bluuebunny/crossref_metadata_2025 huggingface dataset:
Endometrial Stromal Sarcoma with Smooth Muscle and Glandular Differentiation of the Feline Uterus
Authors: Sato T. , Maeda H. , Suzuki A. , Shibuya H. , Sakata A. , Shirai W.
Published: May 2007

The intra-abdominal tumor developing in the uterus and lung of a domestic Shorthair cat was examined histopathologically and immunohistochemically. The tumor showed a proliferation of both endometrial stromal and smooth muscle cells accompanied by prominent vasculature. There were well-differentiated endometrial glands, and tubuli made up a monolayer of eosinophilic cuboidal epithelium. Immunohistochemically, the spindle-shaped cells and half of the stromal-like cells reacted to caldesmon and desmin antibodies. The neoplastic epithelium expressed AE1/AE3 cytokeratin. Feline endometrial stromal tumor has, to the best of our knowledge, not been reported previously and has smooth muscle and glandular components that are a unique variant to the human counterpart.
Ovarian and Intestinal Angiomatosis in a Horse
Authors: Lamm C. G. , Njaa B. L.
Published: May 2007

Dozens of red, raised nodules scattered along the serosal surface of the small intestine and the right and left ovaries were observed as incidental findings on gross examination in a 21-year-old Thoroughbred mare euthanatized for severe lameness. Histologically, these nodules were composed of numerous, variably sized, redundant vascular profiles filled with red blood cells and fibrin thrombi. Based on the presence of multiple nodules composed of benign vascular channels scattered within the small intestine and ovary, a diagnosis of angiomatosis is proposed. To the authors' knowledge, this is the first report of small intestinal and ovarian angiomatosis in a horse.
Primary Cardiac Fibrosarcoma with Pulmonary Metastasis in a Labrador Retriever
Authors: Speltz M. C. , Manivel J. C. , Tobias A. H. , Hayden D. W.
Published: May 2007

A 6–year-old, neutered male Labrador Retriever was diagnosed with congestive heart failure, and an echocardiogram revealed a large mass inside the pericardial sac associated with the left ventricle. At necropsy, the dog had marked ascites, mild hydrothorax, marked hydropericardium, and an 11.0 X 7.0 X 6.0 cm, tan and red, firm, well-demarcated mass attached to the left ventricular free wall. The mass was diagnosed as a fibrosarcoma based on the morphologic appearance and supportive immunohistochemical staining. To our knowledge, this is the first case report of a primary fibrosarcoma involving the left ventricular free wall myocardium, epicardium, and pericardium with a pulmonary metastasis in a dog.
Two early case reports on conjoined twins
Authors: van der Weiden Robert MF
Published: May 2007

Case reports of thoracopagus/xiphopagus conjoined twins by Godofredus Christell (1751) and Francesco Luigi Fanzago (1803) have been recovered and can be added to the history of conjoined twins.
Some implications of chaos theory for the genetic analysis of human development and variation
Authors: Eaves Lindon J , Kirk Katherine M , Martin Nicholas G , Russell Robert J
Published: May 2007

Non-linear epigenetic processes are a potential underlying source of phenotypic differences in development. Simulation studies of twin pairs using simple non-linear development models characterised by chaotic or near-chaotic behavior are presented. The effect of chaotic processes on correlations is to lower them from their initial values, but high initial correlations are affected much less by chaotic and near-chaotic processes than intermediate correlations. Therefore, we would predict that traits affected by chaotic processes would have high MZ and low DZ twin correlations and this is reminiscent of certain traits such as EEG spectra. However the much more frequent observation of MZ correlations close to twice their DZ counterparts would suggest that the role of chaos in development is quite limited.
Risk of premature birth in multifetal pregnancy
Authors: Minakami H , Kosuge S , Fujiwara H , Mori Y , Sato I
Published: May 2007

The risk of preterm delivery ( < 37 weeks of gestation) is approximately nine times higher in women with multifetal pregnancies than in women with singleton pregnancies. However, it is possible that the risk will vary according to gestational week. To assess the risk of premature birth within 1 week by gestational age among multifetal pregnancies and compare the estimated risk with that of singleton pregnancies, we analyzed 6 036 475 infants born in singleton pregnancies and 90 887 infants born in multifetal pregnancies in Japan ( ≥ 22 weeks) over the 5-year period 1989–1993. An estimate of the risk of birth within 1 week at gestational week n was obtained by dividing the number of infants delivered at gestational week n by the number of infants delivered at or beyond gestational week n. The risk at 22 weeks was 0.9 per 1000 fetuses for singleton pregnancies and 5.0 per 1000 for multifetal pregnancies. The risk remained relatively stable until 27 weeks of gestation, then sharply increased toward 36 weeks of gestation in both singleton and multifetal pregnancies. The odds ratio for birth within 1 week for fetuses of multifetal pregnancies compared with fetuses of singleton pregnancies was 5.9 (95% CI, 5.4–6.5) at 22 weeks of gestation, increasing gradually with increasing gestational age until 33 weeks of gestation (13.7; 95% CI, 13.1–14.2) but declining thereafter to 8.8 (95% CI, 8.6–8.9) at 36 weeks of gestation. Results of data analysis for each year of the 5-year period did not differ substantially. Twin Research (2000) 3, 2–6.
The comparative constitution of twinship: strategies and paradoxes
Authors: Stewart EA
Published: May 2007

