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Scholander-Irving curves describe the relationship between ambient temperature and metabolic rate and are fundamental to understanding the energetic demands of homeothermy. However, Scholander-Irving curves are typically measured in dry air, which is not representative of the humidity many organisms experience in nature. Consequently, it is unclear (1) whether Scholander-Irving curves (especially below thermoneutrality) are altered by humidity, given the effects of humidity on thermal properties of air, and (2) whether physiological responses associated with Scholander-Irving curves in the lab reflect organismal performance in humid field conditions. We used laboratory experiments and biophysical models to test the effects of humidity on the thermoregulatory physiology of tree swallows (Tachycineta bicolor). We also tested whether physiological responses measured under lab conditions were correlated with field body temperatures and nestling provisioning rates. We found that humidity reduced rates of evaporative water loss but did not have large effects on body temperature or metabolic rate, suggesting that swallows can decouple evaporative cooling, body temperature and metabolic rate. Although the effect of humidity on metabolic rate in the lab was small, our biophysical models indicated that energetic costs of thermoregulation were â¼8% greater in simulations that used metabolic rates from birds in humid compared with dry conditions. Finally, we found mixed evidence that physiological responses measured in the lab under humid or dry conditions were associated with body temperature and nest provisioning rates in the field. Our results help clarify the effect of humidity on endotherm thermoregulation, which may help forecast organismal responses to environmental change.
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Regulação da Temperatura Corporal , Umidade , Andorinhas , Animais , Regulação da Temperatura Corporal/fisiologia , Andorinhas/fisiologia , Metabolismo Basal/fisiologia , Modelos Biológicos , Metabolismo Energético , Comportamento de Nidação/fisiologia , Masculino , Temperatura Corporal/fisiologiaRESUMO
Behavioural thermoregulation has critical ecological and physiological consequences that profoundly influence individual fitness and species distributions, particularly in the context of climate change. However, field monitoring of this behaviour remains labour-intensive and time-consuming. With the rise of camera-based surveys and artificial intelligence (AI) approaches in computer vision, we should try to build better tools for characterizing animals' behavioural thermoregulation. In this study, we developed a deep learning framework to automate the detection and classification of thermoregulation behaviour. We used lizards, the Rough-tail rock agama (Laudakia vulgaris), as a model animal for thermoregulation. We colour-marked the lizards and curated a diverse dataset of images captured by trail cameras under semi-natural conditions. Subsequently, we trained an object-detection model to identify lizards and image classification models to determine their microclimate usage (activity in sun or shade), which may indicate thermoregulation preferences. We then evaluated the performance of each model and analysed how the classification of thermoregulating lizards performed under different solar conditions (sun or shade), times of day and marking colours. Our framework's models achieved high scores in several performance metrics. The behavioural thermoregulation classification model performed significantly better on sun-basking lizards, achieving the highest classification accuracy with white-marked lizards. Moreover, the hours of activity and the microclimate choices (sun vs shade-seeking behaviour) of lizards, generated by our framework, are closely aligned with manually annotated data. Our study underscores the potential of AI in effectively tracking behavioural thermoregulation, offering a promising new direction for camera trap studies. This approach can potentially reduce the labour and time associated with ecological data collection and analysis and help gain a deeper understanding of species' thermal preferences and risks of climate change on species behaviour.
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Environmental temperatures are increasing worldwide, threatening desert ectotherms already living at their thermal limits. Organisms with flexible thermoregulatory behaviours may be able to mitigate the effects of extreme temperatures by moving among microhabitats, yet little work has tracked movement patterns of desert ectotherms in the wild over diurnal scales or compared behaviour among seasons. Here, we used camera traps to track the thermoregulatory behaviour and microhabitat choices of 30 desert lizards (Messalina bahaldini) in custom, outdoor arenas that provided access to open, rock, and bush microhabitats. We found that in the summer, lizards preferred to move to the shaded microhabitats and remain there under warmer conditions. During winter, however, lizards' activity was not related to temperature, and lizards mostly chose to remain in the open habitat. Interestingly, in both seasons, lizards tended to remain in their current microhabitat and moved infrequently between certain combinations of microhabitats. Our study shows that thermoregulation (shade-seeking behaviour) is a major factor during summer, helping lizards to avoid extreme temperatures, but not during winter, and shows a novel effect of current microhabitat on movement, suggesting that other biotic or abiotic factors may also drive microhabitat choice. Understanding the complex factors at play in microhabitat choice is critical for developing conservation programs that effectively mitigate the negative impacts of climate change on desert animals.
