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USGS2015

Monitoring digestibility of forages for herbivores: a new application for an old approach

Ruminant populations are often limited by how well individuals are able to acquire nutrients for growth, maintenance, and reproduction. Nutrient supply to the animal is dictated by the concentration of nutrients in feeds and the efficiency of digesting those nutrients (i.e., digestibility). Many different methods have been used to measure digestibility of forages for wild herbivores, all of which rely on collecting rumen fluid from animals or incubation within animals. Animal-based methods can provide useful estimates, but the approach is limited by the expense of fistulated animals, wide variation in digestibility among animals, and contamination from endogenous and microbial sources that impairs the estimation of nutrient digestibility. We tested an in vitro method using a two-stage procedure using purified enzymes. The first stage, a 6 h acid–pepsin treatment, was followed by a combined 72 h amylase–cellulase or amylase–Viscozyme treatment. We then validated our estimates using in sacco and in vivo methods to digest samples of the same forages. In vitro estimates of dry matter (DM) digestibility were correlated with estimates of in sacco and in vivo DM digestibility (both P < 0.01). The in vitro procedure using Viscozyme ( r 2 = 0.77) was more precise than the in vitro procedure using cellulase ( r 2 = 0.59). Both procedures can be used to predict in sacco digestibility after correcting for the biases of each method. We used the in vitro method to measure digestibility of nitrogen (N; 0.07–0.95 g/g), which declined to zero as total N content declined below 0.03–0.06 g/g of DM. The in vitro method is well suited to monitoring forage quality over multiple years because it is reproducible, can be used with minimal investment by other laboratories without animal facilities, and can measure digestibility of individual nutrients such as N.

Canadian Journal of Zoology↗

USGS2016

Physiology of the invasive apple snail Pomacea maculata : tolerance to low temperatures

Apple snails of the genus Pomacea native to South America have invaded and become established in Europe, Asia, and the United States. Both the channeled apple snail Pomacea canaliculata and the island apple snail Pomacea maculata have been reported in the United States. The two species are difficult to distinguish using morphological characters, leading to uncertainty about the identity of the animals from populations in the United States. Because the snails are subtropical, their tolerance of low temperatures is a critical factor in limiting the spread of the animals from present localities along the coast of the Gulf of Mexico to more northern areas. The tolerance of P. maculata collected in Louisiana to temperatures as low as 0°C was examined. There was no mortality among animals maintained in water at temperatures of 20°C or 15°C for 10 days. Survival of animals during a 10-day exposure to water at temperatures 10°C and 5°C was 50%. The LD 50 for a 10-day exposure was 7°C. Snails did not survive more than 5 days in liquid water at 0°C. Ammonia excretion by animals in temperatures of 20°C and 15°C was comparable to values reported for freshwater gastropods; at very low temperatures, excretion of ammonia was decreased. There was no difference in the mean values of the osmolality of the hemolymph of animals exposed to 20°C, 15°C and 10°C for 10 days. Sequencing of mitochondrial cytochrome oxidase 1 identified the animals in the Louisiana population used in this study as P. maculata.

