Mastozoología Neotropical ISSN: 0327-9383 [email protected] Sociedad Argentina para el Estudio de los Mamíferos Argentina
Ott, Paulo H.; Sucunza, Federico; Wickert, Janaína; Danilewicz, Daniel; Tavares, Maurício EVIDENCES OF ATTACK OF A KILLER WHALE ON A CALF SOUTHERN RIGHT WHALE IN SOUTHERN BRAZIL Mastozoología Neotropical, vol. 24, núm. 1, julio, 2017, pp. 235-240 Sociedad Argentina para el Estudio de los Mamíferos Tucumán, Argentina
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EVIDENCES OF ATTACK OF A KILLER WHALE ON A CALF SOUTHERN RIGHT WHALE IN SOUTHERN BRAZIL
Paulo H. Ott1, 2, Federico Sucunza2, 3, 4, Janaína Wickert2, 5, 6, Daniel Danilewicz2, 3, 7, and Maurício Tavares5, 6
1 Universidade Estadual do Rio Grande do Sul (UERGS), Unidade do Litoral Norte, Osório, RS, Brazil. [Correspondence: Paulo Henrique Ott
ABSTRACT. The killer whale (Orcinus orca) has a worldwide distribution and its feeding habits varies greatly among populations. In the southern Atlantic Ocean, knowledge about the distribution and diet of the species is still scarce. Herein we report the first evidence of a killer whale’s attack on a southern right whale (Eubalaena australis) in Brazilian waters and provide new records of killer whale sightings in coastal waters of the south- ernmost Brazilian region.
RESUMEN. Evidencias de un ataque de orca a una cría de ballena franca austral en el sur de Brasil. La orca (Orcinus orca) presenta una distribución global y una gran variación en los hábitos tróficos de sus poblaciones. En el Océano Atlántico Sur, el conocimiento sobre la distribución y la dieta de la especie es todavía escaso. En este trabajo, presentamos la primera evidencia de ataque de una orca a una ballena franca austral (Eubalaena australis) en aguas brasileñas y reportamos nuevos registros de avistamientos de orcas en aguas costeras de la región más austral de Brasil.
Key words: Eubalaena australis. Orcinus orca. Predatory-prey interaction. Stranding. Tooth marks.
Palabras clave: Eubalaena australis. Interacción predador-presa. Marcas de dientes. Orcinus orca. Varamiento.
The killer whale (Orcinus orca) is a large 2008; Ford, 2009; Weller, 2009). The diet of top predator that feeds on a variety of prey, killer whales varies greatly among populations, including over 30 cetacean species worldwide and prey specialization is usually one of the (e. g., Jefferson et al., 1991; Ford and Reeves, defining characteristics of the different ecotypes
Recibido 13 febrero 2017. Aceptado 31 marzo 2017. Editor asociado: R Bastida 236 Mastozoología Neotropical, 24(1):235-240, Mendoza, 2017 PH Ott et al. http://www.sarem.org.ar - http://www.sbmz.com.br
(e. g., Baird et al., 1992; Pitman and Ensor, Chuí River mouth (33o45’S, 53°22’W) were 2003; Weller, 2009; De Bruyn et al., 2013). In recorded during aerial surveys to estimate Antarctic and subantarctic waters, for instance, franciscana abundance in 2004 and 2014 (see five distinct ecotypes of killer whales (types A, Danilewicz et al., 2010). For every killer whale B-big, B-small, C and D) have been proposed sighting, information regarding date, location (Pitman and Ensor, 2003; Pitman et al., 2011). and number of individuals were recorded. Whereas some morphotypes prey mainly on On 24 July 2008, a newborn southern right marine mammals (types A and B-big), others whale was found dead (GEMARS 1304) at are suspected to have a diet based on penguins Balneário Quintão (30°19’S, 50°16’W), on the (type B-small) or fishes (type C and, probably, northern coast of Rio Grande do Sul (RS). type D) (De Bruyn et al., 2013). The female calf (Fig. 1), with 595 cm of total In South America, along the Patagonian coast length, still had vestiges of the umbilical cord. of Península Valdés, Argentina, killer whales The specimen presented several tooth marks prey mainly on South American sea lions on both dorsal and ventral surfaces of the (Otaria flavescens) and southern elephant seals right pectoral fin (Fig. 2A) and on the left (Mirounga leonina) (Thomas and Taber, 1984; fluke margin Fig.( 2B). Separation of the rake López and López, 1985; Hoelzel 1991; Bastida marks ranged from 3.0 to 3.5 cm, which is et al., 2007), although attacks to southern right characteristic of an adult killer whale (Schef- whales (Eubalaena australis) (Harris and García, fer, 1969). The marks were also very similar to 1986; Jefferson et al., 1991; Sironi et al., 2008), those reported in a southern right whale calf dusky dolphins (Lagenorhynchus obscurus) and found dead on Golfo San José, Argentina, fol- common dolphins (Delphinus delphis) have lowing an attack by adult killer whales (Harris been reported (Coscarella et al., 2015). and García, 1986). For the Brazilian waters, the feeding habi- Killer whales use a variety of hunting strate- tats and distribution of killer whales are still gies to debilitate and kill their preys. Attacking poorly known and only two cetaceans have killer whales are known, for instance, to grasp been reported as prey items of the species: large whales by the flukes and pectoral flippers the