Trophic interaction between white shark (Carcharodon carcharias
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Trophic interaction between white shark (Carcharodon carcharias
Trophic interaction between white shark (Carcharodon carcharias) and cetaceans: a comparison between Plioceene and Recent data from central Mediterranean Sea Giovanni Bianucci (1), Michelangelo Bisconti (1), Walter Landini (1), Tiziano Storai (2), Marco Zuffa (3), Silvia Giuliani (4), Angelo Mojetta (5) (1) Dipartimento di Scienze della Terra, Università di Pisa, via Santa Maria 53, 56126, Pisa (Italy). E-mail: [email protected]; [email protected]; [email protected]. (2) Museo Civico di Scienze Naturali della Valdinievole, P.zza Leonardo da Vinci 1, 51017, Pescia, Pistoia (Italy). E-mail: [email protected]. (3) Museo "Luigi Donini", Via F.lli Canova 49, 40068, San Lazzaro di Savena, Bologna (Italy). (4) C.I.B.M. Centro Interuniversitario di Biologia Marina, Piazzale Mascagni 1, 57100, Livorno (Italy). (5) Civica Stazione Idrobiologica e Acquario di Milano, viale Gadio 2, 20121, Milano (Italy). E- mail: [email protected]. 1 Abstract Evidences of white shark-cetacean trophic interactions from Pliocene and Recent central Mediterranean Sea are examined. The analysis of Recent data (stomach content reports, eyewitnesses' depositions about predation on living cetaceans and scavenging signs on the carcasses) shows that cetaceans represent a significant component of the diet of Carcharodon carcharias. Fossil evidences (cetacean bones marked by white shark bites and white shark teeth in close relation with skeletal remains of cetaceans) suggest sharks-cetaceans trophic interaction in the Pliocene too. A comparison between Recent and fossil data lets us presume that in the Pliocene both Mysticeti and Odontoceti were equally represented in the Carcharodon carcharias diet. On the contrary in the Recent the white shark interaction is principally directed to little-sized toothed whales and just rarely to mysticetes baleen whales. This change could be due to both the general reduction of the living white shark body size and the diminished diversity of the cetacean assemblage. Key words White sharks, Cetaceans, Mediterranean Sea, Pliocene, Recent, Trophic interactions. Introduction 2 Predation events on cetaceans are principally due to white sharks (Carcharodon carcharias) and killer whales (Orcinus orca) (Tomilin, 1967; Philo et al., 1993). The interactions between predators and preys are not completely cleared by behavioural studies and a pacific coexistence of both is sometimes recorded (Tomilin, 1967). In general, white sharks attack preferably toothed whales (Slipp and Wilke, 1953; Day and Fisher, 1954; Arnold, 1972; Corkeron et al., 1987; Cockcroft et al., 1989; Cliff et al., 1989; Long, 1991; Bruce, 1992; Long and Jones, 1996) while the interaction with baleen whales is limited to scavenging actions (Long and Jones, 1996). The whale population of the Mediterranean Sea is formed by several species of toothed whales and essentially one gigantic baleen whale (the fin whale: Balaenoptera physalus). Other mysticetes are occasionarily observed. Some authors reported that the Mediterranean whales are sometimes engaged in predatory interactions due to white sharks (Cigala-Fulgosi, 1990; Fergusson, 1996; Mojetta et al., 1997). The fossil record relative to the time interval between about 5 to 1.6 million years (spanning to the Pliocene time) suggests that this trophic relationship could be relatively old. Carcharodon carcharias fossil remains consist primarily of teeth that are frequently found in the Pliocene outcrops of the Italian peninsula. They are sometimes found in direct association to whale remains suggesting ancient interactions. Cigala-Fulgosi (1990) described in great detail the bite marks made by a white shark on a Pliocene dolphin providing an experimental paradygm to diagnosize white shark bites on fossil bones in absence of shark's teeth. His work supplements the initial attempt by