Changes In Wildlife Populations Research Articles

Reconstructing cave past to manage and conserve cave present and future

Whilst restoration and recovery of ecosystems has become a major priority, developing a baseline of what biodiversity was like prior to disturbance, and what might have driven changes in wildlife populations often remains unknown in many systems. Challenging to access ecosystems, such as subterranean ecosystems which cannot be monitored by remote sensing and frequently have very little information provide a significant challenge to understanding how biodiversity patterns may have changed, and how they might be more effectively managed. Caves represent unique ecosystems, key sites for our own human history, but with their unique conditions and stability can provide insights into their own past use as well as an index of local climate and vegetation. In addition, caves host many of the worlds over 1400 bat species, meaning that the ability to reconstruct past population trajectories may facilitate their conservation, as well as that of the many other, often undescribed cave dependant species. Here we discuss the various types of data from biological, chemical, geological and social that can be used to reconstruct the past history of cave sites across various timescales. We discuss the considerations needed for each approach as well as providing examples to guide the application of such approaches to better understand cave systems and their varying uses over time, and highlight how such data may facilitate cave management.

Socioeconomic factors predict population changes of large carnivores better than climate change or habitat loss

Land-use and climate change have been linked to changes in wildlife populations, but the role of socioeconomic factors in driving declines, and promoting population recoveries, remains relatively unexplored. Here, we evaluate potential drivers of population changes observed in 50 species of some of the world’s most charismatic and functionally important fauna—large mammalian carnivores. Our results reveal that human socioeconomic development is more associated with carnivore population declines than habitat loss or climate change. Rapid increases in socioeconomic development are linked to sharp population declines, but, importantly, once development slows, carnivore populations have the potential to recover. The context- and threshold-dependent links between human development and wildlife population health are challenges to the achievement of the UN Sustainable development goals.

First record of a least weasel in Nunavik

The spatial distributions of several small mammals in Nunavik, Québec, Canada, currently do not rely on any recorded observations due to the rarity of wildlife surveys in that area. This is concerning because understanding changes in wildlife populations in response to the rapidly warming Arctic requires knowledge of prior population states. On 18 July 2021, my assistant and I captured a least weasel ( Mustela nivalis Linnaeus, 1766) alive, 11 km southwest of Salluit during a live-trapping session of lemmings and voles. Identification was done with the small body mass (44 g), the presence of prominent testicles indicating maturity, short length of the tail, and pale colour at the tip of the tail. All these criteria combined fit only the description of least weasels. According to the available records for this species, this observation is the first one confirmed in Nunavik. This Low Arctic area was already included in the species distribution described in the literature, but no record supported it up to now. It is of particular importance considering this species is susceptible to be designated as threatened or vulnerable in the province of Quebec according to the Centre de données sur le patrimoine naturel du Québec.

Acoustical characteristics of avian choruses in a western migratory bird refuge

Migratory bird refuge soundscapes are seasonally dynamic due to changes in wildlife populations. Some of the most prominent acoustical events in a bird refuge are the morning and evening avian choruses, particularly during spring and early summer when breeding activity of birds is high. For this study, near-continuous spectral data were collected at the U.S. Federal Fish and Wildlife Services Bear River Migratory Bird Refuge. Although data fidelity can be compromised by wind and rain, changes in the avian chorus characteristics over time are observed. Likely correlations with avian migration and refuge land management are discussed.

Spatially explicit power analysis for detecting occupancy trends for multiple species.

