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Results for “Biology of Reproduction”

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At least 73 records · Page 4Linked to original sources
USGS1996

More flowers or new cladodes? Environmental correlates and biological consequences of sexual reproduction in a Sonoran Desert prickly pear cactus, Opuntia engelmannii

Should a platyopuntia expend all aerolar meristems in flower production, now new cladodes could be produced, and further reproductive effort and vegetative growth would cease. To investigate the trade-off between flower and cladode production, the numbers of flowers, fruits, and cladodes were monitored for 4 years on 30 Opuntia engelmannii Salm-Dyek, plants on Tumamoc Hill, Tucson, Arizona. Plant size controlled the number of flowers initiated each spring. The proportion of flowers that developed (i.e., did not abort) was perhaps determined by December-February rainfall in the months before bloom, with more being developed in the wettest years. Models based on different ratios of initiated cladodes to initiated flowers demonstrated that continued high investment in flowers and fruits would eventually terminate reproduction altogether; therefore periods of high sexual reproduction should alternate with periods of high vegetative growth. In the first 3 years of this study, the ratio of new cladodes to initiated flowers was low, showing a high investment in sexual reproduction. As suggested by the model, the population recouped this investment in the fourth year, when the number of new cladodes was nearly 3 times the 1992-1994 mean, and the number of initiated flowers was only 73% of the 3-year mean.

Arizona↗
USGS2022

From flowering to foliage: Accelerometers track tree sway to provide high-resolution insights into tree phenology

Trees are bioindicators of global climate change and regional urbanization, but available monitoring tools are ineffective for fine-scale observation of many species. Using six accelerometers mounted on two urban ash trees ( Fraxinus americana ), we looked at high-frequency tree vibrations, or change in periodicity of tree sway as a proxy for mass changes, to infer seasonal patterns of flowering and foliage (phenophases). We compared accelerometer-estimated phenophases to those derived from digital repeat photography using Green Chromatic Coordinates (GCC) and visual observation of phenophases defined by the USA National Phenology Network (NPN). We also drew comparisons between two commercial accelerometers and assessed how placement height influenced the ability to extract seasonal transition dates. Most notably, tree sway data showed a greenness signal in an urban environment and produced a clear flowering time-series and peak flowering signal (PF), marking the first observations of a flower phenophase using accelerometer data. Estimated start of spring (SOS) from accelerometers and time-lapse GCC were more similar than start of autumn (SOA); accelerometers lagged behind the time-lapse camera dates by three and four days for SOS and 13 and 14 days for SOA for each tree. Estimates for SOS and SOA from accelerometers and time-lapse cameras aligned closely with different NPN phenophases. The two commercial accelerometers produced similar season onset: a difference of 2.4 to 3.8 days for SOS, 2.1 days for SOA, and 0.5 to 2.0 days for PF. Accelerometers placed at the main crown branch point versus higher in the canopy showed a difference of 0.2 to 4.9 days for SOS and -1.5 to 1.7 days for PF. Our results suggest accelerometers present a novel opportunity to objectively monitor reproductive tree biology and fill gaps in phenology observations. Furthermore, widely available accelerometers show promise for scaling up from individual trees to the landscape level to aid forest management and assessing climate change impacts to tree phenology.

Colorado↗
USGS2018

Food web contaminant dynamics of a large Atlantic Slope river: Implications for common and imperiled species

