No description available.

No description available.

No description available.

No description available.

In highly dynamic and unpredictable environments such as the Southern Ocean, species that have evolved behaviours that reduce the effects of intra-specific competition may have a selective advantage. This is particularly true when juveniles face disadvantages when foraging due to morphological or physiological limitation, such as in the case of many marine mammals. Southern elephant seals (Mirounga leonina) are a major consumer of biomass in the Southern Ocean with a global distribution. Recent modelling of the Macquarie Island population concluded that juvenile survival is a key parameter in influencing the rates of population change and as an important demographic component of the population. Resource limitation has been suggested as the primary reason for the change in numbers of these populations and this coupled with the importance of juvenile rates of survival influencing population change may provide some insight into explaining any reduction in juvenile survival. Until now, little has been known about these juveniles, ontogenetic and intra-specific differences in life history and foraging ecology have been suggested but not investigated. During this juvenile stage individuals undergo many morphometric and physiological changes as they develop toward maturity. Therefore, it would seem likely that studying the foraging ecology and growth and development patterns of this demographic group may show the proximate processes in affecting population dynamics. This study has followed juvenile seals as they grow and develop rapidly toward adulthood observing changes in foraging areas or strategies and associated changes in prey availability, differences in the seasonal availability of prey, changes in morphology and physiology for growth, maintenance or provisioning toward adulthood. In this thesis I present data for: 1) Anaesthesia for safe handling - I assessed the effects of variation in body condition and age at on the characteristics of anaesthesia, including induction time and dose-specific recovery rate which has increased the control over immobilisation level and duration, and reduces handling times for wild pinnipeds. 2) Foraging range and 3) Habitat use of the Southern Ocean -I tracked the at-sea movements of juvenile southern elephant seals using locations derived from recorded light levels. 4) Diet - I describe intra-specific dietary differences in prey composition and size. 5) Metabolic estimates and energy use and 6) Growth and body condition changes - I examined changes in mass and body composition of juvenile southern elephant seals during and between their annual moult and mid-year haul-outs. General discussion - These key ecological areas of an important predator has increased our understanding of the evolutionary and ecological interactions that influence the population dynamics of southern elephant seals at Macquarie Island and the structure of the Southern Ocean ecosystem.

Damage caused by possums (Trichosurus vulpecula Kerr) in New Zealand's extensive Pinus radiata plantations has caused concern among foresters. This study set out to examine the nature of tire problem and investigate the ecology of possums in radiata plantations in relation to damage and control. The work was carried out in the Kinleith Forest near Tokoroa in the central North Island. A review of existing literature and survey results showed that damage is mainly a problem of young plantations, consisting of bark-stripping on young trees and browsing of newly-planted seedlings. A simulated browsing experiment indicated that the latter damage was unlikely to result in discernible production losses. Bark-stripping was found to occur during the winter and spring. It had a patchy distribution and was only thought likely to prove serious where stocking was already low for other reasons. Analysis of stomach contents from animals poisoned in 1971 plantings and 1960 age class stands revealed that in both habitats possums relied heavily on foods other than pine, although in the older (1960) stands radiata pollen cones were an important winter and spring food. Insect larvae (Philia nigrostigma) were also eaten at this time of year, particularly in older stands. Little bark was consumed in either habitat, but it was a more common food in the younger stands, were it was eaten during the winter and spring. It is suggested that bark-stripping in young stands may be a response to relatively poor nutrition during the winter and early spring. Data on fat reserves, reproductive performance and growth support the view that the overall plane of nutrition was better among possums in the older stands. Possum populations were studied by livetrapping and radiotelemetry in two areas, one within a 1960 age class radiata stand (FRSA), the other extending across the boundary between a 1971 planting and cutover native forest (MSA). In the latter area there was a seasonal pattern of habitat use, with animals tending to use the native forest to a greater extent than the plantation during the winter. Population densities were similar in the two areas (2-3/ ha), with the MSA population having an apparent trend of increase. The two populations differed in composition, the FRSA one having an excess of females and the MSA an initial excess of males but an increasing proportion of females. It is suggested that disturbance of the MSA population, by burning in 1971 and subsequent poisoning, resulted in partial depopulation with initial recolonisation predominantly by dispersing males. Results from both study areas showed that young males have a greater tendency to disperse from their native area than do young females. Radiotelemetry revealed that possums in the MSA used more dens than those in the FRSA and good dens appeared to be few in the latter area. It is suggested that dens may be a limiting resource for some possum populations. Since females are known to control the use of dens the survival of males should be poorer where dens are limited, resulting ultimately in a biased sex ratio. Experimental depopulation of the FRSA and monitoring of its recolonisation over one year suggested that population re-establishment on cleared areas does not depend on local reproduction by survivors, but is primarily by dispersal in the initial stages, with an early influx of young males. The MSA population was also poisoned, in a standard 1080 airdrop, and the effectiveness of this operation was monitored. Current control practices are critically appraised in the light of the results obtained in this study and the value of widespread aerial poisoning operations in pine plantation habitats is questioned.

