Roads are a major source of mortality for wildlife, particularly amphibians. Identifying vulnerable species and understanding any behavioral predictors of mortality helps us understand vulnerability to traffic and can inform management strategies. If anurans use roads to facilitate movement, thermoregulate, or feed, then standard mitigation methods may not be effective. We investigated a 9-species anuran community in tropical Australia with respect to behavioral responses on roads including proportion of time spent on roads, distances and direction moved along roads, and whether feeding was occurring on roads. We also noted if focal individuals were killed during observations, with the aim of assessing any link between mortality and on-road behavior or anuran size. We found no differences among species regarding behavior on roads, no evidence to suggest they use the road as a movement corridor, and no difference in road mortality among species. Our results indicate this anuran community is equally vulnerable to mortality via road traffic, indicating that actions to reduce mortality such as underpasses, signage, and speed restrictions in hotspots will benefit the entire community and thus have high cost-effectiveness.

Millions of animals are killed by vehicles on roads yearly, left mostly to rot, but these unfortunate mortalities may have a benefit to society that is not widely appreciated: they represent a valuable source of animals for study that does not require and could even replace the use of live wildlife. Here, we provide the first literature review to uncover validated uses for roadkill and, in doing so, encourage uptake of this valuable resource. We located 312 studies using roadkill whose aim included purposes other than enumerating or mitigating roadkill. We identified 26 broad-use and 91 specific-use categories of roadkill carcasses. Most common uses included assessing species presence or distribution, assessing parasite, disease or pathogen presence, assessing roadkill as an index of species abundance, describing species diet and lodging specimens in museums. The studies included at least 650 species; mammals dominated the studies, followed sequentially by reptiles, birds, amphibians and invertebrates. We discuss how we might better take advantage of this source of animals for study and highlight limitations and cautions in their use. Given the proven and diverse uses demonstrated in our review, we encourage the scientific community to now (re-)consider roadkill as an ethical alternative to live animal sampling.

Plasticity is a flexible response to environmental change. Although many studies show plastic responses to sustained increases in temperature, few investigate temporal changes in plasticity, especially under variable temperatures. We show that increasing temperature by 5 degrees C for just 2 days per week dramatically increased boldness in the ectotherm Armadillidium vulgare during the first exposure. Plasticity was reduced over the next 2 weeks, primarily because of large increases in boldness at the cooler reference temperature. After 2 weeks of reprieve from protocols some deacclimation occurred, as boldness was significantly reduced at the reference temperature in week 6. Individual variation in plasticity was evident in weeks 1 and 2, but not in the remaining weeks of exposure, suggesting rapid individual acclimation towards an assumed adaptive mean. Another form of behavioural flexibility, residual intraindividual variability, did not vary with time or temperature. The repeatability of individual behaviour was high at the cooler reference temperature, as was the repeatability of thermal plasticity and predictability, indicating that each aspect of their behavioural reaction norm is potentially heritable. Our study highlighted the complex interplay between inflexible (repeatable) individual differences in behaviour and flexible temporal changes in plasticity, highlighting their considerable adaptive capacity to thermal change and the importance of studying temporal dimensions of plasticity. (c) 2025 The Author(s). Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

Offspring sex ratio has been proposed as an indicator of the risk of developing certain cancers in humans, but offspring sex ratio may also be a consequence of the disease. In this study, we investigate this subject using the zebrafish, Danio rerio, as a model system. First, we explore whether inducing skin cancer at an early stage of the host's life (embryonic stage) has the potential to influence sex determination and/or sex-specific mortality. Second, we investigate whether the sex ratio in offspring produced by tumor-bearing adult females differs from that of healthy females. Third, we compare the survival (until sexual maturity) of offspring produced by cancerous and non-cancerous females. We found that skin cancer did not influence sex determination and the sex ratio of the offspring. However, consistent with previous studies on other model systems, the survival of offspring was higher when mothers were cancerous, suggesting that diseased females allocate more resources to current reproductive effort compared to their healthy counterparts. This study makes a significant contribution to our understanding of the ecological and evolutionary consequences of host-tumor interactions in animals.

