Optimization of resource allocation can explain the temporal dynamics and honesty of sexual signals

In species in which males are free to dynamically alter their allocation to sexual signaling over the breeding season, the optimal investment in signaling should depend on both a male’s state and the level of competition he faces at any given time. We developed a dynamic optimization model within a game‐theoretical framework to explore the resulting signaling dynamics at both individual and population levels and tested two key model predictions with empirical data on three‐spined stickleback (Gasterosteus aculeatus) males subjected to dietary manipulation (carotenoid availability): (1) fish in better nutritional condition should be able to maintain their signal for longer over the breeding season, resulting in an increasingly positive correlation between nutritional status and signal (i.e., increasing signal honesty), and (2) female preference for more ornamented males should thus increase over the breeding season. Both predictions were supported by the experimental data. Our model shows how such patterns can emerge from the optimization of resource allocation to signaling in a competitive situation. The key determinants of the honesty and dynamics of sexual signaling are the condition dependency of male survival, the initial frequency distribution of nutritional condition in the male population, and the cost of signaling

Silicon micromachined accelerometer/seismometer and method of making the same

A silicon-based microaccelerometer for seismic application is provided using a low-resonant frequency (10 Hz), large proof mass (1 gram), and high Q suspension to achieve high sensitivity of less than 1 ng with a bandwidth a 0.05 to 50 Hz. The proof mass is cut away from a planar substrate in the form of a disk using abrasive cutting, which disk closely fits but does not touch a surrounding angular frame. The spring of the microaccelerometer between the angular frame and the proof mass is provided from two continuous, 3 microns thick membranes. The fixed capacitive electrodes are provided on separate, subsequently bonded substrates, and movable capacitive plates are provided on the membranes. By fabricating capacitive plates on the separate substrates, the gap between the fixed and movable capacitive plates in the differential capacitive sensor is closely controlled. The use of continuous membranes for the spring produces a shock resistant, robust sensor

Using robots to understand animal cognition

In recent years, robotic animals and humans have been used to answer a variety of questions related to behavior. In the case of animal behavior, these efforts have largely been in the field of behavioral ecology. They have proved to be a useful tool for this enterprise as they allow the presentation of naturalistic social stimuli whilst providing the experimenter with full control of the stimulus. In interactive experiments, the behavior of robots can be controlled in a manner that is impossible with real animals, making them ideal instruments for the study of social stimuli in animals. This paper provides an overview of the current state of the field and considers the impact that the use of robots could have on fundamental questions related to comparative psychology: namely, perception, spatial cognition, social cognition, and early cognitive development. We make the case that the use of robots to investigate these key areas could have an important impact on the field of animal cognition

Individual differences in visual and olfactory cue preference and use by cats (Felis catus)

Highlights • Eight cats were trained in a T-maze using a two-alternative forced choice procedure. • Cats could use either an olfactory or visual cue to locate a food reward. • Cues were then put in conflict to determine which was preferred for the task. • Most cats used the visual cue to learn the location of the food. • Preferences were stable, repeatable and rapidly learned. -------------------------------------------------------------------------------- Abstract Animals are constantly presented with stimuli through different sensory challenges, which may sometimes contain contradictory information and so they must decide which is more salient in a given situation. Both vision and olfaction are extensively utilised by the domestic cat (Felis catus) in a variety of biological contexts, but which modality tends to take priority when the two channels contain information of similar potential value is unknown, as is the tendency for different individuals to use different cues in relation to the same situation. Such individual difference may have important clinical implications as it may help to explain why animals living within the same house may respond differently to the same environment. For example a change in the olfactory features of the environment may be stressful to an individual who has a bias towards using this sensory modality, but have no significant impact on individuals who rely more on visual cues for orientation. Eight cats were trained in a T-maze using a two-alternative forced choice procedure. The positive and negative stimuli presented both visual and olfactory information. Thus, there were two cues that the cats could use in order to make the discrimination. After reaching criterion for their training stimuli the six successful cats were presented with a feature mismatch test in which the positive visual stimuli were combined with the negative olfactory stimuli and vice versa. This investigated which cues were of greater salience to them. Four out of six cats showed a significant preference (P = 0.022- 0.006) for the visual cue, but one individual showed a consistent preference for using the olfactory cue (P = 0.019). To investigate whether the cats using visual cues had learned anything about the olfactory stimulus, four were given an additional test in which they were presented with the olfactory stimulus alone. Three out of four cats successfully made this discrimination, (P = 0.006-0.003, unsuccessful cat P = 0.076). This demonstrated that the cats had the potential to use olfactory cues in the absence of visual ones. These results highlight the importance of considering sensory preferences as an individual trait, which may vary substantially from population level effects

Dietary carotenoid availability, sexual signalling and functional fertility in sticklebacks

In species where males express carotenoid-based sexual signals, more intensely coloured males may be signalling their enhanced ability to combat oxidative stress. This may include mitigating deleterious oxidative damage to their sperm, and so be directly related to their functional fertility. Using a split-clutch in vitro fertilization technique and dietary carotenoid manipulation, we demonstrate that in non-competitive fertilization assays, male three-spined sticklebacks (Gasterosteus aculeatus) that are fed higher (but biologically relevant) levels of carotenoids had a significantly increased fertilization success, irrespective of maternal carotenoid intake. Furthermore, within diet groups, a male's fertilization success was positively related to the expression of his carotenoid-based nuptial coloration, with more intensely coloured males having higher functional fertility. These data provide, to our knowledge, the first demonstration that dietary access to carotenoids influences fertilization success, and suggest that females could use a male's nuptial coloration as an indicator of his functional fertility

