Biology subjects

Lens, L.

Publications and source records attributed to Lens, L..

At least 19 recordsLinked to original sources

bioRxiv2026

Post-fledging space use and survival in hand-reared versuswild juvenile herring gulls

Parental care can shape post-fledging behaviour through provisioning, guidance and social information, yet its absence may alter how young birds establish space use and habitat preferences. We tested the consequences of absent parental care by comparing, hand-reared juvenile herring gulls released without parents with wild, parent-reared conspecifics, focusing on the first two months after fledging. Wild juveniles frequently revisited their natal nest during the first month, whereas hand-reared birds rarely returned to the release site; revisits declined in both groups by the second month but remained more common in wild birds. Wild juveniles used smaller ranges that subsequently expanded, while hand-reared birds began with larger ranges that later contracted, leading to convergence. Contrary to expectation, wild juveniles occurred in areas with higher human population density than hand-reared birds. Habitat use also differed between groups and changed over time. Early on, wild juveniles concentrated activity in anthropogenic and marine habitats, whereas hand-reared birds used rural green habitats more. Later, both groups shifted away from marine areas towards rural green habitats, reducing but not eliminating between-group differences. Short-term survival, did not differ between hand-reared and wild juveniles, indicating that parental care primarily reshaped early space use and habitat choice rather than immediate survival.

animal behavior and cognition↗

bioRxiv2025

Predicting current and future distribution of the common waxbill using a mechanistic modelling approach

Biological invasions and climate change are two of the most pressing drivers of biodiversity loss worldwide. Anticipating where invasive species are likely to establish, as well as the potential impact of climate change on their range expansion, is essential for early detection and targeted management. In this study, we use a mechanistic species distribution model (SDM) to evaluate the current and future areas at risk of invasion by the common waxbill (Estrilda astrild), a widespread avian invader. Our model accurately predicts the species current range in Iberia and identifies additional climatically suitable areas, particularly in southern and western Europe. Under warming scenarios of +2 {degrees}C and +4 {degrees}C, suitable areas expand northwards, with over two-thirds of Europe classified as suitable under the most extreme scenario. These results suggest that the species is already operating near the cold limits of its thermal niche in parts of its invasive range, and that rising temperatures may remove these constraints, allowing expansion into previously unsuitable areas. Our findings demonstrate the power of mechanistic models in identifying regions at risk of colonisation and underscore the importance of early intervention and targeted monitoring in areas projected to become suitable.

ecology↗

bioRxiv2025

Weak evaporative cooling capacity and body size shape thermal limits in tropical montane forest birds

Climate warming and forest fragmentation threaten tropical biodiversity by altering microclimates and narrowing the range of temperatures within which species can maintain optimal physiological performance. We investigated the thermoregulatory capacities of five forest-dependent bird species from the Taita Hills (Kenya), a montane biodiversity hotspot experiencing severe habitat loss. Using respirometry, we measured resting metabolic rate (RMR) across a range of temperatures to determine thermoneutral zone (TNZ) limits, quantified evaporative water loss (EWL), evaporative heat loss (EHL), and metabolic heat production (MHP) as proxies of cooling capacity, and estimated heat tolerance limits (HTLs). Contrary to expectations of a classical TNZ pattern, RMR-temperature relationships were predominantly V-shaped, suggesting the absence, or marked narrowness, of a TNZ. In contrast, HTL clearly increased with body mass, with larger species tolerating higher temperatures. Evaporative cooling efficiency remained weak across all species (EHL/MHP < 1), indicating limited capacity to dissipate metabolic heat. Compared with global data, the Taita Hills species exhibited low critical temperatures and narrow thermal ranges, consistent with specialisation to the stable microclimates of tropical montane forests. Our findings suggest that small-bodied, forest-dependent tropical birds function within narrow thermal margins, which may make them especially vulnerable to rising temperatures and the microclimatic changes associated with climate change and forest fragmentation.

