Ecology Of Reptiles Research Articles

An Enhanced Method for the Use of Reptile Skin Sheds as a High-Quality DNA Source for Genome Sequencing.

With the emergence of high-throughput sequencing technology, a number of non-avian reptile species have been sequenced at the genome scale, shedding light on various scientific inquiries related to reptile ecology and evolution. However, the routine requirement of tissue or blood samples for genome sequencing often poses challenges in many elusive reptiles, hence limiting the application of high-throughput sequencing technologies to reptile studies. An alternative reptilian DNA resource suitable for genome sequencing is in urgent need. Here, we used the corn snake (Pantherophis guttatus) as a reptile model species to demonstrate that the shed skin is a high-quality DNA source for genome sequencing. Skin sheds provide a noninvasive type of sample that can be easily collected without restraining or harming the animal. Our findings suggest that shed skin from corn snakes yields DNA of sufficient quantity and quality that are comparable to tissue DNA extracts. Genome sequencing data analysis revealed that shed skin DNA is subject to bacteria contamination at variable levels, which is a major issue related to shed skin DNA and may be addressed by a modified DNA extraction method through introduction of a 30 min pre-digestion step. This study provides an enhanced method for the use of reptile shed skins as a high-quality DNA source for whole genome sequencing. Utilizing shed skin DNA enables researchers to overcome the limitations generally associated with obtaining traditional tissue or blood samples and promises to facilitate the application of genome sequencing in reptilian research.

A quantitative synthesis of and predictive framework for studying winter warming effects in reptiles

Increases in temperature related to global warming have important implications for organismal fitness. For ectotherms inhabiting temperate regions, ‘winter warming’ is likely to be a key source of the thermal variation experienced in future years. Studies focusing on the active season predict largely positive responses to warming in the reptiles; however, overlooking potentially deleterious consequences of warming during the inactive season could lead to biased assessments of climate change vulnerability. Here, we review the overwinter ecology of reptiles, and test specific predictions about the effects of warming winters, by performing a meta-analysis of all studies testing winter warming effects on reptile traits to date. We collated information from observational studies measuring responses to natural variation in temperature in more than one winter season, and experimental studies which manipulated ambient temperature during the winter season. Available evidence supports that most reptiles will advance phenologies with rising winter temperatures, which could positively affect fitness by prolonging the active season although effects of these shifts are poorly understood. Conversely, evidence for shifts in survivorship and body condition in response to warming winters was equivocal, with disruptions to biological rhythms potentially leading to unforeseen fitness ramifications. Our results suggest that the effects of warming winters on reptile species are likely to be important but highlight the need for more data and greater integration of experimental and observational approaches. To improve future understanding, we recap major knowledge gaps in the published literature of winter warming effects in reptiles and outline a framework for future research.

A global assessment of research on urban ecology of reptiles: patterns, gaps and future directions

AbstractGlobal urban expansion has multiple impacts on biodiversity and ecosystem functioning. Still, urban centres may play an important role in the conservation of reptiles, an undersampled, megadiverse and unevenly distributed group especially vulnerable to anthropogenic impacts. However, major gaps in research on the urban ecology of reptiles and species responses to urbanisation persist, which may limit our capacity to guide suitable conservation policies. We conducted a global systematic literature review to evaluate biogeographic, taxonomic and ecological research biases in the urban ecology of reptiles and ultimately to detect major gaps and steer future sampling efforts. Our database comprised 278 articles dealing with biological responses to urbanisation of 493 species across 45 countries, comprising 658 cases between a given species and specific biological response. Research on the urban ecology of reptiles was geographically and taxonomically biased. Developed countries within temperate regions were better sampled, whereas developing tropical and megadiverse countries were mostly undersampled or neglected. Among reptile orders, Testudines and Crocodylia were proportionally more studied than Squamata. Across lower groups within Squamata, lizards were present in most studies and were the biological model most commonly used. Studies evaluating biological responses associated with landscape‐level processes, behaviour and/or population dynamics were prevalent, whereas conservation, human–reptile conflicts and wildlife management were the least considered topics. Our results show that research on urban ecology of reptiles is unevenly distributed across regions and lineages. Overcoming these major gaps is an important step towards the improvement of the conservation of reptiles worldwide under the upcoming biodiversity loss scenario. Beyond spreading sampling efforts across undersampled countries, taxa and research topics to meet conservation objectives, we recommend more multidisciplinary approaches to evaluate and compare the actual performance of reptiles in urban environments and to achieve the equilibrium between human well‐being and species conservation.

