Recent years have seen an increase in the number of publications on bat migration and an overall growing interest among bat researchers that culminated in the 1st International Symposium on Bat Migration in Berlin in January 2009. Here, we summarize the most recent findings about the biology and behavior of migratory bats and the phenomenon of bat migration, discuss the methods that were used to obtain them, draw attention to the challenges that migratory bats face in our changing world, and provide a few suggestions that may encourage researchers to conduct further work in this promising field.

Many species of bats undergo annual migrations, in some cases covering distances of 1,000 km or more. However, very little is known about the physiological and biochemical mechanisms underlying bat migration. In contrast, the physiology of migrating birds has been studied for decades and many migration-related changes have been documented. Although bats and birds evolved flight and long-distance migration independently, they have likely experienced many similar selective pressures. We therefore suggest that knowledge of bird migration physiology can be used to generate predictions for emerging studies of bat migration physiology. In this review, we discuss major physiological and biochemical adaptations relating to fuel acquisition and fuel utilization. For each, we summarize knowledge gained from migration studies of birds and bats (if any) and make predictions of bat migration physiology. For many aspects, we predict that bats will have evolved similar physiological mechanisms to birds. However, there are some potentially major differences in the energetic models for bats and birds, including torpor, fuel selection at high-intensity exercise, and trade-offs between reproduction and migration.

This paper introduces some theoretical concepts based on optimality theory that may be applied to bat migration. Most predictions are based on flight mechanics and potential flight range. Optimal behavior will depend on the relevant immediate currency, such as safety, time, or energy. Predictions concern optimal flight speeds, stopover duration, fuel load at departure, and the adaptive use of winds. I also consider a criterion for fuel management when bats are migrating between summer and hibernation sites. The overall migration speed is predicted to be 46 km/day for a small (10-g) bat, and banding recoveries in Nathusius's bat (Pipistrellus nathusii) showed a mean speed of 47 km/day. The timing of migration in bats that minimizes the time spent in migration is considered a result of the trade-off between seasonally increased length of the night (decreased in spring) and reduction of aerial insect abundance. Most predictions remains to be tested; the theoretical framework herein offers a point of departure when designing new field or laboratory studies of bat migration.

Several European bat species migrate long distances of >1,000 km, but information on migration routes is poor or anecdotal, or both. We investigated migration of bats along the Oder River valley in southwestern Poland to determine the significance of large river valleys as migration corridors for bats. We determined direction of bat movements from visual observations and sequence of echolocation signals received by 2 bat detectors, from March to November 2007. The predominant activities of bats were directional flights in spring (March–May) and autumn (mid-August–October) and foraging in summer (June–July). In spring, most bats flew northward, and in autumn, southward. In autumn, the movement occurred over a longer time and there were fewer bats migrating than in spring. We conclude that river valleys are migration flyways for bats that travel long distances and those that travel short distances, and that differences between spring and autumn migration may be related to food supply, to energy demands, to seasonally different routes, or to a combination of these factors.

We studied bats migrating and foraging over the sea by direct observations and automatic acoustic recording. We recorded 11 species (of a community of 18 species) flying over the ocean up to 14 km from the shore. All bats used sonar during migration flights at sea, often with slightly lower frequencies and longer pulse intervals compared to those used over land. The altitude used for migration flight was most often <10 m above sea level. Bats must use other sensory systems for long-distance navigation, but they probably use echoes from the water surface to orient to the immediate surroundings. Both migrant and resident bats foraged over the sea in areas with an abundance of insects in the air and crustaceans in the surface waters. When hunting insects near vertical objects such as lighthouses and wind turbines, bats rapidly changed altitude, for example, to forage around turbine blades. The findings illustrate why and how bats might be exposed to additional mortality by offshore wind power.

Migrating bats are among the most poorly understood of migratory taxa, with relatively little information available on their behavior and ecology during migration compared to other taxa. This arises because of the “small animal problem,” namely the limitations of current technology to track individual animals that weigh <190 g. In this paper (which is not a comprehensive review of bat migration) we assess the limits of current techniques available to study the migratory behavior of individual bats and what is needed to take the study of the behavior and ecology of migrating bats forward.