In both traditional and modern societies, twinship, as an unusual mode of reproduction, involves difficulties for social systems in maintaining consistent classification systems. It is proposed that the most prevalent response to twinship involves various ‘strategies of normalisation’ to defuse and contain the potential disruption. This proposition is illustrated and analysed in relation to ethnographic maternal drawn mainly (but not exclusively) from African communities in the twentieth century. Following a discussion of twin infanticide as the most extreme of the normalising strategies, the article concludes by identifying a number of paradoxes in the social construction of twinship. Twin Research (2000) 3, 142–147.
Birth Weight Corrected for Gestational Age is Related to the Incidence of Down's Syndrome Pregnancies
Authors: van Montfrans Joris M. , Bakker Petra S.M. , Rekers-Mombarg Lyset T.M. , van Weissenbruch Mirjam M. , Lambalk Cornelis B.
Published: May 2007

Three recent studies reported that early depletion of the primordial follicle pool is likely to be an independent risk factor for Down's syndrome pregnancies. The size of the primordial follicle pool at birth is determined by oogenesis and by the rate of follicle atresia during the intra uterine period. Since intra uterine growth retardation was reported to be associated with a significantly reduced primordial follicle pool at birth, we investigated the possibility of a relation between low birth weight for gestational age and the risk of a Down's syndrome pregnancy. In a case control study, 95 women with a history of a Down's syndrome pregnancy and 85 controls provided information on their own birth weight and length of gestation. Birth weight standard deviation scores, indicating the difference in birth weight from a reference group, were significantly lower in Down's syndrome mothers than in controls. These findings illustrate that the risk of a Down's syndrome pregnancy is related to a low birth weight corrected for gestational age, possibly by a causal relation between intra uterine growth retardation and the size of the primordial follicle pool
The Rate of Preterm Twin Births (22–27 Weeks) As a Criterion for Measuring the Quality of Prenatal Care
Authors: Papiernik Emile
Published: May 2007

While the true figures are not well established, outcomes of twin pregnancies are directly dependent on a small number of preterm births between 22 and 27 weeks. Observation of perinatal outcomes in twin pregnancies yields two contradictory results. Firstly, it shows an improvement in perinatal mortality figures. Secondly, it reveals an increase in the rates of preterm deliveries. These findings result from the observation of 783 twin pregnancies followed and delivered in a level 3 perinatal centre in Paris between 1993 and 1998. Women followed since the beginning of pregnancy through the outpatient clinic of the institution are included in this number, as are women who were referred or transferred to the centre at a later date due to complications. This analysis reflects the influence of two contrasting policies. The first, and less recent policy is devoted to the prevention of preterm births, and is reflected by the low number of extremely preterm deliveries at 22–32 weeks. The second is the effect of our new approach to the prevention of foetal deaths in relation to foetal growth retardation in twins which has resulted in increased medical intervention such as the induction of labour or scheduled Caesarean birth. This has resulted in an increase in twin preterm births from 33 to 36 weeks, with the expected result of fewer foetal deaths.
Revisiting the Children of Twins: Can They Be Used to Resolve the Environmental Effects of Dyadic Parental Treatment on Child Behavior?
Authors: Eaves Lindon J. , Silberg Judy L. , Maes Hermine H.
Published: May 2007

The children of twins (COT) design has been proposed as an alternative to the adoption study to resolve the direct effects of parental treatment from secondary parent–child association due to genetic factors. The basic analytical approach compares the parent–offspring correlation with the correlation between children and the monozygotic (MZ) twins of their parents. We show that a significant difference between these correlations does not imply direct environmental causality when the measured parental treatment in question is dyadic, that is, influenced by both parents even when mating is random. Nongenetic causal effects yield very similar patterns of correlation to secondary genetic effects on dyadic treatment variables. The fact that many candidate environments, such as parental divorce, are dyadic gives reason to question the interpretation of their correlations with behavior in the children of twins.
Environmental Factors Determine Where the Dutch Live: Results From the Netherlands Twin Register
Authors: Willemsen Gonneke , Posthuma Danielle , Boomsma Dorret I.
Published: May 2007

The heritability of the degree of residential area urbanization in twins and their siblings in the Dutch population was examined. The postal code was known for 6879 twins and 2724 siblings registered with the Netherlands Twin Register and born between 1940 and 1983. Using data from Statistics Netherlands (Centraal Bureau voor de Statistiek, 2001), these postal codes could be related to residential area characteristics, including urbanization level. The degree of urbanization was assessed on a 5-point scale: very heavy, heavy, moderate, low and not urbanized. Genetic model-fitting was carried out in three age cohorts: young adults (born 1975 to 1983), adults (born 1965 to 1974) and older adults (born 1940 to1964). Twin and sibling resemblance in urbanization level was expressed in polychoric correlations. These correlations decreased from the youngest cohort (.66 to .86) to the oldest cohort (.20 to .58). In all 3 age cohorts, genetic factors did not contribute to familial resemblance. The influence of common environment decreased in importance from the young cohort (70% to 83%) to the old cohort (46% to 47%) and was lower in women than in men in all but the oldest age cohort. This study did not replicate Australian findings of a genetic contribution in the older cohorts; common environmental factors and, increasingly with age, unique environmental factors determine where the Dutch live. Future studies in European and other populations will reveal whether these results are specific to the Dutch population.
Twins Born Following Fertility Treatment: Implications for Quantitative Genetic Studies
Authors: Goody Adam , Rice Frances , Boivin Jacky , Harold Gordon T. , Hay Dale F. , Thapar Anita
Published: May 2007

