We tested the unsustainable fishing hypothesis that species in assemblages of fish differ in relative abundance as a function of their size, growth rates, vagility, trophic level, and diet by comparing species composition in historical bone middens, modern fisheries, and areas closed to fishing. Historical data came from one of the earliest and most enduring Swahili coastal settlements (approximately AD 750-1400). Modern data came from fisheries near the archeological site and intensively harvested fishing grounds in southern Kenya. The areas we sampled that were closed to fishing (closures) were small (<28 km(2) ) and permanent. The midden data indicated changes in the fish assemblage that are consistent with a weak expansion of fishing intensity and the unsustainable fishing hypothesis. Fishes represented in the early midden assemblages from AD 750 to 950 had longer life spans, older age at maturity, and longer generation times than fish assemblages after AD 950, when the abundance of species with longer maximum body lengths increased. Changes in fish life histories during the historical period were, however, one-third smaller than differences between the historical and modern assemblages. Fishes in the modern assemblage had smaller mean body sizes, higher growth and mortality rates, a higher proportion of microinvertivores, omnivores, and herbivores, and higher rates of food consumption, whereas the historical assemblage had a greater proportion of piscivores and macroinvertivores. Differences in fish life histories between modern closures and modern fishing grounds were also small, but the life histories of fishes in modern closures were more similar to those in the midden before AD 950 because they had longer life spans, older age at maturity, and a higher proportion of piscivores and macroinvertivores than the modern fisheries. Modern closures and historical fish assemblages were considerably different, although both contained species with longer life spans.
Metacommunity theory allows predictions about the dynamics of potentially interacting species' assemblages that are linked by dispersal, but strong empirical tests of the theory are rare. We analyzed the metacommunity dynamics of Florida rosemary scrub, a patchily distributed pyrogenic community, to test predictions about turnover rates, community nestedness, and responses to patch size, arrangement, and quality. We collected occurrence data for 45 plant species from 88 rosemary scrub patches in 1989 and 2005 and used growth form, mechanism of regeneration after fire, and degree of habitat specialization to categorize species by life history. We tested whether patch size, fire history, and structural connectivity (a measure of proximity and size of surrounding patches) could be used to predict apparent extinctions and colonizations. In addition, we tested the accuracy of incidence-function models built with the patch survey data from 1989. After fire local extinction rates were higher for herbs than woody plants, higher for species that regenerated only from seed than species able to resprout, and higher for generalist than specialist species. Fewer rosemary specialists and a higher proportion of habitat generalists were extirpated on recently burned patches than on patches not burned between 1989 and 2005. Nestedness was highest for specialists among all life-history groups. Estimated model parameters from 1989 predicted the observed (1989-2005) extinction rates and the number of patches with persistent populations of individual species. These results indicate that species with different life-history strategies within the same metacommunity can have substantially different responses to patch configuration and quality. Real metacommunities may not conform to certain assumptions of simple models, but incidence-function models that consider only patch size, configuration, and quality can have significant predictive accuracy.
I compared understory bird community structure and composition among primary, slightly disturbed, and moderately disturbed forest in the East Usambara Mountains in Tanzania. Comparisons were conducted at two spatiotemporal scales: short term, conducted in 1999 and 2000, in which treatments (disturbance levels) were replicated, and long term, conducted from 1989–2004 along the same disturbance gradient of a subset of the short-term sites. I used capture-recapture models to assess the probability of detection and estimate species richness and population growth rates. The probability of detection of species did not vary significantly among disturbance levels but did vary significantly among species. Over the short- and long-term surveys, estimated species richness did not vary significantly among disturbance levels. Temporal variability in estimated species richness and the relative abundance of guilds did vary significantly among disturbance levels yet was contingent on survey length. The coefficient of variation in species richness over the short-term survey was <5% across all disturbance levels, whereas over the long-term survey it was 35% in slightly disturbed forest, 11% in moderately disturbed forest, and 0% in primary forest. In the short-term survey, zero of seven feeding guilds varied significantly in relative abundance among disturbance levels, whereas over the long-term survey four of seven (57%) feeding guilds did so. Terrestrial insectivores were most adversely affected by forest disturbance. Population growth rates (λ) between 1989 and 2004 for the more common species of terrestrial insectivores did not vary significantly among disturbance levels and for these species were significantly ≤1.00, indicating the recovery time for terrestrial insectivores in slightly and moderately disturbed forest is very long. These results illustrate the importance of long-term studies in assessing ecological impacts of forest disturbance and the importance of protecting primary forest in the Eastern Arc Mountains.
Resumen: Comparé la estructura y composición de la comunidad de aves de sotobosque en bosque primario, ligeramente perturbado y moderadamente perturbado en las Montañas East Usambara en Tanzania. Las comparaciones abarcaron dos escalas espaciotemporales: corto plazo, realizado en 1999 y 2000 en el que los tratamientos (niveles de perturbación) fueron replicados, y largo plazo, realizados entre 1989 y 2004 a largo de un gradiente de perturbación de un subconjunto de sitios de corto plazo. Utilicé modelos de captura-recaptura para evaluar la probabilidad de detección y estimar la riqueza de especies y las tasas de crecimiento poblacional. La probabilidad de detección de especies no varió significativamente entre los niveles de perturbación pero sí varió significativamente entre especies. La riqueza estimada de especies no varió significativamente entre niveles de perturbación en los muestreos de corto y largo plazo. La variabilidad temporal en la riqueza estimada de especies y la abundancia relativa de gremios no varió significativamente entre los niveles de perturbación pero dependió de la duración del muestreo. El coeficiente de variación en la riqueza de especies en el muestreo de corto plazo fue <5% en todos los niveles de perturbación, mientras que en el muestreo de largo plazo fue de 35% en el bosque ligeramente perturbado, 11% en bosque moderadamente perturbado y 0% en bosque primario. En el muestreo de corto plazo, ninguno de los siete gremios varió significativamente en abundancia relativa entre niveles de perturbación, mientras que en el muestreo de largo plazo cuatro gremios (57%) sí variaron. Los insectívoros terrestres fueron los más afectados por la perturbación del bosque. Entre 1989 y 2004, las tasas de crecimiento poblacional (λ) de las especies más comunes de insectívoros terrestres no variaron significativamente entre niveles de perturbación y fueron significativamente ≤1.00, lo que indica que el tiempo de recuperación de insectívoros terrestres en bosques ligera y moderadamente perturbados es muy largo. Estos resultados ilustran la importancia de estudios de largo plazo para evaluar los impactos ecológicos de la perturbación de bosques y la importancia de proteger el bosque primario en las Montañas Eastern Arc.
