Divergent estimates of herd-wide caribou calf survival: Ecological factors and methodological biases

Population monitoring is a critical part of effective wildlife management, but methods are prone to biases that can hinder our ability to accurately track changes in populations through time. Calf survival plays an important role in ungulate population dynamics and can be monitored using telemetry and herd composition surveys. These methods, however, are susceptible to unrepresentative sampling and violations of the assumption of equal detectability, respectively. Here, we capitalized on 55 herd-wide estimates of woodland caribou (Rangifer tarandus caribou) calf survival in Newfoundland, Canada, using telemetry (n = 1,175 calves) and 249 herd-wide estimates of calf:cow ratios (C:C) using herd composition surveys to investigate these potential biases. These data included 17 herd-wide estimates replicated from both methods concurrently (n = 448 calves and n = 17 surveys) which we used to understand which processes and sampling biases contributed to disagreement between estimates of herd-wide calf survival. We used Cox proportional hazards models to determine whether estimates of calf mortality risk were biased by the date a calf was collared. We also used linear mixed-effects models to determine whether estimates of C:C ratios were biased by survey date and herd size. We found that calves collared later in the calving season had a higher mortality risk and that C:C tended to be higher for surveys conducted later in the autumn. When we used these relationships to modify estimates of herd-wide calf survival derived from telemetry and herd composition surveys concurrently, we found that formerly disparate estimates of woodland caribou calf survival now overlapped (within a 95% confidence interval) in a majority of cases. Our case study highlights the potential of under-appreciated biases to impact our understanding of population dynamics and suggests ways that managers can limit the influence of these biases in the two widely applied methods for estimating herd-wide survival.

Geometry of the ideal free distribution: individual behavioural variation and annual reproductive success in aggregations of a social ungulate

Variation in social environment can mitigate risks and rewards associated with occupying a particular patch. We aim to integrate Ideal Free Distribution (IFD) and Geometry of the Selfish Herd (GSH) to address an apparent conflict in their predictions of equal mean fitness between patches (IFD) and declining fitness benefits within a patch (GSH). We tested these hypotheses in a socio-spatial context using individual caribou that were aggregated or disaggregated during calving and varied in their annual reproductive success (ARS). We then tested individual consistency of these spatial tactics. We reveal that two socio-spatial tactics accorded similar mean ARS (IFD); however, ARS for aggregated individuals declined near the periphery (GSH). Individuals near the aggregation periphery exhibited flexibility, whereas others were consistent. The integration of classical theories through a contemporary lens of consistent individual differences provides evidence for an integrated GSH and IFD strategy that may represent an evolutionary stable state.

SimSurvey: An R package for comparing the design and analysis of surveys by simulating spatially-correlated populations

Populations often show complex spatial and temporal dynamics, creating challenges in designing and implementing effective surveys. Inappropriate sampling designs can potentially lead to both under-sampling (reducing precision) and over-sampling (through the extensive and potentially expensive sampling of correlated metrics). These issues can be difficult to identify and avoid in sample surveys of fish populations as they tend to be costly and comprised of multiple levels of sampling. Population estimates are therefore affected by each level of sampling as well as the pathway taken to analyze such data. Though simulations are a useful tool for exploring the efficacy of specific sampling strategies and statistical methods, there are a limited number of tools that facilitate the simulation testing of a range of sampling and analytical pathways for multi-stage survey data. Here we introduce the R package SimSurvey, which has been designed to simplify the process of simulating surveys of age-structured and spatially-distributed populations. The package allows the user to simulate age-structured populations that vary in space and time and explore the efficacy of a range of built-in or user-defined sampling protocols to reproduce the population parameters of the known population. SimSurvey also includes a function for estimating the stratified mean and variance of the population from the simulated survey data. We demonstrate the use of this package using a case study and show that it can reveal unexpected sources of bias and be used to explore design-based solutions to such problems. In summary, SimSurvey can serve as a convenient, accessible and flexible platform for simulating a wide range of sampling strategies for fish stocks and other populations that show complex structuring. Various statistical approaches can then be applied to the results to test the efficacy of different analytical approaches.

