The Extreme Breeding and Sexual Reproduction Behaviour of the Mirounga Leonine - Research Paper Example

Abstract The study undertaken is focused on the extreme polygyny of southern elephant seals of the Sea Lion Island, Falkland Islands. The results of the study undertaken by Fabiani, Galimberti, Sanvito and Hoelzel presented an update of the line of research that it is even to the point of being an extreme type of polygyny. In addition, the variation of the polygyny behaviour of the northern population from the southern population had been determined through a synergy of different methods including behavioural measures and genetic markers. The research is a continuation of the investigation and further information gathering in relation to the extreme breeding and sexual reproduction behaviour of the Mirounga leonine, or the southern elephant seal in the latest population located specifically in the Falkland Islands. Background of the Study There are different concepts that are included in the study undertaken. One is the case of polygyny and the different issues that are related specifically based on one of the species of mammals that can be known as an important case of polygyny through the course of behavioural science which is the elephant seal. Polygyny Defined Polygyny is one of the types of breeding in animals which can be described by having a male member of the population have specific or non-specific number of female partners. The said process can be considered of interest specifically in behavioural ecology in relation to the determination of different concept such as genetic contribution of parents, paternity, breeding behaviours and techniques and other issues that can help classify, observe and analyze the animals belonging to different groups and families (Scheffer, 1969; Sumich & Sumich, 2008). Included in the most significant examples of animals that utilize polygyny are the mammals. Based on the studies that had been undertaken related to the polygyny in mammals, one of the most important reasons for the said practice and/or adaptation is the unequal production of the gametes from the female compared to the male members of the population. The main role of the males in the population is to mate with a number of females regardless of the percentage the said number of females can achieve pregnancy in a particular breeding season. Due to the said behaviour of the male population, the females can also have different partners but fertilization and pregnancy can be achieved by a single male member of the population (Sumich & Sumich, 2008). There are different factors that can be related to the polygyny in mammals. Aside from the disparity in the gametes, sexual dimorphism is also another important indication of polygyny in selected species. The type of mammal under study belongs to the group significantly known to practice polygyny (Sumich & Sumich, 2008). The Elephant Seal and Polygyny In the Order Pinnepedia, the Phocidae within which the focus of the study the elephant seals belong, can be considered highly developed in terms of polygyny. The said characteristic includes the majority of the Phocidae group. Based on earlier studies undertaken, the origin and reasons for the polygyny can be speculated on the basis of different reasons such as the variation in the site and location for breeding and the differences in size and physiology of the male and female members of the population, already discussed as the sexual dimorphism (Sumich & Sumich, 2008). The elephant seals can be classified on the basis of the origin of the population. The main focus of the study is the group originating from the south, the southern elephant seals. There are different species that make up the said group (Table 1). Species of the Southern Elephant Seals Species Area of Origin Mirounga leonina Falkland area Mirounga leonina Macquarie Islands Mirounga leonina Heard Island Mirounga leonina Different areas of the south Mirounga angustirostris Northern elephant seal species (Source: Scheffer, 1969) The species Mirounga leonina can then be considered as the elephant seals from the southern are and the Mirounga angustirostris is the northern elephant seals. In general, the Mirounga species physiologically display sexual dimorphism with the females relatively smaller and lacking the elongated nose, the elongated canines and the thickened neck which are distinct characteristics of the adult males (Sumich & Sumich, 2008). Research Results of Studies on Southern Elephant Seals Prior to Fabiani et al. The study of the polygyny in the southern elephant seals is based on different aspects such as the main breeding process and the information regarding behavioural ecology, the methods and techniques of data gathering, and the qualitative and statistical analysis of the significance of the data gathered and the methods used. In the process of breeding within the southern elephant seal population, can be considered to have a high level of variation on the basis of the different factors that can affect the said process such as the reproductive success of the males. In a comparative study of the northern and the southern elephant seals in terms of paternity success, the southern population significantly showed more advantage. This can be attributed to the difference between the male and the female members of the elephant seal population in the respective areas (Hoelzel, Le Boeuf, Reiter & Campagna, 1999). In the said types of qualitative analysis, it is important to consider the factor and parameter that can be used to measure the inequality in the mating and copulation process. This can be attributed to the fact that validity and reliability of results can be questioned since results can vary based on the specific factor that can be used. In the study of the southern elephant seals the lek mating system had been predominantly used due to the comparative advantage in terms of validity of the mating study results with other systems of measuring the mating process (Galimberti, Fabiani and Sanvito, 2002). The new century initiated the in depth study of the different aspects of behavioural ecology with the development and improved techniques of molecular study. This aided the process of studying the breeding behaviours of mammals, thus, resulting to a recognized breakthrough in the accumulated knowledge in the field of behavioural ecology. Through the said field, the mammals and specifically the species most suitable for the study of behaviours in breeding and polygyny had been determined. The study on the viability of the southern elephant seal specifically the Falkland Islands population had been initiated and resulted to the important population trends. The said population became the target of future research of behaviour ecology since there is limited information gathered in relation to the said group. Exploratory studies revealed important aspects significant to the study generally the viability of the said population. This is although the small population size can risk the southern elephant seals toward extinction (Galimberti, Sanvito, Boitani & Fabiani, 2001). In a subsequent research undertaken that deals with the linearity aspects in the study of dominance hierarchy, the southern elephant seals had been used namely the populations from the Valdés Peninsula and Falkland Islands. Linearity then had been concluded to be affected by the factors affecting the completeness of matrices and other variables. For that matter, localized results or data in the specific locality can be considered reliable because higher levels can result to biased linearity (Galimberti, F., Fabiani, A. and Boitani, L. (2003). Based on the results of the studies undertaken prior to the Fabiani et al. in 2004, there are different points considered to be the foundation of the research. One is the interest in polygyny which can be considered as an important aspect of behavioural ecology due to the fact that the acquisition of such knowledge can help maintain the viability of a population specifically in cases wherein the species is in danger of extinction. Another point is the fact that the southern elephant seals have distinct characteristics and a research that focus on a relatively distinct population can be considered to achieve significant result that can contribute to the field. Through the prior research in the issue, significant and effective methods in data gathering and analysis techniques had been gauged, thus, researchers can determine the appropriate method and procedure to apply. Determination of the Extreme Polygyny by Fabiani et al. The methodology applied in the research undertaken is based on the study of the appropriate and efficient techniques that achieved reliable and viable results. The research is focused on the southern elephant seals that can be found in the Sea Lion Island, which is part of the Falkland Islands and considered as the main site for breeding of the said species. The study covered the three breeding seasons of three consecutive years, 1996 until 1998, through the months of September to November (Fabiani et al., 2004). Based on the observations, the population is localized and the population size is small which according to the prior research can give reliable results in terms of the factors and parameters that are related to the breeding process. The areas covered in the island are the coastlines with the approximate length of 4.4 km. Survey and monitoring of the study area is performed daily during low tide (Fabiani et al., 2004). The sample population included in the study is composed of 527 to 567 females and 68 to 81 males. Markers were used to monitor the members of the population that are copulating. There are different factors used to be able to analyse the behaviour of the population. One is the observation of harem or a grouping of females with the corresponding male. The behaviours of the harems are recorded on the basis of different parameters with respect to time, both in the daily and seasonal basis. In addition, the male reproductive success was also measured through the ENFI parameter defined as the estimated number of females that had been fertilized (Fabiani et al., 2004). In terms of classification and identification, the DNA had been analysed through the samples gathered and extracted from the hind flippers of the seals. The said samples are then analysed to match the pups produced in the successive seasons under study. Though there are data based on ocular study and observation, the actual DNA study can be considered to present confirmed paternity results. Specifically, the process undertaken to analyse paternity is through the microsatellite DNA loci amplified to be analysed with ease (Fabiani et al., 2004). The data gathered were organized and analysed