The Natura 2000 network is the most important conservation effort being implemented in Europe. Nevertheless, no comprehensive and systematic region-or nationwide evaluation of the effectiveness of the network has been conducted. We used habitat suitability models and extent of occurrence of 468 species of vertebrates to evaluate the contribution of the Natura 2000 network to biodiversity conservation in Italy. We also estimated the population size of 101 species inside the Natura 2000 network to assess its capacity to maintain or improve the population status of listed species. In general the Italian Natura 2000 did not seem to integrate existing protected areas well. The Natura 2000 network increased from 11% to 20% the area devoted to conservation in Italy and the coverage provided to areas with high biodiversity. Nevertheless, some areas with high numbers of species were devoid of conservation areas, and more than 50% of the highly irreplaceable areas were not considered in the system. Moreover, the Natura 2000 network cannot maintain 44-80% (depending on the taxa considered) of the species in a "favorable conservation status" under World Conservation Union Red List criteria. The Natura 2000 network is probably stronger than the results of our analyses suggest. The system is based on a site-specific expert-based strategy and is driven by direct and detailed knowledge of local diversity. Nevertheless, if Natura 2000 is taken to represent the final point of all the EU conservation policies, it will inevitably fail. Its role in conservation could be enhanced by integrating the Natura 2000 system into a more general strategy that considers natural processes and the ecological and evolutionary mechanisms underlying these processes.
In the Neotropics ongoing deforestation is producing open and heavily fragmented landscapes dominated by agriculture, mostly plantations and cattle pastures. After some time agriculture often becomes uneconomical and land is abandoned. Subsequent habitat regeneration may be slow because seed inputs are restricted by a lack of incentives--such as suitable roost sites--for seed dispersers to enter deforested areas. Increasing environmental awareness has fostered growing efforts to promote reforestation. Practical and cost-efficient methods for kick-starting forest regeneration are, however, lacking. We investigated whether artificial bat roosts for frugivorous bat species can attract these key seed dispersers to deforested areas, thereby increasing seed rain. We installed artificial bat roosts in a forest-pasture mosaic in the Costa Rican Atlantic lowlands and monitored bat colonization and seed dispersal. Colonization occurred within a few weeks of installation, and 10 species of bats occupied the artificial roosts. Five species of frugivorous or nectarivorous bats colonized artificial roosts permanently in both primary habitat and in deforested areas, in numbers similar to those found in natural roosts. Seed input around artificial roosts increased significantly. Sixty-nine different seed types, mostly of early-successional plant species, were transported by bats to artificial roosts in disturbed habitats. The installation of artificial bat roosts thus successfully attracted frugivorous bats and increased seed inputs into degraded sites. This method is likely to speed up early-vegetation succession, which in turn will attract additional seed dispersers, such as birds, and provide a microhabitat for seeds of mid- and late-successional plants. As well as supporting natural forest regeneration and bat conservation, this cost-efficient method can also increase environmental awareness among landowners.
The 2010 biodiversity target adopted globally and in Europe is an important political commitment for improved biodiversity conservation and management. Whether or not it is achieved will be judged by a set of biodiversity indicators now under development. We reviewed the development of these indicators in Europe and globally, paying particular attention to the need to make the indicators relevant to the purpose; to distinguish between measures of pressure, state, and response; to design and validate the indicators in context; to ensure effective communication with relevant audiences; to turn lists of measures into simple or composite indicators; and to maximize the cost-effectiveness of the indicator process. We conclude that urgent steps are needed to complete the indicator set, reduce and refine the agreed measures, ensure that work is started soon so that reliable reporting occurs in 2010, and start soon on planning for subsequent assessments.
Resumen: La meta 2010 de biodiversidad adoptada globalmente y en Europa es un propósito político importante para una mejor conservación y manejo de la biodiversidad. Si es alcanzada o no será juzgado por un conjunto de indicadores de biodiversidad que están en desarrollo. Revisamos el desarrollo de estos indicadores en Europa y globalmente, con particular atención en la necesidad de hacer que los indicadores sean relevantes para el propósito; para distinguir entre medidas de presión y respuesta; para diseñar y validar los indicadores en contexto; para asegurar una comunicación efectiva con audiencias relevantes; para convertir listas de medidas en indicadores simples o compuestos y para maximizar la rentabilidad del proceso. Concluimos que se requieren medidas urgentes para completar el conjunto de indicadores, reducir y refinar las medidas acordadas, asegurar que el trabajo comience pronto para que haya reportes confiables en 2010, y comenzar pronto con la planificación de evaluaciones subsecuentes.
Effective management of biodiversity in production landscapes requires a conservation approach that acknowledges the complexity of ecological and cultural systems in time and space. Fennoscandia has experienced major loss of forest biodiversity caused by intensive forestry. Therefore, the Countdown 2010 initiative to halt the loss of biodiversity in Europe is highly relevant to forest management in this part of the continent. As a contribution to meeting the challenge posed by Countdown 2010, we developed a spatially explicit conservation-planning exercise that used regional knowledge on forest biodiversity to provide support for managers attempting to halt further loss of biological diversity in the region. We used current data on the distribution of 169 species (including 68 red-listed species) representing different forest habitats and ecologies along with forest data within the frame of modern conservation software to devise a map of priority areas for conservation. The top 10% of priority areas contained over 75% of red-listed species locations and 41% of existing protected forest areas, but only 58% of these top priorities overlapped with core areas identified previously in a regional strategy that used more qualitative methods. We argue for aggregating present and future habitat value of single management units to landscape and regional scales to identify potential bottlenecks in habitat availability linked to landscape dynamics. To address the challenge of Countdown 2010, a general framework for forest conservation planning in Fennoscandia needs to cover different conservation issues, tools, and data needs.
The 2010 biodiversity target agreed by signatories to the Convention on Biological Diversity directed the attention of conservation professionals toward the development of indicators with which to measure changes in biological diversity at the global scale. We considered why global biodiversity indicators are needed, what characteristics successful global indicators have, and how existing indicators perform. Because monitoring could absorb a large proportion of funds available for conservation, we believe indicators should be linked explicitly to monitoring objectives and decisions about which monitoring schemes deserve funding should be informed by predictions of the value of such schemes to decision making. We suggest that raising awareness among the public and policy makers, auditing management actions, and informing policy choices are the most important global monitoring objectives. Using four well-developed indicators of biological diversity (extent of forests, coverage of protected areas, Living Planet Index, Red List Index) as examples, we analyzed the characteristics needed for indicators to meet these objectives. We recommend that conservation professionals improve on existing indicators by eliminating spatial biases in data availability, fill gaps in information about ecosystems other than forests, and improve understanding of the way indicators respond to policy changes. Monitoring is not an end in itself, and we believe it is vital that the ultimate objectives of global monitoring of biological diversity inform development of new indicators.
