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At least 757 records · Page 42Linked to original sources
USGS2016

Safety of the molluscicide Zequanox (R) to nontarget macroinvertebrates Gammarus lacustris (Amphipoda: Gammaridae) and Hexagenia spp. (Ephemeroptera: Ephemeridae)

Zequanox® is a commercial formulation of the killed bacterium, Pseudomonas fluorescens (strain CL145A), that was developed to control dreissenid mussels. In 2014, Zequanox became the second product registered by the United States Environmental Protection Agency (USEPA) for use in open water environments as a molluscicide. Previous nontarget studies demonstrated the safety and selectivity of P. fluorescens CL154A, but the database on the toxicity of the formulation (Zequanox) is limited for macroinvertebrate taxa and exposure conditions. We evaluated the safety of Zequanox to the amphipod Gammarus lacustris lacustris , and nymphs of the burrowing mayfly, Hexagenia spp. at the maximum approved concentration (100 mg/L active ingredient, A.I.) and exposure duration (8 h). Survival of animals was assessed after 8 h of exposure and again at 24 and 96 h post-exposure. Histopathology of the digestive tract of control and treated animals was compared at 96 h post-exposure. The results showed no significant effect of Zequanox on survival of either species. Survival of G. lacustris exceeded 85% in all concentrations at all three sampling time points. Survival of Hexagenia spp. ranged from 71% (control) to 91% at 8 h, 89–93% at 24 h post-exposure, and 70–73% at 96 h post-exposure across all treatments. We saw no evidence of pathology in the visceral organs of treated animals. Our results indicate that application of Zequanox at the maximum approved concentration and exposure duration did not cause significant mortality or treatment-related histopathological changes to G. lacustris and Hexagenia spp.

Management of Biological Invasions↗
USGS2013

Habitat, wildlife and one health: Arcanobacterium pyogenes in Maryland and Upper Eastern Shore white-tailed deer populations

Background : Understanding the distribution of disease in wildlife is key to predicting the impact of emerging zoonotic one health concerns, especially for wildlife species with extensive human and livestock interfaces. The widespread distribution and complex interactions of white - tailed deer ( Odocoileus virginianus ) with humans suggest deer population health and management may have implications beyond stewardship of the animals. The intracranial abscessation suppurative meningitis (IASM) disease complex in deer has been linked to Arcanobacterium pyogenes , an under - diagnosed and often misdiagnosed organism considered commensal in domestic livestock but associated with serious disease in numerous species, including humans. Methods : Our study used standard bacterial culture techniques to assess A. pyogenes prevalence among male deer sampled across six physiogeographic regions in Maryland and male and female deer in the Upper Eastern Shore under Traditional Deer Management (TDM) and Quality Deer Management (QDM), a management protocol that alters population demographics in favor of older male deer. Samples were collected from antler pedicles for males, the top of the head where pedicles would be if present for females, or the whole dorsal frontal area of the head for neonates. We collected nasal samples from all animals by swabbing the nasopharyngeal membranes. A gram stain and catalase test were conducted, and aerobic bacteria were identified to genus and species when possible. We evaluated the effect of region on whether deer carried A. pyogenes using Pearson's chi-square test with Yates’ continuity correction. For the white-tailed deer management study, we tested whether site, age class and sex predisposed animals to carrying A. pyogenes using binary logistic regression. Results : A. pyogenes was detected on deer in three of the six regions studied, and was common in only one region, the Upper Eastern Shore. In the Upper Eastern Shore, 45% and 66% of antler and nasal swabs from deer were positive for A. pyogenes , respectively. On the Upper Eastern Shore, prevalence of A. pyogenes cultured from deer did not differ between management areas, and was abundant among both sexes and across all age classes. No A. pyogenes was cultured from a small sample of neonates. Conclusion : Our study indicates A. pyogenes may be carried widely among white-tailed deer regardless of sex or age class, but we found no evidence the pathogen is acquired in utero. The distribution of A. pyogenes across regions and concentration in a region with low livestock levels suggests the potential for localized endemicity of the organism and the possibility that deer may serve as a maintenance reservoir for an emerging one health concern.