Offspring social network structure predicts fitness in families.

addresses: Centre for Ecology and Conservation, Biosciences, College of Life and Environmental Sciences, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, UK. [email protected]: PMCID: PMC3497231types: Journal Article; Research Support, Non-U.S. Gov'tSocial structures such as families emerge as outcomes of behavioural interactions among individuals, and can evolve over time if families with particular types of social structures tend to leave more individuals in subsequent generations. The social behaviour of interacting individuals is typically analysed as a series of multiple dyadic (pair-wise) interactions, rather than a network of interactions among multiple individuals. However, in species where parents feed dependant young, interactions within families nearly always involve more than two individuals simultaneously. Such social networks of interactions at least partly reflect conflicts of interest over the provision of costly parental investment. Consequently, variation in family network structure reflects variation in how conflicts of interest are resolved among family members. Despite its importance in understanding the evolution of emergent properties of social organization such as family life and cooperation, nothing is currently known about how selection acts on the structure of social networks. Here, we show that the social network structure of broods of begging nestling great tits Parus major predicts fitness in families. Although selection at the level of the individual favours large nestlings, selection at the level of the kin-group primarily favours families that resolve conflicts most effectively

The impact of water pH on association preferences in fish

Acidification of lakes and rivers, as a consequence of anthropogenic interference, can cause fundamental changes to biological and ecological processes. One of the main consequences of a reduction in water pH for aquatic organisms is the disruption of their chemosensory abilities, as the detection of chemical cues underpins a wide range of decision-making processes; for example, a reduction to low pH has been shown to interfere with predator avoidance and the detection of foraging cues. Moreover, aquatic organisms are known to make widespread use of chemical information to inform their social behaviour, although we have a comparably poor understanding of how this is impacted by water acidification, especially their shoaling behaviour. Using a standard behavioural assay, we therefore investigated the impact of low water pH on the social interactions mediated by diet-derived chemical cues in three-spined sticklebacks (Gasterosteus aculeatus), by quantifying social behaviour in water that varied either experimentally or naturally in pH. In both cases we predicted that association patterns would be disrupted by low pH conditions, as reduced pH has shown to interfere with the perception of chemical cues in other non-social contexts. Consistent with this prediction, our results demonstrate that an acute, short-term reduction in water pH caused a breakdown in the diet-mediated social interaction patterns seen in more alkaline water, although, interestingly, the pattern of associations for fish tested in naturally acidic water was both more complex and in a direction that was precisely contrary to our predictions. Overall the findings provide insights into the potential effects of an acute reduction in water pH on fish communication and social interaction patterns, which may have implication for various individual, group, population and community-level processes

High-resolution isotopic evidence of specialised cattle herding in the European Neolithic.

Peer reviewe

Planetary Interiors

This report identifies two main themes to guide planetary science in the next two decades: understanding planetary origins, and understanding the constitution and fundamental processes of the planets themselves. Within the latter theme, four specific goals related to interior measurements addressing the theme. These are: (1) Understanding the internal structure and dynamics of at least one solid body, other than the Earth or Moon, that is actively convecting, (2) Determine the characteristics of the magnetic fields of Mercury and the outer planets to provide insight into the generation of planetary magnetic fields, (3) Specify the nature and sources of stress that are responsible for the global tectonics of Mars, Venus, and several icy satellites of the outer planets, and (4) Advance significantly our understanding of crust-mantle structure for all the solid planets. These goals can be addressed almost exclusively by measurements made on the surfaces of planetary bodies

Thorium-234 as a tracer of spatial, temporal and vertical variability in particle flux in the North Pacific

Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 56 (2009):1143-1167, doi:10.1016/j.dsr.2009.04.001.An extensive 234Th data set was collected at two sites in the North Pacific: ALOHA, an oligotrophic site near Hawaii, and K2, a mesotrophic HNLC site in the NW Pacific as part of the VERTIGO (VERtical Transport in the Global Ocean) study. Total 234Th:238U activity ratios near 1.0 indicated low particle fluxes at ALOHA, while 234Th:238U ~0.6 in the euphotic zone at K2 indicated higher particle export. However, spatial variability was large at both sites- even greater than seasonal variability as reported in prior studies. This variability in space and time confounds the use of single profiles of 234Th for sediment trap calibration purposes. At K2, there was a decrease in export flux and increase in 234Th activities over time associated with the declining phase of a summer diatom bloom, which required the use of non-steady state models for flux predictions. This variability in space and time confounds the use of single profiles of 234Th for sediment trap calibration purposes. High vertical resolution profiles show narrow layers (20-30 m) of excess 234Th below the deep chlorophyll maximum at K2 associated with particle remineralization resulting in a decrease in flux at depth that may be missed with standard sampling for 234Th and/or with sediment traps. Also, the application of 234Th as POC flux tracer relies on accurate sampling of particulate POC/234Th ratios and here the ratio is similar on sinking particles and mid-sized particles collected by in-situ filtration (>10-50 μm at ALOHA and >5–350 μm at K2). To further address variability in particle fluxes at K2, a simple model of the drawdown of 234Th and nutrients is used to demonstrate that while coupled during export, their ratios in the water column will vary with time and depth after export. Overall these 234Th data provide a detailed view into particle flux and remineralization in the North Pacific over time and space scales that are varying over days to weeks, and 10’s to 100’s km at a resolution that is difficult to obtain with other methods.Funding for VERTIGO in the US was provided primarily by research grants from the US National Science Foundation Programs in Chemical and Biological Oceanography with additional support by the US Department of Energy (DAS). For TWT, support came from the Australian Cooperative Research Centres program