A review of applications of environmental DNA for reptile conservation and management.

Reptile populations are in decline globally, with total reptile abundance halving in the past half century, and approximately a fifth of species currently threatened with extinction. Research on reptile distributions, population trends, and trophic interactions can greatly improve the accuracy of conservation listings and planning for species recovery, but data deficiency is an impediment for many species. Environmental DNA (eDNA) can detect species and measure community diversity at diverse spatio‐temporal scales, and is especially useful for detection of elusive, cryptic, or rare species, making it potentially very valuable in herpetology. We aim to summarize the utility of eDNA as a tool for informing reptile conservation and management and discuss the benefits and limitations of this approach. A literature review was conducted to collect all studies that used eDNA and focus on reptile ecology, conservation, or management. Results of the literature search are summarized into key discussion points, and the review also draws on eDNA studies from other taxa to highlight methodological challenges and to identify future research directions. eDNA has had limited application to reptiles, relative to other vertebrate groups, and little use in regions with high species richness. eDNA techniques have been more successfully applied to aquatic reptiles than to terrestrial reptiles, and most (64%) of studies focused on aquatic habitats. Two of the four reptilian orders dominate the existing eDNA studies (56% Testudines, 49% Squamata, 5% Crocodilia, 0% Rhynchocephalia). Our review provides direction for the application of eDNA as an emerging tool in reptile ecology and conservation, especially when it can be paired with traditional monitoring approaches. Technologies associated with eDNA are rapidly advancing, and as techniques become more sensitive and accessible, we expect eDNA will be increasingly valuable for addressing key knowledge gaps for reptiles.

Ontogenetic Habitat Use and Density of the Green Lizard (Lacerta bilineata) in Contrasted Landscapes in France and Italy

Habitat modification is a major factor in the decline of reptile populations. The degree of the decline has been shown to be directly related to the intensity of habitat modification. Farming practices and urbanization are just two of the factors involved indicating that the development of practices that minimize or cancel anthropogenic impacts is urgently needed to prevent further declines. This requires knowledge of population ecology of reptiles in both disturbed and pristine habitats. In this paper, we describe aspects of green lizard (Lacerta bilineata) population ecology in a forest–pasture relatively pristine mosaic habitat in central Italy and a fragmented habitat in western France. In Italy, habitat niche overlap was very high between males and females but very low between males and juveniles. For male and female abundances, general linear models showed that the adult abundances increased with the increase of Rubus bushes, whereas juvenile abundance increased with the increase of Spartium bushes. Contingency table analysis showed that juveniles were also much more frequently observed in grasslands than adults of either sexes. The observed ontogenetic structural niche pattern was likely due to intraspecific competition avoidance, competition interference, and cannibalism. The persistence of the same patterns across years demonstrates a temporal stability of the ontogenetic structural niche pattern. Over the length of the study period, population densities were stable in the Italian population, but densities were much higher by around five times in the hedgerow in the fragmented habitat in France. In the hedgerow, monthly lizard presence was uneven, with the greatest number of sightings in June and July. Overall, our study provided no support for the notion that lizard abundance/density should be lower in modified compared to unmodified habitats, and clearly revealed that a careful management of the hedgerows is crucial for the conservation of this lizard species in agro-forest ecosystems.

First evidence of convergent lifestyle signal in reptile skull roof microanatomy

BackgroundThe study of convergently acquired adaptations allows fundamental insight into life’s evolutionary history. Within lepidosaur reptiles—i.e. lizards, tuatara, and snakes—a fully fossorial (‘burrowing’) lifestyle has independently evolved in most major clades. However, despite their consistent use of the skull as a digging tool, cranial modifications common to all these lineages are yet to be found. In particular, bone microanatomy, although highly diagnostic for lifestyle, remains unexplored in the lepidosaur cranium. This constitutes a key gap in our understanding of their complexly interwoven ecology, morphology, and evolution. In order to bridge this gap, we reconstructed the acquisition of a fossorial lifestyle in 2813 lepidosaurs and assessed the skull roof compactness from microCT cross-sections in a representative subset (n = 99). We tested this and five macroscopic morphological traits for their convergent evolution.ResultsWe found that fossoriality evolved independently in 54 lepidosaur lineages. Furthermore, a highly compact skull roof, small skull diameter, elongate cranium, and low length ratio of frontal and parietal were repeatedly acquired in concert with a fossorial lifestyle.ConclusionsWe report a novel case of convergence that concerns lepidosaur diversity as a whole. Our findings further indicate an early evolution of fossorial modifications in the amphisbaenian ‘worm-lizards’ and support a fossorial origin for snakes. Nonetheless, our results suggest distinct evolutionary pathways between fossorial lizards and snakes through different contingencies. We thus provide novel insights into the evolutionary mechanisms and constraints underlying amniote diversity and a powerful tool for the reconstruction of extinct reptile ecology.

