A simple alternative to line transects of nests for estimating orangutan densities

We conducted a validation of the line transect technique to estimate densities of orangutan (Pongo pygmaeus) nests in a Bornean swamp forest, and compared these results with density estimates based on nest counts in plots and on female home ranges. First, we examined the accuracy of the line transect method. We found that the densities based on a pass in both directions of two experienced pairs of observers was 27% below a combined sample based on transect walks by eight pairs of observers, suggesting that regular line-transect densities may seriously underestimate true densities. Second, we compared these results with those obtained by nest counts in 0.2-ha plots. This method produced an estimated 15.24nests/ha, as compared to 10.0 and 10.9, respectively, by two experienced pairs of observers who walked a line transect in both directions. Third, we estimated orangutan densities based on female home range size and overlap and the proportion of females in the population, which produced a density of 4.25-4.5 individuals/km2 . Converting nest densities into orangutan densities, using locally estimated parameters for nest production rate and proportion of nest builders in the population, we found that density estimates based on the line transect results of the most experienced pairs on a double pass were 2.82 and 3.08 orangutans/km2, based on the combined line transect data are 4.04, and based on plot counts are 4.30. In this swamp forest, plot counts therefore give more accurate estimates than do line transects. We recommend that this new method be evaluated in other forest types as wel

Characteristics of white-chinned petrels Procellaria aequinoctialis Linnaeus in New Zealand waters : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Ecology at Massey University, Palmerston North, New Zealand

Current taxonomy of the white-chinned petrel suggests that all populations are similar enough to be a single global taxon, Procellaria aequinoctialis Linnaeus. This thesis challenges that view with an analysis of morphological characteristics of white-chinned petrels from fisheries bycatch in the New Zealand Exclusive Economic Zone (EEZ). The two main aims were: first, to determine if white-chinned petrels in New Zealand waters comprise one taxon; and second, to determine if white-chinned petrels in New Zealand waters fit the proposition of a global taxon. Morphological characteristics included: standard external measurements (head, bill, tarsus, wing and tail measurements), descriptions (area of white on the chin and bodily descriptions), and measurements of internal organs of a sample of 723 bycatch white-chinned petrels. Twenty-five white-chinned petrel study skins from breeding islands in the South Pacific. Indian and Atlantic Oceans, and 29 study skins from birds caught off Chile were also measured for comparison with the bycatch birds. I compared a range of external measurements from the bycatch sample taken by myself and 'the Laboratory' (measurements and descriptions of white-chinned petrels taken by C.J.R. Robertson and E. Bell) to estimate the measurement error between multiple observers measuring the same sample of birds. Results clearly showed very little measurement error between the two observers, and the small amount of error was biologically insignificant. I found two cluster groups of bycatch white-chinned petrels, the 'Antipodes Island group' (n = 105) which was significantly larger in most external measurements than the 'Auckland Island group' (n = 45). Using discriminant analysis I could differentiate 93% males of the 'Antipodes Island group' versus the 'Auckland Island group' based on culmen and tail length. I could also differentiate 92% of females from the 'Antipodes Island group' versus the 'Auckland Island group' based on head and bill length, culmen depth at the base and wing length. Discriminant analysis indicates that the Antipodes Island population male and female white-chinned petrel study skins related closest to the 'Antipodes Island group' and the Auckland Island, South Indian Ocean, South Atlantic Ocean, and Chile male and female white-chinned petrel study skins related closest to the 'Auckland Island group'. The results suggest that within the New Zealand EEZ there are two taxa of white-chinned petrels based on external morphology: 'aequinoctialis' Linnaeus, the smaller sized white-chinned petrels from the Auckland Islands; and 'steadi' Mathews, the larger sized white-chinned petrels from Antipodes Island and most likely Campbell Island. The results also suggest that, globally, the external morphology of white-chinned petrels can be used to identify two taxa: 'aequinoctialis' Linnaeus, the smaller sized white-chinned petrels which comprise the Auckland Islands, the South Indian Ocean, and the South Atlantic Ocean populations; and 'steadi' Mathews, the larger sized white-chinned petrels which comprise the Antipodes Islands population. Further, most white-chinned petrels caught off Chile are likely to be from the Auckland Island breeding population or South Atlantic Ocean breeding populations