Persistent and bioaccumulative contaminants often reach concentrations that threaten aquatic life by causing alterations in organism behavior and development, disruption of biological processes, reproductive abnormalities, and mortality. The objectives of this research were to determine the aquatic food web structure and trophic transfer and accumulation of contaminants within a riverine ecosystem and identify potential stressors to the health of an imperiled fish, the robust redhorse (Moxostoma robustum) and other species of conservation concern in a large Atlantic Slope (USA) river. Trophic position was determined for food web taxa by stable isotope analyses of representative producers, consumers, and organic matter of the Yadkin-Pee Dee River of North Carolina and South Carolina. Contaminant analyses were performed on water, sediment, organic matter, and aquatic biota to assess the prevalence and accumulation of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), current use pesticides (CUPs), polycyclic aromatic hydrocarbons (PAHs), and selected metals. Contaminants were prevalent in the environment and food web components of the river. PCBs were detected in 32% of biotic samples (mean 0.24 μg/g dry weight [DW], range 0.01–3.33 μg/g DW), and DDTs (legacy OCPs and metabolites) were detected in 90% (mean 0.014 μg/g DW, range 0.0004–0.29 μg/g DW). The trace metals manganese and cadmium exceeded published threshold effect concentrations in sediment (460 and 0.99 μg/g DW, respectively). Mercury was detected in all food web samples exhibiting a mean of 0.61 μg/g DW and range 0.006–2.35 μg/g DW (mean 0.13 μg/g wet weight [WW], range 0.001–0.6 μg/g WW). Concentrations exceeded the 0.2 μg/g WW aquatic life criterion for mercury in 38% of fish samples. Fish trophic magnification factors (TMFs; range 0.33–3.75) indicated that contaminant accumulation occurred from both water and dietary sources. The combination of analytical approaches applied here provides new insight into contaminant dynamics with conservation implications.

Science of the Total Environment↗
USGS2022

PCB exposure is associated with reduction of endosymbionts in riparian spider microbiomes

Microbial communities, including endosymbionts, play diverse and critical roles in host biology and reproduction, but contaminant exposure may cause an imbalance in the microbiome composition with subsequent impacts on host health. Here, we examined whether there was a significant alteration of the microbiome community within two taxa of riparian spiders (Tetragnathidae and Araneidae) from a site with historical polychlorinated biphenyl (PCB) contamination in southern Ontario, Canada. Riparian spiders specialize in the predation of adult aquatic insects and, as such, their contaminant levels closely track those of nearby aquatic ecosystems. DNA from whole spiders from sites with either low or high PCB contamination was extracted, and spider microbiota profiled by partial 16S rRNA gene amplicon sequencing. The most prevalent shift in microbial communities we observed was a large reduction in endosymbionts in spiders at the high PCB site. The abundance of endosymbionts at the high PCB site was 63 % and 98 % lower for tetragnathids and araneids, respectively, than at the low PCB site. Overall, this has potential implications for spider reproductive success and food webs, as riparian spiders are critical gatekeepers of energy and material fluxes at the land-water interface.

Science of the Total Environment↗
USGS2007

Analysis of the sea otter ( Enhydra lutris ) reproductive tract: A methods manual

Reproduction in the female sea otter, Enhydra lutris, was relatively unstudied until Sinha et al. (1966) examined 140 reproductive tracts collected 1955-62 and used their findings to describe sea otter reproductive anatomy and biology. Two years later Sinha and Conaway (1968) published a more detailed paper on the ovary of the sea otter. These descriptive papers have been used as the basis for all subsequent studies of sea otter reproductive tracts. During biological collections of sea otters in the 1960s and 70s a large number of female carcasses became available to wildlife biologists. Using Sinha’s research, Schneider (1973) analyzed 1,482 female reproductive tracts to determine the timing of reproduction, gestation period, age of sexual maturity, fetal sex ratio and growth rate of otters in the Aleutian Islands. A similar study was conducted by Bodkin et al. (1993) on a sample of 177 females collected after the 1989 Exxon Valdez oil spill. Recently (von Biela 2007) examined 134 reproductive tracts obtained from beachcast and harvested otters across the three Alaskan population stocks as part of a Master’s thesis. As with most life history data, comparisons among and within populations that differ in status relative to equilibrium densities provide useful data with which to test hypotheses about the cause and effects of changes in demographic rates such as reproductive rate. However, in order to make such comparisons, methods used in different periods must be comparable. The purpose of this manual is to explicitly describe how to collect and analyze sea otter reproductive tracts for the determination of reproductive rate, pregnancy rate, percentage of mature females, and timing of reproduction so that the data will be directly comparable to that collected in the past. The techniques presented in this manual have been used to study sea otter populations over the last 50 years, and maintaining such consistency is essential to comparisons in the future. This manual is based on the methods of previous researchers and draws heavily on the published and unpublished works of James Bodkin, Karl Kenyon, Calvin Lensink, Daniel Mulcahy, Karl Schneider, and Akhouri Sinha. Most invaluable to the production of this manual were the direct communications with Karl Schneider and Dan Mulcahy. In each instance, researchers have communicated with each other to attain comparable methods. Recognizing that researchers in the future may not have this luxury, this guide has been produced to preserve the technique. In addition to using this manual, researchers should consult with colleagues experienced in the analysis of mammalian reproductive tracts, preferably specific to sea otters. Individuals are encouraged to contact V. von Biela with any questions. Sea otter reproductive tracts have most commonly come from either intentional sampling through harvests (Sinah et al. 1966, Schneider 1975) or unintentional large scale mortalities (e.g. the 1989 Exxon Valdez oil spill) (Bodkin et al. 1993). Carcasses and reproductive tracts can also be obtained through the collection of fresh beach cast carcasses. Analysis of reproductive tracts should consider the source of carcasses as samples representing either the “living” or “dead” sea otter population, as they may differ in reproductive parameters. In most cases the reproductive tracts are fixed in formalin or frozen (minimum of –20˚C) immediately after collection; both methods are acceptable for later analysis of the tissue. Immediate fixation is preferred as it is a necessary step in analysis. Uteri and ovaries are then examined to determine the current and past reproductive history of each individual. This manual also includes an example datasheet (Appendix A) and glossary (Appendix B).

Technical Report↗
USGS2026

Black Carp Mylopharyngodon piceus reproductive development and maturation in the Mississippi River basin

Black Carp Mylopharyngodon piceus are native to most major east Asian drainages and are internationally cultured for use as a food-fish or a biological control for molluscs. We describe the reproductive biology of Black Carp from the growing invasive population in the Mississippi River basin through examination of incidental commercial fisheries and biologist captures. Our objectives were to assess (1) reproductive development by combined macroscopic and histological staging to compare reproductive maturation by total length, estimated age, and latitude; (2) population functions of gonadosomatic index, length and age, and weight and length relationships; and (3) absolute fecundity. We identified length as a better predictor of reproductive maturation than age, with variation among individuals, and between males and females, with higher probability of maturation anticipated for larger and older individuals predicted around 1050 mm total length (TL; 6 years) for females and 950 mm TL (5 years) for males ( n = 548). Proposed sizes and ages are representative minimum and should be interpreted with the understanding that spawning and recruitment success increase for older, more mature fish than in early stages. Observed growth rates were rapid relative to both native and introduced ranges. We confirmed that Black Carp are developmentally indeterminate batch spawners due to the simultaneous presence of advanced growth oocytes via histology and egg measurements, with preserved egg average diameters ranging from 0.395 to 3.215 mm ( n = 23). Absolute fecundity estimates ranged from 72,748 to 3,542,789 eggs across the 966 to 1412 mm TL size range of individuals, with substantial variability among individuals attributed to poor relative fecundity estimates. These results represent the first step in assessing the reproductive rates of Mississippi River Black Carp via the size of reproductive development and potential contributions through fecundity. The results and population rates presented here may be used or adapted for future studies on regional spawning phenology and reproductive development, or in population growth models for control.

Arkansas, Illinois, Indiana, Kentucky, Louisiana, ↗
USGS2017

Reproductive success of Mariana swiftlets (Aerodramus bartschi) on the Hawaiian island of O'ahu

