ABSTRACT Environmental factors influence females and the resources they accumulate and invest in their eggs. We studied the influence of climatic variables and corporal attributes of Caiman latirostris females on egg characteristics, hatching success and hatchling size. We recorded reproductive metrics of female body and physiological condition, and collected their entire clutches. One group of the eggs in a clutch was assigned for fatty acid profile analysis (FA), while another was used for artificial incubation. We also registered the precipitation and temperature of previous reproductive season and prior to oviposition. Eggs from females with better body condition had a higher proportion of the essential fatty acid (EFA) C20:4 and higher polyunsaturated FA content. EFAs such as C20:4, C22:5, and C22:6 in eggs were positively associated with seasonal precipitation and temperature, suggesting that rainy years are beneficial for maternal investment. In contrast, C18:2 in eggs was negatively associated with precipitation during vitellogenesis but positively correlated with maternal tissue fatty acids. The high proportion of C18:2 may reflect a greater consumption of prey rich in C18:2, such as insects or mollusks, possibly associated with a less diverse diet resulting from changes in resource availability driven by climatic conditions during these periods. High C18:2 content in eggs was associated with lower hatching success. Therefore, years with abundant precipitation during vitellogenesis are advantageous because they may increase prey diversity and resource availability for females, allowing greater transfer of physiologically important fatty acids to eggs.
ABSTRACT The Squamata group exhibits remarkable diversity in lung structure. However, a comprehensive understanding of how this variation evolved within the clade is still lacking. To reconstruct the evolutionary history of lungs of living squamates, we conducted comparative phylogenetic analyses using categorized lung traits, such as lung type, respiratory epithelium type, and distribution of parenchyma, obtained from literature‐derived morphological data. Stochastic character mapping on an amniote phylogeny revealed uncertainties regarding the ancestral lung type at the amniote root, whereas strong support for a unicameral lung was found at the base of Lepidosauria, Squamata, Toxicofera, Iguania, and Anguimorpha. Correlation analysis revealed a small but significant association between epithelium type and distribution, suggesting a degree of correlated evolution among these traits.
ABSTRACT Early‐life environments can shape behavioural development trajectories without altering DNA. In this review, we consider how non‐genetic factors, particularly parental care, shape behavioural development in rodents, using African striped mice ( Rhabdomys ) as our primary model. The Rhabdomys system is particularly informative because it encompasses a natural gradient from solitary to group‐living strategies, demonstrates marked social plasticity and combines field observations with laboratory experimental manipulations. Long‐term studies of Rhabdomys , integrated with broader rodent research including laboratory rats, mice and voles, reveal that early parental care creates lasting changes in sociality, stress physiology, cognition and reproductive behaviour. These changes are mediated through epigenetic, hormonal and neuroendocrine mechanisms that can persist across generations. We frame this review within Developmental Systems Theory (DST), which considers development as the emergent dynamic interplay of genes, environment and experience. Maternal care, via tactile stimulation, diet and social context, forms the primary basis of early caregiving, while paternal and communal care contribute significantly to development in biparental and group‐living species. Cross‐fostering and isolation experiments demonstrate that caregiving can modify developmental trajectories independent of genetic inheritance. This plasticity enables behavioural adjustments to local ecological conditions; when outcomes are adaptive and transgenerationally stable, caregiving itself becomes a target of selection. Understanding developmental plasticity as an evolutionary force, rather than noise around a genetic mean, improves our ability to predict behavioural trajectories under environmental change. This framework has direct applications in conservation biology, captive breeding programmes and perinatal medicine. Because these developmental mechanisms are conserved across vertebrates, rodent studies provide broad insights into how plasticity in caregiving contributes to rapid behavioural evolution.
