Situated in a transitional region among the Mojave, Sonoran, and Great Basin Deserts, the Granite Mountains and surrounding landscape support extraordinary biological diversity. This diversity, as well as superb examples of geomorphic processes, provides a wealth of research and teaching opportunities.
The Granite Mountains Desert Research Center provides a base of operation for those wishing to investigate not only the Granite Mountains, but surrounding features of the east Mojave Desert as well. Visiting researchers and classes are within 50 miles of the Kelso and Cadiz Dunes; the sand ramps of Devil’s playground; the recently active volcanic areas at Cima Cinder Cones and Amboy Crater; dense Joshua tree woodland on Cima Dome, bunchgrass prairie and Great Basin sagebrush in the Mid Hills; and limestone substrates, rich in species endemism, of the Providence and New York Mountains. Located 45 miles east of the Granite Mountains is the Sacramento Mountains Reserve (SMR), a satellite reserve to the GMDRC. The SMR is comprised of species more typical of the Sonoran Desert, including dense stands of Cylindropuntia bigelovii (teddy-bear cholla) and Fouquieria splendens subsp. splendens(ocotillo). It also contains outstanding examples of desert pavement.
Until relatively recently, scientific exploration of the east Mojave Desert was limited to scientists willing to confront the numerous logistical obstacles of working in a remote area. Since the establishment of the GMDRC in 1978, and with the ongoing development of research and teaching programs there, research in the region has grown considerably (see Transect vol. 26(1)). The region, however, remains ripe for scientific study and still represents a frontier for taxonomic discovery. Over the past 10 years, several new taxa have been described in the Granite Mountains, including two spiders, two vascular plants, a nematode, several insects, an ant, and a new wasp genus.
Reserve use is restricted to those conducting research or instructing a class. All researchers and instructors are required to submit an application and obtain consent by the reserve director prior to visiting the reserve. UC researchers and courses are given priority, but all teaching institutions and researchers are welcome to apply for use.
The Center has supported a wide variety of research projects and classes. Listed below are selected research projects and courses conducted at the reserve:
Selected Research Projects
James M. André (UC Riverside-GMDRC) continues his work on a comprehensive Flora of the Mojave National Preserve. To date, he has documented the range and abundance of over 900 vascular plant taxa in the Preserve, while adding more than 100 previously undocumented taxa to the 1.5 million acre area. The project has received recent funding support from the National Park Service’s Inventory & Monitoring Program. The Flora will add substantially to our understanding of floristic composition of the Preserve, while providing detailed information on rare and unique species and associations that are of high management concern. In 2006 Jim published a Flora of the Granite Mountains, a subset of his larger work in the region.
Jayne Belnap (USGS BRD) quantified and expanded our understanding of the impacts vehicles can have on recovery rates of different soil properties. They found that across desert types in the western U.S., pre-disturbance soil lichen cover was positively correlated with soil silt content, and that nitrogenase activity of biological soil crusts declined more as a result of impacts in sandy versus fined textured soils and showed greater declines in cool versus hot desert sites. In another study, Belnap and Steven Warren conducted a study comparing soil properties inside and outside tracks of military vehicles. Fifty-five years after the impacts, soil penetrability was much lower, particle size was smaller, and the most rapidly recovering components of biological soil crusts (cyanobacteria) were at most 65% inside versus outside the tracks. Recovery under plant canopies was much better than in plant interstitial spaces. For some of the most sensitive lichen species to fully recover in plant interspaces, it may take up to two millennia, assuming recovery would occur at a linear rate.
Martin L. Cody (UC Los Angeles) conducted a study on slow-motion population dynamics in Mojave Desert perennial plants. To investigate survivorship and regeneration in desert perennial plants, individual shrubs were mapped, measured and tagged on a nearly level 360 m2 plot of diverse Mojave Desert vegetation in 1981, they were re-mapped and measured 15 years later, in 1996. A large majority of the shrubs persisted between censuses. Modest birth (establishment) and death rates indicate that plants are replaced approximately every century, while the median longevity of several species is much longer. A 15-yr intercensus interval, appropriate for most species (i.e. birth and death rates were measurable), is too short for several larger shrubs (including Larrea divaricata, Ephedra nevadensis, Yucca schidigera and the larger Opuntia spp.) in which virtually no births or deaths occurred and in which longevity must be extremely high. While individuals of most species grew over the 15-yr interval, others did not, and some individuals shrank in size. In a number of species, individual growth rates were significantly reduced according to the number of neighboring plants rooted 0.5-2.0 m distant. Even Larrea tridentata, one of the largest species, showed significant effects of growth rate reduction where crowded by allospecific plants, despite the generally much smaller sizes of these neighbors.
