Biology and Ecology of Dolphins - Essay Example

BIOLOGY AND ECOLOGY OF DOLPHINS by + Introduction In the ocean, the basic social unit is referred to as a school but in the case of dolphins it is referred to as a pod. This unit is responsible for improved chances of individual survival. Dolphins in a pod use both acoustic as well as non-acoustic communication. Dolphins are like most other marine animals very social. Dolphins will often hunt together as it improves their odds of acquiring food. Unlike most animals, dolphins will often cooperate in the search for mates choosing to work in pairs (Odell, 2010). Dolphins face a multitude of threats in the wild. These threats are both natural as well as those relating to man. Of all threats to dolphins, the largest percentage of these threats is directly related to humans and their activities in the oceans. Human activity in oceans has contributed to the extinction of quite a number of dolphin species (Allison & Cross, 2006). Research suggests that human activity is responsible for up to 95% of all dolphin deaths with natural treats contributing to only 5%. The demand from people wanting to see dolphins causes a lot more dolphin captures leading to higher and higher numbers of dolphins in captivity that is in itself a threat to dolphin numbers in the wild. Conservation of dolphins like any other animal is very significant for their overall survival. It is only fitting that humans being the number one threat to dolphins be saddled with the largest responsibility for conservation. There is a maximum hope for a total change in the large number of deaths of dolphins through the various conservation efforts in place. Dolphin numbers are beginning to see an increase as a result of these efforts (Carwardine, 2002). Behavior Social According to King, J. (2001). Dolphins are highly social animals having a basic social unit called a pod. They manipulate their social environment by cooperating and forming alliances. Dolphins are dependent upon one another when defending themselves, hunting and even in mating. These pods are not constant however since dolphins will join pods leave and often rejoin in differing combinations (Taylor, & Dunstone, 1996).. Sometimes pods will join other pods to form larger pods called herds. Pods size is often determined by openness and depth as well as food availability. There have been reported case of instances in deep water with high food availability where super pods have been witnessed reaching up to 1000 dolphins and stretching over a mile in length. Shallower areas witness smaller pod formations of up to 20 dolphins. Pod composition is highly based on age, sex and reproductive status. There are various types of pods. One type of pod consists of mother dolphins and calves, such maternity pads are referred to as nurseries. They may include a number of elderly dolphins in protection within the pods. Babysitting within these pods is not uncommon and may in some instances members from a different species. Juvenile pods will often consist female and males that have left the nurseries, but are yet to achieve sexual maturity (Claybourne, 2013).It is here that they learn acceptable dolphin behavior. Upon maturity female will typically go back to their mother pods to raise their own offspring. Male that have acquired sexual maturity will form pair-bonds and go off in search of mates. These pair-bonds are often lifelong. Adult males will rarely associate with juveniles. Reproductive Most male mammals will rarely work together when it comes to mating choosing to outdo each other in order to establish dominance for mating rights. Dolphins, on the other hand, seem to gain advantage by forming a male pair-bond which they use to herd one or even more females into a mating situation (Bowermaster, 2010). These pairs work in unison while somehow remaining in competition for mating. Reproductive dominance is established by the exhibiting aggressiveness to sub-dominant dolphins. This is done by jaw-popping, tail-slapping racing and chasing. Occasionally dolphins will produce bubble cloud from their blowhole as an aggressive behavior. Older animals are considered as repositories for dolphin behavior acting as group leaders and passing this information to younger members of the pod. Feeding. Since dolphins are nearly always in a pod, it is only natural that they hunt and feed within these pods. It is common for members to leave the pod, join another pod and rejoin it later for purposes of mating or hunting. They may even join a hunting pod for