ABSTRACT Camera traps are extensively used to monitor medium‐ and large‐bodied mammals, but the avian bycatch they generate remains largely untapped in biodiversity assessments. This underuse is particularly evident in urban ecosystems, despite the growing application of camera trapping in cities. Here, we evaluated the ecological value of bird detections obtained opportunistically from camera traps by comparing them with standardized point count surveys conducted in 2023–2024, across the metropolitan area of Firenze, central Italy, and explored their potential to indicate broader urban biodiversity patterns through cross‐taxa relationship with mammal richness. Combining both methods, we recorded 72 bird species, with camera traps detecting two‐thirds of total richness. Bird species richness estimated from camera traps was strongly and positively correlated with richness derived from point counts across sampling stations, indicating that camera‐trap bycatch captures consistent spatial patterns in avian diversity. Bird communities detected by the two methods showed a high degree of species overlap (70%), although modest but significant differences in community composition were observed, reflecting method‐specific detection biases. Using camera‐trap data, we detected a positive association between mammal and bird richness values across sites. This relationship was confirmed after accounting for variation in sampling effort and seasonal effects, suggesting that local areas supporting a higher diversity of birds also tend to support a richer mammal community. Overall, our results show that avian bycatch from camera traps provides meaningful information on bird diversity and complements traditional survey methods, while also offering potential insights into multi‐taxon biodiversity patterns. Repurposing existing camera‐trap datasets can therefore enhance the efficiency and taxonomic breadth of urban biodiversity monitoring programs.
Escaping from predators is a crucial behavior for organism survival and represents a key target of natural selection. Temperature is one of the most influential environmental factors in individual development by influencing physiological performance and, consequently, overall fitness. This study aimed to describe the escape response of a flexible fish species to a simulated predator attack and to evaluate the effect of increasing temperature-associated with climate change-on escape velocity, using Galaxias maculatus as a model species. We hypothesized that G. maculatus exhibits a higher turning rate compared to less flexible fish, and that individuals exposed to warmer experimental temperatures perform faster escape responses due to enhanced neurophysiological processes. Specimens were collected from Tierra del Fuego National Park (55 degrees S) and maintained at 10 degrees C (current average summer temperature) and 16 degrees C (projected average temperature for the year 2100). Their escape responses to a mechano-acoustic stimulus were recorded at 480 fps. Galaxias maculatus displayed a two-stage "C-start" escape response, with an average duration of 70 ms and a high turning rate. Individuals tested at 16 degrees C exhibited higher velocity and turning rates, and shorter stage 1 durations compared to those at 10 degrees C. Our results indicate that G. maculatus changes its behavior with increasing ambient temperature in response to simulated attacks, producing faster escape responses at higher temperatures. Moreover, the findings suggest that this species tends to prioritize directional control-often swimming toward the predator-over maximizing escape speed.
Abstract Traditionally, morphological characterization has served as the primary method for species identification; however, it often fails to distinguish cryptic species or organisms with overlapping phenotypic traits. Modern techniques, though available, are frequently expensive and time‐consuming. In this context, Fourier transform infrared spectroscopy (FTIR) has emerged as a promising alternative. This technique is cost‐effective, provides rapid results and requires minimal sample preparation. Each organism exhibits a unique vibrational spectral fingerprint, enabling reliable classification when coupled with multivariate analysis. This review explores the application of FTIR spectroscopy in the taxonomic identification of macro‐organisms. We highlight its ability to generate distinct vibrational spectral fingerprints, and when coupled with multivariate statistical tools, such as hierarchical cluster analysis (HCA) and principal component analysis (PCA), can effectively differentiate taxa at the family, genus and species levels. The analysis also evaluates common software platforms for spectral processing, assessing their suitability for biological classification. The reproducibility and discriminative capacity of spectral data demonstrate its value in resolving taxonomic relationships and contributing to spectral library development. These insights underscore the broader potential of FTIR spectroscopy in supporting global biodiversity conservation, ecological research and environmental assessment initiatives.
Ageing is associated with a reduction in cognitive function and numerous studies have focused on age-related cognitive decline in laboratory rodent models to provide insight into human ageing and neurogenerative disease. However, fewer studies have focused on age-related cognitive decline in captive wild animals, which typically live longer than their free-roaming wild counterparts. In this study, we investigated whether recognition memory, measured using a novel object recognition (NOR) task, declines with age in a captive population of native Australian fawn-footed mosaic-tailed rats (Melomys cervinipes). Adult individual mosaic-tailed rats were tested for NOR twice, 4.6 years apart. Both younger and older mosaic-tailed rats took longer to approach the novel object, while intermediate-aged rats responded the fastest. Interestingly, rats were also less discriminatory when at an intermediate age, although this was not statistically significant. Sex affected the number of interactions with the novel object, with female mosaic-tailed rats interacting more with the unfamiliar object than males. This is the first study exploring age-related cognitive decline in NOR in a native Australian rodent, indicating that recognition abilities of mosaic-tailed rats do not diminish over time. Instead, some intrinsic biological factors affect NOR and there may be a trade-off in energetic investment associated with neophobia and other factors during the prime-of-life.
