Following historical restrictions to isolated and patchy populations, large carnivores like the brown bear Ursus arctos are recolonizing areas of their historical range in Europe. This process is of ...particular interest in the Alps and the Dinaric Mountains in Central Europe, the largest mountain range in the continent and of transboundary conservation interest. To assist policies focused on the expansion of bears in this region, we conducted habitat selection analyses accounting for different behaviour between three populations (Trentino, pre‐Alps and Dinaric) where bears have adapted to different intensities of human persecution. We then identified the landscape connectivity between these fragmented populations that could provide viable habitat and stepping‐stone patches for recolonization. To handle individual and population differences in space‐use, we modelled habitat selection per population from an individual‐level and integrated results into a multi‐population model using scale‐integrated resource selection functions. We then calculated connectivity indices per patch and the contribution of various countries involved in bear management in the region to enhancing connectivity. Bears mostly selected forests across all populations while preferences for other variables differed among populations and across scales. Bears in the highly humanized habitats of the Trentino selected the most intricate topography, where they could more easily find refuge. Suitable but fragmented habitat patches were common all over the study area with the most suitable habitat in the pre‐Alpine and Dinaric populations. However, the Trentino and pre‐Alp included the patches of maximum/medium priority as stepping‐stones to connect these populations. Transboundary initiatives for the conservation of existing habitat and the facilitation of connectivity are required to promote current bear expansion and reduce conflicts with humans. Our framework provides insight into the adaptive behaviour of large carnivores in human‐dominated landscapes in a conservation context.
Large carnivores like the brown bear Ursus arctos are recolonizing areas of their historical range in Europe in processes of transboundary conservation interest. We conducted multi‐population and multiscale habitat selection analyses of three populations in the Alps and Dinaric Mountains, where bears have adapted to different intensities of human persecution. We also identified the landscape connectivity between these fragmented populations and the contribution of various countries to enhancing this connectivity. Bears mostly selected forests across all populations and in the highly human‐dominated habitats of the Trentino selected the most intricate topography, ensuring refuge. Suitable but fragmented habitat patches were common all over the study area, and the Trentino and pre‐Alp included the patches of maximum/medium priority as stepping‐stones to connect these populations. Transboundary initiatives for conservation and connectivity are required to promote current bear expansion while reducing conflicts with humans.
The Eurasian lynx is of special conservation concern based on the European Union's Habitat Directive and its populations need to be maintained or restored at favourable conservation status. To ...evaluate lynx population status, appropriate monitoring needs to be in place. We modelled the distribution dynamics of lynx in the Alps (200 000 km2) during 1994–2014 at a resolution of 100 km2. Lynx distribution and detection probability varied by year, country, forest cover, elevation and distance to the nearest release site. Occupancy of neighbouring quadrats had a strong positive effect on colonization and persistence rates. Our analyses demonstrate the importance of accounting for imperfect detection: the raw data underestimated the lynx range by 55% on average, depending on country and winter. Over the past 20 years the Alpine lynx range has expanded at an average rate of 4% per year, which was partly due to the lynx translocations to new areas. Our approach to large‐scale distribution modelling and analysing trends using site occupancy models can be applied retrospectively and is useful in many cases where a network of trained people is established to report the presence of target species, for example, in Europe where member states of the European Union have to report conservation status of species of community interest. Hence, dynamic occupancy models are an appealing framework for inference about the large‐scale range dynamics based on opportunistic data and a useful tool for large‐scale management and conservation programmes.
We analysed range dynamics of a reintroduced large carnivore, the Eurasian lynx, in the Alps (200 000 km2) over 20 years, combining a cutting edge occupancy model with citizen science. Lynx distribution and detection probability varied by distance to the nearest release site, year, forest cover, elevation and country. Occupancy of neighbouring quadrats had a strong positive effect on colonization and persistence rates. Our analyses demonstrate the importance of accounting for imperfect detection: the raw data underestimated the lynx range by 55% on average. Over the past 20 years the Alpine lynx range expanded at an average rate of 4% per year, which was partly due to the lynx translocations to new areas. Our approach to large‐scale distribution modelling and analysing trends using site occupancy models can be applied retrospectively and is useful in many cases where a network of trained people is established to report the presence of target species.