Editorial for the Michael Bull special issue

A review of the role of parasites in the ecology of reptiles and amphibiansParasite in peril? A new species of mite in the genus Ophiomegistus Banks (Parasitiformes: Paramegistidae) on an endangered host, the pygmy bluetongue lizard Tiliqua adelaidensis (Peters) (Squamata: Scincidae)

Age-Dependent Utilization of Shelters and Habitat in Two Reptile Species with Contrasting Intraspecific Interactions.

Simple SummaryIntraspecific interactions are known to affect habitat use in birds and mammals but their role in spatial ecology of reptiles is far less recognized. Our comparative study shows that species known to exhibit intraspecific predation (smooth snake Coronella austriaca) express clearly different patterns of habitat and shelter occupancy than a species with no such cannibalistic behavior (slow worm Anguis fragilis). Specifically, juvenile smooth snakes prefer sites and shelters not occupied by the adults, even despite suboptimal habitat conditions. We propose that such division indicates an avoidance of predation pressure set by larger individuals on the younger and smaller ones. On the contrary, in slow worms no tendency for intraspecific avoidance are observed, since specimens of different ages commonly share the same area and shelters. This points to higher flexibility in habitat use in slow worms, while the smooth snake population is spatially structured, with juveniles dispersed to the margins of the population range. For endangered smooth snakes, habitat conservation should therefore include a wide buffer zone to maintain the youngest fraction of the population. Future studies on habitat utilization in squamates needs to pay more attention to the social cues, a commonly overlooked aspect in the spatial ecology of reptiles.Reptiles undergo worldwide decline driven mostly by habitat change. Detailed recognition of factors underlying spatial structure and habitat utilization is therefore a prerequisite of effective conservation of this group. While the body of data on spatial ecology of reptiles is rapidly growing, studies on social factors remain still underrepresented. We studied age-specific patterns of shelter use, range size, and habitat preferences in the context of intraspecific interactions in the smooth snake Coronella austriaca—known to exhibit intraspecific predation—and the limbless lizard slow worm Anguis fragilis—with no such behavior observed. Despite smaller availability of preferred microhabitats, juveniles of smooth snakes occupied habitat and shelters located at the edge of the population range that did not overlap with adults. No such pattern was observed in the slow worm. Our study indicates that intraspecific interactions affect the spatial ecology of squamates. Passive and active protection of habitat must include wide buffers to preserve the poorly detectable young fraction of the population.

A review of the role of parasites in the ecology of reptiles and amphibians

AbstractA great diversity of parasites, from viruses and bacteria to a range of remarkable eukaryotic organisms, exploit reptile and amphibian hosts. Recent increases in the emergence of infectious disease have revealed the importance of understanding the effects of interactions between hosts and their parasites. Here we review the effects of parasite infection on a range of demographic, behavioural, genomic and physiological factors in reptile and amphibian species. Reviewing these parasite roles collectively, and prioritising areas for research, advances our ecological understanding and guides direction for conservation in a time of rapid species decline. Poorly resolved systems include Gymnophionan amphibians and Crocodilian hosts, in addition to viral and bacterial parasites. Future research should seek to understand processes enabling population recovery and examining synergistic interactions of parasites with fragmentation, climate change and other processes that threaten species persistence.

Effect of temperature on the locomotor performance of species in a lizard assemblage in the Puna region of Argentina.

