Sex identification and sex-specific behaviour are fundamental to fish reproductive ecology, yet their spatial variation along environmental gradients remains insufficiently understood. Adult brown trout (Salmo trutta) were sampled during the spawning period at 43 stream sites, each with at least three adult trout. We investigated sex ratios and morphometric characteristics (length, weight, and relative head length) of brown trout in relation to altitude, Strahler stream order, stream depth range, and mean stream depth across the Bohemian Forest (Central Europe). In total, 311 individuals were sexed. Males were significantly larger and had relatively longer heads than females. The proportion of males increased significantly with altitude, indicating a male-biased sex ratio in higher-elevation streams. Fish weight decreased with altitude along upstream-downstream gradients, suggesting that environmental conditions at higher elevations may constrain growth and body size. Measured temperature, Strahler stream order, and depth range had no detectable effect on brown trout sex ratios and morphometric characteristics. These results indicate sex-specific spatial segregation during the spawning period, likely driven by differences in migratory behaviour, competition, and energetic constraints, highlighting the role of natural environmental gradients in shaping salmonid population structure.
In the sand goby, Pomatoschistus minutus, males build nests and provide sole care for the eggs until hatching. We examined whether male and female courtship before spawning were associated with subsequent filial cannibalism by the male. Full and partial brood cannibalism showed distinct patterns. Broods that were later completely cannibalised were smaller, and spawning occurred later than in broods of males that received continued care. In contrast, brood size was not correlated with the extent of partial brood cannibalism. Instead, female courtship was negatively associated with partial brood cannibalism, whereas no similar relationship was found for male courtship. These results are consistent with full and partial brood cannibalism reflecting different biological mechanisms. Female courtship may provide information about future male care, influence subsequent male behaviour, or covary with brood or egg quality.
Non-volant small mammals in Afrotropical regions are a species-rich group of vertebrates, yet their diversity, distribution, and community structure remain insufficiently analysed. Here, we examined them at four locations in Afromontane tropical rainforests in Rwanda across two seasons, with a primary focus on Nyungwe National Park (NNP), comprising Nyungwe and Cyamudongo forests. Using standardised live-trapping and DNA analysis, applied systematically for the first time in this region, we documented 25 species, including 22 rodents, two shrews, and one golden mole. We confirmed most of the species previously recorded in NNP, but sequencing of the mitochondrial cytb gene and comparison with specimens from across Africa revealed one new species record, Lophuromys cinereus, for NNP and the country. The most abundant species were in the genera Praomys, Hybomys, Lophuromys, and Hylomyscus. Our study provides preliminary insights into the effects of season and patch size on non-volant small mammals in NNP: generally, seasonality did not show significant effects on community composition, whereas all species found in the small Cyamudongo fragment were also found in the main forest block of NNP. We highlight gaps worthy of further investigation, including clarification of the influence of biogeographic and ecological factors, e.g. altitudinal ranges, microhabitats, and edge effects, on non-volant small mammals. We also urge the inclusion of non-volant small mammals among target groups to understand the dynamics of Nyungwe ecosystems, demonstrate Afromontane diversity, and inform ecological monitoring and park management plans.
Amphibian populations worldwide are experiencing an unprecedented decline. More than 40% of species are at risk of extinction due to climate change, habitat loss and disease. The Near Eastern fire salamander (Salamandra infraimmaculata) is distributed across T & uuml;rkiye, Iran, Iraq, Syria, Israel and Lebanon, yet its demographic parameters remain poorly understood. Here, we present the first multi-year mark-recapture study (2022-2024) of population dynamics and life-history variation across six Anatolian populations. Our analyses indicate substantial variation among populations, with eastern populations often showing higher abundance estimates and older age structures, whereas other populations showed higher detectability, lower survival, or contrasting age structures. The average age ranged from 6.5 to 8 years, and sexual maturity was generally reached at 3-4 years. Females showed a faster growth trajectory and appeared to attain adult size earlier than males. Phenological patterns also varied among populations, although activity was mainly concentrated between late autumn and spring. Our results suggest marked variation among populations in demographic performance and potential vulnerability. This may reflect local differences in habitat conditions and environmental context. Compared with the limited earlier studies, these findings provide one of the first integrated multi-population demographic baselines for S. infraimmaculata in Anatolia and offer a basis for population-sensitive conservation planning. Given the species' dependence on humid microhabitats and suitable breeding waters, targeted habitat protection, reduction of road mortality, and long-term monitoring should be prioritised to support its persistence in a rapidly changing environment.
