Understanding the distribution of introduced mammalian predators in an urban environment using monitoring tools and community trapping

<p>Introduced mammalian predators are one of the largest conservation threats to New Zealand native flora and fauna, and there is an increasing concern about their presence in urban environments, coupled with a recognition that cities present a unique opportunity for ecological restoration, due to the availability of a large number of volunteers and options for intensive management of green spaces and gardens. Predator control is an essential step towards the ecological restoration of urban environments, however, it requires an understanding of the factors influencing the distribution of these mammalian predators before successful control operations can be implemented. Few studies have investigated mammalian predators in urban environments, and there is little certainty about what drives their distribution in these environments. This thesis used simple mammal monitoring techniques and trapping data to investigate the distribution of mammalian predators within broad scale urban environments, with the aim of identifying drivers of their distribution. Chew cards and tracking tunnels collected across three New Zealand cities were assessed for their efficacy as accurate monitoring devices in urban environments. In Chapter 2, monitoring devices were cross-checked between observers to assess the level of consistency in interpretation of chew and tracking marks. The consistency of chew card and tracking tunnel identifications was relatively high overall and were not substantially influenced by the city of identification, or the duration of card exposures. Monitoring devices were also assessed for their change in sensitivity between one and six-night exposures. Both devices were effective at detecting rats, however, tracking tunnels showed greater sensitivity and consistency in detecting mice and hedgehogs, whereas chew cards were better suited to the monitoring of possums. Neither device was particularly effective at detecting mustelids or cats. In Chapter 3, mammalian predators were monitored across 24 monitoring lines in autumn, 2018, and results were compiled with spring 2017 and autumn 2018 data, pre-collected in two other cities, following the same procedures. There were distinct differences in the broad-scale habitat utilisation of rats, mice, hedgehogs, with possums being the only species to show a strong preference for urban forests. Only two of the tested microhabitat variables had an influence on species distributions. Detection of rats declined with increasing distance to the coast, and the increase in human population size was related to a significant increase in hedgehogs. There was a strong seasonal difference on the influence of local trap density and the detection of mammals. The increase in trap density within 25-50m radii was significantly related to a decrease in rat and hedgehog detections. Overall, there are substantial differences between the distributions of species in an urban environment. Trapping is one of the main methods of predator control in New Zealand, and is already widespread within urban and suburban Wellington. In Chapter 4, I compiled trap data from 22 community trapping groups operating in residential and reserve areas in Wellington City. Residential groups (“backyard trappers”) used a high proportion of Victor and various rat and mouse traps, which was strongly linked to their high number of rat and mouse catches. Groups trapping in reserves used a high proportion of DOC 200, Victor and A24 traps, however, fewer hedgehogs were caught compared to residential areas. Catches were significantly influenced by various landscape variables. An increased distance of traps to streams led to significantly higher catches of rats, conversely, proximity to streams resulted in significantly higher catches of mice and hedgehogs. Although few catches of weasels were reported, traps closer to the coast and to forest fragments caught significantly more individuals. The research in this thesis contributes to the small body of research conducted on mammalian predators within urban environments. The findings in this thesis can assist with the current and future predator management programmes, by highlighting areas of potential significance, particularly in Wellington.</p>

Understanding distributions of invasive mammals in urban environments using remote cameras and citizen science

