Stephen Hartley - Profile on Academia.edu (original) (raw)

Papers by Stephen Hartley

After eight years, mānuka (LS) and cabbage trees (CA) had the highest survival rates (52-56%), th... more After eight years, mānuka (LS) and cabbage trees (CA) had the highest survival rates (52-56%), the podocarps, kahikatea (DD) and tōtara (PT), had survival rates of 41-48%. Cabbage trees grew tallest, Pittosporum tenuifolium (KO) and Olearia virgata (OV) sequestered the most carbon over the eight years (7.4 and 5.1 kg per tree, respectively) and kahikatea and tōtara the least (0.1 to 0.8 kg per tree).

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Biology

A barrier to successful ecological restoration of urban green spaces in many cities is invasive m... more A barrier to successful ecological restoration of urban green spaces in many cities is invasive mammalian predators. We determined the fine- and landscape-scale habitat characteristics associated with the presence of five urban predators (black and brown rats, European hedgehogs, house mice, and brushtail possums) in three New Zealand cities, in spring and autumn, in three green space types: forest fragments, amenity parks, and residential gardens. Season contributed to variations in detections for all five taxa. Rodents were detected least in residential gardens; mice were detected more often in amenity parks. Hedgehogs were detected least in forest fragments. Possums were detected most often in forest fragments and least often in residential gardens. Some of this variation was explained by our models. Proximity of amenity parks to forest patches was strongly associated with presence of possums (positively), hedgehogs (positively), and rats (negatively). Conversely, proximity of re...

Better food-based baits and lures for invasive rats Rattus spp. and the brushtail possum Trichosurus vulpecula: a bioassay on wild, free-ranging animals

Journal of Pest Science, 2015

Food-based baits and lures remain the mainstay of eradication and monitoring methodologies for in... more Food-based baits and lures remain the mainstay of eradication and monitoring methodologies for invasive mammalian species. To date, however, best-practise baits and lures for rats and possums have not been systematically compared to alternative food-based products in ways that quantify their effectiveness on free-ranging, wild animals. We designed a rapid bioassay using chew-cards to present large numbers of food-based products to free-ranging rats and possums to assess their attractiveness and consumption compared to current standards. We used linear mixed-effects regression analysis and an information-theoretic model set to consider the nutritive drivers of consumption for each species with the aim of informing the design of, and future search for, baits. Current standards were statistically outperformed in our trials. For rats, cheese, milk chocolate, Nutella® and walnut were statistically more attractive than the peanut butter standard. For possums, apricot and almond were statistically more attractive that the cinnamon standard. Model comparisons indicate that energy, particularly from fats, is the most important determinant of consumption by rats, while protein is the most important determinant of consumption by possums. Our results demonstrate that current standard lures for both species could be more attractive whilst the inclusion of fat to rat baits and protein to possum baits could increase bait consumption and improve control operation outcomes. Further, our bioassay provides practitioners a cost effective and rapid methodology to systematically assess large numbers of food products on free-ranging, wild animals thus providing more realistic results than those obtained under pen or laboratory conditions.

1. The aggregation model of coexistence has been used widely to explain the coexist-ence of compe... more 1. The aggregation model of coexistence has been used widely to explain the coexist-ence of competing species that utilize patchy and ephemeral resources. Over the years, it has been reformulated in many different ways, using different assumptions, indices and analyses, leading sometimes to contradictory conclusions. We present a general framework, from which many of the alternative approaches are derived as special cases. 2. A generalized distribution, composed of the distribution of visits across patches and the distribution of eggs per visit, is used to model changes in the mean individual-level experience of density that occur at different population-level densities. 3. New and more general criteria for coexistence are derived, based upon standard invasability analysis of Lotka–Volterra competition equations applied to a patchy system. 4. An important parameter in the new coexistence criteria is the mean per capita den-sity of individuals in a single clutch ( §). Until now this ...