The rate of multiple births is substantially elevated in women who have had assisted reproduction treatment (ART; ˜26%) compared to the general population (˜1%), and these offspring are usually included in twin studies. Several studies have attempted to identify possible consequences of undergoing ART on the subsequent offspring. However, most studies have only included singleton births. We first examined whether twins born by ART differed from other twins on measures of childhood psychopathology, putative risk factors and correlates, and secondly tested for differences in the degree of twin similarity for available outcome measures. From a population-based twin sample, 101 families with dizygotic (DZ) twins conceived via ART were identified and compared with 1073 naturally conceived (NC) control DZ twin pairs. Analyses performed were (1) univariate and multivariate comparisons of between-group mean differences; and (2) comparison of twin 1–twin 2 correlations between the groups. The groups differed significantly on demographic factors (parental age, family size and social class) and pregnancy variables (smoking during pregnancy and birthweight) but did not differ on family conflict scores or in the frequency of obstetric complications. Family cohesion was higher in the ART group but this was accounted for by demographic factors. For child psychopathology there was a difference between the groups only for teacher-rated ADHD (Attention Deficit Hyperactivity Disorder). Differences were also found between groups for twin correlations. The differences found between ART and NC twins on group means and twin correlations suggest that researchers should be aware that including ART twins may influence results from twin studies.
Estimation of the Rate of SNP Genotyping Errors From DNA Extracted From Different Tissues
Authors: Montgomery Grant W. , Campbell Megan J. , Dickson Peter , Herbert Shane , Siemering Kirby , Ewen-White Kelly R. , Visscher Peter M. , Martin Nicholas G.
Published: May 2007

High density single nucleotide polymorphism (SNP) genotyping panels provide an alternative to microsatellite markers for genome scans. However, genotype errors have a major impact on power to detect linkage or association and are difficult to detect for SNPs. We estimated error rates with the Affymetrix GeneChip® SNP platform in samples from a family with a mixed set of monozygotic (MZ) and dizygotic (DZ) triplets using lymphocyte, buccal DNA and samples from whole genome amplification using the multiple displacement amplification (MDA) technique. The average call rate from 58,960 SNPs for five genomic samples was 99.48%. Comparison of results for the MZ twins showed only three discordant genotypes (concordance rate 99.995%). The mean concordance rate for comparisons of samples from lymphocyte and buccal DNA was 99.97%. Mendelian inconsistencies were identified in 46 SNPs with errors in one or more family members, a rate of 0.022%. Observed genotype concordance rates between parents, between parents and children, and among siblings were consistent with previously reported allele frequencies and Hardy–Weinberg equilibrium. Using the MDA technique, results for two samples had equivalent high accuracy to results with genomic samples. However, the SNP call rate for the remaining seven samples varied from 72.5% to 99.5%, with an average of 86.11%. Quality of the DNA sample following the MDA reaction appears to be the critical factor in SNP call rate for MDA samples. Our results demonstrate highly accurate and reproducible genotyping for the Affymetrix GeneChip® Human Mapping Set in lymphocyte and buccal DNA samples.
Twin Studies on Obsessive–Compulsive Disorder: A Review
Authors: van Grootheest Daniël S. , Cath Daniëlle C. , Beekman Aartjan T. , Boomsma Dorret I.
Published: May 2007

Genetic factors have historically been thought of as important in the development of obsessive–compulsive disorder (OCD). For the estimation of the relative importance of genetic and environmental factors, twin studies are an obvious approach. Twin studies of OCD have a long history, starting in 1929. In this review, over 70 years of twin research of OCD is presented, using four different approaches that represent the steps in the twin research of OCD from past to present. These steps include (1) case-studies of twins with OCD from the old literature; (2) twin studies of OCD using Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria; (3) twin studies of OCD using a dimensional approach, comparing resemblances in monozygotic and dizygotic twins; and (4) twin studies of OCD using a dimensional approach, analyzing the data with Structural Equation Modeling. It is concluded that only the studies using the last method have convincingly shown that, in children, obsessive–compulsive (OC) symptoms are heritable, with genetic influences in the range of 45% to 65%. In adults, studies are suggestive for a genetic influence on OC symptoms, ranging from 27% to 47%, but a large twin study using a bio- metrical approach with continuous data is still needed to provide conclusive evidence. Strategies for future twin studies of OCD are discussed.
Variations in the Maternal Age Effect on Twinning Rates: The Nordic Experience
Authors: Fellman Johan , Eriksson Aldur W.
Published: May 2007