Anthropic Indexical Sampling and Implications for The Doomsday Argument

Anthropic reasoning refers to a class of arguments that incorporate the information entailed by our own existence to make inferences about the world in which we live. One prominent example is the Doomsday Argument, which makes predictions about the future total population of human observers yet to be born based on the ordinal rank of our birth among humans that have been born so far. A central question in anthropic reasoning is from which distribution should we consider ourselves to be randomly sampled. The Self Sampling Assumption (SSA) states that we should reason as if we're a random sample from the set of actual existent observers, while the self indication assumption (SIA) states that we should reason as if we're a random sample from among the set of all possible observers (Bostrom 2002). Effectively, SIA weighs the probability of our actual world by the number of observers relative to SSA. The distinction is important, as SSA supports the Doomsday Argument, while SIA refutes it. We consider a new thought experiment called {\em Geometric Incubator} and show that SSA implies precognition of coin flips in this hypothetical world. We consider this to be very strong evidence in favor of SIA over SSA and against the Doomsday Argument. We use this observation to develop a more axiomatic mathematical theory of anthropic reasoning. We also introduce an empirical version of the Doomsday Argument

Incidental Catch of Marine Mammals by Foreign and Joint Venture Trawl Vessels in the U.S. EEZ of the North Pacific, 1973-88

During 1973-88, 3,661 marine mammals of 17 species were reported as incidental catch by U.S. fishery observers aboard foreign and joint venture trawl vessels in the U.S. Exclusive Economic Zone in the North Pacific Ocean and the Bering Sea. Northern sea lions (Eumetopias jubatus) accounted for 90% of the reported incidental mortality in the Gulf of Alaska and eastern Bering Sea. Nearly half of these sea lions were taken in trawl nets in the Shelikof Strait, Alaska, joint venture fishery during 1982-84. However, high incidental mortality rates (>25 sea lions per 10,000 metric tons of groundfish catch) also occurred in the foreign fisheries near Kodiak Island and in the Aleutian Islands area in earlier years. Estimated annual mortality of incidentally caught northern sea lions in Alaska declined from 1,000 to 2,000 animals per year during the early 1970s and 1982 to fewer than 100 animals in 1988. In the Bering Sea most sea lions incidentally caught were males, while in the Gulf of Alaska females were more frequently caught. Females may also have been dominant in the incidental catch of sea lions in the Aleutian Islands area, but age and sex composition data are limited. Incidental mortality of adult female sea lions by foreign trawl fisheries in these areas could have partially contributed to the reported declines in northern sea lion populations in Alaska during the 1970s, but it cannot alone account for the present decline in population size. (PDF file contains 64 pages.

Biological and Statistical Variation in Age Estimation from Pubic Symphyseal Morphology with Regard to Individual Identification and Demographic Profiling