through the different statistical parameters namely the measures of central tendencies (mean and median), standard deviation (SD) and the median absolute deviation from the median (MAD). MAD is used to be able to statistically analyse the data with less effects from the extreme values. In addition, the CV or the coefficient of variation is used to determine the variability and the significance of the gathered data (Fabiani et al., 2004). Results of the study undertaken are based on the genetic diversity, the behavioural aspects, the paternity and the mating performance. In the population of 263 with 101 males and 162 females, no significant differences had been observed from the different genders. Compared to other populations of the southern elephant seals, there is no significant variation in the alleles that had been analysed (Fabiani et al., 2004). In terms of the breeding behaviour of the elephant seals, mating had been undertaken at least one of the three seasons under study by 28.2 percent of the male population. In terms of copulation mean the value is 5.65 + 15397, with med = 0 and MAD = 0 for all males. For those males that performed copulation, the mean is 20.05 + 25.0. Polygyny can be observed since approximately half of the population (54.8%) had performed copulation that are less than 10 (Fabiani et al., 2004). Based on the paternity assignment, the methods used have high level of confidence as well as high achievement and development of pups. The results gathered had been analysed and significant observation of success in terms of the mating techniques in the said species had been observed. Some of the contributing factors in relation to the said success in the mating process are the alternative and unconventional methods that had been observed in the population of the elephant seal under study. One is the capability of the males to cover different harems which can be considered to increase the probability of pregnancy (Fabiani et al., 2004). One of the most important parameter in the study undertaken is the determination of the level of polygyny in the population. Based on the study that had been undertaken the SLI breeding colony has a high level, specifically 75% through a range of 57 to 96%. The said results is significantly higher than other populations of the southern elephant seals in areas such as Punta Delgada and the other groups of seals that are situated in the north. Another feature of the extreme polygyny exhibited by the said species is the capability to have the mate a particular harem based on research up to a maximum of 6 breeding seasons. The said result is comparatively the highest compared to other groups (Fabiani et al., 2004). The study undertaken by the research group then had achieved a number of different results and conclusions. One is in terms of the mating behaviour of the elephant seals which can be considered the same regardless of the region of origin. Important factors that can affect the dominance in terms of the mating process include the phenotypic, the behavioural and the environmental factors. The most significant analysis based on the research undertaken is the polygyny of the population that can be characterized as being extreme due to the high level of mating and breeding values and observation. Conclusion The study undertaken contributed in different aspects such as methods of data gathering, analysis and organization of data related to the southern elephant seals. In addition, the result related to the extreme polygyny in the said species had been achieved by the research process undertaken by Fabiani et al. References Clutton-Brock, T.H., Albon, S.D. and Guinness, F.E. (1981). Parental investment in male and female offspring in polygynous mammals. Nature 289: 487 – 489. Fabiani, A., Galimberti, F., Sanvito, S. and Hoelzel, A.R. (2004). Extreme polygyny among southern elephant seals on Sea Lion Island, Falkland Islands. Behavioral Ecology, 15 (6): 961-969. Fabiani, A., Hoelzel, A.R., Galimberti, F., and Muelbert, M.M.C. (2003). Long-Range Paternal Gene Flow in the Southern Elephant Seal. Science, 299 (5607): 676. Galimberti, F., Fabiani, A. and Boitani, L. (2003). Socio-spatial level in linearity analysis of dominance hierarchies: a case study on elephant seals. J Ethol 21 (2): 131-136. Galimberti, F., Fabiani, A. and Sanvito, S. (2002). Measures of breeding inequality: a case study in southern elephant seals. Can. J. Zool. 80 (7): 1240–1249. Galimberti, F., Sanvito, S., Boitani, L. and Fabiani, A. (2001). Viability of the southern elephant seal population of the Falkland Islands. Animal Conservation, 4 (1):81-88. Hoelzel, A.R., Le Boeuf, B.J., Reiter, J. and Campagna, C. (1999). Alpha male paternity in the elephant seals. Behav Ecol Sociobiol 46: 298-306. Le Boeuf, B.J. and Reiter, J. (1988). Lifetime reproductive success in northern elephant seals. In Reproductive Success, Chicago: University of Chicago Press, 344-362. Scheffer, V. (1969). Seals, Sea Lions And Walruses. Stanford University Press. Sumich, J.L. and Sumich, G.D. (2008). Laboratory and Field Investigations in Marine Life. Jones & Bartlett Publishers. Wainstein, M., Le Boeuf, B., Campagna, C., Amos, B., Gemmell, N. and Ortiz, L. (1999). Paternity in southern elephant seals (Mirounga leonina). In The 13th Biennial Conference on the Biology of Marine Mammals Abstracts. The Society for Marine Mammalogy, 195. Read More