a few minutes or hours till the hunt is over and then leave again (Thomas, Moss & Vater, 2004).. This cooperation ensures that each member of the pod is well fed as opposed to each individual going off on their own. Hunting in pods ensures efficiency and betters the odds of a larger catch (Brooker, 2012). Vocalization. From the birth, dolphins produce individual signature whistles. These whistles will remain unchanged throughout life. This suggests that dolphins are self-aware or are in a position to form a concept of self even in a pod situation. Research using sonograms on the short whistles has identified that each animal has its own unique whistle (Shogren, 2013). Male dolphins will develop whistle signatures closely resembling their mother’s while females are more independent of maternal influence. It is believed that is a mechanism to avoid mating between mothers and their male offspring. Whistling is largely used by mothers to communicate with their offspring as a means of locating each other. Whistles often communicate level of alertness emotional state, availability of food, presence of danger and hierarchy within the pod (Perrin, WüRsig & Thewissen, 2009). Threats to dolphins. Being such a large expanse of space the ocean is full of threats to the animals living within, and dolphins are no exceptions. In as much as, dolphins face several natural threats man is the most dominant threat to the survival of dolphins. Statistics shows alarming increase dolphin deaths as a result of fishing nets, dynamite fishing, collisions with boats, beaching due to sonar interference and marine pollution (Gunderson, 2011). Dolphin capture and holding in aquariums across the world is a major cause of alarming dolphin deaths. The capture process itself is according to research a major contributory factor to dolphin deaths. Apart from the capture process, the transportation process as well as exposure to diseases while in captivity also causes a large number of dolphin deaths (Gleick, (2012). Another human attributable threat to dolphin survival is the unstoppable chemical pollution. Heavy metal pollution and oil contamination is a growing threat to dolphin populations. This contamination mostly contributes to high infant mortality and illness among dolphins. Being at the top of their food chain dolphins suffer the highest effects since they consume the combination of contaminants (The World Conservation Union, 1991). Another great danger to dolphins in the wild is noise pollution from several human-related sources. Some of these include activities such as: navigational sonar, ship engines and oil drills that produce continuous streams of noise underwater that often frighten injure and disorient dolphins (Simmonds, 2007). This kind of noise may even cause dolphins to move away from their natural habitat. The following is a statistical chart showing bottlenose dolphin stranding. Dolphins also meet their deaths from humans through traumatic injuries sustained as a result of entanglement in shark safety nets, fishing nets and cages. Collision with boats and ships and their rotor blades is also not uncommon. The alleged exploration of their habitat in many ways brings the danger right to them (Nichols, 2001). Though it is well understood that when it comes to the food chain they are on top, dolphins are not exempt from nature. They face competition from toothed whales. The diminishing food sources as a result of global warming are also a factor contributing to the decreasing number of dolphins in the wild. It is however evident that humans pose the biggest threat to dolphins as compared to natural causes (Reeves, Leatherwood & Perrin, 1994). The chart bellow illustrates some statistics. Conservation of dolphins. The battle to save the dolphins is not lost. Gains have been made in recent past to the aid of dolphins. Some conservation efforts have been aimed at the protection and preservation of water habitats to ensure dolphins continue to have a place to live (Reeves, 2003). Although some such as the Ganges River and the Amazon River are considered as critically endangered there is still hope. Laws passed as the Marine Mammal Protection Act of 1972 and also the 1973 Act of Endangered Species has played a major role in the protection of dolphins. Though slow at first and effects minimal at first, persistence will play a major role in the fight for the dolphins (Reeves, Leatherwood & Perrin, 1994). Several private and non profit organizations have also come on board to assist in the protection of dolphins. Some