Damage caused by possums (Trichosurus vulpecula Kerr) in New Zealand's extensive Pinus radiata plantations has caused concern among foresters. This study set out to examine the nature of tire problem and investigate the ecology of possums in radiata plantations in relation to damage and control. The work was carried out in the Kinleith Forest near Tokoroa in the central North Island. A review of existing literature and survey results showed that damage is mainly a problem of young plantations, consisting of bark-stripping on young trees and browsing of newly-planted seedlings. A simulated browsing experiment indicated that the latter damage was unlikely to result in discernible production losses. Bark-stripping was found to occur during the winter and spring. It had a patchy distribution and was only thought likely to prove serious where stocking was already low for other reasons. Analysis of stomach contents from animals poisoned in 1971 plantings and 1960 age class stands revealed that in both habitats possums relied heavily on foods other than pine, although in the older (1960) stands radiata pollen cones were an important winter and spring food. Insect larvae (Philia nigrostigma) were also eaten at this time of year, particularly in older stands. Little bark was consumed in either habitat, but it was a more common food in the younger stands, were it was eaten during the winter and spring. It is suggested that bark-stripping in young stands may be a response to relatively poor nutrition during the winter and early spring. Data on fat reserves, reproductive performance and growth support the view that the overall plane of nutrition was better among possums in the older stands. Possum populations were studied by livetrapping and radiotelemetry in two areas, one within a 1960 age class radiata stand (FRSA), the other extending across the boundary between a 1971 planting and cutover native forest (MSA). In the latter area there was a seasonal pattern of habitat use, with animals tending to use the native forest to a greater extent than the plantation during the winter. Population densities were similar in the two areas (2-3/ ha), with the MSA population having an apparent trend of increase. The two populations differed in composition, the FRSA one having an excess of females and the MSA an initial excess of males but an increasing proportion of females. It is suggested that disturbance of the MSA population, by burning in 1971 and subsequent poisoning, resulted in partial depopulation with initial recolonisation predominantly by dispersing males. Results from both study areas showed that young males have a greater tendency to disperse from their native area than do young females. Radiotelemetry revealed that possums in the MSA used more dens than those in the FRSA and good dens appeared to be few in the latter area. It is suggested that dens may be a limiting resource for some possum populations. Since females are known to control the use of dens the survival of males should be poorer where dens are limited, resulting ultimately in a biased sex ratio. Experimental depopulation of the FRSA and monitoring of its recolonisation over one year suggested that population re-establishment on cleared areas does not depend on local reproduction by survivors, but is primarily by dispersal in the initial stages, with an early influx of young males. The MSA population was also poisoned, in a standard 1080 airdrop, and the effectiveness of this operation was monitored. Current control practices are critically appraised in the light of the results obtained in this study and the value of widespread aerial poisoning operations in pine plantation habitats is questioned.

