Evidence of shark attacks on Atlantic spotted dolphins (Stenella frontalis) off Bimini, The Bahamas

Abstract

Predators can influence prey communities through direct predation and also through the costs of antipredatory behavioral responses or risk effects (Heithaus 2001a, Heithaus and Dill 2006, Wirsing et al. 2008. The risk of predation by sharks may be a selective pressure for social evolution (Norris 1994) and perhaps seasonality in calving rates (Fearnback et al. 2012) in dolphins. Sharks are considered to prey on dolphins when they attack free-swimming individuals as opposed to scavenging on terminally ill, severely wounded, or stranded animals (Heithaus 2001a). Stomach content studies have shown delphinid species consumed by at least five different shark species (Cockcroft et al. 1989, Monteiro et al. 2006. First-hand observations of shark attacks on small cetaceans (Mann and Barnett 1999, Maldini 2003, Gibson 2006, Silva-Jr et al. 2007, Turnbull and Dion 2012, Dudzinski 2 ) are rare and therefore alternative methods for assessing shark predation must be developed. One method is by assessing failed attempts; that is, documenting fresh injuries and scars on reliably reidentified dolphins that can be attributed to sharks.Here, we report on shark attacks on Atlantic spotted dolphins (Stenella frontalis) near Bimini, The Bahamas, and examine occurrence of attacks as a function of body parts, sex, and age class. We also discuss how the rate of scarring attributed to nonlethal shark attacks at our study site compares to others, and the possible shark species responsible for these attacks.The waters north and west of North Bimini, The Bahamas, have been the site of longitudinal, long-term research by the Dolphin Communication Project (DCP)

Shark bite injuries on three inshore dolphin species in tropical northwestern Australia

“…, Heithaus , Melillo‐Sweeting et al . ). With the exception of Shark Bay, Western Australia, the prevalence of shark‐inflicted scars reported in these other populations is notably lower than those reported here for Australian snubfin dolphins.…”

“…Few studies have focused on other dolphin species (but see Cockcroft for Indian Ocean humpback dolphins, Sousa plumbea and Melillo‐Sweeting et al . for Atlantic spotted dolphins, Stenella frontalis ), and investigations of shark bite prevalence on multiple, sympatric species are lacking.…”

Spatial variation in shark‐inflicted injuries to Indo‐Pacific bottlenose dolphins (Tursiops aduncus) of the southwestern Indian Ocean

“…aduncus ; Heithaus ) and Atlantic spotted dolphins ( Stenella frontalis ; Melillo‐Sweeting et al . ) suggest that injuries are less likely to occur ventrally, it is unlikely that spatial patterns in injury rates were largely affected by this bias. Calculated injury proportions, however, should be considered to be minimum estimates because of the incomplete coverage of dolphins' bodies and the likelihood that old injuries that had healed well were missed ( e.g ., Heithaus ).…”

Blacktip shark Carcharhinus limbatus presence at fishing piers in South Carolina: association and environmental drivers

“…Limbaugh (1963) activity at piers is greater during the day than at night, which results in more opportunities for sharks to feed on discarded fish. Carcharhinus limbatus can be considered opportunistic foragers (Heithaus, 2001;Melillo-Sweeting et al, 2014). Multiple observations were made of C. limbatus feeding on discarded fish and even circling cleaning stations while anglers were cleaning their fish and discarding scraps.…”