Title page for ETD etd-01162007-134154


Document Type Master's Dissertation
Author Munyai, Fhatuwani Michael
Email mmfhatuwani@zoology.up.ac.za
URN etd-01162007-134154
Document Title Intersite movement by Southern Elephant seals ashore at Marion island
Degree MSc(Zoology)
Department Zoology and Entomology
Supervisor
Advisor Name Title
Marthan N Bester
Keywords
  • moulting haulout
  • winter haulout
  • Marion Island
  • Southern elephant seals
  • movement
  • breeding haulout
Date 2007-04-20
Availability restricted
Abstract
Data from an on-going mark resight program at Marion Island from November 1983 to April 2004 was used to investigate the patterns and frequency of intersite movements of southern elephant seals (Mirounga leonina) during haulout events. The number of times each seal moved, the number of sites visited and the distance covered were used to determine the patterns and frequency of intersite movement by males and females of different age classes during natal, winter, moult and breeding haulouts. The interactions between age class and sex, and between haulout type and sex were significant for all three measures of movement. Southern elephant seals show substantial differences in the patterns of movement between males and females. While there is an increase with age in the number of times moved, the number of sites visited and the distance moved by males, this is not the case for females. Adult males on average moved significantly more often (> 4 times) than adult females, and male elephant seals in general moved significantly more than females during both the moult and the breeding haulouts. In general, adult males visited on average significantly more sites (1.64) than adult females (1.18). This was the result of different obligations of the two sexes during the different haulouts. Subadult and adult males on average moved significantly further than their female counterparts, and males moved significantly further than females during the moult (m= 1.81 km, f= 1.59 km) and breeding (3 times more) haulout.

Age has no influence on the patterns of intersite movement by breeding females for all three measures. For breeding males, however, age has a significant influence in number of times an animal moved and the distance it moved. Older mature breeding males (9 & 10+ year-olds) moved more frequently and further than younger breeders (6 & 7-year-olds) because mature animals were often involved in dominance interactions in defence of their harems or access to cows. Breeding males differ significantly from breeding females of all comparable ages: they moved significantly more often, visited more sites and moved further than breeding females. This is because females need to be with dependent and relatively immobile pups for most of the duration of the breeding season. While moulting males and females showed no clear pattern of behaviour in all three measures of intersite movement, age did have a significant influence. Amongst males, 6 and 7-year-olds moved significantly more often and visited significantly more sites than 1 to 5-year-olds and 1 to 4-year-olds, respectively. Amongst moulting females, immature animals (1 & 2-year-olds) moved significantly more often, visited more sites and moved further than mature animals. This was possibly a result of the different obligations of these groups prior to the moult haulout where adult females were involved in the strenuous and energy taxing breeding haulout. During the moult of males and females of comparable ages, males older than 1 year moved significantly more than females of the same ages. In addition, moulting males between 1 and 8 years of age visited significantly more sites than females of the same ages and moulting males between 2 and 8 years old moved further than moulting females of similar ages. Although age has no significant influence in all three measures of movements within both wintering males and females, a significant difference is found when comparing corresponding ages of the two sexes, with males being more adventurous than females in terms of all three measures of movements. This was likely a result of earlier maturity in females, as participation level in the winter haulout at Marion Island declines before individualís haulout to breed or become pregnant

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