ReptiLearn: An automated home cage system for behavioral experiments in reptiles without human intervention

Understanding behavior and its evolutionary underpinnings is crucial for unraveling the complexities of brain function. Traditional approaches strive to reduce behavioral complexity by designing short-term, highly constrained behavioral tasks with dichotomous choices in which animals respond to defined external perturbation. In contrast, natural behaviors evolve over multiple time scales during which actions are selected through bidirectional interactions with the environment and without human intervention. Recent technological advancements have opened up new possibilities for experimental designs that more closely mirror natural behaviors by replacing stringent experimental control with accurate multidimensional behavioral analysis. However, these approaches have been tailored to fit only a small number of species. This specificity limits the experimental opportunities offered by species diversity. Further, it hampers comparative analyses that are essential for extracting overarching behavioral principles and for examining behavior from an evolutionary perspective. To address this limitation, we developed ReptiLearn-a versatile, low-cost, Python-based solution, optimized for conducting automated long-term experiments in the home cage of reptiles, without human intervention. In addition, this system offers unique features such as precise temperature measurement and control, live prey reward dispensers, engagement with touch screens, and remote control through a user-friendly web interface. Finally, ReptiLearn incorporates low-latency closed-loop feedback allowing bidirectional interactions between animals and their environments. Thus, ReptiLearn provides a comprehensive solution for researchers studying behavior in ectotherms and beyond, bridging the gap between constrained laboratory settings and natural behavior in nonconventional model systems. We demonstrate the capabilities of ReptiLearn by automatically training the lizard Pogona vitticeps on a complex spatial learning task requiring association learning, displaced reward learning, and reversal learning.

Implications of heat exchange for a free-living endangered marsupial determined by non-invasive thermal imaging

We used thermal imagining and heat balance modelling to examine the thermal ecology of wild mammals, using the diurnal marsupial numbat (Myrmecobius fasciatus) as a model. Body surface temperature was measured using infra-red thermography at environmental wet and dry bulb temperatures of 11.7-29°C and 16.4-49.3°C, respectively; surface temperature varied for different body parts and with environmental temperature. Radiative and convective heat exchange varied markedly with environmental conditions and for various body surfaces reflecting their shapes, surface areas and projected areas. Both the anterior and posterior dorsolateral body areas functioned as thermal windows. Numbats in the shade had lower rates of solar radiative heat gain but non-solar avenues for radiative heat gain were substantial. Radiative gain was higher for black and lower for white stripes, but overall, the stripes had no thermal role. Total heat gain was generally positive (<4 to >20 W) and often greatly exceeded metabolic heat production (3-6 W). Our heat balance model indicates that high environmental heat loads limit foraging in open areas to as little as 10 min and that climate change may extend periods of inactivity, with implications for future conservation and management. We conclude that non-invasive thermal imaging is informative for modelling heat balance of free-living mammals.

Inferring the lifestyles of extinct Crocodyliformes using osteoderm ornamentation

Osteoderms are bony plates formed within the dermis of diverse vertebrate groups. They are present in all crocodylomorphs but Metriorhynchidae. Most of them show typical bone ornamentation consisting of pits and ridges on their outer surface. The most widely discussed functional hypothesis suggests that the ornamentation of osteoderms influences heat exchange with the environment through the adjacent vascular network, facilitating the absorption of solar radiation. This process allows semiaquatic crocodiles to compensate for heat loss resulting from the high thermal conductivity of surrounding water. In order to test this assertion, we conducted a phylogenetic logistic regression analysis to evaluate the relationship between osteoderm relative area of pits (RAP) and lifestyle (terrestrial versus aquatic) in a sample of crocodyliforms. Our results revealed that lifestyle is significantly explained by RAP: the lower the degree of ornamentation (RAP), the higher the probability of a terrestrial lifestyle. We used this model to infer the lifestyle of two extinct taxa, Peirosaurus torminni and Microsuchus schilleri. We concluded that terrestrial notosuchians may have lost osteoderm ornamentation due to the lower thermal conductivity of air and reduced heat loss in a terrestrial environment compared to what happens in water. Among these notosuchians, we hypothesize that large terrestrial baurusuchids maintained a stable body temperature due to thermal inertia, whereas small notosuchians took advantage of the early morning sun exposure to warm up and stayed in terrestrial burrows during periods of intense solar radiation. Finally, unlike the almost motionless behavior of freshwater crocodiles, fully marine Metriorhynchidae probably lost osteoderms because they constantly swim, generating heat by muscular contraction, so osteoderms with a thermoregulatory function for heat absorption were no longer positively selected.