Louisana↗

USGS2025

Wake Atoll vessel movement biosecurity program efficacy

Executive Summary The purpose of this Wake Atoll Vessel Movement Biosecurity Program Efficacy document is to provide the United States Air Force (USAF) with an unbiased review of the current (2015; hereafter referred to as the 2015 Biosecurity Plan) biosecurity plan for the military base Wake Island Airfield (WIA) on Wake Atoll (hereafter Wake). Periodic reviews are an integral step for evaluating plan efficacy and updating plans with new information for improving plan effectiveness. The U.S. Geological Survey (USGS) acted as an external expert to provide the first unbiased assessment of the program and observe how it was being implemented. The USAF 2015 Wake Island Biosecurity Management Plan goes beyond sea vessel and container biosecurity; however, those aspects were not included in this evaluation. We used several methods for a quality assurance evaluation of the 2015 sea vessel and shipping container biosecurity program specified in the Biosecurity Plan. Our evaluation included real-time observations in Hawai`i and at Wake. We surveyed cargo staging areas and empty shipping containers before supply shipment and the containers, barge, and marina at Wake after shipment. We used various detection tools and techniques (for example, visual encounter surveys, glue boards, chew cards, camera traps, and so on). We carried out an insect mortality experiment trial using one of the required shipping container biosecurity tools (dichlorvos impregnated pest strips). We also included a table-top review of documentation (largely the 2015 Biosecurity Plan) with respect to our observations to provide an assessment of how well the Biosecurity Plan protocols were carried out and how well they serve their intended purpose. We observed biosecurity concerns in each focal area and stage of cargo handling (before and after barge movement) across all surveys of containers, flat racks, break bulk, warehouses, and dock areas. Using visual inspections, we recorded biosecurity concerns for every empty container we inspected before it was to be stuffed with cargo. Most containers had structural integrity issues (such as holes and damaged floorboards) and sanitation concerns, including live animals and plant matter or seeds. About one third of the containers had mold and a few had wet floorboards or standing water. We detected live animals on the break bulk, and flat racks were in poor condition. Next, we inspected cargo staging areas and noted extensive permeability of the building where cargo was staged for the 2018 resupply shipment and the building that had typically been used. We included the adjacent dock area used for staging break bulk, shipping containers and mooring the barge. We detected more than 5,000 individuals of 105 species. We also detected seeds in each location and scattered vegetation in the dock area, including growing in from the area outside separated by a chain link fence. During surveys at Wake, we observed that 100 percent of the shipping containers, including all containers sent with required biosecurity tools, had live animals. The barge had only one unsecured snap trap for intercepting rodents aboard, we saw areas with fairly deep layers of dirt (or soil; we did not examine it to determine its properties), and there was plant matter with seed heads on the barge gangway that could easily be transported onto the barge. There was also only one snap trap station that was improperly placed on the dock. We also observed piled wood and vegetation nearby that could provide refuge to potential stowaway animals escaping. Combined, surveys of the containers, staging areas, barges, and receiving area in Hawai`i and at Wake resulted in detection of more than 9,000 individuals of 131 animal species; nearly 4,000 individuals of 62 species were detected in surveys of containers once they had arrived at Wake. None of the species identified are known to be native to Wake. Our preliminary risk analysis of all species detected included eight species that we scored as high risk of potentially negative effects to biodiversity, infrastructure, or human health should they arrive at Wake and become established. Six of these species were only recorded using tools not clearly required by the Biosecurity Plan or being used to implement the plan. We observed that the required biosecurity tools intended to intercept animals in the cargo staging area did not target the suite nor number of species present. Our analysis also indicated the required biosecurity tools intended to intercept animals in shipping containers were inadequate to handle the volume of organisms that were in the containers. The insect mortality trial experiment showed the pest strips were highly effective for only one of the three species tested, leaving uncertainty about how effective they are across the suite of potential species stowing away in cargo and containers. Base Operating Support (BOS) did not carry out all Biosecurity Plan actions, but we also noted the document uses terminology such as “recommendation” as opposed to “requirement” which may lead contractors to consider those actions as optional. However, USAF provided evidence of BOS training and follow up; this included detailed identification of specific requirements for some of the biosecurity actions that we did not observe being carried out. The 2015 Biosecurity Plan contains critical and useful components that seem to be well carried out. However, we also saw discrepancies, weaknesses, or both across methods and protocols currently used for Wake Atoll biosecurity. We observed shortcomings at each stage of our survey as well as in the plan as written, and we suggest general modifications to the Biosecurity Plan for consideration to potentially strengthen biosecurity overall. Prevention is the most efficient and cost-effective biosecurity measure. Based on our findings, we see possible solutions to improve existing preventative biosecurity efforts and reduce potential incursion at Wake. These potential solutions include creating and implementing the following: Minimum cargo staging area sanitation and permeability standards, Minimum shipping container integrity and sanitation standards, Stand-alone inspection protocols, Inspection checklists, Monitoring protocols, Accountability reporting, Horizon scanning for prioritizing and targeting species of highest concern, Expansion of educational materials and outreach, Schedules for biosecurity plan reviews and updates Management of invasive species enhances capability to protect human health and the environment as well as to advance mission accomplishment. Biosecurity plans are an integral component for addressing invasive species. Periodic evaluation of the efficacy of these plans is useful for identifying elements that are working well and for illuminating those that can be improved. Evaluations encourage consideration of new tools and adaptation of processes to achieve better outcomes and accommodate potential future threats more efficiently and more cost effectively.