Inferring the distribution and abundance of a species from field records must deal with false‐negative and false‐positive errors. False‐negative errors occur if a species present goes undetected, ...while false‐positive errors are typically a consequence of species misidentification. False‐positive observations in studies of rare species may cause an overestimation of the distribution or abundance of the species and distort trend indices. We illustrate this issue with the monitoring of the Eurasian lynx in the Alps. We developed a three‐level classification of field records according to their reliability as inferred from whether they were validated or not. The first category (C1) represents ‘hard fact’ data (e.g. dead lynx); the second category (C2) includes confirmed data (e.g. tracks verified by an expert); and the third category (C3) are unconfirmed data (e.g. any kind of direct visual observation). For lynx, which is a comparatively well‐known species in the Alps, we use site‐occupancy modelling to estimate its distribution and show that the inferred lynx distribution is highly sensitive to presence sign category: it is larger if based on C3 records compared with the more reliable C1 and C2 records. We believe that the reason for this is a fairly high frequency of false‐positive errors among C3 records. This suggests that distribution records for many lesser‐known species may be similarly unreliable, because they are mostly or exclusively based on unconfirmed and thus soft data. Nevertheless, such soft data form a considerable part of species assessments as presented, for example in the International Union for Conservation of Nature Red List. However, C3 records can often not be discarded because they may be the only information available. When inferring the distribution of rare carnivores, especially for species with an expanding or shrinking range, we recommend a rigorous discrimination between fully reliable and un‐ or only partly reliable data, in order to identify possible methodological problems in the distribution maps related to false‐positive records.
In a multi-prey system, predators kill different kinds of prey according to their availability, where "availability" is a function of prey abundance and vulnerability (e.g. anti-predator behavior). ...We hypothesized that prey availability changes seasonally, for instance because reproduction leads to a higher abundance of young in spring and summer or because changes in behavior such as during the mating season makes the prey periodically more vulnerable. We tested this hypothesis in a simple predator-prey system in the Jura Mountains of Switzerland and France, where a single large mammalian predator, the Eurasian lynx, preys upon two ungulate species, the roe deer and the chamois. In 1996 and 1997 we were able to assign a total of 190 roe deer and 54 chamois killed by lynx to a specific age and sex class (males, females or juveniles). As expected, the proportion of juveniles killed varied considerably among periods, being at the highest from 1st of June to 15th of August. No significant seasonal differences were detected regarding the frequency of predation on males versus females. In particular, the interaction between species and period, expected because of different timing of the rutting period between roe deer and chamois, was not significant. Females were killed only slightly more often during gestation. The relationship between prey abundance and vulnerability is highly complex, as the lynx' prey selection needs to be analyzed not only horizontally (changes of a specific prey category with season) but also vertically (an increase in the vulnerability of one category releases predation pressure on others). Second, we predicted that certain activities, such as feeding, expose prey to predation more than others. We found more chamois predated when feeding, whereas roe deer were predated mainly when ruminating. This interspecific discrepancy reflects differences either in the anti-predator behavior of roe deer and chamois or in the relative time allocation to feeding and ruminating between the two species.