Assessing the statistical power to detect changes in wildlife populations is a crucial yet often overlooked step when designing and evaluating monitoring programs. Here, we developed a simulation framework to perform spatially explicit statistical power analysis of biological monitoring programs for detecting temporal trends in occupancy for multiple species. Using raster layers representing the spatial variation in current occupancy and species-level detectability for one or multiple observation methods, our framework simulates changes in occupancy over space and time, with the capacity to explicitly model stochastic disturbances at monitoring sites (i.e., dynamic landscapes). Once users specify the number and location of sites, the frequency and duration of surveys, and the type of detection method(s) for each species, our framework estimates power to detect occupancy trends, both across the landscape and/or within nested management units. As a case study, we evaluated the power of a long-term monitoring program to detect trends in occupancy for 136 species (83 birds, 33 reptiles, and 20 mammals) across and within Kakadu, Litchfield, and Nitmiluk National Parks in northern Australia. We assumed continuation of an original monitoring design implemented since 1996, with the addition of camera trapping. As expected, power to detect trends was sensitive to the direction and magnitude of the change in occupancy, detectability, initial occupancy levels, and the rarity of species. Our simulations suggest that monitoring has at least an 80% chance at detecting a 50% decline in occupancy for 22% of the modeled species across the three parks over the next 15yr. Monitoring is more likely to detect increasing occupancy trends, with at least an 80% chance at detecting a 50% increase in 87% of species. The addition of camera-trapping increased average power to detect a 50% decline in mammals compared with using only live trapping by 63%. We provide a flexible tool that can help decision-makers design and evaluate monitoring programs for hundreds of species at a time in a range of ecological settings, while explicitly considering the distribution of species and alternative sampling methods.

Urbanization Alters Swimming Performance of a Stream Fish

Human activities cause many changes in wildlife populations, including phenotypic shifts that represent adaptations to new conditions and influence population dynamics, diversity, and persistence. Although many examples of phenotypic adjustment to anthropogenic disturbance exist, we rarely know the extent to which these changes result from genetic evolution or phenotypic plasticity. Furthermore, our understanding of how whole-organism performance changes as a result of habitat alteration is very limited. We tested how urbanization, an important type of global disturbance, influences fish swimming performance in urban streams. Because urban streams have higher water velocities during rain events than rural streams, we tested for increased steady-swimming performance in fish from urbanized watersheds. Across ten populations of wild-caught Creek Chub (Semotilus atromaculatus), we found that fish from streams in more urbanized areas exhibited a longer propulsive wavelength and a lower tailbeat frequency, expending lower levels of hydromechanical power during steady swimming. In a laboratory experiment, we reared individuals collected as fry from four populations with different urbanization histories, and found evidence for genetically based differences in swimming kinematics. Laboratory-reared fish derived from urbanized populations exhibited higher locomotor efficiency, matching predictions for adaptation to urban environments. We exposed laboratory-reared Creek Chub from urban and rural populations to artificially increased water velocity for four months and observed that only some populations exhibited plasticity. Urban populations may have lost maladaptive, velocity-induced plasticity in locomotor efficiency that is still present in rural populations. Evolutionary change in freshwater species may represent a widespread yet unrecognized consequence of anthropogenic activity.

Protected areas act as a buffer against detrimental effects of climate change-Evidence from large-scale, long-term abundance data.

Climate change is driving species to shift their distributions toward high altitudes and latitudes, while habitat loss and fragmentation may hamper species ability to follow their climatic envelope. These two drivers of change may act in synergy, with particularly disastrous impacts on biodiversity. Protected areas, PAs, may thus represent crucial buffers against the compounded effects of climate change and habitat loss. However, large-scale studies assessing the performance of PAs as such buffers remain scarce and are largely based on species occurrence data. Conversely, abundance data have proven to be more reliable for addressing changes in wildlife populations under climate change. We evaluated changes in bird abundance from the 1970s-80s to the 2000s inside and outside PAs at the trailing range edge of 30 northern bird species and at the leading range edge of 70 southern species. Abundances of retracting northern species were higher and declined less inside PAs at their trailing range edge. The positive effect of PAs on bird abundances was particularly marked in northern species that rely strongly on PAs, that is, their density distribution is largely confined within PAs. These species were nearly absent outside PAs in the 2000s. The abundances of southern species were in general lower inside PAs and increased less from the 70s-80s to 2000s. Nonetheless, species with high reliance on PAs had much higher abundances inside than outside PAs in the 2000s. These results show that PAs are essential in mitigating the retraction of northern species, but also facilitate northward expansions of southern species highly reliant on PAs. Our study provides empirical evidence documenting the role of PAs in facilitating species to adjust to rapidly changing climatic conditions, thereby contributing to the mitigation of impending biodiversity loss. PAs may thus allow time for initiating wider conservation programs on currently unprotected land.