<p>Preserving biodiversity in urban environments is crucial not only for preventing local extinctions of native species, but also for educating the public about the importance of species conservation. Invasive mammalian species can have negative impacts for both people and biodiversity in urban environments. Understanding the factors influencing the distribution of these invasive species is crucial to comply with the ethical, ecological, and practical concerns associated with their management. Remote cameras are an increasingly popular tool for investigating the distribution and abundance of mammals. Yet few studies have used these cameras in urban environments. The time and effort required to classify remote camera data is the main constraint of this monitoring technique. To determine whether employing citizen science could facilitate the use of remote cameras in urban environments, I investigated the engagement, accuracy, and efficiency of volunteers (i.e., citizen scientists) in classifying animal images recorded by remote cameras in Wellington, New Zealand. Classifications from citizen scientists were in 84.2% agreement with classifications of expert ecologists. However, accuracy varied significantly among species and volunteers. Aggregating multiple classifications per image and highlighting animal movement in the images improved the accuracy of citizen scientists. Additionally, weighting their classifications based on previous accuracy, self-assessed confidence, and the species reported reduced the number of volunteer classifications required to achieve levels of accuracy comparable to that of experts. These results illustrate that citizen science allows for accurate and efficient classifications of remote camera data from urban areas. Using the classifications provided by citizen scientists, I then evaluated the suitability of remote cameras to monitor invasive mammals in urban environments. Based on data collected from forest and residential areas of Wellington, New Zealand, remote cameras detected significantly more European hedgehogs (Erinaceus europaeus) and rats (Rattus spp.) than tracking tunnels. Cameras, however, missed recording house mice (Mus musculus) on some occasions where tracking tunnels detected them, and vice-versa. Overall, my results demonstrate that remote cameras are a more efficient multi-species monitoring tool than tracking tunnels. Independent of habitat type, cats (Felis catus), hedgehogs, and mice were the species most frequently recorded. Data from remote cameras subsequently helped quantify differences in the occupancy rates of species between residential and forested areas furthering our ecological understanding of the distribution of invasive species in peopled landscapes. To identify the underlying processes influencing the distribution and abundances of invasive mammals found in urban patches of vegetation, I also used remote cameras to investigate the influence of habitat quality, management efforts, interspecific interactions and seasonality on the occupancy and relative abundance of invasive mammals in 47 patches of forest within Wellington. My results indicate that distance to forest edge influences positively on the relative abundance of rodents and negatively on the relative abundance of common brushtail possums (Trichosurus vulpecula), cats, European rabbits (Oryctolagus cuniculus), and hedgehogs. The cameras also revealed a positive interaction between the occupancy of ship rats (Rattus rattus) and the abundance of Norway rats (Rattus norvegicus), a positive influence of the nearby buildings on the occupancy of cats, and how management control reduces the occupancy of target species, particularly during spring. These results illustrate the importance of using season- and species-specific approaches to identify the most important factors influencing the distribution of invasive species in urban environments. Overall, my research highlights the benefits of engaging the public with scientific research, the advantages of using remote cameras to monitor mammals in urban environments and the importance of controlling invasive species at adequate spatial and temporal scales to ensure effective conservation management.</p>

Understanding distributions of invasive mammals in urban environments using remote cameras and citizen science