Rats have followed mankind into a wide diversity of habitats around the world. This includes many smaller islands, where they present a possible threat to local fauna that have often evolved in the absence of mammalian predators and therefore may not recognise them as dangerous. Many lizards can detect chemicals left behind by predators (mostly snakes) and will change their behaviour in response to them. However, whether lizards recognise mammal scents in general, and of rats in particular, remains unclear. Here we compared the responses towards rat chemical cues between Italian wall lizards (Podarcis siculus) originating from mainland and island habitats. In a first experiment, tongue flick rates (indicative of chemosensorial excitement) and behaviour of lizards were observed in two control situations (blank and pungent) and in the presence of rat scent. Lingual sampling increased dramatically in response to rat cues in both mainland and island lizards, but the animals' overall behaviour hardly changed. We found no evidence that the rat cues elicited stress or anti-predator behaviour. In a second experiment, we offered the lizards the choice between two basking sites, one of which we labelled with rat scent. We found no evidence that lizards systematically avoided the rat-scented perch. We conclude that both mainland and island Italian wall lizards can detect chemicals produced by rats, but these do not elicit noticeable changes in their behaviour (other than increased tongue flick rates). However, in both the control and experimental treatments, island and mainland lizards differed in tongue flick rates and in several aspects of their behaviour.
In social birds such as flamingos, intraspecific interactions are frequent and play a key role in flock cohesion, communication, and the establishment of social networks. These behaviors can reduce competition stress and enhance protection, but their nature and underlying motivations vary. Understanding the patterns and drivers of these interactions can provide valuable ecological insights and inform management, husbandry, and conservation practices. We observed agonistic intra-flock interactions in a wild population of Chilean Flamingo (Phoenicopterus chilensis) at Lagoa do Peixe National Park, southern Brazil. Data were collected on the interactions, flock composition, and environmental conditions. Based on the individuals involved, their characteristics, and the nature of behavioral displays, we classified interactions into three types: unilateral disputes, bilateral disputes, and brief altercations. Using Generalized Linear Mixed Models, we analyzed the influence of flock and environmental variables on two main factors: the probability of physical aggression and the mean duration time of interactions. Our findings indicate that unilateral and bilateral disputes were primarily influenced by flock-related variables, especially during periods with more males and denser aggregations, suggesting a social-driven origin. In contrast, brief altercations were affected by both social and environmental factors, becoming longer in resource-scarce conditions, which indicates competition-driven behavior. These results highlight a dual mechanism shaping intra-flock aggression in Chilean Flamingos: social roles and resource competition. This complexity reveals a fundamental trade-off in group living, between the safety of sociality and the costs of increased conflict, offering important perspectives for the ecological understanding of this and other social species.
