Archives -- Research Reports

Effects of Top Predators (Trout) on the Mean Levels, Overall Variability, and Spatial Heterogeneity of Lower Trophic Levels (Invertebrates, Algae in Streams)-- Scott D. Cooper, Marine Science Institute and Department of Biological Sciences, UCSB

K. Kratz, S. Diehl, S. Wiseman, T. Jenkins, S. Roll, M. Dixon, R. Burneo, E.-M. Diehl, E. Gayler, M. Strunk, S. Stark, N. Barbee, T. Even, B. Perez: Department of Biological Sciences, UCSB

During the summer of 1994, my research group and I conducted experiments in the experimental stream facilities at SNARL. This research examined the effects of top predators (trout) on the mean levels, overall variability, and spatial heterogeneity of lower trophic levels (stream invertebrates, algae). We set up a gradient of densities of young-of-the-year brown trout in the 50 m2 stream channels at SNARL, and also reduced trout densities in two of the large (1100 m2) stream sections, leaving trout density in the other two stream sections at natural levels. We examined the responses of benthic invertebrates, invertebrate drift, algae, and detritus, as well as trout growth, survival, emigration, and diets, to manipulated densities of trout. We also examined the effects of trout manipulations on the spatial arrangement of patches of grazing invertebrates and algae using geostatistical techniques. We found that trout had strong effects on the local distribution of grazing insects and the biomass of algae; however, trout appeared to have few effects on the spatial heterogeneity of invertebrates and algae. Trout ate primarily mayflies at low trout densities and chironomids at high trout densities, and trout growth was a negative, exponential function of trout density. Trout density had no effects on trout survivorship or per capita emigration rates. We also ran a series of small-scale experiments examining responses of different types of grazers (mobile vs. slow-moving) to different scales of patchiness in their algal resources. Field personnel included the principal investigator, field and laboratory supervisors, and three full-time student assistants. We obtained additional help from seven part-time assistants during three periods of intensive sampling. Funding: NSF

Livestock Grazing and Rangeland Stream Ecology --David B. Herbst and Roland A. Knapp, Marine Science Institute, UCSB M. Embury, P. Kirchner, D. R. Dawson: SNARL

Livestock grazing in the limited riparian zone of arid Great Basin streams often results in a loss of vegetative cover and the degradation and erosion of stream channel habitats. Although changes in the riparian and physical environment of streams are well-documented, much less is known about the responses of in-stream aquatic communities to grazing-related impacts. For 3 years we have been using biological monitoring of stream reaches exposed to varied grazing practices to both evaluate differences in the ecological attributes of grazed and ungrazed areas, and the success of management in alleviating nonpoint source pollution problems. A loss of invertebrate species diversity and shifts in indicator groups consistently occurred at some grazed sites while others were unchanged relative to reference sites. Trout abundance also was decreased at some grazed sites but not others. Results suggest that riparian monitoring alone is insufficient to detect changes in aquatic ecosystem structure and function, and that bioassessment monitoring is sensitive and responsive to local and seasonal changes in rangeland stream environments. Funding: UC Water Resources Center.

Mono Lake Benthic Ecology and Environmental Physiology --David B. Herbst, Marine Science Institute, UCSB

C. Culbertson and L. Miller: USGS, Menlo Park
D. Blinn and J. Naquin: Northern Arizona University
R. Castenholz: University of Oregon

Continued research at Mono Lake has included monitoring of the abundance of the alkali fly population, the primary food source for many shorebirds visiting this saline lake. Changes related to varied lake levels will provide feedback to lake management planning. Research also included studies of the rate of colonization of artificial substrates by algae and fly larvae and pupae (as a monitoring tool and in relation to small-scale surface orientation). In addition, salinity effects on the microbial community of Mono Lake were investigated in (1) the growth response of the filamentous green alga Ctenocladus, and (2) the rate of nitrogen fixation in the microbial community of shallow sediments. All results played a role in the recent decision of the State Water Resources Control Board to raise the level of Mono Lake and to restore the ecosystem. Funding: Mono Lake Foundation.  

