HUNT Project

Lek behavior is a biological mechanism used by male birds to attract mates by forming a group. This project explores the use of a biological behavior found in many species of birds to form leks to guide the creation of groups of robots. The lek behavior provides a sound basis for multi-robot formation because it demonstrates a group of individual entities forming up around a scarce resource. This behavior can be useful to robots in many situations, with an example scenario the case in which robots were dropped via parachute into an area and then needed to form meaningful task-oriented groups.

A. Basic Behavior


The formation of leks in order to effectively share resources and to allow all parties to be more successful is a true testament to the intelligence of these bird species. Lek behavior is unique to each particular species of bird, but there are some common themes between all of the variations. All species of birds that lek do so because the primary responsibility for the males is to copulate with females with their goal being to obtain as many successful copulations as possible. Interestingly, copulation with one male does not serve to devalue the possibility of copulations with other males, even those in the same lek, during a breeding season [2]. The behavior of species that lek is determined by available resources, both female and natural, that cannot be monopolized by any one male [3]. The most successful male of a lek, around which subordinates often gather, is termed the “hotshot”. Thus males group into leks to become more successful as a group than would be possibly individually [3]. It is predicted that if the most successful males are removed from a lek, the female visitation will decrease, but if the lesser males are removed, the female visitation will remain the same [3]. Males in a lek often display their colors and announce their presence with mating calls. Where hotshots are located in a lek, their status is determined by differences in attractiveness to potential mates or their dominance over the other males [3]. In general, our computational model will focus on male behavior in the lek. At this stage in our research, however, we are concerned solely with the spatial distribution and organization associated with this behavioral pattern rather than the intraspecies communication mechanisms. Lek settlement appears to be based on minimizing interlek competition rather than maximizing proximity to females [2]. Individual lek location is related to the traffic patterns of females [4], but not on the locations of the nest. A possible reason for this is that leks are by their nature noisy due to the males’ vocalizations, and thus should be located in more open areas, while nests should be in sheltered areas with less noise to avoid predation [2]. The number of males per lek and the amount of young males that joined the lek seems to be based on the female to male ratio throughout the season, although they also appear related to the amount of time that other males had been present in the lek [4]. This appears reasonable, since male fidelity between seasons is based on the harem size (number of females) that is encountered at a given site. Therefore, the number of established males is a good predictor of how popular a particular lek is. Since leks are located in the same area from year to year, they are not located near fruiting plains, which can be highly varied from season to season [5]. It was shown in simulation [6] that as male populations increased, the number of leks remained the same and the size of these leks increased. As evidenced by certain species, the average lek size for territorial males was between two to six males [5], but overall lek size seems to be highly influenced by female availability [4]. Both “hotshot” behavior and the hot spot hypothesis are potential indicators of lek formation, and while they are competing theories, they overlap minimally and are both useful in different ways in our robotic behavioral implementation. The hot spot theory proves useful for determining the robot lek location related to available target resources, while the hot shot theory provides a model for robot lek formation itself, independent of available resources.

B. Hotshot Behavior
An important aspect of lek behavior is the idea of the “hotshot” male. These males are highly successful and other males gather around them in order to encounter mates that they would not otherwise have attracted [2]. In normal lek behavior the “hotshot” male would be chosen based on the result of the attractiveness to potential females, but in our robot lek behavior it will be assigned a priori to a specific robot; the basis for the selection will be either the sensors available to the robot or an arbitrary assignment made before deployment. Normal bird leks have multiple “hotshots” that cluster in the middle of the lek, with secondary males clustered around them holding smaller territories. In our simulations, since the leks will be small, each will only contain one “hotshot”. We will use multiple “hotshots”, however, to create multiple leks. This is important for our behavioral implementation because these “hotshots” will be integral in both communication and leadership roles for the leks.

C. "Hot spot" Hypothesis
The “hot spot” hypothesis is hotly contested among ornithologists. It generally states that the distance between leks should be equal to a female home range plus the distance from which a lek can be detected, and that leks should be located in an area that maximizes the overlap of female home ranges [6]. Evidence that supports this hypothesis includes the observations that bird leks are preferentially located in open areas that have a high volume of female traffic, and that females visit leks near their nests [4]. For the purposes of this research, the “hot spots” for the robots to settle into will be configured based on the distribution of resources and potential traffic patterns.

[1] Figure 1 reprinted from The University of Montana Research View 2005. Photograph by Brett Walker of Dr. Dave Naugle’s group.
[2] Duraes, R., Loiselle, B. A., and Blake, J. G., “Intersexual spatial relationships in a lekking species: blue-crowned manakins and female hot spots,” Behavioral Ecology, vol. 18, no. 6, pp. 1029-1039, Aug. 2007.
[3] Höglund, J. and Alatalo, R. V., Leks, Princeton: Princeton University Press, 1995, pp. 36, 171.
[4] Gibson, R. M., “A re-evaluation of hotspot settlement in lekking sage grouse,” Animal Behavior, vol. 52, no. 5, pp. 993-1005, Nov. 1996.
[5] Westcott, D. A., “Lek locations and patterns of female movement and distribution in a Neotropical frugivorous bird,” Animal Behavior, vol. 53, no. 2, pp. 235-247, Feb. 1997.
[6] Stillman, R. A., Deutsch, J. C., Clutton-Brock, T. H., and Sutherland, W. J., “Black hole models of ungulate lek size and distribution,” Animal Behavior, vol. 52, no. 5, pp. 891-902, Nov. 1996.
[7] Georgia Tech Mobile Robot Laboratory, Manual for MissionLab Version 7.0, 2007.
[8] MacKenzie, D., Arkin, R.C., and Cameron, J., "Multiagent Mission Specification and Execution", Autonomous Robots, Vol. 4, No. 1, Jan. 1997, pp. 29-57. Also appears in Robot Colonies, ed. R. Arkin and G. Bekey, Kluwer Academic Publishers, 1997.
[9] Arkin, R.C., Behavior-based Robotics, MIT Press, 1998.
[10] Arkin, R.C., 1989. "Motor Schema-Based Mobile Robot Navigation", International Journal of Robotics Research, Vol. 8, No. 4, August 1989, pp. 92-112.
[11] Balch, T. and Arkin, R.C., 1994. "Communication in Reactive Multiagent Robotic Systems", Autonomous Robots, Vol. 1, No. 1, pp. 27-52, 1994.
[12] Balch, T. and Arkin, R.C., 1998. "Behavior-based Formation Control for Multi-robot Teams", IEEE Transactions on Robotics and Automation, Vol. 14, No. 6, December 1998, pp. 926-939.
[13] Figure reprinted from Google, in accordance with their guidelines posted online. ©2009 Google – Imagery ©2009 DigitalGlobe, GeoEye, USDA Farm Service Agency, Map data ©2009 Tele Atlas.

We are currently working on developing and running real robot experiments.

Our submission to ROBIO 2009 can be found at:
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The simulation figures found in the are shown here: