As part of a health survey of New Zealand sea lions (Phocarctos hookeri) on Enderby Island, Auckland Islands (50°30’S, 166°17’E), neonatal mortality was continuously monitored at the Sandy Bay Beach rookery, from 1998/1999 to 2004/2005. The primary causes of death were categorised as trauma (35%), bacterial (24%) and hookworm (13%) infections, starvation (13%) and stillbirth (4%). During the 2001/2002 and 2002/2003 breeding seasons, bacterial epidemics caused by Klebsiella pneumoniae increased mortality by three times the mean in non-epidemic years. Uncinaria spp. from New Zealand sea lion (NZSL) pups was described for the first time using morphometric criteria. It differed from the two species already described in pinnipeds, Uncinaria lucasi and Uncinaria hamiltoni, suggesting the existence of a different morphotype in NZSLs. A study on the epidemiology of hookworm infection showed that all pups up to at least three months of age harboured adult hookworms in their intestines and transmammary transmission was identified as the route of infection of NZSL pups. Uncinariosis as a primary cause of mortality was generally associated with anaemia, haemorrhagic enteritis and frank blood in the lumen. The relationship between hookworm burden and clinical disease could not be clearly established. The 2001/2002 and 2002/2003 bacterial epidemics at Sandy Bay Beach rookery were caused by a clonal strain of Klebsiella pneumoniae as verified by pulse-field gel electrophoresis and antimicrobial testing. Suppurative arthritis was the most common post-mortem diagnosis during the two epidemic seasons. Internal lesions were consistent with septicaemia, which explained the wide range of organs from which the pathogen was grown in pure culture. A serological test investigating the exposure of NZSLs to Klebsiella spp. showed that the large majority of pups up to two months of age did not have any anti-Klebsiella antibodies, even after the epidemics, but that almost all the adults were seropositive. In addition, passive immunoglobulin (Ig) transfer from lactating females to neonates was examined by measuring IgG levels in pups and was very low compared to terrestrial mammals although similar to other pinniped neonates.

The objectives of the present study were to: 1) describe the gross chemical milk composition of the New Zealand sea lion (NZSLs), Phocarctos hookeri, in early lactation; 2) validate an analytical method for sea lion milk composition; 3) investigate a series of temporal, individual and dietary factors that influence the milk composition of the NZSL and; 4) investigate the temporal and spatial differences in the fatty acids signatures of sea lion milk. A comprehensive literature review revealed that data on milk composition in otariid species is either missing or limited, that to be able to fully describe their milk composition extensive sampling was required and that the temporal, maternal and offspring factors that influence milk composition in pinnipeds are poorly understood. The review identified that considerable work has been conducted to infer diet via the application of fatty acids signature analysis of milk and blubber. There are many factors (i.e. metabolism, de novo synthesis and endogenous sources) that contribute to the differences in fatty acid composition between the diet and milk or blubber. Milk samples from NZSL were used to test whether a new method would give similar results as the standard methods of milk analysis. Agreement between analytical methods for milk components was assessed using different measures of statistical fitness and the results indicated that the new method was comparable to the standard methods and applicable to the milk of sea lions, pinnipeds and to ecological studies of lactation. Milk from NZSLs was collected over a period of seven years (1997, 1999 to 2003, and 2005) in early lactation to describe the composition of milk of NZSL and to test for differences between years. The results indicated that: i) the milk protein concentration was comparable to other species of pinnipeds; ii) the milk fat concentration and the milk energy content of NZSL is the lowest reported for otariids in early lactation; however iii) the milk fat concentration was significantly different between years. These results suggested that the milk composition of NZSLs was influenced by annual changes in the environment; however, there may be other unidentified factors. Month, maternal body condition, age, body weight and length, offspring sex and age, and attendance pattern were compared with milk components. The results identified that month, maternal body condition and age significantly affected milk fat concentration. These results and the fact that maternal body condition varied significantly between years and mothers nursing male pups had lower body condition and produced milk lower in energy content suggested that local food resources along with other unidentified factors have an effect on the reproductive success of NZSLs. To test whether the fatty acid signature analysis (FASA) of lipid rich tissues (milk, blubber and serum) of otariids could be used to infer diet a mixture of vegetable oil (with distinctive fatty acid signature) was fed to 24 lactating NZSL and tissue samples were collected at different time intervals. Significant increases in the concentration of specific fatty acids in serum and milk were observed with peaks within 12hrs and 24hrs respectively of ingestion. Concentrations in milk remained elevated for up to 72hrs and there were differential rates of incorporation into milk. These findings confirm the potential of FASA to infer the composition of the diet. The variation in milk fatty acid signatures from lactating NZSL from four years (1997, 2003, 2004 and 2005) of sampling were measured in order to test whether differences occurred between years. Fatty acids signatures from five potential prey species including the commercially important arrow squid were incorporated into the analysis to associate the changes in milk fatty acids with a shift in prey choice. The results indicated that milk fatty acid signatures were different in 1997 and 2003; however, it was not possible to relate these differences to the five prey species. The variability in the annual arrow squid catch data suggested that local food resources around the Auckland Islands may also be variable. In conclusion, the milk produced by the NZSL has the lowest concentration of fat and energy in early lactation reported for any otariid species. The main factors that contributed to changes in milk quality were stage of lactation, year and maternal body condition. The yearly variation in the quality of milk appears to be a result of their lactation strategy or to variable local food conditions that also affect maternal body condition. Therefore monitoring the annual milk quality may be a means to monitor the health of a pinniped population and potential management tool for pinniped species. This thesis has shown that annual changes in the diet of NZSL can be assessed with milk fatty acid signatures.