Animal movement in dynamic landscapes : interaction between behavioural strategies and resource distributions

Most ecological and evolutionary processes are thought to critically depend on dispersal and individual movement but there is little empirical information on the movement strategies used by animals to find resources. In particular, it is unclear whether behavioural variation exists at all scales, or whether behavioural decisions are primarily made at small spatial scales and thus broad-scale patterns of movement simply reflect underlying resource distributions. We evaluated animal movement responses to variable resource distributions using the grey teal (Anas gracilis) in agricultural and desert landscapes in Australia as a model system. Birds in the two landscapes differed in the fractal dimension of their movement paths, with teal in the desert landscape moving less tortuously overall than their counterparts in the agricultural landscape. However, the most striking result was the high levels of individual variability in movement strategies, with different animals exhibiting different responses to the same resources. Teal in the agricultural basin moved with both high and low tortuosity, while teal in the desert basin primarily moved using low levels of tortuosity. These results call into question the idea that broad-scale movement patterns simply reflect underlying resource distributions, and suggest that movement responses in some animals may be behaviourally complex regardless of the spatial scale over which movement occurs.

Carbon Nanotube – Reduced Graphene Oxide Composites for Thermal Energy Harvesting Applications

By controlling the SWNT-rGO electrode composition and thickness to attain the appropriate porosity and tortuosity, the electroactive surface area is maximized while rapid diffusion of the electrolyte through the electrode is maintained. This leads to an increase in exchange current density between the electrode and electrolyte which results in enhanced thermocell performance.

Cocoon of the silkworm Antheraea pernyi as an example of a thermally insulating biological interface.

Biological materials are hierarchically organized complex composites, which embrace multiple practical functionalities. As an example, the wild silkworm cocoon provides multiple protective functions against environmental and physical hazards, promoting the survival chance of moth pupae that resides inside. In the present investigation, the microstructure and thermal property of the Chinese tussah silkworm (Antheraea pernyi) cocoon in both warm and cold environments under windy conditions have been studied by experimental and numerical methods. A new computational fluid dynamics model has been developed according to the original fibrous structure of the Antheraea pernyi cocoon to simulate the unique heat transfer process through the cocoon wall. The structure of the Antheraea pernyi cocoon wall can promote the disorderness of the interior air, which increases the wind resistance by stopping most of the air flowing into the cocoon. The Antheraea pernyi cocoon is wind-proof due to the mineral crystals deposited on the outer layer surface and its hierarchical structure with low porosity and high tortuosity. The research findings have important implications to enhancing the thermal function of biomimetic protective textiles and clothing.

Utilisation of intensive foraging zones by female Australian fur seals

Within a heterogeneous environment, animals must efficiently locate and utilise foraging patches. One way animals can achieve this is by increasing residency times in areas where foraging success is highest (area-restricted search). For air-breathing diving predators, increased patch residency times can be achieved by altering both surface movements and diving patterns. The current study aimed to spatially identify the areas where female Australian fur seals allocated the most foraging effort, while simultaneously determining the behavioural changes that occur when they increase their foraging intensity. To achieve this, foraging behaviour was successfully recorded with a FastLoc GPS logger and dive behaviour recorder from 29 individual females provisioning pups. Females travelled an average of 118 ± 50 km from their colony during foraging trips that lasted 7.3 ± 3.4 days. Comparison of two methods for calculating foraging intensity (first-passage time and first-passage time modified to include diving behaviour) determined that, due to extended surface intervals where individuals did not travel, inclusion of diving behaviour into foraging analyses was important for this species. Foraging intensity 'hot spots' were found to exist in a mosaic of patches within the Bass Basin, primarily to the south-west of the colony. However, the composition of benthic habitat being targeted remains unclear. When increasing their foraging intensity, individuals tended to perform dives around 148 s or greater, with descent/ascent rates of approximately 1.9 m•s-1 or greater and reduced postdive durations. This suggests individuals were maximising their time within the benthic foraging zone. Furthermore, individuals increased tortuosity and decreased travel speeds while at the surface to maximise their time within a foraging location. These results suggest Australian fur seals will modify both surface movements and diving behaviour to maximise their time within a foraging patch.

Directional moisture transfer through a wild silkworm cocoon wall

A silkworm cocoon is a porous biological structure with multiple protective functions. In the current work, the authors have used both experimental and numerical methods to reveal the unique moisture transfer characteristics through a wild Antheraea pernyi silkworm cocoon wall, in comparison with the long-domesticated Bombyx mori silkworm cocoon walls. The water vapor transmission and water vapor permeability (WVP) properties show that the A. pernyi cocoons exhibit directional moisture transfer behavior, with easier moisture transfer from inside out than outside in [e.g., the average WVP is 0.057 g/(h m bar) from inside out and is 0.034 g/(h m bar) from outside in]. Numerical analysis shows that the cubic mineral crystals in the outer section of the A. pernyi cocoon wall create a rough surface that facilitates air turbulence and promotes disturbance amplitude of the flow field, leading to lengthened water vapor transfer path and increased tortuosity of the moist air. It also indicates the vortex of water vapor can be generated in the outer section of cocoon wall, which increases the diffusion distance of water vapor and enhances the turbulence kinetic energy and turbulence eddy dissipation, signifying higher moisture resistance in the outer section. The difference in moisture resistance of the multiple A. pernyi cocoon layers is largely responsible for the unique directional moisture transfer behavior of this wild silkworm cocoon. These findings may inspire a biomimicry approach to develop novel lightweight moisture management materials and structures.