Gary McCracken, Ph.D. - US grants

This award will support the purchase of reach-in and walk-in environmental chambers that permit programmed control of climatic conditions and of associated monitoring equipment. The units will be shared by five researchers and their students and postdocs. Some of the units will be used for rearing various animal taxa (e.g., cooperative spiders from African tropical rain forests that require moderate temperatures and high humidities, or Mexican free-tailed bats whose nursing-colony maintenance requires temperatures of 120F). Other chambers will be used in experiments (e.g., simulated releases of biologically engineered bacteria in a quasi-natural system, or territory size estimates for genetic studies of the behavior of desert animal species). All of these projects require varying conditions of lighting, temperature and humidity. Additionally, some of the projects require the presentation of stimuli (e.g., odors) under conditions isolated from extraneous stimuli. The equipment to be funded permits the achievement of these necessary conditions.

Students apply a broad range of molecular, cytological and classical genetic techniques to problems at the gene, chromosome, organism, and population levels. The organizing theme is analysis of the Adh locus in Drosophila. Experiments include a molecular analysis of Adh variants, recombination and cytological mapping of the Adh locus, analysis of polytene chromosomes exhibiting Adh-region rearrangements, histological analysis of the tissue, and an exploration of the genetic basis of the response to selection for alcohol tolerance in a large population. The equipment for this laboratory includes electrophoresis systems, centrifuges, and specialized microscopes. The unique feature of this project is the use of a variety of techniques to study one system at a number of levels; from population statistics based on behavior to analysis of DNA sequences. This multilevel approach conveys to the students the true nature of research within the discipline.

How do animals adapt to changes in their environments? Are all healthy, normal appearing individuals or their offspring equally able to survive? Since finding and utilizing food resources are important aspects of survival and the occupation of new or altered habitats, this proposal aims at the study of foraging and food use in a species with a generalized diet that is known to exploit novel prey. This species is the common garter snake, Thamnophis sirtalis, which can feed on a variety of small animals. This investigator will follow babies from birth through the first months of life in a study that will look at the effects of genetic background, diet, and ontogeny on food choice, foraging ability, and growth. The initial responses to prey involve chemical cues in newborn common garter snakes. There is great variability among individuals, even from the same litter. Experience with different prey types can alter prey recognition, prey preference, and prey capturing ability. This project will investigate this individuality and plasticity with snakes from different litters born to mothers from the same natural area. Since one advantage of snakes is the large number of animals born to each mother, snakes from each litter will be put in various groups raised on controlled or free-choice diets. Another advantage of this species is that different babies born to a given female may have different fathers. Thus identifying which snakes in a litter have the same or different fathers can help separate genetic factors from prenatal environmental ones. Newly developed microsatellite DNA techniques will be applied in identifying animals with the same or different fathers. It is hoped that the results of this work will help in predicting which aspects of foraging are most important to survival when animals confront different or changed environments, and how environments and genetic differences interact.

