Kererū declined rapidly following European settlement in New Zealand, and they remain at a reduced density. We assessed three sources of information to test the hypothesis that predation by introduced mammals and abundance of food resources are the two major factors determining kererū abundance across New Zealand. First, we reviewed the literature on factors affecting the vital rates of kererū. This analysis showed that predation is the cause of most nest failures and deaths in kererū.
There are many examples in the literature of a positive correlation between the distribution of a species and its local abundance, i.e., widely occurring species tend to be more abundant locally when they do occur. Such relations have been documented over a wide range of taxa and spatial scales. There are five major hypotheses seeking to explain the relation: Random placement, Sampling error, Niche width, Demography, and Metapopulation dynamics. However, there is little evidence to distinguish between them, especially for plants.
Chamois (Rupicapra rupicapra) are usually considered an alpine species in New Zealand, but also occur in forests in areas such as Westland. A postal survey of commercial helicopter-based hunters indicated that chamois are present within Westland forests from timberline to sea level and are most abundant within an area of about 1600 km(2) extending from the Wanganui River in the north to the Karangarua River to the south. The diet of 40 chamois shot in spring and summer was determined by analysis of rumen contents.
Two tree weta Hemideina ricta and H. femorata are predominantly allopatric on Banks Peninsula (South Island, New Zealand) except for four small areas of overlap. H. ricta was found over the outer eastern portion of Banks Peninsula including the eastern slopes of Akaroa Harbour whereas H. femorata was usually lower down on the eastern edge of Akaroa Harbour and west of this. H. ricta ranged from 20 m to 806 m in altitude whereas all H. femorata were found below 450 m. Ninety-four per cent of H.
Populations of ship rats (Rattus rattus), Norway rats (R. norvegicus), feral house mice (Mus musculus), stoats (Mustela erminea), weasels (M. nivalis), and ferrets (M. furo) were sampled with killtraps every three months from November 1982 to November 1987 in logged and unlogged native forest and in exotic plantations of various ages at Pureora Forest Park, central North Island. Mice (n=522 collected) were fewest in unlogged native forest, more abundant in road edge cutover forest, and most abundant in a young (5-10 year old) plantation.
Historical and recent records indicate that kiwi are less numerous and widespread in Hawke's Bay than they used to be. The birds are still scattered throughout the ranges to the west and north of the region, usually at densities of about one bird per 100 ha. Kiwi have now almost completely disappeared from their former lowland habitats. The decline of kiwi in Hawke's Bay may have started before European settlement, but has been particularly rapid in the last 70 years. RePeat surveys of three populations between 1984 and 1990-91 indicate that the decline is continuing.
Replacing native forests and grasslands with plantations, pastures and crops has resulted in both contraction of ranges and exploitation of modified habitats by native species, and both general and restricted dispersal of introduced species of soil fauna. Contraction is shown by native earthworms, land snails, ring nematodes and various arthropods, while the areas with changed land use suggest certain native insects are more numerous than 150 years ago. Damage to pastures by grass grub and porina show clearly how native species can exploit modified habitats.
The breeding ranges of thar are described as they were in 1976 and 1984 and compared with previously described ranges in 1936, 1946, 1956 and 1966. Commercial hunting during 1972-1976 harvested about 32000 thar and along with habitat limits in some areas this slowed the rate of dispersal into new areas and eliminated thar from the periphery of their range in other areas. The rate of thar dispersal from the time of their liberation in 1904 until 1936 was non-linear and recalculation of their breeding ranges from 1936-1966 shows rates of dispersal consistent with an exponential curve.
Goats were liberated on Raoul Island early in the 19th century. Attempts to eliminate the goats commenced in 1937 and have accounted for at least 15 000 animals. Since 1972, when annual hunting expeditions began, both the number of goats and the area over which they range have steadily declined and the herd is now almost extinct. Despite these changes, the mean group size of goats in 1981-83 remained the same at 3.19, 2.74 and 3.24 respectively. On average, 19% of goats escaped each encounter with the hunters.