franciscana (Pontoporia blainvillei) (Ott in an attempt to slow or stop their movement, and Danilewicz, 1998; Santos and Netto, or even drown their prey by pulling them un- 2005) and the Burmeister’s porpoise (Phocoena derwater (Silber et al., 1990; Barrett-Lennard et spinipinnis) (Dalla Rosa, 1995). al., 2011). Therefore, considering that grasping Herein we report the first evidence of a killer whale attack on a southern right whale in Brazilian waters and present new records of O. orca in coastal waters of the southernmost region of Brazil. The original database include records of stranding southern right whales collected by a marine mammal research team (GEMARS – Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul) during regular beach surveys over 25 years (1991-2016) be- tween Torres (29°19’S, 49°42’W) and the Lagoa do Peixe National Park (31o21’S, 51o02’W), in southern Brazil. Opportunistic sighting of killer whales south of the Cape of Santa Marta Grande (28o36’S, 48°49’W) have been made onboard fishing vessels or documented in video Fig. 1. Southern right whale (Eubalaena australis) calf by recreational sailors from 2003 to early 2017. found dead (GEMARS 1304) on the northern coast of Rio Additional sightings of killer whales in coastal Grande do Sul, southern Brazil, with evidences of attack waters from Cape of Santa Marta Grande to by a killer whale (Orcinus orca). KILLER WHALE ATTACK ON A CALF SOUTHERN RIGHT WHALE 237
Fig. 2. Detail of the tooth rakes (white arrows) of a killer whale (Orcinus orca) on the right pectoral fin (A), and left fluke margin (B), of the southern right whale (Eubalaena australis) calf found dead (GEMARS 1304) on the northern coast of Rio Grande do Sul, southern Brazil. Ruler in (A) is 20 cm long. A few whale-lice (Cyamus sp.) are also visible in (B).
and dragging its prey is a common behavior of Therefore, although both killer whales and killer whales and previous attacks on southern southern right whales occur in southern Brazil, right whales are known (Harris and García, their spatial and temporal distributions seem to 1986; Jefferson et al., 1991; Sironi et al., 2008), be quite different, reducing the probability of it seems reasonable to assume that the marks encounters. In fact, we provide the first evidence found on the calf reported here were produced of predator-prey interaction between these spe- when the whale was still alive. cies in the region. From a total of 19 southern Southern right whales migrate to southern right whales found dead during 25 years in Brazil during winter and spring for breeding the study area, there is no other record of and calving (Groch et al., 2005; Danilewicz et this ecological interaction. Nevertheless, there al., 2016). The main aggregation areas roughly are several documented records of attacks or extend from 27oS to 30oS of latitude. Mother harassments of killer whales on southern right and calve pairs occur usually in waters close to whales in the calving and nursing grounds in the shore (< 10 m deep), with peak abundance Argentina and South Africa (e. g., Jefferson et between August and October (Groch et al., al., 1991; Sironi et al., 2008), although they do 2005; Danilewicz et al., 2016). Killer whales, on not seem to be a regular food source of killer the other hand, have been reported in southern whales (Bastida et al., 2007; Best et al., 2010; Brazil throughout the year, usually near the Coscarella et al., 2015). shelf break and the continental slope, in waters At the present, scarce information is available depth ranging from 110 to 3500 m (Castello and about the stock discreteness and foraging habits Pinedo, 1986; Pinedo et al., 2002; Dalla Rosa and of killer whales in Brazilian waters. Based on Secchi, 2007; Passadore et al., 2015; Di Tullio sighting data, including the long movements et al., 2016). Nevertheless, as reported here, in of a photo-identified adult male, it has been a few occasions killer whales have also been suggested that killer whales in southeastern sighted close to shore, mainly during the sum- Brazil present a similar behavior to the “tran- mer (December through February) (Table 1). sient” killer whales of the northeastern Pacific The finding of the remains of three franciscana (Siciliano et al., 1999; Santos and Silva, 2009). specimens, a dolphin species that inhabit waters These “transient” killer whales form small mainly up to 30 m (Danilewicz et al., 2009), groups that prey on marine mammals and in the stomach of a killer whale found dead in have an unpredictable occurrence in coastal northern coast of RS on December 19th, 1993 waters (Ford, 2009). The killer whale sight- (Ott and Danilewicz, 1998) is also noteworthy. ings in southern Brazil (Table 1) as well as 238 Mastozoología Neotropical, 24(1):235-240, Mendoza, 2017 PH Ott et al. http://www.sarem.org.ar - http://www.sbmz.com.br
Table 1 Sightings of killer whales (Orcinus orca) in inshore waters of southern Brazil, between the Cape of Santa Marta Grande (28o36’S) and Chuí river mouth (33o45’S). SC = Santa Catarina. RS = Rio Grande do Sul.
