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At least 37 records · Page 2Linked to original sources
USGS2004

Cloning, expression, cellular distribution, and role in chemotaxis of a C5a receptor in rainbow trout: The first identification of a C5a receptor in a nonmammalian species

C3a, C4a, and C5a anaphylatoxins generated during complement activation play a key role in inflammation. C5a is the most potent of the three anaphylatoxins in eliciting biological responses. The effects of C5a are mediated by its binding to C5a receptor (C5aR, CD88). To date, C5aR has only been identified and cloned in mammalian species, and its evolutionary history remains ill-defined. To gain insights into the evolution, conserved structural domains, and functions of C5aR, we have cloned and characterized a C5aR in rainbow trout, a teleost fish. The isolated cDNA encoded a 350-aa protein that showed the highest sequence similarity to C5aR from other species. Genomic analysis revealed the presence of one continuous exon encoding the entire open reading frame. Northern blot analysis showed significant expression of the trout C5a receptor (TC5aR) message in PBLs and kidney. Flow cytometric analysis showed that two Abs generated against two different areas of the extracellular N-terminal region of TC5aR positively stained the same leukocyte populations from PBLs. B lymphocytes and granulocytes comprised the majority of cells recognized by the anti-TC5aR. More importantly, these Abs inhibited chemotaxis of PBLs toward a chemoattractant fraction purified from complement-activated trout serum. Our data suggest that the split between C5aR and C3aR from a common ancestral molecule occurred before the emergence of teleost fish. Moreover, we demonstrate that the overall structure of C5aR as well as its role in chemotaxis have remained conserved for >300 million years.

Journal of Immunology↗
USGS1999

Cumulative index to chemicals and to common and scientific names of species listed in Contaminant Hazard Reviews 1 through 34

The Contaminant Hazard Review (CHR) series--sponsored by the U.S. Geological Survey, Patuxent Wildlife Research Center--synthesizes ecotoxicological data for selected environmental contaminants, with emphasis on hazards to native species of flora and fauna. From 1985 through 1998, 34 reviews were published in various report series of the U.S. Department of the Interior on agricultural pesticides (acrolein, atrazine, carbofuran, chlordane, chlorpyrifos, diazinon, diflubenzuron, famphur, fenvalerate, mirex, paraquat, toxaphene), metals and metalloids (arsenic, boron, cadmium, chromium, copper, lead, mercury, molybdenum, nickel, selenium, silver, tin, zinc), mammalian biocides (sodium monofluoroacetate), organic industrial and municipal wastes (dioxins, pentachlorophenol, polycyclic aromatic hydrocarbons, polychlorinated biphenyls), minin wastes (cyanide), and ionizing radiations. This current report is a cumulative index to the common and scientific names of all biological species listed in the first 34 reports in the CHR series, with individual species cross-referenced with contaminant hazard review and corresponding page numbers. A similar index for chemicals is included.

Biological Science Report↗
USGS2007

Mammal inventories for eight National Parks in the Southern Colorado Plateau Network

