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1.
Understanding survival and cause-specific mortality of native and translocated animals can help biologists design more effective recovery programs. We estimated survival rates for 181 native mountain quail (Oreortyx pictus) in west-central Idaho from 1992 to 1996 and for 199 translocated mountain quail in western Idaho and eastern Washington in 2005 and 2006. Spring–summer survival of native birds over 4 yr ranged from 0.210 (SE = 0.116) to 0.799 (SE = 0.103) and fall–winter survival in 2 yr was 0.523 (SE = 0.089) and 0.244 (SE = 0.084). Annual survival rates were 0.418 (SE = 0.088) and 0.174 (SE = 0.065). Spring–summer survival rate of translocated birds was 0.215 (SE = 0.044) in 2005 and 0.059 (SE = 0.021) in 2006. We modeled biweekly survival as a function of sex, age, movement rate, native versus translocated status, and linear time trend, and then we added year and 3 weather covariates (mean biweekly precipitation and maximum and minimum temperatures). Year and climate variables improved the a priori top model which included movement rate and native versus translocated status. Higher mortality rates due to predation coincided with movements to breeding habitat in late winter, periods of higher temperatures in the spring and summer, and periods of higher precipitation and colder temperatures during the fall–winter seasons. High movement rates of native birds in winter to avoid snow and by translocated birds when dispersing may have led to greater exposure to predators and consequently lower survival rates. Mountain quail can experience low and variable survival, stressing the potential need for multiple years of releases in restoration efforts in the eastern portion of their range. More attention is needed to identify optimal habitat (including nest sites) for restoring mountain quail populations to reduce movements, lower mortality risks, and provide conditions for withstanding periods of unfavorable weather. © 2011 The Wildlife Society.  相似文献   

2.
ABSTRACT Long-term population declines and habitat reductions have increased concern over the status of the lesser prairie-chicken (Tympanuchus pallidicinctus). Robust estimates of demographic parameters are essential for identifying population declines and planning effective management. We evaluated the effects of age and season on the survival of female lesser prairie-chickens at 2 sites in southwestern Kansas, USA. Using telemetry data from a 7-year field study (from 1997 to 2003), we estimated seasonal (Apr—Sep) and annual (Apr—Mar) survival. We also examined daily survival rates of females attending nests during the 26-day incubation period and young during the 14-day early brood-rearing period. We evaluated the probable mortality causes of radiomarked birds by examining evidence at recovery sites. We captured 227 female lesser prairie-chickens (87 yearlings, 117 ad, and 23 age undetermined) and fitted them with radiotransmitters. Estimates of 12-month survival were lower among yearlings (Ŝ12 = 0.429, SE = 0.117) and adults at site I (Ŝ12 > = 0.302, SE = 0.080) than among yearlings (Ŝ12 = 0.588, SE = 0.100) and adults at site II (Ŝ12 > = 0.438, SE = 0.083). The patterns in timing of mortality and age-specific 6-month survival were consistent with those of 12-month estimates at site I from 1998 to 2002, with a peak in mortality during May and June. Females tending to nests or to prefledged chicks had lower daily survival (DŜRtend = 0.993, SE = 0.001) than females not involved in these activities (DŜRfailedbreeder = 0.997, SE = 0.002). We recorded 92 mortalities from April 1997 to March 2003, and 59% and 11% were attributed to predation by mammals and raptors, respectively. Our research suggests that predation during the nesting season can have a major impact on lesser prairie-chicken demography, and conservation efforts should focus on enhancing female survival during the nesting and brood-rearing seasons.  相似文献   

