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.
Sanctioning to extinction in Iran Khalatbari, L; Brito, J C; Ghoddousi, A ...
Science (American Association for the Advancement of Science),
12/2018, Letnik:
362, Številka:
6420
Journal Article
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.
The red fox (Vulpes vulpes) is one of the best‐documented examples of a species that has successfully occupied cities and their suburbs during the last century. The city of Zurich (Switzerland) was ...colonized by red foxes 15 years ago and the number of recorded individuals has increased steadily since then. Here, we assessed the hypothesis that the fox population within the city of Zurich is isolated from adjacent rural fox populations against the alternative hypothesis that urban habitat acts as a constant sink for rural dispersers. We examined 11 microsatellite loci in 128 foxes from two urban areas, separated by the main river crossing the city, and three adjacent rural areas from the region of Zurich. Mean observed heterozygosity across individuals and the number of detected alleles were lower for foxes collected within the city as compared with their rural conspecifics. Genetic differentiation was significantly lower between rural than between rural and urban populations, and highest value of pairwise FST was recorded between the two urban areas. Our results indicate that the two urban areas were independently founded by a small number of individuals from adjacent rural areas resulting in genetic drift and genetic differentiation between rural and urban fox populations. Population admixture and immigration analysis revealed that urban–rural gene flow was higher than expected from FST statistics. In the five to seven generations since colonization, fox density has dramatically increased. Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation over time.
The brown bear
Ursus arctos, wolf
Canis lupus, and Eurasian lynx
Lynx lynx vanished during the 18th and 19th centuries from all regions of high human activity in Europe because of direct persecution ...and environmental changes. Bear, wolf, and lynx were vulnerable in different ways to deforestation and the destruction of wild ungulate populations. Analysing the ecological factors responsible for the fall of the large carnivores can help to prepare their recovery. The return of large predators into semi-natural areas such as the Alps is possible, as the forests have expanded, and the wild ungulate populations increased. Lynx reintroduction in the Alps started in the 1970s. Wolves returned to the south-western Alps from the central Italian population in the early 1990s. The brown bear is recolonising the Austrian Alps from Slovenia. However, the modern protective legislation is not backed by a cooperative attitude among the affected people. In rural areas, large carnivores are still regarded as unrestrained killers of wildlife and livestock. Ecological conditions and husbandry in the Alps have been altered substantially since the large carnivores were eradicated, and the potential for conflicts has diminished. But stockmen have lost any remaining tradition of coexistence with large predators, and sheep are again very abundant in the Swiss Alps. The return of the large predators will not be possible without changing the system of sheep-husbandry. The rural people are not yet willing to do so. They generally object to any change in their lifestyle induced from outside, and the large predators become a negative symbol for restrictive conservation measures considered to hinder economic development. Nature conservation, including the reintegration of large predators, must be integrated into rural development; local people must be much more involved in this process.
Summary
Subsequent to rabies vaccination campaigns, two well‐established methods for the determination of the proportion of vaccinated foxes – the detection of tetracycline (TC) in bones and the ...detection of virus neutralizing antibodies (VNA) in thoracic fluids – were used and compared. Special emphasis was given to the effect of a new method of bait distribution at the den, which is primarily targeted at young foxes. The overall proportion of vaccinated animals estimated by TC was 60% as compared to 50% by VNA. In young foxes overall, significantly lower proportions of vaccinated animals (58% by TC and 40% by VNA) than in adult foxes (75 and 59%) were estimated with both methods. Low proportions of vaccinated young animals were found after spring (39 and 18%), but also after autumn vaccination (56 and 35%). In contrast, after den vaccination the level of vaccination of young foxes reached that of adult foxes. The theoretical implication of the successful elimination of fox rabies in Switzerland in spite of a relatively low overall proportion of VNA‐positive animals is discussed.
Dispersal influences the dynamics and persistence of populations, the distribution and abundance of species, and gives the communities and ecosystems their characteristic texture in space and time. ...The Eurasian lynx Lynx lynx is a medium-sized solitary carnivore that has been re-introduced in central Europe and currently occurs in rather small populations, where dispersal is believed to play a prominent role for the recolonization of unsettled areas and persistence of subpopulations. Between 1988 and 2001 the spatio-temporal behaviour of sub-adult Eurasian lynx was studied in two re-introduced populations in Switzerland, based on 31 juveniles of which 24 were radio-tagged to find out which factors influence dispersal. Age at independence ranged from 8.1 to 10.7 months and did not differ between populations or sex. Independence began from January to the beginning of May with a peak in April. After independence, sub-adults stayed a few days in the maternal home range. Age at dispersal differed between the areas of origin and was possibly affected by sex and the presence of new progeny. Dispersers of both sexes established transient home ranges; however, only one male in the saturated population established a transient home range. Although only females took over the maternal home range, there was no significant sex bias in the proportion of individuals that dispersed in both populations. Successful dispersers settled in a territory at distances that differed between populations with effects of sex, but not condition. The mean dispersal distance in the high-density population was 25.9 km compared to 63.1 km in the low-density population. Dispersal distances in the high-density population – shorter than those reported in other Eurasian lynx studies but comparable to those observed in an Iberian lynx population – are limited by habitat restrictions hindering connections with a neighbouring population.
1. Although many reintroduction schemes for the Eurasian lynx Lynx lynx in Germany have been discussed, the implications of connectivity between suitable patches have not been assessed. 2. We ...introduce an individual-based, spatially explicit dispersal model to assess the probability of a dispersing animal reaching another suitable patch in the complex heterogeneous German landscape, with its dense transport system. The dispersal model was calibrated using telemetric data from the Swiss Jura and based on a map of potential lynx dispersal habitat. 3. Most suitable patches could be interconnected by movements of dispersing lynx within 10 years of reintroduction. However, when realistic levels of mortality risks on roads were applied, most patches become isolated except along the German-Czech border. Consequently, patch connectivity is limited not so much by the distribution of dispersal habitat but by the high mortality of dispersing lynx. Accordingly, rather than solely investing in habitat restoration, management efforts should try to reduce road mortality. 4. Synthesis and applications. Our approach illustrates how spatially explicit dispersal models can guide conservation efforts and reintroduction programmes even where data are scarce. Clear limits imposed by substantial road mortality will affect dispersing lynx as well as other large carnivores, unless offset by careful road-crossing management or by the careful selection of release points in reintroduction programmes.
The Iberian Lynx Conservation Breeding Program follows a multidisciplinary approach, integrated within the National Strategy for the Conservation of the Iberian lynx, which is carried out in ...cooperation with national, regional and international institutions. The main goals of the ex situ conservation programme are to: (1) maintain a genetically and demographically managed captive population; (2) create new Iberian lynx Lynx pardinus free-ranging populations through re-introduction. To achieve the first goal, the Conservation Breeding Program aims to maintain 85% of the genetic diversity presently found in the wild for the next 30 years. This requires developing and maintaining 60-70 Iberian lynx as breeding stock. Growth projections indicate that the ex situ programme should achieve such a population target by the year 2010. Once this goal is reached, re-introduction efforts could begin. Thus, current ex situ efforts focus on producing psychologically and physically sound captive-born individuals. To achieve this goal, we use management and research techniques that rely on multidisciplinary input and knowledge generated on species' life history, behaviour, nutrition, veterinary and health aspects, genetics, reproductive physiology, endocrinology and ecology. Particularly important is adapting our husbandry schemes based on research data to promote natural behaviours in captivity (hunting, territoriality, social interactions) and a stress-free environment that is conducive to natural reproduction.
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.
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