Behavioral response of termites to tunnel surface irregularity.

Subterranean termites construct underground tunnels, tens to hundreds of meters in length, in order to search for and transport resources. Diverse soil conditions surrounding the tunnels, such as soil pores and differing moisture concentrations, may cause different sized- and shaped-irregularities in the tunnels. To understand how individual termites respond to the irregularities, the present study monitored the movement of termites, Coptotermes formosanus Shiraki, in artificially excavated tunnels with rectangular irregularities of varying sizes in two-dimensional sand substrates. Termites tunneled at some of the irregularities and not at the others. The tunneling or non-tunneling behavior resulted from four different responses. The non-tunneling response may result from a behavioral adaptation that allows termites to avoid wasting energy that may be used in foraging.

Exploring landscape structure effect on termite territory size using a model approach.

The foraging territory of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was simulated by using a lattice model in order to study how landscape structure affects the foraging territory. Three kinds of landscape were generated on lattice space: ideal, random and fractal landscape. Each lattice cell had a value ranging from 0.0 to 1.0, interpreted as transition probability, P(trans), which represents spatially distributed property of the landscapes. The heterogeneity of the fractal landscape was characterized by a parameter, H, controlling aggregation of lattice cells with higher value of P(trans). Higher H values corresponded to higher aggregation levels. The model made use of minimized local rules based on empirical data that determines the development of the foraging territory. Additionally, seasonal cycle (summer and winter season), and obstacles which hinder the growth of the territory were incorporated in the model as environmental variables. Territory size was largest in the ideal landscape while it was larger in the random landscape than in the fractal landscape. As obstacle density increased, the territory size decreased. In the fractal landscape, the territory size increased, decreased, and increased again as H increased.

Optimal length distribution of termite tunnel branches for efficient food search and resource transportation.

Subterranean termites excavate branching tunnels for searching and transporting food in soil. Experimentally, the length distribution of the branch tunnels, P(L), was characterized by the exponentially decaying function, P(L) approximately exp(-alphaL) with a branch length exponent of alpha=0.15. To evaluate the significance of this alpha value, we used a lattice model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki in featureless soil and computed the ratio of energy gain for obtained food to loss for transporting food for a given time, gamma for various simulated tunnel patterns with the different values of alpha. In simulation, the gamma was maximized at 0.15

Food encounter rate of simulated termite tunnels in heterogeneous landscapes.

The aim of this study was to explore how a heterogeneous landscape affects food encounter rate in the Formosan subterranean termite, Coptotermes formosanus Shiraki. To do this, a lattice model was formulated to simulate the tunneling structure of the termite. The model made use of minimized local rules derived from empirical data. In addition, a landscape structure was generated on a lattice space by using a neutral landscape model. Each lattice cell has a value h, representing spatially distributed property of the landscape (e.g., temperature or moisture). The heterogeneity of the landscape was characterized by a parameter, H controlling aggregation of lattice cells with higher values of h. Higher H values correspond to higher aggregation levels. The effect of the landscape heterogeneity on the encounter rate was clear in the presence of higher food density than in lower density. The effect was also enhanced by the increase of the number of primary tunnels.

Food encounter rates of simulated termite tunnels with variable food size/distribution pattern and tunnel branch length.

Subterranean termites excavate tunnels in a search pattern to encounter food in soil. To investigate the effect of food size, food distribution and the branch length of tunnels on food encounter rate we used a lattice gas model to simulate tunnels of the Formosan subterranean termite, Coptotermes formosanus Shiraki. The model made use of minimized local rules derived from empirical data to simulate termite tunnel patterns in featureless soil. Food distributions with three types (uniform, random, and clumped) were defined by using an I-index proposed by Zimmer and Johnson (1985). The food encounter rate was higher in a clumped than in non-clumped (uniform and random) distribution of food particles. When food particle size was varied in random distributions of food particles a maximum encounter rate was found, with particles of larger or smaller size being encountered less frequently. We also discussed the relationship between the branch tunnel length and the tunnel search pattern in minimizing the redundancy of overlapping branches.

Three dimensional path integration in the house mouse (Mus domestica).

Previous studies have explored two-dimensional path integration in rodents by recording responses to passive rotation on a horizontal plane. This study adds the element of passive rotation in a vertical plane, necessitating the mouse to integrate positional information from three dimensions. Mice were trained to climb a wire mesh joining two horizontal planes. The whole arena was rotated 90 degrees while the mouse was vertically oriented as it moved between planes. Rotation was conducted both clockwise and counter-clockwise, controls being provided by rotation of the arena while the mouse was in its nest-box. All 16 mice tested altered their direction of travel subsequent to rotation in the vertical plane, compensating with a change in their path on the following horizontal plane.