Two techniques for assessing possum (Trichosurus vulpecula Kerr) diet from stomach contents ("point-sampling" and "layer- separation") are described and compared. Point-sampling involves sieving stomach contents, systematically selecting fragments from the retained material then, identifying and weighing these. Layer-separation involves separation, identification, and weighing of the discrete layers apparent in most possum stomach contents. In 41 of 43 stomachs examined, we were able to separate discrete layers that nearly always comprised a single food item.
We monitored the behaviour of 62 radio-collared ferrets and 25 radio-collared cats in dry, tussock grassland habitat in New Zealand's South Island. The total home range of adult male ferrets (102 ± 58 ha, mean ± 1 s.d.) was marginally greater than that of females (76 ± 48 ha), and averaged 90 ± 55 ha. Male ferret core ranges (27 ± 15 ha) were larger than those of females (16 ± 8 ha). Adult cat home ranges were similar between sexes, and were larger and more variable than those of ferrets (225 ± 209 ha). Core range size of cats was similar between sexes and averaged 54 ± 24 ha.
Possum leaf diet from 1976 to 1989 in the Orongorongo Valley was compared with the diet recorded from four previous years, using faecal analysis. There were large differences in the proportions of species eaten in different seasons and between different years. There was little overall change in the proportion of the main diet tree species, Metrosideros robusta and Weinmannia racemosa, and seasonal increases or declines in one were usually balanced by opposite changes in the other.
Food of the North Island kaka (Nestor meridionalis septentrionalis) on Kapiti Island was identified while quantifying the foraging activity of nine radio-tagged birds from March 1991 to January 1992. Additional food types were identified by opportunistic observation of feeding birds and qualitative examination of nestling faeces. A diverse range of food was taken, including wood-boring invertebrates, scale insects, seeds, nectar or pollen, fruits, and sap.
The Humped-back theory of plant species richness, a theory related to Grime's C-S-R 'triangular' model, has been widely discussed, and some evidence has been claimed in support of it. The theory suggests that species richness is maximal at intermediate levels of productivity, i.e., at intermediate positions on a stress/favourability gradient. We sought evidence for the theory from 90 stands of native podocarp/broadleaved and beech forest in the Coastal Otago region, with an adjustment made for the effect of stand area on species richness.
The objective of this study was to quantify the population dynamics, morphological characteristics, and diet of rodents on Rangitoto Island (Hauraki Gulf, New Zealand) to provide information for the future development of an eradication strategy. An aerial 1080 operation to eradicate possums and wallabies was carried out two months after the study began. The effects of this operation on rodent population dynamics are discussed. Both ship rats (Rattus rattus) and mice (Mus musculus) were trapped on Rangitoto Island over a 15 month period.
We examined possum trapping data collected from 1945 to 1989 in the Pararaki catchment to assess whether there was any evidence for a major natural decline in possum numbers several decades after colonisation and whether the population has subsequently shown any long-term trend in abundance. The catchment was probably colonised by possums around 1915-20. We found evidence for a major decline (c. 80%) in possum numbers between 1945 and 1965. There was no significant trend in our trap catches from 1965 to 1976, but in 1977 there was a further abrupt decline.
Hawthorn (Crataegus monogyna) is a naturalised tree that is classified as a noxious plant in several counties in the eastern South Island. It is locally abundant in lowland forest remnants, and with the indigenous spiny shrub matagouri (Discaria toumatou), on grazing land in Canterbury. Two scrub sites near Porters Pass, where the original hawthorn trees still existed, and a forest site near Kowai Bush were sampled by measuring stem diameters and counting growth rings, to determine the age structure and dynamics of hawthorn.
Seventeen exclosures were built by the New Zealand Forest Service within Urewera forests over the period 1961-68 to exclude ungulates. Forest structure and species composition inside and outside these exclosures were compared in 1980-81. Some relatively shade tolerant species such as the fern Asplenium bulbiferum, the liane Ripogonum scandens, the sub-canopy shrubs Geniostoma ligus,Trifolium and Coprosma australis and the canopy species Beilschmiedia tawa were less abundant in certain tiers outside the exclosures than inside.
Tree trunks are important links between the forest floor and canopy, especially for flightless invertebrates that move from the forest floor to feed or breed in the canopy. Traps were used to sample invertebrates moving up and down on mahoe (Melicytus ramiflorus), hinau (Elaeocarpus dentatus), hard beech (Nothofagus truncata), and kamahi (Weinmannia racemosa). In 19 months 22 696 invertebrates were collected. Many unexpected groups e.g.