Open-File Report↗

USGS2012

Preliminary assessment of sources of nitrogen in groundwater at a biosolids-application area near Deer Trail

Concentrations of dissolved nitrite plus nitrate increased fairly steadily in samples from four shallow groundwater monitoring wells after biosolids applications to nonirrigated farmland began in 1993. The U.S. Geological Survey began a preliminary assessment of sources of nitrogen in shallow groundwater at part of the biosolids-application area near Deer Trail, Colorado, in 2005 in cooperation with the Metro Wastewater Reclamation District. Possible nitrogen sources in the area include biosolids, animal manure, inorganic fertilizer, atmospheric deposition, and geologic materials (bedrock and soil). Biosolids from the Metro Wastewater Reclamation District plant in Denver and biosolids, cow manure, geologic materials (bedrock and soil), and groundwater from the study area were sampled to measure nitrogen content and nitrogen isotopic compositions of nitrate or total nitrogen. Biosolids also were leached, and the leachates were analyzed for nitrogen content and other concentrations. Geologic materials from the study area also were sampled to determine mineralogy. Estimates of nitrogen contributed from inorganic fertilizer and atmospheric deposition were calculated from other published reports. The nitrogen information from the study indicates that each of the sources contain sufficient nitrogen to potentially affect groundwater nitrate concentrations. Natural processes can transform the nitrogen in any of the sources to nitrate in the groundwater. Load calculations indicate that animal manure, inorganic fertilizer, or atmospheric deposition could have contributed the largest nitrogen load to the study area in the 13 years before biosolids applications began, but biosolids likely contributed the largest nitrogen load to the study area in the 13 years after biosolids applications began. Various approaches provided insights into sources of nitrate in the groundwater samples from 2005. The isotopic data indicate that, of the source materials considered, biosolids and (or) animal manure were the most likely sources of nitrate in the wells at the time of sampling (2005), and that inorganic fertilizer, atmospheric deposition, and geologic materials were not substantial sources of nitrate in the wells in 2005. The large total nitrogen content of the biosolids and animal-manure samples and biosolids leachates also indicates that the biosolids and animal manure had potential to leach nitrogen and produce large dissolved nitrate concentrations in groundwater. The available data, however, could not be used to distinguish between biosolids or manure as the dominant source of nitrate in the groundwater because the nitrogen isotopic composition of the two materials is similar. Major-ion data also could not be used to distinguish between biosolids or manure as the dominant source of nitrate in the groundwater because the major-ion composition (as well as the isotopic composition) of the two materials is similar. Without additional data, chloride/bromide mass ratios do not necessarily support or refute the hypothesis that biosolids and (or) animal manure were the primary sources of nitrate in water from the study-area wells in 2005. Concentrations of water-extractable nitrate in the soil indicate that biosolids could be an important source of nitrate in the groundwater recharge. Nitrogen inventories in the soil beneath biosolids-application areas and the nitrogen-input estimates for the study area both support the comparisons of isotopic composition, which indicate that some type of human waste (such as biosolids) and (or) animal manure was the source of nitrate in groundwater sampled from the wells in 2005. The nitrogen-load estimates considered with the nitrogen isotopic data and the soil-nitrogen inventories indicate that biosolids applications likely are a major source of nitrogen to the shallow groundwater at these monitoring wells.

Colorado↗

USGS2021

Drivers of site fidelity in ungulates

While the tendency to return to previously visited locations—termed ‘site fidelity’—is common in animals, the cause of this behaviour is not well understood. One hypothesis is that site fidelity is shaped by an animal's environment, such that animals living in landscapes with predictable resources have stronger site fidelity. Site fidelity may also be conditional on the success of animals’ recent visits to that location, and it may become stronger with age as the animal accumulates experience in their landscape. Finally, differences between species, such as the way memory shapes site attractiveness, may interact with environmental drivers to modulate the strength of site fidelity. We compared inter-year site fidelity in 669 individuals across eight ungulate species fitted with GPS collars and occupying a range of environmental conditions in North America and Africa. We used a distance-based index of site fidelity and tested hypothesized drivers of site fidelity using linear mixed effects models, while accounting for variation in annual range size. Mule deer Odocoileus hemionus and moose Alces alces exhibited relatively strong site fidelity, while wildebeest Connochaetes taurinus and barren-ground caribou Rangifer tarandus granti had relatively weak fidelity. Site fidelity was strongest in predictable landscapes where vegetative greening occurred at regular intervals over time (i.e. high temporal contingency). Species differed in their response to spatial heterogeneity in greenness (i.e. spatial constancy). Site fidelity varied seasonally in some species, but remained constant over time in others. Elk employed a ‘win-stay, lose-switch’ strategy, in which successful resource tracking in the springtime resulted in strong site fidelity the following spring. Site fidelity did not vary with age in any species tested. Our results provide support for the environmental hypothesis, particularly that regularity in vegetative phenology shapes the strength of site fidelity at the inter-annual scale. Large unexplained differences in site fidelity suggest that other factors, possibly species-specific differences in attraction to known sites, contribute to variation in the expression of this behaviour. Understanding drivers of variation in site fidelity across groups of organisms living in different environments provides important behavioural context for predicting how animals will respond to environmental change.