Biogeography of Great Basin Aquatic Invertebrates --David B. Herbst, Marine Science Institute, UCSB

with the University of Nevada Biodiversity Center at Reno, Nevada

Aquatic habitats throughout much of the Great Basin are isolated islands in a sea of desert. On the Sheldon Wildlife Refuge in northern Nevada are a variety of habitats including ephemeral lakes, spring systems, and perennial streams that flow for a few miles then disappear into desert sand. Few collections of aquatic invertebrates have been made from this region and there is great potential for the discovery of relict, isolated and endemic species and extensions in the ranges of known organisms. Exploration and collections on this half-million acre refuge will contribute to documenting the biodiversity of the Great Basin and prioritizing refuge habitats for protection. Funding: E. L. Wiegand Foundation.

Project 1: Impacts of Livestock Grazing on the Habitat and Population Structure of Golden Trout
Project 2: Impacts of Non-native Trout on Lake Ecosystems in the Sierra Nevada
--Roland A. Knapp, Marine Science Institute, UCSB

K. Matthews, V. Vredenburg, J. Muck, D. Paron: USDA Pacific Southwest Research Station
R. Jellison, T. Jenkins, P. Kirchner, M. Embury, E. Wenk: Marine Science Institute, UCSB

Project I: The first of these projects is aimed at understanding the impacts of livestock grazing on the habitat and population structure of golden trout in their native streams (Golden Trout Wilderness, Inyo National Forest, California). The native streams of the golden trout are generally heavily degraded by cattle grazing, and trout populations in these streams are characterized by extremely dense and slow-growing fish, but little is known about what regulates these populations. Our results to date show that golden trout have very specific spawning habitat requirements, only utilizing particular water depths, water velocities, and substrate sizes for nest construction and egg deposition. In addition, preferred spawning habitat features are much more common in heavily-grazed areas than lightly-grazed or ungrazed areas, because cattle grazing decreases bank stability and results in wider, shallower streams. As a result of increased spawning habitat availability, nest density and density of juvenile trout is also much higher in heavily grazed than in lightly-grazed or ungrazed areas. These results suggest that by increasing the amount of spawning habitat available to golden trout, livestock grazing may have indirectly resulted in increased densities and slower growth rates of golden trout in their native streams. Our results have important consequences for grazing management and stream restoration strategies in the Golden Trout Wilderness and other meadow-stream ecosystems in the western United States. Project 2: The second research project is designed to elucidate the impacts of non-native trout on lake ecosystems in the Sierra Nevada. Historically, nearly all Sierran lakes were fishless. Starting in the 1850's and continuing to the present day, however, trout have been stocked into nearly all suitable waters. Because trout are effective predators, these introductions have resulted in precipitous declines in species adapted to fishless lakes, including amphibians, and some zooplankton and benthic invertebrates. In some cases (e.g., amphibians), these declines have been severe enough that some species may soon be listed under the Endangered Species Act. In order to better understand the impacts of introduced trout on lake ecosystems, we are sampling all lakes in several watersheds in the Sierra Nevada for fish, amphibians, zooplankton, and benthic invertebrates. The information generated by this sampling effort will be used to model the population viability of the mountain yellow-legged frog, and the distribution of trout that would result from several alternative trout stocking practices. Our study will increase our understanding of causes underlying amphibian declines, and will have important consequences for the future management of high mountain lake ecosystems. Funding: USDA Pacific Southwest Research Station.

Vertical Mixing and Resource Supply to Phytoplankton
--Sally MacIntyre, Marine Science Institute, UCSB

R. S. Jellison, K. M. Flynn, J. R. Romero, D. Heil, C. Saltikov: Marine Science Institute, UCSB

My research project addresses the importance of vertical mixing to phytoplankton ecology. I use turbulent microstructure profilers to determine where the water column is mixing and the intensity of the turbulence. With accompanying profiles of chlorophyll a and nutrients, we will assess the vertical circulation of phytoplankton and their exposure to fluctuating irradiance as well as rates of nutrient flux. By performing measurements in different parts of lake basins, we will determine whether nutrient fluxes are forced by Kelvin-Helmholtz billowing in the thermocline or by other processes such as boundary mixing or upwelling. Measurements were made in Lake Biwa, Japan, in 1993, as part of the Lake Biwa Transport Experiment (BITEX), the first international, interdisciplinary limnological study on the scale of an oceanographic experiment. Field studies were conducted at Mono Lake, CA during spring, summer, and fall of 1995 and included periods of calm as well as stormy periods with winds gusting to 20 m/s. Funding: National Science Foundation.