We applaud Berger et al. (2013) for putting the dynamics of Central Asian cashmere markets on the agenda of international conservation. We agree that intensification of cashmere production has altered livelihoods in the
region since the political changes in the early 1990s. The rising number of goats has become a major concern for conservation, and we agree with Berger et al. that, for example, in Northern Mongolia rangelands are highly
degraded and wildlife abundance is in decline. Here we present more data and literature through which we drew a different picture than they; that is, conservation dynamics are complex and cannot be reduced to single drivers.We deliberately restricted our account to a region of >400,000 km2 in southern Mongolia because it hosts many wildlife species as well as perhaps the most intact ecosystems of Central Asia, which thus have a high relevance for conservation. We agree that other rangelands
in Central Asia—especially more mesic habitats— show a partly different pattern in which the degradation of rangelands by grazing is more pronounced. Our case study is representative for large parts of the Chinese and Mongolian Gobi, where climate variability and livestock numbers are tightly linked. We reviewed the key arguments of Berger et al. and question whether the number of cashmere goats is the ultimate cause of the current challenges to conservation of wildlife in
Dynamic conservation of forest genetic resources (FGR) means maintaining the genetic diversity of trees within an evolutionary process and allowing generation turnover in the forest. We assessed the network of forests areas managed for the dynamic conservation of FGR (conservation units) across Europe (33 countries). On the basis of information available in the European Information System on FGR (EUFGIS Portal), species distribution maps, and environmental stratification of the continent, we developed ecogeographic indicators, a marginality index, and demographic indicators to assess and monitor forest conservation efforts. The pan-European network has 1967 conservation units, 2737 populations of target trees, and 86 species of target trees. We detected a poor coincidence between FGR conservation and other biodiversity conservation objectives within this network. We identified 2 complementary strategies: a species-oriented strategy in which national conservation networks are specifically designed for key target species and a site-oriented strategy in which multiple-target units include so-called secondary species conserved within a few sites. The network is highly unbalanced in terms of species representation, and 7 key target species are conserved in 60% of the conservation units. We performed specific gap analyses for 11 tree species, including assessment of ecogeographic, demographic, and genetic criteria. For each species, we identified gaps, particularly in the marginal parts of their distribution range, and found multiple redundant conservation units in other areas. The Mediterranean forests and to a lesser extent the boreal forests are underrepresented. Monitoring the conservation efficiency of each unit remains challenging; however, <2% of the conserved populations seem to be at risk of extinction. On the basis of our results, we recommend combining species-oriented and site-oriented strategies.
Books, articles, government documents, and other written accounts of tropical biology and conservation reach a tiny fraction of their potential audience. Some texts are inaccessible because of the language in which they are written. Others are only available to subscribers of developed-world journals, or distributed narrowly within tropical countries. To examine this dysfunction in the tropical literature - and what it means for conservation - we tried to compile everything ever written on the biology and conservation of the department of Madre de Dios, Peru, in southwestern Amazonia. Our search of libraries, databases, and existing bibliographies uncovered 2,202 texts totaling roughly 80,000 pages. Texts date from 1553 to 2004, but 93% were written after 1970. Since that year the publication rate has increased steadily from fewer than 10 texts/year to nearly 3 texts/week in 2004. Roughly half of the Madre de Dios bibliography is in Spanish-language texts written by Peruvian authors and mostly inaccessible outside Peru. Most of the remaining material is English-language texts written by foreign authors and largely inaccessible in Peru. Foreign authors tended to write about ecological studies with limited relevance to on-the-ground conservation challenges, whereas Peruvian authors were more likely to make specific management recommendations. The establishment of a Web-based digital library for Neotropical nature would help make the tropical literature a more efficient resource for science and conservation. Additional recommendations include investing in syntheses, translations, popular summaries, and peer-reviewed journals in tropical countries, providing incentives for management-relevant research in tropical protected areas, and reinforcing training of scientific reading and writing in tropical universities.
Many marine invertebrate species facing potential extinction have uncertain taxonomies and poorly known demographic and ecological traits. Uncertainties are compounded when potential extinction drivers are climate and ocean changes whose effects on even widespread and abundant species are only partially understood. The U.S. Endangered Species Act mandates conservation management decisions founded on the extinction risk to species based on the best available science at the time of considerationrequiring prompt action rather than awaiting better information. We developed an expert-opinion threat-based approach that entails a structured voting system to assess extinction risk from climate and ocean changes and other threats to 82 coral species for which population status and threat response information was limited. Such methods are urgently needed because constrained budgets and manpower will continue to hinder the availability of desired data for many potentially vulnerable marine species. Significant species-specific information gaps and uncertainties precluded quantitative assessments of habitat loss or population declines and necessitated increased reliance on demographic characteristics and threat vulnerabilities at genus or family levels. Adapting some methods (e.g., a structured voting system) used during other assessments and developing some new approaches (e.g., integrated assessment of threats and demographic characteristics), we rated the importance of threats contributing to coral extinction risk and assessed those threats against population status and trend information to evaluate each species' extinction risk over the 21st century. This qualitative assessment resulted in a ranking with an uncertainty range for each species according to their estimated likelihood of extinction. We offer guidance on approaches for future biological extinction risk assessments, especially in cases of data-limited species likely to be affected by global-scale threats.
Failure to account for interactions between endangered species may lead to unexpected population dynamics, inefficient management strategies, waste of scarce resources, and, at worst, increased extinction risk. The importance of species interactions is undisputed, yet recovery targets generally do not account for such interactions. This shortcoming is a consequence of species-centered legislation, but also of uncertainty surrounding the dynamics of species interactions and the complexity of modeling such interactions. The northern sea otter (Enhydra lutris kenyoni) and one of its preferred prey, northern abalone (Haliotis kamtschatkana), are endangered species for which recovery strategies have been developed without consideration of their strong predator-prey interactions. Using simulation-based optimization procedures from artificial intelligence, namely reinforcement learning and stochastic dynamic programming, we combined sea otter and northern abalone population models with functional-response models and examined how different management actions affect population dynamics and the likelihood of achieving recovery targets for each species through time. Recovery targets for these interacting species were difficult to achieve simultaneously in the absence of management. Although sea otters were predicted to recover, achieving abalone recovery targets failed even when threats to abalone such as predation and poaching were reduced. A management strategy entailing a 50% reduction in the poaching of northern abalone was a minimum requirement to reach short-term recovery goals for northern abalone when sea otters were present. Removing sea otters had a marginally positive effect on the abalone population but only when we assumed a functional response with strong predation pressure. Our optimization method could be applied more generally to any interacting threatened or invasive species for which there are multiple conservation objectives.
