49 research outputs found
California swordfish fishery: maximizing the catch rate of a target species simultaneously minimizes bycatch rates
No full textNo abstract available
Density dependence and marine bird populations: are wind farm assessments precautionary?
No full textAlthough density-dependent regulation of population growth is thought to be relatively widespread in nature, density-independent models are often used to project the population response to drivers of change. Such models are often considered to provide a maximum estimate of mortality and therefore offer a precautionary approach to impact assessment. However, this perception assumes that density dependence operates as compensatory (negative density dependence), and overlooks that other forms of density dependence, such as depensation (positive density dependence), would generate a contrasting population response.
Currently, there is debate about including density-dependent mechanisms in models that assess the impact of offshore wind farms on marine bird populations. Density dependence is considered poorly understood for this group of species. Consequently, it is either excluded from assessments, or incorporated in a compensatory form that has little empirical validation.
We reviewed the evidence for compensatory and depensatory regulation of 31 marine bird species, and conducted a meta-analysis to examine the functional shape of density-dependent population growth. The evidence was also evaluated in relation to established species-specific indices of wind farm vulnerability in order to assess whether compensatory mechanisms are likely to offset losses associated with collision or displacement.
Compensatory regulation was reported across all of the demographic processes and focal groups considered, and was attributed to a variety of causal mechanisms. The strength of compensatory population growth appeared consistent between colonies; however, the regulation of productivity was highly context-dependent with a similar number of studies reporting compensatory, depensatory and insignificant effects. Depensation was consistently attributed to increased rates of predation at lower population densities.
Synthesis and applications. We conclude that among marine bird species with high vulnerability to wind farms, compensatory regulation is unlikely to offset large and sustained losses from the breeding population. In addition, depensation has the potential to accelerate population declines and generate local or regional extinctions, especially in smaller colonial species. Consequently, density-independent models will not offer a consistently precautionary approach for assessing the potential impact of wind farms on marine bird populations. Instead, assessments should examine the potential population response using a range of density-dependent structures
Factors Influencing Physical Risk Taking in Rock Climbing
No full textThis study was designed to investigate factors influencing physical risk taking in the sport of rock climbing. Specifically, the relationships between physical risk taking, sensation seeking, spheres of control, and desirability of control were examined. One hundred five rock climbers from the United States completed a series of surveys measuring each of the above-mentioned psychological variables. As predicted, physical risk taking demonstrated significant positive relationships to both total sensation seeking and thrill/adventure seeking (TAS). The expected relationships between physical risk taking, personal control and desirability of control were not supported. As hypothesized, no substantive patterns were revealed between physical risk taking and interpersonal control or sociopolitical control. Finally, comparisons between high and low physical risk taking rock climbers revealed significant group differences for total sensation seeking, TAS, and disinhibition. The identification of predictors of physical risk taking is a key step toward identifying individuals likely to engage in high physical risk behavior, and under what circumstances they are likely to do so
Linking extreme interannual changes in prey availability to foraging behaviour and breeding investment in a marine predator, the macaroni penguin
No full textUnderstanding the mechanisms that link prey availability to predator behaviour and population change is central to projecting how a species may respond to future environmental pressures. We documented the behavioural responses and breeding investment of macaroni penguins Eudyptes chrysolophus across five breeding seasons where local prey density changed by five-fold; from very low to highly abundant. When prey availability was low, foraging trips were significantly longer and extended overnight. Birds also foraged farther from the colony, potentially in order to reach more distant foraging grounds and allow for increased search times. These extended foraging trips were also linked to a marked decrease in fledgling weights, most likely associated with reduced rates of provisioning. Furthermore, by comparing our results with previous work on this population, it appears that lowered first-year survival rates associated, at least partially, with fledging masses were also evident for this cohort. This study integrates a unique set of prey density, predator behaviour and predator breeding investment data to highlight a possible behavioural mechanism linking perturbations in prey availability to population demography
Lightweight Procedural Animation with Believable Physical Interactions
No full textI describe a procedural animation system that uses techniques from behavior-based robot control, combined with a minimalist physical simulation, to produce believable character motions in a dynamic world. Although less realistic than motion capture or full biomechanical simulation, the system produces compelling, responsive character behavior. It is also fast, supports believable physical interactions between characters such as hugging, and makes it easy to author new behaviors