Mono Lake Research --John M. Melack, Marine Science Institute and Department of Biological Sciences, UCSB

M. Gastil, D. Heil, R. Jellison, M. Embry, M. Moskowitz: Marine Science Institute, UCSB

Mono Lake is a large, hypersaline, highly productive alkaline lake lying just east of the Sierra Nevada. In, addition to its value as a recreational and scenic resource, it contains large populations of an endemic brine shrimp and the alkali fly which are an important food source for migrating birds. Although saline lakes are common throughout the world and provide important ecological resources for many species, they are much less studied than freshwater ecosystems. Limnological monitoring programs and experimental research conducted from 1982-1994 represent one of the longest continuous studies of any hypersaline ecosystem and, in addition to addressing current environmental concerns in the Mono Basin, provide insight into the functioning of saline ecosystems. Funding: Los Angeles Department of Water and Power and NASA (HIRIS).

Aquatic Insects in the Springs of the Great Basin --Marilyn Myers, Department of Environmental Science, Policy and Management, UC Berkeley

In the 1994 field season I visited 52 springs to do preliminary collecting of aquatic insects. Some of the springs were dry, but for those that had water, I took water temperature, estimated discharge, and made qualitative collections of aquatic insects. I kept detailed field notes on each spring, i.e., size of the riparian area, dominant vegetation, impacts from grazing or recreation, substrate type, etc., and took photographs of the site. In the winter, I identified most aquatic insects to the generic level. From this preliminary work, I selected five springs to use in a population study of Hesperophylax designatus in 1995. I also decided to begin a life history study of Pedomecus sierra, a poorly known caddisfly that lives in some of the springbrooks in the Glass Mountains. Funding: UC Berkeley departmental funds.

Snow Algae Studies at SNARL--William H. Thomas, Scripps Institution of Oceanography, UC San Diego

T. Thomas, A. M. Thomas, and A. K. Thomas: MRD/SIO/UC San Diego
B. Duval: University of Massachusetts

Microscopic algae, that color old snowfields red or green, were abundant in early summer of 1993 and 1994 in the Tioga Pass area of the Sierra Nevada. We postulated that surface algal blooms would decrease albedo, the proportion of sunlight reflected back from the snow, and thus snow melting would be increased. Significant negative correlations were found between albedo and algal cell numbers in the snow, but albedo was not decreased over the whole Tioga Pass watershed because the algae occurred in discrete patches. Thus water supply was not affected by algae. Dirt on the snow also decreased albedo. Snow bacterial abundances and growth rates were higher in red snow containing algae than in white snow. Bacterial growth rates were also less than algal photosynthetic rates. Thus bacteria seemed to be dependent on algae for much of their nutrient supply and were ultimately associated with algae, often attached to algal cells. About 30% more ultraviolet radiation is found at the elevation of Tioga Pass than at sea level and the Sierra is a high-UV environment. In experiments where snow algae were contained in UV-transmitting quartz tubes, UV radiation inhibited red snow (collected from open, sunlit areas) photosynthesis about 25%, whereas green snow (collected from forested, shady locations) photosynthesis was inhibited by 85%. These differences may be due to different habitats, or may be genetic, since different species were found in the two snow types. These studies are some of the first to examine the microbial ecology of snow, and we plan to assess the effects of UV on the complete algal-bacterial ecosystem in future field studies at Tioga Pass and at SNARL. Funding: Donation to SIO and Southern California Edison Company.

back to top

Geography/Geology

Cold Regions Research and Engineering Laboratory-- Robert E. Davis, Department of the Army, Hanover, NH
J. Dozier's research group: ICESS, UCSB
S. Burak: Snow Survey Associates

The broad goal of this research is to advance the understanding of the spatial distributions of snow properties and processes in complex landscapes. Use of the Reserve toward this goal involved carrying out field and laboratory experiments to measure changes in snow properties, testing models to predict the changes in snow properties over time, and developing links between these models and remote sensing measurements. Investigations toward this goal were carried out at a variety of spatial scales. In laboratory experiments we melted snow to examine how initial conditions and melt schemes affected the intensity and timing of the ionic pulse of trace chemical species. Near the other end of the scale range we related weather conditions over a large area to the release of avalanches by explosive triggering. Results of these efforts were published. Additional publications on the avalanche data are currently in preparation. At intermediate spatial scales, we are continuing research to develop links between remotely sensed products, such as snow extent maps, and spatially distributed snow process modeling. Most of this work used Mammoth Mountain as the test area for intensive studies, and the Black Cap watershed in the Kings River basin as the test area for broad hydrologic studies. Funding: Primarily by Army Corps of Engineers Projects 2A762784AT42 and Civil Works Remote Sensing (363) Work Unit 32712.