Sharon J. Coe (UC Riverside) studied how water availability affects clutch size in Black-throated Sparrows (Amphispiza bilineata). Birds that breed in hot, arid environments experience unique physiological demands resulting from efforts to maintain positive water balance when ambient temperatures are high, but humidity and water availability are low. We provided water to sparrows on breeding territories in the Mojave Desert of southern California to examine the effects of water availability on reproduction in desert birds, independent of the increase in food availability commonly associated with increased precipitation in arid ecosystems. In both years of the study (2000 and 2001), water-supplemented (treatment) pairs laid significantly larger clutches than did control pairs. In 2000, the drier of the two years, the mean clutch size of treatment pairs was almost 0.5 eggs larger, or about 16% larger, than control pairs. Overall, the mean egg volume per nest in treatment and control pairs was not significantly different, and the mean proportion of eggs hatched was not significantly different at alpha = 0.05, but was nearly so. Daily nest survival probabilities were not greater in treatment nests than in control nests in 2000 or in 2001. Treatment nests did not produce a greater mean number of young surviving to day 8 than did control nests, although the trend is of greater means in treatment nests. The results of our study indicate that for species like the Black-throated Sparrow that are abundant in deserts, are successful in breeding there, and can survive without drinking water, water availability in arid environments can nevertheless impose limitations on reproduction.
Ammon Corl (Mathias Grant Recipient) investigated how the rate of speciation is influenced by sexual selection. Alternative mating types are quite common in nature and are the result of intense sexual selection. It has been hypothesized that alternative mating types and sexual selection will result in rapid evolution and promote speciation. I am testing this hypothesis in the side-blotched lizard, Uta stansburiana, a species that has three male mating strategies that engage in male-male competition. Specifically I am: 1. studying the geographic variation in the alternative mating strategies of the side-blotched lizard, 2. using phylogenetic comparisons to test for rapid phenotypic evolution associated with divergence of mating types across populations and, 3. conducting female choice experiments and mating trials to test whether divergence in mating types between populations can lead to reproductive isolation. Results thus far show that there is widespread geographic variation in mating strategies and that reproductive isolation can build up quite rapidly between populations that differ in their mating strategies.
Brad Coupe (Ohio State University) studied sidewinder rattlesnake (Crotalus cerastes) spatial ecology at the Kelso Dunes, reviewing three generations of research. Sidewinder rattlesnakes (Crotalus cerastes) have been well studied on the eastern edge of the Kelso Dunes system, San Bernardino Co., CA, USA. In this paper I review the information on spatial ecology of these snakes resulting from my and two other studies. Male sidewinders have larger minimum convex polygon home ranges than females during the mating seasons and this likely results from males moving greater distances rather than more often than females. However, no significant differences are observed in home range size when other seasons are included. Potentially this is a result of migration movements made by both sexes to overwintering sites on the edge of the dunes. Males and females have similar movement frequencies, although these are variable seasonally and between studies. Additionally, I noted females to be more variable in movement frequency. Meander ratios (actual distance moved/net distance moved) were larger in the other studies than in mine, and in my study varied according to sex, season, and year. Lastly, data from previous studies allowed me to estimate sidewinder population density at 0.48-1.18 snakes per hectare.
Clinton W. Epps (UC Berkeley) conducted an exhaustive study of the evolution and genetics of desert bighorn sheep leading to the completion of his PhD in 2005. Working in more than a dozen mountain ranges in the eastern Mojave Desert, Epps studied how diet (nutrition) and habitat parameters influence sheep behavior and population genetics. The outcome of this work will greatly assist management efforts, which may continue to depend upon reintroductions of rare species in the desert.