Thousands of industrial-scale wind turbines are being built across the world each year to meet the growing demand for sustainable energy. Bats of certain species are dying at wind turbines in unprecedented numbers. Species of bats consistently affected by turbines tend to be those that rely on trees as roosts and most migrate long distances. Although considerable progress has been made in recent years toward better understanding the problem, the causes of bat fatalities at turbines remain unclear. In this synthesis, we review hypothesized causes of bat fatalities at turbines. Hypotheses of cause fall into 2 general categories—proximate and ultimate. Proximate causes explain the direct means by which bats die at turbines and include collision with towers and rotating blades, and barotrauma. Ultimate causes explain why bats come close to turbines and include 3 general types: random collisions, coincidental collisions, and collisions that result from attraction of bats to turbines. The random collision hypothesis posits that interactions between bats and turbines are random events and that fatalities are representative of the bats present at a site. Coincidental hypotheses posit that certain aspects of bat distribution or behavior put them at risk of collision and include aggregation during migration and seasonal increases in flight activity associated with feeding or mating. A surprising number of attraction hypotheses suggest that bats might be attracted to turbines out of curiosity, misperception, or as potential feeding, roosting, flocking, and mating opportunities. Identifying, prioritizing, and testing hypothesized causes of bat collisions with wind turbines are vital steps toward developing practical solutions to the problem.

Little is known regarding the migratory behavior of bats, due in part to their elusive nature. Recently, however, fatalities of migratory bats at some wind energy facilities across North America have provided the opportunity and impetus to study bat migration at the landscape level. Using acoustic monitoring and carcass searches, we examined variation in activity levels and fatality rates of bats across southern Alberta, Canada, to determine if bat activity and fatality are concentrated in certain areas or evenly distributed across the landscape. To investigate geographical variation in bat activity, we acoustically monitored activity from 15 July to 15 September 2006 and 2007 at 7 proposed or existing wind energy installations across southern Alberta (∼155 km between the most westerly wind energy facility and the most easterly). Activity of migratory bats varied among sites, suggesting that, rather than migrating in a dispersed way across a broad area, bats concentrate along select routes. To investigate variation in bat fatality rates among wind energy installations, we compiled fatality data collected between 2001 and 2007 from 6 wind energy facilities and conducted carcass searches at 3 wind energy installations in 2006 and 2007. Fatality rates differed among the 9 sites, partly due to differences in turbine height, but also due to differences in migratory-bat activity and the interaction between bat activity and turbine height. Our results indicate that bats migrate in certain areas and that measuring migratory activity may allow wind energy facilities to be placed so as to minimize bat fatalities.

We investigated the activity patterns of platypuses, Ornithorhynchus anatinus, at Lake Lea, a subalpine lake in Tasmania. Platypuses were equipped with activity loggers or time–depth recorders, which allowed constant recordings for up to 48 days. The recordings revealed an unexpectedly high variety of foraging behaviors. Although nocturnal activity, as reported from other habitats, was still predominant, diurnal activity as well as highly fragmented activity patterns were common. Mean foraging duration was 12.4 h/day, with some animals foraging continuously for up to 29.8 h. Daily emergence and return times as well as durations of daily foraging trips varied considerably. At least 2 animals showed a distinct shift in activity pattern related to the lunar cycle. Season and water temperature affected platypus behavior. Foraging durations were longer and activity levels were higher in winter. In contrast to observations in river systems, temporal separation likely served as a mechanism to avoid intraspecific competition, and was particularly important for adult males during the breeding season. Dominant males were preferentially nocturnal, whereas lower-ranked males adopted more variable or fragmented activity patterns.

The monito del monte (Dromiciops gliroides) is an arboreal marsupial found only in austral South American temperate rain forests. Its conservation is a priority as the only extant species of the order Microbiotheria. We investigated whether the apparent low abundances reported for D. gliroides are real, or reflect a sampling artifact. We used wire-mesh and Sherman live traps, devices for recording tracks and hair, 2 types of bait, and 2 trap placements (ground level and 1.5–2.5 m high) in an old-growth forest in southern Chile. Type of bait and placement height affected captures of D. gliroides. The most efficient trapping combination (wire-mesh traps baited with banana, and placed above ground) yielded capture rates of up to 11%, and a relative population density of 21 ± 5 individuals/ha (mean ± SE), whereas traditional methods used for sampling small mammals were not effective. The sampling artifact uncovered here may have important future management and conservation implications.