Classic evolutionary theory predicts that predation will shift trait means and erode variance within prey species; however, several studies indicate higher behavioral trait variance and trait integration in high-predation populations. These results come predominately from field-sampled animals comparing low- and high-predation sites and thus cannot isolate the role of predation from other ecological factors, including density effects arising from higher predation. Here, we study the role of predation on behavioral trait (co)variation in experimental populations of guppies (Poecilia reticulata) living with and without a benthic ambush predator (Jaguar cichlid) to better evaluate the role of predation and where density was equalized among replicates twice per year. At 2.5 years after introduction of the predators (similar to 10 overlapping generations), 40 males were sampled from each of the six replicate populations and extensively assayed for activity rates, water column use, and latency to feed following disturbance. Individual variation was pronounced in both treatments, with substantial individual variation in means, temporal plasticity, and predictability (inverse residual variance). Predators had little effect on mean behavior, although there was some evidence for greater use of the upper water column in predator-exposed fish. There was greater variance among individuals in water column use in predator-exposed fish, and they habituated more quickly over time; individuals higher in the water column fed slower and had a reduced positive correlation with activity, although again this effect was time specific. Predators also affected the integration of personality and plasticity-among-individual variances in water column use increased, and those in activity decreased, through time-which was absent in controls. Our results contrast with the extensive guppy literature showing rapid evolution in trait means, demonstrating either increases or maintenance of behavioral variance under predation.

The inability to control cell proliferation results in the formation of tumors in many multicellular lineages. Nonetheless, little is known about the extent of conservation of the biological traits and ecological factors that promote or inhibit tumorigenesis across the metazoan tree. Particularly, changes in food availability have been linked to increased cancer incidence in humans, as an outcome of evolutionary mismatch. Here, we apply evolutionary oncology principles to test whether food availability, regardless of the multicellular lineage considered, has an impact on tumorigenesis. We used two phylogenetically unrelated model systems, the cnidarian Hydra oligactis and the fish Danio rerio , to investigate the impact of resource availability on tumor occurrence and progression. Individuals from healthy and tumor-prone lines were placed on four diets that differed in feeding frequency and quantity. For both models, frequent overfeeding favored tumor emergence, while lean diets appeared more protective. In terms of tumor progression, high food availability promoted it, whereas low resources controlled it, but without having a curative effect. We discuss our results in light of current ideas about the possible conservation of basic processes governing cancer in metazoans (including ancestral life history trade-offs at the cell level) and in the framework of evolutionary medicine.

The presence of doubly uniparental inheritance (DUI) in bivalves represents a unique mode of mitochondrial transmission, whereby paternal (male-transmitted M-type) and maternal (female-transmitted F-type) haplotypes are transmitted to offspring separately. Male embryos retain both haplotypes, but the M-type is selectively removed from females. Due to the presence of heteroplasmy in males, mtDNA can recombine resulting in a 'masculinized' haplotype referred to as Mf-type. While mtDNA recombination is usually rare, it has been recorded in multiple mussel species across the Northern Hemisphere. Given that mitochondria are the powerhouse of the cell, different mtDNA haplotypes may have different selective advantages under diverse environmental conditions. This may be particularly important for sperm fitness and fertilization success. In this study we aimed to i) determine the presence, prevalence of the Mf-type in Australian blue mussels (Mytilus sp.) and ii) investigate the effect of Mf-mtDNA on sperm performance (a fitness correlate). We found a high prevalence of recombined mtDNA (≈35 %) located within the control region of the mitochondrial genome, which occurred only in specimens that contained Southern Hemisphere mtDNA. The presence of two female mitotypes were identified in the studied mussels, one likely originating from the Northern Hemisphere, and the other either representing the endemic M. planulatus species or introduced genotypes from the Southern Hemisphere. Despite having recombination events present in a third of the studied population, analysis of sperm performance indicated no difference in fertilization success related to mitotype.

Abstract Cancer is a disease that affects the control of cell proliferation in many multicellular lineages. Nonetheless, little is known about the extent of conservation of the biological traits and ecological factors that promote or inhibit tumorigenesis across the metazoan tree. Particularly, changes in food quantity and quality have been linked to increased cancer incidence in humans, an outcome of evolutionary mismatch. Here, we apply evolutionary ecology principles to test the hypothesis whether food availability, regardless of the multicellular lineage considered, should govern tumorigenesis. We used two phylogenetically unrelated model systems, namely the cnidarian Hydra oligactis and the fish Danio rerio to investigate the impact of resource availability on tumor emergence and progression. Individuals from healthy and tumor-prone lines were placed on four diets that differed in feeding frequency and quantity. For both models, frequent overfeeding favored tumor emergence, while lean diets appear more protective. When investigating tumor progression, high food availability promoted it, whereas low resources controlled it, but without curing the animals. We discuss our results in light of current ideas about the possible conservation of basic processes governing cancer in metazoans (including ancestral life history trade-offs at the cell level) and in the framework of evolutionary medicine.

