6.2 Intra-species communication & Foraging in social insects  (Page 8/9)

How honeybees cope with waggle dance informational conflicts

There is a notable conflict between personal and communicated information. This conflict is present within the waggle dance itself. Marco and Menzel show that, because of path integration, a scout’s dance may encode both the actual distance traveled as well as the shortest theoretical distance to a desired destination (2005). Gould also noticed the discrepancy between the actual location of the food source and where the foragers following the waggle-dances arrived (1974). Actual and theoretical directions and distances to locations are obscured because of this, and can therefore vary widely from scout to scout. How will an inexperienced worker interpret these highly variable signals? Tanner and Visscher’s study shows that, surprisingly that the range of possible locations expressed in the dances is more variable then the flights of newly recruited bees (2008). It is by averaging the observed waggle-runs that the recruits are able to fine-tune their trajectory. This is precisely how A. mellifera reaches its colony ‘consensus.’ Tanner and Visscher’s data show that those bees that observe the waggle-runs the longest will have a more accurate path trajectory. Also, those bees that advertise longer will be more likely to be observed and followed (2008). Furthermore, the most profitable locations are advertised more vigorously, more at length and by more individual recruiters than those that are less so (Oldroyd et al. 2008), and are therefore more likely to be observed. This is conflict and competition at its most productive and beneficial to the colony.

There are clearly certain disparities between personal and communicated information. Therefore, for these complex informational systems to succeed, a certain amount of individual decision-making is also needed. For example, if the odor of a certain flower brought by a scout-dancer is familiar to a dance observer but the demonstrated location is unknown, a bee will use preexisting private information to forage locations of known food sources and will disregard the new information conveyed in the waggle dance (Grüter et al. 2008). In one study, Grüter et al. found that 82% of tested bees returned to previously visited food patches when they received unknown spatial and scent information (2008). Workers on the surface of the hive will swarm recruiters that return often with the scent of a certain flower on them. Grüter et al. informs us that often times that, depending on the specific pollen detected on the nest mate, the worker may have sufficient knowledge to begin foraging at previously visited sites. They show that this reactivation would lead 93% of experienced foragers with divergent private data to return to an old foraging location (2008).

Box 2: quorum&Tandem runs in the ant temnothorax curvispinosis

Ants communicate predominantly through olfactory cues, but one particular behavior called Tandem Running is used to recruit foragers to a new location. It involves slowly guiding a worker along the path to the resource or nest site. The follower maintains contact with the guide with its antennae (see image below). Tandem running increases the number of recruited ants as well as informing them on location of a resource or possible nest, whether or not the run is finished to completion. Ants may supplement this information by laying down pheromone trails on the return to nest from a food source (Chu et al. 2003). Pratt (2008) notes that this process is slow and costly to the ants so they must know when to disengage from this behavior and began gathering or ‘transporting,’ where they literally carry their nest mates to the newly discovered site. The ants are able to decide, by monitoring the group of nest mates at the new site for when it has enough workers already established there, when it will be most profitable to stop tandem runs and begin transports (Pratt 2008). This is an example of the quorum rule in use. There is a close analog to this behavior in honeybees. Once a new nest site has been decided on, certain scouts will fly quickly through the moving swarm in order to ‘point’ the new recruits in the correct direction (Beekman et al. 2006). Ants are typically members of large-sized colonies that can number in the millions. This means that often they rely more on group foraging and chemical signals and less individual and learned knowledge (Beckers et al. 1989).