of these are American Cetacean society which works for the protection of dolphins, whales and porpoises together with their habitats through education and research (nbn-resolving.de/urn:nbn:de). Cetacean Alliance is a non-profit outfit that campaigns for marine life conservation wild wide and the entire biodiversity and the reduction of human impact on the numbers of dolphins. The Sea Shepherd Conservation Society is a well recognized international organization whose main goal is to bring to an end the senseless destruction of dolphin habitats the world over (Herzing, 2011). Conservation of dolphins is not only being done in the wild but also in captivity. Greater research has helped to dock captive dolphin deaths by nearly half. Dolphins that are rescued but for health and survival reasons cannot be released are also being taken care of with some even getting prosthetic fins to aid in their movement (White, 2007). Conclusion. Dolphins are without doubt magnificent creatures that are very fascinating. From their intelligent and docile nature they inspire much fascination, and this is sometimes to their detriment. Human beings have for decades interfered with their lives and survival by interfering with the various aspects of their lives such as habitats, breeding grounds, feeding grounds and migration routes. The great losses in dolphins may take some time but with persistent conservation efforts meaningful gains will be made. References ALLISON, A., & CROSS, G. S. (2006). Millennial monsters: Japanese toys and the global imagination. Berkeley (Calif.), University of California press. CARWARDINE, M. (2002). A guide to whales, dolphins & porpoises. San Francisco, Fog City Press. CLAYBOURNE, A. (2013). Dolphins. London, Raintree. BOWERMASTER, J. (2010). Oceans the threats to our seas and what you can do to turn the tide : a participant media guide. New York, PublicAffairs. http://www.contentreserve.com/TitleInfo.asp?ID={7F912BAB-BCF0-4A2B-9628- C29808988334}&Format=50. BROOKER, W. (2012). The Blade runner experience the legacy of a science fiction classic. New York, Columbia University Press. http://public.eblib.com/choice/publicfullrecord.aspx?p=909615. PERRIN, W. F., WÜRSIG, B. G., & THEWISSEN, J. G. M. (2009). Encyclopedia of marine mammals. Amsterdam, Elsevier/Academic Press. http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&A N=265186. GUNDERSON, M. M. (2011). Spinner dolphins. Edina, Minn, ABDO Pub. GLEICK, P. H. (2012). The worlds water. the biennial report on freshwater resources Volume 7 Volume 7. Washington, DC, Island Press. http://dx.doi.org/10.1007/978-1-59726-228- 6IUCN-- THE WORLD CONSERVATION UNION. (1991). Resolutions and recommendations. Gland, Switzerland, International Union for Conservation of Nature and Natural Resources. NICHOLS, C. (2001). Observations of interactions between Hectors dolphins (Cephalorhynchus hectori), boats, and people at Akaroa Harbour, New Zealand. Wellington, N.Z., Dept. of Conservation. REEVES, R. R., LEATHERWOOD, S., & PERRIN, W. F. (1994). Dolphins, porpoises, and whales: 1994-1998 action plan for the conservation of cetaceans. Gland, Switzerland, IUCN REEVES, R. R. (2003). Dolphins, whales and porpoises: 2002 - 2010 Conservation Action Plan for the Worlds Cetaceans. Gland, Switzerlanad [u.a.], IUCN. REEVES, R. R., LEATHERWOOD, S., & PERRIN, W. F. (1994). Dolphins, porpoises, and whales: 1994-1998 action plan for the conservation of cetaceans. Gland, Switzerland, IUCN (2014). Long Island Sound Prospects for the Urban Sea. New York, NY, Springer New York. http://nbn-resolving.de/urn:nbn:de:1111-201311221521. HERZING, D. L. (2011). Dolphin diaries: my 25 years with spotted dolphins in the Bahamas. New York, St. Martins Press. WHITE, T. I. (2007). In defense of dolphins the new moral frontier. Malden, MA, Blackwell Pub. http://site.ebrary.com/id/10196725. SIMMONDS, M. P. (2007). Whales and dolphins of the world. London, New Holland. SHOGREN, J. F. (2013). Encyclopedia of energy, natural resource, and environmental economics. http://www.sciencedirect.com/science/referenceworks/9780080964522. TAYLOR, V. J., & DUNSTONE, N. (1996). The exploitation of mammal populations. London, Chapman and Hall. THOMAS, J. A., MOSS, C., & VATER, M. (2004). Echolocation in bats and dolphins. Chicago, University of Chicago Press. ODELL, S. (2010). Island of the Blue Dolphins. Boston, Sandpiper.http://www.contentreserve.com/TitleInfo.asp?ID={8CFF25EC-09AB-427F- B7CC-6975573E3FDB}&Format=410. KING, J. (2001). Wales. Footscray, Vic, Lonely Planet. Read More