Knowing kill rate is essential for knowing the basic nature of predation. We compared estimates of kill rate for previously observed wolf-prey systems with new observations from wolves Canis lupus ...which preyed on white-tailed deer Odocoileus virginianus in Michigan, USA. For the five packs that we studied during 2001-2004, the mean kill rate was 0.68 kill/pack/day (∼7.7 kg/wolf/day). However, kill rates varied considerably. In particular, the coefficient of variation associated with the means was 0.55 for kills/pack/day and 0.68 for kg/wolf/day. Our analysis of previously observed kill rates also revealed a negative correlation between the duration of observation and the estimated kill rate. This correlation is the basis for showing how most published estimates of kill rate for wolves during winter tend to overestimate, by 50%, the season-long average kill rate during winter. The negative association between duration of observation and estimated kill rate occurs, in part, because wolves are unable to maintain very high kill rates for a long time. We also document how estimates of kill rate based on ground tracking tended to be 3.3 times greater than aerial-based estimates (2.4 vs 7.9 kg/wolf/day). Ground tracking is better able to detect multiple carcasses at one site, and better able to detect carcasses when wolves bed far from their kills. These previously undocumented biases are surprising given that wolves are so extensively studied.
In conservation and management of large predators, effects of species are often considered separately. However, predators often interact with one another in different ways (e.g. interspecific ...competition, intra guild predation and kleptoparasitism) that may influence the total predation on a common prey. We estimated the total number of semi-domestic reindeer Rangifer tarandus killed by Eurasian lynx Lynx lynx and wolverine Gulo gulo at different relative abundances of the two species using a model based on diet, food requirements of lynx and wolverine and amount of food available on a reindeer. Our model suggests that total predation decreases by approximately 7.9% (± 4.8 SD) if wolverines scavenge on lynx-killed reindeer, compared to a model without scavenging. If the management goal is a constant number of predators, the model suggests that the total kill rate will be lowest in areas with only wolverines, as the estimated wolverine kill rate is much lower than the lynx kill rate. Our model showed that it is unlikely that the lowest number of reindeer killed per predator individual will be at a certain lynx-wolverine ratio, which would appear if lynx consumption of killed reindeer is low and wolverines are very efficient finding lynx-killed reindeer. However, if the management goal is a constant number of lynx and wolverines, the model suggests that the total predation is lower, if lynx and wolverines coexist in the same area compared to existing separately in different areas. The total predation by wolverine and lynx on reindeer is very important for the management of lynx and wolverine in the reindeer husbandry area in Sweden, as the current compensation scheme for predator-killed semi-domestic reindeer is based on the number of predators present within a reindeer herding district, and the compensation for wolverine and lynx is added independently of one another.
1. In regions where sheep are kept in fenced pastures and do not graze unattended in carnivore habitats, sheep losses vary greatly between sites and livestock farms. To assess the factors that may ...predispose farms to lynx predation in the French Jura, we compared sheep availability and environmental characteristics between pastures with and without attacks in a 1800-km2study area. Nine lynx were radio-tracked in the same area for a total of 21 lynx years to estimate individual killing rates on sheep and to identify possible habitual livestock killers. 2. Depending on individual and year, lynx predation rate on sheep within lynx home ranges varied between 0 and 12·4 attacks 100 days-1. Predation rate on sheep was not related to sheep abundance nor sheep dispersion in lynx home ranges. Two individuals became habitual sheep killers during, respectively, their third and fourth year of monitoring. Other lynx that had access to the same flocks were only occasional sheep killers. No obvious causal factor (e.g. sex, reproductive status, physical debilitation) explained the differential individual propensity for lynx to kill livestock. 3. We found no difference in sheep availability between pastures with and without attacks, but strong differences in their environmental characteristics. In only 5·1% of 98 pastures > 250 m from a forest were sheep attacked by lynx. In 228 pastures adjacent or connected to forests by cover, 39·1% sustained attacks on sheep by lynx (P < 0·01). For these latter pastures, logistic regression showed a positive effect of their proximity to major forested areas (P < 0·01), absence of human dwellings (P < 0·01), local abundance of roe deer (P = 0·01) and the presence of attacked pastures in their vicinity (P = 0·03). 4. These results suggests that lynx damage locally can be explained by a predictable set of habitat features that expose sheep on some pastures to risk, and by an unpredictable event, i.e. an individual developing regular predation on sheep. 5. In grazing systems like the Jura, where unattended sheep are distributed patchily and individual problem lynx may appear, removing lynx or lowering density without differentiating individuals will be insufficient to limit conflicts. Selective removals could temporarily reduce predation but the site effect implies that durable management can arise only through improved shepherding. This might include guard dogs in the few local sites at risk and providing shelter for sheep at night when attacks are on the increase.