Strategies and Mechanisms of Thermal Compensation in Newborn Water Buffaloes

Hypothermia is one of the principal causes of perinatal mortality in water buffaloes and can range from 3% to 17.9%. In ruminants, factors affecting hypothermia in newborns may be of intrinsic (e.g., level of neurodevelopment, birth weight, vitality score, amount of brown fat, skin features) or extrinsic origin (e.g., maternal care, environmental conditions, colostrum consumption). When newborn buffaloes are exposed to cold stress, thermoregulatory mechanisms such as peripheral vasoconstriction and shivering and non-shivering thermogenesis are activated to prevent hypothermia. Due to the properties of infrared thermography (IRT), as a technique that detects vasomotor changes triggered by a reduction in body temperature, evaluating the central and peripheral regions in newborn buffaloes is possible. This review aims to analyze behavioral, physiological, and morphological strategies and colostrum consumption as thermal compensation mechanisms in newborn water buffalo to cope with environmental changes affecting thermoneutrality. In addition, the importance of monitoring by IRT to identify hypothermia states will be highlighted. Going deeper into these topics related to the water buffalo is essential because, in recent years, this species has become more popular and is being bred in more geographic areas.

Non-invasive measurements of respiration and heart rate across wildlife species using Eulerian Video Magnification of infrared thermal imagery

BACKGROUND

An animal's metabolic rate, or energetic expenditure, both impacts and is impacted by interactions with its environment. However, techniques for obtaining measurements of metabolic rate are invasive, logistically difficult, and costly. Red-green-blue (RGB) imaging tools have been used in humans and select domestic mammals to accurately measure heart and respiration rate, as proxies of metabolic rate. The purpose of this study was to investigate if infrared thermography (IRT) coupled with Eulerian video magnification (EVM) would extend the applicability of imaging tools towards measuring vital rates in exotic wildlife species with different physical attributes.

RESULTS

We collected IRT and RGB video of 52 total species (39 mammalian, 7 avian, 6 reptilian) from 36 taxonomic families at zoological institutions and used EVM to amplify subtle changes in temperature associated with blood flow for respiration and heart rate measurements. IRT-derived respiration and heart rates were compared to 'true' measurements determined simultaneously by expansion of the ribcage/nostrils and stethoscope readings, respectively. Sufficient temporal signals were extracted for measures of respiration rate in 36 species (85% success in mammals; 50% success in birds; 100% success in reptiles) and heart rate in 24 species (67% success in mammals; 33% success in birds; 0% success in reptiles) using IRT-EVM. Infrared-derived measurements were obtained with high accuracy (respiration rate, mean absolute error: 1.9 breaths per minute, average percent error: 4.4%; heart rate, mean absolute error: 2.6 beats per minute, average percent error: 1.3%). Thick integument and animal movement most significantly hindered successful validation.

CONCLUSION

The combination of IRT with EVM analysis provides a non-invasive method to assess individual animal health in zoos, with great potential to monitor wildlife metabolic indices in situ.

Allometry reveals trade-offs between Bergmann's and Allen's rules, and different avian adaptive strategies for thermoregulation

Animals tend to decrease in body size (Bergmann's rule) and elongate appendages (Allen's rule) in warm climates. However, it is unknown whether these patterns depend on each other or constitute independent responses to the thermal environment. Here, based on a global phylogenetic comparative analysis across 99.7% of the world's bird species, we show that the way in which the relative length of unfeathered appendages co-varies with temperature depends on body size and vice versa. First, the larger the body, the greater the increase in beak length with temperature. Second, the temperature-based increase in tarsus length is apparent only in larger birds, whereas in smaller birds, tarsus length decreases with temperature. Third, body size and the length of beak and tarsus interact with each other to predict the species' environmental temperature. These findings suggest that the animals' body size and shape are products of an evolutionary compromise that reflects distinct alternative thermoregulatory adaptations.

Postural, pilo-erective and evaporative thermal windows of the short-beaked echidna (Tachyglossus aculeatus)

We identify for wild, free-living short-beaked echidnas (Tachyglossus aculeatus) a novel evaporative window, along with thermal windows, and demonstrate the insulating properties of the spines, using infrared thermography. The moist tip of their beak, with an underlying blood sinus, functions as a wet bulb globe thermometer, maximizing evaporative heat loss via an evaporative window. The ventral surface and insides of the legs are poorly insulated sites that act as postural thermal windows, while the spines provide flexible insulation (depending on piloerection). These avenues of heat exchange likely contribute to the higher-than-expected thermal tolerance of this species. Our study highlights how technological advances that allow for non-contact measurement of thermal variables allow us to better understand the physiological capacity of animals in their natural environment.

Differences of energy adaptation strategies in Tupaia belangeri between Pianma and Tengchong region by metabolomics of liver: Role of warmer temperature

Global warming is becoming the future climate trend and will have a significant impact on small mammals, and they will also adapt at the physiological levels in response to climate change, among which the adaptation of energetics is the key to their survival. In order to investigate the physiological adaptation strategies in Tupaia belangeri affected by the climate change and to predict their possible fate under future global warming, we designed a metabonomic study in T. belangeri between two different places, including Pianma (PM, annual average temperature 15.01°C) and Tengchong (TC, annual average temperature 20.32°C), to analyze the differences of liver metabolite. Moreover, the changes of resting metabolic rate, body temperature, uncoupling protein 1content (UCP1) and other energy indicators in T. belangeri between the two places were also measured. The results showed that T. belangeri in warm areas (TC) reduced the concentrations of energy metabolites in the liver, such as pyruvic acid, fructose 6-phosphate, citric acid, malic acid, fumaric acid etc., so their energy metabolism intensity was also reduced, indicating that important energy metabolism pathway of glycolysis and tricarboxylic acid cycle (TCA) pathway reduced in T. belangeri from warmer habitat. Furthermore, brown adipose tissue (BAT) mass, UCP1 content and RMR in TC also decreased significantly, but their body temperature increased. All of the results suggested that T. belangeri adapt to the impact of warm temperature by reducing energy expenditure and increasing body temperature. In conclusion, our research had broadened our understanding of the physiological adaptation strategies to cope with climate change, and also provided a preliminary insight into the fate of T. belangeri for the future global warming climate.