Deméré and Cerutti (1982) that documents a white shark attack on a little late Pliocene mysticete. Other reports are older and involve both mysticetes and odontocetes of Italy (Portis, 1883) and Southern Argentine (Frenguelli, 1928). Purdy (1996) extends the likelihood of direct interactions analyzing the contemporaneous presence of white shark 3 teeth and cetacean remains in North Atlantic geological formations characterized by both reduced temporal and areal extension. In this work, a new analysis of fossil cetaceans is carried out to search clues of interactions with white sharks in the Pliocene time. The study was made in the light of the current evidence about Carcharodon carcharias predation on Mediterranean whales. A comparison between Recent and Pliocene data was made to hypothesize possible changes in the diet of the white shark in the last five million years. Materials and methods Recent data Several kinds of sources were employed to gather evidences on the interactions between white sharks and cetaceans in the living population of the central Mediterranean Sea: a) scientific publications; b) non-specialistic publications on newspapers and other journals; c) communications by eyewitnesses. In general, the likelihood of the data obtained by scientific publications (point a) is considered high; about the likelihood of the data obtained by sources as those in points b and c, here, just some informations were considered useful for the investigation. These are the ones that were supported by evidence as photographies, multiple verifications and expertise of the witnesses. Pliocene data Informations on interactions between Pliocene white sharks and cetaceans were obtained by analysis of both literature and skeletal remains. Three criteria were chosen to evaluate the grade of likelihood of the hypothesized interactions: a) presence of bite 4 marks on the whale bones (Portis, 1883; Frenguelli, 1928; Cigala-Fulgosi, 1990; Deméré and Cerutti, 1982); b) direct association of white shark teeth and cetacean bones, that means the teeth were found over or in close proximity of the cetacean bones (Borselli and Cozzini, 1992; Capellini, 1865); c) coexistence of both shark teeth and cetacean remains within the same deposit (Purdy, 1996). The first criterion is presumed to provide the highest likelihood but it does not clear the kind of interaction (attack or scavenging). Moreover, the signs on the bones allow to identify the shark just when supplementary informations are available, as those due to the marginally serrated teeth belonging to Carcharodon carcharias (Deméré and Cerutti, 1982; Cigala-Fulgosi, 1990). About the second criterion, current evidence discussed later will show that predatory interactions exist in which the shark does not leave bite marks on the bones of the prey; for this reason, the finding of shark's teeth in close association with cetacean remains should be considered as an evidence of interaction. In general, the fossilization process is a rare fact; to assume that a shark tooth and some cetacean bones have been fossilized in different times within the same few m2 is an unlikely event. Cetacean bones and closely associated shark's teeth could be the remains of an ancient predatory or scavenging interaction even if the bones of the prey are not marked by bite signs. A single bite on the ventral addominal portion as that in Fig. 1 does not leave bite marks on the cetacean bones and similar attacks are presumed to have been possible also during Pliocene. The third criterion provides the lesser likelihood to interpret interaction types between cetaceans and white sharks. In general, it is difficult to evaluate the contemporaneous presence of both vertebrates when they are found in weak association. The main part of the fossil specimens are difficult to place chronologically within the stratigraphic 5 frameworks of deposits that span for some million years. Moreover, the finding of shark's teeth and cetacean remains on the same stratigraphical