3.
Aspergillosis (a fungal disease) is affecting sea fan corals Gorgonia spp. throughout the Caribbean. To measure the impact of this disease, we established longitudinal, or in other words individual-based, monitoring studies on 3 reefs in the Florida Keys, USA, to obtain estimates of incidence, rates of disease progress, recovery, and mortality. At Western Dry Rocks (near Key West), 40 Gorgonia ventalina colonies (20 initially healthy and 20 initially diseased) were photo-monitored between June 1996 and May 1998. Additional sea fans were visually monitored during 2 localized outbreaks at Conch (May 1998 to September 1999) and Carysfort (July 2000 to May 2001) reefs located in the Upper Keys. Data from Western Dry Rocks showed that over a 2 yr period, the incidence rate was 0.58 sea fans yr(-1) and that tissue purpling can lead to tissue loss and subsequently to mortality, albeit at low frequencies. Most sea fans, once infected, maintained a low level of damage over time. Only 3 fans recovered from the disease; however 2 were subsequently re-infected. Case fatality rate was 10% (2 of 20 initially infected died), which is equivalent to 5% yr(-1). However, mortality can increase during localized outbreaks. At Conch, mortality was 46% yr(-1) among infected sea fans (compared to 8% yr(-1) at Carysfort, a less impacted site, during the same period). During an outbreak at Carysfort, mortality was 95% yr(-1) among diseased sea fans. These data clearly demonstrate the significant role aspergillosis plays in the population ecology of sea fan corals.  相似文献   

4.
The reintroduction of trumpeter swans to the north central United States appears to be a conservation success story. For the most part, population management goals have been met or exceeded. The population cannot be considered self-sustaining, however, because 90% of the swans migrate short distances to wintering sites where supplemental feeding occurs. The remaining 10% migrate longer distances to areas where adequate open water and forage occur naturally. To determine how these 2 different wintering habits might affect mortality, we used mark-resight data gathered between 2000 and 2008 to estimate and compare annual survival rates for long- and short-distance migrant swans marked in Wisconsin. Apparent annual survival rates were similar for long- (0.81, SE = 0.019) and short- (0.81, SE = 0.022) distant adult migrants but were higher for long-distance sub-adult (0.86, SE = 0.036) migrants than for short-distance sub-adult migrants (0.7, SE = 0.046). We also estimated seasonal survival of long-distance migrants to determine if the migratory periods are a time of high mortality. We found little evidence for seasonal variation in survival and estimates for both migratory and non-migratory seasons were very high (>0.97). Overall, the results suggest that little mortality occurs during migration and long-distance migrants are able to survive at rates at least equal to, but probably higher than, short-distance migrants. © 2011 The Wildlife Society.  相似文献   

5.
Fractal analysis of narwhal space use patterns   总被引:1,自引:0,他引:1  
Quantifying animal movement in response to a spatially and temporally heterogeneous environment is critical to understanding the structural and functional landscape influences on population viability. Generalities of landscape structure can easily be extended to the marine environment, as marine predators inhabit a patchy, dynamic system, which influences animal choice and behavior. An innovative use of the fractal measure of complexity, indexing the linearity of movement paths over replicate temporal scales, was applied to satellite tracking data collected from narwhals (Monodon monoceros) (n = 20) in West Greenland and the eastern Canadian high Arctic. Daily movements of individuals were obtained using polar orbiting satellites via the ARGOS data location and collection system. Geographic positions were filtered to obtain a daily good quality position for each whale. The length of total pathway was measured over seven different temporal length scales (step lengths), ranging from one day to one week, and a seasonal mean was calculated. Fractal dimension (D) was significantly different between seasons, highest during summer (D = 1.61, SE 0.04) and winter (D = 1.69, SE 0.06) when whales made convoluted movements in focal areas. Fractal dimension was lowest during fall (D = 1.34, SE 0.03) when whales were migrating south ahead of the forming sea ice. There were no significant effects of size category or sex on fractal dimension by season. The greater linearity of movement during the migration period suggests individuals do not intensively forage on patchy resources until they arrive at summer or winter sites. The highly convoluted movements observed during summer and winter suggest foraging or searching efforts in localized areas. Significant differences between the fractal dimensions on two separate wintering grounds in Baffin Bay suggest differential movement patterns in response to the dynamics of sea ice.  相似文献   

6.