Effects of environmental condition, size, coat type, and body condition score on rectal temperature prediction in dogs using infrared auricular and surface temperature

Background and Aim:

Generally, rectal body temperature (BTrectum) is used to prefer as core body temperature in dogs. However, this procedure is time- and labor-consuming with stress induction. Therefore, infrared auricular temperature (BTear) and surface temperature (ST) could be applied to estimate BTrectum. This study aimed to estimate BTrectum from BTear or ST in various areas and determined the factors that influenced the accuracy of prediction equations.

Materials and Methods:

Under controlled temperature (n=197) and ambient temperature (n=183), the parameters BTrectum, BTear, and ST at internal pinna, auricular canal, lateral aspect of shoulder, hip, axillary area, inguinal area, footpad, and anal area (STrectum) were measured. In addition, temperature and humidity levels of the surrounding environment were recorded. The correlation between each measurement technique was calculated. The BTrectum prediction equation was created using all measured data and several influencing factors (environmental condition, size, coat type, and body condition score [BCS]).

Results:

The highest correlation with BTrectum was observed for BTear (r=0.61, p<0.01), which was similar to STrectum (r=0.61, p<0.01). Based on multiple linear regression model results using BTrectum as the dependent variable, BTear or STrectum were first selected as independent variables in all estimation equations. Ambient temperatures (R²=0.397), small breed (R²=0.582), long hair (R²=0.418), and/or a BCS of 2 (R²=0.557) provided the highest coefficients of determination of the prediction equation.

Conclusion:

The most appropriate predictors for estimating BTrectum were STrectum and BTear, which were impacted by the dog’s signalments and the environment. To obtain satisfactory outcomes, the equation must be selected depending on the dog’s signalments and the environmental conditions. However, based on the findings of this investigation, the accuracy remains low in several equations, and further studies are needed to improve the accuracy of the equation, mainly by increasing the sample size and developing a specific equation for each dog’s signaling and environmental condition.

Thermal and Circulatory Changes in Diverse Body Regions in Dogs and Cats Evaluated by Infrared Thermography

Infrared thermography (IRT) has been proposed as a method for clinical research to detect local inflammatory processes, wounds, neoplasms, pain, and neuropathies. However, evidence of the effectiveness of the thermal windows used in dogs and cats is discrepant. This review aims to analyze and discuss the usefulness of IRT in diverse body regions in household animals (pets) related to recent scientific evidence on the use of the facial, body, and appendicular thermal windows. IRT is a diagnostic method that evaluates thermal and circulatory changes under different clinical conditions. For the face, structures such as the lacrimal caruncle, ocular area, and pinna are sensitive to assessments of stress degrees, but only the ocular window has been validated in felines. The usefulness of body and appendicular thermal windows has not been conclusively demonstrated because evidence indicates that biological and environmental factors may strongly influence thermal responses in those body regions. The above has led to proposals to evaluate specific muscles that receive high circulation, such as the bicepsfemoris and gracilis. The neck area, perivulvar, and perianal regions may also prove to be useful thermal windows, but their degree of statistical reliability must be established. In conclusion, IRT is a non-invasive technique that can be used to diagnose inflammatory and neoplastic conditions early. However, additional research is required to establish the sensitivity and specificity of these thermal windows and validate their clinical use in dogs and cats.

Testing the febrile response of snakes inoculated with Ophidiomyces ophidiicola, the causative agent of snake fungal disease

Snake Fungal Disease (SFD) negatively impacts wild snake populations in the eastern United States and Europe. Ophidiomyces ophidiicola causes SFD and manifests clinically by the formation of heterophilic granulomas around the mouth and eyes, weight loss, impaired vision, and sometimes death. Field observations have documented early seasonal basking behaviors in severely infected snakes, potentially suggesting induction of a behavioral febrile response to combat the mycosis. This study tested the hypothesis that snakes inoculated with Ophidiomyces ophidiicola would seek elevated basking temperatures to control body temperature and behaviorally induce a febrile response. Eastern ribbon snakes (Thamnophis saurita, n = 29) were experimentally or sham inoculated with O. ophidiicola. Seven days after inoculation, snakes were tested on a thermal gradient and the internal body temperature and substrate temperature of each snake was recorded over time. Quantitative PCR was used when snakes arrived, during pre-inoculation, and post-inoculation to test snakes for the presence of O. ophidiicola. Some snakes arrived with O. ophidiicola and were subsequently inoculated, allowing for an assessment of secondary exposure effects. Snake thermoregulatory behavior was compared between 1) O. ophidiicola inoculated vs. sham inoculated treatments, 2) infected vs. disease negative groups, and 3) disease naïve vs. pre-exposed immune response categories. Neither internal nor substrate temperatures differed among initially prescribed, and qPCR recovered disease states, although infected snakes tended to reach a preferred body temperature faster than disease negative snakes. Snakes experiencing their first exposure (disease naïve) sought higher substrate temperatures than snakes experiencing their second exposure (pre-exposed). Here, we recover no evidence for behaviorally induced fever in snakes with SFD but do elucidate a febrile immune response associated with secondary exposure.