Journal of Animal Ecology↗

USGS2016

The extra mile: Ungulate migration distance alters the use of seasonal range and exposure to anthropogenic risk

Partial migration occurs across a variety of taxa and has important ecological and evolutionary consequences. Among ungulates, studies of partially migratory populations have allowed researchers to compare and contrast performance metrics of migrants versus residents and examine how environmental factors influence the relative abundance of each. Such studies tend to characterize animals discretely as either migratory or resident, but we suggest that variable migration distances within migratory herds are an important and overlooked form of population structure, with potential consequences for animal fitness. We examined whether the variation in individual migration distances (20–264 km) within a single wintering population of mule deer ( Odocoileus hemionus ) was associated with several critical behavioral attributes of migration, including timing of migration, time allocation to seasonal ranges, and exposure to anthropogenic mortality risks. Both the timing of migration and the amount of time animals allocated to seasonal ranges varied with migration distance. Animals migrating long distances (150–250 km) initiated spring migration more than three weeks before than those migrating moderate (50–150 km) or short distances (<50 km). Across an entire year, long-distance migrants spent approximately 100 more days migrating compared to moderate- and short-distance migrants. Relatedly, winter residency of long-distance migrants was 71 d fewer than for animals migrating shorter distances. Exposure to anthropogenic mortality factors, including highways and fences, was high for long-distance migrants, whereas vulnerability to harvest was high for short- and moderate-distance migrants. By reducing the amount of time that animals spend on winter range, long-distance migration may alleviate intraspecific competition for limited forage and effectively increase carrying capacity. Clear differences in winter residency, migration duration, and risk of anthropogenic mortality among short-, moderate-, and long-distance migrants suggest fitness trade-offs may exist among migratory segments of the population. Future studies of partial migration may benefit from expanding comparisons of residents and migrants, to consider how variable migration distances of migrants may influence the costs and benefits of migration.

Wyoming↗

USGS2002

Behavioral effects of environmental enrichment on harbor seals (Phoca vitulina concolor) and gray seals (Halichoerus grypus)

Zoos and aquariums have been incorporating environmental enrichment into their animal care programs for the past 30 years to increase mental stimulation and promote natural behaviors. However, most attempts to document the effects of enrichment on animal behavior have focused on terrestrial mammals. Staff at the National Aquarium in Baltimore conducted an investigation of the behavioral effects of enrichment on the seven harbor seals and two gray seals housed in the aquarium's outdoor seal exhibit. We expected that enrichment would change the amount of time the animals spent engaged in specific behaviors. The behaviors recorded were: resting in water, resting hauled out, maintenance, breeding display, breeding behavior, aggression, pattern swimming, random swimming, exploration, and out of sight. Activity levels (random swimming and exploration) were expected to increase, while stereotypic behaviors (pattern swimming) were expected to decrease. The frequency and duration of behaviors were documented for 90 hr in both the control phase (without enrichment) and the experimental phase (with enrichment). Statistically significant differences ( P <0.05) in the time spent in pattern swimming, random swimming, exploration, and out of sight were observed between the two phases. With enrichment, pattern swimming and out of sight decreased, while random swimming and exploration behavior increased. These findings demonstrate that enrichment can promote behaviors (random swimming and exploration) that are likely to be normal for phocids in the wild, and that may contribute to the behavioral complexity of these seals in captivity.