Objective

The aim of this study was to present the therapeutic outcome of patients with locally advanced pancreatic cancer treated with pancreatoduodenectomy combined with vascular resection and reconstruction in addition to highlighting the mortality/morbidity and main prognostic factors associated with this treatment.

Materials and Methods

We retrospectively analyzed the clinical and pathological data of a total of 566 pancreatic cancer patients who were treated with PD from five teaching hospitals during the period of December 2006–December 2011. This study included 119 (21.0%) patients treated with PD combined with vascular resection and reconstruction. We performed a detailed statistical analysis of various factors, including postoperative complications, operative mortality, survival rate, operative time, pathological type, and lymph node metastasis.

Results

The median survival time of the 119 cases that received PD combined with vascular resection was 13.3 months, and the 1-, 2-, and 3-year survival rates were 30.3%, 14.1%, and 8.1%, respectively. The postoperative complication incidence was 23.5%, and the mortality rate was 6.7%. For the combined vascular resection group, complications occurred in 28 cases (23.5%). For the group without vascular resection, complications occurred in 37 cases (8.2%). There was significant difference between the two groups (p = 0.001). The degree of tumor differentiation and the occurrence of complications after surgery were independent prognostic factors that determined the patients’ long-term survival.

Conclusions

Compared with PD without vascular resection, PD combined with vascular resection and reconstruction increased the incidence of postoperative complications. However, PD combined with vascular resection and reconstruction could achieve the complete removal of tumors without significantly increasing the mortality rate, and the median survival time was higher than that of patients who underwent palliative treatment. In addition, the two independent factors affecting the postoperative survival time were the degree of tumor differentiation and the presence or absence of postoperative complications.  相似文献   

7.
Seasonal selection acting on the melanic polymorphism in the two-spot ladybird Adalia bipunctata was investigated in The Netherlands. An increase in melanic frequency over the spring-summer reproductive period was quantified. The selective advantage gained by melanics averaged 9%, but significant heterogeneity occurred between populations. Adult hibernation behaviour is described. The beetles when outdoors show a highly clumped distribution both between and within trees. The distribution of the morph classes between aggregations is random. Survivorship in a hibernating cohort (initial n= 1898) on a grid of 70 lime trees near Utrecht was monitored by making three counts over the winter of 1981–1982. Intense selection favouring each melanic morph occurred during December and January. The relative fitness of non-melanics was 0.55 (melanics =1). The discovery of dead beetles in late January (about 5% of total losses) and the absence of spatially density-dependent mortality were consistent with a climatic stress rather than selective predation. The period of selection was associated with very cold temperatures averaging up to 4°C below normal and an overall mortality of nearly 75%. There was no change in morph frequency, near normal temperatures and a lower mortality from February to early April. Examination of groups of nearby trees in late January strongly suggested that similar differential mortality had occurred except on some willows. This difference was probably due to the more protected hibernation sites available on these trees. Samples of hibernating cohorts at three other sites showed no evidence of differential mortality. Laboratory experiments with hibernating beetles found no difference in survivorship or rate of weight loss between starved non-melanics and melanics in temperature regimes with and without periods of adult activity. It is concluded that the intense winter selection on the study limes is probably exceptional. Examination of changes in morph frequency through the annual cycle suggests that at some sites the selection favouring melanics during reproduction is counterbalanced by selection against melanics in late summer or early autumn. The results are discussed in relation to mathematical models of cyclical selection and to other field studies including that of Timoféeff-Ressovsky (1940), who found large decreases in melanic frequency during hibernation in Berlin.  相似文献   