ecology↗

bioRxiv2025

Avian influenza causes age-related mortality in a long-lived seabird

Recently, highly pathogenic avian influenza (HPAI) A (H5N1) clade 2.3.4.4b viruses have caused mass mortality events in seabirds worldwide, raising concern for long-lived species with low reproductive rates. Using individual-level data from the 2022 mass mortality event in northwestern European Sandwich terns (Thalasseus sandvicensis), we show that older individuals were disproportionately more affected, while no sex bias was observed. This age-specific mortality likely removed the most experienced individuals from the population. Our findings highlight a previously underappreciated mechanism through which HPAI outbreaks may impair the resilience of long-lived avian populations.

ecology↗

bioRxiv2025

Metabolic responses at sub-thermoneutral temperatures in captive common waxbills (Estrilda astrild)

Understanding how endotherms manage energy expenditure at sub-thermoneutral temperatures is crucial for predicting their physiological flexibility and adaptive potential. This study investigated the metabolic responses of captive-bred common waxbills (Estrilda astrild) to decreasing ambient temperatures, with a focus on three questions: whether basal metabolic rate (BMR) predicts standard metabolic rate (SMR), how consistent individual metabolic responses are, and whether waxbills employ cold-induced energy-saving mechanisms. We found that BMR did not reliably predict SMR, underscoring the limits of BMR as a proxy under ecologically relevant conditions. SMR showed moderate repeatability across individuals, but variation was mainly due to baseline metabolic level rather than slope differences in thermal reaction norms. A two-breakpoint model best described the relationship between temperature and metabolic rate, with a marked decline in SMR below ~18.8{degrees}C. This decrease, along with observed reductions in core body temperature in some individuals, reveals an energy-saving strategy involving shallow hypothermia at relatively mild sub-thermoneutral temperatures. These findings suggest that energy-saving mechanisms may be intrinsic to the species rather than purely plastic responses. Overall, our results highlight both the limitations of BMR and the importance of measuring metabolic responses across thermal gradients to detect subtle but ecologically relevant hypometabolic strategies.

ecology↗

bioRxiv2025

Early-life social instability affects aggression, but not response inhibition, in chickens

Living in complex social environments presents behavioural and cognitive challenges. A key challenge is the regulation of aggression, which may be facilitated by response inhibition, the ability to suppress inappropriate actions. In more complex social environments, greater variability in interactions may increase demands for aggression regulation, promoting the development of response inhibition. However, social instability, a form of complexity characterised by frequent changes in group composition, can elevate aggression and may instead impair inhibition. To test these competing predictions we raised 144 chickens (Gallus gallus domesticus) in either stable or unstable social groups for five weeks. We observed the aggression within their enclosures following the final manipulation, and assessed their response inhibition using a thwarting task and a cylinder task. Unstable groups initially showed more aggression than stable groups following regrouping, but this declined rapidly to the same lower level of aggression as the stable groups. Contrary to our predictions, there were no differences between birds raised in stable and unstable groups for any measure of response inhibition, and individual variation in aggression did not correlate with inhibitory performance. These findings suggest that social instability influences aggression but does not affect the development of response inhibition in chickens, highlighting the potential context- and species-specific nature of social effects on cognition.

animal behavior and cognition↗

bioRxiv2025

Multitaxon assessment reveals inconsistent biodiversity responses to forest structural complexity in temperate forests

