Parasitism, disease and breeding ecology of little blue penguins (Eudyptula minor) on Tiritiri Matangi Island, New Zealand : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Auckland
According to the New Zealand Threat Classification, little blue penguin (LBP) (Eudyptula
minor) populations are under ‘gradual decline’. Although long-term data are available for
some mainland populations, the status of LBP on offshore islands remains largely unknown.
Most studies have focussed on breeding success and foraging ecology. However, there is a
paucity of data pertaining to diseases and parasites, and the potential effects of these factors
on LBP health, reproductive success and survival. To date, the LBP population on Tiritiri
Matangi Island, Hauraki Gulf, Auckland, New Zealand, has only been monitored periodically,
despite the island being an important habitat for LBP throughout their annual cycle. The
overall aim of this study was to examine the relative importance of parasites and disease in
relation to key aspects of LBP life-history, including: the annual cycle; reproductive success;
energetic demands, immunity; and mortality.
During 2006 and 2007, the reproductive success of LBP on Tiritiri Matangi Island was
investigated with respect to lay date, nest site attributes, parental quality and ectoparasite
loads. A nest treatment experiment was conducted to explore flea (Parapsyllus longicornis)
and tick (Ixodes eudyptidis) effects on breeding success. Overall reproductive output was
low, estimated at 33.3%, with an average of 0.67 chicks fledged per pair. Lay date and body
condition (BC) appeared to be the main drivers of reproductive success, with early breeders
fledging significantly more chicks than late breeders. Increased BC improved reproductive
success. Although late breeders exhibited higher BC scores, increased chick mortality
indicated that late nests face a reproductive trade-off. Treatment did not prove effective in
reducing ectoparasite loads and there was no correlation between ectoparasite abundance in
the nest and reproductive success.
Throughout their geographic distribution, penguins are host to a range of ectoparasites.
Using Ixodes eudyptidis ticks as indicators, ectoparasite-host dynamics were investigated
over the course of one year, in relation to LBP life stages, body condition (BC) and
haematological parameters. To investigate the presence of vector-borne diseases, blood
parasite prevalence was determined using molecular techniques and microscopy. Tick load
exhibited significant seasonal variation, being highest during periods of increased host
availability i.e. moult and breeding. However, these increases in abundance were not
associated with body condition or decreased reproductive success of adults. Nonetheless,
LBP exhibited seasonal fluctuations in haematological parameters, with decreases in white
blood cell concentrations during periods of increased energy demands and high tick loads.
Blood parasite prevalence was low (<1%), determined to be Plasmodium sp. infection. No
other blood parasites were found. These results indicate that the lifecycle of I. eudyptidis is
tightly linked with that of its LBP hosts, and that infested individuals exhibit physiological
responses to tick load.
LBP exhibit annual fluctuations in mortality and experience periodic mass mortalities. To
examine factors associated with mortality, post-mortems were conducted on 32 LBP from the
Hauraki Gulf. Additionally, 128 LBP necropsy records were obtained from the National
Wildlife Database (HUIA) for the period spanning April 1993-January 2009, and the causes of
mortality were reviewed. Starvation and disease accounted for the highest mortality levels,
with 65% of deaths attributed to either one or both of these factors. Furthermore, there was a
strong association between starvation and parasites. Parasitic disease and diseases of
uncertain aetiology were the most common disease types. In all age groups, the likelihood of
infectious, non-infectious and disease of unknown aetiology was significantly higher in LBP
that harboured one or more parasite species. Results from this study suggest that starvation
and disease, including parasites, are significant factors associated with mortality of LBP in
New Zealand, as has been found in Australian LBP populations.
Parasites and disease are increasingly recognised as a challenge to the conservation of
wildlife, and information regarding endemism of pathogens and parasites within populations
is vital for determining ecosystem health, and identifying aberrant diseases.
Appendix 4.4 removed due to copyright restrictions:
Suepaul, R.B., Alley, M.R., Jansen van Rensburg, M., 2010, Salt gland adenitis associated with bacteria in blue penguins (Eudyptula minor) from Hauraki Gulf (Auckland, New Zealand). Journal of Wildlife Diseases, 46(1) : 46-54.