Mariana Swiftlets ( Aerodramus bartschi ) are federally listed as endangered, with populations currently limited to just three islands in the Mariana Islands plus an introduced population on the Hawaiian island of O'ahu. Before efforts are made to reintroduce Mariana Swiftlets to other islands in the Mariana archipelago, additional information is needed concerning their breeding biology. Therefore, our objective was to examine the reproductive biology of Mariana Swiftlets over five annual cycles on the Hawaiian island of O'ahu. This introduced population used a human-made tunnel for roosting and nesting, and was studied as a surrogate to negate interference with endangered populations in the Mariana Islands. Active nests ( N = 478) were observed in every month of the year, with peak nesting activity between May and September. All clutches consisted of one egg. Mean duration of incubation and nestling periods were 23.9 d (range = 18–30 d, N = 233) and 55.0 d (range = 41–84 d, N = 228), respectively. Estimated nest success was 63%. Over half (52%) of nest failures were attributed to eggs found on the tunnel floor. Predation by rats ( Rattus spp.) was also an important cause of nest failure and often resulted in the loss of most active nests. However, Mariana Swiftlets did re-nest after these predation events. Our results suggest that rat predation of both nests and adults may limit growth of the Mariana Swiftlet population on O'ahu, and could also affect the chances for successful establishment of relocated populations in the Mariana Islands. Another limiting factor on O'ahu is that only one nesting site is apparently available on the island. Current goals for downlisting Mariana Swiftlets from endangered to threatened include establishing populations on Guam, Rota, Aguiguan, and Saipan. To meet these goals, the population of Mariana Swiftlets on O'ahu can be important for testing reintroduction techniques, learning more about the natural history of these swiftlets, and providing individuals for reintroduction efforts in the Mariana Islands.

Hawai'i↗
USGS2013

The predicted influence of climate change on lesser prairie-chicken reproductive parameters

The Southern High Plains is anticipated to experience significant changes in temperature and precipitation due to climate change. These changes may influence the lesser prairie-chicken (Tympanuchus pallidicinctus) in positive or negative ways. We assessed the potential changes in clutch size, incubation start date, and nest survival for lesser prairie-chickens for the years 2050 and 2080 based on modeled predictions of climate change and reproductive data for lesser prairie-chickens from 2001-2011 on the Southern High Plains of Texas and New Mexico. We developed 9 a priori models to assess the relationship between reproductive parameters and biologically relevant weather conditions. We selected weather variable(s) with the most model support and then obtained future predicted values from climatewizard.org. We conducted 1,000 simulations using each reproductive parameter's linear equation obtained from regression calculations, and the future predicted value for each weather variable to predict future reproductive parameter values for lesser prairie-chickens. There was a high degree of model uncertainty for each reproductive value. Winter temperature had the greatest effect size for all three parameters, suggesting a negative relationship between above-average winter temperature and reproductive output. The above-average winter temperatures are correlated to La Nina events, which negatively affect lesser prairie-chickens through resulting drought conditions. By 2050 and 2080, nest survival was predicted to be below levels considered viable for population persistence; however, our assessment did not consider annual survival of adults, chick survival, or the positive benefit of habitat management and conservation, which may ultimately offset the potentially negative effect of drought on nest survival.

PLoS ONE↗
USGS2023

A review of grass carp and related species literature on diet, behavior, toxicology, and physiology focused on informing development of controls for invasive grass carp populations in North America

Grass carp ( Ctenopharyngodon idella ) are globally important in aquaculture and aquatic vegetation control. However, escaped grass carp have established invasive populations. A targeted keyword search was performed on a carp (order: Cypriniformes) literature database maintained by the U.S. Geological Survey to identify literature relevant to grass carp. Additional sources cited in reviewed documents and provided by numerous reviewers were also included. There were three focus areas designed to provide support for invasive grass carp management: (1) diet and behavior; (2) physiological constraints, toxicity, and biology; and (3) gut physiology. Each focus area provides information to guide development of potential pathways for invasive grass carp control. Information from other carp species was used to fill in gaps where grass carp information was lacking and provide additional, potential research directions. Diet-related information included food selection and aquacultural diet formulations. Behavioral information included stimuli and non-physical barriers to attract, repel, or stop movement. Physiological constraints, toxicology, reproductive control, and biological control provide a research review for control options. Gut physiology and related control pathways provide knowledge to improve toxin or pathogen delivery. This review provides a basis for developing approaches and research for controlling invasive grass carp populations, aquaculture, and native population management.

