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At least 1,117 records · Page 62Linked to original sources

Microbial infections in a declining wild turkey population in Texas

A survey was conducted at 5 locations in Texas for avian pathogens that might adversely affect wild turkey ( Meleagris gallopavo ) productivity and survival. At 1 site, the Rob and Bessie Welder Wildlife Refuge (WWR), turkeys have declined precipitously in recent years. During the winters of 1983-85, 442 wild turkeys were caught with cannon and drop nets, 161 of these on WWR. Blood samples were drawn for serologic evaluation, and cloacal and tracheal swabs were collected for isolation attempts. Salmonella spp. bacteria, Newcastle disease virus (NDV), and avian influenza virus (AIV) were not detected in any samples tested. Serologic tests for antibodies to NDV and AIV also were negative. Many mycoplasma isolates were recovered from turkeys from every location. Characterization of these isolates indicated that several species were present. None were species typically associated with mycoplasmosis in domestic turkeys, such as Mycoplasma gallisepticum (MG), M. meleagridis (MM), or M. synoviae (MS), although antibodies to these pathogens were detected in turkeys at every location sampled. There was no evidence to link any of these disease causing agents to the decline observed in the population of wild turkeys on the WWR.

Texas↗

Winter fasting and refeeding effects on urine characteristics in white-tailed deer

The effects of dietary protein, fasting, and refeeding on urinary characteristics of 9 captive, female white-tailed deer ( Odocoileus virginianus ) were studied from 23 February to 3 May 1984. Urinary sodium (na) and potassium (K) were diminished in fasted deer after 2 and 4 weeks. Renal excretion of Na and K were lower, whereas urinary phosphorus (P) was higher in fasted deer compared to deer fed high protein-high energy (HPHE) diets. Urinary P excretion of the fasted deer was also greater than in a low protein-high energy (LPHE)-fed group. Urinary area excretion of fasted deer was similar to that of deer fed low and high protein diets. One fasted deer died during the study and exhibited notably high excretion of urea, Na, K, and calcium (Ca). No effects of the 2 levels of dietary protein on urinary characteristics were detected. Urinary Na:C and K:C ratios wer significantly correlated with Na and K intake. Urinalysis has potential as a sensitive means of monitoring the nutritional status of white-tailed deer. Data are presented as reference values for interpretation of data from deer under less controlled circumstances.

Minnesota↗

Effects of winter fasting and refeeding on white-tailed deer blood profiles

This study examined the effects of dietary protein, fasting, and refeeding on blood characteristics of 9 nonpregnant, female white-tailed deer ( Odocoileus virginianus ) in captivity from 23 February to 3 May 1984. Percent weight loss was greater in fasted deer than in deer fed diets of 2 crude protein levels. Fasting effects were also observed for hemoglobin (Hb), red blood cell (RBC) counts, packed cell volume (PCV), cholesterol, triglycerides, serum urea nitrogen (SUN), potassium (K), glucose, phosphorus (P), insulin, thyroxine (T4), and total protein (TP). Refeeding influenced cholesterol, sodium (Na), and calcium (Ca). Hemoglobin, PCV, Ca, P, and albumin varied with time in fasted deer. Changes over time in the fed deer occurred for several hematological and serum characteristics. Data are presented to serve as reference values for better understanding of data collected from free-ranging deer under less known conditions.

Minnesota↗

Survival of young American alligators on a Florida lake

A capture-recapture study was conducted on Orange Lake, Florida, from 1979 through 1984 to estimate survival rates of young in an American alligator ( Alligator mississippiensis ) populations. Hatchlings remained together in sibling groups (pods) for at least their 1st year and then began to disperse during their 2nd spring and summer. Mortality through mid-November of their 1st year was negligible. Jolly-Seber (JS) survival estimates of hatchlings for 6 and 12 months were 76 and 41%, respectively. The 2-year JS estimate for the 1980 cohort was 8%. Minimum-Known-Alive (MKA) survival values were 72 and 46% of JS estimates for 6 months and 1 year of age. Survival during the 2nd 6 months of life (spring-summer) tended to be lower than survival during the 1st 6 months (fall-winter).