8.
Emerging diseases and expanding carnivore populations may have profound implications for ungulate harvest management and population regulation. To better understand effects of chronic wasting disease (CWD) and cougar (Puma concolor) predation, we studied mortality and recruitment of elk (Cervus elaphus) at Wind Cave National Park (WICA) during 2005–2009. We marked 202 elk (83 subadult M and 119 subadult and ad F) with Global Positioning System (GPS) collars, observed 28 deaths during 74,220 days of monitoring, and investigated 42 additional deaths of unmarked elk found dead. Survival rates were similar for males and females and averaged 0.863 (SE = 0.025) annually. Leading causes of mortality included hunting (0.065, SE = 0.019), CWD (0.034, SE = 0.012), and cougar predation (0.029, SE = 0.012). Marked elk killed by hunters and cougars typically were in good physical condition and not infected with CWD. Effects of mortality on population growth were exacerbated by low rates of pregnancy (subadults = 9.5%, SE = 6.6%; ad = 76.9%, SE = 4.2%) and perinatal survival (0.49, SE = 0.085 from 1 Feb to 1 Sep). Chronic wasting disease, increased predation, and reduced recruitment reduced the rate of increase for elk at WICA to approximately λ = 1.00 (SE = 0.027) during the past decade. Lower rates of increase are mitigating effects of elk on park vegetation, other wildlife, and neighboring lands and will facilitate population control, but may reduce opportunities for elk hunting outside the park. © 2011 The Wildlife Society  相似文献   

9.
B C Morton  D S Beanlands 《CMAJ》1984,131(8):889-892
Data on complication rates in a cardiac catheterization laboratory were prospectively gathered over a 6-year period. During this time 7960 catheterizations were performed. Death occurred in seven (0.1%) of the cases. The difference between the mortality rates for procedures performed with and without systemically administered heparin (0.04% and 0.2% respectively) was barely statistically significant (p less than 0.05). A significant complication occurred in 1.5% of the cases; however, most did not have long-term sequelae. No significant change in the annual rate of such complications was seen during the study period. Such a tabulation permits audit of quality of care, points out changing trends in morbidity and offers meaningful information on the safety of cardiac catheterization to referring physicians and their patients.  相似文献   

10.
IntroductionWhile neuroendocrine tumours (NETs) account for only a small proportion of cancer diagnoses, incidence has been rising over time. We examined incidence, mortality and survival over three decades in a large population-based registry study.MethodsThis retrospective study included all cases (n = 4580) of NETs diagnosed from 1986 to 2015 in Queensland, Australia. We examined directly age-standardised incidence and mortality rates. The impact on overall survival according to demographic factors and primary site was modelled using multivariable Cox proportional hazards regression (HR). Cause-specific and relative survival were estimated using the Kaplan-Meier survival function.ResultsAnnual incidence increased from 2.0 in 1986 to 6.3 per 100,000 in 2015, while mortality remained stable. The most common primary site was appendix followed by lung, small intestine and rectum. Rectal, stomach, appendiceal and pancreatic NETs had the greatest rate increase, while lung NETs decreased over the same period. Five-year cause-specific survival improved from 69.4% during 1986–1995 to 92.6% from 2006 to 2015. Survival was highest for appendiceal and rectal NETs and lowest for pancreas and unknown primary sites. The risk of dying within five years of diagnosis was about 40% higher for males (HR = 1.41, 95%CI 1.20–1.65) and significantly higher for patients aged over 40 years compared to younger patients (p < 0.001).ConclusionThis study, including 30 years of data, found significantly increasing rates of NETs and confirms results from elsewhere. Increasing survival over time in this study, likely reflects increased awareness, improvements in diagnostic imaging, greater use of endoscopy and colonoscopy, and the development of new therapies.  相似文献   

