Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Establishment of a stable isotope database for New Zealand fur seal breeding colonies using δ13C and δ15N in pup vibrissae(Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2025-05-21) Galbraith D; Chilvers BL; Bilgmann KThe New Zealand fur seal/kekeno (Arctocephalus forsteri, NZFS) is native to Aotearoa/New Zealand. Its original range included the entire coast of mainland New Zealand, and offshore and subantarctic islands. The NZFS has gradually recolonised much of its former range after being almost extirpated by hunting, however, little is known about species dispersal in the non-breeding season. Stable isotope analysis (SIA) can trace foraging ecology and migration in marine mammal species. Isotopic niche width can be described statistically and provides ecologically relevant information on diet and potentially foraging location. Otariid pup vibrissae (whiskers) can be used as proxies for maternal foraging as they provide a sequential record of nutrient intake derived from maternal milk. In this study, vibrissae from NZFS pups were collected from seven established breeding areas around the coast of New Zealand. A stable isotope database of δ13C and δ15N was established for each breeding colony, and isotopic niche widths estimated. Isotopic niche widths were largest at Open Bay Islands and Cape Foulwind. Results were discussed in light of previous oceanographic and NZFS diet and foraging studies. Colonies are not likely to be sufficiently isotopically distinct for pups to be identified to their colony of origin.Item Infection dynamics in ecosystems: on the interaction between red and grey squirrels, pox virus, pine martens and trees(The Royal Society Publishing, 2021-10) Roberts MG; Heesterbeek JAPEcological and epidemiological processes and interactions influence each other, positively and negatively, directly and indirectly. The invasion potential of pathogens is influenced by the ecosystem context of their host species’ populations. This extends to the capacity of (multiple) host species to maintain their (common) pathogen and the way pathogen dynamics are influenced by changes in ecosystem composition. This paper exemplifies these interactions and consequences in a study of red and grey squirrel dynamics in the UK. Differences and changes in background habitat and trophic levels above and below the squirrel species lead to different dynamic behaviour in many subtle ways. The range of outcomes of the different interactions shows that one has to be careful when drawing conclusions about the mechanisms and processes involved in explaining observed phenomena concerning pathogens in their natural environment. The dynamic behaviour also shows that planning interventions, for example for conservation purposes, benefits from understanding the complexity of interactions beyond the particular pathogen and its threatened host species.Item Long-term changes in the breeding biology of a New Zealand bellbird population suggest plasticity in life-history responses to ecological restoration(2021-01-19) Roper MM; Aaron MTH; Brunton DHEcological restoration projects provide excellent opportunities to study how animals adapt their life-history strategies in response to changeable environments. A fundamental way animals can optimise reproductive success in changing conditions is trading-off aspects of their breeding system. The New Zealand bellbird ( Anthornis melanura ) has had a long-term presence on the small restoration island, Tiritiri Matangi Island (Tiri), spanning the island’s degraded agricultural past to its current extensively restored state. We studied the breeding biology of this bellbird population to assess how their reproductive life-history strategies have responded over time to the restoration on Tiri. We compared the current breeding data (2012–2016) of the bellbirds with data from between 2001–2010 (including Baillie, 2011, Cope, 2007), and from 1977–1978 (Anderson and Craig, 2003), prior to the island’s restoration. We also explored associations between abiotic/biotic factors and bellbird reproductive success for the most recent period (2012–2016). Our main finding was that clutch size significantly declined over time from a mean of 3.6 to 2.4 eggs per nest and this decline correlated with increasing population density. This is consistent with a density dependent effect, although further data are required to empirically test this conclusion. Overall, the earliest spring laying dates were in late August and the latest extended to January, with all chicks fledged by the end of February. Nest success was 47% (range 40 – 54%) across 2012–2016, falling within a similar range as previous studies. We found little effect of year, weather, parental age or morphometrics on reproductive success. We observed directional change in patterns of parental investment between 1977–1978 and 2012–2016; in 2012–2016, parents persisted with raising single broods rather than abandoning and re-nesting to raise larger broods. These results suggest that the bellbirds’ life-history traits are plastic in response to local conditions which provides an advantage when repopulating a regenerating or changing habitat.