The key to winter survival: daily torpor in a small arid-zone marsupial

Mammalian hibernation, which lasts on average for about 6 months, can reduce energy expenditure by >90% in comparison to active individuals. In contrast, the widely held view is that daily torpor reduces energy expenditure usually by about 30%, is employed for a few hours every few days, and often occurs only under acute energetic stress. This interpretation is largely based on laboratory studies, whereas knowledge on daily torpor in the field is scant. We used temperature telemetry to quantify thermal biology and activity patterns of a small arid-zone marsupial, the stripe-faced dunnart Sminthopsis macroura (16.9 g), in the wild and to test the hypothesis that daily torpor is a crucial survival strategy of this species in winter. All individuals entered torpor daily with the exception of a single male that remained normothermic for a single day (torpor on 212 of 213 observation days, 99.5%). Torpor was employed at air temperatures (T _a) ranging from approximately −1°C to 36°C. Dunnarts usually entered torpor during the night and aroused at midday with the daily increase of T _a. Torpor was on average about twice as long (mean 11.0 ± 4.7 h, n = 8) than in captivity. Animals employed sun basking during rewarming, reduced foraging time significantly, and occasionally omitted activity for several days in sequence. Consequently, we estimate that daily torpor in this species can reduce daily energy expenditure by up to 90%. Our study shows that for wild stripe-faced dunnarts daily torpor is an essential mechanism for overcoming energetic challenges during winter and that torpor data obtained in the laboratory can substantially underestimate the ecological significance of daily torpor in the wild.     

Coping with chaos: unpredictable food supplies intensify torpor use in an arid-zone marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata)

The severity, duration and amplitude of extreme weather events are forecast to intensify with current climate trends, over both long (e.g. seasonal) and short (e.g. daily) time-scales. As such, the predictability of food supplies for many small endotherms is likely to become increasingly important. Numerous small mammals and birds combat food shortages using torpor, a controlled reduction in metabolic rate and body temperature that helps lower their daily energy requirements. As such, torpor often has been cited as a key feature allowing some small endotherms to survive highly unpredictable climates, such as tropics or dry deserts, but mensurative demonstrations of this are lacking. We have shown here that when a small desert marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata), is offered unpredictable levels of daily food, they increase frequency of daily torpor and length of bouts compared with animals offered ad libitum food, but this was not found for animals offered a 70% food-restricted diet. Our data suggest that simple food restriction may not be sufficient for evaluating the efficacy of torpor as a strategy for managing unpredictable climates.     

Fat and fed: frequent use of summer torpor in a subtropical bat

A widely held view is that torpor is avoided by mammals whenever possible because of potential costs associated with reduced body temperatures and slowed metabolic processes. We examined this hypothesis by quantifying use of torpor in relation to body condition of free-ranging northern long-eared bats (Nyctophilus bifax, approximately 10 g), a species known to hibernate, from a subtropical region during the austral summer when insects were abundant. Temperature-telemetry revealed that bats used torpor on 85% of observation days and on 38% of all nights. Torpor bouts ranged from 0.7 to 21.2 h, but the relationship between duration of torpor bouts and ambient temperature was not significant. However, skin temperature of torpid bats was positively correlated with ambient temperature. Against predictions, individuals with a high body condition index (i.e., good fat/energy reserves) expressed longer and deeper torpor bouts and also employed torpor more often during the activity phase at night than those with low body condition index. We provide the first evidence that use of torpor in a free-ranging subtropical mammal is positively related with high body condition index. This suggests that employment of torpor is maximised and foraging minimised not because of food shortages or low energy stores but likely to avoid predation when bats are not required to feed.     

Yearlong hibernation in a marsupial mammal

Many mammals hibernate each year for about 6 months in autumn and winter and reproduce during spring and summer when they are generally not in torpor. I tested the hypothesis that the marsupial pygmy-possum (Cercartetus nanus), an opportunistic nonseasonal hibernator with a capacity for substantial fattening, would continue to hibernate well beyond winter. I also quantified how long they were able to hibernate without access to food before their body fat stores were depleted. Pygmy-possums exhibited a prolonged hibernation season lasting on average for 310 days. The longest hibernation season in one individual lasted for 367 days. For much of this time, despite periodic arousals after torpor bouts of ∼12.5 days, energy expenditure was reduced to only ∼2.5% of that predicted for active individuals. These observations represent the first report on body-fat-fuelled hibernation of up to an entire year and provide new evidence that prolonged hibernation is not restricted to placental mammals living in the cold.     