11.
Erythropoiesis-stimulating agent (ESA) responsiveness has been reported to be associated with increased mortality in hemodialysis (HD) patients. ESA requirement to obtain the same hemoglobin (Hb) level is different between HD and peritoneal dialysis (PD) patients. In this study, we investigated the impact of ESA responsiveness on mortality between both HD and PD patients. Prevalent HD and PD patients were selected from the Clinical Research Center registry for end-stage renal disease, a prospective cohort study in Korea. ESA responsiveness was estimated using an erythropoietin resistant index (ERI) (U/kg/week/g/dL). Patients were divided into three groups by tertiles of ERI. ESA responsiveness was also assessed based on a combination of ESA dosage and hemoglobin (Hb) levels. The primary outcome was all-cause mortality. A total of 1,594 HD and 876 PD patients were included. The median ESA dose and ERI were lower in PD patients compared with HD patients (ESA dose: 4000 U/week vs 6000 U/week, respectively. P<0.001, ERI: 7.0 vs 10.4 U/kg/week/g/dl, respectively. P<0.001). The median follow-up period was 40 months. In HD patients, the highest ERI tertile was significantly associated with higher risk for all-cause mortality (HR 1.96, 95% CI, 1.07 to 3.59, P = 0.029). HD patients with high-dose ESA and low Hb levels (ESA hypo-responsiveness) had a significantly higher risk of all-cause mortality (HR 2.24, 95% CI, 1.16 to 4.31, P = 0.016). In PD patients, there was no significant difference in all-cause mortality among the ERI groups (P = 0.247, log-rank test). ESA hypo-responsiveness was not associated with all-cause mortality (HR = 1.75, 95% CI, 0.58 to 5.28, P = 0.319). Our data showed that ESA hypo-responsiveness was associated with an increased risk of all-cause mortality in HD patients. However, in PD patients, ESA hypo-responsiveness was not related to all-cause mortality. These finding suggest the different prognostic value of ESA responsiveness between HD and PD patients.  相似文献   

12.
Status epilepticus (SE) is a serious neurologic emergency associated with a significant mortality. The objective of this study is to investigate its epidemiology in terms of age- and sex-specific incidences and mortality. By using the Taiwan National Health Insurance Research Database during 2000 to 2011, we identified hospitalized patients with a discharged diagnosis of SE and calculated the incidence and in-hospital mortality of SE with respect to age and sex. The overall incidence of SE was 4.61 per 100,000 person-years, which displayed a “J-shaped” distribution by age with a little higher under the age of 5 and highest over 60 years. The male-to-female rate ratio was 1.57 and it demonstrated a “mountain-shape” across ages with the peak at 45 to 49 years old. The in-hospital mortality was significantly lower in males (7.38%) than in females (11.12%) with an odds ratio of 0.64 (95% CI 0.56-0.72). Notably, the in-hospital mortality for females increased rapidly after the age of 40 to 45 years. The multivariate analysis found males had a significantly lower risk of mortality than females after, but not before, 45 years of age with an odds ratio of 0.56 (95% CI 0.49-0.65). Sex and age are crucial factors associated with the incidence and in-hospital mortality of SE. The females over 45 years of age have a higher risk of occurrence and mortality from SE. The underlying mechanism deserves further study.  相似文献   

13.
Spring harvest is a primary mortality factor for male eastern wild turkeys (Meleagris gallopavo silvestris), but the relationship between spring harvest regimes and annual survival is not well understood. We banded 462 male wild turkeys from 1989 to 2007 in southeastern Louisiana to estimate annual survival and band recovery rates relative to spring harvest. We evaluated these parameters under a liberal harvest season (3-bird limit; 1989–1997) and a reduced conservative harvest season (2-bird limit; 2000–2007). Estimated recovery rates during the liberal season were 0.75 (SE = 0.05) for adults and 0.63 (SE = 0.04) for juveniles, and recovery rates during the conservative season were 0.61 (SE = 0.04) and 0.48 (SE = 0.05) for adults and juveniles, respectively. Annual survival averaged 0.16 (SE = 0.05) and 0.43 (SE = 0.05) for adults and juveniles, respectively, during the liberal season. Conversely, during the conservative season, annual survival averaged 0.31 (SE = 0.05) and 0.56 (SE = 0.05) for adults and juveniles, respectively. Our findings suggest that bag limit reductions combined with a reduction in season length contributed to a 2-fold increase in annual survival for male wild turkeys. We contend that male wild turkeys were likely over harvested on our study area during the liberal harvest season, which contributed to exceptionally low annual survival rates. Managers should attempt to assess survival rates of male wild turkeys in harvested populations to properly manage spring harvest and develop appropriate harvest limits. © 2012 The Wildlife Society.  相似文献   