Maternal age is the most important nongenetic factor influencing the twinning rate. Every study of the effect of other factors should consider the age distribution of the mothers. Besides standardizing techniques, the age-specific twinning rates are analyzed. Especially, the slope of the regression line is considered when the age-specific twinning rates are regressed against maternal age. How well the maximum age-specific twinning rate measures the variation in the maternal age effect is also studied. The two measures, which are strongly correlated, give consistent results. The proposed methods are applied to data from Finland (1866 to 2003) and Denmark (1855 to 2000). Comparisons with Sweden (1861 to 2000) and Norway (1855 to 2003) are also made. In general, marked decreasing trends in the twinning rates are discernible up to the middle of the 20th century. In Sweden the decline starts around the beginning of the 20th century and is stronger than in Denmark and Norway. The decrease in the twinning rate for Finland, which up to World War II was rather isolated, sets in around the middle of the 20th century and is not as strong as in other Nordic countries. After the minima around 1980, strong increasing trends are noted. This is mainly caused by the influence of the artificial reproduction technologies and particularly the use of fertility-enhancing drugs on the commonly noted dependence between maternal age and the twinning rate. Similar temporal trends can be observed in the slopes of the regression line and in the maximum age-specific twinning rates.
The Hispanic Paradox in Twin Pregnancies
Authors: Luke Barbara , Brown Morton B. , Misiunas Ruta B. , Gonzalez-Quintero Victor H. , Nugent Clark , van de Ven Cosmas , Witter Frank R. , Newman Roger B. , D'Alton Mary , Hankins Gary D. V. , Grainger David A. , Macones George A.
Published: May 2007

The objective of this study was to compare length of gestation, fetal growth, and birthweight by race/ethnicity and pregravid weight groups in twin pregnancies. Three thousand and thirty-six twin pregnancies of 28 weeks or more gestation were divided by race/ethnicity (White, Black and Hispanic), and pregravid body mass index (BMI) groups (less than 25.0 vs. 25.0 or more). Outcomes were modeled using multiple regression, controlling for confounders, with White non-Hispanic women as the reference group. Hispanic women had the highest average birthweight and the longest gestation, as well as the lowest proportions of low birthweight, very low birthweight, preterm and early preterm births of the 3 race/ethnicity groups. In the multivariate analyses, Hispanic women had significantly longer gestations (by 7.8 days) and faster rates of fetal growth midgestation (20 to 28 weeks, by 17.4 g/week) and late gestation (after 28 weeks, by 5.3 g/week), whereas Black women had significantly slower rates of fetal growth (by 5.7 g/week and by 4.5 g/week, respectively). These findings in twins reflect the racial and ethnic disparities previously shown in singletons, including the Hispanic paradox of longer gestations and higher rates of fetal growth.
Twin Transplants; Twin Study Summary; Human Interest Topics
Authors: Segal Nancy L.
Published: May 2007

An overview of the nature and success of organ transplantation in monozygotic (MZ) twins is presented. Recent timely examples demonstrate the unique donor–recipient relationship shared by MZ co-twins. Next, a recent analysis of MZ co-twin differences in the epigenetic profile and associations with differences in life history factors is presented. This work has been the focus of considerable attention by scientists and the media. The final section of this column summarizes information and events concerning twins' longevity, screen careers, older parenting of twins and the origin of the word ‘twin’.
Genetic Influence on Reproductive Behavior in Female Rhesus Macaques
Authors: Trefilov Andrea , Croucher Peter J. P. , Krawczak Michael , Schmidtke Jörg
Published: May 2007

Commentary on Cherkas et al. (2004). Genetic Influences on Female Infidelity and Number of Sexual Partners in Humans: A Linkage and Association Study on the Role of the Vasopressin Receptor Gene (AVPR1A). Twin Research, 7, 649–658.
Genetic Etiology of Reading Difficulties in Boys and Girls
Authors: Wadsworth Sally J. , DeFries John C.
Published: May 2007

Although it has been suggested that genetic influences on reading difficulties may differ in boys and girls, results obtained from previous analyses of data from same-sex twin pairs have failed to provide evidence for a differential genetic etiology of reading disability (RD) as a function of gender. However, results of a recent study in which data from both same-sex and opposite-sex twin pairs were analyzed indicated a higher heritability for reading difficulties in boys (Harlaar et al., 2005). Because the current sample of twin pairs tested in the Colorado Learning Disabilities Research Center is substantially larger than that analyzed for our previous report (Wadsworth et al., 2000), this hypothesis was tested more rigorously using data from both same-sex and opposite-sex twin pairs in our current augmented sample. Composite reading scores from 634 twin pairs were subjected to DeFries–Fulker sex-limitation analysis using the model-fitting approach of Purcell and Sham (2003). Analysis of data from the combined sample of male and female twins indicated that genetic influences account for more than half the proband reading deficit (h2g = .58). When this model was extended to test for gender differences in the magnitude of genetic influences on RD, h2g estimates were somewhat higher for females than for males (.63 and .53, respectively), but the difference was nonsignificant (p > .3). A test for qualitative gender differences was also nonsignificant. Thus, these results provide little evidence for a differential genetic etiology of RD in boys and girls.
Familial Clustering of Major Depression and Anxiety Disorders in Australian and Dutch Twins and Siblings
Authors: Middeldorp Christel M. , Birley Andrew J. , Cath Danielle C. , Gillespie Nathan A. , Willemsen Gonneke , Statham Dixie J. , de Geus Eco J. C. , Andrews J. Gavin , van Dyck Richard , Beem A. Leo , Sullivan Patrick F. , Martin Nicholas G. , Boomsma Dorret I.
Published: May 2007