Laurelin Evanhoe (Cornell University) is studying the population genetics and community ecology of native bees in the east Mojave Desert. The primary objectives of her research are to: (1) perform a comparative genetic study of two congeneric bee species (one specialist, one generalist) to examine how specialized foraging may affect population size, structure, and probability of extinction, (2) to create a long-term record of the diversity and abundance of bees that pollinate plants in two predominant vegetation types (cactus-yucca scrub and creosote-bush scrub), (3) to document the frequency with which each bee interacts with each plant species, and (4) to quantify the dependence of bees on plants (and vice versa) to predict the response of these plant-bee communities to species loss. Additionally, Laurie is collaborating with Terry Griswold (USDA-ARS Bee Lab, Utah State University) to produce a preliminary list of bee species for the east Mojave Desert.
Joy Giffin (Desert Research Institute, University of Nevada, Reno) is studying the geomorphic processes of storage, stability, and transport of sediment in desert basins during periods of paleoclimate change. The December 2004 flood event in Granite Cove and on bajadas throughout the region has a return time of 50 – 100 years, providing an ideal case study for Joy’s work. Joy is also studying the effects of wildfire on desert slopes. The Hackberry Fire burned 70,000 acres in the Mid Hills area in June, 2005, providing an excellent location for this field study. Joy is looking at vegetative cover, soil properties, and sediment movement in burned and unburned areas of the region.
Eric P. Hamerlynck, Joseph R. McAuliffe, Stanley D. Smith, and Eric V. McDonald (Rutgers University, Arizonia Desert Botanical Garden, UNLV, Desert Research Institute – Reno, Nevada) have teamed up to explore the complex dynamics between soil characteristics and plant physiological performance among different aged alluviums on the west side of the Providence Mountains. They analyzed leaf nitrogen, carbon isotope discrimination, plant water potential, and stomatal conductance in creosotebush (Larrea tridentata). They found that co-limiting resources of water and nitrogen are highly important to creosotebush productivity and were strongly influenced by soil physiochemical characteristics and stomatal behavior. Younger, coarser soils with little horizon development and greater water infiltration had greater leaf nitrogen and lower carbon isotope discrimination, stomatal conductance, and plant water potential. Lower plant water potential suggests less soil water in the vicinity of the plant roots at the time of measurements and lower carbon isotope discrimination suggests that over time, leaf stomata are closed more often, leading to greater water use efficiency compared to plants in finer textured soils.
An additional study found that creosotebush growing in older soils with greater horizon development experienced reduced growth and greater mortality compared to populations in younger, coarser soils. At peak growth in the spring however, soils of intermediate age had individuals with the highest plant water potential. It is suggested that competition among large individuals at the young alluvial site reduced available soil water in the spring compared to the intermediate alluvial site. Results of their research have broader implications for the growth and development of vegetation associations and the potential impacts of climate change on desert ecosystems.
Thomas R. Huggins (UC Los Angeles) is studying Cecidomylid midges in the genus Asphondylia, which are a diverse group of galiforming flies on creosotebush. Tom is investigating the idea that abandoned galls of A. auripila are over-represented on some creosotebush plants, and under-represented on others (i.e., clumped). His study plots at the Granites will examine whether plant stress, manifest as lower relative plant performance, can explain these clumped gall distributions.
Bruce C. Jayne (University of Cincinnati) studied how inclines affect the escape behavior of a dune-dwelling lizard. Although previous laboratory studies have commonly determined sprinting speeds of lizards on horizontal surfaces, the speeds and slopes used during the escapes of lizards in natural habitats with variable inclines are virtually unstudied. To quantify performance and the use of inclined surfaces during escape, we took advantage of the footprints left in soft substrate and the simple surface topography of the natural dune habitat of the Mojave fringe-toed lizard, U. scoparia. The lengths of 52 escape paths ranged from 1.7-34 m, and the inclines of 1-m portions of escape paths ranged from -25degree to 28degree, which effectively encompassed the entire range of inclines in the habitat. The cumulative frequencies (N = 550) of inclines along 1-m intervals of the escape paths were not a simple random sample of the habitat. Less than 10% of the cumulative distance traveled during escape was bipedal, and the escape paths were relatively straight. Trajectories of the first metre of escapes were oriented significantly away from the presumed threat (observer) but were random with respect to the orientation of both the nearest cover and steepest incline. Eleven per cent of the cumulative number (N = 1382) of strides measured were within 90% of the maximum stride length within each path. Multiple regressions revealed that stride lengths (and hence speed) during escapes in the field were maximized on level surfaces with no turning. For lizards tested on a level racetrack in the laboratory, maximum speeds averaged 2.8 m/s (range = 2.1-3.9) and approximated 75% of the maximum performance attained in the field.