Population variation in the morphological aging process of the pubic symphysis has generated much debate. The question of whether age parameters derived from an American population will reliably estimate age-at-death for East European skeletal populations is important since the ability to accurately estimate an individual’s age-at-death hinges on what standard is used. Consequently, successful age estimation, individual identification, and demographic profiling rests on the ability to correctly define the skeletal parameters of age-at-death. The purpose of this study is to assess the aging process of American and East European populations and to determine what age parameters should be applied to estimate the ages-at-death for unidentified victims. A reference sample of identified individuals with known ages-at-death from Kosovo, Bosnia, and Croatia (n=861) is used to determine the age structure of victims and serves as the informed prior in the Bayesian analysis. Skeletal data comes from a subset of the Balkan reference sample and a comparative American sample. Balkan male (n=212) and female (n=84) pubic symphyses were scored in both the manners of Todd (1920 and 1924) and Suchey-Brooks (Katz and Suchey, 1986; Suchey et al., 1986). Further, repeat observations were completed by four observers for the entire Balkan sample. American male (n=1,560) and female (n=518) pubic symphyses were scored in the manner of Todd (1920 and 1921). The American data were converted from the Todd ten-phase system to the Suchey-Brooks six-phase system, as recommended by Katz and Suchey (1986) for comparative purposes. First, the affect of inter-observer variation on the reliability of estimating age-at-death parameters from the pubic symphyses is investigated. Pearson’s r correlation coefficients among observers for the Todd system are all significant (p \u3c 0.01) and strongly correlate among females. The correlation coefficients among males are more varied and not as strong as the female sample, ranging from r = 0.309 – 0.738. Correlation coefficients among observers for the Suchey-Brooks method are more consistent and higher than those for the Todd method, ranging from r = 0.866 – 0.939 among females and from r = 0.710 – 0.844 among males. Wilcoxon signed ranks tests demonstrate significant differences among observers for both methods. Second, population variation in the aging processes of American and East European populations is tested using proportional odds probit regression. An analysis of deviance is calculated using an improvement chi-square to test the adequacy of the model. No significant association between the aging process of pubic symphyses and population is found (df = 1, chi-square likelihood ratio = 3.209, p = 0.10). However, when males and females are treated separately, there is a significant association among females and the population (df = 1, chi-square likelihood ratio = 15.071, p = 0.001). Finally, a Bayesian statistical analysis is utilized to establish accurate age parameters. The ages-of-transition for each phase are calculated using an unrestrictive cumulative probit model for the Balkan males and the log-age cumulative probit model for the Balkan females. The probability density functions (PDF) for the posterior distributions of age at each symphyseal phase are calculated. The age estimates are based on the calculated age distribution from the Gompertz-Makeham hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density regions for each Symphyseal phase is calculated and four different regions are provided (95%, 90%, 75%, and 50%)

Data Analysis in Multimedia Quality Assessment: Revisiting the Statistical Tests

Assessment of multimedia quality relies heavily on subjective assessment, and is typically done by human subjects in the form of preferences or continuous ratings. Such data is crucial for analysis of different multimedia processing algorithms as well as validation of objective (computational) methods for the said purpose. To that end, statistical testing provides a theoretical framework towards drawing meaningful inferences, and making well grounded conclusions and recommendations. While parametric tests (such as t test, ANOVA, and error estimates like confidence intervals) are popular and widely used in the community, there appears to be a certain degree of confusion in the application of such tests. Specifically, the assumption of normality and homogeneity of variance is often not well understood. Therefore, the main goal of this paper is to revisit them from a theoretical perspective and in the process provide useful insights into their practical implications. Experimental results on both simulated and real data are presented to support the arguments made. A software implementing the said recommendations is also made publicly available, in order to achieve the goal of reproducible research

Sex-related differences in chromatic sensitivity

Generally women are believed to be more discriminating than men in the use of colour names and this is often taken to imply superior colour vision. However, if both X-chromosome linked colour deficient males (~8%) and females (<1%) as well as heterozygote female carriers (~15%) are excluded from comparisons, then differences between men and women in red-green colour discrimination have been reported as not being significant (e.g., Pickford, 1944; Hood et al., 2006). We re-examined this question by assessing the performance of 150 males and 150 females on the Colour Assessment and Diagnosis (CAD) test (Rodriguez-Carmona, 2005). This is a sensitive test that yields small colour detection thresholds. The test employs direction-specific, moving, chromatic stimuli embedded in a background of random, dynamic, luminance contrast noise. A four-alternative, forced-choice procedure is employed to measure the subject’s thresholds for detection of colour signals in 16 directions in colour space, while ensuring that the subject cannot make use of any residual luminance contrast signals. In addition, we measured the Rayleigh anomaloscope matches in a subgroup of 111 males and 114 females. All the age-matched males (30.8 ± 9.7) and females (26.7 ± 8.8) had normal colour vision as diagnosed by a battery of conventional colour vision tests. Females with known colour deficient relatives were excluded from the study. Comparisons between the male and female groups revealed no significant differences in anomaloscope midpoints (p=0.709), but a significant difference in matching ranges (p=0.040); females on average tended to have a larger mean range (4.11) than males (3.75). Females also had significantly higher CAD thresholds than males along the red-green (p=0.0004), but not along the yellow-blue discrimination axis. The differences between males and females in red-green discrimination may be related to the heterozygosity in X-linked cone photopigment expression common among females