University of St Andrews

About: University of St Andrews is a education organization based out in St Andrews, Fife, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 16260 authors who have published 43364 publications receiving 1636072 citations. The organization is also known as: St Andrews University & University of St. Andrews.

Deep‐diving foraging behaviour of sperm whales (Physeter macrocephalus)

Abstract: 1. Digital tags were used to describe diving and vocal behaviour of sperm whales during 198 complete and partial foraging dives made by 37 individual sperm whales in the Atlantic Ocean, the Gulf of Mexico and the Ligurian Sea. 2. The maximum depth of dive averaged by individual differed across the three regions and was 985 m (SD = 124.3), 644 m (123.4) and 827 m (60.3), respectively. An average dive cycle consisted of a 45 min (6.3) dive with a 9 min (3.0) surface interval, with no significant differences among regions. On average, whales spent greater than 72% of their time in foraging dive cycles. 3. Whales produced regular clicks for 81% (4.1) of a dive and 64% (14.6) of the descent phase. The occurrence of buzz vocalizations (also called 'creaks') as an indicator of the foraging phase of a dive showed no difference in mean prey capture attempts per dive between regions [18 buzzes/dive (7.6)]. Sperm whales descended a mean of 392 m (144) from the start of regular clicking to the first buzz, which supports the hypothesis that regular clicks function as a long-range biosonar. 4. There were no significant differences in the duration of the foraging phase [28 min (6.0)] or percentage of the dive duration in the foraging phase [62% (7.3)] between the three regions, with an overall average proportion of time spent actively encountering prey during dive cycles of 0.53 (0.05). Whales maintained their time in the foraging phase by decreasing transit time for deeper foraging dives. 5. Similarity in foraging behaviour in the three regions and high diving efficiencies suggest that the success of sperm whales as mesopelagic predators is due in part to long-range echolocation of deep prey patches, efficient locomotion and a large aerobic capacity during diving.

Why do populations cycle? a synthesis of statistical and mechanistic modeling approaches

Abstract: Population cycles have long fascinated ecologists. Even in the most-studied populations, however, scientists continue to dispute the relative importance of various potential causes of the cycles. Over the past three decades, theoretical ecologists have cataloged a large number of mechanisms that are capable of generating cycles in population models. At the same time, statisticians have developed new techniques both for characterizing time series and for fitting population models to time-series data. Both disciplines are now sufficiently advanced that great gains in understanding can be made by synthesizing these complementary, and heretofore mostly independent, quantitative approaches. In this paper we demonstrate how to apply this synthesis to the problem of population cycles, using both long-term population time series and the often-rich observational and experimental data on the ecology of the species in question. We quantify hypotheses by writing mathematical models that embody the interactions and forces that might cause cycles. Some hypotheses can be rejected out of hand, as being unable to generate even qualitatively appropriate dynamics. We finish quantifying the remaining hypotheses by estimating parameters, both from independent experiments and from fitting the models to the time-series data using modern statistical techniques. Finally, we compare simulated time series generated by the models to the observed time series, using a variety of statistical descriptors, which we refer to collectively as “probes.” The model most similar to the data, as measured by these probes, is considered to be the most likely candidate to represent the mechanism underlying the population cycles. We illustrate this approach by analyzing one of Nicholson’s blowfly populations, in which we know the “true” governing mechanism. Our analysis, which uses only a subset of the information available about the population, uncovers the correct answer, suggesting that this synthetic approach might be successfully applied to field populations as well.

Effects of eutrophication on reef-building corals. III: Reproduction of the reef-building coral Porites porites

Abstract: The sexual reproduction of Porites porites (Pallas), a shallow water hermatypic coral, was studied over a one-year period (June, 1982 to June, 1983) on three fringing reef complexes lying along an eutrophication gradient on the west coast of Barbados, West Indies. The data suggest that P. porites is a gonochoric species with a brooding mode of reproduction, but a low incidence (2.7%) of hermaphroditism was detected in a population sampled from a reef subjected to urban and industrial pollution. Gonadal development occurs within the mesenteries between the retractor muscles and the mesenterial filaments. Gametogenesis occurs during nine to ten months of the year, with the peak reproductive activity occurring predominantly in the fall and winter (November to January). Gametogenesis was therefore loosely synchronized between colonies; however, gonads in all stages of development were present within colonies throughout the reproductive season. The reproductive season of two P. porites populations sampled from two polluted reefs began one to two months earlier than that of a P. porites population sampled from a less polluted reef. The simultaneous presence of ova and larvae within a colony between November and April suggests that larvae may be released repeatedly during an extended breeding season. No correlation was found between the average number of gonads and polyp size. However, the gonad index (average number of gonads based on the sum of male and female gonads) showed an inverse relationship with a number of environmental variables. It is suggested that zooxanthellae in the maturing ova may play an important role in the reproductive success of P. porites. The reduction of zooxanthellae photosynthesis through reduced light levels may significantly lower the energy available from photosynthates to the maturing ova and/or embryos, thus depressing larval development and maturation. Coral colonies sampled from two polluted reefs contained lower numbers of larvae than colonies sampled from a less polluted reef. The 2: 1 sex ratio observed in a P. porites population sampled from a polluted reef may result from rapid asexual reproduction (fragmentation), indicating that the mode of reproduction may be influenced by environmental conditions.

Symmetry, sexual dimorphism in facial proportions and male facial attractiveness.

Abstract: Facial symmetry has been proposed as a marker of developmental stability that may be important in human mate choice. Several studies have demonstrated positive relationships between facial symmetry and attractiveness. It was recently proposed that symmetry is not a primary cue to facial attractiveness, as symmetrical faces remain attractive even when presented as half faces (with no cues to symmetry). Facial sexual dimorphisms ('masculinity') have been suggested as a possible cue that may covary with symmetry in men following data on trait size/symmetry relationships in other species. Here, we use real and computer graphic male faces in order to demonstrate that (i) symmetric faces are more attractive, but not reliably more masculine than less symmetric faces and (ii) that symmetric faces possess characteristics that are attractive independent of symmetry, but that these characteristics remain at present undefined.