Locomotion is relevant to the ecology of reptiles because of its presumed influence on an organism's Darwinian fitness. Moreover, in ectothermic species, physiological performance capacity is affected by body temperature. We analyzed two components of locomotor performance in three species of lizards, Phymaturus extrilidus, Liolaemus parvus, and Liolaemus ruibali, in the Puna environment of Argentina. First, we estimated the thermal sensitivity of locomotion by measuring sprint speed at four different body temperatures. We included two measures of sprint speed: initial velocity and long sprint for sustained runs. Based on these data, we calculated the optimal temperature for performance and the optimal performance breadth. We also estimated endurance capacity at a single temperature. Maximum sprint speed for L. parvus was greater than L. ruibali and P. extrilidus in both initial velocity and long sprint. In contrast, L. parvus exhibited lower levels of endurance than L. ruibali and P. extrilidus. However, endurance in L. ruibali exceeded that of P. extrilidus. The species differed in the optimal temperature for the initial velocity with the lowest for L. ruibali (31.8°C) followed by P. extrilidus (33.25°C) and then L. parvus (36.25°C). The optimal temperature for long sprint varied between 32 and 36°C for all species. We found that all species attained maximum performance at body temperatures commonly experienced during daily activity, which was higher than the thermal quality of the environment. We found evidence for thermal sensitivity in locomotor performance in these species. However, we also show that the broad thermal breadth of performance suggests that the lizards are capable of sustaining near optimal levels of locomotor performance at ambient temperatures that would appear to be suboptimal. Thus, this lizard assemblage is capable of coping with the highly variable climatic conditions in the Puna region of Argentina.

A possible new specimen of Ruhuhuaria reiszi from the Manda Beds (?Middle Triassic) of southern Tanzania and its implications for small sauropsids in the Triassic

ABSTRACTDuring the recovery from the end-Permian extinctions in the Middle Triassic, small reptiles (<50 cm) are exceptionally rare, and this gap in the fossil record inhibits our understanding of small reptile ecology and evolution during such a critical transition in Earth history. Here, we fully describe two fragments of left and right hemimandibles of a small sauropsid (UMZC T1162) that likely belonged to the same individual. The specimen bears anteriorly enlarged dentary teeth and labiolingually expanded crown bases, two character states unique to Ruhuhuaria reiszi (Procolophonoidea: Owenettidae), a taxon recently described from the same locality. From this, we tentatively assign UMZC T1162 to Ruhuhuaria reiszi. Micro-computed tomography (CT) and scanning electron microscopy (SEM) were employed to fully examine the morphology of the new specimen and illuminate details of the teeth not available in the holotype. The dentition of UMZC T1162 is better preserved than that of the holotype and shows that the more posterior teeth of this animal were chisel-shaped rather than pointed, that at least some of the teeth were transversely expanded at the base, and that tooth implantation is acrodont in the posterior portion and pleurodont in the anterior portion of the dentary. This potential second specimen of Ruhuhuaria reiszi complicates the previously hypothesized relationships of the taxon and further illustrates the difficulties in assigning small sauropsids to various clades in the Triassic Period. If UMZC T1162 does represent another specimen of Ruhuhuaria reiszi, it would show that small Triassic sauropsids had more variation in their tooth implantation and tooth disparity than previously appreciated.Citation for this article: Bradley, A. B., and S. J. Nesbitt. 2017. A possible new specimen of Ruhuhuaria reiszi from the Manda Beds (?Middle Triassic) of southern Tanzania and its implications for small sauropsids in the Triassic; pp. 88–95 in C. A. Sidor and S. J. Nesbitt (eds.), Vertebrate and Climatic Evolution in the Triassic Rift Basins of Tanzania and Zambia. Society of Vertebrate Paleontology Memoir 17. Journal of Vertebrate Paleontology 37(6, Supplement).

"Reptile Ecology and Conservation: A Handbook of Techniques" by C. kenneth Dodd, Jr., 2016. [book review

"Reptile Ecology and Conservation: A Handbook of Techniques" by C. kenneth Dodd, Jr., 2016. [book review

Cyclic colour change in the bearded dragon Pogona vitticeps under different photoperiods.

The ability to change colour rapidly is widespread among ectotherms and has various functions including camouflage, communication and thermoregulation. The process of colour change can occur as an aperiodic event or be rhythmic, induced by cyclic environmental factors or regulated by internal oscillators. Despite the importance of colour change in reptile ecology, few studies have investigated the occurrence of a circadian rhythm in lizard pigmentation. Additionally, although colour change also entails changes in near-infrared reflectance, which may affect thermoregulation, little research has examined this part of the spectrum. We tested whether the bearded dragon lizard, Pogona vitticeps, displays an endogenous circadian rhythm in pigmentation changes that could be entrained by light/dark (LD) cycles and how light affected the relative change in reflectance in both ultraviolet-visible and near-infrared spectra. We subjected 11 lizards to four photoperiodic regimens: LD 12∶12; LD 6∶18; LD 18∶6 and DD; and measured their dorsal skin reflectance at 3-hour intervals for 72 hours after a habituation period. A proportion of lizards displayed a significant rhythm under constant darkness, with maximum reflectance occurring in the subjective night. This endogenous rhythm synchronised to the different artificial LD cycles, with maximum reflectance occurring during dark phases, but did not vary in amplitude. In addition, the total ultraviolet-visible reflectance in relation to the total near-infrared reflectance was significantly higher during dark phases than during light phases. We conclude that P. vitticeps exhibits a circadian pigmentation rhythm of constant amplitude, regulated by internal oscillators and that can be entrained by light/dark cycles.

Aspects of community ecology of reptiles in the swamp forests of the Upper Orashi Forest Reserve (Niger Delta, Nigeria)

The study of community composition shifts due to increased habitat modifications and deforestation is a primary issue in contemporary tropical community ecology theory. As the forest habitat conversion process has been very short in Africa relative to the evolutionary temporal scale, it is likely that animal communities are not at an equilibrium. The Upper OrashiForest Reserve(NigerDelta regionofSouthern Nigeria) is a valuable case study as it is one of the few remnant deltaic swamp forest patches inside a highly developed and deforested region. In this paper, we investigated some aspects of the community ecology of reptiles of thisforestareabasedonstandardizedfieldsurveysacross26 study plots. Overall, we recorded 34 species, with the detected number of both species (34 versus 27) and individuals (562 versus 381) being higher during the wet season. Diversity/dominance diagrams showed similar trends in both seasons, but diversity measures showed that evenness was remarkably higher by wet season. Analysis of similarities (ANOSIM) confirmed that the species-richness estimate generated by Chao’s index was significantly higher for the wet season. However, the profiles of the diversity curves were comparable in the two seasons. The proportion of forest-specialist species decreased compared to that observed at the same study area 15+ years ago, with a gradual process of biotic homogenization being apparent.

Maintained effects of fire on individual growth and survival rates in a spur-thighed tortoise population

Fires strongly influence the ecology of reptiles and have both direct and indirect effects on population dynamics as they affect life history traits. Here, we examine the effects of fire on individual growth patterns and on the survival rates of a tortoise Testudo graeca population in south-eastern Spain. We compare the biometric data from recaptures 4 years before and after a fire which burned 31 % of our study area. The von Bertalanffy and Gompertz growth models best describe the individual growth patterns for males and females. In males, but not females, fire significantly decreased the time required to reach their asymptotic size (k parameter). However, adult survival analyses reveal that the local survival rates lowered for both sexes after fire. Our work evidences that the effects of fire can be complex and maintained over time, affecting different life history traits.

National peculiarities, scientific traditions and research directions

s research scientists, how do we choose our research topics, our study animals, our methods and our interpret- ations? Personal preferences are obvi- ously important, as is the role of historical contingency - mentors, funding oppor- tunities and the like. But, more general ‘national peculiarities’ - unique features of a country’s landforms, geology, climate and fauna - may also affect the kinds of science that we choose to pursue. This essay will argue that such national peculiarities influence the sorts of questions we ask, the kinds of methods we use to obtain answers, and the kinds of answers that we find satisfying. 1’11 restrict my discussion to one field (the ecology of reptiles) and two countries (Sweden and Australia), but the ideas should be generally applicable. Academic systems and regional faunas are tightly linked because most biologists work within the country that employs them. Thus, there is ample opportunity for the physical and biological character- istics of a region to affect the evolution of its scientific traditions. This linkage can be demonstrated by comparing the field of reptile ecology in two very dif- ferent countries: Australia and Sweden. Compared to Australia, Sweden is small and cold, and consequently has a low her- petofaunal diversity (six reptile species, 13 amphibians). Most of the Swedish rep- tile taxa are also widely distributed across Europe. And, as a gross general- ization, Sweden has fertile soils (at least in the south) and a high and reliable pre- cipitation regime, so that productivity in many areas is high and relatively stable from year to year. Sweden also has a long academic tradition, with some univer- sities dating back to the 1700s. What kinds of research into reptile ecology will flourish in such a land? Cer- tainly, basic natural history is not likely to be popular because the fauna has been intensively studied - both inside and out- side Sweden - for many years. Taxo- nomically oriented work will be a low pri- ority because there are few difficulties in identifying the local fauna. The strategy more likely to succeed in such a high-tech country will be sophisticated detailed re- search, closely tied to current develop- ments in theory. Conceptual and method- ological innovation will be highly prized. Academic fitness will be maximized by defining one’s research interests concep tually (e.g. as an ‘ecologist’ or ‘behav- iourist’) rather than taxonomically (e.g. as a ‘herpetologist’ or ‘mammalogist’). Two other factors reinforce this drive towards high-powered, conceptually ori- ented science. First, the relative stability of the climate (and thus, of ecological systems) encourages the development of deterministic theory. With stability comes the possibility that animals are precisely adapted to local conditions, and that eco- logical relationships are potentially explic- able in terms of manageable theoretical models. The second factor is more ped- estrian, but just as important. The long cold winter makes fieldwork on Swedish reptiles impossible for most of the year because the animals are inactive through- out this time. This enforced interregnum stimulates researchers to think long and hard about their study systems, and gives them the time to develop complex theory. It is no accident that most theoreticians come from cold climates. Australia provides a striking contrast to Sweden in most of these respects. It is a large country, covering a latitudinal range from temperate to tropical, and with a consequently high diversity in climates and vegetational associations. Australia’s nutrient-poor soils (due to its geological history) and low variable rainfall (due to its landforms and latitudinal position) result in low and variable productivity in most Australian habitats. Ectotherms (such as reptiles) tend to be better-suited to such areas than are endotherms (such as birds and mammals) that rely on a high and relatively constant food supply’. With these factors in operation, plus the fact that almost all of Australia is warm enough to support reptiles, the overall species richness and diversity of the her- petofauna is high (951 speciesz). As well as being speciose, Australia’s herpetofauna shows a high level of endem- ism because of the geological history of the Australian plate, which has remained well- separated from other reptile-bearing land- masses for long periodss. Also, even those elements of the Australian fauna that are not endemic tend to have their closest rela- tives either in the tropics (e.g. elapid snakes) or Gondwanan remnants (e.g. chelid turtles) - but certainly not in North America and Europe, the two areas with a high density of professional herpetologists. Thus, lin- eages with Australian representatives have attracted less study than equivalent lin- eages in Europe or North America, and the basic biology of most Australian rep- tiles remains poorly known. The short history of scientific study of the fauna exacerbates this

Site Attachment by the Red-Backed Salamander, Plethodon cinereus

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Ecology of Reptiles

Ecology of Reptiles

Physiological Ecology of Reptiles

Physiological Ecology of Reptiles

The Use of Co(60) as a Tag for Recovering Amphibians in the Field

Students of amphibian and reptile ecology are often vexed by the problem of determining where animals go following periods of observable activity. It is generally known that nearly all amphibian and reptile species retreat underground, but where and how deep are usually unanswered questions. Random excavation of suspected subterranean niches is usually an uncertain procedure. Many of the available data on aestivating or hibernating forms have come from chance observations or when special opportunities present themselves. Cowles (1941) utilized the chance afforded by a land clearing project to gather hibernation data on desert reptiles unearthed by a tractor and scraper. Oliver (1955) reports Latham's observations on Fowler's toad, Bufo woodhousi fowleri, plowed up in fields on Long Island, New York. Many other bits of information are scattered throughout the literature, but the fact remains that critical data on the retreat site and physiological condition of hibernating animals are usually absent from life history studies. Tagging animals with a radioactive isotope and detection with suitable instruments is a relatively new technique which has been used to advantage in field studies of mosquitoes (Hassett and Jenkins 1949; Bugher and Taylor 1949), click beetles (Brian 1947), plovers (Griffin 1952), field voles (Godfrey 1954), and moles (Godfrey 1955). Lachelt (1954) has suggested possible uses of radioactive isotopes in wildlife investigations where the transmission of radioactivity by animals in close association with each other might be used in studying mother-young or prey-predator-scat relationships. The author has been engaged in a study of the natural history of the Yosemite toad, Bufo canorus Camp, a species occupying elevations between 7000 and 1,000 feet in the Sierra Nevada of eastcentral California. In an attempt to recover toads in their subterranean retreats part of a population was tagged with radioactive cobalt during the late spring and summer of 1955. A description of the methods and, problems involved and some of the results are herein reported. Grateful acknowledgment is made of the facilities and detection equipment made available by the Radiation Safety Division, University of California, Berkeley. Horton Steel suggested the use of the radioactive method in tagging amphibians. Special thanks are due Robert Magill, Radiation Safety Engineer, for his helpful advice and active interest in the project. Dr. Robert C. Stebbins and Dr. Oliver P. Pearson kindly read the manuscript and offered valuable suggestions.