Snowmelt research at the Sierra Nevada Aquatic Research Laboratory-- Bob Harrington, Hydrology and Water Resources, University of Arizona

Monitoring of snowmelt runoff and chemistry was conducted at the Sierra Nevada Aquatic Research Laboratory's snowmelt research site on Mammoth Mountain. Principal investigators Roger Bales of the University of Arizona and Jeff Dozier of UCSB examined the process governing release of pollutants stored in the snowpack, and determined the spatial variability of snowpack properties and snowmelt runoff. The extremely deep (5.2 meters) snowpack during the winter of 1994-1995 provided an excellent set of data for looking at hydrologic processes that take place under heavy snow conditions. Dr. Rick Kattelmann and Bob Harrington observed slightly elevated concentrations of ionic solute at the onset of spring melt, followed by extremely dilute flow from the melting snowpack. Funding: NSF and the NASA Earth Observing System Interdisciplinary Science Investigations Program .

Water Studies in the Sierra Nevada-- Rick Kattelmann, ICESS, UCSB

Initial wetting of dry snow cover controls the timing of water release to soils and streams. Field studies in the Sierra Nevada examined the transition from dry to wet snow, both seasonally in the alpine zone and during short periods of rainfall in the forest zone. Snowpack properties were monitored on a near-daily basis at several sites to examine the progressive wetting of an alpine snow cover over a period of a few weeks. During initial introduction of liquid water into the high-elevation snow cover, water had a highly irregular distribution with no signs of a uniform wetting front. Convergence of near-surface flow in shallow depressions on level snow surfaces allowed water to reach the base of the snowpack in isolated spots as much as a month in advance of wetting throughout the snowpack. This convergence produced local fluxes of water ten to a hundred times greater than the surface melt rate. Flow along strata within sloping snowpacks allowed water to bypass lower layers of the snow cover during the first few days of surface melt. More than 40 rain-on-snow events with adequate records of rainfall and outflow timing illustrated the short-term response of deep snowpacks to rainfall. The observed snowpacks stored little water before the first outflow and imposed only a few hours of delay on its time of release. Large amounts of fresh snow did not impede water percolation resulting from rainfall. Funding: NASA's Earth Observing System Program (Jeff Dozier, ICESS).

Acid Rain Research-- John M. Melack, Marine Science Institute and Department of Biological Sciences, UCSB

D. R. Dawson: SNARL Reserve Manager
J. Sickman, K. Skeen, G. Spindell, S. Root, P. Kirchner, N. Fiddler, K. Leary, M. Moskowitz, D. Lucero: Marine Science Institute, UCSB

For the last decade, high-altitude lakes of the Sierra Nevada and their catchments have been studied to assess their susceptibility to acidic atmospheric deposition. Some lakes were found to undergo episodic acidification during snowmelt and during intense summer rains. Experimental studies identified some aquatic organisms as sensitive to pHs of about 5.5. However, chronic (i.e.., long-term) acidification of lakes and streams is unlikely under present acid-deposition rates. Funding: California Air Resources Board.

EOS NASA Project-- John M. Melack, Marine Science Institute and Department of Biological Sciences, UCSB
--Jeff Dozier, Department of Geography, UCSB

V. B. Aizen, E. Lolctionova: Russian Academy of Sciences
R. Kattelmann: UCSB

As an extension of a decade long studies of Sierran catchments, applications of remote sensing of snow with optical and microwave systems, hydrological and hydrochemical modeling and experimental studies are in progress. Funding: EOS NASA Project.