Increasing forest structural complexity is a key objective of future-proof forest management, with potential benefits for biodiversity. However, empirical evidence for consistent biodiversity-structure relationships across taxa is still limited. We investigated whether structurally more complex forests support greater species richness and higher multidiversity across taxonomic and functional groups in 19 mature forest plots in Flanders, Belgium. As one of the most densely populated and urbanized regions in Europe, with limited and highly fragmented forest cover, Flanders provides a particularly informative and policy-relevant context to test structure-biodiversity relationships. Its forests, often dominated by a few tree species and subject to long-term anthropogenic pressures and management, represent a realistic gradient of structural complexity. Structural complexity was quantified using a Structural Complexity Index (SCI), and biodiversity was assessed using a multidiversity index integrating scaled species richness across five taxonomic and seven arthropod functional groups. Using mixed-effects models and multivariate Bayesian analyses, we tested both direct effects of SCI on biodiversity and the covariation in species richness among groups. Contrary to expectations, SCI was not a consistent predictor of multidiversity, and most groups showed weak or inconsistent responses. These findings might suggest that structural complexity alone may be insufficient to enhance biodiversity in simplified forests. HighlightsO_LIForest structural complexity does not consistently predict biodiversity. C_LIO_LIResponses vary among taxonomic and functional groups. C_LIO_LICross-taxon congruence in diversity is limited and scale-dependent. C_LIO_LIKeywords: Forest structural complexity; Multidiversity, Species richness; Functional groups; Sustainable forest management C_LI

ecology↗

bioRxiv2025

Evaluating wildlife rehabilitation: Successful return of rehabilitated gulls in the wild

The expansion of human activities has increased the need for animal rehabilitation, especially for urban-breeding species such as herring gulls (Larus argentatus) and lesser black-backed gulls (L. fuscus), which now commonly nest on buildings and industrial sites. This study evaluates rehabilitation effectiveness by comparing survival and post-release reintegration, measured through habitat use and the degree of association with human-dominated environments, between rehabilitated and wild juvenile gulls along the Belgian coast. From 2012 to 2023, 3443 juveniles were ringed and monitored. Estimated survival rates varied significantly with age, but there was no difference between rehabilitated and wild birds. Differences in habitat use and association with local human population density were largely confined to juveniles: rehabilitated juveniles were resighted more often in rural green areas with lower human population densities, with patterns converging in older age classes. Our results suggest rehabilitation can support urban gull populations by yielding wild-like survival and space use.

ecology↗

bioRxiv2024

To Peck or Not To Peck: The influence of early-life social environment on response inhibition and impulsive aggression in Japanese quails

Deficits in response inhibition (i.e., the ability to suppress inappropriate responses) may contribute to increased impulsive aggression (i.e., unplanned behaviors that harm others). Since early-life environment might influence the development of response inhibition, it could also indirectly affect impulsive aggression. However, this relationship has rarely been directly examined. Here, we investigated whether response inhibition is associated with impulsive aggression and whether this relationship explains the effects of early-life social environments on impulsive aggression in juvenile Japanese quails (Coturnix japonica). Quails (n = 120) were raised in two social conditions: Small groups of five birds or Large groups of 15 birds. Response inhibition was assessed using the Barrier and Cylinder tasks, while impulsive aggression was measured in two contexts - within a group of five familiar individuals and in a dyad with an unfamiliar individual. We found that some aspects of response inhibition were related to impulsive aggression. Furthermore, quails reared in small groups showed significantly poorer response inhibition than those reared in large groups. Yet, impulsive aggression did not significantly differ between the two conditions. These findings suggest that, while impulsive aggression is partly related to response inhibition, other factors mitigate the effects of early social environments on its expression.

animal behavior and cognition↗

bioRxiv2024

Ixodes ricinus nymphs prefer blood with Borrelia infection and low corticosteroid concentration

Ticks play a significant role in the transmission of various pathogens, impacting both human and animal health. Understanding the factors influencing tick feeding preferences is crucial for mitigating the risk of tick-borne diseases. This study investigates the blood preference of Ixodes ricinus nymphs, focusing on host species, stress hormone levels (glucocorticoids), and the presence of Borrelia burgdorferi bacteria. Three series of in vitro experiments were conducted. The setup involved placing individual blood drops (15 {micro}l) on filter paper over a 37{degrees}C plate. Ticks were placed in the center, and their movements were tracked for two minutes to record preferences. The first experiment evaluated the ticks preference for blood from different hosts (mouse, bird, sheep). The second experiment explored the role of stress hormones by assessing the ticks response to blood with varying levels of supplemented cortisol and corticosterone (0, 10, 100 and 1000 ng/ml). The third experiment examined the potential influence of Borrelia infection, combined with elevated stress hormone levels, on blood preference. Our results show that I. ricinus nymphs show a significant preference for blood without added glucocorticoids and, in mice, blood with Borrelia infection. No clear preference for a specific host species was observed. These findings provide valuable insights into the complex interactions between ticks, blood characteristics, and Borrelia infection status, highlighting the potential importance of host physiological state in tick host selection. Future studies should explore the mechanisms behind these preferences, which could lead to the development of new methods to control the spread of tick-borne diseases. HIGHLIGHTSO_LIIn vitro experiments with nymphs can reveal insights into their blood preferences C_LIO_LITicks displayed no difference in preference towards bird, mouse, or sheep blood C_LIO_LITicks prefer blood with baseline stress levels over increased stress levels C_LIO_LIMouse blood infected with Borrelia burgdorferi was preferred by ticks C_LI

