Subtropical mouse-tailed bats use geothermally heated caves for winter hibernation.

We report that two species of mouse-tailed bats (Rhinopoma microphyllum and R. cystops) hibernate for five months during winter in geothermally heated caves with stable high temperature (20°C). While hibernating, these bats do not feed or drink, even on warm nights when other bat species are active. We used thermo-sensitive transmitters to measure the bats' skin temperature in the natural hibernacula and open flow respirometry to measure torpid metabolic rate at different ambient temperatures (Ta, 16-35°C) and evaporative water loss (EWL) in the laboratory. Bats average skin temperature at the natural hibernacula was 21.7 ± 0.8°C, and no arousals were recorded. Both species reached the lowest metabolic rates around natural hibernacula temperatures (20°C, average of 0.14 ± 0.01 and 0.16 ± 0.04 ml O2 g(-1) h(-1) for R. microphyllum and R. cystops, respectively) and aroused from torpor when Ta fell below 16°C. During torpor the bats performed long apnoeas (14 ± 1.6 and 16 ± 1.5 min, respectively) and had a very low EWL. We hypothesize that the particular diet of these bats is an adaptation to hibernation at high temperatures and that caves featuring high temperature and humidity during winter enable these species to survive this season on the northern edge of their world distribution.

Macroevolution of life-history traits in passerine birds: adaptation and phylogenetic inertia.

We used a recent passerine phylogeny and comparative method to evaluate the macroevolution of body and egg mass, incubation and fledging periods, time to independence and time with parents of the main passerine lineages. We hypothesised that passerine reproductive traits are affected by adaptation to both past and present environmental factors and phenotypic attributes such as body mass. Our results suggest that the evolution of body and egg mass, time to independence, incubation and fledging times are affected by strong phylogenetic inertia and that these breeding traits are all affected by body mass. Time with parents, where major lineages exhibit their own fixed optima and body mass does not have an effect, and clutch size which is affected by body mass and additionally by climate regimes, do not exhibit any phylogenetic inertia.

In Its Southern Edge of Distribution, the Tawny Owl (Strix aluco) Is More Sensitive to Extreme Temperatures Than to Rural Development.

Populations at the warm edge of distribution are more genetically diverse, and at the same time are more susceptible to climate change. Between 1987-1996, we studied Tawny Owls in Israel, the species' global southern edge of distribution and a country undergoing a rapid land cover transformation for over a century. To assess the potential impacts of land cover transformation, we modelled the species' most suitable habitat and climate and analyzed how climate and habitat affected the nesting success and prey selection. Moreover, we monitored Tawny Owl juveniles' survival and ontogeny from eggs to dietary independent young, to find out whether the Israeli population is a sink. While the species distribution model correctly predicted the Tawny Owl's densest areas of occurrence, it failed to predict its occurrence in adjacent regions. The model also predicted that areas included in the species' historical range remained suitable habitats. The number of fledglings increased with precipitation and in rural settings but was adversely affected by extreme temperatures. While voles dominated the diet in all habitats, the Tawny Owl's diet is considerably more variable than other Israeli owls. Our results suggest that the Tawny Owl can adapt to rural-agricultural environments, but is susceptible to climate change.

Lynx body size in Norway is related to its main prey (Roe deer) density, climate, and latitude.

We studied the effect of various factors on body size variation of the Eurasian lynx in Norway, using data from 374 lynx collected between 1960 and 1976 and whose locality of capture, year of birth, sex, and age were known. Body size of lynx in Norway was mainly affected by sex and age. Female skull size (and by implication body size) was also positively affected by the availability of its main prey (roe deer) and by latitude, and negatively by the North Atlantic Oscillation (NAO). Male size was not affected by any of the environmental factors examined. We interpret the effects of NAO and latitude on body size through their effect on the local climate and particularly snow conditions. We suggest that females are more sensitive to environmental factors than males.

Recent changes in body size of the Eurasian otter Lutra lutra in Sweden.

We studied geographical and temporal body size trends among 169 adult museum specimens of the Eurasian otter (Lutra lutra) collected in Sweden between 1962 and 2008, whose sex, year of collection, and locality were known. Skull size and body mass increased significantly in relation to the year of collection, and skull size (but not body mass) was significantly and negatively related to latitude, contrasting Bergmann's rule and the trend found for Norwegian otters. Latitudinal differences in body size between the two countries may be due to differences in food availability. The temporal increase in body size among Swedish otters resembled that observed for Norway otters, though Swedish otters are smaller with respect to their Norwegian counterparts. Latitude and year represent a combination of environmental factors, including ambient temperature in the year of collection as well as the number of days of ice coverage. We replaced the above factors with mean annual temperature or the number of days of ice coverage, and found that each of these factors explains a similar proportion of the variation in body size as did latitude and year. We hypothesize that this temporal increase in body size is related to a combination of factors, including reduced energy expenditure resulting from increasing ambient temperature, and increased food availability from longer ice-free periods.