Historically, the Colorado Plateau has been the subject of many geological and biological explorations. J. W. Powell explored and mapped the canyon country of the Colorado River in 1869 (Powell 1961). C. H. Merriam, V. Bailey, M. Cary, and other employees of the Bureau of Biological Survey conducted biological explorations of the area in the late 1800s. In recent times, researchers such as S. D. Durrant (1952), Durrant and Robinson (1962), D. M. Armstrong (1972), J. S. Findley et al. (1975), D. F. Hoff meister (1986), and J. Fitzgerald et al. (1994) have made considerable contributions to our understanding of the fauna of the Colorado Plateau. Despite earlier efforts, biological details on many regions of the plateau have remained insufficiently explored. In an effort to gather valuable biological information, the National Park Service (NPS) initiated a nationwide program to inventory vascular plants and vertebrates on NPS lands (Stuart 2000). The U.S. Geological Survey, Fort Collins Science Center, Arid Lands Field Station became a cooperator on this effort in 2001, when we began mammalian inventories on five parks within the NPS Southern Colorado Plateau Network (SCPN): Aztec Ruins National Monument (AZRU), El Morro National Monument (ELMO), Petroglyph National Monument (PETR), Salinas Pueblo Missions National Monument (SAPU), and Yucca House National Monument (YUHO). Existing baseline data on mammalian occurrences in these parks varied from very sparse to moderate, with little information available for most parks. In most cases, information was insufficient to assess the status of species of local concern. A final report on inventory efforts on these five parks was submitted in February 2004 (Bogan et al. 2004). In 2003, biologists from the Arid Lands Field Station began work on three additional parks in the SCPN: Bandelier National Monument (BAND), Chaco Culture National Historical Park (CHCU), and El Malpaís National Monument (ELMA). The primary emphasis at these three parks was on nonvolant mammals, as personnel from the Field Station had worked earlier on bats at all three parks (Bogan et al. 1998, Valdez et al. 2002a, 2002b). A final report on inventories at these three parks was submitted in April 2005. This publication details fieldwork conducted in all eight parks from 2001–2004. The information that appears here was originally contained in two separate reports that have been combined in order to make it easier for readers to find information on SCPN mammal inventories. To remain faithful to the original reports, and because of slightly differing objectives, personnel, and emphases at the two sets of parks, we have generally presented the methods, results, and recommendations separately for the 5-park and 3-park inventories.

Natural Resource Technical Report↗
USGS1995

Population biology of the Florida manatee

The Florida manatee ( Trichechus manatus latirostris ) is a unique element of the U.S. fauna. It is a distinct subspecies of the West Indian manatee (Domning and Hayek 1986) and one of the largest inshore mammals of the continent, reaching weights to 1,650 kg (Rathbun et al. 1990). Annual migratory circuits of some individuals through the intracoastal waterways of the Atlantic Coast are 1,700 km round trips at seasonal travel rates as high as 50km/day (*3 Reid and O'Shea 1989; Reid et al. 1991), resulting in one of the longest remaining intact mammalian migrations in the eastern United States.

Information and Technology Report↗
USGS2025

Mammalian scent lures fail to increase detections of invasive Burmese pythons (Python bivittatus)

Burmese pythons ( Python bivittatus ) are large constricting snakes native to Southeast Asia that have invaded the Greater Everglades Ecosystem in South Florida, USA. Pythons have caused precipitous declines in native mammals and are exceedingly difficult to detect using traditional methods such as scout snakes, detection dogs, and visual surveys. Live mammal lures have previously been used to attract pythons, with rabbits outperforming rodents in increasing detection. While live mammal lures can increase python detection and identify hotspots of python activity, ensuring animal welfare and logistical challenges limit their utility. As part of this study, field experiments were conducted to determine if mammalian lures, derived from rabbits (feces, urine, and hair) could replace live mammals and increase the detection of pythons. We ran trials for 84 days from June to September 2022 for 21 paired plots across three study sites in the Greater Everglades. We monitored two groups, the treatment (i.e., rabbit scent) and control (i.e., soil) with camera traps on a 1-minute time lapse. We detected 11 pythons during our study, but there was no difference between controls with soil ( n = 7) and treatments (n = 4). However, we did find that scent lures increased native snake detection. This pattern was best explained by an increased number of rodents at the scent lures. Our experiment indicates that mammalian scent lures alone are insufficient to attract pythons. Since live mammals can attract pythons, but scent lures cannot, future studies could examine if a multi-faceted lure combining several stimuli (i.e., heat, visual, movement) might increase python detection.

