Improving matrix quality may be a powerful strategy for conserving biodiversity in fragmented landscapes, but effectively implementing this strategy requires a better understanding of how much of the matrix needs to be converted to ‘high‐quality’ land uses to achieve conservation goals. Here, we use data on the distribution of forest birds across > 1000 landscapes throughout New Zealand to quantify how the impacts of habitat loss (declining native forest cover) change as the proportion of matrix that is a high‐quality land use (exotic plantation forest) increases. As expected, we found that the amount of plantation forest in the matrix strongly influenced the extent to which native forest loss impacted bird communities: a decline in native forest cover from 90 to 1% caused a 60% decrease in bird species richness when there was no plantation forest in the matrix, but only a 15% decrease when 99% of the matrix was plantation forest. However, this plantation forest effect was strongly nonlinear, with most of the benefits of increasing plantation forest cover occurring before plantations reached even 10% of the matrix. Conversely, increasing plantation forest cover had minimal effects when the matrix was already dominated by plantation forest, or when native forest cover was high. Previous research has confirmed that matrix quality can strongly influence the biodiversity of fragmented landscapes, but results from our study system suggest that managing the matrix to benefit biodiversity could be surprisingly straightforward. Most of these benefits may be achieved by maintaining a small proportion of the matrix as high‐quality land uses.

Effective biodiversity conservation in lowland New Zealand requires an understanding of the relative benefits of managing impacts of native forest loss versus controlling invasive species. We used bird count data from 195 locations across mainland northern New Zealand to examine how the abundance and richness of native forest birds varied across wide gradients of native forest cover (c. 0-100%) and intensity of invasive species control (`eradication', 'high-intensity rat and possum', 'low-intensity rat and possum', 'periodic possum' and `none'). Most response variables were significantly affected by forest cover, and this effect was typically non-linear: response variables declined rapidly below c. 5-10% forest cover, but were relatively invariant to forest cover above this point. Pest control was found to affect surprisingly few species, with only kereru (Herniphaganovaeseelandiae) and tui (Prosthemadera novaeseel andiae) being more abundant at pest controlled than uncontrolled sites for any pest control category. Species richness and 'total abundance' (abundance of all species combined) also increased at pest controlled sites, but effects were largely driven by responses 'of tui and kereru. Effects of eradication were far larger than effects of other pest control categories, while it was unclear whether 'low-intensity rat and possum' or 'periodic possum' control had any effects at all. Our results suggest that both managing levels of forest cover and controlling invasive mammals can benefit native forest birds, but the occurrence and magnitude of these benefits will be context-dependent. Managing forest cover may be relatively unimportant in landscapes with >5-10% forest cover, while benefits of pest control may be limited unless intensive methods are used. Moreover, even intensive pest control may only benefit a small subset of species unless coupled with reintroduction of locally-extinct species. Combining these results with knowledge of the financial, ethical, and social constraints of different management options should provide a solid foundation for effective conservation decision-making in lowland environments.

Predicting and managing edge effects requires an understanding of the mechanisms that drive them. However, analytical methods that dominate edge effects research are not well suited to discriminating mechanisms, because they do not measure ‘indirect’ edge effects: effects that are mediated by covariates in statistical models.

Collinearity among metrics of habitat loss and habitat fragmentation is typically treated as a nuisance in landscape ecology, and it is the norm to use statistical approaches that remove collinear information prior to estimating model parameters. However, collinearity may arise from causal relationships among landscape metrics and may therefore signal the occurrence of indirect effects (where one model predictor influences the response variable by driving changes in another influential predictor). Here we suggest that, far from being merely a statistical nuisance, collinearity may be crucial for accurately quantifying the effects of habitat loss versus habitat fragmentation. We use simulation modelling to create datasets of collinear landscape metrics in which collinearity arose from causal relationships, then test the ability of two statistical approaches to estimate the effects of these metrics on a simulated response variable: 1) multiple regression, which statistically removes collinearity, and was identified in a recent study as the best approach for estimating the effects of collinear landscape metrics (although this study did not account for any indirect effects implied by collinearity among metrics); and 2) path analysis, which accounts for the causal basis of collinearity. In agreement with this previous study, we found that multiple regression gave unbiased estimates of direct effects (effects not mediated by other model predictors). However, it gave biased estimates of total (direct. indirect) effects when indirect effects occurred. In contrast, path analysis reliably identified the causal basis of collinearity and gave unbiased estimates of direct, indirect, and total effects. We suggest that effective research on the impacts of habitat loss versus fragmentation will often require tools that can empirically test whether collinear landscape metrics are causally related, and if so, account for the indirect effects that these causal relationships imply. Path analysis, but not multiple regression, provides such a tool.