The aim of this study was to investigate familial influences and their dependence on sex for panic disorder and/or agoraphobia, social phobia, generalized anxiety disorder and major depression. Data from Australian (N= 2287) and Dutch (N= 1185) twins and siblings who were selected for a linkage study and participated in clinical interviews to obtain lifetimeDiagnostic and Statistical Manual of Mental Disorders(4th ed.; DSM-IV) diagnoses were used. In a liability model, tetrachoric correlations were estimated in sibling pairs and sex differences between sibling correlations were tested. For each diagnosis, the sibling correlations could be constrained to be equal across the Australian and Dutch samples. With the exception of panic disorder and/or agoraphobia, all sibling correlations were the same for brother, sister and opposite-sex sibling pairs and were around .20. For panic disorder and/or agoraphobia, the correlation was .23 in brother and sister pairs, but absent in opposite-sex sibling pairs. From these results it can be concluded that upper heritability estimates, based on twice the correlations in the sibling pairs, vary between 36% (major depression) and 50% (social phobia). Furthermore, different genetic risk factors appear to contribute to the vulnerability for panic disorder and/or agoraphobia in men and women. No other sex differences were found.
A Comparison of Twin Birthweight Data From Australia, the Netherlands, the United States, Japan, and South Korea: Are Genetic and Environmental Variations in Birthweight Similar in Caucasians and East Asians?
Authors: Hur Yoon-Mi , Luciano Michelle , Martin Nicholas G. , Boomsma Dorret I. , Iacono William G. , McGue Matt , Shin Joong Sik , Jun Jong Kwan , Ooki Syuichi , van Beijsterveldt C. E. M. , Han Jung Yeol
Published: May 2007

Birthweight has implications for physical and mental health in later life. Using data from Caucasian twins collected in Australia, the Netherlands and the United States, and from East Asian twins collected in Japan and South Korea, we compared the total phenotypic, genetic and environmental variances of birthweight between Caucasians and East Asians. Model-fitting analyses yielded four major findings. First, for both males and females, the total phenotypic variances of birthweight were about 45% larger in Caucasians than in East Asians. The larger phenotypic variances were mainly attributable to a greater shared environmental variance of birth- weight in Caucasians (ranging from 62% to 67% of variance) than Asians (48% to 53%). Second, the genetic variance of birthweight was equal in Caucasians and East Asians for both males and females, explaining a maximum of 17% of variance. Third, small variations in total phenotypic variances of birthweight within Caucasians and within East Asians were mainly due to differences in nonshared environmental variances. We speculate that maternal effects (both genetic and environmental) explain the large shared environmental variance in birthweight and may account for the differences in phenotypic variance in birthweight between Caucasians and East Asians. Recent molecular findings and specific environmental factors that are subsumed by maternal effects are discussed.
Analysis of Factors Affecting Birthweight, Birth Length and Head Circumference: Study of Japanese Triplets
Authors: Yokoyama Yoshie , Sugimoto Masako , Ooki Syuichi
Published: May 2007

The aims of this study were to identify factors associated with birthweight, birth length and head circumference for triplets, and analyze these body size parameters at birth, especially head circumference, according to gestational age. The subjects of this study were 370 mothers and their 1109 triplet children (excluding one stillborn infant) who were born between 1978 and 2002. The gestational age proved to be the strongest contributing factor to birthweight, birth length and head circumference of the triplets. Moreover, sex was a significant factor affecting birthweight, birth length and head circumference. Male neonates had a higher birthweight, longer birth length and greater head circumference than female neonates. Birth order in triplets also had a significant effect on birthweight and head circumference. Lower birth- order neonates had a higher birthweight and greater head circumference. An effect of maternal pregravid body mass index (BMI) on both birth- weight and birth length was observed. The birthweights of triplets born to women whose pregravid BMIs were more than 26.0 kg/m2 weighed an average of 150 g more than those of triplets born to women whose pregravid BMIs were less than 19.8 kg/m2, and the birth length of triplets born to women whose pregravid BMIs were more than 26.0 kg/m2 averaged 1.5 cm longer than those of triplets born to women whose pregravid BMIs were less than 19.8 kg/m2. Concerning head circumference, the median head circumference of male neonates was approximately 0.5 cm longer than female neonates. Compared to singleton neonates, the median head circumference of triplets was almost the same.
Reflections on the Implementation of a Course Website Maintained by Multiple Faculty Members: Analysis, Development, Sustainability, and Evaluation
Authors: Fried Aaron P.
Published: May 2007

Sustainability is a major issue when creating Websites that students use with courses. How will content change over time, how can faculty inexperienced with Web development add to and maintain content? This article will examine an implemented sustainable Website that can be managed by everyone associated with the course.
Impact of Spatial and Temporal Variation in Calf Survival on the Growth of Elk Populations
Authors: RAITHEL JAROD D. , KAUFFMAN MATTHEW J. , PLETSCHER DANIEL H.
Published: May 2007