Florida↗
USGS1997

Status and management of the PaliIa, an endangered Hawaiian honeycreeper, 1987-1996

A single, relictual population of Palila Loxioides bailleui, a Hawaiian honeycreeper, survives on the slopes of Mauna Kea volcano on the island of Hawai'i, where it feeds principally on flowers and green seeds of the mamane tree Sophora chrysophylla. The Palila was listed as an endangered species by state and federal governments because of continuing damage to its habitat by browsing Feral and Mouflon Sheep Ovis aries and O. musimon and Goats Capra hircus and because of the bird's restricted range and low numbers. Ecology of the Palila was studied from 1987 to 1996. Annual population estimates fluctuated between 1 600 and 5 700 and averaged 3 400 birds. Estimates varied with availability of mamane seeds, which are less abundant in drought years. In drought years, most birds did not attempt to breed, and survival rates were lower because of a shortage of food. Availability of mamane seeds also showed large seasonal variability. While some nests were preyed upon by Owls Asio flammeus, Cats Felis catus and Rats Rattus rattus, losses were high at the end of the season from unexplained death of eggs and chicks. Genetic studies did not implicate inbreeding depression. Neither avian malaria nor avian pox appeared at this site, where the mosquito vector was absent. However, weather and food shortage worsened towards the end of the nesting season. Availability of food and habitat remain the principal factors limiting increase in the Palila population. Recovery efforts now focus on reducing numbers of feral ungulates, fire management, removing mammalian predators, and developing techniques for captive propagation and introduction to currently unoccupied sites within the bird's former range. Reforestation adjacent to the Mauna Kea Forest Reserve would allow the Palila population to expand and grow.

Pacific Conservation Biology↗
USGS1998

Study design and interpretation of mammalian carnivore density estimates

Ecological theory and wildlife management often depend on reliable comparison and interpretation of population density estimates. A synthesis of 1,772 mammalian carnivore population estimates (713 unique to reference, species, site, and size of study area) from 74 species revealed global patterns among aspects of study and interpretive design that undermine the reliability and usefulness of density comparisons. The spatial extent of the study area could explain most of the variation in density, probably because study areas are typically delineated around population clusters. We related the scale-defined density estimates (regression residuals) to 28 other variables measured from the published literature, but none provided convincing biological explanation of the variation in density. Many aspects of study and interpretive design were possibly ill-suited to identifying the factor(s) influencing density. Study attributes and findings were reported inconsistently, and were subject to ideological motivations. Descriptions of vegetation were most difficult to relate to density. More intensive sampling and estimation methods produced above-average density estimates, but the differences were slight and the evidence lacking for concluding whether these more intensive methods were also more accurate. The first underlying factor extracted from principle-components analysis described the growing recognition of population declines and range reductions among large-bodied carnivores, which has also influenced study design. Another factor described an increasing trend for density to be compared and extrapolated to larger areas, but without adjusting for the effect of scale. To understand the factors influencing carnivore distribution and abundance, sampling and reporting methods (e.g., site description with maps) will need to represent the available pool of species, locations, and ecological conditions at larger-than-conventional spatial and temporal scales.

Oecologia↗
USGS2011

Vertebrate species introductions in the United States and its territories

At least 1,065 introduced vertebrate species have been introduced in the United States and its territories, including at least 86 mammalian, 127 avian, 179 reptilian/amphibian, and 673 fish species. Examples in each major taxonomic group include domestic cat, small Indian mongoose, red fox, goat, pig, rabbit, rats, house mouse, gray squirrel, nutria, starling, Indian common myna, red-vented bulbul, brown treesnake, red-eared slider, brown trout, tilapia, and grass carp. We briefly review some of these species and the types of damage they cause. We then review the basic types of methods used for control or eradication of each taxonomic group, including physical, chemical, biological, and cultural methods. We discuss some of the challenges in managing these species, including issues with the use of toxicants, land access, public attitudes, and monitoring difficulties. Finally, we list some ongoing research and future research needs, including improved detection methods, improved attractants, improved barriers, improved capture methods, fertility control, and risk assessment methods.

