High gene flow on a continental scale in the polyandrous Kentish plover Charadrius alexandrinus

Gene flow promotes genetic homogeneity of species in time and space. Gene flow can be modulated by sex‐biased dispersal that links population genetics to mating systems. We investigated the phylogeography of the widely distributed Kentish plover Charadrius alexandrinus. This small shorebird has a large breeding range spanning from Western Europe to Japan and exhibits an unusually flexible mating system with high female breeding dispersal. We analysed genetic structure and gene flow using a 427‐bp fragment of the mitochondrial (mtDNA) control region, 21 autosomal microsatellite markers and a Z microsatellite marker in 397 unrelated individuals from 21 locations. We found no structure or isolation‐by‐distance over the continental range. However, island populations had low genetic diversity and were moderately differentiated from mainland locations. Genetic differentiation based on autosomal markers was positively correlated with distance between mainland and each island. Comparisons of uniparentally and biparentally inherited markers were consistent with female‐biased gene flow. Maternally inherited mtDNA was less structured, whereas the Z‐chromosomal marker was more structured than autosomal microsatellites. Adult males were more related than females within genetic clusters. Taken together, our results suggest a prominent role for polyandrous females in maintaining genetic homogeneity across large geographic distances.     

Breeding biology of the Kentish Plover Charadrius alexandrinus in the Sabkhat Al-Fasl Lagoons,Saudi Arabia (Aves: Charadriiformes)

The breeding biology of the Kentish Plover Charadrius alexandrinus was studied in the Sabkhat Al-Fasl Lagoons of Saudi Arabia, where ground temperatures may ex- ceed 55°C in summer. Although halophytic bushes are abundant, this species seems to prefer nesting at exposed sites. Biparental brood care was common: the females were absent in only three out of 24 families. Kentish Plovers attended their nests more than 80% over the full day and more than 90% of the time during day-time, and the number of change-overs increased during the hottest parts of the day which could be due to the possibility that a single parent cannot protect the eggs and itself from overheating.     

Changes in body core temperatures and heat balance after an abrupt release of lower body negative pressure in humans

Changes in body core temperature (T _cor) and heat balance after an abrupt release of lower body negative pressure (LBNP) were investigated in 5 volunteers under the following conditions: (1) an ambient temperature (T _a) of 20 °C or (2) 35 °C, and (3)T _a of 25 °C with a leg skin temperature of 30°C or (4) 35°C. The leg skin temperature was controlled with water perfusion devices wound around the legs. Rectal (T _re), tympanic (T _ty) and esophageal (T _es) temperatures, skin temperatures (7 sites) and oxygen consumption were measured. The intensity of LBNP was adjusted so that the amount of blood pooled in the legs was the same under all conditions. When a thermal balance was attained during LBNP, application of LBNP was suddenly halted. The skin temperatures increased significantly after the release of LBNP under all conditions, while oxygen consumption hardly changed. The release of LBNP caused significant falls inT _cor s under conditions (1) and (3), but loweredT _cor s very slightly under conditions (2) and (4). The changes inT _es were always more rapid and greater than those ofT _ty andT _re. The falls inT _ty andT _re appeared to be explained by changes in heat balance, whereas the sharp drop ofT _es could not be explained especially during the first 8 min after the release of LBNP. The results suggest that a fall inT _cor after a release of LBNP is attributed to an increase in heat loss due to reflexive skin vasodilation and is dependent on the temperature of venous blood returning from the lower body. It is presumed thatT _es may not be an appropriate indicator forT _cor when venous return changes rapidly.     

Bat thermoregulation in the heat: Limits to evaporative cooling capacity in three southern African bats

High environmental temperatures pose significant physiological challenges related to energy and water balance for small endotherms. Although there is a growing literature on the effect of high temperatures on birds, comparable data are scarcer for bats. Those data that do exist suggest that roost microsite may predict tolerance of high air temperatures. To examine this possibility further, we quantified the upper limits to heat tolerance and evaporative cooling capacity in three southern African bat species inhabiting the same hot environment but using different roost types (crevice, foliage or cave). We used flow-through respirometry and compared heat tolerance limits (highest air temperature (T_a) tolerated before the onset of severe hyperthermia), body temperature (T_b), evaporative water loss, metabolic rate, and maximum cooling capacity (i.e., evaporative heat loss/metabolic heat production). Heat tolerance limits for the two bats roosting in more exposed sites, Taphozous mauritianus (foliage-roosting) and Eptesicus hottentotus (crevice-roosting), were T_a = ~44 °C and those individuals defended maximum T_b between 41 °C and 43 °C. The heat tolerance limit for the bat roosting in a more buffered site, Rousettus aegyptiacus (cave-roosting), was T_a = ~38 °C with a corresponding T_b of ~38 °C. These interspecific differences, together with a similar trend for higher evaporative cooling efficiency in species occupying warmer roost microsites, add further support to the notion that ecological factors like roost choice may have profound influences on physiological traits related to thermoregulation.     