Wyatt Korff (UC Berkeley) conducted field and laboratory work to compare the running performance of two lizards inhabiting sandy areas in the desert. The Mojave fringe-toed and zebra-tailed lizards are not close relatives but both have fleshy fringes on their toes. These fringes are believed to be an example of convergent evolution, providing an adaptation that enhances the ability of these animals to run on sand. Differences in the form of the fringes may give the Mojave fringe-toed lizard greater running efficiency, compared to the zebra-tailed lizard, on certain types of sandy soils. Wyatt is using high-speed video to investigate this question, which may illustrate small-scale habitat differences between these two co-occurring species.
Megan E. Lulow, Darren R. Sandquist (UC Riverside-GMDRC, CSU Fullerton) are studying the effects of precipitation and invasive species on seasonal plant community structure in the eastern Mojave Desert. Experimental watering regimes were designed to test of effects of both precipitation amount and timing on each winter and summer seeded plant communities. Seeds of the invasive annual grass Bromus madritensis were sown into split plots of each watering regime to test for interactive effects of regime type and competitive environment. In addition to providing insight for management of native and invasive species, this study will contribute to a dearth of experimental field studies investigating the role of precipitation variables in governing annual and establishing perennial plant communities in the Mojave desert.
Junko Noguchi (Kyoto University, Japan) Is studying evolutionary adaptation on floral longevity traits in Camissonia refracta (Onagraceae, Myrtales). On bajadas in the Mojave Desert, California, Camissonia refracta occurs in at least two soil microhabitats which differ in soil coarseness and are described here as “sand” and “terrace”. Floral characters, growth form, and floral longevity traits were examined in C. refracta growing in these soil habitats. In an ANOVA, the floral characters, petal shape, petal area, pistil length, sepal length and flower tube length, differed significantly between the habitats. Plant height, the number of primary branches, and the number of secondary branches were also distinctly and significantly different between the habitats. The relationship between degree of flower opening and weather environmental data was analyzed by factor analyses. It was found that the degree of flower opening was influenced by wind speed and solar radiation. Two types of flowers with floral longevity traits were found; the one type had flowers which stayed open from a half to two days after anthesis, and the other type closed during the daytime after first anthesis and repeated opening and closing up to seven days. On floral longevity the two types significantly differed from each other in characters of petal shape and area, sepal length and lifetime length, but not on growth form characters. This suggested that differentiation of the floral longevity traits and growth form characters occurred independently of each other. It also suggested that selection has acted for the floral longevity traits in that of the two types formed through evolutionary adaptation, the “Repeat open and close” flowers were more adaptive than the flowers that “Remain open.”
Mary V. Price, Nickolas M. Waser, and Shauna A. McDonald (UC Riverside) are conducting long term research on two species of kangaroo rats (Dipodomys merriami and Dipodomys panamintinus) along an elevation gradient from the Granite Mountains to the Kelso Dunes area. Changes in the spatial distribution of these species in years of high or low population density (coincident with annual precipitation) revealed a pattern where in years with sufficient rain, D. merriami was restricted to lower elevations through competitive exclusion with D. panamintinus. In contrast, D. panamintinus was restricted to higher elevations in drought years as a result of metabolic constraints from low primary productivity. Results of the study provided an excellent example of how species distributions may be affected by physiological constraints and interspecific competition, and have implications for changes in species distribution with climate change.
Philip W. Rundel (UC Los Angeles) has a long-term study that is exploring the differences in plant communities between three winter rainfall deserts: the Mojave, Succulent Karoo of South Africa, and the Atacama Desert of Chile. Despite this similarity in broad climatic conditions, there are fundamental differences in the community architecture and species richness of plants in these three desert regions. Phil is comparing community structure, seasonal growth dynamics, and plant functional groups as clues to the multiple routes which evolution can take in adapting plants to subtle differences in ecosystem stability and dynamics, as well as the significance of regional species pools and climatic history. The Granite Mountains contains some of the most diverse desert ecosystems in the Mojave region and thus is a classic site for exploring the adaptive strategies of plant functional groups in a winter rainfall arid land.