Episodic Acidification of High-Elevation Sierra Lakes-- John L. Stoddard, Mantech Environmental

M. M. Erway: Mantech Environmental
P. Kirchner, K. Leary, N. Fiddler, M. Moskowitz, J. Sickman, R. Erway: Marine Science Institute, UCSB

The Sierra Episodes Study is a project to study episodic acidification of high-elevation Sierra Lakes. We collect daily snowmelt runoff samples from nine lake outlets and analyze the samples for acid/base chemistry. Funding: California Air Resources Board and the U. S. Environmental Protection Agency.

back to top

Terrestrial Botany

Biological and Physical Processes Determining the Development of an Alkaline Playa Sand-dune Ecosystem--
Catherine A. Toft, Center for Population Biology, UC Davis
Deborah L. Elliott-Fisk, Department of Geography, UC Davis
James H. Richards, Department of Land, Air and Water Resources, UC Davis
L. Donovan, UC Davis/University of Georgia
N. Ives: McGill University
C. Hinkson, A. Cook, M. Rillig: SDSU, UC Davis
S. Gordon, S. Chirman: High school volunteers
Visiting scientists: A. Danin: Israel, A. Berteit: Stanford, R. Zimmerman: JPL-CalTech
J. Frensch, P. Meyerhof, J. Schaber, K. Fort, G. Kyser, D. Chirman, R. Rosecrance, B. Bladon, S. Matzner, B. Rojas Lara, S. Eppley, G. Ludwig, M. Muller, G. Besne, E. Rowell, C. de Leon Horton, A. Koeberle, D. Schwarzbach, K. Vandermer, R. Mazur, D. Dudley: UC Davis

The goal of the research we are conducting on the north shore of Mono Lake, CA is to understand the biological and physical processes determining the development of an alkaline playa sand-dune ecosystem. The site is typical of highly saline alkaline Great Basin lake-bed playas, which were produced by recession of pluvial lakes due to past climate change and, in some, from anthropogenic changes in the lakes' water budgets. We are investigating aspects of a conceptual model of desert succession that emphasizes abiotic, plant, and animal ecosystem components on a time scale appropriate to the development of desert ecosystems (i.e. centuries). We have chosen sites, or are sampling transects, along the playa-to-diverse-dune gradient where the substrate became available for colonization very recently (10 yr.) up to many hundreds of years ago. We are: 1) quantifying ecosystem characteristics (soil and water chemistry, stratigraphy, substrate and landform age, plant and animal diversity and density) along a continuous 2200-m horizontal gradient from the current, changing lake shore to mature stabilized dunes, and 2) testing experimentally the relative importances of crucial processes that guide and constrain the development of terrestrial ecosystems in deserts. The experiments test hypotheses regarding the physical and physiological constraints that plants have in migrating to, germinating on, establishing on, and propagating on highly saline, highly alkaline, and dry substrates that have very limited nutrient availability. Results of this study will allow a major advance in the understanding of succession in desert ecosystems, a topic of long-standing and unresolved debate. More importantly the project will rigorously test hypotheses about biogeochemical, ecophysiological, and plant- and animal-population mechanisms operating at several stages during development of semi-stabilized dunes in desert playa environments. The results of the study can be directly applied to ecosystem restoration and revegetation in the western United States, particularly where saline, alkaline, or chemically unfavorable substrates have been desiccated by diversions of water for agricultural or urban uses. Applications to other desert locations are also envisioned as we increase our understanding of the interactions between abiotic and biotic constraints to the success of plants in these environments. Funding: USDA Competitive Grants.

Effects of Induction of Wound Responses of Nicotiana attenuata on Herbivore and Plant Performance --Rick Karban, Department of Entomology, UC Davis

During this past spring I initiated an experiment to evaluate the effects of induction of wound responses of Nicotiana attenuata on herbivore and plant performance. Nicotiana attenuata synthesizes nicotine when it is damaged by herbivory. This response can also be induced by application of methyl jasmonate to the roots of plants. Methyl jasmonate appears to act as the signal that moves through the plant and turns on other defensive responses as well. I induced some plants with minute concentrations of methyl jasmonate and kept other plants as water controls. Jasmonate treated plants had higher whole-plant concentrations of nicotine, confirming previous laboratory findings. Plants treated with jasmonates also suffered less damage by cutworm larvae. Data evaluating the effects of this treatment on plant fitness are still being collected. An important herbivore of Nicotiana attenuata in some years is the tobacco hornworm, Manduca quinquemaculata. This year populations of hornworms were low at the reserve. Adult moths were preferentially attracted to tall N. a. plants and those that were in close proximity to other flowering species. Hornworm larvae were placed on plants that had been treated with methyl jasmonate and on untreated controls. Although sample sizes were small, the results suggested that hornworm growth was retarded on plants induced with jasmonates.