Antipredatory behaviors arise from selective pressures associated with predator protection. Recognizing predators is crucial for an appropriate response to aversive stimuli. Animals employ various sensory cues to differentiate between predator types and assess the level of danger they face. Snakes are notable for having a broad range of predators and one of the most diverse repertoires of defensive behaviors. During heightened responses to aversive stimuli, one of the behaviors displayed is the venomous bite, particularly relevant because it triggers snakebite incidents in humans. In studying the essential sensory factors that initiate venomous snakebites, we investigated the sensory cues employed by snakes for envenomation. Consequently, we examined the consequence of human-derived sensory stimuli, such as temperature, vision, and odor, in influencing the probability and accuracy of venomous strikes. Our model species was the lancehead pit viper Bothrops jararaca, widely distributed and a major cause of envenomation in Brazil. We conducted sensory deprivation experiments on the snakes and tested sensory stimuli in isolation and in all possible combinations in order to assess their impact on snake response. Among these cues, the combination of thermal and visual cues significantly increased the occurrence and accuracy of strike responses in snakes. When cues were presented in isolation, thermal cues elicited the strongest strike response from snakes. Although isolated human odor played a limited role in strikes, its interaction with other sensory cues synergistically increased both the frequency and accuracy of strikes. Consequently, this study equips us with tools to understand and develop strategies for preventing snakebite envenomations. Comportamentos anti-predat & oacute;rios surgem de press & otilde;es seletivas associadas & agrave; prote & ccedil;& atilde;o contra predadores. Reconhecer predadores & eacute; crucial para uma resposta adequada a est & iacute;mulos aversivos. Os animais utilizam diversas pistas sensoriais para diferenciar tipos de predadores e avaliar o n & iacute;vel de perigo que enfrentam. As cobras s & atilde;o not & aacute;veis por terem uma ampla gama de predadores e um dos repert & oacute;rios mais diversos de comportamentos defensivos. Durante respostas intensificadas a est & iacute;mulos aversivos, um dos comportamentos exibidos & eacute; bote defensivo, particularmente relevante porque desencadeia incidentes de mordidas de cobra em humanos. Ao estudar os fatores sensoriais essenciais que iniciam botes defensivos de cobras, investigamos as pistas sensoriais utilizadas pelas cobras para envenenamento. Consequentemente, examinamos a consequ & ecirc;ncia de est & iacute;mulos sensoriais derivados de humanos, como temperatura, vis & atilde;o e odor, na influ & ecirc;ncia da probabilidade e precis & atilde;o de botes defensivos. Nossa esp & eacute;cie modelo Bothrops jararaca, & eacute; amplamente distribu & iacute;da e uma das principais esp & eacute;cies a causar envenenamento no Brasil. Realizamos experimentos de priva & ccedil;& atilde;o sensorial nas cobras e testamos est & iacute;mulos sensoriais isoladamente e em todas as combina & ccedil;& otilde;es poss & iacute;veis para avaliar seu impacto na resposta das cobras. Dentre essas pistas, a combina & ccedil;& atilde;o de pistas t & eacute;rmicas e visuais aumentou significativamente a ocorr & ecirc;ncia e a precis & atilde;o das respostas de ataque das cobras. Quando as pistas foram apresentadas isoladamente, as pistas t & eacute;rmicas provocaram a resposta de ataque mais forte das cobras. Embora o odor humano isolado tenha um papel limitado nos botes, sua intera & ccedil;& atilde;o com outras pistas sensoriais aumenta sinergicamente tanto a frequ & ecirc;ncia quanto a precis & atilde;o dos botes defensivos. Consequentemente, este estudo nos equipa com ferramentas para entender e desenvolver estrat & eacute;gias para prevenir envenenamentos por mordida de cobra.
The intensification of human activities exerts an influence on animal behaviour, resulting in noticeable shifts in species distributions, movements and activity patterns. Differential responses among sympatric species, influenced by human disturbance, have the potential to alter species interactions, such as predator-prey relationships. This study investigated the impact of human disturbance on the activity patterns of wolves and their potential prey, as well as their spatiotemporal interactions, in one of the historical strongholds of wolves in Italy, where both large predator and human presence have long been established. Data were collected between October and April to provide a focused snapshot of cold season dynamics, when environmental conditions and human activities show limited temporal variability. Local human disturbances (considering both urbanization and outdoor recreation) were found to have a negligible impact on the temporal and spatial niche use of wolves and, overall, had a modest effect on the mammal community studied, both in terms of individual species' activity patterns and their spatiotemporal interactions with the large predator. Wild boar was the only ungulate species that increased its nocturnality in more urbanized landscapes, resulting in increased temporal overlap with wolves. On the contrary, fallow deer was found to have more diurnal activity in more urbanized areas, which suggests habituation to humans. Interestingly, our results showed that human disturbance might indirectly benefit wolves by increasing their temporal overlap with their primary prey, the wild boar. Overall, our findings indicate substantial tolerance to human disturbance in a long-established coexistence system, with limited behavioural change and preserved predator-prey temporal coupling.