Comparison of diurnal rectal and body surface temperatures in large white piglets during the hot-dry season in a tropical Guinea savannah

The aim of the study was to determine the differences in rectal and body surface temperatures and their extent of conformity using digital and infrared thermometers, respectively, in piglets during the hot-dry season in a tropical guinea savannah of Nigeria. Thirty Large White piglets of both sexes, aged 10-14 days, served as the experimental subjects. The rectal and surface body temperatures were recorded concurrently with those of the ambient dry- and wet-bulbs, during the day at 06:00, 09:00, 12:00, 15:00 and 18:00 h (GMT +1). There were significant (P < 0.05) diurnal variations in all body and ambient temperature readings, with the highest values obtained in the afternoon (at 15:00 h GMT + 1). The mean diurnal rectal and body surface temperatures in the piglets at 09:00-18:00 h were significantly higher (P < 0.001) than the corresponding values at 06:00 h. The overall mean rectal temperature (39.00 ± 0.04 °C) was higher (P < 0.01) than body surface temperature recorded for the eye (38.05 ± 0.04 °C), ear (38.10 ± 0.07 °C), head (37.97 ± 0.05 °C), nose (35.68 ± 0.13 °C), scapula (38.16 ± 0.06 °C), thigh (38.00 ± 0.06 °C), back (38.02 ± 0.06 °C) and hoof (36.83 ± 0.07 °C). The largest and smallest mean difference between rectal and body surface temperatures was -3.32 ± 0.12 °C and -0.84 ± 0.06 °C for the temperature of the nose and scapula, respectively. The positive correlation (P < 0.05) between body temperatures (rectal and surface) of the piglets with ambient temperature implied that the later had a tremendous effect on the former. Body surface temperatures at the region of eye, ear, head, nose, scapula, thigh, back and hoof had significantly (P < 0.0001) linear and positive relationships with rectal temperature. In conclusion, the similar diurnal trends, highly significant correlation coefficients and linear relationships between the rectal and body surface temperatures suggest that the later may serve as valid and reliable estimates of the former in piglets.

Computer Vision, Machine Learning, and the Promise of Phenomics in Ecology and Evolutionary Biology

For centuries, ecologists and evolutionary biologists have used images such as drawings, paintings and photographs to record and quantify the shapes and patterns of life. With the advent of digital imaging, biologists continue to collect image data at an ever-increasing rate. This immense body of data provides insight into a wide range of biological phenomena, including phenotypic diversity, population dynamics, mechanisms of divergence and adaptation, and evolutionary change. However, the rate of image acquisition frequently outpaces our capacity to manually extract meaningful information from images. Moreover, manual image analysis is low-throughput, difficult to reproduce, and typically measures only a few traits at a time. This has proven to be an impediment to the growing field of phenomics – the study of many phenotypic dimensions together. Computer vision (CV), the automated extraction and processing of information from digital images, provides the opportunity to alleviate this longstanding analytical bottleneck. In this review, we illustrate the capabilities of CV as an efficient and comprehensive method to collect phenomic data in ecological and evolutionary research. First, we briefly review phenomics, arguing that ecologists and evolutionary biologists can effectively capture phenomic-level data by taking pictures and analyzing them using CV. Next we describe the primary types of image-based data, review CV approaches for extracting them (including techniques that entail machine learning and others that do not), and identify the most common hurdles and pitfalls. Finally, we highlight recent successful implementations and promising future applications of CV in the study of phenotypes. In anticipation that CV will become a basic component of the biologist’s toolkit, our review is intended as an entry point for ecologists and evolutionary biologists that are interested in extracting phenotypic information from digital images.

Selection on phenotypic plasticity favors thermal canalization

Climate change affects organisms worldwide with profound ecological and evolutionary consequences, often increasing population extinction risk. Climatic factors can increase the strength, variability, or direction of natural selection on phenotypic traits, potentially driving adaptive evolution. Phenotypic plasticity in relation to temperature can allow organisms to maintain fitness in response to increasing temperatures, thereby "buying time" for subsequent genetic adaptation and promoting evolutionary rescue. Although many studies have shown that organisms respond plastically to increasing temperatures, it is unclear if such thermal plasticity is adaptive. Moreover, we know little about how natural and sexual selection operate on thermal reaction norms, reflecting such plasticity. Here, we investigate how natural and sexual selection shape phenotypic plasticity in two congeneric and phenotypically similar sympatric insect species. We show that the thermal optima for longevity and mating success differ, suggesting temperature-dependent trade-offs between survival and reproduction in both sexes. Males in these species have similar thermal reaction norm slopes but have diverged in baseline body temperature (intercepts), being higher for the more northern species. Natural selection favored reduced thermal reaction norm slopes at high ambient temperatures, suggesting that the current level of thermal plasticity is maladaptive in the context of anthropogenic climate change and that selection now promotes thermal canalization and robustness. Our results show that ectothermic animals also at high latitudes can suffer from overheating and challenge the common view of phenotypic plasticity as being beneficial in harsh and novel environments.