Current Zoology↗
USGS2009

Otters, Marine

The otters (Mustelidae; Lutrinae) provide an exceptional perspective into the evolution of marine living by mammals. Most extant marine mammals (e.g. the cetaceans, pinnipeds, and sirenians) have been so highly modified by long periods of selection for life in the sea that they bear little resemblance to their terrestrial ancestors. Marine otters, in contrast, are more recent expatriates from freshwater habitats and some species still live in both environments. Contrasts among species within the otters, and among the otters, terrestrial mammals, and the more highly adapted pinnipeds and cetaceans provide powerful insights into mammalian adaptations to life in the sea (Estes, 1989). Among the marine mammals, sea otters ( Enhydra lutris , Fig. 1) provide the clearest understanding of consumer-induced effects on ecosystem function. This is due in part to opportunities provided by history and in part to the relative ease with which shallow coastal systems where sea otters live can be observed and studied. Although more difficult to study than sea otters, other otter species reveal the connectivity among the marine, freshwater, and terrestrial systems. These three qualities of the otters – their comparative biology, their role as predators, and their role as agents of ecosystem connectivity – are what make them interesting to marine mammalogy. The following account provides a broad overview of the comparative biology and ecology of the otters, with particular emphasis on those species or populations that live in the sea. Sea otters are features prominently, in part because they live exclusively in the sea whereas other otters have obligate associations with freshwater and terrestrial environments (Kenyon, 1969; Riedman and Estes, 1990).

Book chapter↗
USGS2002

Assessing state-wide biodiversity in the Florida Gap analysis project

The Florida Gap (FI-Gap) project provides an assessment of the degree to which native animal species and natural communities are or are not represented in existing conservation lands. Those species and communities not adequately represented in areas being managed for native species constitute 'gaps' in the existing network of conservation lands. The United States Geological Survey Gap Analysis Program is a national effort and so, eventually, all 50 states will have completed it. The objective of FI-Gap was to provide broad geographic information on the status of terrestrial vertebrates, butterflies, skippers and ants and their respective habitats to address the loss of biological diversity. To model the distributions and potential habitat of all terrestrial species of mammals, breeding birds, reptiles, amphibians, butterflies, skippers and ants in Florida, natural land cover was mapped to the level of dominant or co-dominant plant species. Land cover was classified from Landsat Thematic Mapper (TM) satellite imagery and auxiliary data such as the national wetlands inventory (NWI), soils maps, aerial imagery, existing land use/land cover maps, and on-the-ground surveys, Wildlife distribution models were produced by identifying suitable habitat for each species within that species' range, Mammalian models also assessed a minimum critical area required for sustainability of the species' population. Wildlife species richness was summarized against land stewardship ranked by an area's mandates for conservation protection. ?? 2002 Elsevier Science Ltd. All rights reserved.

Journal of Environmental Management↗
USGS2010

The H4IIE cell bioassay as an indicator of dioxin-like chemicals in wildlife and the environment

The H4IIE cell bioassay has proven utility as a screening tool for planar halogenated hydrocarbons (PHHs) and structurally similar chemicals accumulated in organisms from the wild. This bioassay has additional applications in hazard assessment of PHH exposed populations. In this review, the toxicological principles, current protocols, performance criteria, and field applications for the assay are described. The H4IIE cell bioassay has several advantages over the analytical measurement of PHHs in environmental samples, but conclusions from studies can be strengthened when both bioassay and analytical chemistry data are presented together. Often, the bioassay results concur with biological effects in organisms and support direct measures of PHHs. For biomonitoring purposes and prioritization of PHH-contaminated environments, the H4IIE bioassay may be faster and less expensive than analytical measurements. The H4IIE cell bioassay can be used in combination with other biomarkers such as in vivo measurements of CYP1A1 induction to help pinpoint the sources and identities of dioxin-like chemicals. The number of studies that measure H4IIE-derived TCDD-EQs continues to increase, resulting in subtle improvements over time. Further experiments are required to determine if TCDD-EQs derived from mammalian cells are adequate predictors of toxicity to non-mammalian species. The H4IIE cell bioassay has been used in over 300 published studies, and its combination of speed, simplicity, and ability to integrate the effects of complex containment mixtures makes it a valuable addition to hazard assessment and biomonitoring studies.