Abstract: The realized impact of a vital rate on population growth (λ) is determined by both the relative influence of the vital rate on λ (elasticity) and its magnitude of variability. We estimated mean survival and reproductive rates in elk (Cervus elaphus) and spatial and temporal variation in these rates from 37 sources located primarily across the Rocky Mountain region and northwestern United States. We removed sampling variance from estimates of process variance both within and across vital‐rate data sets using the variance discounting method developed by White (2000). Deterministic elasticities calculated from a population matrix model parameterized with these mean vital rates ranked adult female survival (eScow = 0.869) much higher than calf survival (eScalf = 0.131). However, process variance in calf survival was >11 times greater than process variance in female survival across data sets and 10 times greater on average within studies. We conducted Life‐Stage Simulation Analysis to incorporate both vital‐rate elasticity patterns and empirical estimates of variability to identify those vital rates most influential in elk population dynamics. The overwhelming magnitude of variation in calf survival explained 75% of the variation in the population growth rates generated from 1,000 matrix replicates, compared to just 16% of the variation in λ explained by variation in female survival. Variation in calf survival greatly impacts elk population growth and calls into question the utility of classical elasticity analysis alone for guiding elk management. These results also suggest that the majority of interannual variability that wildlife managers document in late‐winter and spring elk surveys is attributable to variation in calf survival over the previous year and less influenced by variation in the harvest of females during the preceding autumn. To meet elk population size objectives, managers should consider the inherent variation in calf survival, and its apparent sensitivity to management, in addition to female harvest.
Estimation of a Nonlinear Density‐Dependence Parameter for Wild Turkey
Authors: McGHEE JAY D. , BERKSON JAMES M.
Published: May 2007

Abstract: Although previous research and theory has suggested that wild turkey (Meleagris gallopavo) populations may be subject to some form of density dependence, there has been no effort to estimate and incorporate a density‐dependence parameter into wild turkey population models. To estimate a functional relationship for density dependence in wild turkey, we analyzed a set of harvest‐index time series from 11 state wildlife agencies. We tested for lagged correlations between annual harvest indices using partial autocorrelation analysis. We assessed the ability of the density‐dependent theta‐Ricker model to explain harvest indices over time relative to exponential or random walk growth models. We tested the homogeneity of the density‐dependence parameter estimates (θ) from 3 different harvest indices (spring harvest no. reported harvest/effort, survey harvest/effort) and calculated a weighted average based on each estimate's variance and its estimated covariance with the other indices. To estimate the potential bias in parameter estimates from measurement error, we conducted a simulation study using the theta‐Ricker with known values and lognormally distributed measurement error. Partial autocorrelation function analysis indicated that harvest indices were significantly correlated only with their value at the previous time step. The theta‐Ricker model performed better than the exponential growth or random walk models for all 3 indices. Simulation of known parameters and measurement error indicated a strong positive upward bias in the density‐dependent parameter estimate, with increasing measurement error. The average density‐dependence estimate, corrected for measurement error ranged 0.25 ≤ θC ≤ 0.49, depending on the amount of measurement error and assumed spring harvest rate. We infer that density dependence is nonlinear in wild turkey, where growth rates are maximized at 39‐42% of carrying capacity. The annual yield produced by density‐dependent population growth will tend to be less than that caused by extrinsic environmental factors. This study indicates that both density‐dependent and density‐independent processes are important to wild turkey population growth, and we make initial suggestions on incorporating both into harvest management strategies.
Influence of the Kid on Space Use and Habitat Selection of Female Alpine Ibex
Authors: GRIGNOLIO STEFANO , ROSSI IVA , BERTOLOTTO ELISA , BASSANO BRUNO , APOLLONIO MARCO
Published: May 2007

Abstract: Mammalian females change their behavior during the last stages of pregnancy and during the weaning as a response to new energetic requirements and antipredator behavior. From March 2001 to December 2004, we studied the effects of parturition and weaning on home‐range sizes and habitat selection in 28 female Alpine ibex (Capra ibex) in a 1,700‐ha free area in the Gran Paradiso National Park (Western Italian Alps). We calculated Kernel home range enclosing 95% of each female's locations according to seasonal and bimonthly timescales. Pregnancy did not seem to modify spatial behavior. Lactating females showed smaller home ranges than nonlactating ones after the birth period in June‐July. Hot summers slowed kids' growth and prolonged maternal care, modifying mothers' behavior. In summer 2003, which was hotter and drier than usual, weaning females showed even smaller home ranges. Because of their use of antipredator tactics during the weaning season, lactating females showed a higher use of safer habitats, such as rocky slopes. Our results are consistent with the findings of previous cervid and bovid studies, and they suggest that ungulate mothers may move to suboptimal, but safer, habitats during weaning to reduce the predation risk for their offspring.
Correcting Home‐Range Models for Observation Bias
Authors: HORNE JON S. , GARTON EDWARD O. , SAGER‐FRADKIN KIMBERLY A.
Published: May 2007