Nine-banded armadillos (Dasypus novemcinctus) are the only free-ranging vertebrates other than humans known to exhibit naturally occurring infections of Mycobacterium leprae, the causative agent of leprosy, but little is known about ecological consequences of leprosy in wild populations. We studied a population of armadillos in western Mississippi during the summers of 2007 and 2008. Consistent with previous work, we found no evidence of leprosy in juveniles or yearlings, suggesting no vertical transmission of disease. In 2008, a higher proportion of adult females were leprosy-positive than were adult males. Across both years, leprous females were significantly larger than nonleprous females, but a higher proportion of leprous females were lactating and lactating females were larger than nonlactating females. The behavior of leprosy-positive and leprosy-negative animals did not differ. Leprosy-positive individuals tended to be spatially clumped, but these results were not statistically significant. Our findings suggest leprosy had minimal impacts on individuals in this population of armadillos, which is a surprising and unexpected result given the substantial costs of infection documented in the laboratory.

The social and genetic mating systems of species can differ. This discrepancy occurs in many birds; however, only 2 studies have examined this issue for shrews, and both were conducted on species that live in temperate regions. We provide the 1st spatial and genetic data to reveal the mating system of the Asian lesser white-toothed shrew (Crocidura shantungensis) in a subtropical region. We tested the hypothesis that the mating system of shrews in the subfamily Crocidurinae is monogamous in subtropical or tropical regions with seasonal climate and resource availability. We used capture–mark–recapture methods to assess spatial organization of shrews during the reproductive season in 2006, and applied 8 microsatellite primers to perform parentage analyses and examine multiple paternity within litters. Males had larger home ranges than females, and the home ranges of resident females, but not males, overlapped with more opposite-sex than same-sex individuals. This spatial structure suggested a polygynous social mating system. Molecular analyses demonstrated that both females and males mated with multiple individuals, and the frequency of multiple paternity was 28%, which supported a promiscuous genetic mating system. Our results rejected the hypothesis that the mating system of C. shantungensis is monogamy in subtropical northern Taiwan.

The genetic structure of brown hyena (Hyaena brunnea) populations in any part of their distribution is unknown. Brown hyenas live in clans whose territories and membership change, making nongenetic estimates of population structure and relatedness among individuals difficult to establish. Sixty-one brown hyenas from the west coast of Namibia were genotyped at 10 microsatellite loci designed for the spotted hyena (Crocuta crocuta). We found reduced microsatellite variation in brown hyenas compared to spotted hyenas. Using nonhierarchical analyses we detected no major genetic subdivisions across the area sampled in Namibia, but weak differentiation among 2 clans in the southern portion of the range. Females within clans were significantly more related (r_wc♀♀  =  0.34 ± 0.072 SE) than females between clans (r_bc♀♀  =  0.022 ± 0.033) and than females and males in clans (r_wc♀♂  =  0.058 ± 0.076). Examination of these data indicates that dominant males were not related to dominant females and that there is multiple paternity within clans.

Based on 15 years of observations of a badger (Meles meles) population at Wytham Woods in the central United Kingdom, we investigated which parameters governed demographic changes, using data recording the life histories of 868 individuals. We modeled the population in terms of a stage-classified matrix, giving an exponential population growth rate of r  =  0.063 (λ  =  1.065). Population elasticity values, derived from this matrix, produced a relative order of importance of regulatory parameters governing this population growth rate, of: adult survival (P_a) > fertility (F) > juvenile survival (P_j) > age at 1st reproduction (α) > age at last reproduction (ω). Thus, changes in P_a and F have the greatest potential to influence population growth rate. The population underwent a dramatic change in the last 5 years of the study, with a decline, then stabilization in population growth. However, this change was not related to any change in elasticity patterns between the 2 periods. Comparing the latter period to the preceding period of marked population growth revealed that fertility rate had little actual influence, whereas adult and juvenile survival rates were far more influential demographic variables. These findings prompted a 2nd, retrospective, analytical approach, a life-table response experiment (LTRE), revealing that the importance of P_j in the LTRE contrasted with its lesser prospective importance in the elasticity analysis. Change in fertility (ΔF) apparently had little environmental or genetic scope (according to the results of either technique) to influence regulation in this population. We also tested for delayed density dependence using the theta logistic model. Because territorial animals are expected to respond quickly to the effects of density dependence, corresponding to theta < 1, our rejection of this hypothesis indicated that the restrictions of territorial sociospatial regulation are relaxed in this badger population. These results are used to highlight population vulnerabilities.