Infection Ecology and Epidemiology↗
USGS2025

Analysis of trends in terrestrial vegetation at Mediterranean Coast Network Parks: Channel Islands National Park

The five islands comprising Channel Islands National Park (CHIS) experience natural gradients in temperature and moisture driven by ocean currents. Additionally, the islands were used as ranchlands and military land before becoming a national park, resulting in widespread erosion and vegetation change. As a result, CHIS spans gradients in climate as well as ranching duration and time since animal removal. Vegetation monitoring was initiated in 1984 on three islands (Anacapa, Santa Barbara, San Miguel), in 1990 on Santa Rosa Island, and in 1998 on Santa Cruz Island, with the goal of documenting the long-term response of island vegetation to ranch animal removal and climate fluctuations. Since that time, monitoring has documented the range of natural fluctuation in island environments over decades and provided insights into vegetation change in ecosystems unencumbered by ongoing development. Long-term vegetation monitoring at CHIS is therefore a rare example of an ecosystem experiment that demonstrates the results of management actions and serves as a baseline for land managers and scientists worldwide. Terrestrial vegetation data collected between 1984 and 2018 were modeled to estimate trends over time and to characterize relationships with covariates related to site characteristics, nonnative mammal removal programs, and water balance metrics. Data were analyzed for trends in vegetation cover, woody plant density, and plant community diversity grouped by life form and nativity across all islands and within individual islands, as well as for several individual species that dominate plant communities or present challenges to native plant recovery. In all, a total of 162 trend and covariate models were tested in this study, the details of which are provided in this report. Briefly, results reflect a decline in nonnative annual disturbance-thriving species with the reduction in animal grazing and trampling. Increasing trends were observed in native shrub density and native shrub recruitment density, as well as native shrub cover across all islands averaged together and on Santa Cruz Island. However, opposite trends were seen on the smaller islands of Santa Barbara and Anacapa, where increasing seabird activity may be damaging vegetation. Further results indicate the importance of soil moisture, relative humidity, fog, precipitation, site exposure, and solar radiation for vegetation patterns and trends. In many instances, there are apparent interacting effects of environmental variables with trends related to nonnative mammal removal and site location. Vegetation patterns in space and time emerge in the dataset as nuanced responses to interacting drivers.

Calfornia↗
USGS2015

Assessing transmissible spongiform encephalopathy species barriers with an in vitro prion protein conversion assay

Studies to understanding interspecies transmission of transmissible spongiform encephalopathies (TSEs, prion diseases) are challenging in that they typically rely upon lengthy and costly in vivo animal challenge studies. A number of in vitro assays have been developed to aid in measuring prion species barriers, thereby reducing animal use and providing quicker results than animal bioassays. Here, we present the protocol for a rapid in vitro prion conversion assay called the conversion efficiency ratio (CER) assay. In this assay cellular prion protein (PrP C ) from an uninfected host brain is denatured at both pH 7.4 and 3.5 to produce two substrates. When the pH 7.4 substrate is incubated with TSE agent, the amount of PrP C that converts to a proteinase K (PK)-resistant state is modulated by the original host’s species barrier to the TSE agent. In contrast, PrP C in the pH 3.5 substrate is misfolded by any TSE agent. By comparing the amount of PK-resistant prion protein in the two substrates, an assessment of the host’s species barrier can be made. We show that the CER assay correctly predicts known prion species barriers of laboratory mice and, as an example, show some preliminary results suggesting that bobcats ( Lynx rufus ) may be susceptible to white-tailed deer ( Odocoileus virginianus ) chronic wasting disease agent.

