► The Azores hold the world’s largest Cory’s shearwater (
Calonectris diomedea) population. ► Population dynamics there remain unknown despite the existence of threats. ► Although we found a high ...adult survival rate, we cannot rule out a decline of the Azorean population. ► The causes of this potential decline are threats to the young on land and possible low juvenile survival at sea. ► We propose a set of measures aimed at reducing chick and fledgling mortality.
Cory’s shearwater (
Calonectris diomedea) is a procellariiform seabird which breeds in the Mediterranean and the north-eastern subtropical Atlantic, and which is considered “Vulnerable” in Europe due to recent declines at some localities. In the Azores archipelago (Atlantic), the introduction of mammalian predators by man has led to petrels being extirpated from the main islands, except for Cory’s shearwater. Currently, the Azorean population of Cory’s shearwaters represents 65% of the species’ world population. However, its dynamics remains unknown, although: (1) numbers might have declined by 43% between 1996 and 2001, (2) on the main islands, the young suffer mortality from introduced mammals, poachers, and urban lights upon fledging, and (3) at sea, the level of fishery mortality remains unknown.
To fill this gap, we conducted a 7-year demographic survey on a mammal-free islet in the Azores to determine adult survival rate using capture-mark-recapture of the breeders and to estimate fecundity. We also assessed urban mortality using the data from the rescue campaigns annually conducted in the archipelago. Urban mortality concerned about 6% of fledglings, but its importance greatly varied among islands. When rescue campaigns occur, the rate might drop below 0.5%. Overall, our simulations concerning the next 100
years do not allow excluding a decrease in Cory’s shearwater numbers in the Azores without rescue campaigns (by 87% under the least favourable scenario). Rescue campaigns should only slow down the decline unless, simultaneously, lower competition for nests compared to Vila islet allows adults to breed almost every year on the main islands and juvenile survival exceeds a threshold value. Since adult survival rate was high (>0.93), an eventual decline of the Azorean population of Cory’s shearwaters would probably not result from fishery mortality of adults, but rather from poor fledgling productivity and perhaps also from low survival during the first year at sea.
Obtaining estimates of animal population density is a key step in providing sound conservation and management strategies for wildlife. For many large carnivores however, estimating density is ...difficult because these species are elusive and wide‐ranging. Here, we focus on providing the first density estimates of the Eurasian lynx (Lynx lynx) in the French Jura and Vosges mountains. We sampled a total of 413 camera trapping sites (with two cameras per site) between January 2011 and April 2016 in seven study areas across seven counties of the French Jura and Vosges mountains. We obtained 592 lynx detections over 19,035 trap days in the Jura mountains and 0 detection over 6,804 trap days in the Vosges mountains. Based on coat patterns, we identified a total number of 92 unique individuals from photographs, including 16 females, 13 males, and 63 individuals of unknown sex. Using spatial capture–recapture (SCR) models, we estimated abundance in the study areas between 5 (SE = 0.1) and 29 (0.2) lynx and density between 0.24 (SE = 0.02) and 0.91 (SE = 0.03) lynx per 100 km2. We also provide a comparison with nonspatial density estimates and discuss the observed discrepancies. Our study is yet another example of the advantage of combining SCR methods and noninvasive sampling techniques to estimate density for elusive and wide‐ranging species, like large carnivores. While the estimated densities in the French Jura mountains are comparable to other lynx populations in Europe, the fact that we detected no lynx in the Vosges mountains is alarming. Connectivity should be encouraged between the French Jura mountains, the Vosges mountains, and the Palatinate Forest in Germany where a reintroduction program is currently ongoing. Our density estimates will help in setting a baseline conservation status for the lynx population in France.
We provide the first density estimates for the Eurasian lynx (Lynx lynx) in the French Jura and Vosges mountains. Our study is yet another example of the advantage of combining spatial capture–recapture methods and noninvasive sampling techniques to estimate density for elusive and wide‐ranging species like large carnivores. While the estimated densities in the French Jura mountains are comparable to other lynx populations in Europe, the situation in the Vosges mountains is alarming. Our density estimates will help in setting a baseline conservation status for the lynx population in France.