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Regulação da Temperatura Corporal , Clima Desértico , Lagartos , Estações do Ano , Animais , Lagartos/fisiologia , Ecossistema , Comportamento Animal , Movimento , MasculinoRESUMO
Worldwide habitat loss, land-use changes, and climate change threaten biodiversity, and we urgently need models that predict the combined impacts of these threats on organisms. Current models, however, overlook microhabitat diversity within landscapes and so do not accurately inform conservation efforts, particularly for ectotherms. Here, we built and field-parameterized a model to examine the effects of habitat loss and climate change on activity and microhabitat selection by a diurnal desert lizard. Our model predicted that lizards in rock-free areas would reduce summer activity levels (e.g. foraging, basking) and that future warming will gradually decrease summer activity in rocky areas, as even large rocks become thermally stressful. Warmer winters will enable more activity but will require bushes and small rocks as shade retreats. Hence, microhabitats that may seem unimportant today will become important under climate change. Modelling frameworks should consider the microhabitat requirements of organisms to improve conservation outcomes.
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A core challenge in global change biology is to predict how species will respond to future environmental change and to manage these responses. To make such predictions and management actions robust to novel futures, we need to accurately characterize how organisms experience their environments and the biological mechanisms by which they respond. All organisms are thermodynamically connected to their environments through the exchange of heat and water at fine spatial and temporal scales and this exchange can be captured with biophysical models. Although mechanistic models based on biophysical ecology have a long history of development and application, their use in global change biology remains limited despite their enormous promise and increasingly accessible software. We contend that greater understanding and training in the theory and methods of biophysical ecology is vital to expand their application. Our review shows how biophysical models can be implemented to understand and predict climate change impacts on species' behavior, phenology, survival, distribution, and abundance. It also illustrates the types of outputs that can be generated, and the data inputs required for different implementations. Examples range from simple calculations of body temperature at a particular site and time, to more complex analyses of species' distribution limits based on projected energy and water balances, accounting for behavior and phenology. We outline challenges that currently limit the widespread application of biophysical models relating to data availability, training, and the lack of common software ecosystems. We also discuss progress and future developments that could allow these models to be applied to many species across large spatial extents and timeframes. Finally, we highlight how biophysical models are uniquely suited to solve global change biology problems that involve predicting and interpreting responses to environmental variability and extremes, multiple or shifting constraints, and novel abiotic or biotic environments.
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Mudança Climática , Ecossistema , Ecologia , Previsões , Temperatura AltaRESUMO
Mechanistic niche models are computational tools developed using biophysical principles to address grand challenges in ecology and evolution, such as the mechanisms that shape the fundamental niche and the adaptive significance of traits. Here, we review the empirical basis of mechanistic niche models in biophysical ecology, which are used to answer a broad array of questions in ecology, evolution and global change biology. We describe the experiments and observations that are frequently used to parameterize these models and how these empirical data are then incorporated into mechanistic niche models to predict performance, growth, survival and reproduction. We focus on the physiological, behavioral and morphological traits that are frequently measured and then integrated into these models. We also review the empirical approaches used to incorporate evolutionary processes, phenotypic plasticity and biotic interactions. We discuss the importance of validation experiments and observations in verifying underlying assumptions and complex processes. Despite the reliance of mechanistic niche models on biophysical theory, empirical data have and will continue to play an essential role in their development and implementation.
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Ecologia , Modelos Biológicos , Fenótipo , Ecossistema , Evolução BiológicaRESUMO
In cold environments ectotherms can be dormant underground for long periods. In 1941 Cowles proposed an ecological trade-off involving the depth at which ectotherms overwintered: on warm days, only shallow reptiles could detect warming soils and become active; but on cold days, they risked freezing. Cowles discovered that most reptiles at a desert site overwintered at shallow depths. To extend his study, we compiled hourly soil temperatures (5 depths, 90 sites, continental USA) and physiological data, and simulated consequences of overwintering at fixed depths. In warm localities shallow ectotherms have lowest energy costs and largest reserves in spring, but in cold localities, they risk freezing. Ectotherms shifting hourly to the coldest depth potentially reduce energy expenses, but paradoxically sometimes have higher expenses than those at fixed depths. Biophysical simulations for a desert site predict that shallow ectotherms have increased opportunities for mid-winter activity but need to move deep to digest captured food. Our simulations generate testable predictions to eco-physiological questions but rely on physiological responses to acute cold rather than to natural cooling profiles. Furthermore, natural-history data to test most predictions do not exist. Thus, our simulation approach uncovers knowledge gaps and suggests research agendas for studying ectotherms overwintering underground.
