it is interesting to note that such associations seem to be beneficial to either species or both. In the Eastern Tropical Pacific (ETP) schools of spotted dolphins (Stenella attenuata) and yellowfin tuna (Thunnus albacares) feed on fishes, squid and crabs. The tuna apparently follow the spotted dolphins possibly benefiting from the echolocation abilities of the dolphins (Perrin et al. 1973). Both seabirds and fishermen take advantage of this associate, the latter setting a net around the school, knowing that it will at the same time capture the tuna swimming close behind (Evans 1987). Here one may point out that dolphins reproduce slowly and thus recovery of population declines are slow with possible deleterious effects for both the dolphin, tuna and other associated species populations.

Thus from what I have said so far it is obvious that Cetaceans are not only a varied group of animals, cetaceans are also unique in their adaptations, biology and behaviours and thus may furnish mankind with answers to many questions relating to the effective utilisation of the marine environment and resources by another group of mammals - HUMANS. We may also find that Cetaceans may be useful to man in many more ways than those noted to date.

Cetaceans - A group of animals in danger

Unfortunately Cetaceans suffer from several direct and indirect human influences on the marine environment (IUCN Red data book 1991). The most common include:

1. Whaling and other forms of hunting,

2. Incidental capture in fishing nets:
· Tuna fishing (purse-seine netting) - In the worst period in the ETP, during 1960s and early 1970s, it has been estimated that between 200,000 and 500,000 dolphins were being killed every year, until the dolphin populations declined drastically. The invention of a special panel of fine mesh, called the Medina panel allowed the escape of the trapped dolphins. However this is not always effective (Beddington et al 1985).
· Drift-netting
· Coastal Gill-netting and Trawling

3. Competition with fisheries for food:
Over-exploitation of fish stocks may reduce food resources for cetaceans and other marine organisms producing imbalances which would take many years to restore, while in some acute exploitation fish stocks may not recover and become locally or economically extinct.

4. Human disturbance:
· Boat traffic,
· Noise
· Oil and Gas explorations
· Dolphin or whale watching can also cause disturbance if undertaken without adequate and scientific management.

5. Capture for captive confinement,
Wild dolphins have been captured and kept in captivity for more than a century. As conditions for cetacean survival in the wild are still being comprehended it is not surprising to find that many of the cetaceans in captivity are not long lived. It is only when our understanding of the biology of these animals is clear that we will be able to: 1) manage such species in appropriate semi-free conditions, and 2) realise how damaging wrong captive confinement has been and can still be to cetaceans.

6. Habitat destruction and marine pollution (Oil, Chemical wastes, Sewage, Rubbish) have all taken their toll:
Reviews of contaminant levels in cetaceans in the Atlantic and Mediterranean coasts of France By Alzieu and Duguy (1979, 1981) and western Mediterranean by Viale (1978) indicate levels to be highest for DDT, PCBs and mercury and in those cetacean species that feed primarily on fish or squid and occupy coastal habitats for most or all of the year.

Due to all of the above, some cetacean species are now in serious trouble and others have all but disappeared from many of their former haunts. Not surprisingly, the IUCN Red List of Threatened Animals compiled by the World Conservation Monitoring Centre in Cambridge, UK, has listed all the species of dolphins and whales.

Each of the problems listed would deserve a talk of its own. However being aware of these problems may help us understand why research and monitoring of marine resources and in our case Cetacean populations becomes vital in checking the extent of effect of one or more of these problems on the perpetuation of the species.

Cetacean - Research studies and developments of new research techniques:

Cetaceans are relatively difficult animals to study in the wild. Many species live in remote areas far out at sea. Some species are fairly shy and elusive and will avoid boats altogether. Several larger species divide their time between separate feeding and breeding areas, which are often hundreds or thousands of kilometres apart. Not surprisingly, for many years the only information we had about them came from dead animals that had been washed ashore or killed by whalers or fishermen. Nowadays, however, a number of research techniques are being employed to study the animals in their natural habitats and exciting new discoveries are being made all the time (Simmonds & Hutchinson 1996).