Peer review remains the cornerstone of quality control in scientific publishing, yet most reviewers receive little or no formal training in how to perform this essential task effectively. Drawing on our combined experience as authors, reviewers, and journal editors, we provide a practical, step-by-step guide to conducting high-quality, constructive manuscript reviews for those new to the practice. We cover the entire review workflow: deciding whether to accept a review invitation, preparing for the review, conducting a structured, section-by-section evaluation, and writing clear, professional review reports. Key features include assessing expertise and potential conflicts of interest, identifying common pitfalls, providing balanced, evidence-based feedback, and upholding high ethical and open-science standards for transparent processes and accountability. A reviewer checklist is also provided to help structure the assessment process. The aim of this short paper is to assist both novice and experienced reviewers in delivering fair, thorough, and constructive reviews that enhance manuscript quality, reduce unnecessary revision cycles, and ultimately strengthen the reliability and progress of ecological and zoological research.
Natural and sexual selection may shape colouration differently across various body regions. More exposed areas could serve in camouflage, while conspicuous visual signals might evolve in concealed parts. The sand lizard is an ideal species for studying the function of visual signals, as it exhibits sexually dichromatic colouration and has dense populations across Eurasia. In this species, female colouration has been considered cryptic, but comprehensive studies on the topic are lacking. To address this gap, we used a spectrometer to measure brightness and hue in different body regions (dorsum, flank, and venter) in two female phenotypes. We observed sharp differences in brightness across body parts, with the dorsum being less bright than other regions. Concerning hue, we noted different patterns between the phenotypes: while the 'dull' phenotype showed uniform values across the dorsum and flank, the 'green' phenotype displayed high contrast between these body areas. We propose three possible scenarios to explain this result: 1) context-dependent camouflage, 2) a signalling role, and 3) phenotypic plasticity. We conclude that, despite previous perceptions of female sand lizard colouration as cryptic, it is a more complex trait that warrants further investigation.
Animal movement is a key trait shaping species management strategies. Ungulate spatial behaviour varies with ecological conditions and can drive human-wildlife conflicts, necessitating appropriate management. The African aoudad (Ammotragus lervia), introduced to the Iberian Peninsula, has expanded its range and caused such conflicts. This study characterises the spatial behaviour of ten GPS-tracked aoudads in Sierra Espu & ntilde;a by analysing daily distances travelled, home ranges (kernel polygons of 50% and 95% probability, representing the likelihood of finding the tracked individual within those areas), their overlap, and tree-cover selection. Mean daily distance travelled was 1.7 +/- 0.9 km, with females covering longer distances than males. Mean daily K95 was 1.2 +/- 3.8 km2 and K50 was 0.3 +/- 0.9 km2, both showing seasonal variation. Home-range overlap was higher for K95 than for K50. Most locations occurred in areas with 50-75% tree cover, although tree-cover selection varied across seasons and times of day. Movement patterns varied by season and sex, with females adjusting their movements throughout the year, possibly in response to reproductive demands. Aoudads preferred areas with high tree cover, particularly in summer, likely as thermal refuges. These findings highlight the importance of spatial ecology for guiding management amid increasing human-wildlife conflicts and climate warming.
Seasonal environmental variation strongly influences bird reproduction, growth, migration and survival. The house sparrow, a characteristic urban species, is declining in parts of its native range, yet information on adult and juvenile survival in Mediterranean countries remains scarce. We examined annual (year-to-year) and seasonal survival patterns (between quarters defined by the biology of the species) in an urban population in eastern Spain. A total of 198 sparrows were colour-marked, and 147 (74.2%) were re-sighted or recaptured. Apparent survival was estimated using Cormack-Jolly-Seber (CJS) models. Annual survival declined during the study period (2017-2020) and was lower in adult females (0.350 +/- 0.060 SE) than in males (0.480 +/- 0.068 SE), while juveniles showed the lowest survival (0.281 +/- 0.098 SE). Seasonal patterns indicated reduced survival in summer, coinciding with the end of the breeding season, with slightly lower values in females. A review of published European annual survival estimates revealed a general decline in both adult and first-year survival over time, with lower values typically reported in local studies than in national assessments, suggesting that reduced survival may contribute to ongoing population declines. Robust, geographically representative survival estimates, together with updated productivity (annual reproductive output) data under current urban conditions, such as reduced food availability, limited nesting sites and high pollution levels, are essential to evaluate population trajectories and assess the long-term viability of the species across its European range.