Implementing a novel movement-based approach to inferring parturition and neonate caribou calf survival

In ungulates, parturition is correlated with a reduction in movement rate. With advances in movement-based technologies comes an opportunity to develop new techniques to assess reproduction in wild ungulates that are less invasive and reduce biases. DeMars et al. (2013, Ecology and Evolution 3:4149-4160) proposed two promising new methods (individual- and population-based; the DeMars model) that use GPS inter-fix step length of adult female caribou (Rangifer tarandus caribou) to infer parturition and neonate survival. Our objective was to apply the DeMars model to caribou populations that may violate model assumptions for retrospective analysis of parturition and calf survival. We extended the use of the DeMars model after assigning parturition and calf mortality status by examining herd-wide distributions of parturition date, calf mortality date, and survival. We used the DeMars model to estimate parturition and calf mortality events and compared them with the known parturition and calf mortality events from collared adult females (n = 19). We also used the DeMars model to estimate parturition and calf mortality events for collared female caribou with unknown parturition and calf mortality events (n = 43) and instead derived herd-wide estimates of calf survival as well as distributions of parturition and calf mortality dates and compared them to herd-wide estimates generated from calves fitted with VHF collars (n = 134). For our data, the individual-based method was effective at predicting calf mortality, but was not effective at predicting parturition. The population-based method was more effective at predicting parturition but was not effective at predicting calf mortality. At the herd-level, the predicted distributions of parturition date from both methods differed from each other and from the distribution derived from the parturition dates of VHF-collared calves (log-ranked test: χ2 = 40.5, df = 2, p < 0.01). The predicted distributions of calf mortality dates from both methods were similar to the observed distribution derived from VHF-collared calves. Both methods underestimated herd-wide calf survival based on VHF-collared calves, however, a combination of the individual- and population-based methods produced herd-wide survival estimates similar to estimates generated from collared calves. The limitations we experienced when applying the DeMars model could result from the shortcomings in our data violating model assumptions. However despite the differences in our caribou systems, with proper validation techniques the framework in the DeMars model is sufficient to make inferences on parturition and calf mortality.

Bird communities and vegetation associations across a treeline ecotone in the Mealy Mountains, Labrador, which is an understudied part of the boreal forest

We examined the factors structuring bird communities across a complex subarctic treeline in the Mealy Mountains, Labrador, Canada. Using point counts of bird abundance in 2007 and 2008, we show that changes in vegetation driven by elevation are strongly correlated with avian community structure in this treeline ecotone system. Overall, avian diversity was higher in the forest compared with other habitat classes (krummholz, deciduous shrub, and alpine). There were strong correlations between avian diversity and vegetation richness, as well as structure, among and within habitat class in 2008. Numerous habitat types (subset of habitat class) were correlated with avian composition, although some species were clearly habitat generalists. Contrary to expectation, avian species composition was associated with physiognomy (vegetation structure) in alpine and deciduous shrub, and with either physiognomy or floristics (vegetation species composition) in krummholz and forest. Given the strong impact of elevation on vegetation and the demonstrated influence on bird communities, we note that for bird species whose near-southernmost populations are found in the Mealy Mountains, climate change is likely to have a strong negative effect if alpine tundra habitat is lost. Furthermore, forest bird species are likely to benefit from the increased tree cover as treeline moves poleward and upward.

Prophylactic amrinone for weaning from cardiopulmonary bypass

This prospective, randomised, double-blind, controlled clinical study was performed at a single tertiary referral centre to test the hypothesis that the prophylactic administration of amrinone before separation of a patient from cardiopulmonary bypass decreases the incidence of failure to wean, and to identify those patients who could be predicted to benefit from such pre-emptive management. Two hundred and thirty-four patients, scheduled to undergo elective cardiac surgery, were randomly allocated to receive either a bolus dose of 1.5 mg x kg(-1) amrinone over 15 min, followed by an infusion of 10 microg x kg(-1) x min(-1), or a bolus of placebo of equal volume followed by an infusion of placebo. Treatment with amrinone or placebo was initiated upon release of the aortic cross-clamp, before weaning from cardiopulmonary bypass. Anaesthetic technique, monitoring and myocardial preservation methods were standardised for both groups. Significantly fewer patients failed to wean in the group that received prophylactic amrinone than in the control group (7 vs. 21%, p = 0.002). Amrinone improved weaning success regardless of left ventricular ejection fraction, although this benefit was statistically significant only in the group with left ventricular ejection fractions > 55%. Of the 32 patients who failed to wean from cardiopulmonary bypass, 14 had normal pre-operative left ventricular ejection fractions.