Critical Reviews in Toxicology↗
USGS1998

Nesting ecology of Spectacled Eiders Somateria fischeri on the Indigirka River Delta, Russia

In 1994 and 1995 we investigated breeding biology and nest site habitat of Spectacled Eiders on two study areas within the coastal fringe of the Indigirka River Delta, Russia (71°20' N, 150 ° 20' E). Spectacled Eiders were first observed on 6 June in both years and nesting commenced by mid-June. Average clutch size declined with later nest initiation dates by 0.10 eggs per day; clutches were larger in 1994 than 1995 and were slightly larger on a coastal island study area compared to an interior area. Nesting success varied substantially between years, with estimates of 1.6% in 1994 and 27.6% in 1995. Total egg loss, through avian or mammalian predation, occurred more frequently than partial egg loss. Partial egg loss was detected in 16 nests and appeared unrelated to nest initiation date or clutch size. We found no difference among survival rates of nests visited weekly, biweekly, and those at which the hen was never flushed, suggesting that researcher presence did not adversely affect nesting success. A comparison of nine habitat variables within each study area revealed little difference between nest sites and a comparable number of randomly located sites, leading us to conclude that Spectacled Eiders nest randomly with respect to most small scale habitat features. We propose that large scale landscape features are more important indicators of nesting habitat as they may afford greater protection from land-based predators, such as the Arctic Fox. Demographic data collected during this study, along with recent conservation measures implemented by the Republic of Sakha (Yakutia), lead us to conclude that there are few threats to the Indigirka River Delta Spectacled Eider population. Presently, the Indigirka River Delta contains the largest concentration of nesting Spectacled Eiders and deserves continued monitoring and conservation.

Indigirka River Delta↗
USGS1998

Contaminant Hazard Reviews. [Reports No. 1-28 on CD-ROM.]

This compact disc (CD) contains the first 28 reports in the Contaminant Hazard Reviews (CHR) that were published originally between 1985 and 1994 in the U.S. Department of the Interior Biological Report series. The CD was produced because printed supplies of these reviews--a total of 84,000--became exhausted and demand remained high. Each review was prepared at the request of environmental specialists of the U.S. Fish and Wildlife Service and each contained specific information on mirex, cadmium, carbofuran, toxaphene, selenium, chromium, polychlorinated biphenyls, dioxins, diazinon, mercury, polycyclic aromatic hydrocarbons, arsenic, chlorpyrifos, lead, tin, index issue, pentachlorophenol, atrazine, molybdenum, boron, chlordane, paraquat, cyanide, fenvalerate, diflubenzuron, zinc, famphur, or acrolein. Each report reviewed and synthesized the technical literature on a single contaminant and its effects on terrestrial plants and invertebrates, aquatic plants and animals, avian and mammalian wildlife, and other natural resources. The subtopics include contaminant sources and uses; physical, chemical, and metabolic properties; concentrations in field collections of abiotic materials and living organisms; deficiency effects, where appropriate; lethal and sublethal effects, including effects on survival, growth, reproduction, metabolism, mutagenicity, teratogenicity, and carcinogenicity; proposed criteria for the protection of human health and sensitive natural resources; and recommendations for additional research.

Book↗
USGS2011

A novel member of the family Hepeviridae from cutthroat trout ( Oncorhynchus clarkii )