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Temperatura Baixa , Solo , Congelamento , Estações do Ano , TemperaturaRESUMO
Animals are responsive to predation risk, often seeking safer habitats at the cost of foraging rewards. Although previous research has examined how habitat features affect detection by predators, little is known about how the interaction of habitat features, sensory cues and physical performance capabilities affect prey escape performance once detected. To investigate how specific habitat features affect predation risk, we developed an individual-based model of terrestrial predator-prey pursuits in habitats with programmable features. We ran simulations varying the relative performance capabilities of predator and prey as well as the availability and abundance of refuges and obstacles in the habitat. Prey were more likely to avoid detection in complex habitats containing a higher abundance of obstacles; however, if detected, prey escape probability was dependent on both the abundance of refuges and obstacles and the predator's relative performance capabilities. Our model accurately predicted the relative escape success for impala escaping from cheetah in open savanna versus acacia thicket habitat, though escape success was consistently underestimated. Our model provides a mechanistic explanation for the differential effects of habitat on survival for different predator-prey pairs. Its flexible nature means that our model can be refined to simulate specific systems and could have applications towards management programmes for species threatened by habitat loss and predation.
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Ecossistema , Comportamento Predatório , AnimaisRESUMO
The capacity to tolerate climate change often varies across ontogeny in organisms with complex life cycles. Recently developed species distribution models incorporate traits across life stages; however, these life-cycle models primarily evaluate effects of lethal change. Here, we examine impacts of recurrent sublethal warming on development and survival in ecological projections of climate change. We reared lizard embryos in the laboratory under temperature cycles that simulated contemporary conditions and warming scenarios. We also artificially warmed natural nests to mimic laboratory treatments. In both cases, recurrent sublethal warming decreased embryonic survival and hatchling sizes. Incorporating survivorship results into a mechanistic species distribution model reduced annual survival by up to 24% compared to models that did not incorporate sublethal warming. Contrary to models without sublethal effects, our model suggests that modest increases in developmental temperatures influence species ranges due to effects on survivorship.
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Mudança Climática , Lagartos , Animais , Ecologia , Estágios do Ciclo de Vida , TemperaturaRESUMO
Changes in the time available for organisms to maintain physiologically preferred temperatures (thermal opportunity) is a primary mechanism by which climate change impacts the fitness and population dynamics of organisms. Yet, it is unclear whether losses or gains in thermal opportunity result in proportional changes in rates of energy procurement and use. We experimentally quantified lizard food consumption and energy assimilation at different durations of thermal opportunity. We incorporated these data in an individual-based model of foraging and digestion in lizards to explore the implications of nonlinear responses to shifts in thermal opportunity across a wide geographic range. Our model predicts that shifts in thermal opportunities resulting from climate change alter energy intake primarily through digestion rather than feeding, because simulated lizards were able to fill their gut faster than they can digest their food. Moreover, since rates of energy assimilation decelerate with increasing thermal opportunity, shifts in daily energetic assimilation would depend on the previous opportunity for thermoregulation. In particular, the same changes in thermal opportunity will have little impact on lizards from warm locations, while having a large impact on lizards from cold locations where thermoregulation is possible for only a few hours each day. Energy expenditure followed spatial patterns in thermal opportunity, with greater annual energy expenditure occurring at warmer locations. Our model predicts that lizards will spend more energy under climate change by maintaining higher body temperatures and remaining active longer. However, the predicted changes in energy assimilation following climate change greatly exceeded the predicted increases in energy expenditure. Simple models, which assume constant rates of energy gain during activity, will potentially mislead efforts to understand and predict the biological impacts of climate change.