Sensible and latent heat loss from the body surface of Holstein cows in a tropical environment

The general principles of the mechanisms of heat transfer are well known, but knowledge of the transition between evaporative and non-evaporative heat loss by Holstein cows in field conditions must be improved, especially for low-latitude environments. With this aim 15 Holstein cows managed in open pasture were observed in a tropical region. The latent heat loss from the body surface of the animals was measured by means of a ventilated capsule, while convective heat transfer was estimated by the theory of convection from a horizontal cylinder and by the long-wave radiation exchange based on the Stefan–Boltzmann law. When the air temperature was between 10 and 36°C the sensible heat transfer varied from 160 to –30 W m^–2, while the latent heat loss by cutaneous evaporation increased from 30 to 350 W m^–2. Heat loss by cutaneous evaporation accounted for 20–30% of the total heat loss when air temperatures ranged from 10 to 20°C. At air temperatures >30°C cutaneous evaporation becomes the main avenue of heat loss, accounting for approximately 85% of the total heat loss, while the rest is lost by respiratory evaporation.Part of first authors doctoral thesis     

Physiological responses to heat strain: A study on personal monitoring for young workers

Heart rate, increased body-core temperature and sweating are the physiological responses to heat stress and they are collectively known as physiological strain. Our goal was to study levels of physiological strain in young farm workers aged 15–21 y. We also verified that heart rate is the response that exceeds threshold limits earliest as seen in previous studies. Personal monitoring for heat-strain measures directly physiological strain as it occurs and gives further information about each worker's state. When estimating levels of physiological strain, certain limits concerning heart rate were adjusted considering the young ages of the workers studied.     

Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat

Body cooling before exercise (i.e. pre-cooling) reduces physiological strain in humans during endurance exercise in temperate and warm environments, usually improving performance. This study examined the effectiveness of pre-cooling humans by ice-vest and cold (3 degrees C) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performance in the heat (35 degrees C, 60% RH). Nine habitually-active males completed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degrees C air) before 35-min cycle exercise: 20 min at approximately 65% VO2peak then a 15-min work-performance trial. At exercise onset, mean core (Tc, from oesophagus and rectum) and skin temperatures, forearm blood flow (FBF), heart rate (HR), and ratings of exertion, body temperature and thermal discomfort were lower in LW and LC than CON (P<0.05). They remained lower at 20 min [e.g. Tc: CON 38.4+/-0.2 (+/-S.E.), LW 37.9+/-0.1, and LC 37.8+/-0.1 degrees C; HR: 177+/-3, 163+/-3 and 167+/-3 b.p.m.), except that FBF was equivalent (P=0.10) between CON (15.5+/-1.6) and LW (13.6+/-1.0 ml.100 ml tissue(-1) x min(-1)). Subsequent power output was higher in LW (2.95+/-0.24) and LC (2.91+/-0.25) than in CON (2.52+/-0.28 W kg(-1), P=0.00, N=8), yet final Tc remained lower. Pre-cooling by ice-vest and cold air effectively reduced physiological and psychophysical strain and improved endurance performance in the heat, irrespective of whether thighs were warmed or cooled.     

Spatial variation of heat flux in Steller sea lions: evidence for consistent avenues of heat exchange along the body trunk

Maintaining insulative fat stores is vital for homeothermic marine mammals foraging in cold polar waters. To accomplish this, animals must balance acquisition and expenditure of energy. If this balance is shifted, body condition can decrease, challenging thermal homeostasis and further affecting energy balance. Prior studies of temperature regulation in sea lions have neither quantified basic all-inclusive heat flux values for animals swimming in cold water, nor determined whether they exhibit consistent spatial patterns of heat flux. Heat flux and skin temperature data were thus collected from four captive Steller sea lions using heat flux sensors (HFSs) with embedded thermistors. Optimal sensor placement was established using infrared thermography to locate the major areas of heat flux along the surface of the animals. Experiments were conducted on swimming animals in a large habitat tank with and without a drag harness, and on stationary animals in a temperature- and current-controlled swim flume. All heat flux measurements were corrected by a previously determined correction factor of 3.42 to account for insulative effects of the HFSs and attachment mechanism. Heat flux from shoulders and hips was consistently greater than from mid-trunk and axillary areas in both swimming and stationary animals, suggesting that certain areas of the body are preferentially used to offload excess heat. Mean heat flux for animals swimming with a drag harness was significantly greater than for unencumbered animals, indicating a likely increase in heat production beyond minimum heat loss. Thus, thermal stress does not appear to constitute significant costs for Steller sea lions swimming under conditions of increased drag at speeds of approximately 1 m/s in water temperatures of approximately 8.0 °C.     