Frequent summer nuptial flights of ants provide a primary food source for bats.

In many ant species, nuptial flight tends to be short in time and assumed to be synchronous across a large area. Here, we report that, in the upper Jordan Valley, northern Israel, massive nuptial flights of Carpenter ants (Camponotus sp.) occur frequently throughout the summer, and their alates form up to 90% of the diet of the greater mouse-tailed bat (Rhinopoma microphyllum) during this period. This fat and protein-rich diet enables female bats to lactate during summer, and the large amount of fat that both sexes accumulate may serve as an energy source for their following winter hibernation and posthibernation mating in early spring (March-April). We suggest that the annual movement of these bats to the Mediterranean region of Israel may have evolved in order to enable them to exploit the extremely nutritious forms of ant alates when the bats' energetic demands are highest.

Exploring the Relationship between Brain Plasticity, Migratory Lifestyle, and Social Structure in Birds.

Studies in Passerines have found that migrating species recruit more new neurons into brain regions that process spatial information, compared with resident species. This was explained by the greater exposure of migrants to spatial information, indicating that this phenomenon enables enhanced navigational abilities. The aim of the current study was to test this hypothesis in another order-the Columbiformes - using two closely-related dove species-the migrant turtle-dove (Streptopelia turtur) and the resident laughing dove (S. senegalensis), during spring, summer, and autumn. Wild birds were caught, treated with BrdU, and sacrificed 5 weeks later. New neurons were recorded in the hyperpallium apicale, hippocampus and nidopallium caudolaterale regions. We found that in doves, unlike passerines, neuronal recruitment was lower in brains of the migratory species compared with the resident one. This might be due to the high sociality of doves, which forage and migrate in flocks, and therefore can rely on communal spatial knowledge that might enable a reduction in individual navigation efforts. This, in turn, might enable reduced levels of neuronal recruitment. Additionally, we found that unlike in passerines, seasonality does not affect neuronal recruitment in doves. This might be due to their non-territorial and explorative behavior, which exposes them to substantial spatial information all year round. Finally, we discuss the differences in neuronal recruitment between Columbiformes and Passeriformes and their possible evolutionary explanations. Our study emphasizes the need to further investigate this phenomenon in other avian orders and in additional species.

Ecotypic variation in the context of global climate change: revisiting the rules.

Patterns of ecotypic variation constitute some of the few 'rules' known to modern biology. Here, we examine several well-known ecogeographical rules, especially those pertaining to body size in contemporary, historical and fossil taxa. We review the evidence showing that rules of geographical variation in response to variation in the local environment can also apply to morphological changes through time in response to climate change. These rules hold at various time scales, ranging from contemporary to geological time scales. Patterns of body size variation in response to climate change at the individual species level may also be detected at the community level. The patterns underlying ecotypic variation are complex and highly context-dependent, reducing the 'predictive-power' of ecogeographical rules. This is especially true when considering the increasing impact of human activities on the environment. Nonetheless, ecogeographical rules may help interpret the likely influences of anthropogenic climate change on ecosystems. Global climate change has already influenced the body size of several contemporary species, and will likely have an even greater impact on animal communities in the future. For this reason, we highlight and emphasise the importance of museum specimens and the continued need for documenting the earth's biological diversity.

Indirect flight of an African bat to Israel: an example of the potential for zoonotic pathogens to move between continents.

The transmission of harmful pathogens during commercial air flights is an increasing health concern. A potential, yet relatively overlooked source of zoonotic infectious diseases involves collisions of birds and bats with aircraft and long distance transport of their carcasses. We report a case of aerial transportation of the remains of an African fruit bat over three continents, following a collision with an aircraft, and demonstrate the relative ease with which zoonotic pathogens, such as rabies virus or other viruses associated with bats, may cross national boundaries and continents even. Improper handling and disposal of animal remains by airport personnel, may lead to exposure of both humans and local fauna to exotic pathogens. This in turn may trigger an epidemic with potentially devastating results.

Possible linkage between neuronal recruitment and flight distance in migratory birds.