Abstract: Home‐range models implicitly assume equal observation rates across the study area. Because this assumption is frequently violated, we describe methods for correcting home‐range models for observation bias. We suggest corrections for 3 general types of home‐range models including those for which parameters are estimated using least‐squares theory, models utilizing maximum likelihood for parameter estimation, and models based on kernel smoothing techniques. When applied to mule deer (Odocoileus hemionus) location data, we found that uncorrected estimates of the utilization distribution were biased low by as much as 18.4% and biased high by 19.2% when compared to corrected estimates. Because the magnitude of bias is related to several factors, future research should determine the relative influence of each of these factors on home‐range bias.
Urban Maternity‐Roost Selection by Big Brown Bats in Colorado
Authors: NEUBAUM DANIEL J. , WILSON KENNETH R. , O'SHEA THOMAS J.
Published: May 2007

Abstract:Despite prevalent use of anthropogenic structures by bats and the associated implications for public health, management, and bat conservation, very little quantitative information exists about urban roost characteristics and their selection by bats. During the summers of 2001 to 2004 we conducted fieldwork in Fort Collins, Colorado, USA, situated on the northern end of Colorado's Front Range, to address questions of roost selection by the big brown bat (Eptesicus fuscus). The city has experienced its greatest growth in the past half century, with its population increasing by 30% in the last decade. Similar growth in new buildings has occurred, with the number of new housing permits issued annually doubling in the past decade. We located 142 roosts using radiotelemetry or by citizen calls in response to a newspaper article and flyers. To determine characteristics of roost selectivity by bats, we compared variables for known maternity roosts and randomly selected buildings at microhabitat and landscape scales using logistic regression; we used an information theoretic approach to determine which variables were most important. We considered 44 and 100 buildings in the microhabitat and landscape scale analyses, respectively. At the microhabitat scale maternity roosts had exit points with larger areas that were higher from the ground and had warmer average temperatures than randomly selected buildings. At the landscape scale distances to similarly categorized roosts were smaller, and urbanization variables such as lower building density, higher street density, and lower traffic count density were most important. Results for variables important to urban‐roosting big brown bats were often analogous to studies that characterized maternity roosts found in tree snags and rock crevices. In addition, changes in the landscape, not only in the form of anthropogenic structures but also in water availability and vegetation structure such as riparian forests, may have led to population increases and range expansions of the big brown bat. Because big brown bats appear to selectively choose specific combinations of characteristics found at maternity roosts, not all available structures can be considered suitable and exclusion from established maternity roosts may negatively impact bat populations.
Satellite Telemetry in Avian Research and Management: Sample Size Considerations
Authors: LINDBERG MARK S. , WALKER JOHANN
Published: May 2007

Abstract: Satellite tracking is currently used to make inferences to avian populations. Cost of transmitters and logistical challenges of working with some species can limit sample size and strength of inferences. Therefore, careful study design including consideration of sample size is important. We used simulations to examine how sample size, population size, and population variance affected probability of making reliable inferences from a sample and the precision of estimates of population parameters. For populations of >100 individuals, a sample >20 birds was needed to make reliable inferences about questions with simple outcomes (i.e., 2 possible outcomes). Sample size demands increased rapidly for more complex problems. For example, in a problem with 3 outcomes, a sample of >75 individuals will be needed for proper inference to the population. Combining data from satellite telemetry studies with data from surveys or other types of sampling may improve inference strength.
Home‐Range Attributes of Raccoons in a Fragmented Agricultural Region of Northern Indiana
Authors: BEASLEY JAMES C. , DEVAULT TRAVIS L. , RHODES OLIN E.
Published: May 2007

Abstract: For many wildlife species, agricultural landscapes undergo spatial and temporal fluctuations in the composition of food and cover annually with the planting and harvesting of crops. Raccoon (Procyon lotor) populations have flourished in agricultural landscapes, where crops increase foraging opportunities and efficiencies. However, information is lacking regarding the effects of temporal shifts in food and cover resulting from agricultural activities on raccoon home ranges. We examined home‐range characteristics of 60 (33 M, 27 F) adult raccoons in northern Indiana, USA, from May 2003 through June 2005 to identify shifts in the size of home ranges and core use areas among seasons defined by crop availability and crop developmental stages. Mean fixed‐kernel home‐range (92 ± 6 ha; xM ± SE) and core‐area sizes (20 ± 2 ha) of males were significantly larger than those of females (58 ± 7 ha and 13 ± 2 ha, respectively), and both were smaller than those reported for raccoons in other fragmented agricultural landscapes. Home‐range sizes varied little among seasons for either sex. However, home ranges of males were smallest during the crop maturation stage, whereas home ranges of females were smallest during the crop growing season. The results of our study suggest that even in expansive rural landscapes, raccoons can maintain small home ranges when food, water, and denning resources are readily available. Additionally, the lack of differences among seasonal home‐range sizes, despite the presence of an ephemeral superabundant food source (i.e., corn) during the maturation season, was likely due to the close proximity of foraging and denning resources across seasons.
Survival of White‐Tailed Deer Fawns in Southern Illinois
Authors: ROHM JOHN H. , NIELSEN CLAYTON K. , WOOLF ALAN
Published: May 2007