Insular environments modify the nature, direction, intensity and complexity of both biotic and abiotic conditions, thereby shaping species' genotypes and phenotypes. Many of these changes intersect with functions commonly associated with melanin-based colourations such as thermoregulation, camouflage and predator deterrence, suggesting a potential link between insularity and melanism. However, although the effects of insularity on traits such as body size are well documented, its influence on other phenotypic traits, including colouration, remains largely unexplored across most taxa, leaving general patterns poorly understood. Here, we address this gap by quantitatively assessing whether insular populations of the amphibian fire salamander (Salamandra salamandra) exhibit a higher proportion of melanic colouration than mainland populations, while accounting for local variation, sex and body size. We show that salamanders from one of the three studied islands exhibit a higher proportion of dorsal black colouration, indicating the role of local pressures in shaping colour patterns. In contrast, insular populations exhibit reduced variation in the proportion of melanic colouration relative to their mainland counterparts, suggesting constraints on phenotypic diversity in insular environments. Additionally, body size significantly influences colouration, and partial sexual dimorphism is evident, with females tending to present more black proportion than males. Overall, this study advances our understanding of colour variation in insular amphibians and provides a foundation for further work investigating the evolutionary mechanisms and functional significance of melanism in this system. Los ambientes insulares modifican la naturaleza, direcci & oacute;n, intensidad y complejidad de las condiciones tanto bi & oacute;ticas como abi & oacute;ticas, modelando as & iacute; los genotipos y fenotipos de las especies. Muchos de estos cambios se relacionan con funciones com & uacute;nmente asociadas a las coloraciones mel & aacute;nicas, como la termorregulaci & oacute;n, el camuflaje y la disuasi & oacute;n de depredadores, lo que sugiere un posible v & iacute;nculo entre la insularidad y el melanismo. Sin embargo, aunque los efectos de la insularidad sobre rasgos como el tama & ntilde;o corporal est & aacute;n bien documentados, su influencia sobre otros rasgos fenot & iacute;picos, incluida la coloraci & oacute;n, sigue estando en gran medida inexplorada en la mayor & iacute;a de los taxones, lo que dificulta la identificaci & oacute;n de patrones generales. En este estudio, abordamos esta laguna en el conocimiento mediante la evaluaci & oacute;n cuantitativa de si las poblaciones insulares del anfibio salamandra com & uacute;n (Salamandra salamandra) presentan una mayor proporci & oacute;n de coloraci & oacute;n melanica que las poblaciones continentales, teniendo en cuenta la variaci & oacute;n local, el sexo y el tama & ntilde;o corporal. Mostramos que mayores proporciones de coloraci & oacute;n negra dorsal son m & aacute;s frecuentes en las salamandras de una de las tres islas estudiadas, lo que pone de manifiesto el papel de las presiones locales en la configuraci & oacute;n de los patrones de coloraci & oacute;n. En contraste, las poblaciones insulares presentan una menor variabilidad en la cantidad de color negro en comparaci & oacute;n con sus hom & oacute;logas continentales, lo que sugiere la existencia de restricciones sobre la diversidad fenot & iacute;pica en ambientes insulares. Asimismo, el tama & ntilde;o corporal influye significativamente en la coloraci & oacute;n y se observa un dimorfismo sexual parcial, con una tendencia de las hembras a presentar una mayor proporci & oacute;n de color negro que los machos. En conjunto, este estudio ampl & iacute;a la comprensi & oacute;n de la variaci & oacute;n en la coloraci & oacute;n en anfibios insulares y sienta las bases para futuras investigaciones sobre los mecanismos evolutivos y la relevancia funcional del melanismo en este sistema.