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Mudança Climática , Lagartos/fisiologia , Animais , Regulação da Temperatura Corporal , Temperatura Baixa , TemperaturaRESUMO
Although observations suggest the potential for phenotypic plasticity to allow adaptive responses to climate change, few experiments have assessed that potential. Modeling suggests that Sceloporus tristichus lizards will need increased nest depth, shade cover, or embryonic thermal tolerance to avoid reproductive failure resulting from climate change. To test for such plasticity, we experimentally examined how maternal temperatures affect nesting behavior and embryonic thermal sensitivity. The temperature regime that females experienced while gravid did not affect nesting behavior, but warmer temperatures at the time of nesting reduced nest depth. Additionally, embryos from heat-stressed mothers displayed increased sensitivity to high-temperature exposure. Simulations suggest that critically low temperatures, rather than high temperatures, historically limit development of our study population. Thus, the plasticity needed to buffer this population has not been under selection. Plasticity will likely fail to compensate for ongoing climate change when such change results in novel stressors.
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Mudança Climática , Lagartos/fisiologia , Comportamento de Nidação , Adaptação Fisiológica , Animais , Clima , Feminino , TemperaturaRESUMO
As global warming has lengthened the active seasons of many species, we need a framework for predicting how advances in phenology shape the life history and the resulting fitness of organisms. Using an individual-based model, we show how warming differently affects annual cycles of development, growth, reproduction and activity in a group of North American lizards. Populations in cold regions can grow and reproduce more when warming lengthens their active season. However, future warming of currently warm regions advances the reproductive season but reduces the survival of embryos and juveniles. Hence, stressful temperatures during summer can offset predicted gains from extended growth seasons and select for lizards that reproduce after the warm summer months. Understanding these cascading effects of climate change may be crucial to predict shifts in the life history and demography of species.
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Aquecimento Global , Lagartos/fisiologia , Modelos Biológicos , Reprodução/fisiologia , Temperatura , Animais , Desenvolvimento Embrionário , Estágios do Ciclo de Vida , América do Norte , Dinâmica Populacional , Crescimento Demográfico , Estações do AnoRESUMO
Although animals fine-tune their activity to avoid excess heat, we still lack a mechanistic understanding of such behaviors. As the global climate changes, such understanding is particularly important for projecting shifts in the activity patterns of populations and communities. We studied how foraging decisions vary with biotic and abiotic pressures. By tracking the foraging behavior of diurnal desert spiny mice in their natural habitat and estimating the energy and water costs and benefits of foraging, we asked how risk management and thermoregulatory requirements affect foraging decisions. We found that water requirements had the strongest effect on the observed foraging decisions. In their arid environment, mice often lose water while foraging for seeds and cease foraging even at high energetic returns when water loss is high. Mice also foraged more often when energy expenditure was high and for longer times under high seed densities and low predation risks. Gaining insight into both energy and water balance will be crucial to understanding the forces exerted by changing climatic conditions on animal energetics, behavior, and ecology.
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Comportamento Apetitivo/fisiologia , Murinae/fisiologia , Perda Insensível de Água/fisiologia , Animais , Temperatura Corporal/fisiologia , Clima Desértico , Ecossistema , Israel , Comportamento Predatório , SementesRESUMO
Recent models predict contrasting impacts of climate change on tropical and temperate species, but these models ignore how environmental stress and organismal tolerance change during the life cycle. For example, geographical ranges and extinction risks have been inferred from thermal constraints on activity during the adult stage. Yet, most animals pass through a sessile embryonic stage before reaching adulthood, making them more susceptible to warming climates than current models would suggest. By projecting microclimates at high spatio-temporal resolution and measuring thermal tolerances of embryos, we developed a life cycle model of population dynamics for North American lizards. Our analyses show that previous models dramatically underestimate the demographic impacts of climate change. A predicted loss of fitness in 2% of the USA by 2100 became 35% when considering embryonic performance in response to hourly fluctuations in soil temperature. Most lethal events would have been overlooked if we had ignored thermal stress during embryonic development or had averaged temperatures over time. Therefore, accurate forecasts require detailed knowledge of environmental conditions and thermal tolerances throughout the life cycle.