Abstract: Survival of white‐tailed deer (Odocoileus virginianus) fawns has been quantified throughout much of North America. However, few studies have assessed the influence of intrinsic factors (e.g., fawn age and birth mass) and habitat on fawn survival. During 2002‐2004, we captured and radiocollared 166 fawns in southern Illinois, USA, to estimate survival rates, determine causes of mortality, and identify factors influencing fawn survival. We used a known fates model in program MARK to estimate survival rates and compare explanatory models based on Akaike's Information Criterion corrected for small sample sizes (AICc). We developed 2 candidate sets of a priori models to quantify factors influencing fawn survival: model set 1 included intrinsic factors and model set 2 focused on habitat variables. We recorded 64 mortalities and the overall survival rate was 0.59 (95% CI = 0.51‐0.68). Predation was the leading source of mortality (64%) and coyotes (Canis latrans) were the most prominent predator. For model set 1, model {Sage X year} had the lowest AICc value suggesting that the age at mortality varied among capture years. For model set 2, model {Slandscape+forest} had the lowest AICc value and indicated that areas inhabited by surviving fawns were characterized by a few large (i.e., > 5 ha) irregular forest patches adjacent to several small nonforest patches, and survival areas also contained more edge habitat than mortality areas. Due to the magnitude of coyote predation, survival areas could have represented landscapes where coyotes were less effective at locating and capturing fawns when compared to mortality areas. This study was the first account of macrohabitat characteristics directly influencing fawn survival. Wildlife managers can use this information to determine how habitat management activities may affect deer populations.
Estimation of Abundance and Recommendations for Monitoring White‐Cheeked Pintails in Wetlands of Puerto Rico and Territorial Islands
Authors: RIVERA‐MILÁN FRANK F. , BONILLA‐MARTINEZ GILBERT
Published: May 2007

Abstract:The white‐cheeked pintail(Anas bahamensis)is listed as threatened, and survey data are needed to assess population status, estimate trends, and guide management on Puerto Rico and territorial islands. We surveyed 51 points in 29 wetland sites to estimate density and population size after the peak of reproduction (Mar‐Jul) and before the waterfowl hunting season (Nov‐Jan). Estimated density was 2.33 individuals/ha (SE = 0.27), and estimated population size was 3,755 individuals (SE = 435, log‐normal 95% CI = 2,995 to 4,708) in 1,614 ha surveyed in August‐October 2003‐2005. Density differed between August‐October 2003(Ď= 3.07 individuals/ha, SE = 0.41) and 2004(Ď= 1.26 individuals/ha, SE = 0.17) and between August‐October 2004 and 2005 (Ď = 2.54 individuals/ha, SE = 0.47) but not between August‐ October 2003 and 2005. Spatial distribution ranged from nearly random (estimate of dispersion parameter [b̌] = 0.99) to highly clumped (b̌ = 3.71). We suggest that spatiotemporal variation of wetland hydrochemical conditions caused changes in foraging resources, which in turn caused changes in white‐cheeked pintail density and spacing patterns. We recommend surveying 186 points 3 times in August‐October for estimated density to have a coefficient of variation of 0.10, even when white‐cheeked pintails are highly clustered (estimate of exp cluster size, Ě[s] = 16.1, SE = 2.8) and clumped (b= 4) in space. We provide additional recommendations for integrating monitoring, research, and management objectives to better understand the ecology and promote the conservation of white‐cheeked pintails and their habitats locally and regionally.
Chromium and Selenium in Invertebrate Prey of Lesser Scaup
Authors: WEEGMAN MITCH D. , WEEGMAN MATT M.
Published: May 2007

Abstract: The combined lesser scaup (Aythya affinis) and greater scaup (A. marila) population in North America has steadily declined from an average of 7.5 million breeding birds in the 1970s to an all‐time low of 3.39 million in 2005. Bioaccumulation is widely known as the means of elevated levels of toxins in vertebrates. Our goal was to determine whether chromium and selenium were factors contributing to the continental scaup population decline by identifying wetlands used by scaup that potentially contain dangerous concentrations of chromium and selenium. We hypothesized that zebra mussels (Dreissena polymorpha) would contain the highest concentrations of selenium and chromium because they are filter feeders, whereas amphipods would contain the lowest concentrations because of their short life span. We collected zebra mussels, fingernail clams (Sphaerium transversum), chironomid larvae, snails (Gastropoda), and amphipods on randomly selected traditional lesser scaup staging and breeding wetlands. We found higher chromium concentrations in zebra mussels from Iowa, USA, than in those from Wisconsin, USA (P = 0.0074). In addition, selenium concentrations in zebra mussels from Wisconsin were higher than in those from Iowa (P < 0.0001). Higher selenium concentrations in amphipods were associated with sampled wetlands surrounded by developed land. Invertebrates with >5 μg/g selenium and >1 μg/g chromium are potentially hazardous for scaup. Chromium concentrations in Iowa were the highest for most species examined, whereas they were the lowest in Minnesota, USA. Based on our results, lesser scaup probably accumulate the highest concentrations of selenium on Lake Onalaska, Wisconsin, whereas they probably accumulate the lowest concentrations in Iowa. Waterfowl biologists are searching for explanations to the scaup decline; we propose chromium and selenium concentrations in amphipods and fingernail clams may be a factor.