Florida↗

Effects of heptachlor- and lindane-treated seed on Canada geese

A study of Canada geese (B. canadensis) was conducted in the Pacific Northwest from 1978 through 1981. Lowered reproductive success, mortality of adults, and a population decline of resident western Canada geese (B. c. moffitti) at the Umatilla National Wildlife Refuge (Umatilla NWR) Oregon and Washington [USA] were associated with the use of heptachlor-treated wheat. Analyses of eggs and tissues from dead geese provided strong evidence that heptachlor was responsible for the mortality and decreased production. Residues of heptachlor epoxide (HE) in brains of B. c. moffitti found dead in 1978 and 1979 equalled or exceeded the lethal hazard zone of 8-9 .mu.g/g in experimental passerine birds; HE residues of > 10 .mu.g/g in sample eggs were associated with low nest success. The breeding population of Canada geese at Umatilla decreased from 129 pairs in 1974 to about 100 pairs in 1979. The heptachlor problem was restricted to the Umatilla area; HE residues were low in tissues and eggs collected at other sites in Oregon, Washington and Idaho. In Sept., 1979, the use of heptachlor-treated seed was banned in a 1700-km2 area that encompassed both sides of the Columbia River near Umatilla. Lindane was substituted for heptachlor in the restricted area in 1979, and its use was extended to much of the Columbia Basin in 1981. Concurrently, reproductive success of geese increased, mortality decreased, and the nesting population increased to 170 pairs by 1983. There was no evidence for either biomagnification of lindance residues from treated seed to goose tissues or eggs or for induction of adverse effects by this compound.

Oregon, Washington↗

Physiological condition of autumn-banded mallards and its relationship to hunting vulnerability

An important topic of waterfowl ecology concerns the relationship between the physiological condition of ducks during the nonbreeding season and fitness, i.e., survival and future reproductive success. We investigated this subject using direct band recovery records of mallards ( Anas platyrhynchos ) banded in autumn (1 Oct-15 Dec) 1981-83 in the Mississippi Alluvial Valley (MAV) [USA]. A condition index, weight (g)/wing length (mm), was calculated for each duck, and we tested whether condition of mallards at time of banding was related to their probability of recovery during the hunting season. In 3 years, 5,610 mallards were banded and there were 234 direct recoveries. Three binary regression model was used to test the relationship between recovery probability and condition. Likelihood-ratio tests were conducted to determine the most suitable model. For mallards banded in autumn there was a negative relationship between physical condition and the probability of recovery. Mallards in poor condition at the time of banding had a greater probability of being recovered during the hunting season. In general, this was true for all ages and sex classes; however, the strongest relationship occurred for adult males.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗

Northern pintail body condition during wet and dry winters in the Sacramento Valley, California

Body weights and carcass composition of male and female adult northern pintails ( Anas acuta ) were investigated in the Sacramento Valley, California, from August to March 1979-82. Pintails were lightweight, lean, and had reduced breast, leg, and heart muscles during August-September. Ducks steadily gained weight after arrival; and body, carcass (body wt minus feathers and gastrointestinal content), fat protein, and muscle weights peaked in October-November. Fat-free dry weight remained high but variable the rest of the winter, whereas body and carcass weight and fat content declined to lows in December or January, then increased again in February or March. Gizzard weights declined from early fall to March. Males were always heavier than females, but females were fatter (percentage) than males during mid-winter. Mid-winter body weight, carcass fat, and protein content were significantly (P < 0.01) lower in the dry winter of 1980-81 than in 2 wet winters (1979-80 and 1981-82). Changes in pintail body weight and composition during winter are probably adaptations to mild climate, predictable food supplies, and requirements for pair formation and molt.

California↗

Geographic variation in band reporting rates for mallards based on reward banding

We conducted a reward band study on mallards ( Anas platyrhynchos ) to estimate and test hypotheses about sources of variation in band reporting rate. We banded 25,398 mallards with standard and 100 reward bands (3 mallards banded with standard bands for every reward-banded mallard) during preseason (Jul-Sep), 1988. We used a series of multinomial models to model the resulting 2,776 band recoveries from 1988 to 1991. Estimates of reporting rate for males shot in 10 harvest areas ranged from 0.29 to 0.46 and averaged 0.38 (SE = 0.020). We found evidence ( P < 0.01) of geographic variation in reporting rates, but not of smooth latitudinal or longitudinal gradients. There was evidence ( P = 0.07) of lower reporting rates for females than males, especially in prairie Canada and the Central Flyway. Except for young males in the northern Atlantic Flyway, estimated harvest rates were lower than historical estimates, as expected from recent restrictive hunting regulations. Patterns of geographic and agesex variation in harvest rates were similar to those obtained using historical band-recovery data.

Journal of Wildlife Management↗

Robustness of survival estimates from radio-telemetry studies with uncertain relocation of individuals

Traditional methods of estimating survival from radio-telemetry studies use either the Trent-Rongstad approach (Trent and Rongstad 1974, Heisey and Fuller 1985) or the Kaplan-Meier approach (Kaplan and Meier 1958; Pollock et al. 1989 a , b ). Both methods appear to require the assumption that relocation probability for animals with a functioning radio is 1. In practice this may not always be reasonable and, in fact, is unnecessary. The number of animals at risk (i.e., risk set) can be modified to account for uncertain relocation of individuals. This involves including only relocated animals in the risk set instead of also including animals not relocated but that were seen later. Simulation results show that estimators and tests for comparing survival curves should be based on this modification.

Journal of Wildlife Management↗

Reproductive performance of female Alaskan caribou

We examined the reproductive performance of female caribou ( Rangifer tarandus granti ) in relation to age, physical condition, and reproductive experience for 9 consecutive years (1987-95) at Denali National Park, Alaska, during a period of wide variation in winter snowfall. Caribou in Denali differed from other cervid populations where reproductive performance has been investigated, because they occur at low densities (≥0.3/km 2 ) and experience high losses of young to predation. Females first gave birth at 2-6 years old; 56% of these females were 3 years old. Average annual natality rates increased from 27% for 2-year-olds to 100% for 7-year-olds, remained high for 7-13-year-olds (98%), and then declined for females ≥14 years old. Females ≥2 years old that failed to reproduce were primarily sexually immature (76%). Reproductive pauses of sexually mature females occurred predominantly in young (3-6 yr old) and old (≥14 yr old) females. Natality increased with body mass for 10-month-old females weighed 6 months prior to the autumn breeding season (P = 0.007), and for females >1 year old and weighed during autumn (late Sep-early Nov; P = 0.003). Natality for 2-, 3-, 4-, and 6-year-olds declined with increasing late-winter snowfall (Feb-May; P ≤ 0.039) during the winter prior to breeding. In most years, a high percentage of sexually mature females reproduced, and lactation status at the time of breeding did not influence productivity the following year. However, following particularly high snowfall during February-September 1992, productivity was reduced in 1993 for cows successfully rearing calves to autumn the previous year. High losses of calves to predators in 1992 may have increased productivity in 1993. Losses of young-of-the-year to predation prior to the annual breeding season can be an important influence on subsequent productivity for ungulate populations where productivity varies with lactation status of females at the time of breeding.