New neuronal recruitment in an adult animal's brain is presumed to contribute to brain plasticity and increase the animal's ability to contend with new and changing environments. During long-distance migration, birds migrating greater distances are exposed to more diverse spatial information. Thus, we hypothesized that greater migration distance in birds would correlate with the recruitment of new neurons into the brain regions involved with migratory navigation. We tested this hypothesis on two Palearctic migrants - reed warblers (Acrocephalus scirpaceus) and turtle doves (Streptopelia turtur), caught in Israel while returning from Africa in spring and summer. Birds were injected with a neuronal birth marker and later inspected for new neurons in brain regions known to play a role in navigation - the hippocampus and nidopallium caudolateral. We calculated the migration distance of each individual by matching feather isotopic values (δ(2)H and δ(13)C) to winter base-maps of these isotopes in Africa. Our findings suggest a positive correlation between migration distance and new neuronal recruitment in two brain regions - the hippocampus in reed warblers and nidopallium caudolateral in turtle doves. This multidisciplinary approach provides new insights into the ability of the avian brain to adapt to different migration challenges.

Woodpecker cavity aeration: a predictive model.

We studied characteristics of the Syrian woodpecker (Dendrocopos syriacus) cavities in the field and a laboratory model, and rates of gas exchange in the laboratory. Night temperature of occupied cavities is 4.3 degrees C higher than empty ones, representing energy savings of approximately 24%. Oxygen conductance (GNO2) of an empty cavity is 7.1 ml[STPD] (Torr h)(-1), and is affected by winds at velocities up to 0.8 m/s. Day and night body temperatures were 42.0 and 40.1 degrees C, respectively. Steady-state O2 consumption rates (MO2) were 3.49 +/- 0.49 and 2.53 +/- 0.26 ml[STPD] (g h)(-1) during day and night respectively -- higher than predicted by allometry. A mathematical model describing PO2 in a cavity, taking into consideration MO2, GNO2, heat convection and wind speed, from the moment birds inhabit it, was developed. It shows that on the average, one woodpecker staying in its cavity at night does not encounter hypoxic conditions. However, in nest cavities with below the average GNO2, with more inhabitants (e.g. during the breeding season), hypoxia may become a problem.

The reproductive rates of Australian rodents.

The reproductive rates of about 50 species of Australian rodents were studied by calculating allometric equations for the relationships between female body weight, litter size, length of gestation and weaning periods as well as age of sexual maturity.Members of the subfamily Hydromyinae, which invaded Australia 5-10 million years ago, are characterised by small litters, long gestation and weaning periods and late maturity. The opposite is true for the Murinae (Rattus and Mus) which invaded Australia during the Pleistocene. Among the species of this latter group, those which invaded earlier have reproductive rates closer to the old invaders, while those which arrived with the Europeans during the last 200 years have the highest reproductive rates.Possible reasons for the low reproductive rates of Australian rodents are discussed. It is concluded that the rain forest origin of the hydromyinids is one of the factors responsible for their low reproductive rate. They maintained this rate to the present time because of the unpredictability of the climate and the low productivity of many Australian habitats.

A winter feeding experiment on an island Song Sparrow population.

Supplemental food, in the form of millet seed, was provided to half of an island Song Sparrow population during the 1978-1979 winter to test if winter food influenced: (1) overwinter survival; (2) winter wights; (3) breeding density in 1979 and (4) 1979 breeding performance.Territorial males were most dominant at feeders and may have restricted access of young to feeders. Young females were most subordinate at feeders. Adult survival was not affected by supplementary food, but young survival was higher than in 6 previous years and young seen to visit feeders may have survived better than young not seen at feeders. Young females were more variable in weight on the unfed half of the island than on the fed end. The breeding population increased by 38% from 1978 to 1979, but it is not known how much of this increase resulted from food addition. Pairs of birds with feeders on their territories began to lay 25 days earlier in 1979 than control pairs, but delayed longer than controls before a second breeding attempt. One-year old females began to lay significantly later than adults on the control area, but not on the fed area. Other measures of breeding performance were not affected by supplemental food. Winter food may be more important and male territorial behaviour less important than previously supposed in limiting numbers in the Mandarte Island Song Sparrow population.

A possible relation between new neuronal recruitment and migratory behavior in Acrocephalus warblers.