An experimental soft-release of oil-spill rehabilitated American coots (Fulica americana): I. Lingering effects on survival, condition and behavior

In spring 1995, we studied survival, condition and behavior of 37 oiled/rehabilitated (OR) American coots (Fulica americana) (RHB) and compared them to 38 wild-caught, non-oiled and non-rehabilitated coots (REF). All coots were wing-clipped to prevent long-range dispersal, mixed equally and randomly and soft-released into two fenced marshes. Twenty RHB+20 REF coots were subjected to handling and sampling four times during the 4-month study and the remainder were left undisturbed. The study ended before any coots dispersed following remige regrowth. Overall survival was significantly lower for RHB coots, regardless of the way survival was viewed (four Chi 2 tests varied between p<0.045 and p<0.006). Mortality was 2.1 times higher in RHB coots: 51% mortality in RHB coots and 24% in REF coots (4 months total). RHB coots began the experiment 9% lighter in mean body condition indices (BCI=a standardization that corrected for different-sized birds) than REF coots, but REF coots also needed a period of adjustment to captivity. BCIs then varied (p<0.02) similarly among both groups throughout the experiment. Initially, RHB coots lost more weight in comparison to REF coots (although RHB coots fed more), but those RHB coots that did survive recovered to REF-comparable BCIs after about 6 weeks: both higher and equivalent at the beginning of moult and then both equivalent but lower through the moulting period. Long-term RHB coot and REF coot survivors both had significant (p<0.001) positive correlations between their initial and ending body weights. A similar relationship was also suggested for the non-surviving REF coots, but could not be tested for statistical significance. In contrast to all other groups, however, non-surviving RHB coots failed to show any relationship between their initial and ending body weights (p>0.10), indicating that non-surviving RHB coots were unable to gain or maintain body condition for about 2-3 months following their oiling/rehabilitation experience. Throughout the experiment, RHB coots preened more on water and on land, bathed more, slept less during the day, and exhibited feeding and drinking behaviors more frequently or of greater duration than REF coots (all statistical tests with Bonferroni-corrected p<0.05).

Pharmacology

When performing IVCS, one must never forget the primary goal of providing patient comfort without compromising cardiopulmonary function or the patient's ability to react purposely to verbal commands and physical stimuli. When it is anticipated that required sedation will lead to loss of protective airway reflexes, such patients require a greater level of care than exists with IVCS. Deep sedation is a complication of IVCS and must be avoided. In deep sedation, one creates a state of depressed consciousness from which the patient is not easily aroused, accompanied by a partial or complete loss of protective reflexes, including the ability to maintain a patent airway independently and respond purposely to physical stimuli or verbal commands. In keeping this goal in mind, understanding those situations in which patients are at increased risk should be emphasized. In general, the elderly show increased sensitivity to the drugs used for IVCS, so the dose and frequency of administration should be reduced. In addition, patients with COPD appear to be more sensitive to the respiratory depressant effects of narcotics and benzodiazepines, especially when used in combination. Patients with low serum albumin concentrations show increased sensitivity to drugs that are highly protein bound such as thiopental because more free drug is available for therapeutic effect. To avoid hypotention, caution should be exercised in patients with poor left ventricular function or borderline volume status before the administration of IVCS. Understanding the metabolism and excretion of the agents used for IVCS is critical to avoid oversedation. Drugs such as diazepam, morphine, meperidine, and fentanyl have active metabolites, so the potential for drug accumulation and prolonged effect certainly exists. Patients with renal disease are particularly susceptible to CNS toxicity from normeperidine because of the accumulation of the active metabolite. Drugs like fentanyl, although short acting, have prolonged activity as a result of seepage of stored drug back into the systemic circulation. In contrast, thiopental is metabolized to water-soluble inactive metabolites. Careful titration to effect with dosage adjustments will avoid unnecessary oversedation with resultant respiratory and cardiovascular complications. Time should elapse between repeat doses to allow peak effects to occur. In addition, potential drug interactions that can prolong the effects should be recognized. Examples of the latter are the interaction between cimetidine and diazepam or the protease inhibitors and the benzodiazepines, in which the potential exists for excessive and prolonged sedation. The use of the narcotic antagonist naloxone and the benzodiazepine antagonist flumazenil should be scrutinized because they should be reserved for the unusual situation in which excessive cardiopulmonary depression occurs. Maintenance of a patent airway and stable cardiovascular function in a patient who can respond to verbal commands and physical stimuli is the primary goal of IVCS. With the agents discussed in this chapter, this goal is easily obtained, keeping the principles just mentioned in mind with all the appropriate monitoring guidelines discussed elsewhere in this text.