Journal of Wildlife Management↗

Interpreting carnivore scent-station surveys

The scent-station survey method has been widely used to estimate trends in carnivore abundance. However, statistical properties of scent-station data are poorly understood, and the relation between scent-station indices and carnivore abundance has not been adequately evaluated. We assessed properties of scent-station indices by analyzing data collected in Minnesota during 1986-03. Visits to stations separated by <2 km were correlated for all species because individual carnivores sometimes visited several stations in succession. Thus, visits to stations had an intractable statistical distribution. Dichotomizing results for lines of 10 stations (0 or ≥ 1 visits) produced binomially distributed data that were robust to multiple visits by individuals. We abandoned 2-way comparisons among years in favor of tests for population trend, which are less susceptible to bias, and analyzed results separately for biogeographic sections of Minnesota because trends differed among sections. Before drawing inferences about carnivore population trends, we reevaluated published validation experiments. Results implicated low statistical power and confounding as possible explanations for equivocal or conflicting results of validation efforts. Long-term trends in visitation rates probably reflect real changes in populations, but poor spatial and temporal resolution, susceptibility to confounding, and low statistical power limit the usefulness of this survey method.

Minnesota↗

Causes and rates of mortality of swift foxes in western Kansas

Knowledge of mortality factors is important for developing strategies to conserve the swift fox (Vulpes velox), a species being considered for listing under the Endangered Species Act, but available information about swift fox mortality is inadequate. We used radiotelemetry techniques to examine the magnitude and causes of mortality of swift fox populations in 2 study areas in western Kansas. One study area was predominantly cropland, the other rangeland. Mortality rates, calculated using Kaplan-Meier estimation techniques in a staggered entry design, were 0.55 ?? 0.08 (5 ?? SE) for adult and 0.67 ?? 0.08 for juvenile swift foxes. We did not detect differences between study areas in mortality rates for adults or juveniles. Predation by coyotes (Canis latrans) was the major cause of mortality for adult and juvenile swift foxes in both study areas, and vehicle collision was an important mortality factor for juveniles in the cropland study area. No mortality was attributed to starvation or disease.

Journal of Wildlife Management↗

Red-shouldered hawk broadcast surveys: Factors affecting detection of responses and population trends

Forest-nesting raptors are often difficult to detect and monitor because they can be secretive, and their nests can be difficult to locate. Some species, however, respond to broadcasts of taped calls, and these responses may be useful both in monitoring population trends and in locating nests. We conducted broadcast surveys on roads and at active red-shouldered hawk ( Buteo lineatus ) nests in northcentral Minnesota to determine effects of type of call (conspecific or great horned owl [ Bubo virginianus ]), time of day, and phase of the breeding cycle on red-shouldered hawk response behavior and to evaluate usefulness of broadcasts as a population monitoring tool using area occupied-probability-of-detection techniques. During the breeding seasons of 1994 and 1995, we surveyed 4 10-station road transects 59 times and conducted 76 surveys at 24 active nests. Results of these surveys indicated conspecific calls broadcast prior to hatch and early in the day were the most effective method of detecting red-shouldered hawks. Probability of detection via conspecific calls averaged 0.25, and area occupied was 100%. Computer simulations using these field data indicated broadcast surveys have the potential to be used as a population monitoring tool.

Minnesota↗

Evaluation of transmitter attachment techniques on growth of wild turkey poults

We compared the effects on growth of backpack-mounted and surgically implanted radiotransmitters used as marking techniques in studies of wild turkey ( Meleagris gallopavo ) poult survival. We applied repeated-measures analysis of variance (ANOVA) and Bayesian analysis to evaluate the null hypothesis that marking technique did not affect growth. Growth in body mass was similar among treatment groups. We did, however, find differences in wing-growth rates among treatment groups. The control group had the highest wing-growth rate, the backpack group had the lowest growth rate, and the surgical implant group was intermediate. Latex backpack harnesses also caused physical developmental problems that would have negatively biased wild poult survival estimates in the field. Surgically implanted transmitters affected wing growth less than the backpack harnesses and are therefore recommended for attaching transmitters to wild turkey poults.

Journal of Wildlife Management↗