Intraguild competition may be reduced if ecologically similar species segregate temporally. Using data from 1,596 camera-trap photos, we present the 1st quantitative analyses of the activity patterns of Andean cats (Leopardus jacobita), Pampas cats (Leopardus colocolo), culpeos (Lycalopex culpaeus), and pumas (Puma concolor) in high-altitude deserts of the Andes. We compared daily activity patterns for these carnivores with those of mountain vizcachas (Lagidium viscacia), the main prey of Andean cats. Activity patterns of all species were positively skewed toward night. Pampas cats displayed the greatest proportion of nocturnal activity, whereas Andean cats were the most diurnal. Activity of Andean cats differed significantly only from that of Pampas cats; Pampas cats also differed from pumas. Activity of Andean cats was generally similar to that of mountain vizcachas. The dissimilar activity patterns of Andean and Pampas cats support the hypothesis of temporal niche segregation of these felids.

Spatial or temporal isotopic variation, or both, in primary producers must be controlled for when investigating the foraging and trophic ecology of top consumers using isotopic data. Populations of the sister species Zalophus californianus and Z. wollebaeki are separated by approximately 3,350 km in the eastern tropical Pacific Ocean, which prevents contact and mixing between the 2 populations. To explore differences in trophic ecology between these species, as well as the impact of differences in baseline food-web isotope values between the 2 regions, we compared conventional dietary data derived from analyses of scat contents to isotopic values of hair collected from pups at 13 rookeries in the Gulf of California (Z. californianus) and 11 rookeries on the Galápagos Islands (Z. wollebaeki). Mean ± 1 SD δ¹³C and δ¹⁵N values were −15.9‰ ± 0.5‰ and 21.8 ± 0.7‰ in the Gulf of California, whereas for the Galápagos they were −14.5‰ ± 0.5‰ and 13.1‰ ± 0.5‰. Examination of scat data suggested overlap in 6 of the 10 most common prey consumed by sea lions. Trophic level (TL) derived from scat analysis was positively related with δ¹⁵N values for the Gulf of California rookeries, but estimates of TL for each region were similar (4.4 for Galápagos and 4.1 for Gulf of California), suggesting that foraging behavior makes a limited contribution to the large difference in δ¹⁵N value between the 2 populations. Particulate organic matter δ¹⁵N values near the Galápagos Islands are ∼5.3‰ lower than values in the Gulf of California, suggesting that the baseline food-web values account for approximately two-thirds of the observed difference in pup hair δ¹⁵N values. This study may provide clues to better understand isotopic values of marine top predators migrating across the eastern Pacific Ocean.

Adult male Alpine ibex (Capra ibex ibex) have been shown to exhibit unusually high survival to relatively advanced ages (>10 years), leading to speculation that males may engage in an energetically conservative reproductive strategy that increases survival. We investigated the extent to which the adoption of alternative mating tactics contributes to the extraordinary survival of adult males in this species. Because basic information on the mating system of Alpine ibex is scarce, we 1st characterized the temporal and spatial distribution of receptive females. Our observations during 3 consecutive rutting seasons revealed 2 alternative mating tactics. Apparently dominant males monopolized individual receptive females by following and defending them, a tactic known as tending. In contrast, apparently subordinate males tried to achieve temporary access to tended females when the latter started to run, a tactic referred to as coursing. In total, 24 copulations were observed, of which 20 (83.3%) were the result of tending and 4 were the result of coursing. The adoption of the 2 tactics was strongly age-dependent; older males (9–12 years) engaged primarily in tending, whereas younger males (2–6 years) engaged mainly in coursing. Males adopting the coursing tactic spent more time in low-cost and less time in high-cost behaviors than males adopting the tending tactic. Time-budget comparisons with another ungulate species suggested that although tending is a relatively costly tactic, coursing is a low-cost tactic that may contribute to the exceptional adult survival in male Alpine ibex.