Zoo Biology↗

USGS2026

Ecological diffusion models are still useful in ecology

Context Connecting animal movement across scales—both among spatial scales and between individual and population level processes—is a central theme in ecology, including the sub-fields of movement and landscape ecology. However, most modeling frameworks operate at either the individual (Lagrangian) or population (Eulerian) level. Objectives We aimed to review how a partial differential equation (PDE) known as the ecological diffusion equation (EDE) offers connections among the scales of animal movement and how it can be embedded in commonly used statistical frameworks (e.g., hierarchical models) and fit to multiple types of data, such as count, presence-only, presence-absence, and telemetry data. In doing so, we also highlight emerging and promising avenues of research related to statistical EDE models. Methods We present how the EDE is derived from a simple set of first principles, can be used to represent both individual animal movement and spatiotemporal population dynamics, and can be fit to data by being applied in a hierarchical statistical framework. Finally, we review literature on recent applications and advances related to EDE models. Results In presenting the derivation of the EDE and reviewing recent advances and applications of EDE models, we established that the EDE can enable a mechanistic understanding of animal movement across scales, as well as the integration of multiple types of data. We also identified a number of topics where EDE models can be advanced to gain additional ecological insight. Conclusions Ecological diffusion is a process that emerges naturally from first principles governing animal movement and can be used to model both individual and population-level spatiotemporal dynamics. Statistical EDE models are related to other modeling frameworks, such as species distribution models, occupancy models, and step-selection analysis. The flexibility of hierarchical statistical modeling allows combining different types of data collected on movement and population dynamics, and the theoretical underpinnings of the EDE allow it to connect ecological processes occurring at fine and coarse spatial scales, as well as individual animal movement and population dynamics.

Landscape Ecology↗

USGS2006

A global perspective on the use, sales, exposure pathways, occurrence, fate and effects of veterinary antibiotics (VAs) in the environment

Veterinary antibiotics (VAs) are widely used in many countries worldwide to treat disease and protect the health of animals. They are also incorporated into animal feed to improve growth rate and feed efficiency. As antibiotics are poorly adsorbed in the gut of the animals, the majority is excreted unchanged in faeces and urine. Given that land application of animal waste as a supplement to fertilizer is often a common practice in many countries, there is a growing international concern about the potential impact of antibiotic residues on the environment. Frequent use of antibiotics has also raised concerns about increased antibiotic resistance of microorganisms. We have attempted in this paper to summarize the latest information available in the literature on the use, sales, exposure pathways, environmental occurrence, fate and effects of veterinary antibiotics in animal agriculture. The review has focused on four important groups of antibiotics (tylosin, tetracycline, sulfonamides and, to a lesser extent, bacitracin) giving a background on their chemical nature, fate processes, occurrence, and effects on plants, soil organisms and bacterial community. Recognising the importance and the growing debate, the issue of antibiotic resistance due to the frequent use of antibiotics in food-producing animals is also briefly covered. The final section highlights some unresolved questions and presents a way forward on issues requiring urgent attention.

Chemosphere↗

USGS2002

Wildlife association with human‐altered water sources in semiarid vegetation communities

Based on common use in wildlife management, we hypothesized that human‐constructed water sources influence faunal communities detectably compared to similar habitats that lack water. We examined 20 wildlife water units and 20 paired comparison sites without water from April to August 1992 in semiarid southern New Mexico to assess animal species associations. We sampled sites by using small‐mammal live traps, herpetofaunal and invertebrate pitfall arrays, and 30‐minute time‐area counts. We compared animal species richness and species concordance among water units (rain catchments, earthen tanks, and windmills) and comparison sites in three vegetation communities (mixed scrub, grassland, and pinyon‐juniper). We detected 134 animal taxa during field sampling. Animal species richness did not differ between water units and comparison sites among vegetation communities. Amphibians were found only at water units but occur far from units during seasonal wet periods. Greater numbers of individual small mammals and herpetofauna at water units versus comparison sites likely related to debris and disturbed soil present near water units. Taxa detected at water units and comparison sites were 65% concordant overall; discordant taxa were those rarely detected. Our data implied that definitive effects of artificial water sources on native wildlife species were not detectable. Providing water sources may be a strategic management tool but must be viewed critically regarding effect on distribution of native, feral, and exotic animals. Water units should be developed only when and where clear objectives have been stated, natural water sources have been quantified, commitment exists to ensure continued function, and feral and exotic animals will not benefit to the detriment of native species.