Improving decision-making about where and how invasive species management is conducted requires a better understanding of spatial variation in pest abundance and the extent to which different pest control regimes reduce those abundances. We measured how the relative abundance of invasive rats and possums, indexed at 147 forest sites in northern New Zealand, varied in response to environmental variables, and to the category of pest control at the site: no control (NC), periodic possum (PP), low-intensity rat and possum (LRP), and high-intensity rat and possum (HRP). We found that climate and topography strongly influenced the rat index, while vegetation characteristics strongly influenced both indices. These variables may therefore be useful for predicting pest impacts and prioritising locations for pest control. HRP control substantially reduced pest abundance indices, with model-predicted values for the rat index that were 99% lower than in areas of no control, and 91% lower for the possum index. In contrast, indices did not differ significantly among NC, PP, and LRP. PP and LRP regimes dominate pest control in New Zealand, but may be of limited conservation value, at least in terms of the 'average' operation in our study region. Globally, conservation agencies with limited budgets frequently avoid monitoring pest populations, since resources spent on monitoring are no longer available for management. However, our results highlight the value of collecting and analysing pest monitoring data, both for informing the location of future management and for ensuring that scarce resources are not wasted on ineffective control.

A successful translocation involves many complex factors, including a genetically appropriate source population that can sustain harvest, social and governmental support, assessment of disease transmission risk and a release site with appropriately secure habitat that can support population establishment and persistence. This information is typically discussed during statutory approval processes and can take considerable time. However, following approval, for translocations of most fauna, the initial critical step involves the inherently stressful process of capture, holding, transportation and release. This process is unpredictable and novel, and is especially challenging for wild animals when they are confined in close proximity to conspecifics and humans. In contrast, captive-reared animals have to cope with the unfamiliar challenges of finding food and shelter, along with coping with competition and predation. Little has been written in the scientific literature about the translocation process. This is unsurprising because this process has usually been the realm of skilled practitioners, often with animal husbandry backgrounds, rather than research scientists. Highly skilled intuition, observation and the translocation practitioner's equivalent of a 'green thumb' often guides the way. However, theory and experimentation, particularly on the effects of stress, is available and this work is invaluable for a successful translocation. Here, we provide a brief description of the translocation process, and discussion of what stress is and how it can be managed. We then provide practical guidelines for the successful translocation of invertebrates, lizards, turtles, passerine birds, marsupials and bats, using examples from Australia and New Zealand.

Chew-track-cards (CTCs) are potentially a cost-effective way to estimate the relative abundance of invasive rats and possums in New Zealand, but previous research suggested that their high sensitivity may limit use to low-density populations. Using a short two-night deployment period, we compared CTC indices of rat and possum abundance with a footprint tracking rate (RTR) index of rat abundance and a wax tag bite rate index (WTI) of possum abundance in 11 forest remnants that varied widely in rat and possum abundance (RTR and WTI of 0-100% over two nights). The CTC indices were strongly correlated with the WTI and RTR and were no more sensitive than these measures, and they showed little indication of saturation at high pest abundances. We found no evidence that rat interference altered possum bite rates, as had been observed for longer deployment periods. CTCs, deployed for two nights, are a promising tool for use over a wide range of pest abundances. Further research is required to examine whether rat interference is ever sufficiently high to obscure possum sign, and to confirm that the index can reflect meaningful variation in population density .

Forest edges can strongly affect avian nest success by altering nest predation rates, but this relationship is inconsistent and context dependent. There is a need for researchers to improve the predictability of edge effects on nest predation rates by examining the mechanisms driving their occurrence and variability. In this study, we examined how the capture rates of ship rats, an invasive nest predator responsible for avian declines globally, varied with distance from the forest edge within forest fragments in a pastoral landscape in New Zealand. We hypothesised that forest edges would affect capture rates by altering vegetation structure within fragments, and that the strength of edge effects would depend on whether fragments were grazed by livestock. We measured vegetation structure and rat capture rates at 488 locations ranging from 0-212 m from the forest edge in 15 forest fragments, seven of which were grazed. Contrary to the vast majority of previous studies of edge effects on nest predation, ship rat capture rates increased with increasing distance from the forest edge. For grazed fragments, capture rates were estimated to be 78% lower at the forest edge than 118 m into the forest interior (the farthest distance for grazed fragments). This relationship was similar for ungrazed fragments, with capture rates estimated to be 51% lower at the forest edge than 118 m into the forest interior. A subsequent path analysis suggested that these 'reverse' edge effects were largely or entirely mediated by changes in vegetation structure, implying that edge effects on ship rats can be predicted from the response of vegetation structure to forest edges. We suggest the occurrence, strength, and direction of edge effects on nest predation rates may depend on edge-driven changes in local habitat when the dominant predator is primarily restricted to forest patches.