Invasive species are increasingly reshaping drylands worldwide, yet their behavioural adaptations remain poorly understood. The wild pig (Sus scrofa) is a species that is physiologically non-adapted to arid conditions; however, it has successfully colonized these environments and has been established in the Monte Desert, Argentina, since the 1980s. We examined the behavioural adaptations of wild pigs in Argentine drylands by comparing their occupancy and activity patterns between a protected area (Biosphere & Ntilde;acu & ntilde;& aacute;n Reserve) and a private grazed field. Using 98 camera trap stations, we assessed the influence of environmental and anthropogenic variables on wild pig behaviour. Bayesian occupancy modelling revealed that proximity to water sources (i.e. water availability) was the strongest predictor of wild pig presence, while human-related variables also significantly and negatively influenced occupancy patterns. Activity pattern analysis revealed moderate overlap (Delta 1 = 0.57) between the two land-use types but with significantly different temporal distributions. In the reserve, wild pigs were crepuscular and nocturnal (38.9% for both), while in the grazed field, they were predominantly nocturnal (50%). These findings highlight that wild pigs adapt to arid environments by seeking water and adjusting their activity to avoid thermal stress and human encounters. Notably, permanent artificial watering points created for livestock facilitate wild pig persistence, emphasizing how human activities unintentionally support the expansion of this invasive species in Argentina's drylands. Las especies invasoras est & aacute;n transformando cada vez m & aacute;s las tierras & aacute;ridas en todo el mundo, pero sus adaptaciones comportamentales siguen siendo poco conocidas. El jabal & iacute; (Sus scrofa) es una especie no adaptada fisiol & oacute;gicamente a las condiciones & aacute;ridas; sin embargo, ha colonizado con & eacute;xito estos ambientes y se ha establecido en el Desierto del Monte, Argentina, desde la d & eacute;cada del 80. Examinamos las adaptaciones comportamentales del jabal & iacute; en las tierras secas de Argentina comparando su ocupaci & oacute;n y patrones de actividad entre un & aacute;rea protegida (Reserva Biosfera de & Ntilde;acu & ntilde;& aacute;n) y un campo privado de pastoreo aleda & ntilde;o. Se utilizaron 98 estaciones de trampas c & aacute;mara y se evaluaron la influencia de las variables ambientales y antropog & eacute;nicas sobre su comportamiento. El modelo de ocupaci & oacute;n bayesiano revel & oacute; que la proximidad a fuentes de agua fue el predictor m & aacute;s fuerte de la presencia del jabal & iacute;, mientras que las variables relacionadas con humanos tambi & eacute;n influyeron de manera significativa y negativa en los patrones de ocupaci & oacute;n. El an & aacute;lisis de patrones de actividad demostr & oacute; una solapamiento moderado (Delta 1 = 0.57) entre la reserva y el campo pastoreado, pero con distribuciones temporales significativamente diferentes. En la reserva, el jabal & iacute; fue crepuscular y nocturno (38.8% cada uno), mientras que en el campo pastoreado fue predominantemente nocturno (50%). Estos hallazgos destacan que el jabal & iacute; se adapta a ambientes & aacute;ridos buscando agua y ajustando su actividad para evitar el estr & eacute;s t & eacute;rmico y los encuentros con humanos. Cabe destacar que las aguadas artificiales creadas para el ganado facilitan la persistencia del jabal & iacute;, lo que pone de relieve c & oacute;mo las actividades humanas contribuyen involuntariamente a la expansi & oacute;n de esta especie invasora en las tierras & aacute;ridas de Argentina.
Sexual dietary divergence was detected in more than half of the anuran species analyzed and appears to have evolved independently multiple times across the phylogeny. Our global synthesis revealed that trophic differences between males and females are more strongly associated with ecological traits, including habitat use, activity period, and foraging strategy, than with sexual size dimorphism alone. These findings highlight the importance of ecological context in shaping sex-specific diets and provide a broad evolutionary framework for understanding sexual dimorphism in amphibians.
Oxygen is one of the most limiting factors in high-altitude environments. In response to oxygen limitations, organisms can exhibit phenotypic adjustments across various levels of biological organization. Strikingly, few studies have evaluated this topic by incorporating replication across several mountain systems, which is essential for assessing the similarity of phenotypic responses across different elevation gradients. Here, we evaluated histomorphological changes in the lung and cardiac tissues in nine populations of the mesquite lizard Sceloporus grammicus, considering three elevation gradients (mountains) in the Trans-Mexican volcanic belt. Our results show that altitude induced some histomorphological changes in the cardiorespiratory organs (lungs and cardiac ventricle), consistent with previous reports. However, we also observed that some attributes in the lung and heart tissues varied across the mountains, possibly as a result of biotic and/or abiotic factors not considered in our study. Therefore, our findings suggest that similar changes may be associated with increasing elevation in different populations of the same species, and that the particular conditions of each individual mountain may affect how those changes manifest.