Torpor, a controlled reduction in metabolism and body temperature, reduces energy expenditure substantially. However, torpor expression in wild passerines is currently understudied. We show that skin temperature (Ts) of resting White-throated Treecreepers (N = 4) fell by 5 °C on average in both summer and winter, independent of ambient temperature, but we could not confirm torpor use (Ts reduction > 5 °C). It is possible that roosting in tree hollows provides sufficient insulation to minimise energy loss, or torpor is used only during extreme conditions. Further studies are needed to characterise the physiological flexibilities of species and, therefore, their capability to cope with changing environmental conditions.

Grasslands are globally threatened and their biodiversity, including grassland birds, is declining markedly. To inform grassland bird conservation globally, we systematically reviewed threats and conservation actions for grassland birds, extracting data from 528 papers. Across the 10 primary grassland regions of the globe, agriculture was the most frequently or joint most frequently reported threat in nine regions (reported as a threat in 73% of publications); hunting was the most frequently reported threat in the remaining region. Natural system modifications (reported as a threat in 32% of publications) and climate change and severe weather (24%) were less frequently reported threats compared with agriculture. The types of threat from agriculture varied regionally, but the most pervasive were livestock farming and ranching (reported in 58% of publications where agriculture was a primary threat) and non-timber cropping (43%). Most agricultural threats relate to intensification, but agricultural abandonment, typically the cessation of grazing, sometimes accompanied by tree planting/succession, poses an emerging threat to some grassland birds (reported in 32% of publications where agriculture was a primary threat). The most frequent conservation actions implemented to date include land/water management and protection, and species-specific management actions. Authors of reviewed publications in almost all regions recommend more land/water management, followed by calls for further land/water protection. The parlous state of grassland birds globally suggests that existing conservation actions for grasslands are inadequate. Furthermore, our review suggests that these should be primarily targeted at reversing the negative impacts of agriculture, in particular livestock farming and cropping.

In recent years, many studies have investigated the potential state dependence of individual differences in behaviour, with the aim to understand the proximate and ultimate causes and consequences of animal personality. Among the potential state variables that could affect behavioural expression is size and mass, but few studies have found associations at the among-individual levels. Insufficient sampling and incorrect analysis of data are cited as impediments to detecting correlations, if they exist. Here, we conducted a study using 100 pillbugs ( Armadillidium vulgare ) and assayed their defensive behaviour 24 times each over time and across familiarity contexts, to test the asset protection hypothesis that predicts a negative correlation between boldness and mass, and with increases in mass over time. Multivariate mixed models revealed that despite mostly consistent individual behavioural differences over time (modest slope variance) and across contexts (near-parallel reaction norms), and 18-fold range in starting mass, there was no correlation between individual mean mass and boldness. However, individuals that gained more mass over time may have been more ‘shy’ compared to those gaining less mass, but the correlation was weak and observed variation in mass gain was small. There was also a mean level trend of increasing shyness over time that was coincident with mean level mass increases over time. Together, our study provides weak evidence for the asset protection hypothesis, whereby individuals that accumulate more resources are thought to protect them through risk averse behaviour. Significance statement Individual variation in ‘state’, such as mass or energy reserves, is thought to be a predictor of individual differences in behaviour that are consistent over time. However, few studies reveal such links, and several studies suggest insufficient sampling may explain null results in most studies. We studied 100 animals sampled 24 times each in a controlled setting to reveal stable individual differences in mean behaviour over time and across contexts; however, individual behaviour was unrelated to large differences in individual mass but weakly related to increases in mass through time whereby individuals became more shy and those growing faster were somewhat more shy. Our results provide little evidence for the asset protection hypothesis.

Reproduction is one of the most energetically demanding life-history stages. As a result, breeding individuals often experience trade-offs, where energy is diverted away from maintenance (cell repair, immune function) toward reproduction. While it is increasingly acknowledged that oncogenic processes are omnipresent, evolving and opportunistic entities in the bodies of metazoans, the associations among reproductive activities, energy expenditure, and the dynamics of malignant cells have rarely been studied. Here, we review the diverse ways in which age-specific reproductive performance (e.g., reproductive aging patterns) and cancer risks throughout the life course may be linked via trade-offs or other mechanisms, as well as discuss situations where trade-offs may not exist. We argue that the interactions between host–oncogenic processes should play a significant role in life-history theory, and suggest some avenues for future research.