business.otago.ac.nz

This Masters project intends to explore by computer simulation the effects of individual foraging... more This Masters project intends to explore by computer simulation the effects of individual foraging behaviour and resource aggregation on foraging patterns at multiple scales. An object-oriented approach will be taken to provide a flexible framework within which different simulation methods may be applied and compared. Examples of previously published methods include observational (Jones 1977) and correlated random walk (Cain 1985) simulations. These methods will be extended to include more biologically realistic interactions with the environment such as olfactory and visual cues to examine the effects on the accuracy of predictions. The results will be in terms of visits to resources (either nectar-feeding or oviposition). Whilst some simulations will be generic, others will be parameterised for specific species such as the cabbage white butterfly, Pieris rapae (which already commands a wealth of previous research and observation). Taking individual level models as a starting point, the intention is to extend the scope to investigate population and community level effects by creating multi-generation and multi-species (e.g. predator / parasatoid) simulations. To complement the simulations, field observations will be made (as part of a separate project), recording flight paths and egg distributions for New Zealand populations of Pieris rapae. With regards to hypotheses, a key question is "Do isolated plants receive fewer visits than those which are aggregated?" Current literature tends to explore this question at various scales separately. This project aims to specifically examine the relationship between multiple scales of observation (what appears isolated at one scale may be aggregated at a larger scale) and the scale of movement of the observed species (dispersal ability). A further question is "Can different resource usage patterns be observed for the same species at different scales?" As "isolation" depends on the scale of observation, a more directed question would be "Can resources which are isolated at one scale receive a greater number of visits but at a larger scale receive fewer visits?" The flexibility of a simulation environment allows a much wider parameter space to be explored than experimentally and it is hoped that results from the simulations can help to direct and stimulate subsequent field experiments.

New Zealand journal of ecology, 2021

Modern aerial 1080 (sodium monofluoroacetate) operations are effective in reducing population den... more Modern aerial 1080 (sodium monofluoroacetate) operations are effective in reducing population densities of possums, rats and stoats, thereby reducing predation pressure on birds. Debate regarding 1080 use, however, continues to centre on potential non-target effects, with some groups claiming that birds are killed in large numbers such that forests "fall silent". We investigated these claims by recording birdsong for 5-8 weeks before and after three separate 1080 operations in the Aorangi and Remutaka Ranges of the lower North Island, New Zealand. A Before-After/Control-Impact (BACI) design was employed for each operation, with simultaneous monitoring carried out in treated and untreated sites using autonomous recording units. The amount of birdsong was quantified, scoring the presence/absence of species' calls in 30 ten second sub-samples for each of the 695 recordings analysed. The interaction between treatment and time and the "BACI contrast" was tested for at the community-and population-level. After each operation, the amount of silence was the same or lower in sites treated with 1080 relative to paired non-treated sites. Six taxa showed no evidence of an effect of 1080, while two of 26 taxa/treatment tests showed a significant interaction between treatment and time consistent with the silent forest hypothesis: chaffinch and tomtit calling rates declined following the Aorangi 2017 and Aorangi 2014 operations respectively. At p < 0.05, one or two "significant" results in 26 may be expected by chance. A negative impact on the introduced chaffinch (observed in one of three operations) is plausible considering the species' granivorous diet. The pathway for a negative impact on insectivorous tomtits is less obvious; as a precautionary approach we recommend further research. Overall, we found little evidence of forests falling silent after aerial 1080 operations and the likelihood of negative population-level impacts via poisoning of native birds was concluded to be very low.

Hebeloma spp.) on organic and inorganic nitrogen

Developmental degree-day models to assess the establishment potential of three exotic turtle species in New Zealand

Effects of mammal exclusion on invertebrate communities in New Zealand

Austral Ecology

Diversity

In this paper, we focus on different roles in citizen science projects, and their respective rela... more In this paper, we focus on different roles in citizen science projects, and their respective relationships. We propose a tripartite model that recognises not only citizens and scientists, but also an important third role, which we call the ‘enabler’. In doing so, we acknowledge that additional expertise and skillsets are often present in citizen science projects, but are frequently overlooked in associated literature. We interrogate this model by applying it to three case studies and explore how the success and sustainability of a citizen science project requires all roles to be acknowledged and interacting appropriately. In this era of ‘wicked problems’, the nature of science and science communication has become more complex. In order to address critical emerging issues, a greater number of stakeholders are engaging in multi-party partnerships and research is becoming increasingly interdisciplinary. Within this context, explicitly acknowledging the role and motivations of everyone ...

