Empirical evidence shows that brood sex ratios can be influenced by environmental factors and reproductive success-related parental traits. The Trivers-Willard hypothesis (TWH) predicts conditiondependent adjustment of offspring sex ratios and has been extended to suggest that females mated to more attractive males will bias offspring sex ratios towards sons, as sons that resemble their fathers could yield greater fitness returns through increased grandoffspring production. Although extensive research has explored the effect of male attractiveness on sex allocation, its interplay with environmental conditions is often overlooked. This study examines how brood sex ratios respond to both male attractiveness and annual rearing conditions (ARC; proxied by annual breeding success) within the framework of the TWH. Using long-term data from 2759 molecularly sexed nestlings of pied flycatchers, Ficedula hypoleuca, ringed between 1997 and 2018 (with 643 brood sex ratios determined from eight breeding seasons between 1997 and 2011) and by tracking lifetime fledgling production through the 2023 breeding season, we found support for sex ratio adjustment as predicted by the TWH. Male attractiveness and ARC positively affected the proportion of males in the broods. These associations were partially context-dependent, with each factor becoming influential only when the other was unfavourable. Analyses of nestling mortality before genetic sexing at day 13 after hatching showed that nestling mortality was more frequent in female-biased broods, decreased with favourable rearing conditions and increased with male attractiveness. Importantly, excluding broods with early nestling mortality left the main sex ratio conclusions unchanged. In addition, we did not find statistical evidence for an association between male attractiveness or ARC and offspring's lifetime reproductive success. Our findings suggest that sex allocation is influenced by poor rearing conditions, sexually selected traits and their interplay. Further research is needed to confirm this relationship and to clarify the fitness consequences for sons and daughters. (c) 2026 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Quantum sensing is a rapidly growing branch of research within the area of quantum science and technology offering key resources, beyond classical ones, with potential for commercialization of novel (quantum) sensors. The exploitation of quantum resources offered by photons can boost the performance of quantum sensors for innovative and challenging applications. In this paper, we build on the idea that quantum ghost spectroscopy (QGS), i.e. the counterpart in the frequency domain of quantum ghost imaging (QGI), can target specific applications in the detection of possible threats. This is implemented by exploiting the opportunities offered by quantum optics, i.e. the generation of photon pairs characterized by spectral correlations. We will discuss our main results obtained with pure QGS experiments showing that it is possible to assess the presence of a target dealing with a low resources measurement. The time-frequency domain reveals a huge potential for several applications, and frequency correlations represent a versatile tool that can be exploited to enable the spectral analysis of objects where a direct measurement would not be feasible (e.g. due to security). The use of non-degenerate sources of correlated photons allowed to reveal spectral features in the near-infrared wavelengths employing the usual detectors for the visible region, showing the effectiveness of this technique.

The major histocompatibility complex (MHC) plays a critical role in the immune response against pathogens. Its high polymorphism is thought to be mainly the consequence of host-pathogen co-evolution, but elucidating the mechanism(s) driving MHC evolution remains challenging for natural populations. We investigated the diversity of MHC class II genes in a wild population of pied flycatchers Ficedula hypoleuca and tested its associations with two key components of individual fitness: lifetime reproductive success and survival. Among 180 breeding adults in our study population, we found 182 unique MHC class II exon 2 alleles. The alleles showed a strong signal of positive selection and grouped into nine functional supertypes based on physicochemical properties at the inferred antigen-binding sites. Three supertypes were found in > 98% of the sampled individuals, indicating that they are nearly fixed in the population. We found no rare supertypes in the population, as all supertypes were present in > 70% of individuals. Three supertypes were related to different components of individual fitness: two were associated with lower offspring production over time, while the third was positively associated with survival. Overall, the substantial allelic and functional diversity and the relationship between specific supertypes and fitness are in accordance with the notion that balancing selection maintains MHC class II diversity in the study population, possibly with fluctuating selection as the underlying mechanism. The absence of rare supertypes in the population suggests that the balancing selection is not driven by rare-allele advantage.