Evidence suggests a possible correlation between learning abilities of adults and new neuronal recruitment into their brains. The hypothesis is that this brain plasticity enables animals to adapt to environmental changes. We examined whether there are differences in neuronal recruitment between resident and migrant birds. We predicted that migrants, which are more exposed to spatial changes than residents, will recruit more new neurons. To test this, we compared neuronal recruitment in two closely related bird species - the migrant reed warbler (Acrocephalus scirpaceus), and the resident Clamorous warbler (A. Stentoreus) - during spring, summer, and autumn. Wild birds were caught, treated with BrdU and sacrificed five weeks later. New neurons were recorded in the Hippocampus and Nidopallium caudolateral. The results support our hypothesis, as more new neurons were found in the migrant species, in both brain regions and all seasons. We suggest that this phenomenon enables enhanced navigational abilities, which are required for the migratory lifestyle. However, in contrast to our hypothesis, in spring we found less new neurons in adults of both species, as compared to other seasons. We suggest that in spring, when birds settle in breeding territories, they require less spatial skills, and this might enable to reduce the cost of neuronal recruitment, as reflected by less new neurons in their brains. We also found age differences, with overall higher neuronal recruitment in juveniles. Finally, we advocate the importance of studying wild populations, for a better understanding of the adaptive significance of neuronal replacement in the vertebrate brain.

Changes in diet, body mass and fatty acid composition during pre-hibernation in a subtropical bat in relation to NPY and AgRP expression.

Prior to hibernation, mammals accumulate large amounts of fat in their bodies. In temperate mammalian species, hibernation is improved by increasing the levels of poly-unsaturated fatty acids (PUFA) in the body. The saturation of fatty acids (FA) in both white adipose tissue (WAT) and membrane phospholipids of mammals often reflects their diet composition. We found that the greater mouse-tailed bat (Rhinopoma microphyllum) accumulates large amounts of fat at the end of summer by gradually shifting to a fat-rich diet (queen carpenter ants, Camponotus felah). PUFA are almost absent in this diet (<1 % of total FA), which contains a high fraction of saturated (SFA) and mono-unsaturated (MUFA) fatty acids. We found similar low levels of PUFA in mouse-tailed bat WAT, but not in their heart total lipids. The expression of two appetite-stimulating (orexigenic) hypothalamic neuropeptides, AgRP and NPY, increased in parallel to the shift in diet and with fat gain in these bats. To the best of our knowledge, this is the only documented example of specific pre-hibernation diet in bats, and one which reveals the most saturated FA composition ever documented in a mammal. We suggest that the increase in expression levels of NPY and AgRP may contribute to the observed diet shift and mass gain, and that the FA composition of the bat's specialized diet is adaptive in the relatively high temperatures we recorded in both their winter and summer roosts.

Bats of a gender flock together: sexual segregation in a subtropical bat.

Competition has long been assumed to be a major driver in regulating ecological communities. Intra-specific competition is considered to be maximal as members of the same species use the same ecological niches in a similar way. Many species of animals exhibit great physiological, behavioral, and morphological differences between sexes (sexual dimorphism). Here we report an extreme geographical segregation between the sexes in the greater mouse-tailed bat (Rhinopoma microphyllum). To gain insight into the driving mechanisms of sexual segregation outside the mating season, we collected and integrated environmental, behavioral, physiological, and spatial information. We found that both sexes choose roosts with similar characteristics and the same food type, but use different habitats for different durations. Males forage around cliffs at higher and cooler elevations while females forage in lowlands around a river delta. We suggest that it is their different physiological and social needs, and not competition, that drives sexual segregation in this species.

Recent spatial and temporal changes in body size of terrestrial vertebrates: probable causes and pitfalls.

Geographical and temporal variations in body size are common phenomena among organisms and may evolve within a few years. We argue that body size acts much like a barometer, fluctuating in parallel with changes in the relevant key predictor(s), and that geographical and temporal changes in body size are actually manifestations of the same drivers. Frequently, the principal predictors of body size are food availability during the period of growth and ambient temperature, which often affects food availability. Food availability depends on net primary productivity that, in turn, is determined by climate and weather (mainly temperature and precipitation), and these depend mainly on solar radiation and other solar activities. When the above predictors are related to latitude the changes have often been interpreted as conforming to Bergmann's rule, but in many cases such interpretations should be viewed with caution due to the interrelationships among various environmental predictors. Recent temporal changes in body size have often been related to global warming. However, in many cases the above key predictors are not related to either latitude and/or year, and it is the task of the researcher to determine which particular environmental predictor is the one that determines food availability and, in turn, body size. The chance of discerning a significant change in body size depends to a large extent on sample size (specimens/year). The most recent changes in body size are probably phenotypic, but there are some cases in which they are partly genetic.