Behavioural studies have shown that even after accounting for individual differences in contextual and temporal plasticity, considerable unexplained (residual) variation remains. Recent studies show that individuals differ in the magnitude of residual variation (=their predictability), but hardly any studies exist that assess whether this individual attribute itself is repeatable and potentially subject to selection, and whether predictability is related to aspects of different underlying state variables. Using data on the latency to emerge after disturbance of 100 pill bugs, Armadillidium vulgare, measured 24 times each over time and across contexts, we found substantial among-individual variation in mean boldness (latency) and in their behavioural predictability. Individual mean boldness across weeks was highly consistent over time, as was individual predictability; by contrast, unadjusted repeatability of boldness scores (the familiar ‘intraclass correlation’) and repeatability adjusted for time-related behavioural changes were low to moderate, indicating substantial residual variation. Individual mean boldness was not related to individual predictability, indicating that while selection can potentially act on individual means and individual variances, correlated selection is unlikely, for the traits assessed. Neither boldness nor predictability in boldness was related to mass or to sex, nor did they vary over time concurrent with gains in mass under ad libitum food conditions and in experience with the behavioural assay, indicating they were not clearly related to these potentially important life history and state variables.

Researchers often use artificial models of animals to elicit and study behavior. Until recently, these models were typically handcrafted; however, 3D-printing technology has been adopted by researchers looking to create accurate and consistent animal models from scans of living animals, taxidermies, or existing models. While 3D-printing techniques create models with accurate and repeatable shape and size, applying coloration to these models is still typically achieved with traditional methods, such as painting by hand. These approaches can be time-consuming and require high levels of artistic skill, creating a barrier to producing realistic models, especially when more than one model or standardized coloration is required. Here, we present a simple workflow to avoid these issues by creating a photograph-accurate paper "skin" that can be glued onto 3D-printed animal models to provide surface coloration. We have used this methodology to create avian models for several experiments, and found that it can create highly detailed and standardized models with minimal training and is independent of artistic skill. Additionally, this method allows the files needed to accurately recreate models to be shared digitally with other researchers, further enhancing repeatability in the field.

Energy expenditure (EE) is generally viewed as tumorigenic, due to production of reactive oxygen species (ROS) that can damage cells and DNA. On this basis, individuals within a species that sustain high EE should be more likely to develop cancer. Here, we argue the opposite, that high EE may be net protective effect against cancer, despite high ROS production. This is possible because individuals that sustain high EE have a greater energetic capacity (=greater energy acquisition, expenditure and ability to up-regulate output), and can therefore allocate energy to multiple cancer-fighting mechanisms with minimal energetic trade-offs. Our review finds that individuals sustaining high EE have greater antioxidant production, lower oxidative stress, greater immune function and lower cancer incidence. Our hypothesis and literature review suggest that EE may indeed be net protective against cancer, and that individual variation in energetic capacity may be a key mechanism to understand the highly individual nature of cancer risk in contemporary human populations and laboratory animals. Lay summary The process of expending energy generates reactive oxygen species that can lead to oxidative stress, cell and DNA damage, and the accumulation of this damage is thought to be a major contributor to many ageing related diseases that include cancer. Here, we challenge this view, proposing how and why high energy expenditure (EE) may actually be net protective against cancer, and provide literature support for our hypothesis. We find individuals with high sustained EE have greater energetic capacity and thus can invest more in repair to counter oxidative stress, and more in immune function, both of which reduce cancer risk. Our hypothesis provides a novel mechanism to understand the highly individual nature of cancer, why taller individuals are more at risk, why physically active individuals have lower cancer risk, and why regular exercise can reduce cancer risk.