ecology↗

bioRxiv2024

Early-Life Group Size Does Not Influence Japanese Quails' Learning in a Response Inhibition Task

In complex social environments, animals benefit from suppressing inappropriate responses (known as Response Inhibition - RI) to avoid conflicts and maintain group cohesion. Recent research suggests that an individuals early-life social environment can shape their RI. However, these findings have mostly been correlational, and results vary across species. Furthermore, the role of learning is often overlooked when measuring RI, despite its potential importance to understanding group differences. We investigated the effect of early-life group size, a key determinant of social complexity, on RI in Japanese quails (Coturnix japonica), whilst taking the role of learning into account. Quails (n = 120) were raised in either small groups of five or large groups of 15 individuals. RI was assessed using the cylinder task. Up to 10 trials were administered to assess whether the birds responses changed with increasing experience of the task. Among the quails that completed 10 trials, we found that those raised in large groups consistently spent less time pecking the cylinder than those raised in small groups. The quails responses were also influenced by their body condition, food motivation, and sex. Importantly, the quails learned to inhibit their responses - successful trials increased, and time spent pecking the cylinder decreased, across 10 trials. However, learning rates did not differ between the treatment groups. These findings suggest that early-life social group size promotes the development of RI in quails, but not their learning during the cylinder task.

animal behavior and cognition↗

bioRxiv2024

Beyond a unitary construct: Dissecting stopping behaviour in two bird species

The ability to stop behaviour is essential for adapting to changes in the environment, a principle that holds true across various species. While traditionally considered a unitary psychological construct, recent studies indicate that this ability is multifaceted. Our research evaluates this multifaceted nature using three tasks that measure stopping in different contexts in two related gull species: herring gulls (Larus argentatus) and lesser black-backed gulls (L. fuscus). These species were selected for their distinct migration and foraging strategies, offering a unique lens through which to examine behavioural adaptations. Across tasks and species, we conceptualised stopping as a race between a go and a stop runner, and predicted correlations based on the type of stop stimulus, the relative timing of the go and the stop stimuli, and the type of action that needed to be stopped. We found correlations between measures of going across tasks, but there was less consistency in measures of stopping. Furthermore, we observed significant differences in going and stopping behaviours that were specific to each species, which may be linked to their migration and foraging strategies. These findings highlight the importance of considering the multifaceted nature of stopping in evolutionary and behavioural studies.

animal behavior and cognition↗

bioRxiv2024

Metabolic responses to cold: thermal physiology of native common waxbills (Estrilda astrild)

Ecophysiological studies of invasive species tend to focus on captive individuals and their invasive range. However, the importance of gaining a thorough understanding of their physiology in their native range, where autecological knowledge is limited, has played a crucial role in assessing species ecophysiological responses to the often novel environmental conditions encountered in their invasive range. Here, we investigated the ecophysiological characteristics of a population of the wild-caught common waxbill (Estrilda astrild), a successful global invader, in part of its native range (South Africa). We investigated how this species adjusts its resting metabolic rate over a range of temperatures to identify its thermoneutral zone (TNZ) as an indicator of a species thermal tolerance. The observed TNZ curve predominantly followed the classic Scholander-Irving model, with metabolic rates increasing linearly at temperatures outside the TNZ. However, we found an inflection point at moderately cold temperatures (16{degrees}C) where the common waxbill began to decrease its metabolic rate. This finding highlights the potential use of an energy-saving strategy as an adaptive response to cold, such as facultative hypothermic responses through a reduction in body temperature, which may explain their success as an invasive species. We argue that although metabolic infection points have been repeatedly identified in studies of TNZ, the specific mechanisms behind metabolic down-regulation at low temperatures remain underexplored in the literature. We therefore suggest that future research should focus on investigating body temperature variation, with particular emphasis on its potential contribution to metabolic adaptation in colder environments.