Evidence from Tarentola mauritanica (Gekkota: Phyllodactylidae) helps validate thermography as a tool to infer internal body temperatures of lizards

Infrared (IR) thermal imaging has become an increasingly popular tool to measure body temperature of animals. The high-resolution data it provides with short lag and minimum disturbance makes it an appealing tool when studying reptile thermal ecology. However, due to the common phenomenon of regional heterothermy and surface-to-core temperature gradients, it is essential to select the appropriate body part to measure and provide calibrations to accurately infer internal body temperatures. This work follows from a previous study on lacertid lizards to assess the reliability of thermography-measured body temperatures, from several body locations, as a proxy for internal body temperature in lizards. This study focuses on the Moorish gecko, Tarentola mauritanica, due to its distant phylogenetic relationship and its different ecology and morphology from the previously tested species. A total of 60 adult geckos of both sexes and of a range of sizes were tested in thermal gradients and subjected to a sequence of randomly assorted treatments of heating and cooling. The temperatures of the animals were periodically measured with a thermal camera at six different body parts and, immediately after, the cloacal temperature was then measured with a thermocouple probe. Body parts' temperatures, obtained thermographically, were regressed against cloacal temperature using OLS regression and the pairwise correlations were tested using Spearman coefficients. Relationships among all body parts and between all body parts and the cloaca were strong in all cases (R² > 0.87, Spearman Correlation > 0.95). The observed pattern was very similar to those previously obtained from lacertid lizards. Ultimately, the eye proved to provide the best overall proxy for internal temperature, when accounting for both the slope and intercept of the regression. Hence, this study provides further support for the establishment of the eye as the standard location to infer internal body temperatures of lizards through thermography.

Detecting small and cryptic animals by combining thermography and a wildlife detection dog

Small and cryptic species are challenging to detect and study in their natural habitat. Many of these species are of conservation concern, and conservation efforts may be hampered by the lack of basic information on their ecological needs. Brown hare (Lepus europaeus) leverets - one example of such a small, cryptic and endangered animal - are notoriously difficult to detect, and therefore data on wild leverets are virtually non-existent. Novel technologies and methods such as thermal imaging and the use of wildlife detection dogs represent suitable means for the detection of such species by overcoming the problem of camouflage, using heat or scent emission respectively. Our study on brown hare leverets provides information on how to apply these new techniques successfully for the detection of small and cryptic species, thus enabling the collection of data that was previously inaccessible (e.g. behavioural observation, radio tagging). We found that the choice of method should be made according to vegetative structure. While the handheld thermal imaging camera is best used in areas with no or low vegetative cover, the thermal drone can be used up to medium vegetative cover, whereas the detection dog method is best applied where vegetation is very dense and not suitable to be searched using thermography. Being able to search all sort of different vegetation types, our combined approach enables the collection of a balanced and unbiased dataset regarding habitat type and hence selection of study specimen. We hope that the use of these new techniques will encourage research on many cryptic species that formerly have been neglected because they could not be detected using conventional methodologies.

The evolution of dermal shield vascularization in Testudinata and Pseudosuchia: phylogenetic constraints versus ecophysiological adaptations

Studies on living turtles have demonstrated that shells are involved in the resistance to hypoxia during apnea via bone acidosis buffering; a process which is complemented with cutaneous respiration, transpharyngeal and cloacal gas exchanges in the soft-shell turtles. Bone acidosis buffering during apnea has also been identified in crocodylian osteoderms, which are also known to employ heat transfer when basking. Although diverse, many of these functions rely on one common trait: the vascularization of the dermal shield. Here, we test whether the above ecophysiological functions played an adaptive role in the evolutionary transitions between land and aquatic environments in both Pseudosuchia and Testudinata. To do so, we measured the bone porosity as a proxy for vascular density in a set of dermal plates before performing phylogenetic comparative analyses. For both lineages, the dermal plate porosity obviously varies depending on the animal lifestyle, but these variations prove to be highly driven by phylogenetic relationships. We argue that the complexity of multi-functional roles of the post-cranial dermal skeleton in both Pseudosuchia and Testudinata probably is the reason for a lack of obvious physiological signal, and we discuss the role of the dermal shield vascularization in the evolution of these groups. This article is part of the theme issue 'Vertebrate palaeophysiology'.