The Effect of Herbivory on the Growth of Rabbitbrush-- Heidi West, California State University at Chico

Native plant species adapted to highly alkaline and saline soils have colonized the recently exposed Mono Lake playa. These plants provide ground cover that dampens the effects of dust and sand storms. Reproduction and growth of plants on the exposed lake bed, therefore, aids in decreasing hazardous airborne material. Rabbits are one of the dominant herbivores of Chrysothamnus nauseosus (Rabbitbrush) around Mono Lake. This study examines the effects of herbivory by these animals on four juvenile populations of this plant in the Mono Dunes. Currently, little information exists on herbivory of native species around Mono Lake. In each population, thirty plants have been chosen and randomly assigned to one of three treatments. These three treatments are defined as follows: one third are fenced herbivore-exclusion plots, another third are fenced herbivore exclusion plots artificially subjected to a specific amount of herbivory by the experimenter, and the last third (i.e.: control) are unfenced, unmanipulated plots that are exposed to natural levels of herbivory. Effects of herbivory will be quantified by measuring plant growth in the latter two treatments and comparing these measurements with the rabbit exclusion treatment.

back to top

Terrestrial Zoology

Begging Energetics in House Wrens
Mark Chappell and Gwen Bachman, Department of Biology, UC Riverside
Robert Gibson, Department of Biology, UC Los Angeles

Our main goal is to evaluate the effectiveness of begging as an honest communication of offspring need. To do this, we are combining laboratory based measures of the energetic expenditures associated with begging with field observations of nestling begging and parental response. Funding: Academic Senate, UC Los Angeles (Gibson), UC Riverside (Chappell).

Aerobic Physiology of Belding's Ground Squirrels
Mark Chappell and Gwen Bachman, Department of Biology, UC Riverside
J. Odell: Department of Biology, UC Riverside

In July 1994 I finished up a three-year study of the aerobic physiology of Belding's ground squirrels. Basically, we looked at the aerobic capacity of the squirrels (minimal resting metabolism and the maximal oxygen consumption during exercise and cold exposure), as a function of age and sex. Aerobic capacity increases with age and is slightly but significantly larger in females than in males (even though males have somewhat larger body size). There is a correlation between an individual's minimal metabolism and its maximal performance in exercise, but not between minimal metabolism and maximal performance in cold exposure. We also examined the repeatability of aerobic performance. Repeatability is a measure of individual consistency (performance rank with respect to the rest of the population after size correction) over time. We found that maximal oxygen consumption was repeatable over periods of up to 1-2 years in adult animals, but was not repeatable between juveniles and adults. These were the first repeatability studies of aerobic performance in wild mammals.

Beetles
Roget Dajoz, Museum of Natural History, Paris
A. Dajoz

Roget and Aline Dajoz made their fourth lengthy visit to SNARL in their ongoing study of the ecology and biodiversity of the Order Coleoptera (beetles).

Development of Alarm-call Responses in Belding's Ground Squirrels
Warren Holmes, Psychology Department, University of Michigan
J. Mateo: Psychology Department, University of Michigan
A. Bell and L. Starr: University of Michigan graduates

In 1994 we continued our research at SNARL investigating the development of alarm-call responses in Belding's ground squirrels. Adults emit vocalizations when a predator is sighted that warn colony members of danger. When juveniles first appear above ground at weaning they do not exhibit adult-like responses to alarm calls or other auditory stimuli, despite being quite vulnerable to predation. We observed animals in 10 x 10 meter outdoor enclosures at SNARL that mimic a ground squirrel's natural habitat. By playing back recordings of vocalizations and filming ground squirrel responses, we have studied how juveniles learn to respond appropriately to alarm calls. We have found that juveniles begin to make adult-like responses by observing other ground squirrels, particularly their mothers. Juveniles housed without adults take longer to develop discriminative responses, that is, respond selectively to alarm calls but not to non-alarm calls. Experiences both before and after weaning influence juvenile alarm-call responses, suggesting that their defensive behavior may be sensitive to the local predator environment (e.g. the number or types of predators). In general, juveniles quickly learn how to respond to alarm calls that warn them of potential danger, aided in part by observing the responses of nearby ground squirrels. Funding: NSF, National Institute of Mental Heath, and the University of Michigan.

back to top