Epidermal defence effectors are part of protective systems associated with exocrine production. This study presents new data on axillary glands (AXGs), defence structures associated with pectoral fins, and epidermal club cells (ECCs) of Synodontis multipunctatus and three closely related species. AXGs are described as exocrine structures made up of multicellular lobes that produce a holocrine, gel-like secretion containing over 1,800 protein components, mainly mucins. Research into AXG morphogenesis revealed their rapid development after hatching and early onset of functionality in all species studied. In adults, AXG structure indicated full functionality in S. multipunctatus, whereas less developed glands or remnants were seen in adults of closely related S. irsacae, S. petricola, and S. polli. Although venom glands are widely reported in catfish fins, they were not found as morphologically distinct organs in the pectoral fins of the Synodontis species studied. Ultrastructural analysis revealed that the putative gland cells in the pectoral fins belong to the epidermal club cell line. Our results raise questions about whether there is a diversified gland developmental programme related to defence and protection in individual Synodontis species and challenge the taxonomic significance of the AXG pore.
Brood parasitism by the common cuckoo (Cuculus canorus) of its avian hosts is a classic model of coevolution. A previously published study proposed and provided experimental evidence supporting hypotheses about the function of the female common cuckoo's distinctive 'bubbling' call during parasitism. While acknowledging their methodological rigour and results, we highlight key evidence that challenges their conclusions about the role of the cuckoo's vocalisation as a counter-defence strategy. In our study, we analysed 11 years of video surveillance data, combining 284 recordings of parasitism events from China and the Czech Republic at the nests of two major host species. Notably, female cuckoo vocalisation during parasitism was nearly absent (282 out of 284 cases). These data provide compelling evidence against the hypothesis that the bubbling call serves as a counter-defence strategy to deceive hosts. Moreover, two female cuckoos that vocalised at host nests were mobbed, further suggesting that the bubbling call does not misdirect host defences. Finally, we provide new insights into the proximate and ultimate factors that likely prevent female cuckoos from vocalising during parasitism, contextualised within recent research on brood parasitism.
For more than a century, studies have documented relationships between environmental variables and species morphology. Biogeographic and macroecological patterns have been identified across several faunal groups worldwide, revealing distinct trends for endotherms and ectotherms. We selected Stenocercus lizards as a model group to explore morphological variation in relation to geographic distribution and environmental variables in Neotropical ectotherms. We analysed intraspecific allometric variation and linear morphological data from 12 Stenocercus species from Ecuador across their elevational and latitudinal distributions. We also examined relationships between morphological variation and bioclimatic variables. We found that Stenocercus species at higher elevations have shorter limbs, whereas those at lower elevations have longer limbs. We did not find significant relationships between snout-vent length or head size and elevational or latitudinal distribution. Elevation and precipitation seasonality were the strongest explanatory variables. Finally, we discuss potential mechanisms underlying these biogeographic patterns and recommend further research that considers additional environmental variables at finer spatial scales.
Understanding mechanisms of species coexistence remains central to ecological theory. Our study tested predictions of niche theory by examining the isotopic niches of small mammal communities across four forest types (oak, beech, spruce, timberline) along an elevational gradient in the Southern Carpathian Mountains of Romania. We analysed delta 13C and delta 15N values from hair samples of seven rodent and insectivore species collected over three years from oak, beech, spruce and timberline forests. Using stable isotope analysis-Bayesian ellipses and convex hull metrics-we evaluated niche width, overlap and community-level structure. Results showed narrowing of isotopic niches and reduced overlap in high-elevation habitats, consistent with predictions based on decreased ecological opportunity. Apodemus flavicollis and Clethrionomys glareolus, the dominant forest species, exhibited dietary segregation that intensified at high elevations. Apodemus agrarius had a distinct isotopic profile and minimal niche overlap, reinforcing its marginal forest role and indicating foraging in neighbouring open habitats at low elevations. Community metrics confirmed tighter niche packing and reduced trophic diversity at timberline sites. Our findings support the view that small mammal communities along elevational gradients exemplify niche partitioning as a mechanism for species coexistence under resource constraints.