horizon but not in close association should be considered a clue of coexistence but not of interaction. Results Interactions in Recent central Mediterranean Sea In Table 1, events are described showing that both toothed (21 records) and baleen whales (2 records) are alimentary items for Carcarodon carcharias. The geographical distribution of these records is reported in Fig. 2. Mediterranean interactions between mysticetes and white sharks are rare and their reports are old. Parona (1896) wrote about close associations of many white sharks to some carcasses of probable Balaenoptera musculus (blue whale) or Balaenoptera physalus (fin whale). This pattern is known in other seas but it appears as exceptional in Mediterranean, where just one or two white sharks are seen together. Damiani (1911) reported a probable attack on a rorqual stranded at Marciana Marina; this is the first time in which an interaction between white shark and a living mysticete is observed. It must be remarked that the rorqual was possibly suffering and unable to escape. Parona's (1896) and Damiani's (1911) identifications of predators and preys are reasonable but not completely sure. Relatively to the 21 toothed whale records, the involved species are the following: Delphinus (Postel, 1958), Tursiops (Marcantonio and Cataldo, pers. comm., 1980; Centro Studi Cetacei, 1988; Vanadie, pers. comm., 1988), Stenella (Centro Studi Cetacei, 1999), Physeter (Fergusson, 1996), and maybe Phocoena (Moreau, 1892). 6 All the attacks in which the predator's size is known are referable to very large white sharks (>400 cm in length). This consideration induces to hypothesize that cetaceans represent a trophic target for white sharks near to the sexual maturity or completely mature (range of sexual maturity lenght by Casey and Pratt, 1985). The reference database for white sharks/cetaceans trophic interactions uses the following sources: a) stomach contents reports; b) eyewitnesses' depositions about predation on living cetaceans; c) scavenging signs on the carcasses. Stomach contents - An extensive bibliographic search provided 274 records relative to several aspects of the Mediterranean Carcharodon carcharias life cycle ( Mojetta et al., 1997; Storai et al., in press; Storai and Zuffa, unpublished data). Among these, 33 records are reports on stomach contents whose analysis furnished data on the relative presence of a given item in the white shark diet. From a quantitative viewpoint, the cetacean component of the white shark diet is highly significant and it covers as much as one-third (17 specimens found into white shark stomaches: 28.91%; total items found: 59) of the whole diet of the white shark. It is remarkable that one-third of the examined sharks beard cetaceans into their stomachs (11 cases on 33). Unfortunately, the sample is statistically too little to allow inferences with high degree of confidence. Moreover, the data from literature are too generic (the authors wrote about the presence of large items as tunas, swordfish, tortoises, other sharks, humans etc., but they did not describe every other little things they found within the stomachs). For this reason, lacking supporting evidence, every detailed inference on the diet of the Mediterranean white shark risks to be deceptive. However, based on the current database, to hypothesize a wide trophic range for the Mediterranean Carcharodon carcharias appears correct. Possibly, this wide trophic range should result from the difference between the Mediterranean biota and other 7 biotas around the world, where white sharks show certain trophic specializations. In fact, non-Mediterranean Carcharodon carcharias populations seem closely associated to large low-diversity communities of marine mammals or other vertebrates while in Mediterranean sea the prey availability is characterized by many highly diversified alimentary items. Eyewitnesses' depositions about predation on living cetaceans - Just one report exists that documents an attack on a living