<p>Preserving biodiversity in urban environments is crucial not only for preventing local extinctions of native species, but also for educating the public about the importance of species conservation. Invasive mammalian species can have negative impacts for both people and biodiversity in urban environments. Understanding the factors influencing the distribution of these invasive species is crucial to comply with the ethical, ecological, and practical concerns associated with their management. Remote cameras are an increasingly popular tool for investigating the distribution and abundance of mammals. Yet few studies have used these cameras in urban environments. The time and effort required to classify remote camera data is the main constraint of this monitoring technique. To determine whether employing citizen science could facilitate the use of remote cameras in urban environments, I investigated the engagement, accuracy, and efficiency of volunteers (i.e., citizen scientists) in classifying animal images recorded by remote cameras in Wellington, New Zealand. Classifications from citizen scientists were in 84.2% agreement with classifications of expert ecologists. However, accuracy varied significantly among species and volunteers. Aggregating multiple classifications per image and highlighting animal movement in the images improved the accuracy of citizen scientists. Additionally, weighting their classifications based on previous accuracy, self-assessed confidence, and the species reported reduced the number of volunteer classifications required to achieve levels of accuracy comparable to that of experts. These results illustrate that citizen science allows for accurate and efficient classifications of remote camera data from urban areas. Using the classifications provided by citizen scientists, I then evaluated the suitability of remote cameras to monitor invasive mammals in urban environments. Based on data collected from forest and residential areas of Wellington, New Zealand, remote cameras detected significantly more European hedgehogs (Erinaceus europaeus) and rats (Rattus spp.) than tracking tunnels. Cameras, however, missed recording house mice (Mus musculus) on some occasions where tracking tunnels detected them, and vice-versa. Overall, my results demonstrate that remote cameras are a more efficient multi-species monitoring tool than tracking tunnels. Independent of habitat type, cats (Felis catus), hedgehogs, and mice were the species most frequently recorded. Data from remote cameras subsequently helped quantify differences in the occupancy rates of species between residential and forested areas furthering our ecological understanding of the distribution of invasive species in peopled landscapes. To identify the underlying processes influencing the distribution and abundances of invasive mammals found in urban patches of vegetation, I also used remote cameras to investigate the influence of habitat quality, management efforts, interspecific interactions and seasonality on the occupancy and relative abundance of invasive mammals in 47 patches of forest within Wellington. My results indicate that distance to forest edge influences positively on the relative abundance of rodents and negatively on the relative abundance of common brushtail possums (Trichosurus vulpecula), cats, European rabbits (Oryctolagus cuniculus), and hedgehogs. The cameras also revealed a positive interaction between the occupancy of ship rats (Rattus rattus) and the abundance of Norway rats (Rattus norvegicus), a positive influence of the nearby buildings on the occupancy of cats, and how management control reduces the occupancy of target species, particularly during spring. These results illustrate the importance of using season- and species-specific approaches to identify the most important factors influencing the distribution of invasive species in urban environments. Overall, my research highlights the benefits of engaging the public with scientific research, the advantages of using remote cameras to monitor mammals in urban environments and the importance of controlling invasive species at adequate spatial and temporal scales to ensure effective conservation management.</p>

Understanding the distribution of introduced mammalian predators in an urban environment using monitoring tools and community trapping

<p>Introduced mammalian predators are one of the largest conservation threats to New Zealand native flora and fauna, and there is an increasing concern about their presence in urban environments, coupled with a recognition that cities present a unique opportunity for ecological restoration, due to the availability of a large number of volunteers and options for intensive management of green spaces and gardens. Predator control is an essential step towards the ecological restoration of urban environments, however, it requires an understanding of the factors influencing the distribution of these mammalian predators before successful control operations can be implemented. Few studies have investigated mammalian predators in urban environments, and there is little certainty about what drives their distribution in these environments. This thesis used simple mammal monitoring techniques and trapping data to investigate the distribution of mammalian predators within broad scale urban environments, with the aim of identifying drivers of their distribution. Chew cards and tracking tunnels collected across three New Zealand cities were assessed for their efficacy as accurate monitoring devices in urban environments. In Chapter 2, monitoring devices were cross-checked between observers to assess the level of consistency in interpretation of chew and tracking marks. The consistency of chew card and tracking tunnel identifications was relatively high overall and were not substantially influenced by the city of identification, or the duration of card exposures. Monitoring devices were also assessed for their change in sensitivity between one and six-night exposures. Both devices were effective at detecting rats, however, tracking tunnels showed greater sensitivity and consistency in detecting mice and hedgehogs, whereas chew cards were better suited to the monitoring of possums. Neither device was particularly effective at detecting mustelids or cats. In Chapter 3, mammalian predators were monitored across 24 monitoring lines in autumn, 2018, and results were compiled with spring 2017 and autumn 2018 data, pre-collected in two other cities, following the same procedures. There were distinct differences in the broad-scale habitat utilisation of rats, mice, hedgehogs, with possums being the only species to show a strong preference for urban forests. Only two of the tested microhabitat variables had an influence on species distributions. Detection of rats declined with increasing distance to the coast, and the increase in human population size was related to a significant increase in hedgehogs. There was a strong seasonal difference on the influence of local trap density and the detection of mammals. The increase in trap density within 25-50m radii was significantly related to a decrease in rat and hedgehog detections. Overall, there are substantial differences between the distributions of species in an urban environment. Trapping is one of the main methods of predator control in New Zealand, and is already widespread within urban and suburban Wellington. In Chapter 4, I compiled trap data from 22 community trapping groups operating in residential and reserve areas in Wellington City. Residential groups (“backyard trappers”) used a high proportion of Victor and various rat and mouse traps, which was strongly linked to their high number of rat and mouse catches. Groups trapping in reserves used a high proportion of DOC 200, Victor and A24 traps, however, fewer hedgehogs were caught compared to residential areas. Catches were significantly influenced by various landscape variables. An increased distance of traps to streams led to significantly higher catches of rats, conversely, proximity to streams resulted in significantly higher catches of mice and hedgehogs. Although few catches of weasels were reported, traps closer to the coast and to forest fragments caught significantly more individuals. The research in this thesis contributes to the small body of research conducted on mammalian predators within urban environments. The findings in this thesis can assist with the current and future predator management programmes, by highlighting areas of potential significance, particularly in Wellington.</p>