Fishes↗
USGS2017

Status of scientific knowledge, recovery progress, and future research directions for the Gulf Sturgeon, Acipenser oxyrinchus desotoi Vladykov, 1955

The Gulf Sturgeon, Acipenser oxyrinchus desotoi , is an anadromous species of Acipenseridae and native to North America. It currently inhabits and spawns in the upper reaches of seven natal rivers along the northern coast of the Gulf of Mexico from the Suwannee River, Florida, to the Pearl River, Louisiana, during spring to autumn. Next to the Alligator Gar (Atractosteus spatula) , the Gulf Sturgeon is currently the largest fish species occurring in U.S. Gulf Coast rivers, attaining a length of 2.35 m and weights exceeding 135 kg, but historically attained a substantially larger size. Historically, the spawning populations existed in additional rivers from which the species has been wholly or nearly extirpated, such as the Mobile and Ochlockonee rivers, and possibly the Rio Grande River. Most Gulf Sturgeon populations were decimated by unrestricted commercial fishing between 1895–1910. Subsequently most populations remained unrecovered or extirpated due to continued harvest until the 1970s–1980s, and the construction of dams blocking access to ancestral upriver spawning grounds. Late 20th Century harvest bans and net bans enacted by the several Gulf Coast states have stabilized several populations and enabled the Suwannee River population to rebound substantially and naturally. Hatchery supplementation has not been necessary in this regard to date. Sturgeon are resilient and adaptable fishes with a geological history of 150 million years. Research undertaken since the 1970s has addressed many aspects of Gulf Sturgeon life history, reproduction, migration, population biology, habitat requirements, and other aspects of species biology. However, many knowledge gaps remain, prominently including the life history of early developmental stages in the first year of life. Natural population recovery is evident for the Suwannee River population, but seems promising as well for at least four other populations. The Pascagoula and Pearl River populations face a challenging future due a combination of natural and anthropogenic factors. These two populations, and perhaps the Escambia River population, are particularly vulnerable to periodic mass mortality due to major stochastic events including hurricanes, flooding, hypoxia, and toxic spills. The present manuscript provides a comprehensive synthesis of knowledge regarding the Gulf Sturgeon at the organismal and population levels, identifying knowledge gaps as priorities for future research. Topics not treated in the present synthesis include morphology, internal biology, physiology, and endocrinology. Topics only briefly treated include parasites and diseases, contaminants, and sturgeon aquaculture.

Journal of Applied Ichthyology↗
USGS1973

Propagation of barn owls in captivity

Some aspects of the biology and life history of native birds often are more readily obtained in captivity than in the field. This is particularly true in evaluating the effects of pesticides or other pollutants on birds, because establishing cause-and-effect relationships requires experimental studies. Few wild species have been bred in captivity with sufficient success to permit the large-scale studies that are needed. This paper reports successful efforts to breed Barn Owls ( Tyto alba prolinicol a) in captivity and presents biological data concerning reproduction.

The Auk↗
USGS2019

Enhancing reproductive assessments of the Florida manatee Trichechus manatus latirostris by establishing optimal time period and inhibin B baseline concentrations

The Florida manatee Trichechus manatus latirostris occupies coastal and riverine habitats that may influence the species’ endogenous biological rhythms, including its reproductive potential. Inhibin B provides a biomarker of gonadal function and reproductive potential in humans and other eutherian mammals. This study examined the influence of size, sex, and time of year on inhibin B levels in manatees sampled among 3 habitats with varying degrees of environmental stress in Florida. Inhibin B levels in 38 males averaged (±SE) 4.90 ± 0.23 pg ml -1 ; the average level in 31 females was 5.63 ± 0.46 pg ml -1 . Elevated patterns in inhibin B were exhibited between mid-March and mid-August corresponding to increased mating activity and testicular function, with significant differences in inhibin B levels between male and female manatees (p = 0.03) throughout the year. No significant differences in inhibin B were detected between low- and high-impacted sampling locations during winter, suggesting the potential influence of environmental stress on manatee reproduction may be best examined between mid-March and mid-August—the midpoint of the reproductively active, non-winter time period. Establishing temporal baselines for inhibin B values may be useful in assessing manatee reproductive status and potential conservation threats, shedding light on fertility potential, and enabling future assessment of the effects of stressors on reproduction in Florida manatees.