The impacts of human disturbances on the behaviour and population structure of impala (Aepyceros melampus) in the Serengeti ecosystem, Tanzania

Human activities can lead to various changes in wildlife populations’ behaviour and dynamics. Understanding specific responses to disturbances can help conservation management better protect wildlife populations to coexist with local communities. Here, we studied the response of a model ungulate species, the impala (Aepyceros melampus), to different types of human activities in the Serengeti ecosystem. Impala were studied in central Serengeti National Park (CSNP), an area with relatively low human disturbance, and, with increasing levels of human disturbance, in western Serengeti National Park (WSNP), Grumeti Game Reserve (GGR), Ikona Wildlife Management Area (IWMA), and Loliondo Game Controlled Area (LGCA); pastoralism and/or hunting are the main disturbances in these areas. We hypothesised that in the exploited GGR, IWMA and LGCA areas, 1) impala would spend more time on costly behaviours, 2) sex ratios would be more female skewed, and 3) group sizes, reproduction and recruitment ratios would be lower compared to CSNP. We found that impala spent less time resting in IWMA and LGCA, as well as a significantly lower proportion of males, and lower reproduction and recruitment ratios in LGCA. Impala synchronized their behaviour, increasing their social cohesion potentially resulting in more efficient anti-predator strategies. Human activities induced a behavioural response in impala, indicating that in less regulated areas where pastoralism and hunting are allowed, these disturbances can potentially affect impala population persistence. These results highlight the importance of protected areas for wildlife populations, and the need for continuous monitoring of the impala and other ungulate populations in less regulated areas, as the underlying anthropogenic disturbances are likely impacting diverse species.

Multi-scale dynamic maps for the management of invading and established wildlife populations: brushtail possums in New Zealand

Context The abundance and distribution of mammalian species often change in response to environmental variability, losses or gains in suitable habitat and, in the case of pest species, control programs. Consequently, conventional distribution maps rapidly become out of date and fail to provide useful information for wildlife managers. For invasive brushtail possum populations in New Zealand, the main causes of change are control programs by central and local government agencies, and post-control recovery through recolonisation and in situ recruitment. Managers need to know current, and likely future, possum population levels relative to control targets to help assess success at preventing the spread of disease or for protecting indigenous species. Information on the outcomes of government-funded possum control needs to be readily available to members of the general public interested in issues such as conservation, disease management and animal welfare. Aims To produce dynamic, scalable maps of the current and predicted future distribution and abundance of possums in New Zealand, taking into account changes due to control, and to use recent visualisation technology to make this information accessible to managers and the general public for assessing control strategies at multiple spatial scales. Methods We updated an existing individual-based spatial model of possum population dynamics, extending it to represent all individuals in a national population of up to 40 million. In addition, we created a prototype interface for interactive web-based presentation of the model’s predictions. Key results The improved capability of the new model for assessing possum management at local-to-national scales provided for real-time, mapped updates and forecasts of the distribution and abundance of possums in New Zealand. The versatility of this platform was illustrated using scenarios for current and emerging issues in New Zealand. These are hypothetical incursions of possums, reinvasion of large areas cleared of possums, and impacts on animal welfare of national-scale management of possums as vectors of bovine tuberculosis (TB). Conclusions The new individual-based spatial model for possum populations in New Zealand demonstrated the utility of combining models of wildlife population dynamics with high-speed computing capability to provide up-to-date, easily accessible information on a species’ distribution and abundance. Applications include predictions for future changes in response to incursions, reinvasion and large-scale possum control. Similar models can be used for other species for which there are suitable demographic data, typically pest species, harvested species or species with a high conservation value. Implications Models such as the spatial model for possums in New Zealand can provide platforms for (1) real-time visualisation of wildlife distribution and abundance, (2) reporting and assessing progress towards achieving management goals at multiple scales, (3) use as a decision-support tool to scope potential changes in wildlife populations or simulate the outcomes of alternative management strategies, and (4) making information about pest control publicly available.

