#SURFERS­FORDINNER

TWEET­ING SHARKS WARN BEACH­GO­ERS THEY’RE NEAR

Guru Magazine - - Na­ture -

De­pend­ing on your age and predica­ment, you might have been ei­ther happy or wor­ried when your mom joined the world of so­cial me­dia. Whether you’re ec­static to share lit­tle Burt’s tenth por­trait of the day or you find your­self fran­ti­cally delet­ing ev­i­dence of that party you went to, your mom – and maybe even your grandma – are there to stay. So­cial me­dia is now the norm and the whole world is on it. Yet so­cial me­dia has even more sur­prises for us: it’s cross­ing the species bound­ary. No, not just pets, but preda­tors too: Sharks liv­ing off the coast of Western Aus­tralia have just joined Twit­ter. “Surf Life Sav­ing WA” is a Twit­ter ac­count that aims to pro­tect beach­go­ers and has amassed over 31,000 fol­low­ers so far. The ‘tweets’ in­clude sum­maries of first aid as­sists, pic­tures of brave res­cues on the wa­ter, and tweets from the lo­cal sharks: “Fish­eries ad­vise: tagged Tiger shark de­tected at Warn­bro Sound re­ceiver at 06:14:00 PM on 13-Feb-2014” Yes, you read that right: sharks that tweet. Ac­cord­ing to their web­site, the De­part­ment of Fish­eries in Western Aus­tralia has tagged 326 sharks – in­clud­ing Great Whites, Whaler and Tiger Sharks – with acous­tic trans­mit­ters. When a tag is then de­tected by one of the 320 or so acous­tic re­ceivers in the wa­ter, a tweet is sent out. This pro­gram was set up in re­sponse to the high num­ber of fa­tal shark at­tacks in Western Aus­tralia in re­cent years, in­clud­ing six in the past two years alone. But Dr. Rory McAu­ley, prin­ci­pal re­search sci­en­tist with the De­part­ment of Fish­eries, says that the tag­ging pro­gram isn’t just to help beach­go­ers stay safe: it also con­trib­utes to im­por­tant shark re­search. So far, the tag-to-tweet pro­gram has done a great job of alert­ing peo­ple to nearby sharks. The one ob­vi­ous snag, how­ever, is that not

all sharks are tagged. Sharks can swim vast dis­tances: one tagged Great White named “Ni­cole” trav­eled an amaz­ing 20,000 km from Africa to Aus­tralia in 2005. It’s likely that many sharks in the wa­ters of Western Aus­tralia are only tem­po­rary vis­i­tors, mak­ing it all but im­pos­si­ble to tag every one. But it’s a good start, and shark-sym­pa­this­ers much pre­fer it to the re­cent govern­ment culling pro­gram, which set out to kill any sharks over 3 me­ters long. Ac­cord­ing to the web­site Sup­port­OurSharks.com, over 100 shark ex­perts and 33,000 oth­ers have spo­ken out against the culling. ( You can see their let­ter here.) As a top preda­tor, sharks are ‘key­stone species’ – they have a very im­por­tant ef­fect on the com­mu­nity around them. If, for ex­am­ple, sharks weren’t there to eat sea tur­tles and dugongs, their pop­u­la­tions would in­crease; all those ex­tra hun­gry mouths to feed would lead to an over-graz­ing of sea grass. (Of course, this ex­am­ple assumes these pop­u­la­tions would ex­pe­ri­ence no hu­man in­ter­fer­ence – some­thing of a vain hope given that both sea tur­tles and dugongs are clas­si­fied as ‘vul­ner­a­ble’ at best and ‘crit­i­cally en­dan­gered’ at worst.) As sea grass pro­vides habi­tat and food for many species, los­ing it would have far-reach­ing ef­fects. In this way, and in count­less oth­ers, sharks are vi­tal to the health of the oceans. Sharks help to keep the sys­tem in bal­ance. Ul­ti­mately, this shark tag­ging pro­gramme may help es­tab­lish a healthy bal­ance be­tween sharks and surfers. But in the mean­time, don’t for­get to check your Twit­ter feed be­cause at least some of them will tweet a hello when they’re around.

Find out more:

• The In­ter­na­tional Union for Con­ser­va­tion of Na­ture and Nat­u­ral Re­sources Red List

• Car­char­o­don car­charias (Great White Shark) • Ga­le­o­cerdo cu­vier (Tiger Shark)

• Car­charhi­nus am­blyrhyn­chos, Black­tail reef shark

• Transoceanic Mi­gra­tion, Spa­tial Dy­nam­ics, and Pop­u­la­tion Link­ages of White Sharks

ABOVE: Re­searchers tag­ging a shark.

ABOVE: An acous­tic trans­mit­ter, used to track the shark’s move­ments.

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