Accumulation of lipid reserves is considered important for the overwinter survival of many animals. Fish are thought to deplete lipids until they reach a critical minimum below which starvation mortality occurs, meaning that lipid-dependent selective overwinter mortality may be a strong selective pressure leading to life-history evolution favouring lipid accumulation and storage. Much of our current knowledge comes from either laboratory studies or field studies that are not well controlled, but rarely is overwinter survival directly estimated to evaluate selective mortality. Here, we studied patterns of lipid storage, overwinter lipid depletion, and subsequent survival of a single strain of rainbow trout (Oncorhynchus mykiss) stocked into experimental lakes that differed in productivity but experienced the same local winter conditions. Productive lakes produced trout with higher lipid content and steeper allometric slopes in contrast with trout in low food lakes; however, these field-based values were all substantially lower than those determined in the lab. Surviving trout from low productivity lakes emerged from winter in poor condition, close to the expected critical minimum needed for survival, in comparison with survivors from higher-productivity lakes. As expected, overwinter mortality was lipid-dependent, with fish in low food lakes nearing 90% mortality and about 60% mortality in high food lakes. Importantly, these estimates are higher than from laboratory (∼70%) and modelling studies (0% to 14%) for this species. These results, though from stocked populations, suggest winter mortality is an even stronger selective pressure than previously thought, creating a tight population bottleneck in young fish cohorts and likely promoting life-history strategies that favour energy storage at the expense of somatic growth.

ABSTRACT Robins in the family Petroicidae are characteristic of the woodland bird community that is threatened in Australia as a result of habitat loss and fragmentation. Flame Robin (Petroica phoenicea) populations declined by 56% between 1980 and 2000, with habitat loss likely being the primary cause. Given that Flame Robins primarily breed at high elevation, populations may become more isolated due to anthropogenic change, resulting in increased inbreeding and loss of genetic diversity that may accelerate local extinction. We estimated the genetic structure and recent gene flow among four populations (n = 70 birds) of this vulnerable (NSWSC) species across a 670 km portion of its range in temperate south-eastern Australia using 14 genetic markers. We found no significant differences in genetic diversity amongst populations and little population structuring – only the northernmost population showing a weak signal of differentiation. However, we detected little recent migration between the northern and southern sites, possibly due to recent fragmentation. We conclude that habitat loss is a conservation concern for this Vulnerable species and further work and ongoing genetic monitoring is needed, particularly given high elevation breeding sites that are vulnerable in the face of a changing climate.

Behavioral and physiological ecologists have long been interested in explaining the causes and consequences of trait variation, with a focus on individual differences in mean values. However, the majority of phenotypic variation typically occurs within individuals, rather than among individuals (as indicated by average repeatability being less than 0.5). Recent studies have further shown that individuals can also differ in the magnitude of variation that is unexplained by individual variation or environmental factors (i.e., residual variation). The significance of residual variation, or why individuals differ, is largely unexplained, but is important from evolutionary, methodological, and statistical perspectives. Here, we broadly reviewed literature on individual variation in behavior and physiology, and located 39 datasets with sufficient repeated measures to evaluate individual differences in residual variance. We then analyzed these datasets using methods that permit direct comparisons of parameters across studies. This revealed substantial and widespread individual differences in residual variance. The magnitude of individual variation appeared larger in behavioral traits than in physiological traits, and heterogeneity was greater in more controlled situations. We discuss potential ecological and evolutionary implications of individual differences in residual variance and suggest productive future research directions.

Torpor is a controlled reduction of metabolism and body temperature, and its appropriate use allows small birds to adapt to and survive challenging conditions. However, despite its great energy conservation potential, torpor use by passerine birds is understudied although they are small and comprise over half of extant bird species. Here, we first determined whether a free-living, small ∼20 g Australian passerine, the eastern yellow robin ( Eopsaltria australis ), expresses torpor by measuring skin temperature (T s ) as a proxy for body temperature. Second, we tested if skin temperature fluctuated in relation to ambient temperature (T a ). We found that the T s of eastern yellow robins fluctuated during winter by 9.1 ± 3.9°C on average (average minimum T s 30.1 ± 2.3°C), providing the first evidence of torpor expression in this species. Daily minimum T s decreased with T a , reducing the estimated metabolic rate by as much as 32%. We hope that our results will encourage further studies to expand our knowledge on the use of torpor in wild passerines. The implications of such studies are important because species with highly flexible energy requirements may have an advantage over strict homeotherms during the current increasing frequency of extreme and unpredictable weather events, driven by changing climate.

Cellular cheating leading to cancers exists in all branches of multicellular life, favoring the evolution of adaptations to avoid or suppress malignant progression, and/or to alleviate its fitness consequences. Ecologists have until recently largely neglected the importance of cancer cells for animal ecology, presumably because they did not consider either the potential ecological or evolutionary consequences of anticancer adaptations. Here, we review the diverse ways in which the evolution of anticancer adaptations has significantly constrained several aspects of the evolutionary ecology of multicellular organisms at the cell, individual, population, species, and ecosystem levels and suggest some avenues for future research.