New Mexico↗

USGS2021

A review of algal toxin exposures on reserved federal lands and among trust species in the United States

Associated health effects from algal toxin exposure are a growing concern for human and animal health. Algal toxin poisonings may occur from contact with or consumption of water supplies or from ingestion of contaminated animals. The U.S. Federal Government owns or holds in trust about 259 million hectares of land, in addition to the Trust species obligations. We completed the first comprehensive review of potential toxin-producing algal blooms in surface waters on Federal lands and Trust species exposed to algal toxins. Events were sorted into three tiers based on potentially toxic algae abundance or toxin concentration and related effects on animal morbidity and mortality. At least 11.1% of Federal lands are known to have been affected by algal events, but exposure is likely underreported. The occurrence of potential toxin producers and their toxins (Tier 1) have been documented 337 times, health advisory threshold exceedances (Tier 2) were reported 943 times, and 86 events involved animal sickness or death linked to cyanobacteria or marine toxins (Tier 3). Trust species exposed to cyano- or algal toxins included marine mammals, migratory birds, threatened and endangered species, and species of concern. We report numerous data gaps ranging from potential effects on human health from consuming intoxicated animals to the infrequency of measuring and reporting certain toxins. Improvements to field and laboratory methods, more consistent evaluation of toxin exposure, decreased latency on data analysis, delivery and interpretation will be necessary to improve response and management strategies for protecting human and animal health where issues persist.

Critical Reviews in Environmental Science and Tech↗

USGS2005

Genetic divergence of rabies viruses from bat species of Colorado, USA

Molecular epidemiological studies have linked many cryptic human rabies cases in the United States with exposure to rabies virus (RV) variants associated with insectivorous bats. In Colorado, bats accounted for 98% of all reported animal rabies cases between 1977 and 1996. The genetic divergence of RV was investigated in bat and terrestrial animal specimens that were submitted for rabies diagnosis to the Colorado Department of Public Health and Environment (CDPHE), Colorado, USA. RV isolates from animal specimens across the United States were also included in the analysis. Phylogenetic analyses were performed on partial nucleoprotein (N) gene sequences, which revealed seven principal clades. RV associated with the colonial big brown bat, Eptesicus fuscus , an bats of the genus Myotis were found to segregate into two distinct clades (I and IV). Clade I was harbored by E. fuscus and Myotis species, but was also identified in terrestrial animals such as domestic cats and striped skunks ( Mephitis mephitis ). Clade IV was divided into subclades IVA, IVB, and IVC; IVA was identified in E. fuscus, and Myotis species bats, and also in a fox; subclades IVB and IVC circulated predominantly in E. fuscus . Clade II was formed by big free-tailed bat ( Nyctinomops macrotis ) and striped skunk ( Mephitis mephitis ) samples. Clade III included RVs that are maintained by generally solitary, migratory bats such as the silver-haired bat ( Lasionycteris noctivagans ) and bats of the genus Lasiurus . Big brown bats were found to harbor this RV variant. None of the Colorado specimens segregated with clades V and VII that harbor RVs associated with terrestrial animals. Different species of bats had the same RV variant, indicating active inter-species rabies transmission. In Colorado, animal rabies occurs principally in bats, and the identification of bat RVs in cat, gray fox Urocyon cinereoargenteus ), and striped skunks demonstrated the importance of rabies spillover from bats to domestic and terrestrial wildlife species.

Vector-Borne and Zoonotic Diseases↗

USGS2003

Surgical implantation of transmitters into fish

Although the Animal Welfare Act does not cover poikilotherms, individual institutions and policies and legal requirements other than the Animal Welfare Act (e.g., the US Public Health Service and the Interagency Research Animal Committee's Principles for the Utilization and Care of Vertebrate Animals Used in Testing, Research, and Training) require the review of projects involving fish by institutional animal care and use committees (IACUCs). IACUCs may, however, lack the knowledge and experience to evaluate fish projects judiciously, especially when the projects are in field settings. Surgeries involving implantation of transmitters and other instruments into the coelom, which now comprise a very common research tool in the study of free-ranging fishes, are examples of surgeries that use a broad spectrum of surgical and anesthetic techniques, some of which would not be considered acceptable for similar work on mammals. IACUCs should apply the standards they would expect to be used for surgeries on homeotherms to surgeries on fish. Surgeons should be carefully trained and experienced. Surgical instruments and transmitters should be sterile. Regulations and laws on the use of drugs in animals should be followed, particularly those concerned with anesthetics and antibiotics used on free-ranging fish. Exceptions to surgical procedures should be made only when circumstances are extreme enough to warrant the use of less than optimal procedures.

