Sponge Carrying by Dolphins (Delphinidae, Tursiops sp.): A Foraging Specialization Involving Tool Use?

Abstract

J. 8. BF.KGC;KT:N, P. 1997: Sponge carving by dolphins (Delphinidae, Turrip sp.): a foraging speciabzation involving tool use? F,thology 103, 4.54465. AbstractDuring long-term research on bottlenose dolphins (Tursiops sp.) in Shark Bay, K'estern Australia, sevcral individuals were observed carrying sponges, lici,inodic!pum mesemterinum, on their rostra. Over multiple years, five regularly sighted individuals were usually carrying sponges when encountered (67-100 "%I of encounters). Four additional regularly sighted individuals were observed with sponges lust one timr each. All fix e individuals that routinely carried sponges were female. Two of the anomalous, one-timc carriers were female, one was likely female, and one was male. Most observations of sponge carrying occurred within a restricted .ires, a relati~ deep water channel (8-10 m deep). Surface observations of sponge carrying, including focal animal observations, revealed a stereotyped surfacing and diving pattern, and occasional indications of prey consumption. Three hypotheses are considered regarding the function of sponge carrying: 1. dolphins wcrc playing with the s p t q e s ; 2. the sponges contain some compound of use to the dolphins (e.g. for medicinal purposes); and 3. the sponges were used as a tool to aid in foraging. The foraging tool hypothesis is hest supported, but thc exact manner in which sponges are used remains to be discovered. Sponge carrying is a beharioural specia'iTation, probably involving foraging, and regularly engaged in by onl! a small proportion of female dolphins in Shark BaJ-.

Ecological characteristics contribute to sponge distribution and tool use in bottlenose dolphins Tursiops sp.

“…Data specific to dolphins observed carrying sponges ('spongers') identified from both transect and non-transect surveys from 2007 to 2009. Channels: depth ≥10 m; shallows; depth <10 m Similarly, in the eastern gulf of Shark Bay, sponges and spongers were concentrated primarily in the deeper waters of the channels, and sponge carrying was largely limited to deep waters where sponges were abundant (≥8 m; Smolker et al 1997, Sargeant et al 2007). The channels in the eastern gulf, however, are generally shallower (5 to 6 cm, Nahas et al 2005) than those in the western gulf (10 to 16 m; Fig.…”

“…One of these tactics involved the use of sponges as foraging tools. Dolphins carry conical sponges Echinodictyum mesenterinum on their rostra, a behaviour termed 'sponging' (Smolker et al 1997). Sponges are thought to serve as a protective tool while the dolphins are foraging for prey in the substratum (Smolker et al 1997).…”

“…Dolphins carry conical sponges Echinodictyum mesenterinum on their rostra, a behaviour termed 'sponging' (Smolker et al 1997). Sponges are thought to serve as a protective tool while the dolphins are foraging for prey in the substratum (Smolker et al 1997). Several studies have shown that sponging is a foraging tactic exhibited by a minority of individuals within the population (e.g.…”

Cultural transmission of tool use by Indo-Pacific bottlenose dolphins (Tursiopssp.) provides access to a novel foraging niche

“…The sponges are thought to be used as a protective tool against abrasion from sharp objects, stingray barbs or noxious organisms [18,25]. Previous evidence suggests that sponging may enable dolphins to target fishes without swim bladders, as these prey items are not easily detectable with echolocation against a complex substrate [25].…”

Abundance, survival and temporary emigration of bottlenose dolphins (Tursiops sp.) off Useless Loop in the western gulf of Shark Bay, Western Australia

“…This ongoing research has a strong focus on behaviour, ecology, genetics, communication and social structure, making it one of the most well renowned dolphinresearch sites in the world (Connor et al 2000b). Shark Bay's bottlenose dolphins live in a fissionfusion society with a complex social organisation (Connor et al , 2000b(Connor et al , 2011Smolker et al 1992) and exhibit a remarkable variety of foraging strategies within a population (Smolker et al 1997;Connor et al 2000a;Mann and Sargeant 2003;Allen et al 2011). The density of the dolphin population may well drive such behavioural complexity.…”