Torpor and basking in a small arid zone marsupial

The high energetic cost associated with endothermic rewarming from torpor is widely seen as a major disadvantage of torpor. We tested the hypothesis that small arid zone marsupials, which have limited access to energy in the form of food but ample access to solar radiation, employ basking to facilitate arousal from torpor and reduce the costs of rewarming. We investigated torpor patterns and basking behaviour in free-ranging fat-tailed dunnarts Sminthopsis crassicaudata (10 g) in autumn and winter using small, internal temperature-sensitive transmitters. Torpid animals emerged from their resting sites in cracking soil at ∼1000 h with body temperatures as low as 14.6°C and positioned themselves in the sun throughout the rewarming process. On average, torpor duration in autumn was shorter, and basking was less pronounced in autumn than in winter. These are the first observations of basking during rewarming in S. crassicaudata and only the second direct evidence of basking in a torpid mammal for the reduction of energetic costs during arousal from torpor and normothermia. Our findings suggest that although overlooked in the past, basking may be widely distributed amongst heterothermic mammals. Therefore, the energetic benefits from torpor use in wild animals may currently be underestimated.     

Influence of conservation tillage on winter bird use of arable fields in Hungary

Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution.     

Hot bats: extreme thermal tolerance in a desert heat wave

Climate change is predicted to increase temperature extremes and thus thermal stress on organisms. Animals living in hot deserts are already exposed to high ambient temperatures (T _a) making them especially vulnerable to further warming. However, little is known about the effect of extreme heat events on small desert mammals, especially tree-roosting microbats that are not strongly protected from environmental temperature fluctuations. During a heat wave with record T _as at Sturt National Park, we quantified the thermal physiology and behaviour of a single free-ranging little broad-nosed (Scotorepens greyii, henceforth Scotorepens) and two inland freetail bats (Mormopterus species 3, henceforth Mormopterus) using temperature telemetry over 3 days. On 11 and 13 January, maximum T _a was ～45.0 °C, and all monitored bats were thermoconforming. On 12 January 2013, when T _a exceeded 48.0 °C, Scotorepens abandoned its poorly insulated roost during the daytime, whereas both Mormopterus remained in their better insulated roosts and were mostly thermoconforming. Maximum skin temperatures (T _skin) ranged from 44.0 to 44.3 °C in Scotorepens and from 40.0 to 45.8 °C in Mormopterus, and these are the highest T _skin values reported for any free-ranging bat. Our study provides the first evidence of extensive heat tolerance in free-ranging desert microbats. It shows that these bats can tolerate the most extreme T _skin range known for mammals (3.3 to 45.8 °C) and delay regulation of T _skin by thermoconforming over a wide temperature range and thus decrease the risks of dehydration and consequently death.     

Colony disassociation following diet partitioning in a unicolonial ant

Discriminating nestmates from alien conspecifics via chemical cues is recognized as a critical element in maintaining the integrity of insect societies. We determined, in laboratory experiments, that nestmate recognition in an introduced population of the Argentine ant, Linepithema humile, is modified by hydrocarbons acquired from insect prey, and that workers from spatially isolated colony fragments, each provided with prey that possessed distinct cuticular hydrocarbons, displayed aggressive behavior towards their former nestmates. Isolation for 28 days or more between colony fragments fed different prey was sufficient to prevent re-establishment of inter-nest communication for at least an additional 28 days through the introduction of a bridge between the nests. Ants possessed intrinsic cuticular hydrocarbons plus only those hydrocarbons from the prey they received during the isolation period. Colony fragments which were isolated for less than 28 days reunited with workers possessing both prey hydrocarbons. Therefore, L. humile nestmate recognition may be dynamic, being in part dependent on the spatio-temporal distribution of prey, along with physical factors permitting or restricting access of subcolony units to those prey.     

Food remains in Confuciusornis sanctus suggest a fish diet

Despite hundreds of excellent fossils of Confuciusornis, the most abundant group of birds in the Early Cretaceous, ‘Jehol Biota’ in China, there is yet no indication of the food choice of these birds. Here, we describe fish remains preserved in the alimentary system of a specimen of Confuciusornis sanctus from the Jiufotang Formation. This find is about five million years younger than all previously published confuciusornithid birds from the Yixian Formation. Although it is unknown how common fish was in the diet of Confuciusornis, the find does not support previous hypotheses that it fed on plants or grain.     

Vector navigation in desert ants, Cataglyphis fortis: celestial compass cues are essential for the proper use of distance information

Foraging desert ants navigate primarily by path integration. They continually update homing direction and distance by employing a celestial compass and an odometer. Here we address the question of whether information about travel distance is correctly used in the absence of directional information. By using linear channels that were partly covered to exclude celestial compass cues, we were able to test the distance component of the path-integration process while suppressing the directional information. Our results suggest that the path integrator cannot process the distance information accumulated by the odometer while ants are deprived of celestial compass information. Hence, during path integration directional cues are a prerequisite for the proper use of travel-distance information by ants.     

邢台市冬季一次重污染过程PM2.5污染特征分析

为了解邢台市秋冬季重污染过程的污染特征,于2018年11月10-16日,在邢台市一中、内丘以及沙河3个点位采集PM2.5样品,分析PM2.5浓度及其化学组分.结果表明:重污染过程期间邢台市PM2.5平均浓度为176.2 μg/m3,超过GB 3095-2012《环境空气质量标准》二级标准限值1.4倍;水溶性离子以NO3...     