cetacean (Condorelli Francavilla and Ferrando, 1909): during the first attack, a large white shark excided the caudal fin of a little Delphinidae caught by fishmen, in the second attack, the same shark scoffed the entire whale. From this description it is impossible to establish a pattern attack to a living whale due to the handicapped situation of the prey. Spoken reports documented the presence within white shark's stomachs of odontocetes whose body was cut in two pieces, but it is not possible to discriminate between predation and scavenging events (Abela, pers. comm., 1987; Giudici and Fino, 1989). Scavenging marks on carcasses - Several elasmobranches perform scavenging operations on floating cetacean carcasses (Long and Jones, 1996), but the records listed in table 1 are reasonably ascribed to Carcharodon carcharias due to the descriptions of bite morphology and dimension (Centro Studi Cetacei, 1988, 1999; Vanadie, pers. com., 1988; Babboni, pers. com., 1995). All of the bites are found in the abdominal zone of the cetacean body. This observation suggests a kind of attack to a prey too large to be scoffed as a whole (Anonymus, 1967; Terrasa, 1988; Chiocca, pers. com., 1990; Lipey, 1994). The comparison between the Mediterranean data and the ones obtained from the Sarasota bay (Florida) Tursiops population (Bortolotto, 1998) shows a difference. In fact, the Florida white sharks seem to attack Tursiops from a craniodorsal direction. 8 However, due to the fact that the main part of the Sarasota bay Tursiops were living after the attack, it is likely that the Florida data are to refer to failed attacks. Vanadie (pers. com., May, 1988) described a 3-meter-long Tursiops carcass showing a wide injury clearly due to a large shark attack near to Bovo Marina (Fig. 1). The bite dimension (diameter about 50 cm) implies, with an high degree of confidence, the involvement of a white shark. Thorough this attack the shark extracted a large portion of both abdominal muscles and bowel without damaging the cetacean skeleton. Interactions in Pliocene central Mediterranean Sea Fossil teeth of Carcharodon carcharias are known from many Pliocene Italian localities both from paleotyrrenian and paleoadriatic areas, even if they are less abundant than other shark teeth, as those referred to Isurus spp. and Carcharinus spp. (Cigala-Fulgosi, 1990, Landini, 1977). Fossil cetaceans are relatively frequent in the marine Pliocene sediments of Italy, particularly in Piedmont, Emilia Romagna and Tuscany regions (Bianucci, 1996, 1997a,b,c; Bianucci and Landini, 1999; Bianucci et al. 1998; Bisconti, 2000) and often they have been collected in the same deposits of white shark teeth. In some cases direct interactions of shark and both odontocete and mysticete cetaceans are documented by fossil data. Bibliographical and new records are listed in Tab. 2 and discussed below. The geographical distribution of these records is reported in Fig. 3. White shark-odontocete interactions - Portis (1883) examined five odontocete records from Pliocene sediments of Piedmont with supposed bite marks of Carcharodon or generic "shark" teeth. Evident signs on the ribs and vertebrae of a delphinid skeleton collected from Bagnasco (Asti province) were reported. The specimen was originally 9 described (Portis, 1886) as the holotype of the species Steno bellardii but recently it has been referred (Bianucci,1996) to Astadelphis gastaldii. We have examined in detail the signs on the bones of this delphinid and no trace of serration, both in cutting and scraping action as described by Deméré and Cerutti (1982) and Cigala-Fulgosi ( 1990) for white shark attack, have been observed. Consequently the attack is not referable to a white shark, as supposed by Portis (1883), but probably to an isurid shark, whose teeth have not serrations. Regarding the bite marks on the other odontocete records described by Portis (1883), we doubt that these are consequences of shark attacks, and particularly the signs on a lumbar vertebra