White shark behaviour altered by stranded whale carcasses: Insights from drones and implications for beach management

• White sharks (Carcharodon carcharias) are attracted to and scavenge on floating whale carcasses. However, little is known about how stranded whale carcasses may affect their behaviour. With increasing whale populations and beach stranding events, sharks may be attracted to nearshore waters at carcass sites, increasing the potential conflict with human use. Here, we used aerial drones to assess whether white shark behaviour around stranded whale carcasses differs from their behaviour away from carcasses. We quantified white shark behaviour by measuring swim speed, net velocity, straightness and sinuosity of shark tracks, as well as the total length of each shark. White sharks in the vicinity of whale carcasses travelled at 0.46 m s(-1) (+/- 0.06 SD) faster, were 0.26 m (+/- 0.15 SD) longer, swam tracks that were 0.15 (+/- 0.11 SD) lower on the straightness index, and showed more sinuous tracks by 0.07 (+/- 0.02 SD), compared to sharks away from a carcass. The presence of a stranded whale carcass may, therefore, significantly altered the behaviour and size of white sharks close to shore. As white shark activity increases in a relatively small nearshore area, which was indicated by decreased straightness and increased sinuosity, there may be an elevated risk of shark interactions with water users in the vicinity of stranded whale carcasses.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

Nyckelord

Carcharodon carcharias

Drone

Elasmobranch

Remotely piloted aircraft

system (RPAS)

Whale carcass

unmanned aerial vehicles

carcharodon-carcharias

abundance

dynamics

patterns

bay

Oceanography

Water Resources

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