Journal of Visualized Experiments↗
USGS2015

Evaluation of capture techniques on lesser prairie-chicken trap injury and survival

Ethical treatment of research animals is required under the Animal Welfare Act. This includes trapping methodologies that reduce unnecessary pain and duress. Traps used in research should optimize animal welfare conditions within the context of the proposed research study. Several trapping techniques are used in the study of lesser prairie-chickens, despite lack of knowledge of trap injury caused by the various methods. From 2006 to 2012, we captured 217, 40, and 144 lesser prairie-chickens Tympanuchus pallidicinctus using walk-in funnel traps, rocket nets, and drop nets, respectively, in New Mexico and Texas, to assess the effects of capture technique on injury and survival of the species. We monitored radiotagged, injured lesser prairie-chickens 7–65 d postcapture to assess survival rates of injured individuals. Injuries occurred disproportionately among trap type, injury type, and sex. The predominant injuries were superficial cuts to the extremities of males captured in walk-in funnel traps. However, we observed no mortalities due to trapping, postcapture survival rates of injured birds did not vary across trap types, and the daily survival probability of an injured and uninjured bird was ≥99%. Frequency and intensity of injuries in walk-in funnel traps are due to the passive nature of these traps (researcher cannot select specific individuals for capture) and incidental capture of individuals not needed for research. Comparatively, rocket nets and drop nets allow observers to target birds for capture and require immediate removal of captured individuals from the trap. Based on our results, trap injuries would be reduced if researchers monitor and immediately remove birds from walk-in funnels before they injure themselves; move traps to target specific birds and reduce recaptures; limit the number of consecutive trapping days on a lek; and use proper netting techniques that incorporate quick, efficient, trained handling procedures.

Journal of Fish and Wildlife Management↗
USGS2012

Techniques for telemetry transmitter attachment and evaluation of transmitter effects on fish performance: Chapter 4

One assumption of nearly every biotelemetry study is that the tagged animals are representative of the untagged population. That is, that the processes by which study animals are captured, handled, and tagged, as well as the act of carrying a transmitter, will have minimal effect on their behavior and performance. This assumption, commonly stated as a lack of transmitter effects, must be valid if telemetry studies are to describe accurately the movements and behavior of an entire population of interest, rather than only of a subset of that population. Considering the sequence of events necessary to implement telemetry studies (i.e., collection, handling, transmitter attachment), as well as the intrusive nature of many transmitter attachment techniques, it is likely that there will be some effect on the study animals. These potential impacts can range from mild to severe, from transitory to permanent, and may be manifest immediately or not for several days to weeks after tagging. Direct physical impacts can include elevated stress levels, injury, or even death (Knights and Lasee 1996; Jepsen et al. 2001; Lacroix et al. 2004). Interrupted integrity of the scales, mucus, or skin can place fish at increased risk of infection (Mellas and Haynes 1985; Swanberg et al. 1999; Bauer et al. 2005; Harms 2005). Effects on fish behavior include altered buoyancy compensation ability (Gallepp and Magnuson 1972; Fried et al. 1976), reduced swimming performance (McCleave and Stred 1975; Counihan and Frost 1999; Makiguchi and Ueda 2009), reduced feeding, or changes in dominance status (Greenstreet and Morgan 1989; Armstrong and Rawlings 1993; Welch et al. 2007). Changes in behavior such as these can affect a fish’s growth, rate of maturation or migration, or increase its vulnerability to predation. At some level, these transmitter effects will be present in nearly every study using telemetry and if substantial, they can violate the critical assumption that tagged fish are representative of the untagged population.

Book chapter↗
USGS2026

Is "weediness" and "invasiveness" of weeds a function of the plant microbiome?