of a supposed delphinid are probably invertebrate bioerosion. Cigala-Fulgosi (1990) described in great detail an almost complete skeleton belonging to a Delphinidae in which he found several signs of attack or scavenging by a Pliocene white shark. The specimen comes from the Rio Stramonte Piacenzian (Piacenza, Emilia Romagna) and was referred to Tursiops cortesii capellini by Pilleri (1987) and CigalaFulgosi (1990) and to Hemisyntrachelus cortesii by Bianucci (1996). There are evident bite signs on the bones of this specimen. Cigala-Fulgosi (1990), analysing the marks, hypothesized that the shark attacked or scavenged the ventrolateral portion of the whale. Based on the particular serrated signs, he proposed that a Carcharodon carcharias was the predator or the scavenger. Together with the attacked or scavenged Hemisyntrachelus cortesii, other cetacean remains were found, among which the Hemisyntrachelus cortesii holotype (Cuvier, 1823), an incomplete Hemisyntrachelus sp. skull (Bianucci, 1997b), and the dentary, ribs and the vertebra that constitute the Balaena paronai holotype (Del Prato, 1900). White shark's teeth from the Rio Stramonte Pliocene sediments (spanning from 3.2-3.0 million years; see Bianucci et al., 1998) were described by De Stefano (1912). This finding is an indirect evidence for a 10 coexistence between white sharks and toothed whales in this area of the Paleoadriatic sea. It can be hypothesized that the highly diffuse Hemisyntrachelus was an alimentary source for Carcharodon carcharias. Cigala-Fulgosi (1990) discussed also another specimen bearing bite marks. It is a single Delphinidae rib on which there are signs made by a white shark. In one case, an odontocete skeleton was found in close association with two white shark's teeth but its bones did not bear bite marks. The specimen belongs to Hemisyntrachelus cortesii (Bianucci, 1997a) and it comes from the Campore quarry near Salsomaggiore (Parma province, Emilia Romagna). The skeleton lacks the arms, many lumbar and all of the caudal vertebrae; the skeletal remains are almost completely articulated but a disarticulation pattern is observed among the anteriormost portion of the postcranial skeleton (Fig. 4). Particularly, the anterior dorsal vertebrae are dislocated and the ribs are dispersed and cracked. Within the cervical-anterothoracic area, on the right side of the whale body, two Carcharodon carcharias teeth were found that were very near to the ribs. A random association between the teeth and the cetacean remains should be considered very unlikely. The depth of the bottom on which the dolphin was deposed is esteemed to be 200-400 m (upper epibathyal; Bianucci, 1997a) is in the range of occurrence of living white sharks. However, Carcharodon carcharias makes rarely scavenging onto preys deposed on the bottom. For this reason, it is reasonable to suppose that the white shark attacked the living dolphin or its floating carcass. The lacking of the arms and the caudal region of the body supports the hypothesis of floating transport of the carcass because these portions could be detached during decomposition before the deposition of the cetacean on the bottom (Shäfer, 1972). 11 White shark-mysticete interactions - Records from Tuscany are noteworthy and comprehend essentially balaenids. Capellini (1876) described bite signs on the ribs and fragments of vertebrae of dwarf balaenids that he identified as Balaenotus found from Poggiarone (Siena province) and S. Murino (Pisa province) near Siena. He supposed that the signs were due to human activities on the bones. After some years, Portis (1883) identified the marks as evidence of interaction with Carcharodon sharks. We consider correct the attribution of these signs to shark bites but we believe that they are not the result of white shark attack because completely different from signs described and illustrated by Cigala-Fulgosi (1990) and Deméré and Cerutti (1982). From the San Miniato basin (including an area between Florence and