Previous studies of distribution and habitat use by meadow jumping mice (Zapus hudsonius) have focused on local habitat associations. Our objectives were to predict occupancy of meadow jumping mice and identify local-, patch-, and landscape-specific factors correlated with the species' occurrence. We livetrapped for 5 consecutive days at each of 922 sites during summers of 2001–2003 in thirty-five 23-km² landscapes located across the upper Wabash River basin, Indiana. At 474 of these sites (300 forest and 174 grassland), we measured local habitat variables and computed metrics of patch size, shape, and isolation. Meadow jumping mice were captured 242 times at 69 of the 474 sites. The species did not associate with grassland habitat more frequently than forest habitat and was slightly more likely to be captured in forested corridors than in forest patches. Occupancy models fitted separately for grassland and forest sites revealed positive effects of stem density <1 m (forest) and 1–2 m (grassland) aboveground, but no effects of patch attributes. Probability of detection increased with lower temperatures at forest sites. Surprisingly, the extent of grasslands in landscapes had no effect on overall occupancy rates. Instead, variation in mean site-specific occupancy estimates among landscapes was related to the amount of forest cover; more heavily forested landscapes exhibited greater overall occupancy probabilities. Tests failed to identify a critical threshold of forest cover below which occupancy declined at an accelerated rate. More powerful tests are needed, because the existence of a threshold could have important implications for long-term viability of meadow jumping mice across the basin.

The Fire and Fire Surrogate study—a replicated, manipulative experiment—sought the most economically and ecologically efficient way to restore the nation's fire-maintained ecosystems. As part of this study, we conducted a 3-year mark–recapture study, comprising 105,000 trap-nights, to assess demographic responses of cotton mice (Peromyscus gossypinus) to Fire and Fire Surrogate treatments at the Gulf Coastal Plain site, where longleaf pine was the ecosystem to be restored. We compared competing models to evaluate restoration effects on variation in apparent survival and recruitment over time, space, and treatment, and incorporated measures of available source habitat for cotton mice with reverse-time modeling to infer immigration from outside the study area. The top-ranked survival model contained only variation over time, but the closely ranked 2nd and 3rd models included variation over space and treatment, respectively. The top 4 recruitment models all included effects for availability of source habitat and treatments. Burning appeared to degrade habitat quality for cotton mice, showing demographic characteristics of a sink, but treatments combining fire with thinning of trees or application of herbicide to the understory appeared to improve habitat quality, possibly creating sources. Bottomland hardwoods outside the study also acted as sources by providing immigrants to experimental units. Models suggested that population dynamics operated over multiple spatial scales. Treatments applied to 15-ha stands probably only caused local variation in vital rates within the larger population.

Burrowing behavior is widespread among mammals and has generated a diverse array of adaptive responses to the physical demands of this lifestyle. While extensive research has been devoted to the morphological, ecological, and evolutionary implications of burrowing, it remains difficult to compare burrowing adaptations between mammals of widely divergent ancestry. A reliable quantitative proxy for fossoriality (burrowing) is necessary for such comparisons as well as for detailed descriptions of ecology from specimens of rare, extinct, and fossil mammals. This study presents several quantitative indices of the morphology of burrowing mammals based on 20 measurements of skull and skeletal morphology taken from 123 different mammalian species, both burrowing and nonburrowing. Discriminant analyses revealed that these quantitative characters successfully distinguish nonburrowing taxa from those that are adapted to a burrowing lifestyle. Additionally, more subtle distinctions between subterranean taxa (which rarely emerge above ground) and other burrowers as well as between mammals using different methods of burrow excavation were identified from these characters. A test of these indices using 6 extinct species yielded results consistent with more-detailed descriptions of the functional morphology of these taxa, indicating that our quantitative proxies provide an important basis for comparisons of fossorial adaptations across divergent mammalian clades.