Differential responses of non-human primates to seasonal temperature fluctuations

Non-human primates (NHPs) can adapt to conditions outside of their natural habitat and climatic ranges but this can be influenced by inherent evolutionary traits or plasticity of species that evolved in diverse environmental conditions. In this study, we investigated how five species of NHPs that have natural distributions across a range of climatic conditions responded to seasonal temperature changes in a captive environment. The activity levels of NHPs were affected by temperature changes over the season, where activity levels were generally reduced at the lower and higher temperature ranges. Species that are naturally found within narrower and warmer climatic ranges, compared to those found in colder environments with wider fluctuations in temperature, showed more marked changes in activity levels in response to temperature changes. In lower temperature conditions, three out of five species showed significantly lower activity levels; whereas in higher temperature conditions, the activity levels of all species did not significantly decrease. The frequency of thermoregulation behaviours was higher, and use of artificial thermoregulatory sources lower, for species that did not substantially adjust their activity levels in different temperature conditions. Our results suggest that NHPs largely retained the evolutionary traits related to thermoregulation, according to the different ambient conditions they evolved in and may have low behavioural plasticity in adapting to conditions outside of their natural ranges. These results provide insights for improving conservation and captive management and may have implications for understanding NHP resilience to the increasing impact of global climate change.

Eye region surface temperature dynamics during acute stress relate to baseline glucocorticoids independently of environmental conditions

Reactions to acute stressors are critical for survival. Yet, the challenges of assessing underlying physiological processes in the field limit our understanding of how variation in the acute stress response relates to fitness in free-living animals. Glucocorticoid secretion during acute stress can be measured from blood plasma concentrations, but each blood sample can only provide information for one point in time. Also, the number of samples that can be extracted from an individual in the field is usually limited to avoid compromising welfare. This restricts capacity for repeated assessment, and therefore temporal resolution of findings within- and between-acute stress responses - both of which are important for determining links between acute stress and fitness. Acute stress induces additional body surface temperature changes that can be measured non-invasively, and at high frequencies using thermal imaging, offering opportunities to overcome these limitations. But, this method's usefulness in the field depends on the extent that environmental conditions affect the body surface temperature response, which remains poorly understood. We assessed the relative importance of individual physiology (baseline glucocorticoid concentrations) and environmental conditions (air temperature and relative humidity) in determining the eye region surface temperature (Teye) response to acute stress, in wild blue tits (Cyanistes caeruleus) during trapping, handling and blood sampling. When controlling for between-individual baseline variation, Teye initially dropped rapidly below, and then recovered above baseline, before declining more slowly until the end of the test, 160 s after trap closure. One measure of the amplitude of this response - the size of the initial drop in Teye - was dependent on environmental conditions, but not baseline corticosterone. Whereas, two properties defining response dynamics - the timing of the initial drop, and the slope of the subsequent recovery - were related to baseline corticosterone concentrations, independently of environmental conditions. This suggests inferring the acute stress response using thermal imaging of Teye will be practical under fluctuating environmental conditions in the field.

Thermographic evaluation of primary closure and second intention healing in dairy calves

OBJECTIVE

To evaluate the suitability of infrared thermography in assessing healing of surgically created wounds that are managed by primary closure or second intention in neonatal dairy calves during a 3-week period.

STUDY DESIGN

Randomized clinical trial.

ANIMALS

Six Jersey bull calves.

METHODS

Two skin patches approximately 10 cm² were shaved on each hind limb of all calves. The dorsal patch was designated the wound creation site, and the ventral patch was the control. The wound creation sites were randomly assigned for either primary closure or healing by second intention. Wounds were created by using an 8-mm biopsy punch. Thermographic imaging was performed prior to wound creation and at 0 minutes; 15 minutes; 2, 4, 8, 12, and 24 hours; and 2, 3, 4, 7, 10, 14, and 21 days postwounding.

RESULTS

There were no differences in skin temperature changes observed between wounds that were managed by primary closure or second intention (P = .9934) at any time. Time after wound creation had an effect on the skin temperature (P < .0001), with skin temperature consistently warmer (P < .05) 2, 4, and 8 hours after creation of wounds compared with subsequent times.

CONCLUSION

Infrared thermography was unable to detect differences in wound healing by primary closure or second intention in this model.

CLINICAL SIGNIFICANCE

Thermographic monitoring to detect differences in wound healing was not evident in this model. This model might be useful in monitoring temporal changes during early wound repair.

High variation in camera trap-model sensitivity for surveying mammal species in northern Australia

Context The use of camera traps as a wildlife survey tool has rapidly increased, and understanding the strengths and weaknesses of the technology is imperative to assess the degree to which research objectives are met. Aims We evaluated the differences in performance among three Reconyx camera-trap models, namely, a custom-modified high-sensitivity PC850, and unmodified PC850 and HC550. Methods We undertook a controlled field trial to compare the performance of the three models on Groote Eylandt, Northern Territory, by observing the ability of each model to detect the removal of a bait by native mammals. We compared variation in detecting the known event, trigger numbers, proportion of false triggers and the difference in detection probability of small to medium-sized mammals. Key results The high-sensitivity PC850 model detected bait take 75% of the time, as opposed to 33.3% and 20% for the respective unmodified models. The high-sensitivity model also increased the detection probability of the smallest mammal species from 0.09 to 0.34. However, there was no significant difference in detection probability for medium-sized mammals. Conclusions Despite the three Reconyx camera models having similar manufacturer-listed specifications, they varied substantially in their performance. The high-sensitivity model vastly improved the detection of known events and the detection probability of small mammals in northern Australia. Implications Failure to consider variation in camera-trap performance can lead to inaccurate conclusions when multiple camera models are used. Consequently, researchers should carefully consider the parameters and capabilities of camera models in study designs. Camera models and their configurations should be reported in methods, and variation in detection probabilities among different models and configurations should be incorporated into analyses.