Local knowledge to enhance wildlife population health surveillance: Conserving muskoxen and caribou in the Canadian Arctic

Monitoring and surveillance of wildlife populations, including demographics and health, is often challenging, particularly in resource-constrained and remote settings. However, in areas characterized by subsistence oriented societies, the users of renewable resources hold a vast and holistic ecological knowledge about the natural environment. This knowledge can be instrumental for understanding and early detection of changes in wildlife populations. Using qualitative research methods and participatory epidemiology techniques we documented the local knowledge from resource users of the community of Iqaluktutiaq (Nunavut, Canada) to assess the health and population status and trends for muskoxen and caribou in the area. Semi-structured individual interviews, followed by group interviews, were implemented with 38 participants, and research findings were summarized and then verified with 31 interviewees. Local knowledge identified major declines in the number of muskoxen and caribou in the study area that were corroborated by subsequent aerial population estimates for both species. Observations made by participants allowed inference of possible mechanisms for the recent population declines, including poor recruitment, poor body condition, and increased morbidity and mortality (including endemic and emerging diseases). Engaging resource users in the process of knowledge generation was useful to identify further research priorities and fostered trust among parties that facilitated the subsequent collaborative development of management plans for these species. We use our experience to illustrate that local knowledge contributes to a holistic understanding of wildlife health and can serve as an early warning system to detect changes in wildlife populations. These participatory approaches are portable to other species and settings and can enhance conservation and co-management efforts for wildlife species worldwide.

Seizures Start without Common Signatures of Critical Transition.

Complex dynamical systems may exhibit sudden autonomous changes from one state to another. Such changes that occur rapidly in comparison to the regular dynamics have been termed critical transitions. Examples of such phenomena can be found in many complex systems: changes in climate and ocean circulation, changes in wildlife populations, financial crashes, as well as in medical conditions like asthma attacks and depression. It has been recognized that critical transitions, even if they arise in completely different contexts and situations, share several common attributes and also generic early-warning signals that indicate that a critical transition is approaching. In the present study, we review briefly the general characteristics that have been observed in systems prior to critical transitions and apply these general indicators to nearly 300 epileptic seizures collected from human subjects using invasive EEG. Only in about 8% of the patients was evidence of critical transitions found. In the remaining majority of cases no early warning signals that behaved consistently prior to seizures were observed. These results do not rule out the possibility of critical transitions to seizure but point to limited relevance of their early warning signals in the context of human epilepsy observed using intracranial EEG recordings.

Hope for Tropical Biodiversity After All.

Much as Mark Twain famously stated that reports of his death were greatly exaggerated, it turns out that land animals in tropical protected areas may be better off than we thought. Current assessments warn of widespread biodiversity loss in the tropics—which is home to half of species globally—and put declines as high as 56% over the last four decades. But now, in this issue of PLOS Biology, Lydia Beaudrot, Jorge Ahumada, and colleagues report that tropical forest preserves around the world may be helping after all: at the community level, ground-dwelling mammals and birds are holding their own. Why the difference? Tropical forests are understudied, and most of the animals living there are rare and elusive, so existing biodiversity assessments rely heavily on aggregated secondary data and expert opinion. In contrast, the new findings are based on standardized primary data from camera traps in the Tropical Ecology Assessment and Monitoring (TEAM) Network, which give close-to-real-time snapshots of wildlife status and trends (Fig 1). Fig 1 Camera traps in remote tropical forests around the world provide insight into the status of rare and endangered wildlife, such as these African bush elephants (Loxodonta africana). Beaudrot, Ahumada, and colleagues determined biodiversity trends for more than 500 populations of nearly 250 species of mammals and birds, using half a million images per year from tropical forest preserves on three continents. The distribution of the 15 study sites reflected the proportion of tropical forest cover on each continent: half were in South and Central America, and the remainder were split between Africa and Southeast Asia. Each of the protected areas studied had a camera trap every square kilometer or two, for a total of 60 to 90 per site. Even so, camera sightings were infrequent—five per year for a given population was not uncommon—and the researchers used occupancy as a proxy for abundance. Analysis of the sightings showed that occupancy declined in 22%, increased in 17%, and did not change in 22% of the populations during the study period, which ranged from three to eight years depending on the site. Further analysis of the camera trap images revealed encouraging news: despite the variability in occupancy trends, biodiversity did not decline systematically at the community level in the protected areas studied. Importantly, occupancy trends did not vary significantly between mammals and birds, or by International Union for Conservation of Nature (IUCN) Red List status. The latter suggests that, at least in the study sites, populations of Threatened and Near Threatened species are doing as well as those of Least Concern. However, sightings were too low to determine trends for nearly two-fifths of the populations studied, leading the researchers to caution that the observed community-level stability could mask wildlife losses in protected areas. The researchers also underscore that their findings do not apply to the many unprotected tropical forests worldwide. Today's extinction rates are estimated to be 1,000 times faster than the average over the history of life on Earth, and this catastrophic species loss occurs disproportionately in the tropics. These caveats aside, this work gives hope that species loss in protected tropical forests is less severe than we feared. Moreover, for the first time, conservation decisions can be based on real-time changes in wildlife populations. Some 200 nations have committed to a suite of protection measures—increasing protected areas, preventing extinctions, and reversing wildlife declines—by 2020. This work provides governments and nonprofits with tools for identifying successful strategies to preserve the biodiversity that remains while we still can.