Pisa, Tuscany), two other balaenids were found in close association to white shark's teeth. Borselli and Cozzini (1992) described the excavation of a large bowhead whale (Balaena sp.) bearing eight white shark's teeth in close proximity. The whale was represented by an almost articulated skeleton whose arms and scapulae were shifted at the level of the lumbar vertebrae. It is likely that the decomposed whale went under a taphonomic process that shifted anteriorly the axial body (skull and vertebral spine) leaving the arms behind. A single white shark tooth was found between the scapula's glenoid cavity and the distal epiphysis of the disassociated ulna (Fig. 5). It is likely that the very close association between shark's teeth and the skeletal remains constitutes a real clue of direct interaction between the large bowhead whale and a white shark. The cetacean body was deposited on a bottom which was not more than 30 m in depth, (Borselli and Cozzini, 1992), and for this reason, a scavenging option cannot be excluded. Within the same basin, a disassociated Eubalaena glacialis skull was found and initially identified as Physeter by Pilleri (1987). Recently, Bisconti (unpublished data) redescribed the specimen and found apomorphies of Eubalaena glacialis. The skull was 12 composed by three disassociated pieces dispersed on several-m2; among the cranial remains, a single triangular white shark's tooth was found. The evidence to hypothesize an interaction is too weak because the lack of a close proximity between the tooth and the cranial remains In his detailed work, Portis (1883) described the bite marks on the bones of some Mysticeti from Pliocene sediments of Piedmont (four records) and Liguria regions (one records). Among these records, only the "Balaenoptera" gastaldii holotype shows bite marks on its ulna that are homogeneous to the experimental paradigm provided by Cigala-Fulgosi (1990) and Deméré and Cerutti (1982) (Fig. 6). For this reason, it is hypothesizable that a white shark attacked or scavenged on the fin of the whale. Three Pliocene rorquals were found in Emilia Romagna that were associated to shark's teeth. Capellini (1865) stated that the rorqual remains found at S. Lorenzo in Collina (Bologna province) were strictly associated to some shark's teeth among which a single Carcharodon carcharias specimen. A balaenopterid skeleton has been recently found near Vignola (Modena province) in weak relation with a single large tooth belonging to a white shark. Unfortunately, the complete disassociation of the skeletons prevents an analysis of the kind of interactions between the sharks and the baleen whales. It can be stated just that some kind of interaction really happened. A large Piacenzian rorqual-like whale was found near Salsomaggiore Terme (Parma province; Bianucci, 1997a) bearing three white shark's teeth. The specimen was found in the same quarry of the Hemisyntrachelus cortesii discussed below. The shark teeth were closely associated to the skeleton; one of them was found under a lumbar vertebra and the others were in the anterior portion of the whale. The whale was deposited on its back and the abdomen was exposed to scavenging. Due to the enormous body size of the cetacean, it is hypothesized that the white shark scavenged on the floating carcass of this whale. 13 Discussion The analysis of trophic interactions between white sharks and cetaceans in the Recent central Mediterranean shows that cetaceans represent a significant component of the diet of large size (> 4 m) Carcharodon carcharias. The available data do not allow to assess which part of this interaction is due to scavenging and which to predation on living animals. However, the involved cetaceans are prevalently small and medium size delphinids which represent, still living, potential preys for these sharks (Casey and Pratt, 1985). The fossil record shows interactions between white sharks and whales also during the Pliocene. In particular, evidence of interaction is documented in three