The Lifecycle of the Orca - Essay Example

Lecturer The Lifecycle of the Orca Of the major attractions to marine zoological parks are killer whales which are also referred toas the orcas. Even though these animals are referred to as whales, they are not actually whales but large dolphins (King 4). The reason as to why these animals are referred to as the killer whales is because of their tendency to kill whales for food (King 4). At the beginning, the animals were referred to as killers of whale but later the name was changed to killer whales (King 4). We chose orcas because we wanted to learn more about their lifecycle considering that the animals are among the most highly socialized animals in the world. In addition, we wanted to find out how human activities threaten the life of the orcas particularly in the wild. This paper will discuss the biological lifecycle of orcas, how orcas interact with the environment and each other throughout their lifecycle, and how human beings affect the lifecycle of orcas. General Characteristics Orcas belong to the Kingdom Animalia, Class mammalian, order Cetacea, suborder Odoceti, Family Delphinidae, Genus Orcinus and Species orca (Northwest Regional Office [NRO]). They are well adapted to live in various environments and so they inhabit all oceans though they have a preference for cooler regions and coastal regions. They are highly social where they live in form of family groups that are known as pods with each pod consisting of 3 to 25 orcas (NRO). In addition, orcas hunt in groups and in a coordinated manner that is considered similar to the wolves. The family groups usually trace their origin to the mother’s side which means that they are matrilineal. Orcas are distinctively colored with patches of black and white which is an adaptation feature that makes it a deadly predator as the coloring makes it hard for preys to consider it dangerous (NRO). When it comes to size and weight, orcas can be as long as 10 meters and can weigh as heavy as 8164 kilograms (NRO). The senses of orcas are well developed with each pod having its distinct sound which is passed from generation to generation and it is believed to be a manifestation of culture (Ivkovich et al. n.pag.). Their diet is usually very varied and it consists of squids, penguins, sea lions, dolphins, whales, and tortoises (NRO). Literature Review Biological Lifecycle Reproduction and Mating Most of the information that is known about the reproduction of orcas has been gathered from studies carried out in zoological parks where the animals are kept in captivity. Sea World has the largest collection of orcas. From the observations carried out there, it has been found out that the female orcas reach sexual maturity at the age of 6 to 10 years while the male orcas reach sexual maturity at the age of 10 to 13 years (Sea World). Female orcas are usually on heat several times in a year which means that they are polyestrous and they ovulate even in the absence of a male counterpart a characteristic that is very rare in mammals (Boran, Heimlich and Boran 28). Another thing is that the female orcas do not experience menstrual blood loss (Sea World). Both the male and female orcas are promiscuous where they mate with more than one partner (Sea World). It is important to note that the age at which mating starts varies depending on the situation where in captivity orcas start mating early but in the wild mating takes time to occur and this has been associated with a rigid social structure where the males have to wait until they are socially mature before they can start mating (Boran, Heimlich and Boran 28). It is believed that mating does not occur between members of the same pod as a way of avoiding incest (Boran, Heimlich and Boran 31). Birth and Care of the Young Ones Gestation takes approximately 15 to 18 months after which a single calf is born. Most of the time the calves are born tail first but in some rare occasions calves have been born head first. Female orcas can bear approximately five calves within a period of 25 years (Boran, Heimlich and Boran 28). The interval between births can range between 2 years and 12 years (Boran, Heimlich and Boran 28). The interval between one pregnancy and the other is influenced partly by the young ones since they suckle for up to 2 years (Boran, Heimlich and Boran 28). Calving occurs all year round in captivity but in the wild there are peak birth months with many females calving between October and March in the northeast Pacific Ocean (Sea World). Newly born orcas weigh between 120 and 160kgs (Sea World). According to the observations carried out at the sea world, the calves suckle for approximately one year after which they are weaned but they can suckle for as long as 2 years (Sea World). Within days of birth, calves