Over the past several decades, the extent to which microbes enhance plant development and health has become clearer; however, this has not been explored in terms of the aggressiveness and hardiness of weedy plants. In this review, we explore the hypothesis that many features of weeds and invasive plants are related to the activities of plant microbiomes. Microbes contribute to weed growth, fecundity, and fitness. They also play roles in soils, and in plants as endophytes, where they modulate plant development and protect the host from pathogens, insects, animals, and abiotic stresses. In addition, the adaptability and hardiness of weeds partly stem from the effects of endophytes on plant gene expression and genetic diversity. Weed control often involves multiple applications of herbicides or other treatments that can be costly and destructive. Weed and invasive plant control for agriculture and environment goes beyond monetary costs to negative impacts on people, animals and environment. However, with a more complete knowledge of the roles played by microbes, their symbiotic interactions may be altered to diminish aggressive traits less expensively and with fewer non target effects on environmental, human and animal health.

Grass Research↗
USGS2001

Susceptibility of the Siberian polecat to subcutaneous and oral Yersinia pestis exposure

To determine if the Siberian polecat ( Mustela eversmannii ) represents a suitable model for the study of plague pathogenesis and prevention in the black-footed ferret ( Mustela nigripes ), polecats were exposed to 10 3 , 10 7 , or 10 10 Yersinia pestis organisms by subcutaneous injection; an additional group was exposed to Y. pestis via ingestion of a plague-killed mouse. Plague killed 88% of polecats exposed to Y. pestis (71% mortality in the 10 3 group, 100% mortality in the 10 7 and 10 10 groups, and 83% mortality in the mouse-fed group). Within the challenged group, mean day of death post-challenge ranged from 3.6 to 7.6 days; all polecats died on or before day 12 post-challenge. Animals receiving the lowest parenteral dose survived significantly longer than those receiving higher parenteral doses. Within challenged animals, mean survival time was lower in those presenting with significant weight loss by day 3, lethargy, and low fecal output; time to onset of lethargy and other signs was also related to risk of dying and/or plague dose. Six polecats developed serum antibody titers to the Y. pestis F1 protein. Three seropositive polecats survived the initial challenge and a subsequent exposure to a plague-killed mouse, while two seropositive animals later died. This study confirms that the Siberian polecat is susceptible to plague and suggests that this species will offer an appropriate surrogate for black-footed ferrets in future plague studies and related vaccine trials.

Journal of Wildlife Diseases↗
USGS2005

Attempts to identify the source of avian vacuolar myelinopathy for waterbirds

Attempts were made to reproduce avian vacuolar myelinopathy (AVM) in a number of test animals in order to determine the source of the causative agent for birds and to find a suitable animal model for future studies. Submerged vegetation, plankton, invertebrates, forage fish, and sediments were collected from three lakes with ongoing outbreaks of AVM and fed to American coots ( Fulica americana ), mallard ducks and ducklings ( Anas platyrhynchos ), quail ( Coturnix japonica ), and laboratory mice either via gavage or ad libitum. Tissues from AVM-affected coots with brain lesions were fed to ducklings, kestrels ( Falco sparverius ), and American crows ( Corvus brachyrhynchos ). Two mallards that ingested one sample of Hydrilla verticillata along with any biotic or abiotic material associated with its external surface developed brain lesions consistent with AVM, although neither of the ducks had clinical signs of disease. Ingestion of numerous other samples of Hydrilla from the AVM affected lakes and a lake with no prior history of AVM, other materials (sediments, algae, fish, invertebrates, and water from affected lakes), or tissues from AVM-affected birds did not produce either clinical signs or brain lesions in any of the other test animals in our studies. These results suggest that waterbirds are most likely exposed to the causative agent of AVM while feeding on aquatic vegetation, but we do not believe the vegetation itself is the agent. We hypothesize that the causative agent of AVM might either be accumulated by aquatic vegetation, such as Hydrilla , or associated with biotic or abiotic material on its external surfaces. In support of that hypothesis, two coots that ingested Hydrilla sampled from a lake with an ongoing AVM outbreak in wild birds developed neurologic signs within 9 days (ataxia, limb weakness, and incoordination), and one of two coots that ingested Hydrilla collected from the same site 13 days later became sick and died within 38 days. None of these three sick coots had definitive brain lesions consistent with AVM by light microscopy, but they had no gross or histologic lesions in other tissues. It is unclear if these birds died of AVM. Perhaps they did not ingest a dose sufficient to produce brain lesions or the lesions were ultrastructural. Alternatively, it is possible that a separate neurotoxic agent is responsible for the morbidity and mortality observed in these coots.