14.
ABSTRACT Reduced chick survival has been implicated in declines of greater sage-grouse (Centrocercus urophasianus) populations. Because monitoring survival of unmarked sage-grouse chicks is difficult, radiotelemetry may be an effective technique to estimate survival rates, identify causes of mortality, and collect ecological data. Previous studies have used subcutaneous implants to attach radiotransmitters to hatchlings of several species of birds with precocial young. Previous researchers who used subcutaneous implants in free-ranging populations removed chicks from the capture location and implanted transmitters at an alternate site. Because logistics precluded removing newly hatched greater sage-grouse chicks from the field, we evaluated a method for implanting transmitters at capture locations. We captured 288 chicks from 52 broods and monitored 286 radiomarked chicks daily for 28 days following capture during May and June 2001–2002. Two (>1%) chicks died during surgery and we did not radiomark them. At the end of the monitoring period, 26 chicks were alive and 212 were dead. Most (98%, 207/212) radiomarked chick mortality occurred < 21 days posthatch and predation (82%, 174/212) was the primary cause of death. Necropsies of 22 radiomarked chicks did not indicate inflammation or infection from implants, and they were not implicated in the death of any chicks. Fate of 48 chicks was unknown because of transmitter loss (n = 16), radio failure (n = 29), and brood mixing (n = 3). Overall, the 28-day chick survival rate was 0.220 (SE = 0.028). We found that mortalities related to the implant procedure and transmitter loss were similar to rates reported by previous researchers who removed chicks from capture sites and implanted transmitters at an alternate location. Subcutaneous implants may be a useful method for attaching transmitters to newly hatched sage-grouse chicks to estimate survival rates, identify causes of mortality, and collect ecological data.  相似文献   

15.
Cohort‐based, partial life tables were constructed to determine the sources and rates of mortality factors affecting Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on cotton in the eastern Mediterranean region of Turkey over a two year period. Mortality factors were recorded as due to predation, parasitism, dislodgement and unknown for five developmental stages. Across 10 independent cohorts, the highest median rate of marginal mortality pooled over all stages was attributed to parasitism (0.69) followed by predation (0.67). The key factor was hypothesized to be parasitism based on graphical and regression‐based comparison of individual factor k‐values to total generational mortality. The greatest amount of marginal immature mortality occurred during the fourth nymphal stadium (median = 0.77) and mortality during this stage was also most predictive of variation in total mortality. Pooled over all developmental stages, the highest rates of irreplaceable mortality were associated with parasitism (median: 0.112), followed by predation (0.088), dislodgement (0.020) and unknown (0.017). Although crawler mortality was not explicitly measured, sensitivity analyses indicated that mortality during this stage would have changed total mortality by only 0.45–1.21% and had no effect on identification of key factors. There was no significant effect of cotton cultivar on any mortality factor or total mortality over the two years of study. Results suggest that conservation of natural enemies, particularly parasitoids, may provide for more sustainable management of B. tabaci on cotton in Turkey.  相似文献   

16.
In this controlled multicentre trial treatment with either streptokinase or heparin was allocated at random to patients suffering from myocardial infarction of less than 24 hours'' duration. Treatment with either drug was standardized and lasted for 24 hours. A total of 764 patients entered the trial; 34 patient charts were rejected (including all 28 charts from one centre) because of data failure. On retrospective analysis of the 730 remaining patients the two groups were found to have been comparable at the start.The total hospital mortality was 18·5% of 373 patients allotted to streptokinase treatment and 26·3% of 357 given herapin. The mortality after infusion (24 hours) was 10·6% of 340 patients treated with streptokinase and 17·8% of 320 given herapin (P=0·011). Reinfarction in hospital after the 24-hour period of infusion occurred significantly less often in patients treated with streptokinase (P=0·036). Bleeding from puncture sites and pyrexia occurred more frequently during streptokinase treatment.After exclusion of those patients whose diagnosis was unconfirmed on retrospective assessment, the total hospital mortality rate was 19·0% of 357 patients treated with streptokinase and 27·4% of 339 treated with heparin (P=0·011). These results indicate that in recent myocardial infarction streptokinase was superior to heparin in reducing mortality and reinfarction rate during an average period of six weeks in hospital.  相似文献   

