6.2 Intra-species communication & Foraging in social insects  (Page 5/9)

Figure 1 Redrawn fromTanner&Visscher (2008)

As far as direction is concerned, Von Frisch was able to prove that, because bee dancers advertising for the same location would change orientation throughout the day, they use the Sun as their ‘North Star,’ so to speak. If the food source is in the direction of the Sun, the dancers move directly upwards along the surface of the hive, shifting away from the vertical orientation depending on its angle and direction from the Sun (Von Frisch 1974). Also, the honeybee’s ability to see polarized light permits them to forage and communicate even when the Sun is obscured and during nighttime (1974). Honeybees can map mentally the paths they travel, meaning they are capable of path integration. This influences the locations they communicate. When a waggle dance indicates a particularly remote distance, the spatial and directional information communicated may be insufficient on difficult terrain. Chittka et al. preformed a set of experiments with trained honeybees in which they proved that foragers are able to memorize and sequence even multiple landmarks along a path to a resource. Foragers can respond to them contextually even if they are not in direct proximity to a food source, allowing them to follow specific memorized trajectories from one landmark to the next (1995). De Marco and Menzel found that because of path integration, when forced to follow a detour, a honeybee scout is actually capable of communicating a theoretical untraveled route with the use of visual references and odometric mapping of the terrain (2005). Therefore, honeybees communicate both distance and direction in their dance (Gardner et al. 2007), that are both actual and hypothetical, taking into account a variety of environmental references (see figure 1).

Seely et al. have also shown in their experiments that waggle dancers communicate even the quality of the food source. They noticed that, while the waggle phase remained constant, the length of the return phase was directly related to the quality of the food source—the longer the return, the higher sucrose content of the resource (2000). This unique and highly variable dance is crucial for the colony to keep track of changing resource conditions and successfully and efficiently exploit specific sources (Seeley&Visscher 1988, cited in Beekman et al. 2008).

Graph 1, Increased nectar intake due to waggle-dance recruiting. Redrawn from Beekman and Lew (2006)

In the absence of waggle dancing, bee colonies search for resources in a more spread out and random area encountering resources of variable quality (Beekman&Lew 2006), as opposed to focusing the recruitment on a patch of high profitability. Foragers will not advertise a site with low profitability nor will they return with a sugar reward, which would be used to excite nest mates (Von Frisch 1967). But searching large areas with various workers allows them to localize a particularly profitable resource that foragers will then advertise to the rest of the workers. Graph 1 above shows how observation of the waggle-dance increases the nectar-intake of the foragers, but without communication (recruitment) is as ineffective as not dancing at all.