Damage caused by possums (Trichosurus vulpecula Kerr) in New Zealand's extensive Pinus radiata plantations has caused concern among foresters. This study set out to examine the nature of tire problem and investigate the ecology of possums in radiata plantations in relation to damage and control. The work was carried out in the Kinleith Forest near Tokoroa in the central North Island. A review of existing literature and survey results showed that damage is mainly a problem of young plantations, consisting of bark-stripping on young trees and browsing of newly-planted seedlings. A simulated browsing experiment indicated that the latter damage was unlikely to result in discernible production losses. Bark-stripping was found to occur during the winter and spring. It had a patchy distribution and was only thought likely to prove serious where stocking was already low for other reasons. Analysis of stomach contents from animals poisoned in 1971 plantings and 1960 age class stands revealed that in both habitats possums relied heavily on foods other than pine, although in the older (1960) stands radiata pollen cones were an important winter and spring food. Insect larvae (Philia nigrostigma) were also eaten at this time of year, particularly in older stands. Little bark was consumed in either habitat, but it was a more common food in the younger stands, were it was eaten during the winter and spring. It is suggested that bark-stripping in young stands may be a response to relatively poor nutrition during the winter and early spring. Data on fat reserves, reproductive performance and growth support the view that the overall plane of nutrition was better among possums in the older stands. Possum populations were studied by livetrapping and radiotelemetry in two areas, one within a 1960 age class radiata stand (FRSA), the other extending across the boundary between a 1971 planting and cutover native forest (MSA). In the latter area there was a seasonal pattern of habitat use, with animals tending to use the native forest to a greater extent than the plantation during the winter. Population densities were similar in the two areas (2-3/ ha), with the MSA population having an apparent trend of increase. The two populations differed in composition, the FRSA one having an excess of females and the MSA an initial excess of males but an increasing proportion of females. It is suggested that disturbance of the MSA population, by burning in 1971 and subsequent poisoning, resulted in partial depopulation with initial recolonisation predominantly by dispersing males. Results from both study areas showed that young males have a greater tendency to disperse from their native area than do young females. Radiotelemetry revealed that possums in the MSA used more dens than those in the FRSA and good dens appeared to be few in the latter area. It is suggested that dens may be a limiting resource for some possum populations. Since females are known to control the use of dens the survival of males should be poorer where dens are limited, resulting ultimately in a biased sex ratio. Experimental depopulation of the FRSA and monitoring of its recolonisation over one year suggested that population re-establishment on cleared areas does not depend on local reproduction by survivors, but is primarily by dispersal in the initial stages, with an early influx of young males. The MSA population was also poisoned, in a standard 1080 airdrop, and the effectiveness of this operation was monitored. Current control practices are critically appraised in the light of the results obtained in this study and the value of widespread aerial poisoning operations in pine plantation habitats is questioned.

Damage caused by possums (Trichosurus vulpecula Kerr) in New Zealand's extensive Pinus radiata plantations has caused concern among foresters. This study set out to examine the nature of tire problem and investigate the ecology of possums in radiata plantations in relation to damage and control. The work was carried out in the Kinleith Forest near Tokoroa in the central North Island. A review of existing literature and survey results showed that damage is mainly a problem of young plantations, consisting of bark-stripping on young trees and browsing of newly-planted seedlings. A simulated browsing experiment indicated that the latter damage was unlikely to result in discernible production losses. Bark-stripping was found to occur during the winter and spring. It had a patchy distribution and was only thought likely to prove serious where stocking was already low for other reasons. Analysis of stomach contents from animals poisoned in 1971 plantings and 1960 age class stands revealed that in both habitats possums relied heavily on foods other than pine, although in the older (1960) stands radiata pollen cones were an important winter and spring food. Insect larvae (Philia nigrostigma) were also eaten at this time of year, particularly in older stands. Little bark was consumed in either habitat, but it was a more common food in the younger stands, were it was eaten during the winter and spring. It is suggested that bark-stripping in young stands may be a response to relatively poor nutrition during the winter and early spring. Data on fat reserves, reproductive performance and growth support the view that the overall plane of nutrition was better among possums in the older stands. Possum populations were studied by livetrapping and radiotelemetry in two areas, one within a 1960 age class radiata stand (FRSA), the other extending across the boundary between a 1971 planting and cutover native forest (MSA). In the latter area there was a seasonal pattern of habitat use, with animals tending to use the native forest to a greater extent than the plantation during the winter. Population densities were similar in the two areas (2-3/ ha), with the MSA population having an apparent trend of increase. The two populations differed in composition, the FRSA one having an excess of females and the MSA an initial excess of males but an increasing proportion of females. It is suggested that disturbance of the MSA population, by burning in 1971 and subsequent poisoning, resulted in partial depopulation with initial recolonisation predominantly by dispersing males. Results from both study areas showed that young males have a greater tendency to disperse from their native area than do young females. Radiotelemetry revealed that possums in the MSA used more dens than those in the FRSA and good dens appeared to be few in the latter area. It is suggested that dens may be a limiting resource for some possum populations. Since females are known to control the use of dens the survival of males should be poorer where dens are limited, resulting ultimately in a biased sex ratio. Experimental depopulation of the FRSA and monitoring of its recolonisation over one year suggested that population re-establishment on cleared areas does not depend on local reproduction by survivors, but is primarily by dispersal in the initial stages, with an early influx of young males. The MSA population was also poisoned, in a standard 1080 airdrop, and the effectiveness of this operation was monitored. Current control practices are critically appraised in the light of the results obtained in this study and the value of widespread aerial poisoning operations in pine plantation habitats is questioned.

