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

During 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 sptqes; 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-.

[1]  Masao Kawai,et al.  Newly-acquired pre-cultural behavior of the natural troop of Japanese monkeys on Koshima islet , 1965, Primates.

[2]  R. Connor,et al.  Two levels of alliance formation among male bottlenose dolphins (Tursiops sp.). , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[3]  John W. Pepper,et al.  Sex Differences in Patterns of Association Among Indian Ocean Bottlenose Dolphins , 1992 .

[4]  C. K. Tayler,et al.  Imitative Behaviour By Indian Ocean Bottlenose Dolphins (t uRsiops Aduncus) in Captivity , 1973 .

[5]  G. Bossart,et al.  RAY ENCOUNTERS AS A MORTALITY FACTOR IN ATLANTIC BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) , 1988 .

[6]  Syunzo Kawamura,et al.  The process of sub-culture propagation among Japanese macaques , 1959, Primates.

[7]  R. Connor,et al.  Habituated Dolphins (Tursiops sp.) in Western Australia , 1985 .

[8]  R. Wrangham,et al.  Zoopharmacognosy: the use of medicinal plants by animals , 1993 .

[9]  E. M. Dorsey,et al.  The foraging specializations of individual minke whales , 1989, Animal Behaviour.

[10]  Acoustic communication in bottlenose dolphins. , 1993 .

[11]  J. Altmann,et al.  Observational study of behavior: sampling methods. , 1974, Behaviour.

[12]  R. W. Baird,et al.  Possible indirect interactions between transient and resident killer whales: implications for the evolution of foraging specializations in the genus Orcinus , 2004, Oecologia.

[13]  B. Beck.  Animal Tool Behavior , 1980 .

[14]  D. Parry,et al.  Chemotaxonomy of Marine Sponges: Families Microcionidae, Raspailiidae and Axinellidae, and their Relationships with other Families in the Orders Poecilosclerida and Axinellida (Porifera : Demospongiae) , 1992 .

[15]  K. S. Norris,et al.  Observations of Captive and Wild Cetaceans , 1956 .

[16]  N. A. Overstrom.  Association between burst‐pulse sounds and aggressive behavior in captive Atlantic bottlenosed dolphins (Tursiops truncatus) , 1983 .

[17]  K. Imanishi,et al.  Identification : A process of enculturation in the subhuman society ofMacaca fuscata , 1957, Primates.

[18]  P. R. Bergquist,et al.  The incidence of antibacterial activity in marine demospongiae; systematic and geographic considerations , 1978 .

[19]  J M Smith,et al.  Evolution and the theory of games , 1976 .

[20]  C. Herrera.  INDIVIDUAL DIETARY DIFFERENCES ASSOCIATED WITH MORPHOLOGICAL VARIATION IN ROBINS ERITHACUS RUBECULA , 2008 .

[21]  M. Kohda.  Individual specialized foraging repertoires in the piscivorous cichlid fish Lepidiolamprologus profundicola , 1994, Animal Behaviour.

[22]  J. Hooper.  Revision of the family Raspailiidae (Porifera : Demospongiae), with description of Australian species , 1991 .