John Hafernik and Leslie Saul-Gershenz (San Francisco State University) are conducting a long-term study addressing nest parasitism of the solitary bee Habropoda pallida (Anthophoridae) by larvae of the blister beetle Meloe franciscanus (Meloidae), and how this interaction may in turn affect two other critical interactions, pollination and herbivory. H. pallida is an oligolectic bee primarily utilizing creosotebush, Larrea tridentata, as a pollen source. Astragalus lentiginosus is a major nector source for the bee in sandy areas of the Mojave Desert. Individual Habropoda bees may visit up to 50,000 flowers in a lifetime and are thus probably important in influencing the floral diversity of sandy desert areas. Adult M. franciscanus are important winter and early spring herbivores of A. lentiginosus and thus may also affect plant diversity, vegetation cover and nectar availability.
This study is being conducted at two sites, the Desert Studies Center and the Kelso Dunes. They have been sampling bees and beetles in those areas for the last 20 years and conducting an intensive study. The results so far indicate that M. franciscanus is unusual among blister beetles in that its first instar larvae form large aggregations of up to 2000 larvae on bunchgrasses and the dried remains of dicots in the dune areas. These aggregations appear to be a novel adaptation for host-finding as they frequently attach, as a group, to males of H. pallida resulting in male bees carrying over 100 triungulins. They hypothesize that the triungulin larvae are dispersed to females by a type of “venereal transmission” as multiple males attempt to mate with a female. This mating behavior may also disperse triungulins among other males. Once on a female, a triungulin is carried to the bee’s nest where it drops off and feeds on the bee’s larvae and pollen and nectar provisions.
This interaction may be important for maintaining community structure in the Kelso Dunes and surrounding creosotebush flats. Loss of the bee could affect seed set and thus recruitment for several plant species. Loss of the beetle could affect winter growth rates of A. lentiginosus and other species altering vegetation cover of it and other species. These events in turn could lead to a cascade of changes within the dune community. Managers wishing to conserve or restore dune habitat in the Mojave should include the following in their plans: 1) Nesting sites for H. pallida and other bees; 2. Pollen and nectar sources for bees; 3, Aggregation sites for trungulin larvae, and 4. Food plants for adult blister beetles.
Amy Toulson (Smith College, MA) is studying the genetic structure of populations of Joshua tree (Yucca brevifolia ). She sampled leaf samples from five populations distributed across the range of the species. She measured nuclear and chloroplast markers from 48 trees in each population. Results of this study will have great relevance to the integrity of revegetation programs for Joshua tree.
Alex Van Dam and Matthew Van Dam (UC Riverside) are studying the biogeography and ecology of dune endemic insects in the Sonoran and Mojave Deserts of California over 10 dune systems, including the nearby Cadiz, Dumont and Kelso Dunes. Their study examines the degree to which altered sand transport pathways have impacted biogeographical patterns of speciation. They hypothesize that more closely related taxa are found along the same transport pathways and more distant taxa found along separated sand transport pathways. They are testing this hypothesis by studying the heterogeneity of DNA of sand roaches Arenivaga (Polyphagidae) and giant flower loving flies Rhaphiomidas (Mydidae) and sand endemic beetles Psuedocotalpa (Sarabaeidae) across the range of their distributions.
John D. Wehausen (UC San Diego, White Mountain Research Station) has studied desert bighorn sheep for the past 3 decades. One focus of John’s research has been on the importance of diet quality and quantity in lamb survivorship. Analysis of rainfall patterns, plant nutrient availability, and lamb survivorship revealed that nutrient quality is largely driven by the amount of precipitation in October, and that February is important in prolonging the growing season and promoting growth of cold intolerant species. The amount of winter precipitation is the most important season in lamb survivorship and the high variation in annual precipitation in the Mojave Desert, not variation in the timing of precipitation, poses the greatest challenge to lamb recruitment.
Selected Courses
UC Santa Cruz – Natural History Field Quarter (Steve Gliessman and Breck Tyler)
Among the longest running classes at the Granite Mountains, UCSC’s Natural History Field Quarter was originally taught by NRS co-founder Ken Norris. This 15-unit field course uses several NRS reserves and other California wild lands in teaching students to develop skills of natural history observation and interpretation. Students gain the ability to identify plants, animals, vegetation types, and landscapes, as well as address the complex issues of preservation and management of these resources.