Reliability and validity of skin temperature measurement by telemetry thermistors and a thermal camera during exercise in the heat

New technologies afford convenient modalities for skin temperature (T_SKIN) measurement, notably involving wireless telemetry and non-contact infrared thermometry. The purpose of this study was to investigate the validity and reliability of skin temperature measurements using a telemetry thermistor system (TT) and thermal camera (TC) during exercise in a hot environment. Each system was compared against a certified thermocouple, measuring the surface temperature of a metal block in a thermostatically controlled waterbath. Fourteen recreational athletes completed two incremental running tests, separated by one week. Skin temperatures were measured simultaneously with TT and TC compared against a hard-wired thermistor system (HW) throughout rest and exercise. Post hoc calibration based on waterbath results displayed good validity for TT (mean bias [MB]=−0.18 °C, typical error [TE]=0.18 °C) and reliability (MB=−0.05 °C, TE=0.31 °C) throughout rest and exercise. Poor validity (MB=−1.4 °C, TE=0.35 °C) and reliability (MB=−0.65 °C, TE=0.52 °C) was observed for TC, suggesting it may be best suited to controlled, static situations. These findings indicate TT systems provide a convenient, valid and reliable alternative to HW, useful for measurements in the field where traditional methods may be impractical.     

Weighing the cost: the impact of serial heatwaves on body mass in a small Australian passerine

Rising temperatures pose a grave risk to arid zone birds because they are already living close to their physiological limits and must balance water conservation against the need for evaporative cooling. We assess how extreme temperatures affect a wild population of small passerines by monitoring daily mass change in individual jacky winters Microeca fascinans (a small Australasian robin) across a series of severe heatwaves that afflicted southern Australia in the summer of 2018–2019. Daily maximum temperature and duration of heat exposure were negatively related to the birds’ ability to maintain body mass. At maximum temperatures ≥ 42°C, birds lost 2.0% of their body mass daily and at ≥ 45°C, 2.6%. Apparent mortality increased almost three‐fold, and all breeding birds abandoned their nests. Nevertheless, net daily mass loss was less than might be expected from laboratory‐based findings, presumably because wild jacky winters undertook behavioural thermoregulation. The birds also regained some mass between heatwave events and suffered no long‐term reduction in body condition.     

Social versus individual behaviour: a comparative approach to thermal behaviour of the honeybee (Apis mellifera L.) and the American cockroach (Periplaneta americana L.)

To study the relationship between the individual and social thermoregulatory behaviour, we used honeybee workers and American cockroaches. Single insects or groups of 10-20 individuals were placed in a temperature gradient chamber, and their thermal preference was recorded for 48 h under natural summer photoperiod. Single bees showed diurnal changes in selected ambient temperature, which culminated at 14:00 reaching 34+/-2 degrees C, and then slowly decreased, reaching a nocturnal minimum of 28+/-2 degrees C at 04:00. In contrast, the zenith of temperature selected by groups of bees (31+/-1 degrees C) was reached at 04:00 and the nadir (29+/-2 degrees C) was recorded at 14:00. Groups of bees clustered together during the night time, and dispersed during intense day time activity. Such changes were absent in groups of cockroaches. Cockroaches selected an ambient temperature of 30+/-1 degrees C both during day and night. In conclusion, there is a striking analogy in the diurnal thermal behaviour between a colony of bees and mammals. During their nychthemeral rest phase, both of them select higher temperatures than during the activity phase and, simultaneously, they reduce their overall surface area of heat loss to conserve metabolic heat. Therefore, the colony behaves as a homeothermic superorganism. In contrast, a single bee, isolated from the colony, utilizes a heterothermic strategy to save energy for a morning warm up.     