Some of these contemporary research techniques involve:
1. Field observations and Photography is particularly used when following a cetacean group closely. Ways of individually identifying cetaceans, through photo identification, has greatly aided in: following their movements and mapping out their home ranges; in studying associations between different individuals; in identifying the sequence and timing of key events and behaviours in their lives, such as mating, giving birth, and recording deaths.
2. Radio and Satellite Telemetry or Remote sensing for studies of overall distribution and movements, but also to receive signals that give details of the animal's physiology and behaviour such as heart beat or swimming behaviour. At the same time measurements of the environment such as water temperature and pressure may also be recorded. All this may be achieved by appropriately attaching a transmitter on an individual cetacean.
3. Genetic studies of samples obtained from cetacean tissue in the wild or from dead cetaceans washed ashore are also important. These genetic techniques allow for detailed identifications of species and individuals, species/population diversity studies and for studies dealing with the social structure and dynamics of the populations.

In each of these techniques the unit focused on is usually the population which needs to be monitored and studied closely in order to understand its viability and persistence in the future. Thus a population's range, demographic dynamics and genetics are increasingly becoming important in assessing the condition of the cetacean population concerned and in planning ways of adequately managing conservation measures.

However apart from studying cetaceans in isolation, cetaceans may be studied in conjunction with fish stock assessments so as to obtain a fuller picture of cetacean populations in relation to their marine environment and more importantly in relation to fishing activities.

It is very important to note that Cetacean studies have been aided by a greater awareness of the general public including individuals making use of the marine resources. With out their collaboration our knowledge today would be scarcer.

Cetaceans - in the Mediterranean Sea: Scientific Research, Educational awareness and Conservation management of local populations.

From the 79 species known to date, 19 have been observed in the Mediterranean and about 8 of these species are seen regularly, these include (Carwardine 1995; Notarbartolo di Sciara pers. comm.):

Another four species are considered occasional visitors:

Among the other seven regarded as rarely occurring in the Mediterranean, the most common is the:

Unfortunately, local research on Cetaceans has been limited to dead strandings reports and occasional recordings of sightings around the Maltese Islands, mostly carried out by fishermen. Here I would like to take the opportunity to thank those fishermen who have furnished such sighting information in the past and look forward to a greater collaboration in the future. Due to the limited data available, scientific surveys and research are required to better appreciate the status of the cetacean populations in this region of the Mediterranean. Here there is a role to play by local people of every type: fishermen, yachtsmen, ferry personnel, helicopter surveying personnel, sports divers, etc. can greatly contribute toward the first stage of surveying which includes the spotting of specific sites visited by specific cetaceans at specific times of the year. Also information of the general characteristics and numbers of these cetaceans sighted may also be picked up. This type of information gathering would greatly aid research efforts undertaken by myself on local cetaceans. Toward this local research may I advice anyone at sea to forward the following basic information on each dolphin or whale sighting witnessed to the address given below:

Sighting Information :

Location of sighting; size and approximate colour of individual/s; number of individuals; time and date of sighting, distance from boat and type of boat.

Address where such sighting information should be directed:

Dr. A. Vella, Department of Biology, University of Malta, Msida, MSD 04, Malta.
FAX: (+356) 23403049

Dr. A. Vella is assisted by BICREF volunteers:
Address: The Biological Conservation Research Foundation (BICREF), PO BOX 30, Hamrun, MALTA.

Why bother with cetacean research and why is it important around the Maltese Islands?

1st: From the little that is known world wide of these animals they prove to be not only interesting from a biological point of view but also interesting to humans for their beauty and friendliness. This is apparent by the number of people (including Maltese people) who find these animals irresistible.

2nd: Due to their highly adapted marine life they respond to changes in it and thus may act as indicator species, aiding environmental monitoring and management.

3rd: As some species are closely linked to fish stocks of economic importance it is vital to understand the underlying linking relationship so as to better control fish stocks.

4th: Unless detailed research is undertaken, it will become very difficult to appropriately protect and sustain cetacean populations around our islands for future generations.

5th: Knowledge is the indispensable foundation on which education and public awareness is to be based. Scientific research is the only reliable means of obtaining such knowledge.