Reproductive rates in Australian rodents are related to phylogeny.

BACKGROUND: The native rodents of Australia are commonly divided into two groups based on the time of their colonization of the Sahulian continent, which encompasses Australia, New Guinea, and the adjacent islands. The first group, the "old endemics," is a diverse assemblage of 34 genera that are descended from a single colonization of the continent during the Pliocene. A second group, the "new endemics," is composed of several native Rattus species that are descended from a single colonization during the Pleistocene. Finally, a third group is composed of three non-native species of Rattus and Mus introduced into Australia by humans over the last 200 years. Previous studies have claimed that the three groups differ in their reproductive rates and that this variation in rates is associated with the unique environmental conditions across Australia. We examined these hypotheses using phylogenetically controlled methods. METHODOLOGY AND RESULTS: We examined the relationship between the reproductive rates of the Australian rodents and the environmental variations across the continent, as well as the epoch of their colonization of the continent. Our results revealed no significant correlation with environmental variables but a significant association between colonization age and all the reproductive parameters examined. DISCUSSION: Based on a larger phylogeny of the subfamily Murinae, we showed that significant differences in reproductive rates among colonization groups are shared with their closest relatives outside Sahul. Therefore, the lower reproductive rates in the old endemics are more likely to be the result of phylogenetic history and conservation of traits than an adaptation to the Australian environment. In the new endemics, we found a trend of increasing reproductive rates with diversification. We suggest that the differences in reproductive rates of the old endemic rodents and the native Rattus represent alternative adaptive strategies that have allowed them to utilize similar ecological niches across Australia.

Population cycles and changes in body size of the lynx in Alaska.

The lynx Lynx canadensis is a common predator in the boreal forests of North America. Its population fluctuates during a 9- to 11-year cycle in synchrony with the population size of its main prey, the snowshoe hare Lepus americanus. Using adult museum specimens, we studied changes in skull (and hence body) size of the lynx in Alaska during the second half of the 20th century. The population cycle in Alaska averaged 9 years, similar to that reported in the neighbouring Yukon. Using harvest data of lynx as an estimate of population size, we found that skull size was negatively related to population size. This relationship was strongest not for the population density in the year of death (X), but for year X-3, a carry-over effect from the first year (or years) of life, indicating that conditions during the fast-growth years are determining body size. We suggest that the density-dependent effect is probably due to changes in food supply, either resulting from the adverse effects of competition or a possible diminished availability of food. Two skull parameters decreased significantly during the second half of the 20th century. We do not know the cause for the year effect and suggest that it might be due to a long-term change in the availability of prey. Canine size did not change during the study period, probably an indication that snowshoe hares maintained their status as the main prey of the lynx throughout the study period.

Geographic variation in body size: the effects of ambient temperature and precipitation.

Latitudinal trends in body size have been explained as a response to temperature- or water-related factors, which are predictors of primary production. We used the first principal component calculated from three body parameters (weight, body length and the greatest length of the skull) of a sample of mammals from Israel and Sinai to determine those species that vary in size geographically, and whether such variation is related to annual rainfall, average minimum January temperature and average maximum August temperature. We used a conservative approach to discern the effects of precipitation and temperature by applying sequential regression. Variable priorities were assigned according to their bivariate correlation with body size, except for rainfall and its interactions that entered into the model last. Eleven species (Acomys cahirinus, Apodemus mystacinus, Canis lupus, Crocidura suaveolens, Gerbillus dasyurus, Hyaena hyaena, Lepus capensis, Meles meles, Meriones tristrami, Rousettus aegyptius and Vulpes vulpes) of the 17 species examined varied in size geographically. In five of them, rainfall was positively related to body size, while in one species it was negatively related to it. Contrary to the prediction of Bergmann's rule, mean minimum January temperature was positively related to body size in five species and negatively related to body size in two species (C. suaveolens and G. dasyurus). As predicted by Bergmann's rule, maximum June temperature was negatively related to body size in three species, and positively so in one (L. capensis). Primary production, particularly in desert and semi-desert areas, is determined mainly by precipitation. The above results indicate that, in our sample, primary production has an important effect on body size of several species of mammals. This is evident from the considerable proportion of the variability in body size explained by rain. However, low ambient temperatures may slow down and even inhibit photosynthesis. Hence, the observed positive relationships between average minimum January temperature and body size in four of the six species influenced by rain further support this conclusion.