Beginning in 1988, the Chinook salmon embryo (CHSE-214) cell line was used to isolate a novel virus from spawning adult trout in the state of California, USA. Termed the cutthroat trout ( Oncorhynchus clarkii ) virus (CTV), the small, round virus was not associated with disease, but was subsequently found to be present in an increasing number of trout populations in the western USA, likely by a combination of improved surveillance activities and the shipment of infected eggs to new locations. Here, we report that the full length genome of the 1988 Heenan Lake isolate of CTV consisted of 7269 nucleotides of positive-sense, single-stranded RNA beginning with a 5' untranslated region (UTR), followed by three open reading frames (ORFs), a 3' UTR and ending in a polyA tail. The genome of CTV was similar in size and organization to that of Hepatitis E virus (HEV) with which it shared the highest nucleotide and amino acid sequence identities. Similar to the genomes of human, rodent or avian hepeviruses, ORF 1 encoded a large, non-structural polyprotein that included conserved methyltransferase, protease, helicase and polymerase domains, while ORF 2 encoded the structural capsid protein and ORF 3 the phosphoprotein. Together, our data indicated that CTV was clearly a member of the family Hepeviridae , although the level of amino acid sequence identity with the ORFs of mammalian or avian hepeviruses (13-27%) may be sufficiently low to warrant the creation of a novel genus. We also performed a phylogenetic analysis using a 262. nt region within ORF 1 for 63 isolates of CTV obtained from seven species of trout reared in various geographic locations in the western USA. While the sequences fell into two genetic clades, the overall nucleotide diversity was low (less than 8.4%) and many isolates differed by only 1-2 nucleotides, suggesting an epidemiological link. Finally, we showed that CTV was able to form persistently infected cultures of the CHSE-214 cell line that may have use in research on the biology or treatment of hepevirus infections of humans or other animals.

Virus Research↗
USGS2022

Rainforest carnivore ecology in a managed forest reserve: Differential seasonal correlates between habitat components and relative abundance

Studies of relationships between seasons and Neotropical carnivore distributions tend to focus on water and prey availability without considering other habitat components such as escape, foraging, and resting cover. Our goal was to evaluate habitat characteristics that may be important for predicting the seasonal (dry or rainy) relative abundance of four commonly captured Neotropical carnivores (i.e., jaguar [ Panthera onca ], puma [ Puma concolor ], ocelot [ Leopardus pardalis ], and grey fox [ Urocyon cinereoargenteus ]) in Chiquibul Forest Reserve in Belize, Central America. We used trail camera data and random-effect Poisson models to investigate how prey ratios (number of prey detections/total detections), cover (e.g., logs and stumps used for hiding cover from predators), vegetation structure, and environmental site characteristics (e.g., site harvest-history, slope, aspect) were related to carnivore relative abundance. Both prey ratios and vegetation structure appeared in supported models more frequently than other environmental site characteristics and were negatively correlated with carnivore relative abundance. Supported models differed for each season for all species except jaguars for which mammalian prey ratios and prey cover at sites was always negatively correlated with jaguar relative abundance. Carnivores appeared to avoid sites where vegetation created ideal escape and hiding cover for prey even though prey may be less abundant. Our data suggest that vegetation structure and composition can create conditions conducive to carnivore foraging and that these characteristics can differ by season in the tropics.

Biological Conservation↗
USGS1998

Overview of a workshop on screening methods for detecting potential (anti-) estrogenic/androgenic chemicals in wildlife

The U.S. Congress has passed legislation requiring the U.S. Environmental Protection Agency (U.S. EPA) to develop, validate, and implement screening tests for identifying potential endocrine-disrupting chemicals within 3 years. To aid in the identification of methods suitable for this purpose, the U.S. EPA, the Chemical Manufacturers Association, and the World Wildlife Fund sponsored several workshops, including the present one, which dealt with wildlife species. This workshop was convened with 30 international scientists representing multiple disciplines in March 1997 in Kansas City, Missouri, USA. Participants at the meeting identified methods in terms of their ability to indicate (anti-) estrogenic/androgenic effects, particularly in the context of developmental and reproductive processes. Data derived from structure-activity relationship models and in vitro test systems, although useful in certain contexts, cannot at present replace in vivo tests as the sole basis for screening. A consensus was reached that existing mammalian test methods (e.g., with rats or mice) generally are suitable as screens for assessing potential (anti-) estrogenic/ androgenic effects in mammalian wildlife. However, due to factors such as among-class variation in receptor structure and endocrine function, it is uncertain if these mammalian assays would be of broad utility as screens for other classes of vertebrate wildlife. Existing full and partial life-cycle tests with some avian and fish species could successfully identify chemicals causing endocrine disruption; however, these long-term tests are not suitable for routine screening. However, a number of short-term tests with species from these two classes exist that could serve as effective screening tools for chemicals inducing (anti-) estrogenic/androgenic effects. Existing methods suitable for identifying chemicals with these mechanisms of action in reptiles and amphibians are limited, but in the future, tests with species from these classes may prove highly effective as screens. In the case of invertebrate species, too little is known at present about the biological role of estrogens and androgens in reproduction and development to recommend specific assays.