Despite increased conservation efforts, the European rabbit (Oryctolagus cuniculus), a keystone species in the Iberian Peninsula, continues declining due to habitat degradation and viral diseases. Following the 2011 outbreak of Rabbit Hemorrhagic Disease virus GI.2, the species was listed as Endangered by the International Union for Conservation of Nature (IUCN). While rabbit declines in natural habitats are well documented, no research has separately analyzed population trends between areas where rabbits are managed as agricultural pests (rabbit emergency hunting areas: REHAs) and other areas, mostly natural (non-REHAs). Additionally, recent findings suggest divergent trends between the two rabbit subspecies, O. c. cuniculus and O. c. algirus, which coexist only in a limited area where their ranges overlap, with the latter possibly experiencing a more widespread decline. Here, we analyzed hunting yield data from 6,000 hunting estates in Castilla-La Mancha (central Spain), spanning 2009 to 2022. Using linear mixed models (GLMMs), we found significant differences in rabbit hunting yields and trends between REHAs and non-REHAs, as well as between the subspecies’ distribution areas. Densities of hunted rabbits were higher in REHAs, while the lowest hunting yields were observed in O. c. algirus areas, consistent with studies suggesting its lower abundance. Population trends in non-REHAs showed declines for both subspecies, with a less pronounced decrease in O. c. cuniculus areas and near stability in REHAs inhabited by this subspecies. These findings reveal contrasting trends between subspecies and management areas, emphasizing the need for targeted management strategies tailored to agricultural and natural habitats and the specific ecological requirements of each subspecies.

Domestic dogs, Canis familiaris, wandering into natural habitats poses a grave threat to wildlife, increasing predation pressure and disease risk and disrupting the ecological balance within ecosystems. This study examines the presence of dogs in a European Protected Area (PA), Doñana National Park (SW Spain), where their access is strictly restricted, and explores how dog presence relates to potential access points. We utilised classifications provided by citizen science and artificial intelligence, subsequently validated by experts, to detect dogs within 5200,000 photos taken by 60 camera traps randomly deployed across the PA from October 2020 to January 2024. We discovered 33 dogs, primarily in groups of 2–5 individuals, recorded across 31 detection events at 22 camera locations. Dogs were detected ranging from 10 to 42 km2 (Minimum Convex Polygon) within the PA. The detection probability of dogs increased by 0.22 log odds per kilometre closer to a village (corresponding to an increase from 0.5 to approximately 0.55) bordering the PA and exceeded 0.9 near it. Our data revealed three types of dogs wandering within the PA: dogs accompanying poachers, free-roaming dogs living in nearby human settlements, and stray dogs, most likely relying on the PA resources. Urgent actions are needed in Doñana as dogs pose severe threats to endangered species like the Iberian lynx Lynx pardinus (six adult female lynx documented killed by dogs). We recommend raising awareness among local authorities of free-roaming dogs, particularly in settlements close to PAs, where their presence should be banned. Regularly monitoring dog presence within PAs is crucial to prevent invasions and their associated impacts. Our findings underscore the importance of using camera traps and integrating artificial intelligence with citizen science to monitor invasive species effectively.

Quantum interference is a central resource in many quantum-enhanced tasks, from computation to communication. While usually occurring between identical photons, it can also be enabled by performing projective measurements that render the photons indistinguishable, a process known as quantum erasing. Structured light forms another hallmark of photonics, achieved by manipulating the degrees of freedom of light, and enables a multitude of applications in both classical and quantum regimes. By combining these ideas, we design and experimentally demonstrate a simple and robust scheme that tailors quantum interference to engineer photonic states with spatially structured coalescence along the transverse profile, a type of quantum mode with no classical counterpart. To achieve this, we locally tune the distinguishability of a photon pair by spatially structuring the polarization and creating a structured quantum eraser. We believe that these spatially engineered multiphoton quantum states may be of significance in fields such as quantum metrology, microscopy, and communication.