Using independent nest survey data to validate changes in reporting rates of Martial Eagles between the Southern African Bird Atlas Project 1 and 2

Repeat monitoring is vital to measure biodiversity change. However, monitoring protocols may change, as survey techniques improve or different questions are asked. Such modifications may cause difficulties when examining changes in wildlife populations. The Southern African Bird Atlas Project (SABAP) 1 and 2 are repeat national bird surveys undertaken 20 years apart. These surveys therefore offer unrivalled potential to examine bird population changes in an African context. However, changes in protocols, both spatially and temporally, between the two surveys have raised concerns over using these data to infer population changes. In this study we use independ- ent nest survey data to test whether changes in reporting rates of Martial Eagles in the Kalahari Gemsbok National Park between the two SABAP surveys were reflected in real change in numbers of nesting pairs. From 11 quarter degree squares (QDS), covering c. 8 000 km2, both SABAP and nest surveys suggested a near identical 44% decline. Levels of agreement were weaker at the individual QDS scale, although in 67% of cases the direction of change was the same using both surveys. These results suggest that comparisons in the reporting rates between SABAP 1 and SABAP 2 accurately reflect changes in the breeding population size of this species.

Effectiveness of the Integrated Conservation and Development Program (ICDP) in conserving wildlife in the Annapurna Conservation Area in Nepal

Nepal has established 22 protected areas (PAs) with the primary aim of conserving wildlife biodiversity. The protected area system of Nepal has gone through various stages of trial and learning. Various problems relating to management of protected areas have emerged during such trials and processes. In the course of this process, the Integrated Conservation and Development Program (ICDP) approach in protected area management has emerged as an important tool to link conservation and development, with the aim of resolving various problems associated with existing protected area management regimes in the country. We investigated the success of the ICDP approach from the perspective of wildlife conservation. The perceived success of the ICDP approach to conserving wildlife in protected area management systems was examined in the Annapurna Conservation Area (ACA), Nepal. An extensive field study was carried out with selected Village Development Committees (VDCs) within the ACA. We employed a social survey method using tools such as, Participatory Rural Appraisal (PRA), structured and semi-structured interviews, and a questionnaire survey conducted in two VDCs. Participatory tools such as matrices were also used to gain further insights into impact of the ICDP approach. We found that a significant positive impact resulted from the ICDP approach in study sites when compared with the pre-ICDP scenario. This study suggests that the Snow Leopard (Uncia uncial), Blue Sheep (Psedois nayaur) and Musk Deer (Moschus moischiferous) populations have increased since implementing the ICDP approach. Participatory tools, such as, interactive matrices, involving local people were used to obtain insights and identify changes in wildlife populations. Based on these findings, we argue that the ICDP approach is significantly enhancing wildlife conservation efforts throughout the ACA and it can also be stated that the ICDP approach could be a better alternative to the conventional approach of the protected area management systems in Nepal.