17.
The aim of this investigation was to analyze secular trend of mortality from cerebrovascular diseases in Croatia and its regional characteristics. The research comprised all deaths from cerebrovascular diseases in Croatia in persons aged between 35 and 74 years over the period 1958-1997. The investigated period is divided in eight 5-year periods, and for that 5-year periods proportional mortality rates, standardized mortality rates and specific mortality rates, according to the age and gender were calculated. Number of all deaths in the population aged 35-74 in Croatia, by 5-year periods rose from 18,913 to 26,788 (increase of 42%), deaths from cerebrovascular diseases from 2831 to 3959 (increase of 40%). Proportional mortality rate for this disease increased from 9.0% in the first 5-year period to 14.8% in the last 5-year period (increase of 64%). Standardized mortality rates for cerebrovascular diseases increased from 118 to 206 per 100,000 inhabitants (increase of 75%). The specific mortality rates over a 5-year period have shown a trend of increase in all men age groups and stagnation or decrease in women age groups. At the same time the rates standardized by age and sex increased by 62%. Standardized mortality rates for cerebrovascular diseases in continental communities (Osijek, Varazdin) are much higher (twice or even threefold) than those in coastal communities (Split, Rijeka). A data analysis showed that, although mortality trends of cerebrovascular diseases stagnated or even declined in some communities during the recent years, the secular trend for the entire country had a tendency of constant rise over the whole period of research. Therefore, the short-term prognosis predicts further increase of both the number and rates of deaths from cerebrovascular diseases in our country.  相似文献   

18.
Animal populations are becoming increasingly exposed to human activity as human populations expand and demand for energy resources (e.g., coal, oil and natural gas) increases. We initiated this study to document survival and cause-specific mortality patterns of female Rocky Mountain elk (Cervus elaphus) exposed to increasing levels of human activity. We fitted 184 females with VHF or GPS collars over 4 years and used the Kaplan–Meier survival estimator to calculate annual survival rates. We used multinomial logistic regression to assess differences in cause-specific mortality and generalized linear mixed models to determine how probability of survival was structured during hunting season; both analyses examined a suite of 5 covariates (i.e., age, year, extent of space use, cover, and human footprint) as potentially influencing cause-specific mortality and survival probability. Annual probability of survival averaged 0.8 (±0.02 SE) over 4 years but averaged 0.91 (±0.03 SE) when harvest mortality was excluded, which was the most significant source of mortality in most years ( [`(x)] = 0.13 ±0.02 \textSE \bar{x} = 0.13 \pm 0.02\,{\text{SE}} ). We found no difference between cause-specific mortality sources relative to elk that survived during the hunting season (χ 102 = 5.79, P = 0.832). The probability of a female surviving during hunting season was negatively influenced by age, year, extent of space use, cover, and human footprint. We found evidence that human activity may have influenced annual rates of natural survival (i.e., exclusive of hunting mortality) and probability of survival during the hunting season. We note that this study occurred largely on privately owned and managed residential and ranch land and focused on female elk; we acknowledge that survival rate and cause-specific patterns of mortality may vary as a function of land ownership (private vs. public), demographic status, and management and harvest practices. While temporal and spatial scales of 1 week may be sufficient to describe patterns of direct mortality during hunting season, broad temporal or spatial scale analyses may be needed to address natural mortality during other seasons.  相似文献   

