Thresher Sharks Use Tail-Slaps as a Hunting Strategy

Abstract

The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails.

Risk and resilience: High stakes for sharks making transjurisdictional movements to use a conservation area

“…Of concern is the fact that each jurisdiction is governed and policed by autonomous authorities that operate on a regional basis according to the priorities of different local interest groups (Sutherland et al, 2009). Leyte, the jurisdiction that was consistently entered by sharks tracked in this study, has an agrarian economy and is an important fishing region for Indian sardines (Sardinella longiceps), the pelagic thresher shark's main prey in this area (Oliver et al, 2013). Thresher sharks hunting sardines in these waters are frequently caught as by-catch or specifically targeted because they foul fishing gear and are perceived as a nuisance (Oliver, 2012).…”

“…Pelagic thresher sharks are one of three recognised thresher shark species (Alopiidae) that possess a unique scythe-like caudal fin that they use to strike and debilitate their prey when hunting (Oliver et al, 2013). Known to frequent warm and temperate offshore waters in the Indo-Pacific (Liu et al, 1999;Oliver et al, 2011), pelagic thresher sharks mature late, have low fecundity, are listed under Annex II (Co17) of the 5 Location Monad Shoal is a shallow coastal seamount in the Visayan Sea that rises from 250 m to 20 m depths between the provincial islands of Cebu and Leyte (N 11° 19' 06.7",E 124° 11' 31.9") ( Figure 1).…”

How sailfish use their bills to capture schooling prey

“…In some instances, posterior extensions of the body in a number of vertebrates (e.g. tails of killer whales Orcinus orca) can also be moved more rapidly than the whole body itself and are used by various large aquatic predators to facilitate prey capture [10,13,19,20]. Previous work suggests that the feeding behaviour of large aquatic vertebrates (both in fishes and cetaceans) involving whole-body attacks is largely determined by the predator-prey size ratio [11,16].…”

Injury-mediated decrease in locomotor performance increases predation risk in schooling fish

“…This is similar to the tail slaps of thresher sharks (Alopius pelagicus, [38]) and killer whales (Orcinus orca [39]), but can be a lot more controlled in targeting specific individuals. How sailfish select their target and the attack strategy (e.g.…”