Current knowledge of orca ( Orcinus orca ) attacks on humpback whales ( Megaptera novaeangliae )

1. Annie Macie – Pacific Whale Foundation Figure 4 Killer whale juvenil (male) sighting in Machalilla National Park -Augoust 2005. Current knowledge of orca (Orcinus orca) attacks on humpback whales (Megaptera novaeangliae) in the Machalilla National Park, Ecuador. Castro, Cristina(1) & Scheidat, Meike(2) 1Pacific Whale Foundation, Casilla 17-21-872, Quito – Ecuador, pccastro@interactive.net.ec- www.pacificwhale.org - www.ecotec.edu.ec/ballenasjorobadas 2 Forschungs- und Technologiezentrum Westkueste, Universidad Kiel, Hafentoern, 25761 Buesum, Germany. scheidat@ftz-west.uni-kiel.de Humpback whales use the Machalilla National Park (MNP) in Ecuador as a breeding ground during the austral winter months (Figure 1 and 2). At the same time orca whales have been observed in this area. To determine the occurrence and behavior of orcas in the MNP, interviews were conducted with local fishermen, vessel captains and tourist guides (Figure 4). They provided information on 27 sightings of orca from 1991 to 1999. Sighting data were also collected using whale watching vessels from 1997 to 2004, resulting in an additional 23 orca sightings. In total, 50 orca sightings were collected, comprised of 141 animals. Pod sizes varied between one and eight animals, with a mean pod size of 2.82 (S.D.=1.05).  One pod containing calves sighted three times (Figure 3). Cristina Castro – Pacific Whale Foundation Figure 2 Off the Ecuadorian mainland humpback whales are primarily found in the marine area of the Machalilla National Park from June to September. Figure 1 Machalilla National Park – Ecuador – South America The behavior of the orca was described for 42 sightings. In six cases (14%), orcas were following a group of humpbacks or were seen in close proximity. In 9 cases (22%), orcas were observed feeding on fish or were associated with marine birds. For 19 orca sightings (45%), orcas were travelling or porpoising (Figure 5). In the remaining eight cases (19%), orcas were observed following or charging and attacking one or more humpbacks pods. The humpbacks displayed defensive behaviors, such as fluke slashes towards the orca. On September 01 2002, a pod of six orcas (5 adults and 1 calf) attacked a pod containing three humpbacks and a calf. After 20minutes, the calf disappeared and several minutes later pieces of flesh, oil and oil mixed with blood was floating on the water surface. The flesh was measured and had a blubber layer about 6cm thick (Figure 6). Attacks of orcas on humpbacks in their breeding grounds around the world have only been documented in only a few cases. Recent evidence indicates that calves and subadult humpback whales are more subjected to predation by orca (Naessig and Lanyon, 2004). These observations in Ecuadorian waters suggest orcas occur regularly in this area and that attacks on humpbacks might have a higher influence on humpback calf survival rates in this breeding region than previously known. Figure 6Oscar Pihuave (naturalistic guide of MNP) with a piece of flesh of humpback whale calf as a result of orca attack, September 1, 2002. Acknowledge We wanted to thank the operators whale-watching, capitains, sailors and the naturalistic guides of the MNP for their help us with the logistics and their thousand of smiles. To the administration of the Machalilla National Park. To the volunteers that unselfishly helped us to the research of whales. And especially to Gregory Kaufman - Pacific Whale Foundation that supports the research in Ecuador. To Bill Rossiter (Cetacean Society International) and Pacific Whale Foundation for my travel and logistic grant.