toothed whales and six baleen whales. Even if, on the basis of fossil data, it is not possible to distinguish scavenging from predation with an higher degree of confidence, considering that the estimated body size of the Mediterranean Pliocene Carcharodon carcharias was larger than the extant one (Cigala-Fulgosi, 1990), we can hypothesize that predation was possible on small and medium size delphinids and small Mysticeti as some cetotheriids and balaenids (Balaenula, Balaenotus). In light of the gathered evidences, the reason of death of the Hemisyntrachelus cortesii from Rio Stramonte and the "Balaenoptera" gastaldii from Cordandone could have been a white shark attack. Both specimens are 4.5-5 m long and show bite marks on the bones. It is hypothesizable that larger toothed and baleen whales could have been a trophic source for white sharks just when died. The finding of Carcharodon carcharias teeth in close proximity to 14 rorquals (Salsomaggiore Terme, about 8 m in length) and balaenids (Ponte a Elsa, about 10 m in length) is a clue of such a scavenging interaction. The comparison between Pliocene and Recent data shows that in the Recent central Mediterranean Sea, the interactions are principally directed to little-sized odontocetes and just rarely to mysticetes, while in the Pliocene, both toothed whales and baleen whales are presumed to have been equally represented in the Carcharodon carcharias diet (Fig. 7). It is remarkable that the diversity of living Mediterranean mysticetes is lower than the Pliocene one and that the living baleen whales from Mediterranean are represented just by larger species. In summary, a change occurred in the diet of white shark through time. This change could be due to both the general reduction of the living white shark body size and the diminished diversity of the cetacean assemblage. 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SHÄFER W, 1972. - Ecology and Palaeocology of marine environments. (G.Y. Craig, ed.), The University of Chicago Press. SLIPP J.W. & WILKE F., 1953. - the beaked whale Berardius on the Washington coast. J. Mammal., 34: 105-113. STORAI T., MOJETTA A., ZUFFA M. & GIULIANI S., in press. - Nuove segnalazioni di Carcharodon carcharias (L.) nel Mediterraneo Centrale. Atti Soc. Tosc. Sci. Nat. TERRASA S., 1988. - Tiburones en Mallorca. Brisas, 55: 6-12. TOMILIN A.G., 1967. - Cetacea. In: HEPTNER V.G. (ed.) - Mammals of the U.S.S.R. and adjacent countries. Israel Program for Scientific Translations, 9: 1-756, Jerusalem. 20 21 FIGURE CAPTIONS Fig. 1 - Carcass of Tursiops trucatus from Bovo Marina, showing a wide injury (diameter about 50 cm) clearly due to a large shark. Fig. 2 - Geographical distribution of the evidence of interactions between Carcarodon carcharias and cetaceans in the Recent central Mediterranean Sea. Circle: odontocetes; squares: mysticetes; questionmark: geographical placing not precisely known. For numbers and referred records see Tab. 1. Fig. 3 - Geographical distribution of the evidence of interactions between Carcarodon carcharias and cetaceans in the Pliocene central Mediterranean Sea. Circle: odontocetes; squares: mysticetes. For numbers and referred records see Tab. 2. Paleogeographical reconstruction after Azzaroli and Cita (1980). Fig. 4 - Outline skeletal plan of Hemisyntrachelus cortesii from Pliocene sediments of Salsomaggiore Terme (Parma, Emilia Romagna). Md, mandible; Rb, rib; Sk, skull; St, stern; Tt, tooth; Vc, cervical vertebra; Vd, dorsal vertebra; Vl, lumbar vertebra. The arrow indicates the two associated Carcharodon carcharias teeth. Fig. 5 - Balaena sp. from Pliocene sediments of Ponte a Elsa (Pisa, Tuscany). A: disarticulated right arm; B detail of A with associated Carcharodon carcharias tooth. The arrows indicate the position of the tooth. 