We introduce a method based on machine vision for automatically measuring aggression and courtship in Drosophila melanogaster. The genetic and neural circuit bases of these innate social behaviors are poorly understood. Highthroughput behavioral screening in this genetically tractable model organism is a potentially powerful approach, but it is currently very laborious. Our system monitors interacting pairs of flies and computes their location, orientation and wing posture. These features are used for detecting behaviors exhibited during aggression and courtship. Among these, wing threat, lunging and tussling are specific to aggression; circling, wing extension (courtship 'song') and copulation are specific to courtship; locomotion and chasing are common to both. Ethograms may be constructed automatically from these measurements, saving considerable time and effort. This technology should enable large-scale screens for genes and neural circuits controlling courtship and aggression. How are innate behaviors programmed into the genome? Answering this question requires identifying the genes that control specific behaviors, the neural circuitry on which they act, and how this circuitry controls behavior [1] [2] [3] [4] [5] . This may be attempted in model organisms such as the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster, thanks to the abundant genetic tools for marking, mapping and manipulating specific populations of neurons 6,7 , thereby enabling large-scale genetic and functional screens 8, 9 . Social behaviors, such as courtship and aggression, are of particular interest because they have strong innate components. Mating has been studied in both D. melanogaster and C. elegans using a combination of molecular genetic and cellular approaches 5, 10 . Drosophila is unique among invertebrate genetic model organisms in that it exhibits both courtship and aggression [11] [12] [13] [14] . Measuring animal behavior is difficult. Both aggression and courtship consist of rich ensembles of stereotyped behaviors, which often unfold in a characteristic sequence 13, 15 . Currently these behaviors are measured manually, which is slow and laborious. Subjective decisions by the observer may lead to difficulty in reproducing experiments. Furthermore, human observers may fail to detect behavioral events that are too quick or too slow and may miss events owing to flagging attention. These constitute substantial obstacles to conducting large-scale behavioral screens. These limitations could be overcome through automation. The first step toward measuring behavior is tracking (that is, measuring the position and orientation of animals over time 23 . In addition to lunging, it would be desirable to measure other aggressive behaviors, such as chasing, tussling, boxing (fencing) and wing threat 13 , as well as courtship behaviors. This would allow the study of whether a given mutation or environmental influence exerts a selective effect on aggression or on social interactions in general 24 . Here we describe a machine vision system designed to quantify and analyze various social behaviors in Drosophila. Actions associated with courtship, aggression and locomotion are detected from overhead videos of fly pairs. We designed our system, first, to allow detailed, accurate and reproducible quantitative measurements of individual component behaviors ('actions') that are expressed in courtship and/or aggression ('activities'), and second, to enable large-scale genetic and circuit-perturbation screens. The system is simple and inexpensive to build and replicate, functions automatically and permits measurements of multiple fly pairs simultaneously. The application of this approach, together with appropriate multiplex aggression arena configurations 25 (Supplementary Methods online), should enable large-scale genetic and circuit-based screens of these behaviors. RESULTS We used a double-arena adapted from a recently developed system 23 (Fig. 1a) . A consumer camcorder, connected to a personal computer, filmed one pair of flies per arena. This setup can be adapted to a medium-throughput mode, consisting of four double arenas (Fig. 1b-d and Supplementary Methods).
Dankert et al. REF have introduced a method for automatically measuring aggression and courtship.
Automated monitoring and analysis of social behavior in Drosophila
Nature Methods
Nature Methods
Medicine Biology