Journal of Wildlife Diseases↗
USGS2008

Vaccination with F1-V fusion protein protects black-footed ferrets (Mustela nigripes) against plague upon oral challenge with Yersinia pestis

Previous studies have established that vaccination of black-footed ferrets ( Mustela nigripes ) with F1-V fusion protein by subcutaneous (SC) injection protects the animals against plague upon injection of the bacterium Yersinia pestis . This study demonstrates that the F1-V antigen can also protect ferrets against plague contracted via ingestion of a Y. pestis -infected mouse, a probable route for natural infection. Eight black-footed ferret kits were vaccinated with F1-V protein by SC injection at approximately 60 days-of-age. A booster vaccination was administered 3 mo later via SC injection. Four additional ferret kits received placebos. The animals were challenged 6 wk after the boost by feeding each one a Y. pestis -infected mouse. All eight vaccinates survived challenge, while the four controls succumbed to plague within 3 days after exposure. To determine the duration of antibody postvaccination, 18 additional black-footed ferret kits were vaccinated and boosted with F1-V by SC injection at 60 and 120 days-of-age. High titers to both F1 and V (mean reciprocal titers of 18,552 and 99,862, respectively) were found in all vaccinates up to 2 yr postvaccination, whereas seven control animals remained antibody negative throughout the same time period.

Journal of Wildlife Diseases↗
USGS2011

Seroepidemiology of TmPV1 infection in captive and wild Florida manatees (Trichechus manatus latirostris)

In 1997, cutaneous papillomatosis caused by Florida manatee ( Trichechus manatus latirostris [Tm]) papillomavirus 1 (TmPV1) was detected in seven captive manatees at the Homosassa Springs Wildlife State Park, Florida, USA, and, subsequently, in two wild manatees from the adjacent Homosassa River. Since then, papillomatosis has been reported in captive manatees housed in other locations, but not in wild animals. To determine TmPV1 antibody prevalence in captive and wild manatees sampled at various locations throughout Florida coastal regions, virus-like particles, composed of the L1 capsid protein of TmPV1, were generated with a baculovirus expression system and used to measure anti-TmPV1 antibodies in an enzyme-linked immunosorbent assay. Serologic analysis of 156 manatees revealed a TmPV1 antibody prevalence of 26.3%, with no significant difference between captive ( n =39) and wild ( n =117) manatees (28.2% and 25.6%, respectively). No antibody-positive wild animal showed PV-induced cutaneous lesions, whereas papillomatosis was observed in 72.7% of antibody-positive captive manatees. Our data indicate that Florida manatees living in the wild are naturally infected by TmPV1 but rarely show TmPV1-induced papillomatosis. Hence, it appears that the wild population would not be harmed in a case of contact with captive animals without visible lesions and productive infections, which could be thus released into the wild.

Florida↗
USGS2014

Evaluation of monkeypox virus infection of prairie dogs (Cynomys ludovicianus) using in vivo bioluminescent imaging