Although dispersal is a key driver of population dynamics and species distributions, we still know little about how it affects the dynamics of endangered and restricted-range species. Density-dependent effects on dispersal in particular may be critical for the range expansion of recovering populations. After 1981, when the last 7 wild individuals of Crested Ibis (Nipponia nippon) were discovered in China, the species remained confined to a single location ("original nesting area") until 2000 (< 24 breeding pairs). Then, the breeding population began a significant spatial and numerical expansion toward new breeding sites ("secondary nesting areas"). Our analyses of long-term (1993-2017) individual resighting data (n = 193) found that natal dispersal was common (similar to 77.2%), whereas breeding dispersal was rare (similar to 2.1%). Breeding density was negatively related to productivity, and natal dispersal was more likely toward low-density areas. The Weibull distribution provided the best fit to the observed dispersal distances, indicating the presence of long-distance natal dispersers. Although we cannot rule out the effect of dispersal mechanisms inherent in the species regardless of density, our findings suggest that the probability of natal dispersal is density-dependent, implying a role for intraspecific competition in the Crested Ibis spreading in the region. We expect the Crested Ibis to spread throughout the region if conservation programs can identify and protect potential reintroduction areas at a large spatial scale to allow dispersing Crested Ibis to settle into new and low-density breeding areas.

The outbreaks of two strains of rabbit haemorrhagic disease (RHD) (GI.1 and GI.2) in the Iberian Peninsula have caused substantial economic losses in commercial rabbitries and have affected the conservation of rabbit-sensitive predators due to the dramatic decline of their natural populations. However, the assessment of the impact of both RHD strains on wild rabbit populations has been limited to a few small-scale studies. Little is known about the overall impact within its native range. In this study, we described and compared the effects of GI.1 and GI.2 countrywide by using time series of hunting bag data widely available across the country and compared their trend during the first eight years after the first outbreak of GI.1 (i.e., 1998) and GI.2 (i.e., 2011), respectively. We used Gaussian generalised additive models (GAM) with the number of hunted rabbits as the response variable and year as the predictor to evaluate the non-linear temporal dynamics of the population at the national and regional community levels. The first GI.1 caused a population decline of around 53%, affecting most Spanish regional communities where the disease occurred. The positive trend observed after GI.1 in Spain ended with the initial outbreak of GI.2, which did not appear to cause a national population decline. In contrast, we found significant variability in the rabbit population trend among regional communities, where some increased, and others decreased. Such a disparity is unlikely to be explained by a single factor; rather, it appears to result from several factors, such as climatic conditions, host resistance improvement, virulence attenuation, or population density. Our study suggests that a national comprehensive hunting bag series could aid in elucidating the differences in the impact of emerging diseases on a large scale. Future research should focus on national longitudinal serological studies to shed light on the immunological status of rabbit populations in different regions to better understand the evolution of RHD strains and the resistance gained by the wild populations.

We present a device that exploits spatial and spectral correlations in parametric downconversion at once. By using a ghost imaging arrangement, we have been able to reconstruct remotely the frequency profile of a composite system. The presence of distinct spectral regions is corroborated by a model-independent statistical analysis that constitutes an intriguing possibility also in the low count regime.

Social monogamy is the most common social mating system in birds. However, the persistence of pair bonds between breeding seasons varies among species, populations and individuals. Understanding fitness causes and consequences of mate change is critical for understanding population dynamics and the evolution of social monogamy. We used 12 years of data from Scopoli's shearwater breeding population to estimate mate change probabilities and test whether they affect the probabilities of (1) skipping breeding, (2) apparent survival and (3) breeding success. Widowing was the most common cause of mate change, with more males changing mates at least once in their lives than females. Females' probability of skipping a breeding season increased significantly just before pairing with a new partner. Also, we found that females' apparent survival, but not males', might increase after mate change. A possible explanation is that a longer adult life expectancy of females after mate change could at least partially offset the cost of skipping breeding. We found no relation between mate change and breeding success. Our study suggests that the costs and benefits of mate fidelity may be sex specific in this species. Future research on this topic should focus on the effects of mate change on each sex's lifetime reproductive success, which we could not address specifically in this study. Future studies will hopefully be able to delve deeper into how mate change, caused by divorce or widowhood, shifts the balance of reproduction or survival, determining lifetime reproductive success.