Contribution of anadromous fish to the diet of European catfish in a large river system

Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine δ¹³C value, over 8‰ higher after lipid extraction compared to the mean δ¹³C value of all other potential freshwater prey fish. The δ¹³C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for δ¹³C.     

Torpor use during gestation and lactation in a primate

Torpor is an energy-saving mechanism that allows endotherms to overcome energetic challenges. Torpor should be avoided during reproduction because of potential incompatibility with offspring growth. To test if torpor can be used during gestation and lactation to compensate for food shortage, we exposed reproductive female grey mouse lemurs (Microcebus murinus), a heterothermic primate, to different levels of food availability. Torpor use was characterised by daily skin temperature profiles, and its energetic outcome was assessed from changes in body mass. Food shortage triggered torpor during the end of the gestation period (n = 1), ranging from shallow in response to 40% food restriction to deep daily torpor in response to 80% restriction. During the early period of lactation, females fed ad libitum (n = 2) or exposed to a 40% restriction (n = 4) remained normothermic; but 80% food restricted females (n = 5) gave priority to energy saving, increasing the frequency and depth of torpor bouts. The use of torpor was insufficient to compensate for 80% energetic shortage during lactation resulting in loss of mass from the mother and delayed growth in the pups. This study provides the first evidence that a heterothermic primate can use torpor to compensate for food shortages even during reproduction. This physiological flexibility likely evolved as a response to climate-driven fluctuations in food availability in Madagascar.     

Modelling scenarios towards a sustainable use of natural resources in Europe

Issues related to the unsustainable use of natural resources are currently high on the policy agenda both in Europe and in other world regions. A large number of studies assessed past developments of material use and resource productivities. However, little effort has so far been devoted to forecasting future patterns of natural resource use and to provide ex-ante assessments of environmental and economic effects of different resource policies. This paper presents results from the international research project “MOSUS” (Modelling opportunities and limits for restructuring Europe towards sustainability), which was designed to fill some of these research gaps. In this project, a global economy–energy model system was extended by a worldwide database on material inputs, in order to run three scenarios for European development up to the year 2020: a baseline scenario without additional policy intervention and two so-called “sustainability scenarios”, simulating the implementation of six packages of policy measures geared towards decoupling economic activity from material and energy throughput. These measures included, amongst others, taxes on CO₂ emissions and transport, measures to increase metal recycling rates, and a consulting programme to raise material productivity of industrial production. This paper presents the evaluation of the three scenarios with regard to the extraction of natural resources on the European and global level. In the baseline scenario, used domestic extraction within the EU remains roughly constant until 2020, while unused domestic extraction decreases (particularly overburden from mining activities). The stabilisation of domestic extraction, however, is accompanied by growing imports of material intensive products. This indicates that the material requirements of the European economy will increasingly be met through imports from other world regions, causing shifts of environmental pressures related to material extraction and processing away from Europe towards resource-rich countries. The implementation of the six sustainability policy measures applied in the sustainability scenarios results in a slight absolute reduction of domestic extraction in all European countries and significantly increased resource productivities. The results suggest that policy instruments aimed at raising eco-efficiency on the micro level can be conducive to economic growth. To limit rebound effects on the macro level, these instruments must, however, be accompanied by other policies influencing the prices of energy and materials. With regard to global resource use trends, the baseline scenario forecasts a significant growth of resource extraction, particularly in developing countries, reflecting the growing demand for natural resources of emerging economies such as China and India.     

Estimating the abundance and egg production of spawning winter flounder (Pseudopleuronectes americanus) in the Niantic River,CT for use in the assessment of impact at Millstone Nuclear Power Station

The winter flounder is a coastal flatfish with spawning populations associated with specific estuaries or coastal areas. Because of its stock structure, this species is susceptible to localized impacts, including power plant entrainment of larvae. Winter flounder rank second in fish larvae entrained at the Millstone Nuclear Power Station (MNPS), located on Long Island Sound in Waterford, CT, USA. Because of its importance to the state’s fisheries, the population spawning in the nearby Niantic River was selected for impact assessment studies in the early 1970s. Northeast Utilities has consistently monitored annual abundance of adult spawners, characterizing relative abundance by trawl catch-per-unit-effort (CPUE) and absolute abundance using mark and recapture data with the Jolly model for demographically open populations. Trends in these two independent but highly correlated indices provide short-term assessments of winter flounder abundance. Abundance of winter flounder peaked in the early 1980s, but as fishing mortality increased to high levels in the late 1980s, their numbers declined thereafter and presently are very low. Information on sex ratio, length-frequency distribution, and spawning condition allow for calculation of annual egg production using a length-fecundity relationship. This forms the basis for estimating production loss due to larval entrainment, which is used as input to a long-term assessment model of power plant impact, discussed in an accompanying paper (Lorda et al., 2000: Lorda, E., Danila, D.J., Miller, J.D., 2000. Application of a population dynamics model to the probabilistic assessment of CWIS effects of Millstone Nuclear Power Station (Waterford, CT) on a nearby winter flounder spawning stock. Environmental Science & Policy 3, S471–S481).