Visual and behavioral evidence indicates active hunting by sperm whales

Abstract

It is hypothesized that sperm whales employ active pursuit strategies for hunting prey, mainly deep-sea squid at great depths, but no visual evidence has been obtained to confirm this. We recorded the hunting behavior of sperm whales using animal-borne cameras and accelerometers simultaneously deployed on 17 whales, and obtained 42.8 h of diving data, including 17 715 images. A statistical comparison indicated no clear effect of light (with or without flashing white lights from cameras) on diving behavior of tagged whales. Although 98.5% of the still images were of empty water and uninformative, 5 classes of images with visible material were identified: (1) suspended material, possibly squid ink (n = 17), (2) unidentified particles (n = 4), (3) possible animal body parts (n = 2), (4) other sperm whales (n = 221), and (5) the seafloor (n = 8). All image classes were recorded at deeper depths (mean ± SD = 785 ± 140 m), except Class 4 images, which were recorded only at depths < 339 m, suggesting that tagged whales swam alone while foraging at great depths. Simultaneous use of speed and image sensors revealed that Class 1 images were associated with bursts of speed up to approximately twice (3.3 ± 1.0 m s

Sperm whale predator-prey interactions involve chasing and buzzing, but no acoustic stunning

“…In the last decades, the development of new tools to study the sounds and movements of free-ranging echolocating whales has extended our knowledge about sound production in sperm whales 21 22 40 41 , the acoustic properties of their clicks 23 42 43 , their echolocation behaviour 44 45 46 47 48 and movements during foraging 14 15 16 29 49 . However, information about how the largest tooth-bearing predator in the world tracks and captures small and agile prey is still scarce.…”

“…Aoki et al . 16 have further shown that such speed bursts are associated with squid ink and body parts passing cameras placed on the back of tagged sperm whales. These results show that sperm whales actively pursue prey during foraging dives.…”

“…However, recently Amano and Yoshioko14 have shown that sperm whales are active predators that at times accelerate to speeds of more than 3 m/s during rapid changes in body orientation and sharp turns at depth15. Aoki et al 16. have further shown that such speed bursts are associated with squid ink and body parts passing cameras placed on the back of tagged sperm whales.…”

High diving metabolic rate indicated by high-speed transit to depth in negatively buoyant long-finned pilot whales

“…Although little is known about the swimming kinematics of deep-diving toothed whales, the diving behaviour of several species such as sperm whales, beaked whales, pilot whales and northern bottlenose whales has been investigated in detail by using animal-borne recorders (e.g. Amano and Yoshioka, 2003;Miller et al, 2004b;Tyack et al, 2006;Watwood et al, 2006;Aoki et al, 2007Aoki et al, , 2012Aoki et al, , 2015Aguilar Soto et al, 2008). Sperm whales routinely dive to depths of 400-1300 m for half an hour or longer (Amano and Yoshioka, 2003;Miller et al, 2004b;Watwood et al, 2006;Aoki et al, 2007).…”

Use of time‐at‐temperature data to describe dive behavior in five species of sympatric deep‐diving toothed whales

“…, Aoki et al . ). With minimal direct observations, vertical profiles of time spent at different depth and/or temperature strata in the water column can provide useful information to deduce differences in dive strategy and habitat use between species and sexes, as well as over diurnal cycles (Johnson et al .…”