Intellectual Merit of the Proposed Activity
Millions of Brazilian free-tailed bats (Tadarida brasiliensis) voraciously consume enormous quantities of insects each summer night throughout the southwestern United States. These bats provide an agricultural pest control service little understood by the scientific community and policy makers. The proposed effort will evaluate the nationwide ecological and economic impact of this species on both natural and agricultural ecosystems. The project is innovative in its development of information technology and unique in its complexity and scale. It requires the collaborative efforts of computer scientists, applied mathematicians, meteorologists, ecologists, and ecological economists. Proposed activities involve:
1. Sensing Technologies.-Design, develop, deploy, and evaluate algorithms and systems for thermal, ultrasonic, and radar sensing of millions of bats and insect pests. Such algorithms and systems currently do not exist but are crucial for providing a reliable census of the nationwide free-tailed bat populations and processes. Computer vision techniques will be developed to analyze nightly emergence, flight paths, and foraging behaviors of individuals and groups of bats.
2. Computational Modeling.-Design, develop, solve, and validate computational models of the agricultural-insects-bats system across temporal and spatial scales. Processes at lower levels of organization, such as the individual bat and its physiological functions, will be analyzed to solve problems posed at higher ecological levels of organization from the population to the landscape. Local population models for particular caves or bridges will be generalized to a spatially explicit regional model for Texas, and then to a spatially explicit landscape model that describes the nationwide impact of Brazilian free-tailed bats on agricultural ecosystems. Currently, no complete individual or population life-history models exist for free-tailed bats nor, indeed, for any bat species, in spite of the fact bats are ubiquitous throughout the world and are distinguished as the second largest order of mammals.
3. System Integration.-The proposed models will be integrated using both conceptual and spatial hierarchies. Results provided by the sensing technologies will be combined to represent the processes of foraging and migration. The integration of these outcomes as well as molecular tools (such as fecal DNA), entomological and agricultural information, energetics, meteorological and toxicological databases, will provide input parameters and validation data to computational models of bat populations. The models will integrate the interdependencies of dietary factors, energy consumption and allocation, weather patterns, effects of toxicants, etc. on birth and mortality rates and population sizes of bats and their prey.

Broader Impacts Resulting from the Proposed Activity
The importance of natural pest-control services becomes evident often only when they are degraded or eliminated by human activity. The proposed research will provide realistic estimates of the economic impact of Brazilian free-tailed bats. The proposed techniques may generalize to other species and thus have a broad impact in the fields of biology, ecology, ecological economics, and agriculture. The proposed methods of image analysis may apply to other large-scale video tracking applications, for instance, the analysis of group behavior of other bat species, insects, herding mammals (e.g., seals, caribou), colonial seabirds, the analysis of human crowd behavior, data mining of video of human motion, and video surveillance for homeland security. An important impact of the proposed research on society will be the development appropriate policy responses by federal, state, or local authorities based on the fundamentally improved understanding of the underlying biological and economic principles of natural pest control. The proposed effort addresses the goals of the ITR Program in a number of ways. It is multidisciplinary in nature, providing a new bridge between the fields of computational sciences and ecology. This may lead to novel, unanticipated insights and technologies in both fields. The proposed effort will train students in biology and computer science to fully integrate information technology and science. Graduate and undergraduate students from both disciplines will learn to conduct joint field experiments, analyze data, and work with computational models. The projects in computer science that are inspired by questions in biology promise to have a special appeal to women, and we expect that our project will encourage more women to explore the computational aspects of biology.

This project investigates the effects of man's alteration of environments on rabies infections in bats. The research involves the following interrelated components: 1) studies of the population ecology and genetics of two common species of bats in natural and in man-altered habitats; 2) surveillance for rabies exposure and infection in these wild populations; 3) investigation of the effects of immune system stress resulting from habitat change on the ability of bats to resist disease infection; 4) laboratory experiments to connect the effects of stress on the immune system of bats and their susceptibility to rabies under controlled conditions; 5) mathematical modeling to integrate the data from the field studies and laboratory experiments to achieve a predictive analysis of how habitat change and stress affect disease dynamics within wild populations of bats.

Within the last 40 years, bats have become the primary reservoir for human rabies infections in the U.S. These same years have witnessed the emergence of numerous infectious diseases (e.g., AIDS, Ebola, West Nile Virus, hantaviruses) that are major threats to human health. Man's alteration of environments and changes in the relationships between the diseases and the animals they infect are implicated in the emergence of each of these diseases. Beyond providing a better understanding of rabies, this study will address issues common to the ecology of many diseases that infect wildlife and man.

White-Nose Syndrome is a fungal disease that affects bats hibernating in caves. Since it was first identified in the eastern United States in 2006, the disease has spread from cave to cave across the Northeast, as far south as Tennessee, and as far west as Oklahoma and Ontario. Over a million bats have died from the fungus, called Geomyces destructans or Gd by scientists, which flourishes in the cool conditions of caves. The goal of this research project is to gain a better understanding how the disease is transmitted at local, regional, and continental scales.