Few empirical studies have described social‐ecological systems (SESs) in transition. Some studies focused on external drivers that impact the SES and communities' responses to adapt to changes, ...including economic, land and conservation policies. Others have considered the effect of social and cultural changes on communities' capacity to sustain their activities. While sociocultural changes are increasingly common through globalization and world‐wide economic development, there is an urgent need to better understand and document how these changes affect individual and community agency to adapt or transform a system that is facing a combination of powerful internal and external forces.
The human–Asian elephant relationship appears particularly illustrative of a complex SES because of the dual status of the elephant being wild or under human care, and the entanglement of ecological, cultural, social and economic dimensions. The ongoing and rapid political, socio‐economic and environmental changes occurring in Laos for the last decades have strongly affected this relationship.
We conducted an ethnological survey to assess how the SES has evolved in Laos and its consequences for human‐wild‐captive elephant interactions and elephant handling practices. We show that in the 1990s, the SES was based on the principles of common access to natural resources and social control over nature and spirits, and led to a form of elephant handling with close interactions between captive and wild elephants. Husbandry practices then could be likened to pastoralism as a mode of production associated with a mode of relation close to seasonal freedom.
Since the turn of the present century, the commodification of nature and of increasingly divided access to natural resources led eventually to the segregation of wild elephants and captivity of their working conspecifics. With the intensification of workload, owners switched to a ranching‐like economy, based on the accumulation of monetary capital from the employment of elephants in logging or tourism.
We discuss how the combination of external drivers, such as economic liberalization, land and conservation policies, and internal drivers linked to sociocultural changes could affect a SES in transition, leading to a fading interest of the new generation in their family heritage.
A free Plain Language Summary can be found within the Supporting Information of this article.
Résumé
Peu d'études empiriques ont décrit les systèmes sociaux‐écologiques (SSE) en transition. Certaines études se sont concentrées sur les facteurs externes qui ont un impact sur les SSE et sur les réponses des communautés pour s'adapter aux changements, notamment les politiques économiques, foncières et de conservation. D'autres ont considéré l'effet des changements sociaux et culturels sur la capacité des communautés à maintenir leurs activités. Alors que les changements socioculturels sont de plus en plus courants du fait de la mondialisation et du développement économique mondial, il est urgent de mieux comprendre et documenter la manière dont ces changements affectent la capacité des individus et des communautés à s'adapter ou transformer un système qui fait face à une combinaison de puissantes forces internes et externes.
La relation entre l'homme et l'éléphant d'Asie est un bon exemple d'un SSE complexe en raison du double statut de l'éléphant, sauvage ou domestique, et la conjonction de multiples dimensions: écologiques, culturelles, sociales et économiques. Les changements politiques, socio‐économiques et environnementaux rapides survenus au Laos au cours des dernières décennies ont fortement affecté cette relation.
Nous avons mené une enquête ethnologique pour étudier comment le SSE a évolué au Laos et décrire les conséquences de ces évolutions sur les interactions entre l'humain, l'éléphant domestique et l'éléphant sauvage, ainsi que les changements des pratiques d'élevage. Nous montrons que dans les années 1990, le SSE était fondé sur les principes d'accès commun aux ressources naturelles et de contrôle social sur la nature et les esprits. Ce SSE a conduit à une forme d'élevage des éléphants avec des interactions étroites entre les éléphants domestiques et sauvages. Les pratiques d'élevage pouvaient alors être assimilées au pastoralisme en tant que mode de production, associé à un mode de relation proche de la liberté saisonnière.
Depuis le début du siècle, la marchandisation de la nature et l'accès de plus en plus divisé aux ressources naturelles ont finalement conduit à la ségrégation des éléphants sauvages et à la captivité de leurs congénères de travail. Avec l'intensification de la charge de travail, les propriétaires ont adopté une économie de type ranching, basée sur l'accumulation de capital monétaire provenant de l'emploi des éléphants dans l'exploitation forestière ou le tourisme.
Nous discutons de la manière dont la combinaison de facteurs externes tels que la libéralisation économique, les politiques foncières et de conservation, et de facteurs internes liés aux changements socioculturels peuvent affecter un SSE en transition, conduisant à une perte d'intérêt de la nouvelle génération pour son héritage familial.