Florida↗
USGS2022

Size distribution and reproductive phenology of the invasive Burmese python (Python molurus bivittatus) in the Greater Everglades Ecosystem, Florida, USA

The design of successful invasive species control programs is often hindered by the absence of basic demographic data on the targeted population. Establishment of invasive Burmese pythons ( Python molurus bivittatus ) in the Greater Everglades Ecosystem, Florida USA has led to local precipitous declines (> 90%) of mesomammal populations and is also a major threat to native populations of reptiles and birds. Efforts to control this species are ongoing but are hampered by the lack of access to and information on the expected biological patterns of pythons in southern Florida. We present data from more than 4,000 wild Burmese pythons that were removed in southern Florida over 26 years (1995–2021), the most robust dataset representing this invasive population to date. We used these data to characterize Burmese python size distribution, size at maturity, clutch size, and seasonal demographic and reproductive trends. We broadened the previously described size ranges by sex and, based on our newly defined size-stage classes, showed that males are smaller than females at sexual maturity, confirmed a positive correlation between maternal body size and potential clutch size, and developed predictive equations to facilitate demographic predictions. We also refined the annual breeding season (approx.100 days December into March), oviposition timing (May), and hatchling emergence and dispersal period (July through October) using correlations of capture morphometrics with observations of seasonal gonadal recrudescence (resurgence) and regression. Determination of reproductive output and timing can inform population models and help managers arrest population growth by targeting key aspects of python life history. These results define characteristics of the species in Florida and provide an enhanced understanding of the ecology and reproductive biology of Burmese pythons in their invasive Everglades range.

Florida↗
USGS2020

Bisphenol A and 17α-ethinylestradiol-induced transgenerational gene expression differences in the brain–pituitary–testis axis of medaka, Oryzias latipes

Endocrine disrupting chemicals (EDCs), such as bisphenol A (BPA) and 17α-ethinylestradiol (EE2), can have far reaching health effects, including transgenerational abnormalities in offspring that never directly contacted either chemical. We previously reported reduced fertilization rates and embryo survival at F2 and F3 generations caused by 7-day embryonic exposure (F0) to 100 μg/L BPA or 0.05 μg/L EE2 in medaka. Crossbreeding of fish in F2 generation indicated subfertility in males. To further understand the mechanisms underlying BPA or EE2-induced adult onset and transgenerational reproductive defects in males, the present study examined the expression of genes regulating the brain–pituitary–testis (BPT) axis in the same F0 and F2 generation male medaka. Embryonic exposure to BPA or EE2 led to hyperactivation of brain and pituitary genes, which are actively involved in reproduction in adulthood of the F0 generation male fish, and some of these F0 effects continued to the F2 generation (transgenerational effects). Particularly, the F2 generation inherited the hyperactivated state of expression for kisspeptin ( kiss1 and kiss2 ) and their receptors ( kiss1r and kiss2r), and gnrh and gnrh receptors. At F2 generation, expression of DNA methyltransferase 1 ( dnmt1 ) decreased in brain of the BPA treatment lineage, while EE2 treatment lineage showed increased dnmt3bb expression. Global hypomethylation pattern was observed in the testis of both F0 and F2 generation fish. Taken together, these results demonstrated that BPA or EE2-induced transgenerational reproductive impairment in the F2 generation was associated with alterations of reproductive gene expression in brain and testis and global DNA methylation in testis.

Biology of Reproduction↗
USGS2021

Sex- and developmental stage-related differences in the hepatic transcriptome of Japanese quail (Coturnix japonica) exposed to 17β-Trenbolone

Endocrine-disrupting chemicals can cause transcriptomic changes that may disrupt biological processes associated with reproductive function including metabolism, transport, and cell growth. We investigated effects from in ovo and dietary exposure to 17β-trenbolone (at 0, 1, and 10 ppm) on the Japanese quail ( Coturnix japonica ) hepatic transcriptome. Our objectives were to identify differentially expressed hepatic genes, assess perturbations of biological pathways, and examine sex- and developmental stage–related differences. The number of significantly differentially expressed genes was higher in embryos than in adults. Male embryos exhibited greater differential gene expression than female embryos, whereas in adults, males and females exhibited similar numbers of differentially expressed genes (>2-fold). Vitellogenin and apovitellenin-1 were up-regulated in male adults exposed to 10 ppm 17β-trenbolone, and these birds also exhibited indications of immunomodulation. Functional grouping of differentially expressed genes identified processes including metabolism and transport of biomolecules, enzyme activity, and extracellular matrix interactions. Pathway enrichment analyses identified as perturbed peroxisome proliferator–activated receptor pathway, cardiac muscle contraction, gluconeogenesis, growth factor signaling, focal adhesion, and bile acid biosynthesis. One of the primary uses of 17β-trenbolone is that of a growth promoter, and these results identify effects on mechanistic pathways related to steroidogenesis, cell proliferation, differentiation, growth, and metabolism of lipids and proteins.