Mountain ecosystems are highly vulnerable to environmental change, particularly due to climate warming and habitat alteration. Despite this, behavioural responses of mountain bird species, especially foraging adaptations to variable environmental conditions, remain poorly studied. Here, we examined the foraging behaviour of the ring ouzel (Turdus torquatus alpestris, Brehm) under fluctuating prey availability driven primarily by soil and weather conditions. Simple linear regression models revealed a positive relationship between soil humidity and prey capture attempts from the soil (primarily earthworms), and a negative relationship between soil humidity and foraging on the soil surface and in low vegetation. Multiple regression models confirmed soil humidity as a statistically significant predictor for all three foraging measures and indicated that air temperature had a positive effect only on foraging in low vegetation. The study demonstrates a strong preference for earthworms when accessible, alongside flexible foraging behaviour and the capacity to switch among microhabitats in response to changing environmental conditions. These findings highlight the importance of wet soil and short vegetation as key foraging spaces for the ring ouzel during breeding. The results have implications for conservation management in montane ecosystems under climate change.
The inner ear of teleost fishes is crucial for hearing and balance. It contains three pairs of otoliths that stimulate the innervating nerve as they move, with the saccular otolith (sagitta) being the largest in most taxa. Shape and size influence the motion of the sagitta and hence sound detection and balance, and are influenced by the ecological niche occupied by the fishes. We were interested in whether the otoliths differ along a spatial gradient in sympatric gobiids. We investigated free-living gobies (Istigobius Whitley, 1932), free-living but temporary burrowing gobies (Amblygobius Bleeker, 1874, Valenciennea Bleeker, 1856) and gobies living in shrimp burrows (Cryptocentrus Valenciennes, 1837, Austrolethops Whitley, 1935). The free-living species had thin sagittae, whereas the gobies inhabiting shrimp burrows had thick sagittae. The thickest otolith was found in Austrolethops wardi Whitley, 1935, a species that permanently inhabits shrimp burrows. The morphology of the otolith of A. wardi is unique among gobiids but reflects its relationship to the Gunnelichthys-lineage. We also analysed otoliths of blind cave fishes and fishes with atrophied eyes, in comparison with those not affected by cave-life. Alterations of the otolith morphology occurred in most of the cave fishes, and the most common alteration was thickening of the otolith.
Chemical communication is important in amphibians, contributing to various functions such as social interactions, foraging, parental care, mate recognition, and predator deterrence. Unlike most anurans (frogs and toads) and caudatans (salamanders and newts), most gymnophionan amphibians (caecilians) lead a secretive, burrowing life and have reduced visual systems; hence, they are expected to make substantial use of chemical communication. In addition, caecilians uniquely possess a protrusible pair of little-studied and poorly understood chemosensory tentacles that connect to the vomeronasal organs, suggestive of reliance on (vomer-)olfaction communication. However, current knowledge of the behaviour of (vomer-)olfaction and chemical communication in caecilians is almost non-existent, having been studied briefly in only two species previously. We investigated the role of olfactory cues in self-recognition in a terrestrial Indian caecilian Gegeneophis sp., using a Y-maze behavioural choice experiment. We analysed choices made under self vs. blank chemical-cue conditions. Individuals expressed a significant preference for self-cues over no cues. This is only the second study on self-recognition in caecilians mediated by olfactory cues, and the first to test it in a terrestrial, soil-dwelling species with highly reduced eyes.
Biological invasions generate novel host-parasite associations that can drive rapid evolutionary change. We tested whether European bitterling (Rhodeus amarus) exhibit behavioural avoidance of the infective parasitic stage (glochidia) of the invasive Chinese pond mussel (Sinanodonta woodiana). Glochidia are released from adult mussels and must attach to a host fish within a few hours to become encysted and continue their development. Across multiple R. amarus and S. woodiana populations, differing in their history of coexistence (from completely na & iuml;ve to 40+ years of coexistence), R. amarus did not show any avoidance of glochidia. Fish spent similar amounts of time in parasite and parasite-free environments, and neither their mean nor maximum swimming speed was affected by the presence of glochidia. No behavioural spatial avoidance of glochidia was detected regardless of invasion history. Body size was the only factor affecting swimming activity, with larger individuals swimming faster regardless of glochidia presence. These findings suggest that behavioural avoidance may not play a major role in host defence in this system, at least under simplified experimental conditions. Our results provide evidence that behavioural avoidance is not a primary defence mechanism of R. amarus to limit infection by parasitic glochidia of an invasive S. woodiana mussel.