Types of anesthesia and cardiovascular outcomes in patients with congestive heart failure undergoing vascular surgery

BACKGROUND. Whether regional anesthesia is preferable to general anesthesia for patients with congestive heart failure (CHF) undergoing noncardiac surgery remains controversial. The purpose of this study was to determine whether anesthetic technique affects postoperative cardiac outcome in patients with CHF; we hypothesized that cardiac outcomes would be superior with regional anesthesia compared with general anesthesia. DESIGN. 106 patients with prior or persistent CHF, undergoing femoral to distal artery bypass surgery, were randomized to general anesthesia (29 patients) or regional anesthesia (epidural, 42 patients, or spinal anesthesia, 35 patients). The primary end point was death or adverse cardiac events (myocardial infarction, unstable angina, or CHF). RESULTS. There was no statistically significant difference between groups in incidence of combined cardiac events, death, myocardial infarction, death or myocardial infarction combined, unstable angina, or CHF. CONCLUSION. Although larger studies are required to establish equivalence of the anesthetic strategies, this large single center study preliminarily indicates that regional anesthesia may not be superior to general anesthesia in patients with heart failure undergoing femoral to distal artery bypass surgery. (c)1999 by CHF, Inc.

Predation on different-sized quail eggs in an artificial-nest study in western Newfoundland

In artificial-nest studies, Japanese Quail (Coturnix japonica) eggs have been used as surrogates for passerine eggs, although small mammals that prey on passerine eggs may be unable to consume Japanese Quail eggs. To determine the influence of egg size on nest predation in different landscapes on insular Newfoundland, we placed either a Japanese Quail egg or a smaller Chinese Painted Quail (Xexcalfactoris chinensis) egg in artificial ground nests along lakeshore forest edges and along riparian buffer strips. Clay eggs were used to identify nest predators. Levels of predation on nests with Japanese Quail and Chinese Painted Quail eggs were similar. Based on clay eggs, predation was attributed to red squirrels (Tamiasciurus hudsonicus), and we found no evidence that smaller mammals preyed on artificial nests. We conclude that the Japanese Quail egg is acceptable for use in artificial-nest studies in Newfoundland, and we discuss the implications of egg size and small mammals in nest-predation experiments.

Services that nursing facilities should provide to residents with MS: a survey of health professionals

This study identified care-related services, programs, and equipment that nursing facilities should provide to residents with multiple sclerosis (MS). Two sets of surveys were used to collect the perspectives and opinions of 140 health professionals representing a variety of disciplines. Frequency tabulations of all responses were done by computer for 10 correlated categories to identify the most frequently mentioned services or programs in each category. Stratified frequency tabulations also were done in the medical, rehabilitation, nursing, as well as psychological and social service categories of care that nursing facilities should provide to residents with MS. The health professionals identified mental health-related services as the most important care that nursing facilities should provide to residents with MS, followed by physical therapy, recreational therapy, occupational therapy, and neurological care.

Anesthesia type does not influence early graft patency or limb salvage rates of lower extremity arterial bypass

PURPOSE

The effect of anesthesia type on 30-day graft patency and limb salvage rates was evaluated in patients who underwent femoral to distal artery bypass.

METHODS

Of 423 patients randomly assigned to receive general, spinal, or epidural anesthetic, 76 did not meet protocol standards and 32 had inadequate anesthesia. A chart review of the remaining 315 patients was undertaken to obtain surgical information not recorded in the original study. All patients were monitored with radial and pulmonary artery catheters. After surgery, patients were in a monitored setting for 48 to 72 hours and had graft function assessments hourly during the first 24 hours and then every 8 hours until discharge.