Monkeypox (MPX) is a re-emerging zoonotic disease that is endemic in Central and West Africa, where it can cause a smallpox-like disease in humans. Despite many epidemiologic and field investigations of MPX, no definitive reservoir species has been identified. Using recombinant viruses expressing the firefly luciferase (luc) gene, we previously demonstrated the suitability of in vivo bioluminescent imaging (BLI) to study the pathogenesis of MPX in animal models. Here, we evaluated BLI as a novel approach for tracking MPX virus infection in black-tailed prairie dogs (Cynomys ludovicianus). Prairie dogs were affected during a multistate outbreak of MPX in the US in 2003 and have since been used as an animal model of this disease. Our BLI results were compared with PCR and virus isolation from tissues collected postmortem. Virus was easily detected and quantified in skin and superficial tissues by BLI before and during clinical phases, as well as in subclinical secondary cases, but was not reliably detected in deep tissues such as the lung. Although there are limitations to viral detection in larger wild rodent species, BLI can enhance the use of prairie dogs as an animal model of MPX and can be used for the study of infection, disease progression, and transmission in potential wild rodent reservoirs.

South Dakota↗
USGS2024

Treat yourself: Pilot testing a new method to treat mange in wild carnivores

Mange is a skin disease caused by mites that parasitize an animal's skin, often yielding inflamed immune responses and hair loss. At a population level, mange may reduce survival and cause population declines. Many forms of mange can be treated quite effectively when an animal is in hand; however, this is not often feasible for many free-ranging wildlife populations. Some animals, particularly territorial carnivores, will rub or roll to scent mark and transmit information about their presence to other individuals. We posited that rub stations comprised, in part, of anthelmintic medication and foreign scents that induce rubbing could be used to remotely treat mange in the wild. We deployed 39 rub stations containing lure and dye in Santa Monica Mountains National Recreation Area, Southern California, USA, October–November 2022. Carnivores rubbed or rolled at .97% of rub stations, with coyotes ( Canis latrans ), gray foxes ( Urocyon cinereoargenteus ), and bobcats ( Lynx rufus ) being the most abundant species. Time to first rub or roll was generally <1 wk. Several sympatric species (e.g., mule deer, Odocoileus hemionus ) were detected at rub stations but did not rub. Our pilot test provides strong evidence that treating mange in wild carnivores may be possible using the remote medicinal rub stations we describe. Future efforts to add medicine to rub stations and monitor for a change in mange prevalence are a logical next step.

Journal of Wildlife Diseases↗
USGS2005

White-tailed deer ecology and management on Fire Island

Deer populations have grown dramatically on Fire Island National Seashore (FIlS) since 1983. Trend data reveal a dichotomy in deer dynamics. In the eastern half of the island, deer density appears to have stabilized between 25-35 deer/km2. In the western half of the island, deer densities are 3-4 times as high in residential communities. Concomitant with that increase has been a general decline in physical stature of some animals, visible impacts on island vegetation, especially in the Sunken Forest, and a perceived increase in the frequency of human and deer interactions. Intensive research on FIlS has shown that deer occupy relatively predictable home ranges throughout the year, but can and do move up and down the island. Impacts of deer on vegetation are most dramatic in the Sunken Forest. Most obvious are the effects of browsing on the herb layer of the Sunken Forest. The least obvious, but perhaps more significant impact is the stark lack of regeneration of canopy tree species since about 1970, which coincides with the initiation of the deer population irruption. A number of herbs and shrubs have been greatly reduced in the understory, and their propagules from the soil. Deer do not readily transmit the bacterium that causes Lyme disease to other organisms, but deer are important hosts for adult ticks which underscores their importance in the transmission pathway of the disease to humans. Deer on FIlS, while occasionally docile, are still wild animals and should be treated as such. Some animals are relatively unafraid of humans due to the absence of predation and a lack of harassment. This in turn has contributed to a longstanding tradition of feeding deer by many residents and visitors, particularly in western portions of the island. Feeding affects both the behavior and population dynamics of deer inhabiting Fire Island. Recent efforts to reduce deer feeding by visitors and residents have been very effective. Ongoing experiments with Porcine Zona Pellucida immunocontraception demonstrate some promise of this technology as a population management tool.. Success appears to be linked directly to factors affecting access to deer, which vary considerably among treatment locations. Continued high National Park Service visibility among communities in the form of interpretive programs, extension and outreach activities, and continued support of research and monitoring of deer and their effects on island biota are keys to successful resolution of persistent issues.