begin to swim on their own but their mothers stay by their side to help them swim properly (Sea World). Another thing is that young orcas that are yet to learn how to swim properly can be carried by their mothers using what is known as a stream swim and this is a form of wave that forms as the mother swims (Sea World). The young ones are taken care of by all the members of a pod and these include the uncles, aunts, sisters, brothers, cousins and grandmothers (Sea World). Life The young ones grow within a pod which is a form of an extended family. Inside the pod the orcas participate in hunting and for most of the time they live in the pods they were born into throughout their lifetime (Sea World). Orcas communicate using calls which are learnt from the mothers (Sea World). Research has shown that each pod has its own distinctive call pattern and this helps in the identification of pod members as well as in communication (Ivkovich et al. n.pag.). However, individual pods do not live in isolation; occasionally they interact with other pods and the result is some similarity in call patterns (Ivkovich et al. n.pag.). Most of the interactions occur for mating purposes. The members of a pod hunt as a team and this enables them to hunt animals of all sizes including the blue whale which is the largest animal on earth (Sea World). The social bonds between members of a pod are usually very strong which makes orcas highly social animals. As stated above, the orcas do not leave the pods they were born into and this means that the members of a pod are closely related thereby strong bonds. As the calves grow up they are taught social discipline by their mothers as well as other important adult members of the pod using disciplinary methods such as tooth scratching and restraining (Sea World). While not hunting, orcas exhibit interesting behaviors such as breaching and this is where orcas jump out of water powerfully and then back into the water, spyhopping where they assume a vertical position with their head outside water, and lob-tailing where the orcas slap their tail on water surface (Sea World). Some of these behaviors are what attracts people to watch them in amusement parks. Longevity Just like in human beings, females live longer than males. Studies show that females can live for as long as 80 years while the male orcas live for only 50 to 60 years (Boran, Heimlich and Boran 27). Some of the reasons that are thought to contribute to this disparity include the large size of their bodies which means that they require more food and energy to maintain them and the stressful role of being protectors (Boran, Heimlich and Boran 28). Studies carried out in the Northwest region of the Pacific Ocean estimates the life expectancies of orcas to be 30 years for males and 50 years for females (Sea World). The calf mortality is very high in some regions and a good example is the Northwest part of the Pacific Ocean where approximately 43 percent of the calves do not live beyond six months (Sea World). The causes of the high mortality rates among calves are yet to be established (Sea World). How Human Beings Affect the Lifecycle of Orcas Human beings affect the lifecycle of orcas by influencing the availability of prey. For orcas to stay healthy, the level of prey has to be adequate. Human activities lead to a reduction in the prey levels which means that the orcas spend a lot of time looking for food with the result being higher rates of mortality as well as a reduction in the rates of reproduction (NRO). For example in the region between California and British Columbia there have been widespread reductions in the number of salmons due to human activities such as overharvesting and changes in the use of land (NRO). Salmon is a major prey for orcas in this region and thus their reduction means prey shortages for orcas (NRO). Environmental contamination is also another way in which human beings affect the lifecycle of orcas. The chemicals from industries, households and agriculture often find their way into water bodies through many avenues after which they accumulate and become toxic to marine life, orcas included. The effects of chemicals on marine mammals include the impairment of reproduction, the suppression of immunity and physiological changes such as osmotic imbalance (NRO). In a study carried out in 2009, it was found out that persistent contamination of marine water with organic pollutants resulted in age-related health risks. The study was carried out on biopsy samples of Southern Resident orcas which are orcas that live in British Columbia, Puget Sound and between Canada and U.S. all year round (Krahn et al. n.pag.). After analysis it was found out that the orcas had high levels of organic pollutants such as DDT with the results showing high levels of