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 8:33-39 (2009) - DOI: https://doi.org/10.3354/esr00181 Assessment of the short-term success of a translocation of lesser short-tailed bats Mystacina tuberculata Jay Ruffell, Stuart Parsons* School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand *Corresponding author. Email: s.parsons@auckland.ac.nz ABSTRACT: Translocation is a powerful tool that has been used in the conservation of a wide range of taxa. However, few translocations of bats have been attempted and we know of no successes. The few translocations which have been attempted have either failed due to dispersal from the release site or have not been monitored sufficiently to determine the cause of failure. We assessed the short-term success of a translocation of lesser short-tailed bats Mystacina tuberculata by the New Zealand Department of Conservation, where 3 release methods were used to minimise dispersal or mortality: bats were juveniles, were maintained in captivity at the release site, and were provided with supplementary food and roosts following release. Success was assessed by determining if founders remained at the release site and maintained condition (weight). Recapture showed that at least 9 of the 20 bats remained at the release site 232 d after release. There was weak evidence that bats lost weight, although final weights were comparable to those of bats from a natural population. However, all bats captured 8 mo after release had damaged, infected ears and some were balding. The problem was treated but recurred, and bats were returned to captivity. Our results are the first to demonstrate that translocated bats can remain at their release site and survive. However, disease may be an issue in future translocations. KEY WORDS: Lesser short-tailed bat · Mystacina tuberculata · New Zealand · Translocation · Relocation · Reintroduction · Soft release · Supplementary food · Disease Full text in pdf format PreviousNextCite this article as: Ruffell J, Parsons S (2009) Assessment of the short-term success of a translocation of lesser short-tailed bats Mystacina tuberculata. Endang Species Res 8:33-39. https://doi.org/10.3354/esr00181 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 8, No. 1-2. Online publication date: July 09, 2009 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2009 Inter-Research.

Translocation is an increasingly popular conservation tool from which a wide range of taxa have benefited. However, to our knowledge, bats have not been translocated successfully. Bats differ behaviourally, morphologically and physiologically from the taxa for which translocation the- ory has been developed, so existing guidelines may not be directly transferable. We review previous translocations of bats and discuss characteristics of bats that may require special consideration dur- ing translocation. Their vagility and homing ability, coloniality, roost requirements, potential ability to transmit diseases, susceptibility to anthropomorphic impacts, and cryptic nature have implications for establishing populations, effects of these populations on the release site, and ability to monitor translocation success following release. We hope that our discussion of potential problems will be able to supplement the existing, more generic guidelines to provide a starting point for the planning of bat translocations.

Abstract Lesser short‐tailed bats (Mystacina tuberculata) have recently been translocated to Kapiti Island in an attempt to form a new population of this threatened species. However, the island's vegetation is regenerating, and there was doubt that the forests provided enough large trees with cavities for bats to roost in. This study measured the availability of tree‐trunk cavities of the right size for potential roost sites on Kapiti Island, and assessed if habitat restoration would be required to increase the translocation's chance of success. first, trees with cavities accessible to us were sampled in six of Kapiti Island's forest types. Size variables known to affect roost site selection by lesser short‐tailed bats at the tree and cavity level were measured. Trees were classified as containing cavities that could potentially provide suitable roosts if their values for all variables measured fell within the range of roosts used by lesser short‐tailed bats in natural populations. Roosts were classified as suitably sized for solitary bats or for colonies, using measurements from both types of roosts in natural populations. Second, the density of these potential roost cavities was calculated. Cavities of a size potentially suitable for colonies were found in four of the six forest types at densities ranging from 3.2 ± 3.2 Se to 52.4 ± 14.0 trees per ha. density of potential solitary roosts was much higher. Not all potential cavities will be suitable because they may be damp, poorly insulated, or have an unsuitable microclimate. Nevertheless, our estimates indicated that the two most extensive forest types each contained thousands of potential cavities of a size suitable for colonies of lesser short‐tailed bats. In addition, there were tens of thousands of cavities large enough to shelter solitary bats. Roost habitat restoration appears unnecessary to assist translocated Mystacina tuberculata on Kapiti Island.