Roads may be one of the most common disturbances in otherwise continuous forested habitat in the southern Appalachian Mountains. Despite their obvious presence on the landscape, there is limited data on the ecological effects along a road edge or the size of the "road-effect zone." We sampled salamanders at current and abandoned road sites within the Nantahala National Forest, North Carolina (U.S.A.) to determine the road-effect zone for an assemblage of woodland salamanders. Salamander abundance near the road was reduced significantly, and salamanders along the edges were predominantly large individuals. These results indicate that the road-effect zone for these salamanders extended 35 m on either side of the relatively narrow, low-use forest roads along which we sampled. Furthermore, salamander abundance was significantly lower on old, abandoned logging roads compared with the adjacent upslope sites. These results indicate that forest roads and abandoned logging roads have negative effects on forest-dependent species such as plethodontid salamanders. Our results may apply to other protected forests in the southern Appalachians and may exemplify a problem created by current and past land use activities in all forested regions, especially those related to road building for natural-resource extraction. Our results show that the effect of roads reached well beyond their boundary and that abandonment or the decommissioning of roads did not reverse detrimental ecological effects; rather, our results indicate that management decisions have significant repercussions for generations to come. Furthermore, the quantity of suitable forested habitat in the protected areas we studied was significantly reduced: between 28.6% and 36.9% of the area was affected by roads. Management and policy decisions must use current and historical data on land use to understand cumulative impacts on forest-dependent species and to fully protect biodiversity on national lands.
Ecologists often discount presence-absence surveys as a poor way to gain insight into population dynamics, in part because these surveys are not amenable to many standard statistical tests. Still, presence-absence surveys are sometimes the only feasible alternative for monitoring large areas when funds are limited, especially for sparse or difficult-to-detect species. I undertook a detailed simulation study to compare the power of presence-absence, count, and time-to-encounter surveys to detect regional declines in a population. I used a modeling approach that simulates both population numbers and the monitoring process, accounting for observation and other measurement errors. In gauging the efficacy of presence-absence surveys versus other approaches, I varied the number of survey sites, the spatial variation in encounter rate, the mean encounter rate, and the type of population loss. My results showed that presence-absence data can be as or more powerful than count data in many cases. Quantitative guidelines for choosing between presence-absence surveys and count surveys depend on the biological and logistical constraints governing a conservation monitoring situation. Generally, presence-absence surveys work best when there is little variability in abundance among the survey sites, the organism is rare, and the species is difficult to detect so that the time spent getting to each survey site is less than or equal to the time spent surveying each site. Count surveys work best otherwise. I present a case study with count data on the Northern Flicker (Colaptes auratus) from the North American Breeding Bird Survey to illustrate how the method might be used with field-survey data. The case study demonstrates that a count survey would be the most cost-effective design but would entail reduction in the number of sites. If this site reduction is not desirable, a presence-absence survey would be the most cost-effective survey.
Effective detection of population trend is crucial for managing threatened species. Little theory exists, however, to assist managers in choosing the most cost-effective monitoring techniques for diagnosing trend. We present a framework for determining the optimal monitoring strategy by simulating a manager collecting data on a declining species, the Chestnut-rumped Hylacola (Hylacola pyrrhopygia parkeri), to determine whether the species should be listed under the IUCN (World Conservation Union) Red List. We compared the efficiencies of two strategies for detecting trend, abundance, and presence-absence surveys, under financial constraints. One might expect the abundance surveys to be superior under all circumstances because more information is collected at each site. Nevertheless, the presence-absence data can be collected at more sites because the surveyor is not obliged to spend a fixed amount of time at each site. The optimal strategy for monitoring was very dependent on the budget available. Under some circumstances, presence-absence surveys outperformed abundance surveys for diagnosing the IUCN Red List categories cost-effectively. Abundance surveys were best if the species was expected to be recorded more than 16 times/year; otherwise, presence-absence surveys were best. The relationship between the strategies we investigated is likely to be relevant for many comparisons of presence-absence or abundance data. Managers of any cryptic or low-density species who hope to maximize their success of estimating trend should find an application for our results.
Many of the challenges conservation professionals face can be framed as scale mismatches. The problem of scale mismatch occurs when the planning for and implementation of conservation actions is at a scale that does not reflect the scale of the conservation problem. The challenges in conservation planning related to scale mismatch include ecosystem or ecological process transcendence of governance boundaries; limited availability of fine-resolution data; lack of operational capacity for implementation; lack of understanding of social-ecological system components; threats to ecological diversity that operate at diverse spatial and temporal scales; mismatch between funding and the long-term nature of ecological processes; rate of action implementation that does not reflect the rate of change of the ecological system; lack of appropriate indicators for monitoring activities; and occurrence of ecological change at scales smaller or larger than the scale of implementation or monitoring. Not recognizing and accounting for these challenges when planning for conservation can result in actions that do not address the multiscale nature of conservation problems and that do not achieve conservation objectives. Social networks link organizations and individuals across space and time and determine the scale of conservation actions; thus, an understanding of the social networks associated with conservation planning will help determine the potential for implementing conservation actions at the required scales. Social-network analyses can be used to explore whether these networks constrain or enable key social processes and how multiple scales of action are linked. Results of network analyses can be used to mitigate scale mismatches in assessing, planning, implementing, and monitoring conservation projects. Discordancia de Escalas, Planificación de la Conservación y el Valor del Análisis de Redes Sociales.