Jaguars are declining in the Americas due to habitat loss and conflict with humans, yet some strategies offer possibilities to balance human and jaguar needs. Certified reduced-impact selective logging (RIL) provides a land-sharing framework for sustainable forest management and biodiversity conservation. Since subsistence hunting occurs in some certified RIL areas, understanding the capacity of these areas to support jaguar populations is essential for jaguar conservation planning and validation that certification standards are being met. We used large-scale camera trapping to estimate the impact of subsistence hunting on jaguar densities within the community-managed forest of Uaxact & uacute;n and two protected areas in Guatemala's Maya Biosphere Reserve. Human access, measured as walking time from settlements, was a proxy for subsistence hunting pressure. Using spatial capture-recapture, we modeled spatial variation in density as a function of structural habitat covariates, prey defaunation index, human access, and protection type. We found that structural habitat did not influence jaguar density; however, their density was positively associated with less accessible areas (effect: 1.36, se = 1.16), indicating a 36% increase in jaguar density every 6.23 walking hours. Jaguar densities ranged from 1.15 to 2.85 jaguars/100 km2 in Uaxact & uacute;n and 1.26 to 4.78 jaguars/100 km2 in remote Mirador-Rio Azul National Park (MRANP) areas. The overall density was 2.39 individuals/100 km2, translating to a population of 50 individuals (95% CI: 48-51) in MRANP and Uaxact & uacute;n. This relationship quantification provides information to improve predictive conservation science and jaguar conservation planning. Understanding the influence of human access on jaguar population density can help guide the management of subsistence hunting in RIL areas. Although densities were lower in Uaxact & uacute;n, we still registered jaguars near the community, and the density there demonstrated that inhabited-certified forests can support jaguar populations while sustaining traditional livelihoods.
The primary function of insect cuticular hydrocarbons (CHC) is to protect the bearer against desiccation, with long-chain saturated (n-alkanes) compounds being the substance class with the strongest effect. The Urban Heat Island (UHI) effect is the process by which cities become hotter than their surrounding semi-natural areas. This can potentially subject insects to heat and desiccation stress and likely induce shifts in their CHC profile. This hypothesis was tested in three different aculeate Hymenoptera: the bees Halictus scabiosae and Osmia cornuta and the wasp Polistes dominula, sampled in different urban settings in the metropolitan city of Milan (Italy). We expected that warmer and more urbanized areas favour insects with a higher abundance of n-alkanes and a lower abundance of alkenes and/or methyl-branched alkanes. In addition, we expect CHC profiles with longer medium chain length of hydrocarbons and particularly of n-alkanes in these areas. We found that temperature, more than the amount of sealed ground surfaces (a proxy of urbanization), explained the shifts in the CHC profiles of all the three species. The strongest shifts were found in O. cornuta and P. dominula compared with H. scabiosae. P. dominula shifted to longer mean hydrocarbon chain length and longer mean n-alkanes chain length with increasing monthly site temperature. In addition, P. dominula showed a CHC profile poorer in n-alkanes and richer in methyl-branched alkanes only under hotter conditions in the most urbanized sites. This suggests complex interactions between temperature and the degree of urbanization. The species-specific responses to temperature can be explained by the inherent characteristics of the CHC profiles, as the two species with the lowest relative abundance of n-alkanes (O. cornuta and P. dominula) showed the strongest shifts in their CHC profiles. These results show that variations in CHC profiles within a species can be detected even at small spatial scales, such as along urbanization gradients.