Assessing the Attractiveness of Three Baits for Roof Rats in California Citrus Orchards

Roof rats (Rattus rattus) are common pests of tree fruit and nut orchards in California. Tracking tunnels are an effective and practical tool for monitoring changes in roof rat numbers in orchard systems, but they rely on the use of attractive baits to draw in rats to the tracking surface. The identification of baits that are both attractive and readily available would be of great assistance for monitoring changes in roof rat numbers within agricultural fields. Therefore, we tested the attractiveness of a soft bait (Liphatech Rat and Mouse AttractantTM), a wax block (Liphatech NoToxTM), peanut butter, and a control (i.e., no bait applied) to roof rats when applied within tracking tunnels. We did not observe a difference in visitation to any of the tested attractants, although all attractants yielded greater visitation rates than control tunnels. However, tracking tunnels without any attractant were still visited at a relatively high rate, indicating the tracking tunnel is attractive to roof rats. As such, monitoring tools that provide shelter may increase detectability, although this would need to be verified. Regardless, all three food-based lures we tested increased the attractiveness of tracking tunnels and could be used to increase visitation to these monitoring devices.

Evaluation of remote cameras for monitoring multiple invasive mammals in New Zealand

© New Zealand Ecological Society. Numerous conservation projects in New Zealand aim to reduce populations of invasive mammalian predators to facilitate the recovery of native species. However, results of control efforts are often uncertain due to insufficient monitoring. Remote cameras have the potential to monitor multiple species of invasive mammals. To determine the efficiency of cameras as a multi-species monitoring tool, we compared the detection rates of remote cameras and tracking tunnels over 4 non-consecutive days across 40 sites in Wellington. On average, cameras detected significantly more hedgehogs (Erinaceus europaeus) and rats (Rattus spp.) than tracking tunnels, and their images could be used to identify rats to the species level in 50% of detections. Cameras also detected more possums (Trichosurus vulpecula) but missed recording mice (Mus musculus) on some occasions where tracking tunnels detected them, and vice-versa. We conclude that remote cameras are well-suited for simultaneously monitoring multiple species of invasive mammals in New Zealand.

Evaluation of remote cameras for monitoring multiple invasive mammals in New Zealand

© New Zealand Ecological Society. Numerous conservation projects in New Zealand aim to reduce populations of invasive mammalian predators to facilitate the recovery of native species. However, results of control efforts are often uncertain due to insufficient monitoring. Remote cameras have the potential to monitor multiple species of invasive mammals. To determine the efficiency of cameras as a multi-species monitoring tool, we compared the detection rates of remote cameras and tracking tunnels over 4 non-consecutive days across 40 sites in Wellington. On average, cameras detected significantly more hedgehogs (Erinaceus europaeus) and rats (Rattus spp.) than tracking tunnels, and their images could be used to identify rats to the species level in 50% of detections. Cameras also detected more possums (Trichosurus vulpecula) but missed recording mice (Mus musculus) on some occasions where tracking tunnels detected them, and vice-versa. We conclude that remote cameras are well-suited for simultaneously monitoring multiple species of invasive mammals in New Zealand.