Environmental Toxicology and Chemistry↗
USGS1989

The brown tree snake, an introduced pest species in the central Pacific Islands

The reproduction of endangered Mariana crows ( Corvus kubaryi ) is intensively monitored, nests are protected, and (when necessary) eggs or young are moved to the safety of lab conditions until they are less vulnerable to the threats in natural habitats. Barriers on tree trunks and judicious pruning of adjacent trees are used in attempts to exclude snakes from nest trees. Two birds unique to Guam--the Micronesian kingfisher ( Halcyon cinnamomina cinnamomina ) and Guam rail ( Gallirallus owstoni )-- are maintained at captive propagation facilities on Guam and in mainland zoos. Studies of these and other species, in captivity and on nearby islands, are underway to bolster our biological understanding of their behavior, reproduction, habitat use, and population biology.

Endangered Species Technical Bulletin↗
USGS2019

Species traits predict stream-fish invaders in an Appalachian (U.S.A.) river basin

We compared the influence of biological traits (morphology, physiology, reproduction, and life history), ecological traits (geographic distribution, habitat associations, food habits), and introduction attributes (propagule pressure, human use of a species, residence time) on invasion success of native and introduced stream fishes during the colonisation and spread stages in an Appalachian (U.S.A.) river basin. Colonisation success was positively related to residence time, benthic feeding, an equilibrium life-history strategy, and nest spawning. Successful spread was associated with tolerance to increased temperature and an equilibrium life-history strategy. The spread of introduced fishes was negatively related to gamefish status. No effect of propagule pressure was detected. Traits linked to invasion success were consistent with the hypothesis that human land-use practices increase the invasibility of highland catchments by creating novel conditions better suited to lowland and equilibrium invaders. We found biological traits to be more useful than ecological traits in predicting invasion success and suggesting invasion mechanisms. Parental care and nest association can facilitate invasions over large spatial extents for both native and introduced fishes. Analyses of suites of traits can reveal mechanisms of invasions and tactics for controlling them; such mechanisms and tactics may be system-specific and scale-dependent.

North Carolina, Virginia↗
USGS1977

Reproductive steroids in the white-tailed deer (Odocoileus virginianus borealis). I. Seasonal changes in the female

A total of 161 blood samples collected from 77 white-tailed does ( Odocoileus virginianus borealis ) during the years 1971 through 1974 in Minnesota were utilized to make a preliminary characterization of the estrogen and progesterone levels in pregnant and nonpregnant animals. Progesterone and estrogen were measured by radioimmunoassay. Progesterone levels during the months of December through February were similar for pregnant and nonpregnant animals (3.98 ± 0.57 vs. 5.50 ± 0.82 ng/ml, x̄ ± S.E., N.S., t = 1.51). The pregnant animals had higher progesterone levels during the March through May period (4.61 ± 0.44 vs. 1.94 ± 0.85, P<0.01). Progesterone levels during the months of June to early November, i.e., anestrus, were low and similar for lactating and nonlactating animals. Estrogen levels did not change during the year except for the period just before parturition in the pregnant does when estrogen levels were dramatically elevated (178 ± 29 pg/ml). Two nonpregnant adult does were sampled every 5 days from late January through early March. Progesterone levels exhibited a cyclic pattern of about 28 days duration. Estrogen levels showed no distinct pattern but tended to be inversely related to progesterone. These data suggest that 1) deer exhibit estrous cycles of about 25 to 30 days in length, 2) that estrous cycles recurred in nonpregnant does from November through early March, 3) that progesterone levels are similar for pregnancy and the luteal phase of the estrous cycle and 4) that late pregnancy is characterized by high estrogen levels as compared to early pregnancy and the estrous cycle.

Minnesota↗