02081nas a2200205   4500008004100000245011800041210006900159260004000228300001100268490000600279520140300285653001701688653001501705653001701720100002701737700002301764700001701787700002001804856005101824       2010                        eng d00aNovel Acoustic Technology for Studying Free-Ranging Shark Social Behaviour by Recording Individuals' Interactions0 aNovel Acoustic Technology for Studying FreeRanging Shark Social   bPublic Library of SciencecFebruary  ae9324+0 v53 aGroup behaviours are widespread among fish but comparatively little is known about the interactions between free-ranging individuals and how these might change across different spatio-temporal scales. This is largely due to the difficulty of observing wild fish groups directly underwater over long enough time periods to quantify group structure and individual associations. Here we describe the use of a novel technology, an animal-borne acoustic proximity receiver that records close-spatial associations between free-ranging fish by detection of acoustic signals emitted from transmitters on other individuals. Validation trials, held within enclosures in the natural environment, on juvenile lemon sharks Negaprion brevirostris fitted with external receivers and transmitters, showed receivers logged interactions between individuals regularly when sharks were within 4 m (\~{}4 body lengths) of each other, but rarely when at 10 m distance. A field trial lasting 17 days with 5 juvenile lemon sharks implanted with proximity receivers showed one receiver successfully recorded association data, demonstrating this shark associated with 9 other juvenile lemon sharks on 128 occasions. This study describes the use of acoustic underwater proximity receivers to quantify interactions among wild sharks, setting the scene for new advances in understanding the social behaviours of marine animals.10abioacoustics10amonitoring10apeer-to-peer1 aGuttridge, Tristan, L.1 aGruber, Samuel, H.1 aKrause, Jens1 aSims, David, W.  uhttp://dx.doi.org/10.1371/journal.pone.0009324