Developmental study of the Proboscis Extension Response to heat in Rhodnius prolixus along the life cycle

Triatominae are blood-sucking insects that localise their hosts using a range of sensory signals to find food, and among them, the heat emitted by the hosts. Heat is one of the main short-range cues in vertebrate hosts, able to trigger alone the Proboscis Extension Response (PER) that precedes the bite. Previous studies demonstrated that heat responsiveness of fifth-instar nymphs is maximum to moderate temperatures (30-35°C) compatible with those of their vertebrate host's body surface. This study investigated whether this thermal preference for biting is maintained along the life cycle of R. prolixus, from the first larval instar to male and female adults. The results showed that PER rates were at maximum around 30-35°C and decreased for a warmer temperature. The same thermal preference was maintained all along the life cycle, despite the increase in the size of the antennae linked to the growth. Interestingly, a decreased thermal responsiveness was stated in males as compared with larval instars and females. This decrease might reveal a lower motivation for host-seeking and might have an impact on males's vectorial competence.

Assessing the reliability of thermography to infer internal body temperatures of lizards

For many years lizard thermal ecology studies have relied on the use of contact thermometry to obtain internal body temperature (T_b) of the animals. However, with progressing technology, an interest grew in using new, less invasive methods, such as InfraRed (IR) pyrometry and thermography, to infer T_b of reptiles. Nonetheless few studies have tested the reliability of these new tools. The present study tested the use of IR cameras as a non-invasive tool to infer T_b of lizards, using three differently body-sized lacertid species (Podarcis virescens, Lacerta schreiberi and Timon lepidus). Given the occurrence of regional heterothermy, we pairwise compared thermography readings of six body parts (snout, eye, head, dorsal, hind limb, tail base) to cloacal temperature (measured by a thermometer-associated thermocouple probe) commonly employed to measure T_b in field and lab studies. The results showed moderate to strong correlations (R²=0.84-0.99) between all body parts and cloacal temperature. However, despite the readings on the tail base showed the strongest correlation in all three species, it was the eye where the absolute values and pattern of temperature change most consistently followed the cloacal measurements. Hence, we concluded that the eye would be the body location whose IR camera readings more closely approximate that of the animal's internal environment. Alternatively, other body parts can be used, provided that a careful calibration is carried out. We provide guidelines for future research using thermography to infer Tb of lizards.

Effects of environmental variables on surface temperature of breeding adult female northern elephant seals, Mirounga angustirostris, and pups

Pinnipeds spend extended periods of time on shore during breeding, and some temperate species retreat to the water if exposed to high ambient temperatures. However, female northern elephant seals (Mirounga angustirostris) with pups generally avoid the water, presumably to minimize risks to pups or male harassment. Little is known about how ambient temperature affects thermoregulation of well insulated females while on shore. We used a thermographic camera to measure surface temperature (T_s) of 100 adult female elephant seals and their pups during the breeding season at Point Reyes National Seashore, yielding 782 thermograms. Environmental variables were measured by an onsite weather station. Environmental variables, especially solar radiation and ambient temperature, were the main determinants of mean and maximum T_s of both females and pups. An average of 16% of the visible surface of both females and pups was used as thermal windows to facilitate heat loss and, for pups, this area increased with solar radiation. Thermal window area of females increased with mean T_s until approximately 26°C and then declined. The T_s of both age classes were warmer than ambient temperature and had a large thermal gradient with the environment (female mean 11.2±0.2°C; pup mean 14.2±0.2°C). This large gradient suggests that circulatory adjustments to bypass blubber layers were sufficient to allow seals to dissipate heat under most environmental conditions. We observed the previously undescribed behavior of females and pups in the water and determined that solar radiation affected this behavior. This may have been possible due to the calm waters at the study site, which reduced the risk of neonates drowning. These results may predict important breeding habitat features for elephant seals as solar radiation and ambient temperatures change in response to changing climate.

The evolution of the avian bill as a thermoregulatory organ

The avian bill is a textbook example of how evolution shapes morphology in response to changing environments. Bills of seed-specialist finches in particular have been the focus of intense study demonstrating how climatic fluctuations acting on food availability drive bill size and shape. The avian bill also plays an important but under-appreciated role in body temperature regulation, and therefore in energetics. Birds are endothermic and rely on numerous mechanisms for balancing internal heat production with biophysical constraints of the environment. The bill is highly vascularised and heat exchange with the environment can vary substantially, ranging from around 2% to as high as 400% of basal heat production in certain species. This heat exchange may impact how birds respond to heat stress, substitute for evaporative water loss at elevated temperatures or environments of altered water availability, or be an energetic liability at low environmental temperatures. As a result, in numerous taxa, there is evidence for a positive association between bill size and environmental temperatures, both within and among species. Therefore, bill size is both developmentally flexible and evolutionarily adaptive in response to temperature. Understanding the evolution of variation in bill size however, requires explanations of all potential mechanisms. The purpose of this review, therefore, is to promote a greater understanding of the role of temperature on shaping bill size over spatial gradients as well as developmental, seasonal, and evolutionary timescales.