A free Plain Language Summary can be found within the Supporting Information of this article
Summary
Under increasing environmental and financial constraints, ecologists are faced with making decisions about dynamic and uncertain biological systems. To do so, stochastic dynamic programming ...(SDP) is the most relevant tool for determining an optimal sequence of decisions over time.
Despite an increasing number of applications in ecology, SDP still suffers from a lack of widespread understanding. The required mathematical and programming knowledge as well as the absence of introductory material provide plausible explanations for this.
Here, we fill this gap by explaining the main concepts of SDP and providing useful guidelines to implement this technique, including R code.
We illustrate each step of SDP required to derive an optimal strategy using a wildlife management problem of the French wolf population.
Stochastic dynamic programming is a powerful technique to make decisions in presence of uncertainty about biological stochastic systems changing through time. We hope this review will provide an entry point into the technical literature about SDP and will improve its application in ecology.
Species-area relationships (SARs) are fundamental to the study of key and high-profile issues in conservation biology and are particularly widely used in establishing the broad patterns of ...biodiversity that underpin approaches to determining priority areas for biological conservation. Classically, the SAR has been argued in general to conform to a power-law relationship, and this form has been widely assumed in most applications in the field of conservation biology. Here, using nonlinear regressions within an information theoretical model selection framework, we included uncertainty regarding both model selection and parameter estimation in SAR modeling and conducted a global-scale analysis of the form of SARs for vascular plants and major vertebrate groups across 792 terrestrial ecoregions representing almost 97% of Earth's inhabited land. The results revealed a high level of uncertainty in model selection across biomes and taxa, and that the power-law model is clearly the most appropriate in only a minority of cases. Incorporating this uncertainty into a hotspots analysis using multimodel SARs led to the identification of a dramatically different set of global richness hotspots than when the power-law SAR was assumed. Our findings suggest that the results of analyses that assume a power-law model may be at severe odds with real ecological patterns, raising significant concerns for conservation priority-setting schemes and biogeographical studies.
Traffic hijacking over the Internet has become a frequent incident over the last two decades. From minor inconveniences for casual users to massive leaks of governmental data, these events cover an ...unprecedently large spectrum. Many hijackings are presumed to be caused by unfortunate routing mistakes, but a well-organized attacker could set up a long-term stealthy relay, accessing critical traffic metadata, despite suitable encryption schemes. While many studies focus on the mitigation of known attacks, we choose to design a complete detection method regardless of the attacker’s strategy. We propose a two-party cryptographic protocol for detecting traffic hijacking over the Internet. Our proposal relies on a distance-bounding mechanism that performs interactive authentication with a “Challenge–Response” exchange, and measures the round-trip time of packets to decide whether an attack is ongoing. Our construction is supported by worldwide experiments on communication time between multiple nodes, allowing us to both demonstrate its applicability and evaluate its performance. Over the course of this paper, we demonstrate our protocol to be efficient—itrequires only two cryptographic operations per execution inducing negligible workload for users and very few loss of throughput, scalable—no software updates are required for intermediate network nodes, routing protocol independent—this means that any future update of the route selection process will not induce changes on our scheme, and network friendly—the added volume of transiting data is only about 1.5%.
To successfully perform their long‐distance migrations, migratory birds require sites along their migratory routes to rest and refuel. Monitoring the use of so‐called stopover and staging sites ...provides insights into (a) the timing of migration and (b) the importance of a site for migratory bird populations. A recently developed Bayesian superpopulation model that integrates mark–recapture data and ring density data enabled the estimation of stopover timing, duration, and population size. Yet, this model did not account for heterogeneity in encounter (p) and staying (ϕ) probabilities.
Here we extended the integrated superpopulation model by implementing finite mixtures to account for heterogeneity in p and ϕ. We used simulations and real data (from 2009–2016) on red knots Calidris canutus, mostly of the subspecies piersmai, staging in Bohai Bay, China, during spring migration to (a) show the importance of accounting for heterogeneity in encounter and staying probabilities to get unbiased estimates of stopover timing, duration, and numbers of migratory birds at staging sites and (b) get accurate stopover parameter estimates for a migratory bird species at a key staging site that is threatened by habitat destruction.
