Rick A. Adams

Water availability and successful lactation by bats as related to climate change in arid regions of western North America

1. Climate change in North America is happening at an accelerated rate, reducing availability of water resources for bats and other wildlife that require it for successful reproduction. 2. We test the water-needy lactation hypotheses directly by tracking the drinking habitats of individual lactating and non-reproductive female fringed myotis at an artificial water source located near a maternity roost. 3. We used a submerged passive integrative transponder (PIT) tag reader system designed to track fish to instead record numbers of water source visitations by tagged bats. 4. Of 24 PIT-tagged adult females, 16 (67%) were detected repeatedly by the plate antenna as they passed to drink between 18 July and 28 August 2006. 5. The total number of drinking passes by lactating females (n = 255) were significantly higher than those of non-reproductive adult females (n = 22). Overall, lactating females visited 13 times more often to drink water than did non-reproductive females. On average, lactating females visited six times more often per night. Drinking bouts occurred most frequently just after evening emergence and at dawn. 6. Drinking patterns of non-reproductive females correlated significantly with fluctuating ambient temperature and relative humidity recorded at the water source, whereas lactating females drank extensively regardless of ambient conditions. 7. We provide a mathematical model to predict the rate of decline in bat populations in the arid West in relation to climate change models for the region.

Bat reproduction declines when conditions mimic climate change projections for western North America.

Climate change models predict that much of western North America is becoming significantly warmer and drier, resulting in overall reductions in availability of water for ecosystems. Herein, I demonstrate that significant declines in the reproductive success of female insectivorous bats occur in years when annual environmental conditions mimic the long-term predictions of regional climate change models. Using a data set gathered on bat populations from 1996 through 2008 along the Front Range of Colorado, I compare trends in population numbers and reproductive outcomes of six species of vespertilionid bats with data on mean annual high temperature, precipitation, snow pack, and stream discharge rates. I show that levels of precipitation and flow rates of small streams near maternity colonies is fundamentally tied to successful reproduction in female bats, particularly during the lactation phase. Across years that experienced greater than average mean temperatures with less than average precipitation and stream flow, bat populations responded by slight to profound reductions in reproductive output depending on the severity of drought conditions. In particular, reproductive outputs showed profound declines (32-51%) when discharge rates of the largest stream in the field area dropped below 7 m3/s, indicating a threshold response. Such sensitivity to environmental change portends severe impacts to regional bat populations if current scenarios for climate change in western North America are accurate. In addition, bats act as early-warning indicators of large-scale ecological effects resulting from further regional warming and drying trends currently at play in western North America.

Transcriptome Sequencing and Annotation for the Jamaican Fruit Bat (Artibeus jamaicensis)

The Jamaican fruit bat (Artibeus jamaicensis) is one of the most common bats in the tropical Americas. It is thought to be a potential reservoir host of Tacaribe virus, an arenavirus closely related to the South American hemorrhagic fever viruses. We performed transcriptome sequencing and annotation from lung, kidney and spleen tissues using 454 and Illumina platforms to develop this species as an animal model. More than 100,000 contigs were assembled, with 25,000 genes that were functionally annotated. Of the remaining unannotated contigs, 80% were found within bat genomes or transcriptomes. Annotated genes are involved in a broad range of activities ranging from cellular metabolism to genome regulation through ncRNAs. Reciprocal BLAST best hits yielded 8,785 sequences that are orthologous to mouse, rat, cattle, horse and human. Species tree analysis of sequences from 2,378 loci was used to achieve 95% bootstrap support for the placement of bat as sister to the clade containing horse, dog, and cattle. Through substitution rate estimation between bat and human, 32 genes were identified with evidence for positive selection. We also identified 466 immune-related genes, which may be useful for studying Tacaribe virus infection of this species. The Jamaican fruit bat transcriptome dataset is a resource that should provide additional candidate markers for studying bat evolution and ecology, and tools for analysis of the host response and pathology of disease.

Calcium as a limiting resource to insectivorous bats: can water holes provide a supplemental mineral source?

Data are presented on a bat assemblage captured among 10 water holes in Colorado over 5 years. The assemblage consists of Myotis ciliolabrum, M. evotis, M. lucifugus, M. thysanodes, M. volans, Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans and Corynorhinus townsendii .R esults show that reproductive females and juveniles are captured in higher frequencies at water holes containing higher water hardness and that water hardness correlates highly significantly with dissolved calcium content. Also presented are laboratory test data on the stomach volume of Eptesicus fuscus that provide a model for understanding the effect of dissolved calcium content in water as a significant resource. These data indicate that water holes provide supplemental sources of calcium for bats not provided by diet.