Prey class selection and kill rates by lynx Lynx lynx were studied in the Swiss Jura Mountains from March 1988 until May 1998 to evaluate the significance of lynx predation for roe deer Capreolus ...capreolus and chamois Rupicapra rupicapra. We found clear differences in the kill rates and prey class selection between lynx of different age, sex and breeding status. Male lynx killed more chamois than female lynx, and chamois was never found in kill series of subadult lynx. Family groups had the highest kill rate. They killed an ungulate every 5.0 days, compared to an average of 6.2–6.6 days for single lynx. During our 10-year study, the density of independent lynx was rather stable, ranging within 0.94–1.01 individuals/100 km2. Based on the observed kill rates and the estimated lynx population structure we calculated that lynx killed 354 ± 13 roe deer and 87 ±13 chamois annually in the 710 km2 study area. The magnitude of lynx predation on roe deer and chamois was primarily shaped by the lynx population structure. A decline in the number of resident male lynx reduced the number of chamois killed in the study area by ¼ of the previous number due to the difference in prey selection of male and female lynx. There was a difference in the most frequently killed age and sex classes between roe deer and chamois: lynx killed more male chamois (39%) than females or fawns, whereas in roe deer, does (38%) were most often killed. By altering adult survival, lynx predation has a significant impact on prey population dynamics. Lynx killed a maximum of 9% of the roe deer and 11 % of the chamois spring population. Considering the differences in the recruitment potential of the two prey species, lynx has a greater impact on chamois than on roe deer.
Abstract Inferring the distribution and abundance of a species from field records must deal with false‐negative and false‐positive errors. False‐negative errors occur if a species present goes ...undetected, while false‐positive errors are typically a consequence of species misidentification. False‐positive observations in studies of rare species may cause an overestimation of the distribution or abundance of the species and distort trend indices. We illustrate this issue with the monitoring of the E urasian lynx in the A lps. We developed a three‐level classification of field records according to their reliability as inferred from whether they were validated or not. The first category ( C 1) represents ‘hard fact’ data (e.g. dead lynx); the second category ( C 2) includes confirmed data (e.g. tracks verified by an expert); and the third category ( C 3) are unconfirmed data (e.g. any kind of direct visual observation). For lynx, which is a comparatively well‐known species in the A lps, we use site‐occupancy modelling to estimate its distribution and show that the inferred lynx distribution is highly sensitive to presence sign category: it is larger if based on C 3 records compared with the more reliable C 1 and C 2 records. We believe that the reason for this is a fairly high frequency of false‐positive errors among C 3 records. This suggests that distribution records for many lesser‐known species may be similarly unreliable, because they are mostly or exclusively based on unconfirmed and thus soft data. Nevertheless, such soft data form a considerable part of species assessments as presented, for example in the I nternational U nion for C onservation of N ature R ed L ist. However, C 3 records can often not be discarded because they may be the only information available. When inferring the distribution of rare carnivores, especially for species with an expanding or shrinking range, we recommend a rigorous discrimination between fully reliable and un‐ or only partly reliable data, in order to identify possible methodological problems in the distribution maps related to false‐positive records.
To evaluate the 2000–2004 status of lynx in the Swiss Alps, we outlined the trend within the large carnivore management compartments and estimated the number of lynx present. Throughout Switzerland ...all reports of lynx signs of presence were collected and classified according to their reliability. From 2000–2004, more than 2000 signs of lynx presence were recorded from the Swiss Alps. The trend of the confirmed records collected over all of Switzerland showed that (1) the lynx population in the North-western Alps decreased compared to the previous pen- tad but nevertheless this compartment remained the area with the highest lynx density within Switzerland, (2) in the Valaisand Central Switzerland West the trend is slightly positive, (3) due to the translocation project, the distribution of lynx in the Swiss Alps has considerably increased and (4) that there is still good lynx habitat yet to be colonised in the Swiss Alps. To estimate the number of lynx, we used findings from systematic camera trap sessions and a radio-telemetry study as well as our expert guess. We estimated the number of lynx in 2004 at 60–90 individuals. Compared to the previous pentad, when the number of lynx in the Swiss Alps was estimated at 70, the number of lynx remained fairly stable. An expansion in the total distribution was compensated for by a decrease in the North-western Alps.