Postmortem: MKULTRA, An Experimental AI-Based Game
No full textGames are inherently situated within the cultures of their players. Players bring a wide range of knowledge and expectations to a game, and the more the game suggests connections to that culture, the stronger those expectations are and/or the more problematic they can be. MKULTRA is an experimental, AI-heavy game that ran afoul of those issues. It’s interesting to hear a talk about or to see demonstrated by the author, but frustrating for players who do not already understand its internals in some detail. In this paper, I will give a postmortem of the game, in the rough style of industry postmortems from venues such as Gamasutra or GDC. I will discuss the goals and design of the game, what went right, what went wrong, and what I should have done instead. In my discussions of the game’s problems, I’ll focus on the ways in which it frustrated the players’ cultural expectations, and what we can learn from them for the design of future games
Temporal change in the contribution of immigration to population growth in a wild seabird experiencing rapid population decline
No full textThe source–sink paradigm predicts that populations in poorer-quality habitats (‘sinks’) persist due to continued immigration from more-productive areas (‘sources’). However, this categorisation of populations assumes that habitat quality is fixed through time. Globally, we are in an era of wide-spread habitat degradation, and consequently there is a pressing need to examine dispersal dynamics in relation to local population change. We used an integrated population model to quantify immigration dynamics in a long-lived colonial seabird, the black-legged kittiwake Rissa tridactyla, that is classified as globally ‘Vulnerable’. We then used a transient life table response experiment to evaluate the contribution of temporal variation in vital rates, immigration rates and population structure to realised population growth. Finally, we used a simulation analysis to examine the importance of immigration to population dynamics. We show that the contribution of immigration changed as the population declined. This study demonstrates that immigration is unlikely to maintain vulnerable sink populations indefinitely, emphasising the need for temporal analyses of dispersal to identify shifts that may have dramatic consequences for population viability
Hierarchical Parallel Markov Models for Interactive Social Agents
No full textFinite state techniques are popular in entertainment software production, but they complicate the modeling of certain aspects of social engagement. In this paper we examine the problem of building probabilistic finite-state interaction models that allow both hierarchical composition of behaviors, and their parallel engagement. Finally, we propose an extension that resolves the difficulties for a class of common cases. Interaction Modeling Intelligent game agents must be able to interact with players, to present themselves as actual inhabitants of the virtual world. Popular approaches to interaction, such as static conversation trees and exchanges of pre-recorded blurbs, are widely recognized as insufficient, but a more generative natural language interaction will require a different approach to the underlying representation. Interaction modeling in games is constrained by the demands of authoring, believability, and performance. The underlying mechanism must allow for easy behavior authoring, because developers require precise control over what the system will do at runtime, in order to provide enjoyable and engaging user experience, with specific aesthetic effects (Hunicke, LeBlanc and Zubek 2004). Additionally, developers want the behavior of the system to be believable, resembling the relevant aspects of human activity; ideally, believable behavior should be produced out of patterns matched against the game state, rather than being completely hand-scripted by a writer. Finally, the mechanisms must be computationally efficient, producing desirable behavior in only a fraction of total compute cycles. For these reasons, simple techniques such as finite state machines (FSMs) remain very popular. Hand-crafted FSMs are routinely used to implement character behavior, since they are simple to author, intuitive to debug, and efficient to compute. In character interaction and conversation, simple dialog trees are very popular. In domains where the inputs are noisy or ambiguous— such as in tracking human activity or language processing—stochastic generalizations are often use
The contribution of music in drivers' time-to-arrival estimations
No full textDriver accuracy in decision-making and estimation is essential to the safety of everyone on the road. Numerous studies have highlighted the failings of drivers’ abilities in critical areas and demonstrated drivers’ tendencies to severely underestimate speed, susceptibility to overestimate time-to-arrival, and reliance on perceptions of time which are influenced by stimuli such as music or conversation (Schutz et al., 2015; Horswill et al., 2005; Brodsky & Slor, 2013). The purpose of the present study was to measure how music affected judgments of speed. To test this, observers were shown a series of videos in which their visual processing was interrupted and were asked to estimate when an approaching test car would have arrived. The results of the study indicated that tempo did not have an effect on time-to-arrival estimations, but that speed did affect time-to-arrival estimations. These results suggest that drivers’ musical choices may not be as important as previously thought for their abilities to make accurate estimations of the amount of time they have before an oncoming vehicle will reach them.M.A.Includes bibliographical reference