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Mudança Climática , Temperatura Baixa , Temperatura Alta , Lagartos/fisiologia , Distribuição Animal , Animais , Desenvolvimento Embrionário , Extinção Biológica , Lagartos/genética , Lagartos/crescimento & desenvolvimento , Longevidade , Modelos BiológicosRESUMO
In the era of big data, ecological research is experiencing a transformative shift, yet advancements in thermal ecology and the study of animal responses to climate conditions remain limited. This review discusses how big data analytics and artificial intelligence (AI) can significantly enhance our understanding of microclimates and animal behaviors under changing climatic conditions. We explore AI's potential to refine microclimate models and analyze data from advanced sensors and camera technologies, which capture detailed, high-resolution information. This integration allows researchers to dissect complex ecological and physiological processes with unprecedented precision. We describe how AI can enhance microclimate modeling through improved bias correction and downscaling techniques, providing more accurate estimates of the conditions that animals face under various climate scenarios. Additionally, we explore AI's capabilities in tracking animal responses to these conditions, particularly through innovative classification models that utilize sensors such as accelerometers and acoustic loggers. Moreover, the widespread usage of camera traps can benefit from AI-driven image classification models to accurately identify thermoregulatory responses, such as shade usage and panting. AI is therefore instrumental in monitoring how animals interact with their environments, offering vital insights into their adaptive behaviors. Finally, we discuss how these advanced data-driven approaches can inform and enhance conservation strategies. Detailed mapping of microhabitats essential for species survival under adverse conditions can guide the design of climate-resilient conservation and restoration programs that prioritize habitat features crucial for biodiversity resilience. In conclusion, the convergence of AI, big data, and ecological science heralds a new era of precision conservation, essential for addressing the global environmental challenges of the 21st century.
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We studied the relationship between sequence of foraging, energy acquired and use of torpor as an energy-balancing strategy in diurnally active desert golden spiny mice. We hypothesised that individuals that arrive earlier to forage will get higher returns and consequently spend less time torpid. If that is the case, then early foragers can be viewed as more successful; if the same individuals arrive repeatedly early, they are likely to have higher fitness under conditions of resource limitation. For the first time, we show a relationship between foraging sequence and amount of resources removed, with individuals that arrive later to a foraging patch tending to receive lower energetic returns and to spend more time torpid. Torpor bears not only benefits but also significant costs, so these individuals pay a price both in lower energy intake and in extended periods of torpor, in what may well be a positive feedback loop.
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Adaptação Fisiológica , Metabolismo Energético , Comportamento Alimentar , Murinae/fisiologia , Animais , Ritmo Circadiano , Dinâmica Populacional , TemperaturaRESUMO
Most mammals can be characterized as nocturnal or diurnal. However infrequently, species may overcome evolutionary constraints and alter their activity patterns. We modeled the fundamental temporal niche of a diurnal desert rodent, the golden spiny mouse, Acomys russatus. This species can shift into nocturnal activity in the absence of its congener, the common spiny mouse, Acomys cahirinus, suggesting that it was competitively driven into diurnality and that this shift in a small desert rodent may involve physiological costs. Therefore, we compared metabolic costs of diurnal versus nocturnal activity using a biophysical model to evaluate the preferred temporal niche of this species. The model predicted that energy expenditure during foraging is almost always lower during the day except during midday in summer at the less sheltered microhabitat. We also found that a shift in summer to foraging in less sheltered microhabitats in response to predation pressure and food availability involves a significant physiological cost moderated by midday reduction in activity. Thus, adaptation to diurnality may reflect the "ghost of competition past"; climate-driven diurnality is an alternative but less likely hypothesis. While climate is considered to play a major role in the physiology and evolution of mammals, this is the first study to model its potential to affect the evolution of activity patterns of mammals.
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Evolução Biológica , Ritmo Circadiano , Comportamento Alimentar , Modelos Biológicos , Murinae/fisiologia , Adaptação Fisiológica , Animais , Temperatura Corporal , Ecossistema , Metabolismo Energético , Temperatura , Água/metabolismoRESUMO
Microhabitats provide ecological and physiological benefits to animals, sheltering them from predation and extreme temperatures and offering an additional supply of water and food. However, most studies have assumed no energetic costs of searching for microhabitats or moving between them, or considered how the availability of microhabitats may affect the energy reserves of animals and how such effects may differ between seasons. To fill these gaps, we studied how the body condition of lizards is affected by microhabitat availability in the extreme environment of the Judean Desert. In particular, we quantified how vegetation and rock cover in the vicinity of these lizards affect their body condition during summer and winter. First, we used aerial imagery to map the vegetation/rock cover at two study sites. Next, we collected 68 adult lizards and examined how their body condition varies across seasons and availability of vegetation and rock cover. In addition, we examined how vegetation and rock cover may differ in their effective distance (i.e., the distance that best explains body condition of lizards). We found that lizards body condition was better if they were collected closer to a higher availability of vegetation or rocks. However, while close proximity (within 10 m) was the best predictor for the positive effect of rocks, a greater distance (up to 90 m) was the best predictor for the effect of the vegetation cover. Moreover, the positive effect of vegetation was 12-fold higher than the effect of rocks. Interestingly, although the lizards' body condition during winter was poorer than during summer, the positive effects of rock and vegetation cover remained constant between the seasons. This similarity of benefits across seasons suggests that shaded microhabitats have important additional ecological roles regardless of climate, and that they may provide thermoregulatory benefits in winter too. We also found a synergic effect of vegetation and rock cover on the lizards' body condition, suggesting that their roles are complementary rather than overlapping. Our research has revealed the importance of shade- and shelter-providing microhabitats in both summer and winter. We suggest that proximity to microhabitat diversity may contribute to better body condition in lizards or, alternatively, facilitates competition and attracts lizards with better body condition. Comprehending the complex interactions between animals and different microhabitats is critical for developing better conservation plans, understanding the risks of climate change, and suggesting mitigation strategies.