Technical Report↗
USGS1969

Tissue residues of dieldrin in relation to mortality in birds and mammals

An experiment was performed with Coturnix to learn what residue levels were indicative of death from dieldrin poisoning. Birds were fed diets containing 250, 50, 10, and 2 ppm dieldrin for periods up to 158 days. The dieldrin was 95% pure HEOD, which is 1,2,3,4,10,10-hexachloro-6, 7.epoxy. l,4,4a,5,6,7,8,8a-octahydro-l,4-endo,exo-5,8- dimethanonaphthalene. When half of a group was dead, the other half was sacrificed for comparison of residues in dead and survivors. Dosage levels controlled time to death, but did not control residue levels in the dead. Residues in liver and carcass proved to be misleading and complicated by changes in lipid content. Brain residues correlated well with death although residues in dead and survivors overlapped. Brain residues of animals killed by dieldrin in the field and in other experiments are listed. Data agree in general for several species of birds and mammals. There is evidence, however, for species differences in average lethal brain residues. It is concluded that brain residues of 4 or 5 ppm (wet weight) or higher indicate that the animal was in the known danger zone and may have died from dieldrin. Brain residues averaged lower in wild than in experimental animals. Possible explanations include species differences, more stress and exertion in the wild, and overrepresentation in the field series of individuals that will die with low but lethal brain residues. The latter is supported by the fact that the first Coturnix to die in each sex and treatment group had the lowest brain residue of its group. Birds receiving 2 ppm dieldrin, and some receiving 10 ppm, were able to maintain low brain residues throughout the experiment. However, birds of the 10 ppm group could withstand little stress and mobilization of toxicant, for a few micrograms in the brain were lethal and bodies contained hundreds or thousands of micrograms.

Book chapter↗
USGS2007

Assessment of Alternative Substrates for Culturing Lumbriculus variegatus

The freshwater oligochaete, Lumbriculus variegatus, is tank-cultured to provide organisms for aquatic-habitat assessments, regeneration research and as a clean source of live food for aquarium fishes. Shredded paper is the typical substrate in cultures used to rear L. variegatus for these purposes. However, the effort needed to separate large numbers from decomposing paper can be prohibitive. Burlap and nylon mesh material were compared to paper as potential alternatives that could reduce this effort. Oligochaete production and the amount of time needed to separate animals from substrate were compared for eight weeks among experimental cultures containing burlap, nylon mesh and paper. Cultures with paper substrate increased in number and weight two to three times faster than those with burlap or nylon mesh substrates. The time needed to separate animals from substrate was initially two to three times longer with paper substrate than with burlap or nylon mesh substrates, but this difference increased to between 10 and 40 times longer after six weeks as the paper substrate decomposed. Feeding rates varied by treatment and were based on average wet weight at the time of water replacement. Elevated ammonia and nitrite concentrations resulting from excess food may have reduced production in nylon mesh treatments and was lethal in paper treatments during the final phases of the study. The type of substrate recommended may depend on the desired production rate of oligochaetes, space available for cultures and the amount of effort available for substrate renewal and separating the animals from the cultures.

Book chapter↗
USGS2009

A traditional and a less-invasive robust design: choices in optimizing effort allocation for seabird population studies