The European population of Eurasian Curlew Numenius arquata arquata, a near‐threatened wader subspecies, has undergone pronounced population declines over the past 30 years. To assess the demography and viability of its global population, we surveyed studies quantifying demographic rates (productivity and survival) and complemented this review with new estimates of survival probability at the flyway scale. Then, using a demographic model, we estimated population growth rates while accounting for the range of variation of demographic parameters, and compared these estimates (expected based on demographic rates) with those observed based on population censuses. Both observed and expected average growth rates were negative but the observed rates were higher than estimates from demographic models (λ = 0.98–0.99 compared with 0.85–0.95). This discrepancy implies that there is geographical variation in the demography of different populations that is not fully covered by current demographic data, namely unstudied regions with higher productivity. According to our calculations, at the flyway scale, productivity is currently c. 0.57 fledglings per pair per year, higher than the average reported productivity of 0.29, but lower than the 0.68 needed to achieve a stable global population size (λ = 1). Adult survival, estimated at 0.90, was the most sensitive parameter determining population growth rates, but the low productivity levels over the last few decades seems to be the most probable cause of population declines. The negative population growth rates require immediate conservation actions to preserve adult survival and increase the extremely low productivity in western and northern European populations to values above 0.68 fledglings per pair per year. We hope our synthesis on the demographic status of Curlew in Europe will encourage the collection of more demographic data and allow concrete management goals at the flyway scale to be established in order to recover the global population of this iconic species.

Mating system theory predicts that social polygyny—when one male forms pair bonds with two females—may evolve by female choice in species with biparental care. Females will accept a polygynous male if the benefit of mating with a male providing high-quality genes or rearing resources outweighs the cost of sharing mate assistance in parental care. Based on this rationale, we hypothesise that the population frequency of social polygyny (FSP) varies due to changes in mate sharing costs caused by changing environmental conditions. We predicted that: (1) polygamous females (i.e. mated with a polygynous male) pay a survival cost compared to monogamous females; (2) FSP would be higher in years with better rearing conditions and (3) the difference in survival rates between monogamous and polygamous females would be small following years with higher FSP. We tested these predictions using regression and multistate analyses of capture-recapture data of pied flycatchers, Ficedula hypoleuca , in central Spain collected over 26 years (1990–2016). Monogamous females had a higher mean survival rate than polygamous females (prediction 1), but there was no difference in survival between polygynous and monogamous males. In addition, FSP was positively associated with annual reproductive success (a proxy of the quality of rearing conditions—prediction 2). Finally, following years with high FSP, the survival of polygamous females was similar to that of monogamous females (prediction 3), while the chance of breeding in a polygamous state for 2 years in a row increased for both males and females. Our findings suggest that fluctuating environmental conditions may be a necessary but neglected aspect of understanding social polygyny mechanisms.

BACKGROUND:Fast-spreading diseases affecting wildlife populations threaten biodiversity. Two caliciviruses, Lagovirus europaeus/GI.1 and Lagovirus europaeus/GI.2, caused rabbit haemorrhagic disease virus (RHDV) in wild rabbits. Despite having different characteristics, these variants spread quickly, posing a threat to wild rabbit populations.METHODS:In this study, we conducted a thorough review of the scientific literature and reports of international organisations of first detections of both variants of RHDV in the Euro-Mediterranean region. We concentrated on this area to avoid bias due to intentional human introductions.RESULTS:The estimated mean spread rate of GI.2 was higher than that of GI.1 (GI.2: 479 km/year, range: 47-7346; GI.1: 330 km/year, 37-6248). These differences were not statistically significant. This lack of difference may be due to the interactions between each variant's virulence characteristics. Humans may have a dominant effect on their spread. Potential limitations associated with the observational process could have hindered our ability to identify statistical differences.CONCLUSIONS:The lack of difference in the spread patterns of the two variants could be due to a biological cause, human facilitation or a lack of statistical power. Adapting protocols to detect diseases in wildlife using homogeneous criteria will be indispensable in the coming years.