UC Santa Barbara – Physiological Plant Ecology (Bruce Mahall)
Both undergraduate and graduate students participate in Bruce Mahall’s Physiological Plant Ecology Class, with activities including independent, non-destructive, research projects designed and conducted by the students. These projects usually involve measurements of water relations, energy budgets, gas exchange, and other techniques that have been taught during the quarter.
UC Los Angeles – Field Biology Quarter (Ken Nagy and Peter Nonacs)
Undergraduate students (up to 15, max.) conduct field research projects of up to 2 weeks in duration. Students work in groups of 2 or 3 to conduct projects on physiology and ecology of desert animals living in the area. The field component is preceded by two weeks of intense lectures at UCLA, during which time students will have conceived a project, planned data gathering, and practiced techniques for carrying out their research. Students analyze and graph/chart data while still at Norris Camp and prepare a scientific research paper as well as a symposium presentation on their project for submission/presentation the week after returning to UCLA.
Cabrillo Community College – Field Biology (John Carothers).
John introduces students to natural history classification, distribution, ecology, and evolution of common plants and animals, emphasizing biological field methods in the study of biotic populations. Along with sharing identification methods for native plants and animals, John encourages students to explore how ecological, behavioral, and evolution theory is reflected in patterns among desert communities. Based out of Yucca Bajada Camp, students are exposed to a primitive camping experience and long hours of intensive learning.
UC Riverside – Evolutionary Ecology of Terrestrial Vertebrates (John Rotenberry and Marlene Zuk)
The purpose of the class as a whole is to introduce students to the classification, identification, and adaptations of terrestrial vertebrates, all placed in an evolutionary context. Field trips are designed to expose students to a diversity of vertebrates in a natural environment, in part to help develop skills in identification, in part to provide them an opportunity to interpret the adaptiveness of structure and behavior in an ecological setting. Most activities are strictly observational; however, occasionally the students capture herps by hand for detailed examination. Although captured herps may be temporarily removed, all are returned to the original site of capture and released within a few hours.
UC Riverside – Introductory Petrology (Michael McKibben)
We use the Granite Mountains Reserve (specifically Norris Cabin) as a central base for having junior and senior undergraduate Geology students examine a variety of geologically important rock types in the eastern Mojave desert. These include the geologically young Quartenary basalt cinder cones at Pisgah and Cima, a thick sequence of Miocene explosive volcanic rocks in the adjacent Van Winkle Mountains, Cretacous granitic and metamorphic rocks hosting iron ore deposits at the nearby Vulcan mine, and ancient Precambrian and early Paleozoic fossiliferous sedimentary rocks in the Marble Mountains to the southeast. In addition the reserve itself contains rapidly uplifted lower crustal Jurassic and Cretaceous granitic rocks as well as interesting geomorphic landforms, including one of the largest alluvial fans in the entire desert.
CSU Pomona – Herpetology (Glenn Stewart)
The purpose of the class is to familiarize students with the herpetofauna of the Mojave Desert. Students observe lizards, snakes and toads in their natural habitat. In addition, they capture (by hand, noose or thongs) and identify examples of the species observed. Representative specimens are held overnight for demonstration and discussion by the instructor, then released at or near their sites of capture.
Pepperdine University – Introduction to Ecology (Lee Katz)
The purpose of this course is to introduce undergraduate biology students to the ecology of the high desert, with particular emphasis on the vertebrate diversity of this ecosystem. Accordingly, class visits involve hikes to explore the structure of the desert landscape, early morning bird walks, and the capture, identification and release of reptiles and small mammals. Reptiles are captured, examined, identified, and released as opportunity allows. Eighty Sherman traps (deployed in four transects) are set for two evenings to sample the small mammal populations of different microhabitats. An additional point of this visit is to stress to students the overall fragility of the desert environment, and consistent with this participants keep the impacts of their visit to a minimum for area plant and animal populations.
Pomona College – Vertebrate Biology (Nina Karnovski)
Following the retirement of Bill Writz, Nina has deftly continued the tradition of Pomona College student visits to the Granite Mountains in her Vertebrate Biology class. Although the class focuses on primarily on observing the herps, mammals, and birds of the area in their natural setting, Nina also introduces students to capture methods of various vertebrate species. Occasionally students catch lizards and measure their temperatures with small thermistors to compare these temperatures with ambient temperatures around different habitat features.