A test of scent-trailing as a contributing factor in the climbing behaviour of the redback salamander (Plethodon cinereus)

Terrestrial salamanders of the family Plethodontidae are common predators of invertebrates in deciduous forest communities of eastern North America. While normally residing and foraging in forest-floor microhabitats, many species facultatively climb vegetation. Different hypotheses have been proffered to explain this behaviour including optimal-foraging strategies and predator avoidance. Using laboratory-based trials, we tested the hypothesis that the terrestrial salamander Plethodon cinereus climbs in response to scent trails left by insect prey. We found that salamanders climbed significantly higher and spent significantly more time climbing on wooden dowel rods that had been treated with prey residue than they did on control rods. Scent trailing possibly interacts with other factors such as optimal-foraging opportunities and predation risk in influencing climbing behaviour in these salamanders.

Improvement of glued-in-rod joint system using compressed wooden dowel

The purpose of this study was to develop eco-friendly and high-performance glued-in-rod (GIR) joints using compressed wood (CW), which has higher tensile strength than normal hardwood, instead of conventional wooden dowels. To explore the bonding performance of the dowel and base material, punching shear tests were performed and relationships were established between the density of CW dowel and punching characteristics. Pull-out tests of GIR joints were performed and results were compared with those derived from a mechanical model to evaluate the influence of insertion length of dowel and to define its optimized length. The results indicate that CW dowel has almost the same bonding performance in the density range 330–1000 kg m-3. Hence, CW as a dowel material in GIR joints has a high application potential. Pull-out tests of GIR joints showed that the insertion length of dowel in GIR joints with the CW-67 dowel is the best if the length is 10 times larger than its diameter. In addition to its satisfactory bonding performance, CW dowels have excellent tensile characteristics.

Evaluation on structural performance of compressed wood as shear dowel

This study addresses the application of compressed wood (CW) made of Japanese cedar, as a substitute for high-density hardwood, to shear dowel. A double wood-to-wood shear test was performed to evaluate the mechanical shear properties of CW perpendicular to the grain, and the results were compared with those of several types of dowel material. CW with its annual ring radial to loading direction (0°) had a unique double shear performance characteristic, and showed good properties as a dowel material by virtue of its strength and rich ductility. In contrast, CW with its annual ring tangential to loading direction (90°) and maple exhibited brittle failure. While thickness of the base member was varied, the ductility of the joint became stable for diameter over 36 mm and 24 mm thickness for the main and side members, respectively. When the density of the base member increased, its stiffness, yield load, and maximum load exhibited proportional improvement with different inclinations; however, in the case of a maple dowel, the increases were small. When the density of the base member was increased, the ultimate load had positive linear tendency, whereas plastic modulus decreased. Consequently, almost constant energy absorption was observed in spite of the increased density. The optimum load-carrying capacity and ductility of a compressed wooden dowel joint could be designed by introducing an appropriate base member.