Our simulations confirmed that heterogeneity in p affected stopover parameter estimates more than heterogeneity in ϕ, especially when most birds had low p. Bias was particularly severe when most birds had both low ϕ and p. Bias was largest for population size, intermediate for stopover duration and negligible for stopover timing.
A total of 50,000–100,000 red knots were estimated to annually stop for 5–9 days in Bohai Bay between 10 and 30 May. This shows the key importance of this staging site for this declining species. There were no clear changes in stopover parameters over time, although stopover population size was substantially lower in 2016 than in preceding years.
Our study shows the importance of accounting for heterogeneity in both encounter and staying probabilities for accurately estimating stopover duration and population size and provides an appropriate modeling framework.
In this paper, we developed a statistical model that accounts for heterogeneity in encounter and staying probability to estimate stopover duration, timing, and population size. We show that ignoring heterogeneity can lead to severe biases in stopover population size and stopover duration. The model is then applied to red knots staging in Bohai Bay, China, and estimates that between 10 and 30 May, 50,000–100,000 red knots use this area for 5–9 days during spring migration.
Reproductive senescence is ubiquitous in mammals. However, patterns of senescence vary across reproductive traits, even within populations, perhaps because of differences in selection pressures, ...physiological constraints, and responses to environmental conditions. We investigated reproductive senescence in wild female polar bears (
Ursus maritimus
), using 31 years of capture-recapture data from the Svalbard area. We studied the influence of environmental conditions on age-specific litter production and litter size using generalized linear mixed models. Further, using a capture-recapture model that handles the dependency between vital rates of individuals belonging to the same family unit, we assessed maternal-age-related changes in first year cub and litter survival. We provide clear evidence for reproductive senescence in female polar bears. Litter production and litter size peaked in middle-aged females and declined sharply afterward. By contrast cub and litter survival did not decline after prime age. We found no evidence of terminal investment. The reproductive output of all females was affected by sea-ice conditions during the previous year and the Arctic Oscillation, with some effects differing greatly between age groups. Old females were affected the most by environmental conditions. Our results suggest that the decline in reproductive output is a combination of fertility and body-condition senescence, with a weak contribution of maternal-effect senescence, possibly due to benefits of experience. Further, as predicted by evolutionary theory, senescence appears to be a consequence of failures in early stages of the reproductive cycle rather than in late stages, and environmental variation affected old females more than prime-aged females. Our study emphasizes the need to study several reproductive traits and account for environmental variation when investigating reproductive senescence. Differences in senescence patterns across reproductive traits should be interpreted in light of evolutionary theory and while considering underlying physiological drivers.
Seabirds are affected by changes in the marine ecosystem. The influence of climatic factors on marine food webs can be reflected in long-term seabird population changes. We modelled the survival and ...recruitment of the Mediterranean storm petrel (Hydrobates pelagicus melitensis) using a 21-year mark-recapture dataset involving almost 5000 birds. We demonstrated a strong influence of prebreeding climatic conditions on recruitment age and of rainfall and breeding period conditions on juvenile survival. The results suggest that the juvenile survival rate of the Mediterranean subspecies may not be negatively affected by the predicted features of climate change, i.e., warmer summers and lower rainfall. Based on considerations of winter conditions in different parts of the Mediterranean, we were able to draw inferences about the wintering areas of the species for the first time.
Whether different sources of mortality are additive, compensatory, or depensatory is a key question in population biology. A way to test for additivity is to calculate the correlation between ...cause-specific mortality rates obtained from marked animals. However, existing methods to estimate this correlation raise several methodological issues. One difficulty is the existence of an intrinsic bias in the correlation parameter. Although this bias can be formally expressed, it requires knowledge about natural survival without any competing mortality source, which is difficult to assess in most cases. Another difficulty lies in estimating the true process correlation while properly accounting for sampling variation. Using a Bayesian approach, we developed a state-space model to assess the correlation between two competing sources of mortality. By distinguishing the mortality process from its observation through dead recoveries and live recaptures, we estimated the process correlation. To correct for the intrinsic bias, we incorporated experts' opinions on natural survival. We illustrated our approach using data on a hunted population of wild boars. Mortalities were not additive and natural mortality increased with hunting mortality likely as a consequence of non-controlled mortality by crippling loss. Our method opens perspectives for wildlife management and for the conservation of endangered species.
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