Length-biased Sampling Research Papers - Academia.edu (original) (raw)

Dietary investigations of sympatric felids are means for understanding how closely related species deal with food resources in a potentially competitive scenario. The diets of the oncilla Leopardus tigrinus, the jaguarundi Puma... more

Dietary investigations of sympatric felids are means for understanding how closely related species deal with food resources in a potentially competitive scenario. The diets of the oncilla Leopardus tigrinus, the jaguarundi Puma yagouaroundi and the ocelot Leopardus pardalis were studied through the analysis of scats in Araucaria Pine Forest with Natural Grasslands of southern Brazil. Small mammals comprised the bulk of the diets of the three felids, followed by birds and reptiles. The smallest food-niche overlap index was 0.84, indicating that these felids shared an important portion of their food resources. Inter-species differences were detected in the consumption of the most frequent rodent prey; L. tigrinus was the only species that consumed all the most frequent rodent prey differently from the rate expected from their abundances. Although these findings suggest competitive interactions, with the oncilla being the most subordinate species, further experimental investigations are necessary to elucidate more precisely how these syntopic felids coexist. The effects of sample size and its influences on the evaluation of the diets of the felids, especially of the ocelot, are discussed. We compare our data to a previous study in the same area, to account for the possible influences of biased sampling and uneven distribution of food resources on the diet of the ocelot. The opportunistic feeding behavior and the abundance of their primary prey (cricetid rodents) seem to allow these small cats to be resilient despite severe anthropogenic disturbance in the study area. We further suggest guidelines for future studies in the study region, in order to understand the dynamics of mammalian carnivores demography.

One of the challenges in studying HIV-risk behaviors among gay men is gathering information from a non-biased sample, as traditional probability sampling methods cannot be applied in gay populations. Respondent-Driven Sampling (RDS) has... more

One of the challenges in studying HIV-risk behaviors among gay men is gathering information from a non-biased sample, as traditional probability sampling methods cannot be applied in gay populations. Respondent-Driven Sampling (RDS) has been proposed as a reliable and bias-free method to recruit “hidden” populations, such as gay men. The aim of this study is to assess the feasibility and effectiveness of RDS to sample Latino gay men and transgender persons. This was carried out when we used RDS to recruit participants into a study that investigated community involvement on HIV/AIDS sexual risk behaviors among Latino gay and bisexual men, and transgender (male-to-female) persons in Chicago and San Francisco. The population coverage of RDS was then compared to simulated time-location sampling (TLS). Recruitment differences were observed across cities, but the samples were comparable. RDS showed broader population coverage than TLS, especially among individuals at high risk for HIV.

When the probability of selecting an individual in a population is proportional to its magnitude, it is called length biased sampling. Length-biased sampling (LBS) situations may occur in biological studies, clinical trials, reliability,... more

When the probability of selecting an individual in a population is proportional to its magnitude, it is called length biased sampling. Length-biased sampling (LBS) situations may occur in biological studies, clinical trials, reliability, queuing models, survival analysis and population studies where a proper sampling frame is absent. In such situations items are sampled at rate proportional to their length so that larger values of the quantity being measured are sampled with higher probabilities. In this note, we present a test to detect ...

This paper presents 75 new radiocarbon dates based on late Quaternary mammal remains recovered from eastern Taimyr Peninsula and adjacent parts of the northern Siberian lowlands, Russian Federation, including specimens of woolly mammoth... more

This paper presents 75 new radiocarbon dates based on late Quaternary mammal remains recovered from eastern Taimyr Peninsula and adjacent parts of the northern Siberian lowlands, Russian Federation, including specimens of woolly mammoth (Mammuthus primigenius), steppe bison (Bison priscus), muskox (Ovibos moschatus), moose (Alces alces), reindeer (Rangifer tarandus), horse (Equus caballus) and wolf (Canis lupus). New evidence permits reanalysis of megafaunal extinction dynamics in the Asian high Arctic periphery. Increasingly, radiometric records of individual species show evidence of a gap at or near the Pleistocene/Holocene boundary (PHB). In the past, the PHB gap was regarded as significant only when actually terminal, i.e., when it marked the apparent “last” occurrence of a species (e.g., current “last” occurrence date for woolly mammoth in mainland Eurasia is 9600 yr bp ). However, for high Arctic populations of horses and muskoxen the gap marks an interruption rather than extinction, because their radiocarbon records resume, nearly simultaneously, much later in the Holocene. Taphonomic effects, ΔC14 flux, and biased sampling are unlikely explanations for these hiatuses. A possible explanation is that the gap is the signature of an event, of unknown nature, that prompted the nearly simultaneous crash of many megafaunal populations in the high Arctic and possibly elsewhere in Eurasia.