State‐and‐Transition Models for Assessing Grasshopper Sparrow Habitat Use

ABSTRACT The combination of ecological site descriptions and state‐and‐transition models (STMs) describes potential vegetation, plant composition, and plant community dynamics and thus can be used to classify and understand dynamics of wildlife habitats across landscapes or home ranges. Numerous studies have evaluated effects of plant community dynamics on diversity and abundance of wildlife populations, but we could find no studies that examined changes in wildlife populations with respect to STMs. We compared abundance of grasshopper sparrows (Ammodramus savannarum) across 5 community phases representing 2 different ecological states in the Columbia Basin, Oregon, USA, to evaluate utility of STMs for understanding and predicting potential changes in habitat use by wildlife species. We measured grasshopper sparrow abundance in 165 100‐m fixed‐radius point counts distributed across 17 study plots within 5 plant community phases: native perennial grassland, sagebrush‐steppe, depleted sagebrush‐steppe, sagebrush‐steppe with an annual grass understory, and annual grassland. We used a general estimating equation with a Poisson distribution to model relative abundance and estimate differences in this abundance index between linked pairs of community phases. Grasshopper sparrows showed clear differences in abundance among community phases and were most numerous in perennial grasslands and least abundant in depleted sagebrush and sagebrush annual grass community phases. As a management tool, STM provides information that predicts the direct and indirect cumulative impacts of various management actions on vegetation composition and structure (and thus habitat). Ecological site descriptions and STMs enable land managers and scientists to assess potential and current wildlife habitat suitability and to predict potential response of wildlife populations to vegetation dynamics based on the ecological potential of the site.

Long-term avian research at the San Joaquin Experimental Range: Recommendations for monitoring and managing oak woodlands

Experimental forests and ranges are living laboratories that provide opportunities for conducting scientific research and transferring research results to partners and stakeholders. They are invaluable for their long-term data and capacity to foster collaborative, interdisciplinary research. The San Joaquin Experimental Range (SJER) was established to develop appropriate land management practices on foothill rangelands in California. SJER has a long and rich history of avian research. Natural history observations recorded since 1935 demonstrate that oak woodlands are one of the most diverse habitat types in North America. Early avian studies focused on California quail ( Callipepla californica) as a game species and led to insights on quail diet and habitat requirements. Starting in the late 1970s, the focus of avian research shifted to methods for detecting changes in wildlife populations over time and response to management practices. This research has led to important recommendations for implementing bird monitoring programs. Using data collected on bird numbers, in conjunction with monitoring reproductive success of all species, recent studies have examined life history strategies, source–sink dynamics, the effects of livestock grazing, and the impacts of an invasive species on native cavity-nesting species. We are currently in the process of examining population trends and predicting the effects of climate change using long-term data. SJER continues to provide unique opportunities for research and educational activities that increase our understanding of the foothill oak woodlands of California.

The impact of subdivision and sedentarization of pastoral lands on wildlife in an African savanna ecosystem

This study looks at the impact of subdivision and sedentarization of pastoral lands on wildlife numbers and production in a savanna ecosystem of southern Kenya. The study uses aerial counts over a period of 33 years to compare changes in wildlife populations on two adjacent and ecologically similar Maasai group ranches. During the period under study, one group ranch was subdivided and settled. The other remained communally owned under shifting seasonal use. Wildlife populations decreased sharply on the privatized ranch following subdivision and increased steadily on the adjacent ranch where pastoralists continued mobile pastoralism. The results of multivariate analysis show that sedentarization and settlement distribution accounts for wildlife declines on the subdivided ranch. Both the direct displacement of wildlife and the reduction in grass production following a switch from seasonal to permanent grazing associated with sedentarization are discussed as causes of wildlife loss. Given the demand for title deeds among pastoralists to counter land losses, the resulting sedentarization is likely to become the biggest threat to wildlife in the East African savannas.