6th: Marine life sustainability requires long-lasting marine processes and dynamics to be respected. Biodiversity, abundance, distribution of marine organisms have taken time to evolve into a neatly intricate functional unit. Cetaceans make part of this unit. Loss in cetacean populations may only aid in creating further imbalances in an increasingly fragile Mediterranean sea.

7th: Cetaceans are fast becoming of touristic and of therapeutic value as more and more people seek their presence for pleasure or for treatment of various psychological problems. However effective utilisation of cetacean populations for such activities need to be preceded and go hand in hand with constant and extensive studies of the populations concerned. This is mandatory in order to minimise disturbance to the cetacean populations concerned.

8th Last but not least, as humans are the major exploiters of marine resources it is their responsibilities to find ways of effectively managing the marine environment. Just as a farmer takes care of his land if he wants it to produce its crop in subsequent years, so the marine environment has to be taken care of for future generations of users.

Cetacean research - Place for collaborations at National and International levels:

I would like to conclude my presentation by pointing out that the research and management of cetaceans has to be carried out at both local and international level because of the large distributions involved in most cases. This workshop aims at setting up a working framework for local research, monitoring, education, and conservation management. This local framework can then grow to include international working links.

The workshop session in the afternoon gives those present the opportunity to contribute toward increasing our knowledge of local population sightings. Just in the last few months it has been possible to get a good number of valuable sighting information from local fishermen and yachtsmen which clearly stand as testimony that several Cetacean species including whale species do indeed visit the waters around the Maltese Islands and that many local people enjoy collaborating in this way. Thus with a little effort from all those that use the marine resources lots of other valuable information could be gathered aiding environmental and economic national interests.

Conclusion

The most effective conservation strategies for cetaceans will evolve from a combination of well directed scientific research, coupled with an understanding of the political, social, economic and cultural shaping of the problem/s. These studies will required a sound basis of fundamental research on the biology of cetaceans and the influence which environmental and other factors have on their populations.

References:

Alzieu, C. and Duguy, R. (1979) 'Teneurs en composes orgaochlores chez les cetaces et pinnipeds frequentant les cotes francaises', Oceanol. Acta, 2 (1), 107-20.

Alzieu, C. and Duguy , R. (1981) 'Nouvelles donnees sur la contamination des cetaces par les organochlores', Cons.Int.l'Explor.Med., Doc. C.M. 1981/N:8

Beddington, J.R., Beverton, R.J. H. and Lavigne, D.M. (Eds.) (1985) Marine Mammals and Fisheries. George Allen & Unwin, London, UK.

Carwardine, M. (1996) The Book of Dolphins. Dragon's World Lts. Surrey, UK.

Carwardine, M (1995) Whales, Dolphins and Porpoises: The visual guide to all the World's Cetaceans. Dorling Kindersley, London, UK.

Evans, P.G.H. (1987) The Natural History of Whales and Dolphins. Academic Press - Harcourt Brace and Company, Pub. London, UK.

IUCN Red Data Book (1991) compiled by Klinowska M. Dolphins,./vb c, Porpoises and Whales of the World. IUCN Gland, Switzerland and Cambridge, UK.

Jerison, H.J. (1973) Evolution of the Brain and Intelligence, Academic Press, New York, NY.

Jerison, H.J. (1978) 'Brain and intelligence in whales' in Frost, S (ed.) Whale and whaling. Vol.II Australian Govt. Printing Service, Canberra, pp 161-97.

Jerisen, H.J. (1980) 'The nature of intelligence', paper presented at the IWC Conference on Cetacean Behaviour, Intlligence and the Ethics of killing Cetaceans, Washington, D.C. 28 Apr-1 May 1980.

Perrin W.F., Warner, R.R., Fiscus, C.H. and Holts, D.B. (1973) Stomach contents of porpoise, Stenella spp and yellowfin tuna, Thunnus albacares, in mixed species aggregations. Fish. Bull. 71, 1077-92.

Simmonds, M.P. and Hutchinson, J.D. (Eds.) (1996) The Conservation of Whales and Dolphins: Science and Practice. John Wiley and Sons, Sussex, UK.

Viale, D. (1978) Evidence of metal pollution in Cetacea of the western Mediterranean', Ann. Inst. oceanogr., Paris, 54, 5-16.