Thermal equilibrium and temperature differences among body regions in European plethodontid salamanders

Information on species thermal physiology is extremely important to understand species responses to environmental heterogeneity and changes. Thermography is an emerging technology that allows high resolution and accurate measurement of body temperature, but until now it has not been used to study thermal physiology of amphibians in the wild. Hydromantes terrestrial salamanders are strongly depending on ambient temperature for their activity and gas exchanges, but information on their body temperature is extremely limited. In this study we tested if Hydromantes salamanders are thermoconform, we assessed whether there are temperature differences among body regions, and evaluated the time required to reach the thermal equilibrium. During summers of 2014 and 2015 we analysed 56 salamanders (Hydromantes ambrosii and Hydromantes italicus) using infrared thermocamera. We photographed salamanders at the moment in which we found them and 1, 2, 3, 4, 5 and 15min after having kept them in the hands. Body temperature was equal to air temperature; salamanders attained the equilibrium with air temperature in about 8min, the time required to reach equilibrium was longer in individuals with large body size. We detected small temperature differences between body parts, the head being slightly warmer than the body and the tail (mean difference: 0.05°C). These salamanders quickly reach the equilibrium with the environment, thus microhabitat measurement allows obtaining accurate information on their tolerance limits.

Infrared thermography: A non-invasive window into thermal physiology

Infrared thermography is a non-invasive technique that measures mid to long-wave infrared radiation emanating from all objects and converts this to temperature. As an imaging technique, the value of modern infrared thermography is its ability to produce a digitized image or high speed video rendering a thermal map of the scene in false colour. Since temperature is an important environmental parameter influencing animal physiology and metabolic heat production an energetically expensive process, measuring temperature and energy exchange in animals is critical to understanding physiology, especially under field conditions. As a non-contact approach, infrared thermography provides a non-invasive complement to physiological data gathering. One caveat, however, is that only surface temperatures are measured, which guides much research to those thermal events occurring at the skin and insulating regions of the body. As an imaging technique, infrared thermal imaging is also subject to certain uncertainties that require physical modelling, which is typically done via built-in software approaches. Infrared thermal imaging has enabled different insights into the comparative physiology of phenomena ranging from thermogenesis, peripheral blood flow adjustments, evaporative cooling, and to respiratory physiology. In this review, I provide background and guidelines for the use of thermal imaging, primarily aimed at field physiologists and biologists interested in thermal biology. I also discuss some of the better known approaches and discoveries revealed from using thermal imaging with the objective of encouraging more quantitative assessment.

Distance makes the difference in thermography for ecological studies

Surface temperature drives many ecological processes and infrared thermography is widely used by ecologists to measure the thermal heterogeneity of different species' habitats. However, the potential bias in temperature readings caused by distance between the surface to be measured and the camera is still poorly acknowledged. We examined the effect of distance from 0.3 to 80m on a variety of thermal metrics (mean temperature, standard deviation, patch richness and aggregation) under various weather conditions and for different structural complexity of the studied surface types (various surfaces with vegetation). We found that distance is a key modifier of the temperature measured by a thermal infrared camera. A non-linear relationship between distance and mean temperature, standard deviation and patch richness led to a rapid under-estimation of the thermal metrics within the first 20m and then only a slight decrease between 20 and 80m from the object. Solar radiation also enhanced the bias with increasing distance. Therefore, surface temperatures were under-estimated as distance increased and thermal mosaics were homogenized at long distances with a much stronger bias in the warmer than the colder parts of the distributions. The under-estimation of thermal metrics due to distance was explained by atmospheric composition and the pixel size effect. The structural complexity of the surface had little effect on the surface temperature bias. Finally, we provide general guidelines for ecologists to minimize inaccuracies caused by distance from the studied surface in thermography.

Temperature preference during forelimb regeneration in the red-spotted newt Notophthalmus viridescens

Red-spotted newts (Notophthalmus viridescens) are model organisms for regenerative research. These animals can regenerate limbs, tails, jaws, spinal cords, as well as the lens of the eye. Newts are small ectotherms that are aquatic as adults; as ectotherms, they naturally conform to the temperature of their surroundings. Environmental temperatures, however, can increase or decrease the red-spotted newt's metabolic processes, including their rate of tissue regeneration; whether an optimal temperature for this rate of regeneration exists is unknown. However, newts do exhibit behavioral preferences for certain temperatures, and these thermal preferences can change with season or with acclimation. Given this flexibility in behavioral thermoregulation, we hypothesized that the process of tissue regeneration could also affect thermal preference, given the metabolic costs or altered temperature sensitivities of tissue regrowth. It was predicted that regenerating newts would select an environmental temperature that maximized the rate of regeneration, however, this prediction was not fully supported. Thermal preference trials revealed that newts consistently selected temperatures between 24 and 25°C throughout regeneration. This temperature selection was warmer than that of uninjured conspecifics, but was lower than temperatures that would have further augmented the rate of regeneration. Interestingly, regenerating newts maintained a more stable temperature preference than sham newts, suggesting that accuracy in thermoregulation may be more important to regenerating individuals, than to noninjured individuals.