Studies evaluating effects of human activity on wildlife typically emphasize short-term behavioral responses from which it is difficult to infer biological significance or formulate plans to mitigate harmful impacts. Based on decades of detailed behavioral records, we evaluated long-term impacts of vessel activity on bottlenose dolphins (Tursiops sp.) in Shark Bay, Australia. We compared dolphin abundance within adjacent 36-km2 tourism and control sites, over three consecutive 4.5-year periods wherein research activity was relatively constant but tourism levels increased from zero, to one, to two dolphin-watching operators. A nonlinear logistic model demonstrated that there was no difference in dolphin abundance between periods with no tourism and periods in which one operator offered tours. As the number of tour operators increased to two, there was a significant average decline in dolphin abundance (14.9%; 95% CI=-20.8 to -8.23), approximating a decline of one per seven individuals. Concurrently, within the control site, the average increase in dolphin abundance was not significant (8.5%; 95% CI=-4.0 to +16.7). Given the substantially greater presence and proximity of tour vessels to dolphins relative to research vessels, tour-vessel activity contributed more to declining dolphin numbers within the tourism site than research vessels. Although this trend may not jeopardize the large, genetically diverse dolphin population of Shark Bay, the decline is unlikely to be sustainable for local dolphin tourism. A similar decline would be devastating for small, closed, resident, or endangered cetacean populations. The substantial effect of tour vessels on dolphin abundance in a region of low-level tourism calls into question the presumption that dolphin-watching tourism is benign.
The task of measuring the decline of global biodiversity and instituting changes to halt and reverse this downturn has been taken up in response to the Convention on Biological Diversity's 2010 target. It is an undertaking made more difficult by the complex nature of biodiversity and the consequent difficulty in accurately gauging its depletion. In the Living Planet Index, aggregated population trends among vertebrate species indicate the rate of change in the status of biodiversity, and this index can be used to address the question of whether or not the 2010 target has been achieved. We investigated the use of generalized additive models in aggregating large quantities of population trend data, evaluated potential bias that results from collation of existing trends, and explored the feasibility of disaggregating the data (e.g., geographically, taxonomically, regionally, and by thematic area). Our results show strengths in length and completeness of data, little evidence of bias toward threatened species, and the possibility of disaggregation into meaningful subsets. Limitations of the data set are still apparent, in particular the dominance of bird data and gaps in tropical-species population coverage. Population-trend data complement the longer-term, but more coarse-grained, perspectives gained by evaluating species-level extinction rates. To measure progress toward the 2010 target, indicators must be adapted and strategically supplemented with existing data to generate meaningful indicators in time. Beyond 2010, it is critical a strategy be set out for the future development of indicators that will deal with existing data gaps and that is intricately tied to the goals of future biodiversity targets.
Pheromone-based monitoring is a promising new method for assessing the conservation status of many threatened insect species. We examined the versatility and usefulness of pheromone-based monitoring by integrating a pheromone-kairomone trapping system and pitfall trapping system in the monitoring of two saproxylic beetles, the hermit beetle Osmoderma eremita (Coleoptera: Scarabaeidae) and its predator Elater ferrugineus (Coleoptera: Elateridae), which live inside hollow trees. We performed mark-recapture studies of both species with unbaited pitfall traps in oak hollows combined with pheromone-baited funnel traps suspended from oak branches to intercept dispersing individuals. For O. eremita, the integrated trapping system showed that the population in the study sites may be considerably higher than estimates based on extrapolation from pitfall trapping alone (approximately 3400 vs. 1100 or 1800 individuals, respectively). Recaptures between odor-baited funnel traps showed that males and females had similar dispersal rates, but estimating the number of dispersing individuals was problematic due to declining recapture probability between subsequent capture events. Our conservative estimate, assuming a linear decrease in capture probability, suggested that around 1900 individuals, or at least half of the O. eremita population, may perform flights from their natal host trees, representing higher dispersal rates than previous estimates. E. ferrugineus was rarely caught in pitfall traps. One hundred thirty-nine individuals, likely almost exclusively females, were caught in odor-baited funnel traps with approximately 4% recapture probability. If recapture probability over consecutive capture events follows that of O. eremita, this would correspond to a total population size of 2500-3000 individuals of the predator; similar to its supposed prey O. eremita. Our results demonstrate that pheromone-based monitoring is a valuable tool in the study of species or life-history stages that would otherwise be inaccessible.
Classifying species according to their risk of extinction is a common practice and underpins much conservation activity. The reliability of such classifications rests on the accuracy of threat categorizations, but very little is known about the magnitude and types of errors that might be expected. The process of risk classification involves combining information from many sources, and understanding the quality of each source is critical to evaluating the overall status of the species. One common criterion used to classify extinction risk is a decline in abundance. Because abundance is a direct measure of conservation status, counts of individuals are generally the preferred method of evaluating whether populations are declining. Using the thresholds from criterion A of the International Union for Conservation of Nature (IUCN) Red List (critically endangered, decline in abundance of >80% over 10 years or 3 generations; endangered, decline in abundance of 50–80%; vulnerable, decline in abundance of 30–50%; least concern or near threatened, decline in abundance of 0–30%), we assessed 3 methods used to detect declines solely from estimates of abundance: use of just 2 estimates of abundance; use of linear regression on a time series of abundance; and use of state-space models on a time series of abundance. We generated simulation data from empirical estimates of the typical variability in abundance and assessed the 3 methods for classification errors. The estimates of the proportion of falsely detected declines for linear regression and the state-space models were low (maximum 3–14%), but 33–75% of small declines (30–50% over 15 years) were not detected. Ignoring uncertainty in estimates of abundance (with just 2 estimates of abundance) allowed more power to detect small declines (95%), but there was a high percentage (50%) of false detections. For all 3 methods, the proportion of declines estimated to be >80% was higher than the true proportion. Use of abundance data to detect species at risk of extinction may either fail to detect initial declines in abundance or have a high error rate.
Resumen: La clasificación de especies de acuerdo con su riesgo de extinción es una práctica común y es el sustento de muchas actividades de conservación. La confiabilidad de tales clasificaciones depende de la precisión de las clasificaciones de amenaza, pero se conoce poco sobre la magnitud y tipos de error que se pueden esperar. El proceso de clasificación de riesgo involucra la combinación de información proveniente de diversas fuentes, y el entendimiento de la calidad de cada fuente es crítico para la evaluación del estado general de la especie. La declinación en abundancia es un criterio común que se utiliza para clasificar el riesgo de extinción. Debido a que la abundancia es una medida directa del estatus de conservación, los conteos de individuos generalmente son el método preferido para evaluar si las poblaciones están declinando. Utilizando los umbrales del criterio A de la Lista Roja (críticamente en peligro, declinación en abundancia de >80% en 10 años o 3 generaciones; en peligro, declinación en abundancia entre 50 y 80%; vulnerable, declinación en abundancia entre 30 y 50%; menor preocupación, declinación en abundancia entre 0 y 30%) de la Unión Internacional para la Conservación de la Naturaleza (UICN), evaluamos 3 métodos utilizados para detectar declinaciones únicamente a partir de estimaciones de abundancia: uso de 2 estimaciones de abundancia, uso de regresión lineal en una serie de tiempo de abundancia; y uso de modelos de estado-espacio en una serie de tiempo de abundancia. Generamos simulaciones de datos a partir de estimaciones empíricas de la variabilidad típica en abundancia y evaluamos los 3 métodos en términos de errores de clasificación. Las estimaciones de la proporción de declinaciones detectadas falsamente con la regresión lineal y los modelos estado-espacio fueron bajas (3-14% máximo), pero 33-75% de las declinaciones pequeñas (30-50% en 15 años) no fueron detectadas. Cuando ignoramos la incertidumbre en las estimaciones de abundancia (con solo 2 estimaciones de abundancia) los modelos tuvieron mayor poder para detectar las declinaciones pequeñas (95%) pero hubo un alto porcentaje de (50%) de declinaciones falsas. Para los 3 métodos, la proporción de declinaciones estimadas en > 80% fue mayor que la proporción real. El uso de datos de abundancia para detectar especies en riesgo de extinción puede fallar en la detección de declinaciones iniciales en la abundancia o pueden tener una tasa de error alta.