chemicals in young orcas than in adults (Krahn et al. n.pag.). This discrepancy was associated with the passing of chemicals from mother to their young ones and it was believed to negatively affect the development of their biological systems (Krahn et al. n.pag.). Chemical contaminants are also harmful in that they affect the population of prey during the life stages that are highly sensitive (NRO). When this happens, the prey populations are decreased and thus a negative effect on orcas. Human activities expose orcas to damaging sounds. Over the years, human activities such as whale watching, recreational boating, commercial shipping, commercial fishing, and ferry operations have increased with the result being the exposure of orcas to unnatural sounds (Jelinski, Kruger and Duffus n.pag.). Orcas depend on sound to communicate and to find food. Some of the vessels such as motor boats produce a lot of noise that hinders communication between orcas and consequently they are unable to find food as well as to navigate well (Jelinski, Kruger and Duffus n.pag.). Noise from the vessels may also disturb the social structures and this is because it hinders communication that is used for the purposes of mating, social cohesion, and warning (Jelinski, Kruger and Duffus n.pag.). In a research carried out in 2002, Jelinski, Kruger and Duffus (n.pag.) found out that the vessels affect orcas and this is because they force them to change direction as an evasion mechanism. This negatively affects them as it disrupts their normal behavior. Discussion Orcas are under serious threats if appropriate measures are not put into place. This is because different human activities such as agriculture, fishing, and ferrying operations affect orcas negatively. This happens due to the interruption of the orcas’ day to day activities as well as the interruption of the normal functioning of their bodies with the result being a disruption in their lifecycle. The government has put into place measures to prevent human activities from interfering with the natural lives of orcas and these are contained in the killer whales recovery plan. The National Oceanic and Atmospheric Administration (NOAA) fisheries added orcas to the list of endangered species in 2003 and so a recovery plan was prepared as it is required by the Endangered Species Act (NRO). Some of the issues that are addressed by the recovery plan include how to handle strandings, how to protect orcas from oil spills and other environmental contaminants, how to protect orcas from the destructive effects of sea vessels and strategies to help increase the availability of prey (NRO). Generally, the government has put in place most of the necessary measures that would help to protect orcas. However, more still needs to be done particularly in educating the public on the importance of protecting orcas. Conclusion Orcas have very interesting characteristics. They are highly socialized where they live in family groups known as pods that consist of orcas that are closely related and which trace their origin to the maternal side. Another thing is that each pod has its own distinct call sound and mating does not occur within the pods. Orcas hunt cooperatively and this makes them deadly predators as they can attack any animal in the waters. Human activities are threatening the existence of orcas and this is through chemical and noise pollution and decreased availability of prey. The government is dedicated to the conservation of orcas and this is through the killer whale recovery plan. However, good results can only be achieved if individuals take precautions at an individual level. Works Cited Boran, S., Heimlich, S. and Boran, J. (2001). Killer Whales. USA: Voyageur. Ivkovich, T., Filatova, O.A., Burdin, A.M., Sato, H. & Hoyt, E. (2010). The social organization of resident-type killer whales (Orcinus orca) in Avacha Gulf, Northwest Pacific, as revealed through association patterns and acoustic similarity. Mammalian Biology, 75(3), 198-210. Accessed through Science Direct. Jelinski, D.E., Krueger, C.C. & Duffus, D.A. (2002). Geostatistical analyses of interactions between killer whales (Orcinus orca) and recreational whale-watching boats. Applied Geography, 22(4), 393-411. Accessed through Science Direct. King, Z. (2011). Orcas. New York: The Rosen Publishing Group. Krahn et al. (2009). Effects of age, sex and reproductive status on persistent organic pollutant concentrations in “southern Resident” killer whales. Marine Pollution, 58(10), 1522-1529. Accessed through Science Direct. Northwest Regional Office. Killer Whales (Orca). URL: http://www.nwr.noaa.gov/Marine- Mammals/Whales-Dolphins-Porpoise/Killer-Whales/ Sea World, 2011. Killer Whales. URL: http://www.seaworld.org/animal-info/info-books/killer-whale/index.htm Read More