As large carnivores recover throughout Europe, their distribution needs to be studied to determine their conservation status and assess the potential for human‐carnivore conflicts. However, efficient ...monitoring of many large carnivore species is challenging due to their rarity, elusive behavior, and large home ranges. Their monitoring can include opportunistic sightings from citizens in addition to designed surveys. Two types of detection errors may occur in such monitoring schemes: false negatives and false positives. False‐negative detections can be accounted for in species distribution models (SDMs) that deal with imperfect detection. False‐positive detections, due to species misidentification, have rarely been accounted for in SDMs. Generally, researchers use ad hoc data‐filtering methods to discard ambiguous observations prior to analysis. These practices may discard valuable ecological information on the distribution of a species. We investigated the costs and benefits of including data types that may include false positives rather than discarding them for SDMs of large carnivores. We used a dynamic occupancy model that simultaneously accounts for false negatives and positives to jointly analyze data that included both unambiguous detections and ambiguous detections. We used simulations to compare the performances of our model with a model fitted on unambiguous data only. We tested the 2 models in 4 scenarios in which parameters that control false‐positive detections and true detections varied. We applied our model to data from the monitoring of the Eurasian lynx (Lynx lynx) in the European Alps. The addition of ambiguous detections increased the precision of parameter estimates. For the Eurasian lynx, incorporating ambiguous detections produced more precise estimates of the ecological parameters and revealed additional occupied sites in areas where the species is likely expanding. Overall, we found that ambiguous data should be considered when studying the distribution of large carnivores through the use of dynamic occupancy models that account for misidentification.
Uso de Detecciones Ambiguas para Mejorar las Estimaciones a partir de Modelos de Distribución de Especies
Resumen
Conforme los carnívoros mayores se recuperan en toda Europa, su distribución requiere ser estudiada para determinar su estado de conservación y para evaluar el potencial de conflictos entre humanos y carnívoros. Sin embargo, el monitoreo eficiente de muchas especies de carnívoros mayores es complicada debido a su rareza, comportamiento elusivo y las grandes extensiones de su ámbito de hogar. Su monitoreo puede incluir avistamientos oportunistas por parte de los ciudadanos, además de los censos diseñados. Pueden ocurrir dos tipos de errores de detección en dichos métodos de monitoreo: negativos falsos y negativos positivos. La detección de los falsos negativos puede justificarse en los modelos de distribución de especies (MDE) que manejan la detección imperfecta. La detección de falsos positivos por causa de la identificación errónea rara vez se justifica en los MDE. Los investigadores usan generalmente métodos con filtración de datos ad hoc para descartar las observaciones ambiguas previo al análisis. Estas prácticas pueden descartar información ecológica variable sobre la distribución de una especie. Investigamos los costos y beneficios de la inclusión de tipos de datos que podrían contener falsos positivos en lugar de descartarlos de los MDE para carnívoros mayores. Usamos un modelo dinámico de ocupación que justificó simultáneamente los falsos positivos y falsos negativos para analizar en conjunto los datos que incluían tanto las detecciones no ambiguas como las ambiguas. Usamos simulaciones para comparar el desempeño de nuestro modelo con el de un modelo ajustado solamente para datos no ambiguos. Probamos los dos modelos en cuatro escenarios en los que variaron los parámetros que controlan la detección de falsos positivos y de detecciones verdaderas. Aplicamos nuestro modelo a datos del monitoreo del lince euroasiático (Lynx lynx) en los Alpes. La suma de las detecciones ambiguas incrementó la precisión de las estimaciones de los parámetros. Para el lince euroasiático, la incorporación de las detecciones ambiguas produjo estimaciones más precisas de los parámetros ecológicos y reveló sitios ocupados adicionales en áreas en donde la especie probablemente se esté expandiendo. En general, encontramos que los datos ambiguos deberían ser considerados cuando se estudia la distribución de carnívoros mayores por medio del uso de modelos dinámicos de ocupación que justifican la identificación errónea.
