Companion animal health and disease: a perspective 1952-2002

Cat-exclusion zones in rural and urban-fringe landscapes: how large would they have to be?

Context. The process of urban sprawl brings the human population and their domestic cats (Felis catus) in close contact with wildlife in areas that were previously remote, including reserves and conservation areas created to protect populations of vulnerable or threatened species. Various mitigation measures have been proposed, including devices designed to hinder cat hunting ability, desexing to reduce wandering and nuisance behaviours, containment at night or at all times and regulations governing cat ownership. Such regulations may aim to reduce cat densities by limiting the number of cats per household, or they may define zones around sensitive conservation areas where cat ownership is prohibited. Aims. The present study sought to establish the necessary size of cat-exclusion zones in rural and urban-fringe landscapes where vulnerable prey species may also reside. Methods. With GPS collars, we tracked 38 domestic cats at three sites (one rural, two urban fringe) where small reserves contained threatened lizard species. Key results. Home ranges (95% kernel density estimates) were considerably larger for cats at the rural site (0.3–69 ha) than at urban-fringe sites (0.35–19 ha at Kaitorete Spit and 0.2–9 ha at Otago Peninsula), and were larger at night than day. Resource selection ratios indicated avoidance of open areas with little cover, such as cultivated areas (farmland), tussock grassland and duneland, whereas sources of cover such as trees and buildings were preferred. Maximum distances moved and large variability between individual cats suggest buffers in rural landscapes would need to be at least 2.4 km wide, whereas those in urban-fringe habitat could be half as large. Conclusions. Despite significant home-range size differences exhibited by cats living in rural v. urban-fringe habitats, exclusion zones would need to be wide to account for considerable inter-cat variation in movement behaviour. Implications. The size of an effective cat-exclusion zone should represent the specific landscape, amount of residential development and substantial variability between individual cats.

Veterinary epidemiology in New Zealand: a 50-year perspective

Abstract Extract The science of epidemiology is still developing although some of its principal tenets, such as identification of risk factors through comparisons of rates of disease occurrence among population sub-groups of individuals, have been used for centuries. The past 50 years has seen a particularly rapid period of growth of the discipline that has become almost exponential, especially since microcomputers and powerful analytical programs became widely available in the 1980s. The most outstanding advance has arguably been the development of causal criteria that arose from the fierce debate about links between smoking and lung cancer. The philosophical concepts of associations between cause and effect that are embodied in causal criteria now underpin epidemiological practice for scientific evaluation of evidence.