ILAR Journal↗

USGS1979

Endocrine correlates of reproduction in the wolf. I. Serum progesterone, estradiol and LH during the estrous cycle

The estrous cycle of 10 intact female wolves, aged 8 months-8 years at the initiation of the study, was characterized in terms of vaginal smears, behavioral observations and serum concentrations of estradiol-17β, progesterone and luteinizing hormone (LH) from January through June. No estrous cycles occurred in these animals between June and December. All were housed with male wolves. Two pups and 1 adult remained anestrous during this interval. One pup and 2 adults produced litters between May 4-6. Four adults exhibited endocrine changes similar to those of the pregnant animals but no litters or signs of abortion were observed. The duration of proestrus was 15.7 ± 1.6 days (X ± SEM, n = 6), of estrus 9.0 ± 1.2 days (n = 4) and of the luteal phase 63 ± 2 days (n = 6). The duration of pregnancy was between 60-65 days. The anestrous females (86 blood samples) had 6 progesterone values between 1-2 ng/ml and the remainder below 1 ng/ml. Their estradiol-17β concentrations varied between 5-20 pg/ml. Values for LH varied between 0.1-2 ng/ml, except for 1 value above 15 ng/ml for each of the 2 anestrous pups on 12 January. The 7 estrous animals (260 samples) included 1 pup and 2 adults that delivered litters. Estradiol-17β varied between 10-20 pg/ml during proestrus, peaked at 30-70 pg/ml late in proestrus and fluctuated between 10-30 pg/ml during pregnancy or the duration of luteal activity in the nonpregnant animals. The preovulatory LH rise, 5-15 ng/ml, extended over 3 days during and immediately following the peak estradiol-17β values. An earlier elevation in LH was observed in 3 of the estrous animals. Progesterone began increasing during the LH surge and peaked 11-14 days later at 22-40 ng/ml. Progesterone concentrations greater than 3 ng/ml were maintained for 56-68 days in 6 of the 7 animals exhibiting estrus. Progesterone concentrations declined at parturition but continued to fluctuate between 0.2-3 ng/ml for 3-6 weeks.

Biology of Reproduction↗

USGS2015

Laboratory investigations of African Pouched Rats ( Cricetomys gambianus ) as a potential reservoir host species for Monkeypox Virus

Monkeypox is a zoonotic disease endemic to central and western Africa, where it is a major public health concern. Although Monkeypox virus (MPXV) and monkeypox disease in humans have been well characterized, little is known about its natural history, or its maintenance in animal populations of sylvatic reservoir(s). In 2003, several species of rodents imported from Ghana were involved in a monkeypox outbreak in the United States with individuals of three African rodent genera ( Cricetomys , Graphiurus , Funisciurus ) shown to be infected with MPXV. Here, we examine the course of MPXV infection in Cricetomys gambianus (pouched Gambian rats) and this rodent species’ competence as a host for the virus. We obtained ten Gambian rats from an introduced colony in Grassy Key, Florida and infected eight of these via scarification with a challenge dose of 4X10 4 plaque forming units (pfu) from either of the two primary clades of MPXV: Congo Basin (C-MPXV: n = 4) or West African (W-MPXV: n = 4); an additional 2 animals served as PBS controls. Viral shedding and the effect of infection on activity and physiological aspects of the animals were measured. MPXV challenged animals had significantly higher core body temperatures, reduced activity and increased weight loss than PBS controls. Viable virus was found in samples taken from animals in both experimental groups (C-MPXV and W-MPXV) between 3 and 27 days post infection (p.i.) (up to 1X10 8 pfu/ml), with viral DNA found until day 56 p.i. The results from this work show that Cricetomys gambianus (and by inference, probably the closely related species, Cricetomys emini ) can be infected with MPXV and shed viable virus particles; thus suggesting that these animals may be involved in the maintenance of MPXV in wildlife mammalian populations. More research is needed to elucidate the epidemiology of MPXV and the role of Gambian rats and other species.