For many animal populations, one or more life stages are not accessible to sampling, and therefore an unobservable state is created. For colonially-breeding populations, this unobservable state could represent the subset of adult breeders that have foregone breeding in a given year. This situation applies to many seabird populations, notably albatrosses, where skipped breeders are either absent from the colony, or are present but difficult to capture or correctly assign to breeding state. Kendall et al. have proposed design strategies for investigations of seabird demography where such temporary emigration occurs, suggesting the use of the robust design to permit the estimation of time-dependent parameters and to increase the precision of estimates from multi-state models. A traditional robust design, where animals are subject to capture multiple times in a sampling season, is feasible in many cases. However, due to concerns that multiple captures per season could cause undue disturbance to animals, Kendall et al. developed a less-invasive robust design (LIRD), where initial captures are followed by an assessment of the ratio of marked-to-unmarked birds in the population or sampled plot. This approach has recently been applied in the Northwestern Hawaiian Islands to populations of Laysan (Phoebastria immutabilis) and black-footed (P. nigripes) albatrosses. In this paper, we outline the LIRD and its application to seabird population studies. We then describe an approach to determining optimal allocation of sampling effort in which we consider a non-robust design option (nRD), and variations of both the traditional robust design (RD), and the LIRD. Variations we considered included the number of secondary sampling occasions for the RD and the amount of total effort allocated to the marked-to-unmarked ratio assessment for the LIRD. We used simulations, informed by early data from the Hawaiian study, to address optimal study design for our example cases. We found that the LIRD performed as well or nearly as well as certain variations of the RD in terms of root mean square error, especially when relatively little of the total effort was allocated to the assessment of the marked-to-unmarked ratio versus to initial captures. For the RD, we found no clear benefit of using 2, 4, or 6 secondary sampling occasions per year, though this result will depend on the relative effort costs of captures versus recaptures and on the length of the study. We also found that field-readable bands, which may be affixed to birds in addition to standard metal bands, will be beneficial in longer-term studies of albatrosses in the Northwestern Hawaiian Islands. Field-readable bands reduce the effort cost of recapturing individuals, and in the long-term this cost reduction can offset the additional effort expended in affixing the bands. Finally, our approach to determining optimal study design can be generally applied by researchers, with little seed data, to design their studies at the outset.

Book chapter↗
USGS2006

Assessing tiger population dynamics using photographic capture-recapture sampling

Although wide-ranging, elusive, large carnivore species, such as the tiger, are of scientific and conservation interest, rigorous inferences about their population dynamics are scarce because of methodological problems of sampling populations at the required spatial and temporal scales. We report the application of a rigorous, noninvasive method for assessing tiger population dynamics to test model-based predictions about population viability. We obtained photographic capture histories for 74 individual tigers during a nine-year study involving 5725 trap-nights of effort. These data were modeled under a likelihood-based, ?robust design? capture?recapture analytic framework. We explicitly modeled and estimated ecological parameters such as time-specific abundance, density, survival, recruitment, temporary emigration, and transience, using models that incorporated effects of factors such as individual heterogeneity, trap-response, and time on probabilities of photo-capturing tigers. The model estimated a random temporary emigration parameter of =K' =Y' 0.10 ? 0.069 (values are estimated mean ? SE). When scaled to an annual basis, tiger survival rates were estimated at S = 0.77 ? 0.051, and the estimated probability that a newly caught animal was a transient was = 0.18 ? 0.11. During the period when the sampled area was of constant size, the estimated population size Nt varied from 17 ? 1.7 to 31 ? 2.1 tigers, with a geometric mean rate of annual population change estimated as = 1.03 ? 0.020, representing a 3% annual increase. The estimated recruitment of new animals, Bt, varied from 0 ? 3.0 to 14 ? 2.9 tigers. Population density estimates, D, ranged from 7.33 ? 0.8 tigers/100 km2 to 21.73 ? 1.7 tigers/100 km2 during the study. Thus, despite substantial annual losses and temporal variation in recruitment, the tiger density remained at relatively high levels in Nagarahole. Our results are consistent with the hypothesis that protected wild tiger populations can remain healthy despite heavy mortalities because of their inherently high reproductive potential. The ability to model the entire photographic capture history data set and incorporate reduced-parameter models led to estimates of mean annual population change that were sufficiently precise to be useful. This efficient, noninvasive sampling approach can be used to rigorously investigate the population dynamics of tigers and other elusive, rare, wide-ranging animal species in which individuals can be identified from photographs or other means.

Ecology↗