The natural flow regimes of rivers worldwide have been heavily altered through anthropogenic activities, and dams in particular have a pervasive effect on riverine ecosystems. Flow-regulation effects of dams negatively affect species diversity and abundance of a variety of aquatic animals, including invertebrates and fishes. However, the effects on semiaquatic animals are relatively unknown. We conducted anuran calling surveys at 42 study locations along the Broad and Pacolet Rivers in South Carolina to address the potential effects of flow regulation by damming on anuran occupancy and abundance. We estimated occupancy and abundance with Program PRESENCE. Models incorporated distance upstream and downstream from the nearest dam as covariates and urbanization pressure as an alternative stressor. Distance from dam was associated with occupancy of 2 of the 9 anuran species in our analyses and with abundance of 6 species. In all cases, distance downstream from nearest dam was a better predictor of occupancy and abundance than distance upstream from nearest dam. For all but one species, distance downstream from nearest dam was positively correlated with both occupancy and abundance. Reduced occupancy and abundance of anurans likely resulted from downstream alterations in flow regime associated with damming, which can lead to reduced area of riparian wetlands that serve as anuran breeding habitat. Our results showed that damming has a strong negative effect on multiple anuran species across large spatial extents and suggest that flow regulation can affect semiaquatic animals occupying riparian zones.
Biological invaders can reconfigure ecological networks in communities, which changes community structure, composition, and ecosystem function. We investigated whether impacts caused by the introduced yellow crazy ant (Anoplolepis gracilipes), a pantropical invader rapidly expanding its range, extend to higher-order consumers by comparing counts, behaviors, and nesting success of endemic forest birds in ant-invaded and uninvaded rainforest on Christmas Island (Indian Ocean). Point counts and direct behavioral observations showed that ant invasion altered abundances and behaviors of the bird species we examined: the Island Thrush (Turdus poliocephalus erythropleurus), Emerald Dove (Chalcophaps indica natalis), and Christmas Island White-eye (Zosterops natalis). The thrush, which frequents the forest floor, altered its foraging and reproductive behaviors in ant-invaded forest, where nest-site location changed, and nest success and juvenile counts were lower. Counts of the dove, which forages exclusively on the forest floor, were 9-14 times lower in ant-invaded forest. In contrast, counts and foraging success of the white-eye, a generalist feeder in the understory and canopy, were higher in ant-invaded forest, where mutualism between the ant and honeydew-secreting scale insects increased the abundance of scale-insect prey. These complex outcomes involved the interplay of direct interference by ants and altered resource availability and habitat structure caused indirectly by ant invasion. Ecological meltdown, rapidly unleashed by ant invasion, extended to these endemic forest birds and may affect key ecosystem processes, including seed dispersal.
The effects of human activities in forests are often examined in the context of habitat conversion. Changes in habitat structure and composition are also associated with increases in the activity of people with vehicles and equipment, which results in increases in anthropogenic noise. Anthropogenic noise may reduce habitat quality for many species, particularly those that rely on acoustic signals for communication. We compared the density and occupancy rate of forest passerines close to versus far from noise-generating compressor stations and noiseless well pads in the boreal forest of Alberta, Canada. Using distance-based sampling, we found that areas near noiseless energy facilities had a total passerine density 1.5 times higher than areas near noise-producing energy sites. The White-throated Sparrow (Zonotrichia albicollis), Yellow-rumped Warbler (Dendroica coronata), and Red-eyed Vireo (Vireo olivaceus) were less dense in noisy areas. We used repeat sampling to estimate occupancy rate for 23 additional species. Seven had lower conditional or unconditional occupancy rates near noise-generating facilities. One-third of the species examined showed patterns that supported the hypothesis that abundance is influenced by anthropogenic noise. An additional 4 species responded negatively to edge effects. To mitigate existing noise impacts on birds would require approximately $175 million. The merits of such an effort relative to other reclamation actions are discussed. Nevertheless, given the $100 billion energy-sector investment planned for the boreal forest in the next 10 years, including noise suppression technology at the outset of construction, makes noise mitigation a cost-effective best-management practice that might help conserve high-quality habitat for boreal birds.
Agricultural landscapes are becoming an important focus of animal conservation, although initiatives to conserve predators to date have rarely provided economic benefits to agricultural producers. We examined whether introduction to vineyards of the New Zealand Falcon(Falco novaeseelandiae), a species listed as threatened by the New Zealand Department of Conservation, affected the abundance of 4 species of Passeriformes that are considered vineyard pests or affected the amount of economic loss due to grape(Vitis vinifera)damage. Three of the species were introduced and remove whole grapes from bunches(Blackbird[Turdus merula], Song Thrush[Turdus philomelos], and Starling[Sturnus vulgaris]), whereas the one native species(Silvereye[Zosterops lateralis])pecks holes in grapes.The introduction of falcons to vineyards was associated with a significant decrease in the abundance of introduced passerines and with a 95% reduction in the number of grapes removed relative to vineyards without falcons. Falcon presence was not associated with a change in the number of Silvereyes, but there was a 55% reduction in the number of grapes pecked in vineyards with falcons. Our results indicate that, relative to damage in vineyards without falcons, the presence of a falcon could potentially result in savings of US$234/ha for the Sauvignon Blanc variety of grapes and $326/ha for Pinot Noir variety of grapes.