ecology↗

bioRxiv2023

Metabolic adjustments to winter severity in two geographically separated great tit (Parus major) populations

Understanding the potential limits placed on organisms by their ecophysiology is crucial for predicting their responses to varying environmental conditions. Studies to date have traditionally relied on between-species comparisons, however, recently, there has been a growing recognition of the importance of intraspecific variation in shaping an organisms ecological and physiological responses. In this context, widely distributed resident bird species offer a well-suited study system to examine intraspecific geographical variation in ecophysiological traits. A main hypothesis for explaining avian thermoregulatory mechanisms is the aerobic capacity model, which posits a positive correlation between basal (BMR) and summit (Msum) metabolism, caused by the energetic maintenance costs associated with increased muscle mass for shivering thermogenesis and enhanced investment in digestive organs for food processing. Most evidence for this hypothesis, however, comes from interspecific comparisons only, and the ecophysiological underpinnings of avian thermoregulatory capacities hence remain controversial. Here, we focus on great tits (Parus major), measuring winter BMR and Msum in two populations from different climates, a maritime-temperate (Gontrode, Belgium) and a continental (Zvenigorod, Russia) one. We test for the presence of intraspecific geographical variation in metabolic rates and assess the predictions following the aerobic capacity model. We found that metabolic rates differed between populations, whereby the birds from the maritime-temperate climate (Gontrode) showed higher (whole-body and mass-independent) BMR whereas conversely, great tits from Zvenigorod showed higher levels of both (whole-body and mass-independent) Msum. Within each population, our data did not fully support the aerobic capacity models predictions. We argue that the decoupling of BMR and Msum observed may be caused by different selective forces acting on these metabolic rates, with birds from the continental-climate Zvenigorod population facing the need to conserve energy for surviving long winter nights (by keeping their BMR at low levels) while simultaneously being able to generate more heat (i.e., a high Msum) to withstand cold spells. We argue that the coupling or uncoupling of basal and maximum metabolic rates at the intraspecific level is likely influenced by different selective pressures that shape local adaptations in response to different climate regimes.

ecology↗

bioRxiv2023

Seasonal variation in great tit (Parus major) energy requirements: reallocation versus increased demand

Understanding how birds annually allocate energy to cope with changing environmental conditions and physiological states is a fundamental question in avian ecology. The two main hypotheses to explain annual patterns in energy use are "reallocation" and "increased demand". The reallocation hypothesis suggests equal energetic costs in winter and breeding seasons, while the increased demand suggests that energy demand should be highest during breeding. Under the standard aerobic capacity model of endothermy, birds are expected to adjust the mass and/or metabolic intensity of their bodies in ways that are consistent with expected cold- and/or activity-induced costs. Here, we look for metabolic signatures of reallocation versus increased demands in the energy requirements of a small, resident passerine of a temperate-zone (great tit, Parus major). To do so, we measured whole-body and mass-independent basal (BMR), summit (Msum), and field (FMR) metabolic rates during late winter and during the chick-rearing period (breeding). We also assessed whether, and to what extent, metabolic rates conform to the predictions of the aerobic capacity model of endothermy. We found that great tits showed no substantial differences in energy expenditure between winter and the breeding season, providing support for the reallocation hypothesis. Only mass-independent Msum showed seasonal variation, with significantly higher values ([~]4%) in winter compared to the breeding season. Our results also lend support to the predictions of the aerobic capacity model for the evolution of endothermy, as we found that whole-body BMR and Msum were positively related. We argue that both energy reallocation and the limited increase in mass-independent Msum are consistent with the relatively mild winter temperatures recorded during our study period. Our results confirm that both BMR and Msum are flexible traits that vary in ways that are consistent with expected cold- and/or activity-induced costs.