Spatial and social population structures can influence intra-and interspecific genetic processes. We investigated the spatial and social genetic structure of two sister species and evaluated whether there was evidence of hybridisation between them at a microgeographic scale, in syntopy. Our study models were Rhabdomys bechuanae (Rbech) and Rhabdomys dilectus dilectus (Rdil). We generated population genetic data using microsatellite markers and cross-referenced some of these results with published behavioural data from a prior study, reanalysed here. We compared genetic diversity and gene flow both in sympatry and allopatry, we tested for hybridisation between the sister species in sympatry and assessed the relationship between kinship and fine-scale spatial and social organisation. Genetic diversity was high within all populations of the two species. Population genetic substructure was more pronounced in Rbech than in Rdil, consistent with stronger group cohesion reported for Rbech. STRUCTURE and NEWHYBRIDS analyses suggested that sympatric individuals, 5% in Rbech, and 2% in Rdil, might have hybrid ancestry. Our results indicate social fences may limit gene flow within and between species. Further, limited hybridisation suggests that, despite syntopy, only rare events of hybridisation may occur, possibly at phases of density troughs and/or that F1 hybrids have a relatively low fitness.
Moult is a challenging stage in the life of birds. Small passerines replace their plumage, a substantial proportion of their body mass, annually to preserve its vital functions. Surprisingly, most species downregulate corticosterone, a major mediator of energy metabolism and the stress response, during this energetically demanding period. Experimental studies suggest that corticosterone has detrimental effects on feather quality and, within species, slows feather growth rate (FGR), prolonging the period when plumage functions are compromised. However, how corticosterone affects moult in natural populations or at the macroecological scale remains poorly understood. In this study, we analysed corticosterone deposited in tail feathers (fCORT), a cumulative measure across multiple days relevant to moult, in an unprecedented sample of 87 passerine species from Europe and the Afrotropics. Our data showed moderate between-and high within-species repeatability, supporting the usefulness of fCORT as a stress record across species. We found no association of fCORT with either FGR or fault bar occurrence. Unlike circulating corticosterone, fCORT did not differ between latitudes. However, there was a weak trend towards higher fCORT in high-elevation tropical species. More research is needed to understand how birds regulate corticosterone during moult and how it affects moult in natural populations.
Harlequin toads (Atelopus) are among the most threatened vertebrates, yet their trophic ecology remains poorly understood owing to the virtual disappearance of most populations and constraints on noninvasive sampling. Here, we combine DNA metabarcoding of faecal samples from six surviving harlequin toad species from Ecuador with synchrotron-based microtomography of historic, fluid-preserved material from seven species across all major clades of the genus to assess dietary composition. Metabarcoding revealed a diverse invertebrate diet with marked ecological segregation between habitats, suggesting potential specialisation on Hymenoptera in species inhabiting low-to mid-elevation forests and broader prey spectra in high-Andean taxa. Synchrotron scanning, for the first time, enabled non-destructive recovery of 3D images of arthropod exoskeletons from the intestinal system of amphibians, confirming hymenopterans as key prey for forest-associated Atelopus in historical specimens. This dual approach overcomes the limitations of traditional and single-method studies, offering a scalable, non-invasive framework for dietary analyses. By providing curated step-by-step commands for sequence processing, we further aim to make dietary metabarcoding more accessible to zoologists. Our study substantially expands dietary data for near-extinct harlequin toads and supports conservation efforts with urgently needed ecological insights as a baseline for adapted conservation breeding and integrative conservation of trophic webs.
Cetaceans display an unusual combination of tooth simplification and frequent tooth-number expansion: baleen whales (Mysticeti) lost functional teeth, whereas many toothed whales (Odontoceti) have evolved elongated, homodont tooth rows. The genomic underpinnings of these divergent trends remain incompletely resolved. We quantified dental complexity using literature-curated orientation patch count (OPC) and found a pronounced decline from archaeocetes to crown taxa, consistent with the abandonment of mastication. Comparative genomics corroborates recurrent pseudogenisation of enamel-matrix genes (notably ODAM) in lineages with reduced enamel, indicating relaxed selective constraint. In contrast, analyses of tooth-number regulators reveal lineage-specific accelerations in EDA/EDAR and Wnt/FGF modulators (e.g. APC, SPRY2). A branch-site test detects episodic positive selection on EDA along the odontocete stem (2 Delta lnL = 9.82, q = 0.006), with three high-confidence sites (Bayes Empirical Bayes (BEB) >= 0.95: 287, 301, 315) in the TNF homology domain, consistent with tuning of EDAR signalling. Phylogenetically controlled regressions link tooth number with EDA evolutionary rate. Our results support a two-track macroevolutionary model in whales: 1) relaxed constraint on enamel-matrix genes accompanying tooth simplification, and 2) adaptive tuning of EDA/EDAR and associated pathways contributing to tooth-number expansion.