Wildflower harvesting is an economically important activity of which the ecological effects are poorly understood. We assessed how harvesting of flowers affects shrub persistence and abundance at multiple spatial extents. To this end, we built a process-based model to examine the mean persistence and abundance of wild shrubs whose flowers are subject to harvest (serotinous Proteaceae in the South African Cape Floristic Region). First, we conducted a general sensitivity analysis of how harvesting affects persistence and abundance at nested spatial extents. For most spatial extents and combinations of demographic parameters, persistence and abundance of flowering shrubs decreased abruptly once harvesting rate exceeded a certain threshold. At larger extents, metapopulations supported higher harvesting rates before their persistence and abundance decreased, but persistence and abundance also decreased more abruptly due to harvesting than at smaller extents. This threshold rate of harvest varied with species' dispersal ability, maximum reproductive rate, adult mortality, probability of extirpation or local extinction, strength of Allee effects, and carrying capacity. Moreover, spatial extent interacted with Allee effects and probability of extirpation because both these demographic properties affected the response of local populations to harvesting more strongly than they affected the response of metapopulations. Subsequently, we simulated the effects of harvesting on three Cape Floristic Region Proteaceae species and found that these species reacted differently to harvesting, but their persistence and abundance decreased at low rates of harvest. Our estimates of harvesting rates at maximum sustainable yield differed from those of previous investigations, perhaps because researchers used different estimates of demographic parameters, models of population dynamics, and spatial extent than we did. Good demographic knowledge and careful identification of the spatial extent of interest increases confidence in assessments and monitoring of the effects of harvesting. Our general sensitivity analysis improved understanding of harvesting effects on metapopulation dynamics and allowed qualitative assessment of the probability of extirpation of poorly studied species.
Patterns of association between humans and biodiversity typically show positive, negative, or negative quadratic relationships and can be described by 3 hypotheses: biologically rich areas that support high human population densities co-occur with areas of high biodiversity (productivity); biodiversity decreases monotonically with increasing human activities (ecosystem stress); and biodiversity peaks at intermediate levels of human influence (intermediate disturbance). To test these hypotheses, we compared anthropogenic land cover and housing units, as indices of human influence, with bird species richness and abundance across the Midwestern United States. We modeled richness of native birds with 12 candidate models of land cover and housing to evaluate the empirical evidence. To assess which species were responsible for observed variation in richness, we repeated our model-selection analysis with relative abundance of each native species as the response and then asked whether natural-history traits were associated with positive, negative, or mixed responses. Native avian richness was highest where anthropogenic land cover was lowest and housing units were intermediate based on model-averaged predictions among a confidence set of candidate models. Eighty-three of 132 species showed some pattern of association with our measures of human influence. Of these species approximately 40% were negatively associated, approximately 6% were positively associated, and approximately 7% showed evidence of an intermediate relationship with human influence measures. Natural-history traits were not closely related to the direction of the relationship between abundance and human influence. Nevertheless, pooling species that exhibited any relationship with human influence and comparing them with unrelated species indicated they were significantly smaller, nested closer to the ground, had shorter incubation and fledging times, and tended to be altricial. Our results support the ecosystem-stress hypothesis for the majority of individual species and for overall species diversity when focusing on anthropogenic land cover. Nevertheless, the great variability in housing units across the land-cover gradient indicates that an intermediate-disturbance relationship is also supported. Our findings suggest preemptive conservation action should be taken, whereby areas with little anthropogenic land cover are given conservation priority. Nevertheless, conservation action should not be limited to pristine landscapes because our results showed that native avian richness and the relative abundance of many species peaked at intermediate housing densities and levels of anthropogenic land cover.
Species distribution models are critical tools for the prediction of invasive species spread and conservation of biodiversity. The majority of species distribution models have been built with environmental data. Community ecology theory suggests that species co-occurrence data could also be used to predict current and potential distributions of species. Species assemblages are the products of biotic and environmental constraints on the distribution of individual species and as a result may contain valuable information for niche modeling. We compared the predictive ability of distribution models of annual grassland plants derived from either environmental or community-composition data. Composition-based models were built with the presence or absence of species at a site as predictors of site quality, whereas environment-based models were built with soil chemistry, moisture content, above-ground biomass, and solar radiation as predictors. The reproductive output of experimentally seeded individuals of 4 species and the abundance of 100 species were used to evaluate the resulting models. Community-composition data were the best predictors of both the site-specific reproductive output of sown individuals and the site-specific abundance of existing populations. Successful community-based models were robust to omission of data on the occurrence of rare species, which suggests that even very basic survey data on the occurrence of common species may be adequate for generating such models. Our results highlight the need for increased public availability of ecological survey data to facilitate community-based modeling at scales relevant to conservation.
Relatively few studies have examined the ecological effects of group-selection timber harvesting, and nearly all have been short-term and have lacked experimental manipulations that allow pre- and posttreatment comparisons. We have been documenting the effects of a group-selection timber harvest on bird abundance in a Maine forest for 24 years (preharvest, 1983-1987; postharvest, 1988-2006). Here we characterized the trends in bird abundance over the first 20 years of the study in the managed and control halves of the 40-ha study area. Species responses to the group-selection harvest were idiosyncratic, but in general the mature-forest bird community was retained and species dependent on early successional habitat temporarily (</=8 years) benefited. The Eastern Wood-Pewee (Contopus virens), Winter Wren (Troglodytes troglodytes), Pine Warbler (Dendroica pinus), and White-throated Sparrow (Zonotrichia albicollis) increased in abundance in the managed half of the study area following timber harvest, whereas the Veery (Catharus fuscescens) decreased. The Black-and-White Warbler (Mniotilta varia), Nashville Warbler (Vermivora ruficapilla), and Common Yellowthroat (Geothlypis trichas) responded positively to harvesting, as indicated by decreases in abundance in the control area and more protracted declines or stable abundances in the managed area. This study constitutes the longest experimental investigation to date of the effects of a group-selection harvest on birds and thus provides important information on the strength, direction, and duration of temporal changes in bird populations following forest management.