We assessed spatial and temporal variation in reporting probability of banded Greater Snow Geese (Chen caerulescens atlantica) shot by hunters in eastern North America and evaluated potential ...residual biases in kill rate estimation. Adult Greater Snow Geese were marked with reward (value: US$10, $20, $30, $50, and $100) and standard bands ($0, control) in the Canadian Arctic from 2003 to 2005. We used a spatially explicit multinomial model based on 200 direct recoveries from 4256 banded geese to estimate reporting rate and harvest rate. We found that reporting rate for standard bands varied over time whereas harvest rate was higher in Canada than in the U.S. The reporting probability increased from 0.40 + or - 0.11 in the first year of the study to 0.82 + or - 0.14 and 0.84 + or - 0.13 the second and third years, respectively. Overall, these reporting rates are higher than two previous estimates for this population, which leads to lower estimates of kill rate. However, the large annual differences in reporting rates found in this study lead to uncertainty in the estimation of kill rate. We suggest that the increase in reporting rate in the last two year of the study may be due to the dissemination of information among hunters regarding the presence of reward bands on birds, resulting in increased reporting rate for all bands. This raises issues about the need to adequately inform the public in such large-scale studies to avoid undesirable temporal trends over the course of the study.Original Abstract: Nous avons determine la variabilite spatiale et temporelle de la probabilite de retourner des bagues de Grandes Oies des neiges (Chen caerulescens atlantica) recoltees par les chasseurs dans l'Est de l'Amerique du Nord, et evalue les biais inherents potentiels dans l'estimation du taux de recolte. Les oies adultes ont ete marquees a l'aide de bagues recompense (d'une valeur de 10, 20, 30, 50 ou 100 $ US) et standards (0 $ US, temoin) dans l'Arctique canadien de 2003 a 2005. Afin d'estimer le taux de retour de bagues par les chasseurs et le taux de recolte, nous avons utilise un modele multinomial spatialement explicite fonde sur 200 recuperations directes de bagues provenant d'un ensemble de 4256 oies baguees. Nos resultats indiquent que le taux de retour par les chasseurs pour les bagues standards a varie au cours du temps, tandis que le taux de recolte etait plus eleve au Canada qu'aux Etats-Unis. La probabilite de retour de bagues par les chasseurs a augmente de 0,40 + or - 0,11 la premiere annee de l'etude a 0,82 + or - 0,14 et 0,84 + or - 0,13 les deuxieme et troisieme annees, respectivement. Ces taux de retour de bagues sont superieurs a ceux estimes precedemment pour cette population, entrainant des estimations du taux de recolte plus faibles. Toutefois, la forte variation interannuelle dans les taux de retour de bagues par les chasseurs observee dans la presente etude engendre une grande incertitude pour l'estimation du taux de recolte. Nous suggerons que l'augmentation du taux de retour de bagues observee au cours des deux dernieres annees de notre etude pourrait etre attribuable a la dissemination de l'information au sein des chasseurs quant a l'existence de bagues recompense sur les oiseaux, conduisant ainsi a une augmentation du taux de retour pour tout type de bagues. Cette etude souligne l'importance des informations a transmettre au public lors d'etudes a grande echelle afin d'eviter des tendances temporelles indesirables au cours de celles-ci.
Prey class selection and kill rates by lynx Lynx lynx were studied in the Swiss Jura Mountains from March 1988 until May 1998 to evaluate the significance of lynx predation for roe deer Capreolus ...capreolus and chamois Rupicapra rupicapra. We found clear differences in the kill rates and prey class selection between lynx of different age, sex and breeding status. Male lynx killed more chamois than female lynx, and chamois was never found in kill series of subadult lynx. Family groups had the highest kill rate. They killed an ungulate every 5.0 days, compared to an average of 6.2–6.6 days for single lynx. During our 10-year study, the density of independent lynx was rather stable, ranging within 0.94–1.01 individuals/100 km2. Based on the observed kill rates and the estimated lynx population structure we calculated that lynx killed 354 ± 13 roe deer and 87 ±13 chamois annually in the 710 km2 study area. The magnitude of lynx predation on roe deer and chamois was primarily shaped by the lynx population structure. A decline in the number of resident male lynx reduced the number of chamois killed in the study area by ¼ of the previous number due to the difference in prey selection of male and female lynx. There was a difference in the most frequently killed age and sex classes between roe deer and chamois: lynx killed more male chamois (39%) than females or fawns, whereas in roe deer, does (38%) were most often killed. By altering adult survival, lynx predation has a significant impact on prey population dynamics. Lynx killed a maximum of 9% of the roe deer and 11 % of the chamois spring population. Considering the differences in the recruitment potential of the two prey species, lynx has a greater impact on chamois than on roe deer.
This study evaluates the accuracy of two alternative models for the kill rate of different visual defects and the yield estimation by using large amount of practical inspection data (140 6-inch ...wafers containing 70 560 dies) in semiconductor manufacturing. One model assumed that the visual defects are randomly distributed on a wafer die; another model considered that clustering visual defects may occur on a wafer die. The results show that two models are both capable of predicting the yield precisely. The results also suggest that the model assuming clustering visual defects on a die is more accurate based on the analysis of Taguchi's signal-to-noise (SN) ratio. The same practices can be implemented with other types of wafer such as 8 inch and 12 inch. Precise prediction for the kill rate of different types of visual defects and the yield in the long supply of semiconductor industry is critical since the requirement of material and the reserved capacity can be largely reduced.
Networked munitions coordinated operations is an effective modern warfare method. In order to better apply the networked munitions coordinated operations effectiveness evaluation to the integrated ...analysis of actual operations, a networked munitions coordinated operations process based on effectiveness evaluation is proposed method of prediction. Analyze the characteristics of the combat plan reflecting the battlefield situation during actual combat or simulation deduction, and construct corresponding effectiveness evaluation indicators for networked ammunition operations. By collecting the target recognition rate in the process of networked ammunition coordinated operations, the target kill rate and false target attack rate are analyzed to obtain the cost-effectiveness ratio. The effectiveness evaluation index is used to accurately predict the cooperative operation process of networked ammunition to achieve the prediction requirements. The simulation results show that the prediction accuracy of the network ammunition cooperative operation process prediction method based on effectiveness evaluation is higher, and it can better realize the efficient and reliable network ammunition cooperative operation effectiveness.
Background: Various mathematical models have been proposed for studying the growth
of tumor cells under chemotherapeutic drug administration. In most of the deterministic models, the
drug is ...administered as per the rate equation of time.
Objective: In this paper we have studied the behavior of a predator-prey model when the drug infusion
rate is governed by a sinusoidal function.
Method: A logistic growth model, to study the response of tumor growth to chemotherapeutic drug
dosage is considered. The model has been suitably modified to introduce periodic drug infusion rate
which is a sinusoidal function. In this paper, an extensive sensitivity analysis on the parameters, tumor
cells division rate, cell kill rate, rate at which the drug becomes ineffective and the drug decay
rate has been carried out to determine how these parameters affect the growth of the tumor and how
the drug accumulates in the body.
Results: 1000 sets of these four parameters were randomly chosen from appropriate Gamma distributions
and corresponding curves for the number of tumor cells and average drug accumulation
have been obtained. A comparative study of drug administration at a constant rate and at a periodic
rate has been done. Effect of changes in the parameters governing the drug infusion rate have been
analyzed and how the parameters used in the model relate to pharmacokinetics and pharmacodynamics
of a drug has been pointed out.
Conclusion: We have been able to show that controlled periodic drug infusion is a better strategy
than administering the drug of a constant rate.
Within the last 3 to 5 years, many silver-based antimicrobial dressings have become available and more are on the way. However, sometimes dressing manufacturers and authors make claims and send ...messages that conflict with data and conclusions in the literature, creating confusion for clinicians. A literature review of six relevant and frequently discussed topics was conducted. Pre-clinical and clinical study data suggest that: a) bacterial resistance to silver may occur, b) silver dissociation is affected by the test medium used, c) bactericidal activity differences may be a function of the bacterial strain used for testing, d) higher rather than lower levels of silver may be needed because Ag+ binds to proteins and nucleic acids, e) rapid delivery of silver (ie, rate of kill) may be a positive factor when considering prevention of silver resistance and biofilm formation, and f) based on the vast majority of in vivo studies available, silver does not adversely effect viable cells; thus, is not cytototoxic. Continued research into the implications of the data is warranted.
The impact of antibiotics on health care likely exceeds that of any other class of drugs by greatly reducing the likelihood of debilitating disease and/or death prevalent in the preantibiotic era. ...However, the coincidence of (1) medicinal chemists’ continuing struggle to produce druggable antibiotics with novel targets that overcome emergence of drug resistance altogether, (2) the general decline of active development of new antimicrobial agents, (3) the prevalence (and growth because of increased use) of antimicrobial resistance to legacy molecules, and (4) the ever-present threat of bioterrorism, mean that antibiotic drug development must necessarily focus on resistance counter-measures throughout the discovery and development process. Thus, in essence, antiinfective discovery and development programs are (or should be) intrinsically charged with the combined responsibility of minimization of resistance selection and targeting drug resistant infections from the outset.
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