Estimating Site Occupancy and Detection Probability Parameters for Meso- And Large Mammals in a Coastal Ecosystem

Large-scale, multispecies monitoring programs are widely used to assess changes in wildlife populations but they often assume constant detectability when documenting species occurrence. This assumption is rarely met in practice because animal populations vary across time and space. As a result, detectability of a species can be influenced by a number of physical, biological, or anthropogenic factors (e.g., weather, seasonality, topography, biological rhythms, sampling methods). To evaluate some of these influences, we estimated site occupancy rates using species-specific detection probabilities for meso- and large terrestrial mammal species on Cape Cod, Massachusetts, USA. We used model selection to assess the influence of different sampling methods and major environmental factors on our ability to detect individual species. Remote cameras detected the most species (9), followed by cubby boxes (7) and hair traps (4) over a 13-month period. Estimated site occupancy rates were similar among sampling methods for most species when detection probabilities exceeded 0.15, but we question estimates obtained from methods with detection probabilities between 0.05 and 0.15, and we consider methods with lower probabilities unacceptable for occupancy estimation and inference. Estimated detection probabilities can be used to accommodate variation in sampling methods, which allows for comparison of monitoring programs using different protocols. Vegetation and seasonality produced species-specific differences in detectability and occupancy, but differences were not consistent within or among species, which suggests that our results should be considered in the context of local habitat features and life history traits for the target species. We believe that site occupancy is a useful state variable and suggest that monitoring programs for mammals using occupancy data consider detectability prior to making inferences about species distributions or population change.

How Much is Enough? Estimating the Minimum Sampling Required for Effective Monitoring of African Reserves

Effective biological monitoring in developing countries requires a balance of rigour and practicality. Unfortunately, there exist few general guidelines to help practitioners design monitoring programs that reach this balance. Here, we analyse a 33-year monitoring program from Ghana, West Africa, to provide both specific and general suggestions for monitoring in developing countries. Since the late 1960s the Ghana Wildlife Division has monitored more than 40 wildlife species with monthly surveys at sites throughout Ghana's nature reserves. These data present unparalleled opportunities to illuminate the scale and pattern of changes in animal abundance over time and the forces that drive these changes. We used sub-sampling of the Ghana monitoring data for four species in two savanna reserves to identify the minimum level of monitoring necessary to reliably detect changes in wildlife populations over 5-year intervals. We used a similar approach to estimate the minimum sampling needed to infer changes in abundance of hunters in reserves. Our results highlight the relative importance of comprehensive spatial and temporal sampling and suggest a requirement of no less than one monitoring site per every 285 km2 in large reserves and 65 km2 in smaller reserves. We discuss briefly the cost of effective monitoring and the relevance of our results to other regions of Africa and the world.

Long-term climatic trend and body size variation in teal Anas crecca

A general warming of climate in the future may profoundly affect wildlife populations in terms of numbers, distribution and characteristics of the individuals, therefore leading to new challenges in terms of management and conservation. The effects of global warming can already be detected through the analysis of long-term databases, but insights into these processes can also be acquired by studying changes in wildlife populations during periods with clear trends in climatic changes. We analysed ringing data from more than 38,000 teal Anas crecca caught at the Station Biologique de la Tour du Valat in the Camargue, Southern France, between September 1954 and April 1971. Temperature in the Camargue clearly decreased over the ringing period. There was no correlation between average annual body mass and temperature in any age or sex class, nor a significant effect of temperature on the age ratio of the population. In adults, there were more males when average daily maximum winter temperature increased, while the opposite trend was found for juveniles. The clearest pattern we observed was a positive relationship between temperature and wing length of the individuals: in all sex and age classes, birds tended to get smaller as temperature decreased. It is unlikely that this pattern was related to harsh climate affecting teal feather growth. Rather, we hypothesise that climate affected the distribution of the individuals in Europe: as temperature got colder, small birds found it still more difficult to remain in northern areas and increasingly used the Camargue as a refuge. Reversing the observed pattern suggests that a global warming of climate in the future may have profound consequences for the distribution of wintering teal in Europe, as more and more birds will become able to remain in northern areas closer to their breeding grounds.