RESULTS

Fifty-one patients were lost to follow-up (15 general, 22 spinal, 14 epidural). Baseline clinical characteristics were similar for the three groups except prior carotid artery surgery, which was more common in the spinal group. Indications for surgery were also similar except for a higher incidence of nonhealing ulcer in the epidural group. There were no differences among groups for 30-day graft patency with or without reoperation, 30-day graft occlusion, death, amputation, or length of hospital stay.

CONCLUSION

These results suggest that the type of anesthetic given for femoral to distal artery bypass does not significantly affect 30-day occlusion rate, limb salvage rate, or hospital length of stay.

Spinal anesthesia reduces oxygen consumption in diabetic patients prior to peripheral vascular surgery

BACKGROUND AND OBJECTIVES

The purpose of this study was to evaluate the effect of spinal anesthesia in VO2 in a uniform high-risk patient population and also the relationship between dermatomal level of block and VO2, neither of which has been investigated previously.

METHODS

The effect of spinal anesthesia on VO2 was studied in 17 diabetic patients undergoing lower limb peripheral vascular surgery. Measurements were made before and 15 minutes after administration of a tetracaine spinal anesthetic. Values for VO2 and oxygen delivery (DO2) were derived from cardiac output as measured by thermodilution, hemoglobin concentration, and arterial and mixed venous blood gas analysis. The dermatomal level of the sensory block was determined by use of a hand-held nerve stimulator.

RESULTS

Mean VO2 decreased by 27.7% (P = .001) (95% confidence limits, decrease of 22.4-90.4%). Mean DO2 and arterial blood gases were unchanged, and the mean postspinal oxygen extraction ratio (VO2/DO2) decreased by 20.5% (P = .002) (95% confidence limits, decrease of 9.1-32.3%). There was a relationship between changes in VO2 and sensory block height (P = .029).

CONCLUSIONS

Spinal anesthesia in diabetic patients is associated with a reduction in VO2, the extent of which appears to be, at least in part, a function of the level of spinal sensory block.

Cardiac outcome after peripheral vascular surgery. Comparison of general and regional anesthesia

BACKGROUND

Despite evidence that regional anesthesia may be associated with fewer perioperative complications than general anesthesia, most studies that have compared cardiac outcome after general or regional anesthesia alone have not shown major differences. This study examines the impact of anesthetic choice on cardiac outcome in patients undergoing peripheral vascular surgery who have a high likelihood of associated coronary artery disease.

METHODS

Four hundred twenty-three patients, between 1988 and 1991, were randomly assigned to receive general (n = 138), epidural (n = 149), or spinal anesthesia (n = 136) for femoral to distal artery bypass surgery. All patients were monitored with radial artery and pulmonary artery catheters. Postoperatively, patients were in a monitored setting for 48-72 h and had daily electrocardiograms for 4-5 days and creatine phosphokinase/isoenzymes every 8 h x 3, then daily for 4 days. Cardiac outcomes recorded were myocardial infarction, angina, and congestive heart failure.

RESULTS

Baseline clinical characteristics were not different between anesthetic groups. Overall, the patient population included 86% who were diabetic, 69% with hypertension, 36% with a history of a prior myocardial infarction, and 41% with a history of smoking. Cardiovascular morbidity and overall mortality were not significantly different between groups when analyzed by either intention to treat or type of anesthesia received. In the intention to treat analysis, incidences of cardiac event or death for general, spinal, and epidural groups were 16.7%, 21.3%, and 15.4%, respectively. The absolute risk difference observed between general and all regional anesthesia groups for cardiac event or death was -1.6% (95% confidence interval -9.2%, 6.1%) This reflected a nonsignificant trend for lower risk of postoperative events with general anesthesia.

CONCLUSIONS

The choice of anesthesia, when delivered as described, does not significantly influence cardiac morbidity and overall mortality in patients undergoing peripheral vascular surgery.