Environmental Toxicology and Chemistry↗
USGS2000

Contaminant Hazard Reviews (compilation)

This compact disc (CD) contains the 35 reports in the Contaminant Hazard Reviews (CHR) that were published originally between 1985 and 1999 in the U.S. Department of the Interior Biological Report series. The CD was produced because printed supplies of these reviews--a total of 105,000--became exhausted and demand remained high. Each review was prepared at the request of environmental specialists of the U.S. Fish and Wildlife Service and each contained specific information on the following: mirex, cadmium, carbofuran, toxaphene, selenium, chromium, polychlorinated biphenyls, dioxins, diazinon, mercury, polycyclic aromatic hydrocarbons, arsenic, chlorpyrifos, lead, tin, index issue, pentachlorophenol, atrazine, molybdenum, boron, chlordane, paraquat, cyanide, fenvalerate, diflubenzuron, zinc, famphur, acrolein, radiation, sodium monofluoroacetate, planar PCBs, silver, copper, nickel, and a cumulative index to chemicals and species. Each report reviewed and synthesized the technical literature on a single contaminant and its effects on terrestrial plants and invertebrates, aquatic plants and animals, avian and mammalian wildlife, and other natural resources. The subtopics include contaminant sources and uses; physical, chemical, and metabolic properties; concentrations in field collections of abiotic materials and living organisms; deficiency effects, where appropriate; lethal and sublethal effects, including effects on survival, growth, reproduction, metabolism, mutagenicity, teratogenicity, and carcinogenicity; proposed criteria for the protection of human health and sensitive natural resources; and recommendations for additional research.

Contaminant Hazard Reviews↗
USGS2014

Climatic variation and tortoise survival: has a desert species met its match?

While demographic changes in short-lived species may be observed relatively quickly in response to climate changes, measuring population responses of long-lived species requires long-term studies that are not always available. We analyzed data from a population of threatened Agassiz’s desert tortoises (Gopherus agassizii) at a 2.59 km 2 study plot in the Sonoran Desert ecosystem of Joshua Tree National Park, California, USA from 1978 to 2012 to examine variation in apparent survival and demography in this long-lived species. Transect-based, mark-recapture surveys were conducted in 10 of those years to locate living and dead tortoises. Previous modeling suggested that this area would become unsuitable as tortoise habitat under a warming and drying climate scenario. Estimated adult population size declined greatly from 1996 to 2012. The population appeared to have high apparent survival from 1978 to 1996 but apparent survival decreased from 1997 to 2002, concurrent with persistent drought. The best model relating apparent survivorship of tortoises ≥18 cm over time was based on a three year moving average of estimated winter precipitation. The postures and positions of a majority of dead tortoises found in 2012 were consistent with death by dehydration and starvation. Some live and many dead tortoises found in 2012 showed signs of predation or scavenging by mammalian carnivores. Coyote (Canis latrans) scats and other evidence from the site confirmed their role as tortoise predators and scavengers. Predation rates may be exacerbated by drought if carnivores switch from preferred mammalian prey to tortoises during dry years. Climate modeling suggests that the region will be subjected to even longer duration droughts in the future and that the plot may become unsuitable for continued tortoise survival. Our results showing wide fluctuations in apparent survival and decreasing tortoise density over time may be early signals of that possible outcome.

California↗