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Lagartos , Animais , Lagartos/fisiologia , Estações do Ano , Ecossistema , Mudança Climática , Regulação da Temperatura CorporalRESUMO
OBJECTIVE: Placental abruption (PA) is associated with adverse maternal and neonatal outcomes. Increasing evidence has shown an association between abruption and inflammation as well as utilization of hematological biomarkers to predict the later. We aimed to evaluate the feasibility of using neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ration (PLR) taken early in pregnancy in predicting later occurrence of PA. STUDY DESIGN: A nested case control study, which compared parturient with PA (cases) to parturient without PA (controls). Parturient were matched by hospitalization date and maternal age. Demographic, clinical, and obstetrical characteristics were retrieved. Hematological indices derived from complete blood count taken during the first trimester of pregnancy, specifically NLR and PLR were retrieved and compared between the groups. Mann-Whitney and T-test were performed for not normally and normally distributed continuous variables respectively, categorical variables were analyzed using Chi-Square or Fisher Exact test as appropriate. RESULTS: The study comprised of 232 patients. Of these, 131 had suffered from PA and 131 without PA. Parturient who had PA has significantly higher rates of hypertensive disorders of pregnancy, mean neutrophil, lymphocyte and platelet count did not differ between the groups. A comparison of NLR and PLR between the study groups yielded no significant differences. CONCLUSION: NLR and PLR taken early in the course of pregnancy were not found associated with PA. Given the potentially severe consequences of PA, the biological plausibility and the readiness of these hematological markers, further investigation of this method with larger, prospective studies are needed.
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Descolamento Prematuro da Placenta/diagnóstico , Biomarcadores/análise , Descolamento Prematuro da Placenta/sangue , Descolamento Prematuro da Placenta/epidemiologia , Adulto , Biomarcadores/sangue , Estudos de Casos e Controles , Distribuição de Qui-Quadrado , Feminino , Humanos , Israel/epidemiologia , Gravidez , Estatísticas não ParamétricasRESUMO
OBJECTIVE: To evaluate whether neutrophil-to-lymphocyte ratio (NLR), a well-established inflammatory marker, can be used as an early predictor for small-for-gestational-age (SGA) neonates and other adverse pregnancy outcomes. METHODS: A case-control study compared first-trimester hematological biomarkers in pregnancies of patients with and without SGA (n=149, n=151, respectively). Demographic, clinical, and obstetrical characteristics and first-trimester complete blood count were retrieved. Woman with singleton pregnancies who delivered at Soroka University Medical Center between January 2015 and December 2016 were included. Patients with known maternal infections, relevant medications, hematological conditions, and chronic diseases that may alter the blood count, those with multiple pregnancies, and those with congenital or chromosomal abnormalities were excluded. After univariate analysis, a linear regression model was constructed to assess the association between hematological indices and SGA. Receiver operating curves were constructed to evaluate the sensitivity and specificity of NLR. RESULTS: First-trimester NLR values of the SGA group were significantly higher compared to controls (3.03 ± 1.68 vs 2.63 ± 1.2, P=0.016). Significantly higher levels of NLR were noted among the severely (<3%) SGA neonates (3.12 ± 1.62 vs 2.62 ± 1.2; P=0.034). CONCLUSION: NLR may be an early, clinically useful marker in the prediction of SGA. As blood samples are routinely collected, correct implication of this result may serve as a valuable non-invasive, low-cost, readily available predicting tool.