22 Fig. 6 - Ulna of the Balaenoptera gastaldii holotype from Pliocene sediments of Cortandone (Asti, Piedmont) with bite marks of white shark (1-3). A: lateral view.; B: detail of A. Fig. 7 - Hypothetical trophic interaction between Carcharodon carcharias and cetaceans in the Pliocene (A) and Recent (B) central Mediterranean Sea. 1: delphinid (odontocete); 2: ziphiid (odontocete); small cethotherid/balaenopterid (mysticete); 4: small balaenid (mysticete); large balaenopterid (mysticete); large balaenid (mysticete); physeterid (odontocete). Solid arrows indicate sure interaction based on data discussed in this paper; broken arrows indicate possible interactions based on the presence of this cetacean group in the central Mediterranean Sea. 23 TABLE CAPTIONS Tab. 1 - Evidences of the interactions between Carcharodon carcharias and cetaceans in the central Mediterranean Sea; Recent data (1889-1997). Tab. 2 - Evidences of the interactions between Carcharodon carcharias and cetaceans in the central Mediterranean Sea; fossil data (Pliocene). 24 Date Place Cetaceans Species involved Cetacean length (cm) Cetacean weight (kg) Shark Length (cm) Shark Weight (kg) 1 Oct. 1889 Toulon (F) Pochoena pochoena ? 2 1896 Liguria (It) 400 - 3 26/1/1909 Augusta (It) Balenoptera musculus or B. physalus Indet. small delphinid - 4 13/11/1910 Marciana Marina I. d’Elba (It) 50 700-800 - 450 800 - (Condorelli and Perrando, 1909) (Damiani, 1911) 5 Aug. 1938 6 16/5/1956 Enfola I. d’Elba (It) Capo Bon (Tun) Jun. 1958 Estaque (F) Indet. large delphinid 8 Aug. 1960 Indet. small delphinid 9 22/10/1963 I. d’Elba, Rio Marina (It) Isola (Slo) 10 1964 Italian coasts 11 1967 12 22/07/1967 C. Ferrutx, Mallorca (E) I. del Giglio (It) Physeter macrocephalus Indet. delphinid 13 Jun. 1978 Lido di Venezia (It) Tursiops sp.? 14 Jun. 1979 Capo Bon (Tun) Indet. delphinid 15 24/04/1980 Favignana (It) Tursiops sp. 600 1.800 520 1.800 Wide Shark 500 1.000 600? 1.100 1.500 900 500 520 540 1.500 (Chiocca, 1990 Pers. Com.) (Postel, 1958) 7 15 200 - 16 17/04/1987 Filfla (Malta) Indet. delphinid 08/05/1987 Favignana (It) Indet. 18 31/07/1987 Ganzirri (It) Tursiops sp. 19 04/05/1988 Bovo Marina (It) Tursiops sp. 20 Jun. 1989 Capo Spartivento (It) Indet. delphinid 21 Jan. 1991 Sete (F) Indet. delphinid 22 04/06/1995 Follonica (It) Indet. delphinid 23 11/06/1997 Is. Salina (It) Stenella sp. 200 100 250 310 120 150 150 - 714? 535 2.000 550 450 400 - 17 Balenoptera physalus or B. acutorostrata Indet. small delphinid Delphinus sp. Indet. delphinid Indet. delphinid References (Moreau, 1892) (Parona, 1896) (Damonte, 1993) (Chiocca, 1994 Pers. Com.) (Lipey, 1994) (Fergusson, 1996) (Terrasa, 1988) (Anonimo, 1967) (Martini, 1989) (Fergusson, 1996) (Marcantonio & Cataldo, 1980 Pers. Com.) Abela, 1987 Pers. Com.) (Giudici & Fino, 1989) (CSC, 1988) (Vanadie, 1988 Pers. Com.) (CSC, 1991) (Fergusson, 1996) (Babboni, 1995 Pers. Com.) (CSC, 1999) 25 "Berardiopsis" "Berardiopsis" Delphinid Hemisyntrachelus cortesii Delphinid Hemisyntrachelus cortesii Balenopterid Balaenoptera cortesii Piedmont "Balaenoptera" gastaldii Balenopterid Balaenopterid Balenopterid Balenopterid (2) Calunga (Asti) (3) "Sabbie gialle" sediments (Asti province) (4) "Sabbie gialle" sediments (Asti province) (5) "Sabbie gialle" sediments (Asti province) Shar k teeth References Portis, 1883 ? ? ? no Portis, 1883 Portis, 1883 Portis, 1883 Portis, 1883 Cigla-Fulgosi, 1990 Cigla-Fulgosi, 1990 (6) Stramonte river (Piacenza) (7) Piacenza province (8) Salsomaggiore Terme (Parma) New data (9) Poggiarone (Siena) Portis, 1883 (10) S. Murino (Pisa) Portis, 1883 Borsellii and Cozzini, 1992 (11) Ponte a Elsa (Pisa) (12) Ricavo, near Caslelfranco (Florence) Eubalena sp. Emilia-R. Mysticeti Balaena sp. Tuscany Balaenotus Balaenotus Shark bites (1) Bagnasco (Asti) Piedmont Astadelphis gastaldii Astadelphis gastaldii Locality Emila-R. Odontoceti Cetacean records New data Portis, 1883 (13) Cortandone (Asti) (14) Calunga, near S. Damiano (Asti) (15) Asti province (16) "Sabbie gialle" sediments (Asti province) (17) S. Lorenzo in Collina (Bologna) (18) Salsomaggiore Terme (Parma) (19) Vignola (Modena) ? ? ? Portis, 1883 Portis, 1883 Portis, 1883 Capellini, 1865 New data New data 26 27 28 29 30 31