The researchers will focus in particular on bat social behavior, such as the size of congregating groups and assortment within groups, which are known to vary both within and between bat species during different seasons. They hypothesize that disease transmission from bat to bat and cave to cave is affected by temporal and spatial variation in how bat social groups are organized. They will collect data to see if transmission increases with colony size and with how often and for how long bats are aroused during hibernation; if cave temperature and humidity affect the growth of the fungus; if the number of different bat species present in a region influences the prevalence of the disease; if some species are more susceptible than others; and if geographic latitude and having more places to hibernate in a given area promotes the development and spread of White-Nose Syndrome in local bat populations.

The researchers will use these data to create a predictive behavior-based model of disease transmission. Bats are significant in North American ecology because they control insects and pollinate plants. Understanding how this devastating disease develops and spreads is critical to protecting bat populations and the ecosystem services they provide. The researchers, who come from multiple disciplines and several universities (Boston University, the University of California-Santa Cruz, Northern Arizona University, and the University of Tennessee), also will train graduate and undergraduate students in the conduct of the research. They will share their results with resource managers and policy makers at state and federal levels, and will participate in Congressional briefings and in the United States Fish and Wildlife Service's White-Nose Syndrome National Plan.

Project Abstract

The acoustic communication and echolocation of bats are among the most sophisticated and technically impressive sensory capabilities in the animal world. The study of bats is important to gain insight into these capabilities as well as to understand the roles of bats as predators of agricultural pests and vectors of infectious disease. Specifically, analysis of the acoustic signals used by bats for foraging and communication is necessary to understand their community structure, hunting patterns, and the signal processing underlying their capabilities. However, efforts to study bat calls in natural settings have been limited by the constraints imposed by ground-based recording equipment. Because of their small body sizes most bats are incapable of carrying existing ultrasonic recording instruments. Therefore, all studies to date have been conducted either in artificial laboratory conditions with fixed recording equipment, or in the wild with ground-based, typically stationary, recording equipment. Both methods have a variety of serious shortcomings. Ultrasound signals are context-specific and vary rapidly and over short distances, so a fixed recording device will not capture the same signals observed by a bat. Laboratory conditions cannot mimic the complex natural environment. With the use of ground-based recordings it usually is not possible to separate the calls made by individual bats. The echoes reflected from targeted insects often are too faint to be detected by ground-based recording equipment. As a result, the information obtainable by ground-based equipment is necessarily incomplete. With recent advances in electronics technology, a wide variety of miniaturized sensors have become possible. This project will include the development of miniaturized ultrasonic recording devices to be mounted on bats for recording calls and echoes during flight. The final design will utilize a custom integrated circuit (IC) to achieve a total system weight under 1 g.

This project will result in an acoustic monitoring device unlike any existing instrument. By reducing the distance between the bat and the transducer from a few 10's of meters to a few centimeters, the instrumentation developed in this project will realize an improvement in signal quality of several orders of magnitude compared to existing ground-based recording techniques. Furthermore, recordings of more distant bats that are currently infeasible due to signal attenuation will be made practical with the proposed instrument. A bat-mounted recorder will also enable separation of signals from individual bats and the ability to follow an individual bat over a significant distance. Additionally, the proposed research will advance the design of ultra-low-power wireless instrumentation and integrated circuit design.
This project offers the potential to introduce a breakthrough in methods for bat research. The knowledge gained through the use of the proposed instrument will provide important insights into communication among bats that are relevant to the role of bats as predators of agricultural pests and to public health concerns regarding bats' role as disease vectors. It will also contribute to the understanding of bats' ultrasonic sensing capacities. The instrumentation developed in this project will also be useful for a wide variety of other scientific investigations, such as the study of song learning in songbirds or language acquisition in human infants. The interdisciplinary nature of the project will provide an opportunity for graduate and undergraduate students to work at the intersection of biology and electronics. The integration of the proposed circuits into a complete recording system will provide valuable practical experience in working with complex electronic systems-on-chip.