摘要
随着欧洲大型食肉动物的恢复, 我们需要研究这些物种的分布以确定它们的保护现状, 并评估人兽冲突的可能性。然而, 由于大型食肉动物的稀有性、回避行为和较大的活动范围, 对它们进行有效监测困难重重。大型食肉动物的监测除了设计调查外, 还可以包含公民的偶然目击。这样的监测方案可能出现两类检测误差: 假阴性和假阳性。假阴性的监测结果可用于物种分布模型分析, 该模型可处理有缺陷的监测。而因物种鉴定错误产生的假阳性结果在物种分布模型中却很少被考虑在内。通常情况下, 研究者在分析前会用特定的数据过滤方法来去除不确定的观察数据。这种做法也可能丢掉对物种分布有价值的生态学信息。我们研究了保留可能含有假阳性发现的数据类型 (而不是丢弃这些数据) 对大型食肉动物物种分布模型的利弊。我们利用同时考虑假阴性和阳性的动态占有模型, 共同分析了包含确定发现和不确定发现的数据。通过模拟, 我们比较了这个模型和仅用真实数据拟合的模型的表现。我们选择了不同的控制假阳性和真阳性的参数, 在四种情况下检验了这两个模型。我们还将这一模型应用于欧洲阿尔卑斯山脉的欧亚猞猁 (Lynx lynx) 的监测数据, 加入不确定的发现数据可以提高参数估计的精确度。对欧亚猞猁来说, 加入不确定的发现可以对生态学参数作出更精确的估计, 揭示这个物种的分布范围可能正在扩张。总之, 我们的研究表明, 在研究大型食肉动物的分布时, 可以用考虑到物种鉴定错误的动态占有模型来利用不确定的数据。翻译: 胡怡思; 审校: 聂永刚
Article impact statement: Use of ambiguous detections can improve understanding of large‐carnivore distribution dynamics.
The ecology and evolution of reproductive timing and synchrony have been a topic of great interest in evolutionary ecology for decades. Originally motivated by questions related to behavioral and ...reproductive adaptation to environmental conditions, the topic has acquired new relevance in the face of climate change. However, there has been relatively little research on reproductive phenology in mammalian carnivores. The Eurasian lynx (Lynx lynx) occurs across the Eurasian continent, covering three of the four main climate regions of the world. Thus, their distribution includes a large variation in climatic conditions, making it an ideal species to explore reproductive phenology. Here, we used data on multiple reproductive events from 169 lynx females across Europe. Mean birth date was May 28 (April 23 to July 1), but was ~10 days later in northern Europe than in central and southern Europe. Birth dates were relatively synchronized across Europe, but more so in the north than in the south. Timing of birth was delayed by colder May temperatures. Severe and cold weather may affect neonatal survival via hypothermia and avoiding inclement weather early in the season may select against early births, especially at northern latitudes. Overall, only about half of the kittens born survived until onset of winter but whether kittens were born relatively late or early did not affect kitten survival. Lynx are strict seasonal breeders but still show a degree of flexibility to adapt the timing of birth to surrounding environmental conditions. We argue that lynx give birth later when exposed to colder spring temperatures and have more synchronized births when the window of favorable conditions for raising kittens is shorter. This suggests that lynx are well adapted to different environmental conditions, from dry and warm climates to alpine, boreal, and arctic climates. This variation in reproductive timing will be favorable in times of climate change, as organisms with high plasticity are more likely to adjust to new environmental conditions.
The Eurasian lynx (Lynx lynx) covers three of the four main climate regions of the world, making it an ideal species to explore reproductive phenology in a carnivore. Mean birth date was May 28 (April 23 to July 1), but was ~10 days later in northern Europe than in central and southern Europe. Timing of birth was delayed by colder May temperatures, and we argue that lynx give birth later when exposed to colder spring temperatures and have more synchronized births when the window of favorable conditions for raising kittens is shorter.
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