Land and resource managers often use detection-nondetection surveys to monitor the populations of species that may be affected by factors such as habitat alteration, climate change, and biological invasions. Relative to mark-recapture studies, using detection-nondetection surveys is more cost-effective, and recent advances in statistical analyses allow the incorporation of detection probability, covariates, and multiple seasons. We examined the efficacy of using detection-nondetection data (relative to mark-recapture data) for monitoring population trends of a territorial species, the California Spotted Owl (Strix occidentalis occidentalis). We estimated and compared the finite annual rates of population change (λt ) and the resulting realized population change (Δt ) from both occupancy and mark-recapture data collected over 18 years (1993-2010). We used multiseason, robust-design occupancy models to estimate that territory occupancy declined during our study (Δt = 0.702, 95% CI 0.552-0.852) due to increasing territory extinction rates (ɛ̂1993 = 0.019 [SE 0.012]; ɛ̂2009 = 0.134 [SE 0.043]) and decreasing colonization rates (γ̂1993 = 0.323 [SE 0.124]; γ̂2009 = 0.242 [SE 0.058]). We used Pradel's temporal-symmetry model for mark-recapture data to estimate that the population trajectory closely matched the trends in territory occupancy (Δt = 0.725, 95% CI 0.445-1.004). Individual survival was constant during our study (ϕ̂1993 = 0.816 [SE 0.020]; ϕ̂2009 = 0.815 [SE 0.019]), whereas recruitment declined slightly (f̂1993 = 0.195 [SE 0.032]; f̂2009 = 0.160 [SE 0.023]). Thus, we concluded that detection-nondetection data can provide reliable inferences on population trends, especially when funds preclude more intensive mark-recapture studies. Relación entre Ocupación y Abundancia en una Especie Territorial, el Búho Moteado de California.
The primary goals of reserve selection are to represent all chosen units of biodiversity and to ensure their long-term persistence while minimizing costs. We considered two simple proxies of species persistence: a time series of point-count data to calculate abundance and a time series of presence-absence data to calculate permanence (a measure of consistent occupancy over time). Using two 10-year intervals of data from the North American Breeding Bird Survey, we compared the performance of each measure at predicting persistence 18 years later. For nonrare species, abundance and permanence predicted persistence similarly well. We performed complementarity-based reserve selections with data on species abundance and permanence (from 1970 to 1979) and then evaluated the effectiveness of the reserve networks at maintaining species populations and efficiency in land use (data from 1997 to 2006). Abundance proved a better predictor of future local persistence than permanence, which justifies the relatively larger financial and temporal costs of collecting a time series of point-count data to estimate abundance. If future extinction events were used as a measure of reserve-network effectiveness, the performance of abundance and permanence did not differ markedly. Nevertheless, when future abundance, which is a more sensitive measure of network effectiveness, was used, abundance was significantly better than permanence at selecting longer-term, high-quality, species-specific habitat but required larger reserves to do so.
Few researchers have investigated the synergistic effects of tropical forest fragmentation and disturbance on species persistence and abundance. We examined effects of both forest-patch metrics and forest disturbance in determining richness and abundance of midsized to large-bodied mammal species in a highly fragmented Amazonian forest landscape. Twenty-one forest fragments, ranging from 2 to 14,480 ha, and two continuous forest sites were sampled based on sightings, tracks, line-transect censuses, armadillo burrow censuses, and camera trapping. Patch occupancy of 37 species recorded ranged from 4% to all forest sites surveyed. Forest fragment size was the strongest predictor of species persistence, explaining 90% of the variation in species richness. Information-theoretic analysis confirmed that fragment area was the most important explanatory variable for the overall species richness and abundance of mammal species, followed by surface fires, which affected the abundance of seven species. Large mammal species were typically absent from fragments <100 ha, whereas some ubiquitous species were favored by fragmentation, exhibiting hyperabundance in small patches. Our findings highlight the importance of large (>10,000 ha), relatively undisturbed forest patches to maximize persistence and maintain baseline abundances of Neotropical forest mammal species.
Successful conservation of large terrestrial mammals (wildlife) on private lands requires that landowners be empowered to manage wildlife so that benefits outweigh the costs. Laikipia County, Kenya, is predominantly unfenced, and the land uses in the area allow wide-ranging wildlife to move freely between different management systems on private land. We used camera traps to sample large mammals associated with 4 different management systems (rhinoceros sanctuaries, no livestock; conservancies, intermediate stocking level; fenced ranches, high stocking level; and group ranches, high stocking level, no fencing, pastoralist clan ownership) to examine whether management and stocking levels affect wildlife. We deployed cameras at 522 locations across 8 properties from January 2008 through October 2010 and used the photographs taken during this period to estimate richness, occupancy, and relative abundance of species. Species richness was highest in conservancies and sanctuaries and lowest on fenced and group ranches. Occupancy estimates were, on average, 2 and 5 times higher in sanctuaries and conservancies as on fenced and group ranches, respectively. Nineteen species on fenced ranches and 25 species on group ranches were considered uncommon (occupancy < 0.1). The relative abundance of most species was highest or second highest in sanctuaries and conservancies. Lack of rights to manage and utilize wildlife and uncertain land tenure dampen many owners' incentives to tolerate wildlife. We suggest national conservation strategies consider landscape-level approaches to land-use planning that aim to increase conserved areas by providing landowners with incentives to tolerate wildlife. Possible incentives include improving access to ecotourism benefits, forging agreements to maintain wildlife habitat and corridors, resolving land-ownership conflicts, restoring degraded rangelands, expanding opportunities for grazing leases, and allowing direct benefits to landowners through wildlife harvesting. Efectos del Uso Privado de Suelo, Manejo de Ganado y la Tolerancia Humana sobre la Diversidad, Distribución y Abundancia de Mamíferos Mayores Africanos.
Predation on native fauna by non-native invasive mammals is widely documented, but effects of predation at the population level are rarely measured. Eradication of invasive mammals from islands has led to recovery of native biota, but the benefits of controlling invasive mammal populations in settings where eradication is not feasible are less understood. We used various combinations of aerially delivered toxic bait and control measures on the ground to reduce abundances of invasive rats (Rattus rattus) to low levels over large areas on mainland New Zealand and then monitored the abundance of invertebrates on replicated treatment sites to compare with abundances on similar nontreatment sites. We also assessed rat diet by examining stomach contents. Abundance of the rats' most-consumed invertebrate prey item, the large-bodied Auckland tree weta (Hemideina thoracica), increased 3-fold on treatment sites where we maintained rats at <4/ha for approximately 3 years, compared with the nontreatment sites. Auckland tree weta also increased in abundance on sites where rats were controlled with a single aerial-poisoning operation, but rat abundance subsequently increased on these sites and tree weta abundance then declined. Nevertheless, our data suggest that biennial reduction of rat abundances may be sufficient to allow increases in tree weta populations. Other invertebrates that were consumed less often (cave weta [Rhaphidophoridae], spiders [Araneae], and cockroaches [Blattodea]) showed no systematic changes in abundance following rat control. Our results suggest that the significant threat to recruitment and individual survival that predation by rats poses for tree weta can be mitigated by wide-scale aerial pest control.