In spite of the wide use of Raman spectroscopy for chemical analysis in different fields, not any automated identification of Raman spectra is universally adopted. However, the interest in this field is witnessed by the large number of papers published in the last decades. The problem of Raman-spectra classification becomes particularly challenging when low irradiation is requested, either for safety reasons or to avoid target photodegradation. This often leads to spectra characterized by a low signal-to-noise ratio, where methods based on correlation usually fail. For this reason, a method based on peak identification through FMFs is presented, discussed and validated over a large set of samples. In particular, a Monte Carlo simulation has been employed to determine the best parameters of the fuzzy membership functions based on the analysis of performances of the classification procedure. The ROC curves have been analyzed, and AUC and best accuracy are employed as key parameters to evaluate the classification performances on different amounts of ammonium nitrate (from 300 to 1500 μg) and different laser exposure levels (from 3.1 to 250 mJ/cm2).

Homonota taragui is an endemic gecko of the northeast of Argentina. We estimate demographic parameters: number of individuals by populations, sex and ontogenetic stage; sexual dimorphism; survival of this species; and describe the use of microhabitat and movement patterns. We measured 11 morphological variables, determined the sex and marked individually. We found bigger head width in males. Some factors contribute to the vulnerability of this species such as its constrained geographical distribution, use of the specific microhabitat and the isolation of their populations. We highlight demography studies as an essential data source for management and conservation of critically endangered species.

Ecogeographical rules, such as Bergmann’s and Allen’s rules, describe empirical observations of latitudinal patterns in homeotherm morphology. Bergmann’s rule predicts that populations within a species or closely related species have smaller body sizes in warmer climates, whereas Allen’s rule predicts a greater proportion of limbs and appendages relative to body size. Bergman’s and Allen’s principles are challenging to test, given the wide range of factors that influence animal morphology, including climate [ 1. Mayr E. Geographical character gradients and climatic adaptation. Evolution. 1956; 10: 105-108 Crossref Google Scholar , 2. Olalla-Tárraga M.Á. 'Nullius in Bergmann' or the pluralistic approach to ecogeographical rules: a reply to Watt et al. (2010). Oikos. 2011; 120: 1441-1444 Crossref Scopus (56) Google Scholar , 3. Watt C. et al. Bergmann’s rule; a concept cluster?. Oikos. 2010; 119: 89-100 Crossref Scopus (167) Google Scholar , 4. Scholander P.F. Evolution of climatic adaptation in homeotherms. Evolution. 1955; 9: 15-26 Crossref Google Scholar ].

• Biological invasions of animals and pathogens threat biodiversity. • Early detection of biological invasions is critical for effective management. • Artificial intelligence enables massive processing of camera-trapping photographs. • Combining AI, camera traps, and remote sensing can be used for real-time detection.

Why females engage in social polygyny remains an unresolved question in species where the resources provided by males maximize female fitness. In these systems, the ability of males to access several females, as well as the willingness of females to mate with an already mated male, and the benefits of this choice, may be constrained by the socio-ecological factors experienced at the local scale. Here, we used a 19-year dataset from an individual-monitored population of pied flycatchers ( Ficedula hypoleuca ) to establish local networks of breeding pairs. Then, we examined whether the probability of becoming socially polygynous and of mating with an already mated male (thus becoming a secondary female) is influenced by morphological and sexual traits as proxies of individual quality relative to the neighbours. We also evaluated whether social polygyny is adaptive for females by examining the effect of females’ mating status (polygamously-mated vs monogamously-mated) on direct (number of recruits in a given season) and indirect (lifetime number of fledglings produced by these recruits) fitness benefits. The phenotypic quality of individuals, by influencing their breeding asynchrony relative to their neighbours, mediated the probability of being involved in a polygynous event. Individuals in middle-age (2–3 years), with large wings and, in the case of males, with conspicuous sexual traits, started to breed earlier than their neighbours. By breeding locally early, males increased their chances of becoming polygynous, while females reduced their chances of mating with an already mated male. Our results suggest that secondary females may compensate the fitness costs, if any, of sharing a mate, since their number of descendants did not differ from monogamous females. We emphasize the need of accounting for local breeding settings (ecological, social, spatial, and temporal) and the phenotypic composition of neighbours to understand individual mating decisions.