Damage caused by possums (Trichosurus vulpecula Kerr) in New Zealand's extensive Pinus radiata plantations has caused concern among foresters. This study set out to examine the nature of tire problem and investigate the ecology of possums in radiata plantations in relation to damage and control. The work was carried out in the Kinleith Forest near Tokoroa in the central North Island. A review of existing literature and survey results showed that damage is mainly a problem of young plantations, consisting of bark-stripping on young trees and browsing of newly-planted seedlings. A simulated browsing experiment indicated that the latter damage was unlikely to result in discernible production losses. Bark-stripping was found to occur during the winter and spring. It had a patchy distribution and was only thought likely to prove serious where stocking was already low for other reasons. Analysis of stomach contents from animals poisoned in 1971 plantings and 1960 age class stands revealed that in both habitats possums relied heavily on foods other than pine, although in the older (1960) stands radiata pollen cones were an important winter and spring food. Insect larvae (Philia nigrostigma) were also eaten at this time of year, particularly in older stands. Little bark was consumed in either habitat, but it was a more common food in the younger stands, were it was eaten during the winter and spring. It is suggested that bark-stripping in young stands may be a response to relatively poor nutrition during the winter and early spring. Data on fat reserves, reproductive performance and growth support the view that the overall plane of nutrition was better among possums in the older stands. Possum populations were studied by livetrapping and radiotelemetry in two areas, one within a 1960 age class radiata stand (FRSA), the other extending across the boundary between a 1971 planting and cutover native forest (MSA). In the latter area there was a seasonal pattern of habitat use, with animals tending to use the native forest to a greater extent than the plantation during the winter. Population densities were similar in the two areas (2-3/ ha), with the MSA population having an apparent trend of increase. The two populations differed in composition, the FRSA one having an excess of females and the MSA an initial excess of males but an increasing proportion of females. It is suggested that disturbance of the MSA population, by burning in 1971 and subsequent poisoning, resulted in partial depopulation with initial recolonisation predominantly by dispersing males. Results from both study areas showed that young males have a greater tendency to disperse from their native area than do young females. Radiotelemetry revealed that possums in the MSA used more dens than those in the FRSA and good dens appeared to be few in the latter area. It is suggested that dens may be a limiting resource for some possum populations. Since females are known to control the use of dens the survival of males should be poorer where dens are limited, resulting ultimately in a biased sex ratio. Experimental depopulation of the FRSA and monitoring of its recolonisation over one year suggested that population re-establishment on cleared areas does not depend on local reproduction by survivors, but is primarily by dispersal in the initial stages, with an early influx of young males. The MSA population was also poisoned, in a standard 1080 airdrop, and the effectiveness of this operation was monitored. Current control practices are critically appraised in the light of the results obtained in this study and the value of widespread aerial poisoning operations in pine plantation habitats is questioned.