PLoS Neglected Tropical Diseases↗

USGS2012

Foraging optimally for home ranges

Economic models predict behavior of animals based on the presumption that natural selection has shaped behaviors important to an animal's fitness to maximize benefits over costs. Economic analyses have shown that territories of animals are structured by trade-offs between benefits gained from resources and costs of defending them. Intuitively, home ranges should be similarly structured, but trade-offs are difficult to assess because there are no costs of defense, thus economic models of home-range behavior are rare. We present economic models that predict how home ranges can be efficient with respect to spatially distributed resources, discounted for travel costs, under 2 strategies of optimization, resource maximization and area minimization. We show how constraints such as competitors can influence structure of homes ranges through resource depression, ultimately structuring density of animals within a population and their distribution on a landscape. We present simulations based on these models to show how they can be generally predictive of home-range behavior and the mechanisms that structure the spatial distribution of animals. We also show how contiguous home ranges estimated statistically from location data can be misleading for animals that optimize home ranges on landscapes with patchily distributed resources. We conclude with a summary of how we applied our models to nonterritorial black bears (Ursus americanus) living in the mountains of North Carolina, where we found their home ranges were best predicted by an area-minimization strategy constrained by intraspecific competition within a social hierarchy. Economic models can provide strong inference about home-range behavior and the resources that structure home ranges by offering falsifiable, a priori hypotheses that can be tested with field observations.

Journal of Mammalogy↗

USGS2009

Forest rodents provide directed dispersal of Jeffrey pine seeds

Some species of animals provide directed dispersal of plant seeds by transporting them nonrandomly to microsites where their chances of producing healthy seedlings are enhanced. We investigated whether this mutualistic interaction occurs between granivorous rodents and Jeffrey pine ( Pinus jeffreyi ) in the eastern Sierra Nevada by comparing the effectiveness of random abiotic seed dispersal with the dispersal performed by four species of rodents: deer mice ( Peromyscus maniculatus ), yellow-pine and long-eared chipmunks ( Tamias amoenus and T. quadrimaculatus ), and golden-mantled ground squirrels ( Spermophilus lateralis ). We conducted two caching studies using radio-labeled seeds, the first with individual animals in field enclosures and the second with a community of rodents in open forest. We used artificial caches to compare the fates of seeds placed at the range of microsites and depths used by animals with the fates of seeds dispersed abiotically. Finally, we examined the distribution and survival of naturally establishing seedlings over an eight-year period. Several lines of evidence suggested that this community of rodents provided directed dispersal. Animals preferred to cache seeds in microsites that were favorable for emergence or survival of seedlings and avoided caching in microsites in which seedlings fared worst. Seeds buried at depths typical of animal caches (5–25 mm) produced at least five times more seedlings than did seeds on the forest floor. The four species of rodents differed in the quality of dispersal they provided. Small, shallow caches made by deer mice most resembled seeds dispersed by abiotic processes, whereas many of the large caches made by ground squirrels were buried too deeply for successful emergence of seedlings. Chipmunks made the greatest number of caches within the range of depths and microsites favorable for establishment of pine seedlings. Directed dispersal is an important element of the population dynamics of Jeffrey pine, a dominant tree species in the eastern Sierra Nevada. Quantifying the occurrence and dynamics of directed dispersal in this and other cases will contribute to better understanding of mutualistic coevolution of plants and animals and to more effective management of ecosystems in which directed dispersal is a keystone process.

Ecology↗

USGS1992

Evaluating habitat selection with radio-telemetry triangulation error

Radio-telemetry triangulation errors result in the mislocation of animals and misclassification of habitat use. We present analytical methods that provide improved estimates of habitat use when misclassification probabilities can be determined. When misclassification probabilities cannot be determined, we use random subsamples from the error distribution of an estimated animal location to improve habitat use estimates. We conducted Monte Carlo simulations to evaluate the effects of this subsampling method, triangulation error, number of animal locations, habitat availability, and habitat complexity on bias and variation in habitat use estimates. Results for the subsampling method are illustrated using habitat selection by redhead ducks ( Aythya americana ). We recommend the subsampling method with a minimum of 50 random points to reduce problems associated with habitat misclassification.

Wisconsin↗