ecology↗

bioRxiv2020

Host-pathogen co-existence incurs reproductive costs

Widespread endemism of host-adapted pathogens poses a heavy burden on animal and human health. Mechanisms underpinning long-term host pathogen co-existence and concurrent costs are poorly understood. We use infections in pigeons with pathogenic, pigeon adapted Salmonella Typhimurium to explain how host and pathogen trade-offs and benefits sustain long-term pathogen endemism. An experimentally infected group of pigeons that was studied for 15 months showed that pathogen persistence decreased host condition and reproductive success, but conferred protection against Salmonella-induced clinical disease. The relevance of these findings was confirmed in nature, where this pathogen was shown to widely occur in feral pigeons (Columba livia), yet without clinical disease. Pathogen transmission and long-term persistence were associated with intermittent faecal shedding, which markedly increased during crop feeding and natural stress periods. Exploiting host specific traits in the presence of protective host population immunity thus facilitates long-term co-existence, be it at a significant reproductive cost.

microbiology↗

bioRxiv2020

Body size and tree species composition determine variation in prey consumption in a forest-inhabiting generalist predator

Trophic interactions may strongly depend on body size and environmental variation, but this prediction has been seldom tested in nature. Many spiders are generalist predators that use webs to intercept flying prey. The size and mesh of orb webs increases with spider size, allowing a more efficient predation on larger prey. We studied to this extent the orb-weaving spider Araneus diadematus inhabiting forest fragments differing in edge distance, tree diversity and tree species. These environmental variables are known to correlate to insect composition, richness and abundance. We anticipated these forest characteristics to be a principle driver of prey consumption. We additionally hypothesised them to impact spider size at maturity and expect shifts towards larger prey-size distributions in larger individuals independently from the environmental context. We quantified spider diet by means of metabarcoding of nearly 1000 A. diadematus from a total of 53 forest plots. This approach allowed a massive screening of consumption dynamics in nature, though at the cost of identifying the exact prey identity, as well as their abundance and putative intraspecific variation. Our study confirmed A. diadematus as a generalist predator, with more than 300 prey ZOTUs detected in total. At the individual level, we found large spiders to consume fewer different species, but adding larger species to their diet. Tree species composition affected both prey species richness and size in the spiders diet, although tree diversity per se had no influence on the consumed prey. Edges had an indirect effect on the spider diet as spiders closer to the forest edge were larger and therefore consumed larger prey. We conclude that both intraspecific size variation and tree species composition shape the consumed prey of this generalist predator.

ecology↗

bioRxiv2020

Genome Report: De novo genome assembly and annotation for the Taita white-eye (Zosterops silvanus)

The Taita White-eye (Zosterops silvanus) is an endangered songbird endemic to the Taita Hills of Southern Kenya, where it is confined to small areas of fragmented forest. With diversification rates exceeding those reported in most other vertebrates, White-eyes are a prime example of a great speciator. Nevertheless, we still know surprisingly little about the genomic underpinnings leading to this extraordinary fast radiation. Here, we present a draft genome assembly (ZSil_MB_1.0) for the Taita White-eye generated from a blood sample of a wild, female bird captured in the Taita Hills, Kenya. By performing a de novo assembly with linked-reads and annotation of the assembly with the MAKER pipeline, we generated a 1.069 Gb assembly with a scaffold N50 of 1.105 Mb and an L50 of 244. After quality evaluation of the assembly, we identified 92.1% of BUSCOs complete or fragmented, indicating that our de novo assembly is of high quality. This new assembly provides a genomic resource for future studies into the evolutionary and comparative genomics of this rapidly diversifying group of birds.

genomics↗