Distance Depth Date Location from shore Group Composition Source (m) (km)
Rio Grande, RS 2 adults, 1subadult, Castello and 28 Dec 1978 110/18 25/21 (32°16’S, 51°58’W) 1juvenile Pinedo (1986) a
Cape of Santa Marta, SC Pinedo et al. 21 Jul 1997 32.4 63 1 individual (28°41’S, 48°39’W) (2002)b
Balneário Pinhal, RS 30 Jan 2003 1 < 10 1 adult male This study (30°14’S, 50°13’W)
Passo de Torres, SC 16 Jan 2004 2 10 Mother-calf pair This study (29°19’S, 49°41’W)
Rio Grande, RS 24 Feb 2004 24 16 2 individuals This study (32°52’S, 52°14’W)
Santa Vitória do Palmar, RS 23 Jan 2014 44 30 1 individual This study (33°25’S, 52°17’W)
Balneário Rincão, SC 6-8 individuals, includ- 26 Jan 2017 3.8 30 This study (28°50’S, 49°10’W) ing one adult male a Castello and Pinedo (1986) cited this sighting as 110 km from the coast and 25 m depth. However, based on the coor- dinates presented, the corresponding locality is about 18 km from the coast and 21 m depth. b Detailed location provided by A. Barreto (pers. comm.).
the prey-interaction described here seem also In conclusion, although killer whales seem to fit in this foraging behavior. Nevertheless, to have primarily an oceanic distribution in considering the scarcity of information on southern Brazil and feed mainly on large fishes killer whales from Brazilian waters and the near the continental slope (Secchi and Vaske Jr., great behavioral flexibility of the species in a 1998; Dalla Rosa and Secchi, 2007; Passadore global scale (De Bruyn et al., 2013), it seems et al., 2015), the species, or at least some of premature to classify the killer whales of this the existent stocks, can also eventually search region in any specific ecotype. and prey upon coastal whales and dolphins Despite this uncertainty, the migratory in the region. movements of three adult female killer whales Acknowledgments. The authors would like to thank all identified as the type B and tagged in Antarctic colleagues and volunteers that collaborated with GEMARS were recorded in offshore waters of RS (around over the years, in special Sandra Krieger, Jonathas Bar- 30oS) (Durban and Pitman, 2011). In addi- reto and Roberto Rosa for help to collect the data on tion, a recent molecular study assigned one the southern right whale calf. We are also grateful to the UERGS, CECLIMAR/IB/UFRGS and MORG-FURG for of the killer whales stranded on the southern the logistical support. André Barreto and Marta Cremer o coast of RS (around 32 S) to type C with high allowed us to use unpublished data. Alexandre Azevedo, probability (Morin et al., 2015). Therefore, it Artur Andriolo, Emanuel Ferreira and Pablo Denuncio seems that more than one stock of killer whales participated of the franciscana aerial surveys. We are also could inhabit the waters of southern Brazil, as in debt with Julian Lemos and Vanessa Andrade for the information and video on the sighting of killer whales at suspected by other authors (Dalla Rosa, 1995; Balneário Rincão. Finally, we would like to thank Ricardo Passadore et al., 2015). Bastida and an anonymous reviewer, which contributed KILLER WHALE ATTACK ON A CALF SOUTHERN RIGHT WHALE 239
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