Army Ants Swarm Harvestman

Video © Tim Brown /

A harvestman (order Opiliones) is swarmed by army ants (Eciton burchellii), but as with several other arachnids and some insects, it remains motionless, thereby escaping unscathed. Eciton army ants rely almost exclusively on vibrational and chemical cues to detect prey, and they refrain from biting or stinging inanimate objects. Because additional workers are recruited only to subdue active prey items, the foraging swarm of ants eventually passes, leaving the surviving harvestman in their wake. The highly coordinated actions of a foraging ant swarm, often involving hundreds of thousands of individuals, illustrate how simple behavioral rules adopted by individuals can result in highly complex and unpredictable behavior at the level of the system as a whole.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 1, ''Principles of Animal Behavior"; chap 11, ''Foraging''; chap 12, "Antipredator Behavior," T. Brown, ''Modeling Behavioral Rules and Self-Organization in New World Army Ant Swarms,'' in Proceedings of the 2nd International Workshop on the Mathematics and Algorithms of Social Insects, ed. C. Anderson and T. Balch (Atlanta: Georgia Institute of Technology, 2003), pp. 25-32.

Differential Responses to Stimulus

Carl Smith

Simple, yet highly effective stimuli serve to elicit certain behaviors. As Niko Tinbergen demonstrated in his pioneering research on the releasers of courtship and aggressive behavior in three-spined sticklebacks (Gasterosteus aculeatus), the red jaw and throat of breeding males are potent releasers of aggression in conspecific males and act to release courtship behavior on the part of gravid females. In this sequence of clips, three-spined sticklebacks show virtually no response to a blue or green object, but show obvious attraction to an otherwise identical red object placed in their midst. Differential responses of this sort exemplify how animals have been selected to attend preferentially to certain stimuli among the broad range of stimuli present in their environment. Sensory biases of receivers that appeared originally in the context of foraging can be exploited in terms of attracting both prey and mates. Actual mate choice decisions, however, typically involve more refined levels of assessment after the initial release of investigatory behavior.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: W. W. Norton, 2013), chap. 1, ''Principles of Animal Behavior''; chap. 7, ''Sexual Selection." C. Smith, I. Barber, R. J. Wootton, and L. Chittka, ''A receiver bias in the origin of three-spined stickleback mate choice,'' Proceedings of the Royal Society of London Series B, Biological Sciences 271 (2004), pp. 949-955.

Moth Puddling

Scott Smedley, Tom Eisner

Many butterflies and some moths aggregate at sources of water (shown here), drinking copious amounts of liquid, and then void that liquid in anal jets projected up to half a meter from their bodies. Such behavior is called ''puddling.'' Adult small pebble moths (Gluphisia septentrionis) are prodigious puddlers, in that individuals weighing on the order of 80 mg will puddle for several hours, pumping up to 50 ml of water through their gut in that time, which is the equivalent of an 80 kg human ingesting and passing some 50,000 liters of water in the same period! Such behavior is performed by male lepidopterans, which not only obtain sodium for themselves, but also provide their female mates with a nuptial gift of sodium that the females bestow on their eggs, increasing their sodium content up to four times the level documented in non-puddler sired eggs.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: Norton, 2013), Chap. 1, ''Principles of Animal Behavior''; Chap. 7, ''Sexual Selection.'' S. R. Smedley & T. Eisner, Sodium: A male moth's gift to its offspring, in Proceedings of the National Academy of Sciences U.S.A. 93 (1996), pp. 809-813.

Zebra Finch Courtship and Mating

Frank R. Castelli, Kristina O. Smiley; E. Adkins-Regan Lab, Cornell University

In studying behavior, we must be aware that the methods we employ sometimes alter the behavior of the animals of interest. For instance, while colored leg bands are commonly used to mark individuals in studies of birds, those leg bands themselves can have a pronounced influence on the birds' social preferences. Zebra finch (Taeniopygia guttata) females, for instance, preferentially associate with males having red leg bands, and avoid males bearing light blue or green leg bands. This preference is presumably attributable to selection favoring female mating preferences for males with deeper red bills and leg coloration (readily visible among the birds in the present clip), which honestly advertise male fitness. The video clip begins with a male and female zebra finch with the male on-screen and others offscreen both calling. The next segment shows a male approaching a female and the female moving away. In the penultimate segment, the female in the center performs a gaped-mouth threat display while to her left a male beak wipes two times (a common social as well as maintenance behavior in this species); the pair in the upper right are clumping and beak fence briefly. In the final segment, an unpaired male mounts a female who is nonreceptive, and the female moves away while the male from the pair to the lower right gives chase.

FURTHER READING: Lee A. Dugatkin, Principles of Animal Behavior, 3rd ed. (New York: Norton, 2013), Chap. 1, ''Principles of Animal Behavior''; Chap. 7, ''Sexual Selection.'' N. Burley, ''Wild zebra finches have band-colour preferences,'' in Animal Behaviour 36 (1988), 1235-1237.