舟山眼镜蛇对光暗周期加热光源反应所导致的体温变化

用 7条舟山眼镜蛇 (Najaatra)研究动物对光暗周期加热光源反应所导致的体温变化。设计两项实验 ,每项实验历时 9d。实验一光照期覆盖整个白天 ,实验二光照期覆盖整个晚上。眼镜蛇仅在加热光源开启期间进行体温调节 ,但光照期内任何阶段都未发现所有个体同时处于热活动状态。两项实验中热活动个体百分比的时间变化显著 ,实验二热活动个体百分比波动相对大于实验一。在加热光源开启期间 ,实验一热活动眼镜蛇的百分比总体上大于实验二。在两项实验中 ,热活动眼镜蛇体温的时间变化都不显著。实验一热活动眼镜蛇的体温高于实验二 ,而两项实验中不处于热活动状态的眼镜蛇的平均体温无显著差异。实验一热活动眼镜蛇 (31 1±0 8°C)选择的体温上限高于实验二眼镜蛇 (2 6 0± 0 9°C)。在两项实验的任何时间段内 ,眼镜蛇的体温都不低于环境温度。     

Modeling heat stress effects on dairy cattle milk production in a tropical environment using test-day records and random regression models

In tropical environments, dairy cattle production is constrained by several factors, including climate. The seasonal loss of milk due to heat stress is a recurring challenge for many dairy producers. The objective of this study was to detect heat stress thresholds, milk yield loss and individual animal variations using random regression models for dairy cattle from test-day milk records. Data were obtained from the Kenya Livestock Breeders Organization for the years 2000–2017 and merged with weather data. The weather parameters were grid-interpolated solar and meteorological data obtained from the National Aeronautics and Space Administration/Prediction Of Worldwide Energy Resources (NASA/POWER). After editing, the records comprised 49 993, 45 251 and 36 136 test-day records for first, second, and third lactations, respectively, for the four main dairy breeds: Friesian (68.0%), Ayrshire (21.1%), Jersey (7.6%) and Guernsey (3.3%). Variance components were estimated using Restricted Maximum Likelihood in ASReml software. Random regression models with third-order Legendre polynomials were fitted to the average and individual lactation curves and the reaction norms. An extended factor analytic variance structure for the random cow effects was used to estimate (co)variances between days in milk and thermal load. The daily average temperature (TA) and temperature humidity index (THI) were identified as the most suitable thermal load indicators for assessing milk yield losses. Considering a one day lag, the estimated heat stress thresholds were about 22 °C and 69 index units for TA and THI, respectively. Almost no differences were observed for estimated residual variances between the thermal load indicators, indicating there was no better model fit by TA or THI. The heat stress thresholds and milk loss patterns are important for management of dairy production systems in the tropics with climatic conditions similar to this study. Data recording should be improved as a tool to monitor the expected impacts of climate change and mitigation measures.     

A central excitatory serotonergic or serotonergic-like synapse on the pathway to heat production in the sheep

1. 1.|Intraventricular injections of serotonergic agonists and receptor blockers were given to sheep to determine whether the central nervous pathway mediating the drive to heat production involves serotonergic synapses.

2. 2.|At 15°C ambient temperature (T_a), 5-hydroxytryptamine (5-HT) at all doses tested, and norfenfluramine (NF) in low doses increased heat loss and decreased rectal temperature (T_re); lysergic acid diethylamide (LSD-25) and methysergide prevented these effects.

3. 3.|AT 0°C T_a, 5-HT, even in high doses failed to increase heat production but NF increased heat production and T_re.

4. 4.|The results suggest the effects of NF and LSD-25 on heat production may be related to synapses activated by an indoleamine other than 5-HT.

Repeated thermal conditioning during the neonatal period affects behavioral and physiological responses to acute heat stress in chicks

ObjectiveThe aim of the present study was to investigate the effects of repeated thermal conditioning (RTC) at an early age on physiological and behavioral responses in chicks.MethodsBirds were assigned to one of the four treatments in which the RTC was exposure to 40 °C for 15 min daily. The treatments were 1) no thermal conditioning (control); 2) early exposure group (EE; RTC from 2 to 4 days of age); 3) later exposure group (LE; RTC from 5 to 7 days of age); or 4) both early and later exposure (BE; RTC from 2 to 7 days of age). All groups of chicks were challenged with high ambient temperature (40 °C for 15 min) at two weeks of age.ResultsDuring heat challenge, initiation times of dissipation behaviors (panting and wing-drooping) were measured. Rectal temperature and respiration rate were measured after and before heat challenge. Hypothalamic samples and blood were collected at the end of heat challenges. Initiation times of dissipation behaviors and rectal temperature were not affected by the treatments. Increases in respiration rate in response to heat challenge were suppressed by early RTC treatment. There was no clear pattern of glucose levels in relation to thermal conditioning, whereas plasma corticosterone levels were decreased by early treatment (EE and BE groups). Hypothalamic thyrotropin releasing hormone gene expression was suppressed by early and later thermal conditioning and suppressed further by both early and later exposure. Neuropeptide Y gene expression in the BE group was lower than in the other groups, with a similar trend for corticotropin releasing hormone expression.ConclusionOur results suggest that the effect of repeated thermal conditioning on the central thermoregulatory system depends on the number of times that chicks experienced conditioning. In addition, repeated thermal conditioning has greater effects on the acquisition of thermotolerance when conditioning occurs in chicks of two to four days of age in comparison with chicks of five to seven days of age.     

北草蜥种群间生活史变异的成因分析:热环境、食物可利用性和体温的岛屿间差异

比较浙江温州北麂岛与洞头岛的热环境、食物可利用性以及动物体温,以辨析北草蜥岛屿种群间生活史特征差异中环境因子的作用。通过测定岛屿上北草蜥栖息地植被和环境温度,比较岛屿热环境的差异。野外测定活动蜥蜴的体温、环境温度和活动规律,实验室温梯板中测定动物喜好体温。用陷阱法测定无脊椎动物多样性和丰度,以比较岛屿蜥蜴种群的食物可利用性。岛屿植被存在差异导致热环境的差异。洞头岛植被高于北麂岛,地表层光线透入率则低于北麂岛。因而,洞头岛郁闭地表的平均温度和最高温度显著低于北麂岛,但两岛裸露地面的温度无显著差异。热环境的岛屿间差异进而影响北草蜥的野外体温。在春季,洞头岛的野外有效温度和基底温度显著大于北麂岛,而两岛北草蜥的体温无显著差异;在夏季,洞头岛的北草蜥体温、有效温度和基质温度均显著高于北麂岛;到秋季,北麂岛蜥蜴体温和环境温度高于洞头岛。地面无脊椎动物多样性和丰度的岛屿间差异表明北麂岛食物可利用性大于洞头岛。岛屿间北草蜥日活动规律和喜好体温无显著差异。本研究表明:(1)温度和食物可利用性存在岛屿间差异,岛屿种群间生活史特征差异可能与之有关;(2)两岛屿北草蜥主要采取行为调节对策来适应自然界的热环境变化,尚未发现热生理学特征的进化性漂移[动物学报51(5):797-805,2005]。     

Influences of sex,ontogeny and body size on the thermal ecology of Liolaemus lutzae (Squamata,Liolaemidae) in a restinga remnant in southeastern Brazil

Variations in body temperature (T_b) of lizards can be partially explained by intrinsic factors such as sex, ontogeny and body size. Liolaemus lutzae is a lizard species restricted to restingas in the Brazilian coast in the state of Rio de Janeiro. Herein, we studied sexual dimorphism and influences of sex, ontogeny, and body size to the T_b of L. lutzae. Adult males were larger than adult females, probably due to both intersexual selection and intra-sexual selection. There was intersexual difference in lizards' T_b (males hotter than females), but T_b did not differ after factored out for the effects of body size. The mean T_b of juvenile lizards was higher than that of adults after factored out for the effect of body mass. It is possible that adults may have excluded juveniles from microhabitats with better thermal regimes. Also, this might have occurred due to requirements of juveniles to maintain high growth rates. Forage searching for prey by juveniles also exposes them to high environmental temperatures. Juveniles also may have higher T_b than co-specific adults (relative to body mass) to favor prey capture. In absolute values, adult lizards tended to use microhabitats with lower temperatures than that used by juveniles, possibly to avoid risks of overheating and death. Body temperature and snout–vent length were positively related, as well as body temperature and body mass, presumably caused by the thermal inertia of the bodies (trend of a body to resist to changes in its temperature). Intrinsic factors such as sex, ontogeny and body size can affect the thermal ecology of L. lutzae, despite coastal habitat features to which they are exposed also influences the body temperature of active lizards in restinga habitats.     

