Cats (Felis catus) are among the most damaging invasive predators in the world, and their impacts in Aotearoa New Zealand (NZ) are particularly severe. However, unlike the invasive predators that are targeted for eradication under the Predator Free NZ initiative, cats are also highly valued by people and therefore will likely remain widespread in NZ for the foreseeable future. This raises the question of how to manage the impacts of cats, which include predation, competition, and disease affecting native species, livestock, and humans.
Two of New Zealand's most important insect pests, grass grub and porina, are endemic species which have successfully colonised improved pastures. Population densities of these insects within this new environment are far greater than in the native plant systems in which they evolved. Within these high populations diseases have flourished, and high numbers of diseases are recorded from each of these pests. These include bacteria, fungi, nematodes, viruses and protozoa.
Many cabbage trees (Cordyline australis) are dying throughout much of the North Island and the northern South Island of New Zealand. The symptomatology of those dying in urban environments is described, and is concluded to be consistent with the hypothesis that death is caused by a biotic agent entering through a leafy tuft of the branch system. This disease, which has been named Sudden Decline, usually leads to almost total defoliation of affected trees within 2-12 months. Disease incidence has increased linearly at about 11% per annum since 1987/88. Cultivated trees of C.
In 1995 and 1996, release of 51 hihi (stitchbird, Notiomystis cincta) onto Tiritiri Matangi Island (wild caught on Hauturu, Little Barrier Island) marked the start of a research and ecological restoration success story. Although establishment of populations of hihi elsewhere in New Zealand has proven to be difficult, the population on Tiritiri Matangi Island has grown to c. 150 individuals and has become one of New Zealand’s few detailed case-study species.
A common question that arises when considering the results from a well-designed sampling programme for a rare or invasive species is: ‘Sampling has failed to detect a species that could have been present, so can we calculate the probability that it truly was absent during the sampling period?’ Noting that this invokes a Bayesian view of ‘probability’, which therefore must be accepted if the question is to be answered in the affirmative, we present a method of addressing it.
Holdaway (1989) described three phases of historical extinctions and declines in New Zealand avifauna, the last of which (Group III, declining 1780–1986) was associated with European hunting, habitat clearance, and predation and competition from introduced European mammals. Some forest bird species have continued to decline since 1986, while others have increased, usually after intensive species-specific research and management programmes.