Tacaribe Virus Causes Fatal Infection of An Ostensible Reservoir Host, the Jamaican Fruit Bat

ABSTRACT Tacaribe virus (TCRV) was first isolated from 11 Artibeus species bats captured in Trinidad in the 1950s during a rabies virus surveillance program. Despite significant effort, no evidence of infection of other mammals, mostly rodents, was found, suggesting that no other vertebrates harbored TCRV. For this reason, it was hypothesized that TCRV was naturally hosted by artibeus bats. This is in stark contrast to other arenaviruses with known hosts, all of which are rodents. To examine this hypothesis, we conducted experimental infections of Jamaican fruit bats (Artibeus jamaicensis) to determine whether they could be persistently infected without substantial pathology. We subcutaneously or intranasally infected bats with TCRV strain TRVL-11573, the only remaining strain of TCRV, and found that low-dose (104 50% tissue culture infective dose [TCID50]) inoculations resulted in asymptomatic and apathogenic infection and virus clearance, while high-dose (106 TCID50) inoculations caused substantial morbidity and mortality as early as 10 days postinfection. Uninoculated cage mates failed to seroconvert, and viral RNA was not detected in their tissues, suggesting that transmission did not occur. Together, these data suggest that A. jamaicensis bats may not be a reservoir host for TCRV.

Morphogenesis in Bat Wings: Linking Development, Evolution and Ecology

The evolution of powered flight in mammals required specific developmental shifts from an ancestral limb morphology to one adapted for flight. Through studies of comparative morphogenesis, investigators have quantified points and rates of divergence providing important insights into how wings evolved in mammals. Herein I compare growth, development and skeletogenesis of forelimbs between bats and the more ancestral state provided by the rat (Rattus norvegicus) and quantify growth trajectories that illustrate morphological divergence both developmentally and evolutionarily. In addition, I discuss how wing shape is controlled during morphogenesis by applying multivariate analyses of wing bones and wing membranes and discuss how flight dynamics are stabilized during flight ontogeny. Further, I discuss the development of flight in bats in relation to the ontogenetic niche and how juveniles effect populational foraging patterns. In addition, I provide a hypothetical ontogenetic landscape model that predicts how and when selection is most intense during juvenile morphogenesis and test this model with data from a population of the little brown bat, Myotis lucifugus.

Bats and Water: Anthropogenic Alterations Threaten Global Bat Populations

Natural bodies of open water in desert landscapes, such as springs and ephemeral pools, and the plant-life they support, are important resources for the survival of animals in hyper arid, arid and semi-arid (dryland) environments. Human-made artificial water sources, i.e. waste-water treatment ponds, catchments and reservoirs, have become equally important for wildlife in those areas. Bodies of open water are used by bats either for drinking and/or as sites over which to forage for aquatic emergent insects. Due to the scarcity of available water for replenishing water losses during roosting and flight, open bodies of water of many shapes and sizes may well be a key resource influencing the survival, activity, resource use and the distribution of insectivorous bats. In this chapter, we review the current knowledge of bats living in semi- and arid regions around the world and discuss the factors that influence their richness, behaviour and activity around bodies of water. We further present how increased anthropogenic changes in hydrology and water availability may influence the distribution of species of bats in desert environments and offer directions for future research on basic and applied aspects on bats and the water they use in these environments.

Bat Evolution, Ecology, and Conservation

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Flapping Tail Membrane in Bats Produces Potentially Important Thrust during Horizontal Takeoffs and Very Slow Flight

Historically, studies concerning bat flight have focused primarily on the wings. By analyzing high-speed video taken on 48 individuals of five species of vespertilionid bats, we show that the capacity to flap the tail-membrane (uropatagium) in order to generate thrust and lift during takeoffs and minimal-speed flight (<1 m s−1) was largely underestimated. Indeed, bats flapped the tail-membrane by extensive dorso-ventral fanning motions covering as much as 135 degrees of arc consistent with thrust generation by air displacement. The degree of dorsal extension of the tail-membrane, and thus the potential amount of thrust generated during platform launches, was significantly correlated with body mass (P = 0.02). Adduction of the hind limbs during upstrokes collapsed the tail-membrane thereby reducing its surface area and minimizing negative lift forces. Abduction of the hind limbs during the downstroke fully expanded the tail-membrane as it was swept ventrally. The flapping kinematics of the tail-membrane is thus consistent with expectations for an airfoil. Timing offsets between the wings and tail-membrane during downstrokes was as much as 50%, suggesting that the tail-membrane was providing thrust and perhaps lift when the wings were retracting through the upstoke phase of the wing-beat cycle. The extent to which the tail-membrane was used during takeoffs differed significantly among four vespertilionid species (P = 0.01) and aligned with predictions derived from bat ecomorphology. The extensive fanning motion of the tail membrane by vespertilionid bats has not been reported for other flying vertebrates.

Prenatal Growth and Development in the Angolan Free-Tailed Bat, Mops condylurus (Chiroptera: Molossidae)

Abstract We present data on prenatal growth, development, and skeletal ossification for the Angolan free-tailed bat (Mops condylurus), a species distributed throughout sub-Saharan Africa. Specimens were measured for crown–rump length (CRL), greatest length of the skull (GLS), forearm length, mass, and wing area. We cleared and differentially stained specimens for cartilage and bone to quantify pattern of skeletogenesis. Significant regressions for general growth trajectories were generated by plotting CRL and fetal mass against GLS. We quantified growth of the forearm, which showed a positive relationship with growth of the skull. Curiously, wing area was highly positively related to fetal mass, suggesting an ecomorphological relationship of wing loading and flight ability being established early in development in this species. Patterns of ossification in this species were more similar to those of phyllostomid and pteropodid bats than they were to vespertilionid bats, to which M. condylurus is apparently more closely related.