Urban Rats in Wellington: Estimating Home Ranges, Population Densities and Detection Probabilities

• Main Author: Mackenzie, Henry
• Format: Thesis
• Language: unknown
• Published: 2021
• Subjects: Ethology and Sociobiology; Ship rat; Spatial ecology; Urban; Detection probability; 060304 Ethology and Sociobiology; School: School of Biological Sciences; Degree Discipline: Biological Sciences; Degree Name: Master of Science; Degree Level: Masters; New Zealand; Norway; Petersen; Rattus rattus
• Online Access: https://doi.org/10.26686/wgtn.14347997.v1; https://figshare.com/articles/thesis/Urban_Rats_in_Wellington_Estimating_Home_Ranges_Population_Densities_and_Detection_Probabilities/14347997

The ship rat (Rattus rattus) and Norway rat (Rattus norvegicus) are prolific pest species with a near- global distribution. Their spread has had serious public health repercussions as carriers of disease and by causing considerable agricultural losses. They are also invasive to many native ecosystems, degrading ecosystem processes, and preying upon native species, resulting in significant losses to biodiversity. This study aims to guide more effective rat management strategies through an increased understanding of the spatial ecology of rats in an urban environment. Three separate studies were conducted, all located in Wellington, New Zealand: 1)A radio-telemetry study looked at the home range and spatial behavior of 10 urban ship rats. Results showed comparatively small home ranges (0.01 - 0.45 ha at 100% minimum convex polygons) with maximum linear distances within a home range of 19-74m. There was significant spatial overlap between home ranges– up to 90% (between two adjacent home ranges); co-nesting behavior between both sexes; frequent diurnal activity amongst ship rats (9 of 10 rats); and two longer distance dispersal events (~120m) by ship rats. Implications for rat management include: a need for tighter spacing of devices in urban habitats for control and detection of survivors, potentially every 20-25m if eradication is the goal. 2)A capture mark re-sight study to estimate the minimum density of ship rats in an 0.63 ha urban bush fragment. A total of five rats were live caught in cage traps and uniquely marked before release. An additional eight wild rats were uniquely identified on cameras based on distinctive features of their appearance. A conservative Lincoln-Petersen estimate was used to estimate the number of rats within the bush fragment: this produced an estimate of 14.6 rats with 95% confidence intervals [7.69-55.6], which translates to a density of 23.2 rats/ha [12.2-88.25]. These densities are significantly higher than those found in most mainland studies and more comparable to those in ...