Adaptations of the reed frog Hyperolius viridiflavus (Amphibia,Anura, Hyperoliidae) to its arid environment. VII. The heat budget of Hyperolius viridiflavus nitidulus and the evolution of an optimized body shape

Estivating reed frogs of the superspecies Hyperolius viridiflavus are extraordinarily resistant to the highly adverse climatic conditions prevailing in their African savanna habitats during dry season (air temperature up to 45°C, solar radiation load up to 1000 W·m^-2, no water replenishment possible for up to 3 months). They are able to withstand such climatic stress at their exposed estivation sites on dry plants without evaporative cooling. We developed a heat budget model to understand the mechanisms of how an anuran can achieve this unique tolerance, and which allows us to predict the anuran's core and surface temperature for a given set of environmental parameters, to within 4% of the measured values. The model makes it possible to quantify some of the adaptive mechanisms for survival in semiarid habitats by comparing H. viridiflavus with anurans (H. tuberilinguis and Rana pipiens) of less stressful habitats. To minimize heat gain and maximize heat loss from the frog, the following points were important with regard to avoiding lethal heat stress during estivation: 1) solar heat load is reduced by an extraordinarily high skin reflectivity for solar radiation of up to 0.65 under laboratory and even higher in the field under dry season conditions. 2) The half-cylindrical body shape of H. viridiflavus seems to be optimized for estivation compared to the hemispheroidal shape usually found for anurans in moist habitats. A half-cylinder can be positioned relative to the sun so that large surface areas for conductive and convective heat loss are shielded by a small area exposed to direct solar radiation. 3) Another important contribution of body shape is a high body surface area to body mass ratio, as found in the estivating subadult H. viridiflavus (snout-vent lengths of 14–20 mm and body weights of 350–750 mg) compared to adult frogs (24–30 mm, 1000–2500 mg) which have never been observed to survive a dry season. 4) These mechanisms strongly couple core temperature to air temperature. The time constant of the core temperature is 29±10 s. Since air temperature can be 43–45°C, H. viridiflavus must have a very unusual tolerance to transient core temperatures of 43–45°C. 5) If air temperature rises above this lethal limit, the estivating frog would die despite all its optimizations, but moving from an unsuited to a more favorable site during estivation can be extremely costly in terms of unavoidably high evaporative water loss. Therefore, H. viridiflavus must have developed behavioral strategies for reliably choosing estivation sites with air temperature staying on average within the vital range during the whole dry season.Abbreviations a absorption coefficient - a absorption coefficient of a T _OE model - A area - A _A light absorbing area - A _C theoretical body core area surrounding a constant core temperature - A _D dorsal skin area - A _E thermal (far infrared radiation) emitting area - A _EM A _E of a T _OE model - A _S silhouette area - A _SM A _S of a T _OE model - A _T total surface area - A _v ventral area - b body breadth just behind the forelimbs - bw body weight - bl body length - C _S specific heat capacity - C _D conductive energy flow - C _v convective energy flow - f _(z) silhouette function - h _C heat transfer coefficient - h _CM heat transfer coefficient of a T _OE model     

Modelling exposure to selected temperature during pregnancy: the limitations of squamate viviparity in a cool-climate environment

Behavioural thermoregulation is important for the success of cool‐climate lizards, and a basis of the cold‐climate hypothesis for the evolution of viviparity in squamate reptiles. The temperature (T_sel) selected by pregnant females in a thermal gradient is considered to be optimal for embryonic development; however, exposure to T_sel throughout pregnancy has been difficult to estimate in small‐bodied lizards as temperature‐sensitive telemetry is impractical. In addition, the value of maternal thermophily during pregnancy is controversial: some studies have shown elevated T_sel, whereas others have found lowered T_sel or no change during pregnancy. We estimated indirectly the overall exposure to T_sel during the 4–5 months of pregnancy of the cool‐climate, sub‐alpine species Oligosoma maccanni (McCann's skink, 3–6 g) from southern New Zealand. The thermal environment available to skinks was modelled using temperature loggers inside validated copper models in basking and retreat sites. Pregnant skinks were able to achieve mean T_sel (28.9 °C) in the field very infrequently (4–15% of each month during the final 4 months of pregnancy). In field thermoregulatory studies, pregnant females did not bask more frequently and did not show altered field body temperature compared with non‐pregnant adults, suggesting that all skinks (whether pregnant or not) thermoregulate maximally whenever conditions allow. Further research on cool‐climate lizards should address the significance for offspring phenotypes of low and variable exposure to T_sel during pregnancy, as well as the significance of temperatures for embryos in maternal bodies (viviparity) versus nest sites (oviparity) arising from differences in maternal body size. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96 , 541–552.