Sex- and stage-related trophic strategies can shape energy allocation to reproduction, particularly in dynamic environments. We investigated whether diet varies according to sex and ontogenetic stage in the river shrimp Macrobrachium borellii, an omnivorous decapod inhabiting floodplain lakes of the middle Paran & aacute; River. We predicted that (1) juveniles and females would consume a higher-quality, more specialized diet than males, (2) females would show higher delta 13C in tissues during vitellogenesis and (3) egg isotopic composition would reflect either capital (muscle) or income (hepatopancreas) sources. Using stable isotope analysis (delta 13C, delta 15N), mixing models and isotopic niche metrics, we examined trophic patterns across sexes and stages. The results partially supported the first prediction: females - especially those in the reproductive stage - and juveniles showed greater trophic diversification than males but consumed higher-quality prey. In agreement with the second prediction, females exhibited higher delta 13C values in both tissues during vitellogenesis. For the third prediction, egg isotopic values were more closely aligned with the hepatopancreas than with muscle, indicating reliance on local food income. Overall, females exhibited flexible foraging and an income-breeding strategy, adjusting their diet to exploit locally abundant resources to meet reproductive energetic demands. This strategy is well-suited to the fluctuating hydrological and trophic conditions of floodplain ecosystems and highlights the interplay between trophic flexibility, reproductive tactics and environmental dynamics in crustaceans.
According to a recent article published in this journal, hypometric scaling of the rate of metabolism in animals (where the log-log scaling slope <1) results from the hypometric scaling of muscle resource demand that is proportional to muscle contraction velocity/frequency. According to this "muscle contraction model" (MCM), larger animals have a relatively low mass-specific metabolic rate because they expend less energy on slower, less frequent muscular contractions compared with smaller animals. My article offers a different perspective that makes two major points. First, no evidence unequivocally supports, and several lines of evidence contradict the MCM, thus calling into question its tenability and general applicability. Second, no single mechanism can fully explain the diversity of metabolic scaling observed in the living world. Therefore, I advocate a multi-mechanistic view that includes effects of both resource supply and demand and their regulated interaction, and that distinguishes mechanisms operating in ectotherms versus endotherms and intra- versus interspecific metabolic scaling, and via external versus internal and proximate (functional) versus ultimate (evolutionary) causes/constraints. Important proximate mechanisms include various age/size-dependent resource-demanding biological processes (e.g., growth, reproduction, thermogenesis, and locomotion) and age/size-dependent changes in the relative masses of tissues with high versus low metabolic activity that interact with age/size-dependent resource supply, mediated by cellular and organismal surface areas and internal transport networks that deliver resources to metabolizing cells and expel their wastes (including heat). Mortality rate and associated adaptive life-history responses appear to be important ultimate causes that drive the "pace of life" and supporting metabolic energy expenditure ("fire of life") and their scaling with body mass by means of various proximate mechanisms.
The contrasting mechanisms driving the northward expansion of African raptors into Europe provide a unique opportunity to understand how these species overcome substantial geographical barriers and a major biogeographic boundary. To explore these mechanisms, we analysed three species currently expanding across the Afro-Palaearctic system: the Atlas Long-legged Buzzard (Buteo rufinus cirtensis), R & uuml;ppell's Vulture (Gyps rueppelli), and White-backed Vulture (Gyps africanus). Using species distribution models based on topo-climatic predictors, we estimated environmental favourability for breeding across 6203 operational geographic units and compared outputs with breeding records, recent sightings, ecological traits, and evidence of interspecific interactions. Our results reveal contrasting colonization pathways. The Atlas Long-legged Buzzard shows broad climatic favourability across North Africa and parts of southern Europe, indicating a climate-driven range expansion facilitated by increasingly favourable environmental conditions. By contrast, African vultures exhibit negligible climatic favourability in Europe, despite multiple field observations, including hybrid breeding attempts with Griffon Vultures (Gyps fulvus) in the case of R & uuml;ppell's Vultures, while observations of immature White-backed Vultures remain few and anecdotal per se, yet they have been recorded increasingly and more regularly over the past few years. This mismatch suggests that vulture colonization in Europe is unlikely to be climate-mediated and may instead be facilitated by socially assisted vagrancy, with immature African vultures following migratory Griffon Vultures and integrating into their social and spatial networks. Our findings thus show that African raptors may be transgressing current biogeographic boundaries through fundamentally different mechanisms, with climate-driven expansion in buzzards and socially mediated dispersal in vultures, underscoring the importance of integrating behavioural ecology and interspecific interactions into predictions of species redistribution under global change.