The breadth of an animals' ecological niche is circumscribed by its morphology, performance, and behavior, 3 factors that can ultimately affect fitness. We investigated potential behavioral and performance adaptations to roost making, a life-history trait associated with high fitness in the insectivorous bat Lophostoma silvicolum. Males of this species use their teeth to excavate roosts in active termite nests, which we found to be much harder than the hardest prey in the bats' diet (beetles). We compared roost making and feeding behavior in L. silvicolum. We also compared the feeding behavior of L. silvicolum to that of 2 similar species that do not excavate roosts. All 3 species predominantly used bilateral bites centered on the premolar and molar teeth to eat beetles. In contrast, L. silvicolum used mainly bilateral bites involving the incisors and canines for roost excavation. All species generated similar bite forces during biting behaviors associated with feeding, but L. silvicolum generated significantly higher bite forces during biting behaviors used for roost excavation. We found no difference in canine tooth wear between the sexes, but tooth wear was significantly higher in an ecologically similar species that does not excavate roosts. We conclude that the behavior, performance, and possibly morphology of L. silvicolum represent adaptations to roost excavation.

The coexistence of multiple species of short-tailed fruit bats (Phyllostomidae: Carollia) is common throughout the range of the genus. Previous studies of fecal and stomach contents have documented differences in dietary breadth and in habitat use as mechanisms by which these species may partition dietary niches. By comparing values of δ¹⁵N and δ¹³C across species of Carollia from 17 sites in Central and South America, we show that co-occurring Carollia frequently differ in dietary breadth, foraging habitats, and level of insectivory. Values of δ¹⁵N, which tended to be enriched in C. castanea, depleted in C. perspicillata, and intermediate in C. brevicauda and C. sowelli, indicate trophic stratification. Values of δ¹³C followed the opposite trend, tending to be enriched in C. perspicillata and depleted in C. castanea, suggesting interspecific differences in breadth of the foraging area. Isotopic comparisons among Carollia, other bat species, and potential food items at 5 of our sites illustrate that populations of Carollia tend to be trophically intermediate between strictly phytophagous and strictly insectivorous organisms, and, contrary to the paucity of insect remains found in fecal samples, indicate that the consumption of insects by Carollia is more common and potentially more important than previously was thought.

Flexible behaviors permit gregarious animals to exploit spatially and temporally favorable conditions for reproduction. Evening emergences of Brazilian free-tailed bats (Tadarida brasiliensis) in south-central Texas were recorded to determine changes in colony dynamics and to evaluate hypotheses associated with predator avoidance and seasonal energy demands. In 2007, median parturition date was 18 June and lactation lasted about 54 days. Juveniles commenced flight after 41 days, then continued to suckle for 2 weeks before being weaned. Onset of evening emergence was correlated with sunset, beginning, on average, 11.8 min after sunset (95% confidence interval  =  7.1, 16.6), which is later than reported in previous studies. Pregnant females emerged later than their roost mates, consistent with a predator avoidance hypothesis. Lactating females emerged after sunset, but earlier than other bats, consistent with the hypothesis that this is a period of high energy demand. Juveniles emerged later than adult females while they continued to be suckled, but emerged earlier as they matured and were weaned, suggesting a trade-off between predator avoidance and energy demands. Our observations indicate that evening emergence behavior of T. brasiliensis varies with environmental cues but is mediated by the energetic demands of reproduction.

The subgenus Artibeus includes 8 species of frugivorous bats of widespread neotropical distribution. The only fossil species, Artibeus anthonyi, was described from deposits of the Cuban Quaternary, and its taxonomic status has been debated in the literature. Based on exceptionally well-preserved new fossil material, an emended diagnosis and a detailed description of the cranium of A. anthonyi are presented. In addition, we used multivariate analyses to explore the morphometric differentiation between A. anthonyi and the extant species of the subgenus Artibeus. A. anthonyi shows the greatest morphological divergence compared with extant Artibeus species.