Use of dynamic two-dimensional transesophageal echocardiography for renal cell carcinoma with cavoatrial tumor thrombus

Renal cell carcinoma with inferior vena caval tumor thrombus extending to the level of the right atrium occurs in about 1% of all cases. Dynamic two-dimensional transesophageal echocardiography is a minimally invasive safe technique that can demonstrate preoperatively the cephalad extent of the cavoatrial tumor thrombus with an accuracy that appears equal to or better than that of any other method currently available. When used intraoperatively, it provides invaluable data to aid in the anesthetic and surgical management of the patient, obviating the need for and potential risk of placing a Swan-Ganz pulmonary artery catheter before complete removal of the tumor thrombus.

Early intervention of inotropic support in facilitating weaning from cardiopulmonary bypass: the New England Deaconess Hospital experience

The current article reviews the therapeutic advantages and disadvantages of early inotropic intervention prior to separation from cardiopulmonary bypass (CPB). Background information is provided on predictors of failure to wean as well as the multiple etiologies and consequences of the "failed wean" from CPB. Advantages of early inotropic intervention include (1) increased contractility, (2) resolution/prevention of ischemia, (3) attainment of therapeutic levels of drug, (4) minimization of inotropic side effects while on CPB, (5) avoidance of mechanical intervention (intra-aortic balloon pump), (6) dilatation of the internal mammary artery, and (7) prevention of the "failed wean". Disadvantages of early inotropic intervention include (1) unnecessary drug usage, (2) tachycardia/arrhythmias, (3) hyper/hypotension, (4) metabolic disturbances (hyperglycemia), (5) coagulation disorders, (6) need for additional drugs to treat side effects, (7) possible myocardial damage, and (8) additional costs. A brief review of this institution's preference for amrinone follows, including its pharmacology, side effects, and dosing prior to separation from CPB. Due to the large percentage of patients with diabetes mellitus undergoing cardiac surgery at our institution (approximately 30% to 40%) a synopsis of special inotropic considerations for this patient population is included.

Safety of saline irrigation for angioscopy: results of a prospective randomized trial

This study evaluates the hemodynamic effects and safety of saline irrigation necessary to obtain high-quality completion angioscopic studies, as compared with standard completion arteriography during infrainguinal bypass grafting. One-hundred ten patients undergoing primary infrainguinal bypass grafting, were prospectively randomized to either arteriography (N = 50) or angioscopy (N = 60) for a completion study to monitor the bypass procedure. All patients were hemodynamically monitored with pulmonary artery catheters and arterial lines. The arteriography group received an average of 27 ml (range 8-60 ml) of contrast per completion study, with a total administered intraoperative fluid volume of 2095 ml (range 650-4000 ml). The angioscopy group received an average bolus of 321 ml (range 90-650 ml) of irrigation fluid per completion angioscopy study, with a total administered intraoperative fluid volume of 2140 ml (range 850-5000 ml). Transient increases in pulmonary artery systolic and diastolic pressures and central venous pressures were measured during angioscopy. Although these changes reached statistical significance, the changes were of minimal clinical relevance, 1.9 (= 4.5), 1.6 (= 3.0) and 1.4 (= 2.3) mmHg respectively, and returned to baseline levels within 30 minutes. Intraoperative intervention with vasodilators and diuretics, the perioperative cardiac morbidity, and less than 30 day mortality, was not different between the two groups. Pressures generated within 24 bypass grafts were within physiologic arterial range for most of the study. With careful angioscopic technique applied and high quality care extended to the patient, irrigation with saline solution is simple, effective and safe.

Pharmacist's effect on digoxin usage and toxicity

Digoxin usage and toxicity were compared in a prospective group of patients who were monitored by a pharmacist and a retrospective group for which there was no pharmacist consultation. For the prospective group, the pharmacist monitored patients and estimated the steady-state digoxin levels by the use of a nomographic method. Level greater than 2.2 ng/ml and concurrent ECG or physical signs of digoxin toxicity were communicated to the physician. For the retrospective group, digoxin levels were calculated based on data from the patients' charts. The 49 patients in the two study groups were categorized according to four levels of digoxin toxicity (ranging from "no evidence" to "probable"). The only characteristic that was significantly different between the two groups was the calculated creatinine clearance (lower for the retrospective group). The maintenance dose of digoxin and the incidence of digoxin toxicity were significantly lower in the prospective group. It is concluded that pharmacist intervention may have had an effect in reducing digoxin dosage and toxicity.