19.
During the recent Mediterranean epizootic of bluetongue, an extensive programme of serological and vector (Culicoides biting midges (Diptera: Ceratopogonidae)) surveillance was carried out across Sicily. This paper presents the analysis of 911 light trap catches collected at the times of peak Culicoides abundance (summer to autumn 2000-2002) in 269 sites, in order to produce detailed maps of the spatial distribution of the main European vector, Culicoides imicola Kieffer and that of potential novel vectors. Whereas C. imicola was found at only 12% of sites, potential novel vectors, Culicoides obsoletus group Meigen, Culicoides pulicaris Linnaeus and Culicoides newsteadi Austen were present at over 50% of sites. However, the spatial distribution of C. imicola showed the closest correspondence to that of the 2000 and 2001 bluetongue (BT) outbreaks and its presence and abundance were significant predictors of the probability of an outbreak, suggesting that it was the main vector during these years. Although C. imicola may have played a role in transmission in several sites near Paternó, it was absent from the majority of sites at which outbreaks occurred in 2002 and from all sites in the province of Messina. All three potential novel vectors were widespread across sites at which outbreaks occurred during 2002. Of these, C. newsteadi was an unlikely candidate, as it was significantly less prevalent in outbreak vs. non-outbreak sites in Messina. It is hypothesized that the yearly distribution and intensity of outbreaks is directly attributable to the distribution and abundance of the vectors involved in transmission during each year. When C. imicola operated as the main vector in 2000 and 2001, outbreaks were few in number and were restricted to coastal regions due to low abundance and prevalence of this species. In 2002, it is hypothesized that BTV transmission was handed over to more prevalent and abundant novel vector species, leading to numerous and widespread outbreaks and probably to overwintering of the virus between 2001 and 2002. Based on catch ranges in outbreak vs. non-outbreak sites, it is tentatively suggested that nightly catches of 400 or more C. obsoletus and 150 or more C. pulicaris allow BTV transmission at a site, and provide a strategy for a fuller examination of the relationship between BTV transmission and the abundance and distribution of different vector species.  相似文献   

20.
Holbrook SJ  Schmitt RJ 《Oecologia》2003,135(4):532-541
Local abundance and dynamics of sedentary species with a dispersing life stage reflect factors that influence input and loss rates to patches of suitable habitat. For reef fishes, more attention has focused on sources of variation in input (larval settlement) than on patterns and causes of subsequent losses. We estimated spatial and temporal variation in juvenile mortality of a tropical damselfish, yellow-tail dascyllus (Dascyllus flavicaudus; Pomacentridae), using a fixed density experiment that was repeated 5 times at the same eight mid-lagoon localities at Moorea, French Polynesia. There was little temporal variation in the overall percent of outplanted fish lost in 48 h among five time periods (range: 32-37%), whereas there was substantial variation among the sites in the average percent lost (range: 16-56%). Differences in loss rates among the sites were highly consistent among the time periods. Densities of predators of juvenile dascyllus varied substantially among the eight sites and were highly correlated with loss rate of dascyllus. We used the empirically derived relationship between predator density and damselfish loss rate to predict the loss rate of dascyllus at four additional sites, and there was excellent agreement between the predicted and observed loss rates. There was a strong positive relationship between predator densities at the 12 sites and structural attributes of the reefs that do not change on a fast time scale, suggesting why there was strong spatial and weak temporal variation in mortality rates, with no interaction between spatial and temporal variation. Natural settlement rates of yellow-tail dascyllus and of a close congener (humbug dascyllus, D. aruanus) varied among the sites, and settlement of the two species was inversely correlated (r=-0.68). Settlement of these species was not statistically correlated with variation in mortality rate, but there was a weak trend for settlement of yellow-tail dascyllus to be greater at sites with higher mortality (r=0.27), and for settlement of humbug dascyllus to be greater at sites with lower mortality (r=-0.32). We calculated that even these weak co-variances could reduce (yellow-tail dascyllus) or increase (humbug dascyllus) the spatial variance in density of 48-h-old recruits arising at settlement by 19 and 27% respectively. Taken together, the findings suggest that the interactions between and relative contributions of input and loss processes can differ substantially over a scale of a few kilometers, resulting in a mosaic of local patches characterized by different abundances and dynamics.  相似文献   

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