Disentangling the factors that vary the impact of trees on flooding (a review)

Water and Environment Journal

Reviewing the past, present and potential lizard faunas of New Zealand cities

Landscape and Urban Planning

Abstract Cities and urban processes typically have a negative impact on biodiversity via land cov... more Abstract Cities and urban processes typically have a negative impact on biodiversity via land cover change, high rates of disturbance and high densities of pest species. Increasingly, however, people are being encouraged and empowered to reduce these impacts through urban restoration and backyard conservation initiatives. Internationally, lizards are a common feature of urban biodiversity, but in New Zealand where many species are threatened, little is known about populations of native skinks and geckos in cities. Yet cities may offer unique opportunities for lizard conservation compared with alternatively modified habitats. To explore the potential of cities for the conservation of lizards, we collated knowledge about the current lizard faunas of six New Zealand cities and developed a list of species that would likely have been present in the locations of these cities prior to human settlement. Comparing the two, we found that, although each of the cities has at least one currently urban-dwelling species, the diversity of lizards in all of the cities has declined dramatically since human colonisation. Patterns of species loss in cities reflect those observed across New Zealand more generally; that is, the loss of large-bodied skinks and geckos, probably resulting from predation by introduced mammalian predators, as well as the loss of regionally endemic species. The high diversity of species that are currently, or were historically, present in the locations of New Zealand cities means that urban restoration involving recovery or reintroduction of populations could have significant benefits for lizard conservation and advocacy.

Conservation Biology

Over the past 1000 years New Zealand has lost 40-50% of its bird species, and over half of these ... more Over the past 1000 years New Zealand has lost 40-50% of its bird species, and over half of these extinctions are attributable to predation by introduced mammals. Populations of many extant forest bird species continue to be depredated by mammals, especially rats, possums, and mustelids. The management history of New Zealand's forests over the past 50 years presents a unique opportunity because a varied program of mammalian predator control has created a replicated management experiment. We conducted a meta-analysis of population-level responses of forest birds to different levels of mammal control recorded across New Zealand. We collected data from 32 uniquely treated sites and 20 extant bird species representing a total of 247 population responses to 3 intensities of invasive mammal control (zero, low, and high). The treatments varied from eradication of invasive mammals via ground-based techniques to periodic suppression of mammals via aerially sown toxin. We modeled population-level responses of birds according to key life history attributes to determine the biological processes that influence species' responses to management. Large endemic species, such as the Kaka (Nestor meridionalis) and New Zealand Pigeon (Hemiphaga novaeseelandiae), responded positively at the population level to mammal control in 61 of 77 cases for species ࣙ20 g compared with 31 positive responses from 78 cases for species <20 g. The Fantail (Rhipidura fuliginosa) and Grey Warbler (Gerygone igata), both shallow endemic species, and 4 nonendemic species (Blackbird [Turdus merula], Chaffinch [Fringilla coelebs], Dunnock [Prunella modularis], and Silvereye [Zosterops lateralis]) that arrived in New Zealand in the last 200 years tended to have slight negative or neutral responses to mammal control (59 of 77 cases). Our results suggest that large, deeply endemic forest birds, especially cavity nesters, are most at risk of further decline in the absence of mammal control and, conversely suggest that 6 species apparently tolerate the presence of invasive mammals and may be sensitive to competition from larger endemic birds.

The effects of squid-baiting pitfall traps for sampling wētā (Orthoptera) and other ground-dwelling forest invertebrates

New Zealand Entomologist

© 2020 Entomological Society of New Zealand. Pitfall traps are commonly used to sample surface-ac... more © 2020 Entomological Society of New Zealand. Pitfall traps are commonly used to sample surface-active invertebrates, although the efficiency of the technique varies among taxa. We investigated how baiting pitfall traps with squid influenced sampling of some ground-dwelling invertebrates in New Zealand forests. The study was conducted across a total of 21 sets of seven lethal pitfall traps established between November 2012 and November 2015 in Aorangi and Remutaka forests. Four non-baited and three squid-baited lethal pitfall traps were established per set and remained active for one night during November/December and three nights during February. Squid-baited pitfall traps caught four times as many ground wētā and three times more cave wētā per unit effort than unbaited traps. Most of the ground wētā were identified as Hemiandrus pallitarsis (Walker, 1869). Carabidae, Scarabaeidae, Staphylinidae, Opiliones, Hymenoptera and Araneae were also more abundant in squid-baited than in unbaited traps. There was little difference in the catches of peripheral pitfall traps versus central pitfall traps, suggesting that 5 m spacing is sufficient to generate independent samples. Exceptions were Araneae and Amphipoda which were both approximately 1.5 times more abundant in central compared to peripheral unbaited traps. The attraction of ground and cave wētā to squid provides some insight into their dietary range. The higher catches obtained with squid-baiting, suggests this may be a useful modification to increase sampling rates, which is valuable where sampling effort is logistically constrained such as on islands or other remote study sites.

Geostatistical interpolation can reliably extend coverage of a very high-resolution model of temperature-dependent sex determination

Journal of Biogeography

Frontiers of Biogeography

The urgency of predicting future impacts of environmental change on vulnerable populations is adv... more The urgency of predicting future impacts of environmental change on vulnerable populations is advancing the development of spatially explicit habitat models. Continental-scale climate and microclimate layers are now widely available. However, most terrestrial organisms exist within microclimate spaces that are very small, relative to the spatial resolution of those layers. We examined the effects of multi-resolution, multi-extent topographic and climate inputs on the accuracy of hourly soil temperature predictions for a small island, generated at a very high spatial resolution (<1 m 2 ) using the mechanistic microclimate model in NicheMapR. Achieving an accuracy comparable to lower-resolution, continentalscale microclimate layers (within about 2-3°C of observed values) required the use of daily weather data as well as high resolution topographic layers (elevation, slope, aspect, horizon angles), while inclusion of site-specific soil properties did not markedly improve predictions. Our results suggest that large-extent microclimate layers may not provide accurate estimates of microclimate conditions when the spatial extent of a habitat or other area of interest is similar to or smaller than the spatial resolution of the layers themselves. Thus, effort in sourcing model inputs should be focused on obtaining high resolution terrain data, e.g., via LiDAR or photogrammetry, and local weather information rather than in situ sampling of microclimate characteristics.

Activity of free-roaming domestic cats in an urban reserve and public perception of pet-related threats to wildlife in New Zealand

Urban Ecosystems

Journal of Urban Ecology

Remotely activated cameras are increasingly used worldwide to investigate the distribution, abund... more Remotely activated cameras are increasingly used worldwide to investigate the distribution, abundance and behaviour of animals. The number of studies using remote cameras in urban ecosystems, however, is low compared to use in other ecosystems. Currently, the time and effort required to classify images is the main constraint of this monitoring technique. To determine whether, or not, citizen science might help overcome this constraint, we investigated the engagement, accuracy and efficiency of citizen scientists providing crowd-sourced classifications of animal images recorded by remote cameras in Wellington, New Zealand. Classifications from individual citizen scientists were in 84.2% agreement with the classifications of professional ecologists. Aggregating the classifications from three citizen scientists per image, and excluding false triggers and unclassifiable classifications increased their overall accuracy to 97.6%. Classifications by citizen scientists also improved if animal movement was highlighted in the images. The likelihood of citizen scientists correctly classifying images was influenced by their previous accuracy, their self-assessed confidence, and the species reported. Weighting the citizen scientist classifications based on their ability to correctly identify animals reduced from 3 to 2 the number of classifications required per sequence to classify >95% of the photographs containing cats. Citizen science is an accurate and efficient approach for classifying remote camera data from urban areas, where most of the animals are familiar to the participants. We demonstrated how appropriate tools and accounting for the accuracy of citizen scientists, allows project managers to maximise the effort of citizen scientists while ensuring high-quality data.

Avian Conservation and Ecology

Automated sound recording devices have become an important monitoring tool used to estimate speci... more Automated sound recording devices have become an important monitoring tool used to estimate species richness and abundance of birds in a variety of ecological and conservation studies. The prevalence of calls detected in a specific time period can be used as an index of relative abundance, to compare between populations. However, the statistical power to infer true differences in abundance between populations is low when detections are highly aggregated in time leading to high variance between samples from the same population. Here, we used two different sampling methods, and used the data from each to calculate species richness and acoustic prevalence of nine bird taxa from a total of 50 sound recordings. The first method simulated typical monitoring techniques used by observers in the field by using a continuous five-minute section of the recording. The second method used the first 10 seconds of each minute to create a composite recording, also of five minutes total duration. There was no difference in the mean prevalence index between methods. The intermittent samples, however, produced prevalence indices with a lower standard deviation (mean difference = 19 %), detected 26% more species per five-minute sample and required 60% less total listening time to detect as many species as the continuous method. The only cost of subsampling from a long recording is the extra digital memory and battery life required to obtain the recordings in the first place. Given that these costs are minor, the intermittent method holds much promise because it detects species more efficiently and provides greater power to detect differences in a species' relative abundance, which in turn should allow for better-informed management regarding population status and trends.

New Zealand Journal of Ecology

Numerous conservation projects in New Zealand aim to reduce populations of invasive mammalian pre... more 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.

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