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DOI 10.3354/esr00924
Geographic and temporal patterns of non-lethal attacks on humpback whales by killer whales in the eastern South Pacific and the Antarctic Peninsula
2018
Capella, Juan J.
;
Felix, Fernando
;
Florez-Gonzalez, Lilian
;
Gibbons Escobar, Jorge Eduardo
;
Haase, Ben
;
Guzman, Hector M.
The role and impact of killer whales Orcinus orca as predators of baleen whales has been emphasized by studies of humpback whales Megaptera novaeangliae. In this study, rake marks on the fluke were used as a proxy for predatory attacks in a sample of 2909 adult humpback whales and 133 calves from 5 breeding and 2 feeding locations in the eastern South Pacific and the Antarctic Peninsula. The goal of this study was to evaluate how often, at what age, where, and when humpback whales were more susceptible to attacks. Overall, 11.5 % of adults and 19.5 % of calves had rake marks on their flukes. Significant differences were found in the prevalence of scars in calves when comparing breeding (9 %) vs. feeding areas (34 %) (chi(2) = 10.23, p < 0.01). Multi-year sighting analysis of scar acquisition in 120 adults (82 % site fidelity) and 37 calves in the Magellan Strait showed no new marks after the initial sighting for the subsequent 15 yr. This finding indicates that rake marks were most probably acquired when whales were calves, which supports the belief that scar acquisition is a once in a lifetime event. The odds of having rake marks increased with time but with a significantly higher rate in calves (chi(2) = 5.04, p < 0.05), which suggests an increase in predation pressure over time. Our results support the earlier hypothesis that killer whale attacks occur mostly on calves, near breeding sites, and during the first migration to feeding areas.
Some of the metrics are blocked by your
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DOI 10.3354/esr00924
Geographic and temporal patterns of non-lethal attacks on humpback whales by killer whales in the eastern South Pacific and the Antarctic Peninsula
2018
Capella, Juan J.
;
Felix, Fernando
;
Florez-Gonzalez, Lilian
;
Gibbons Escobar, Jorge Eduardo
;
Haase, Ben
;
Guzman, Hector M.
The role and impact of killer whales Orcinus orca as predators of baleen whales has been emphasized by studies of humpback whales Megaptera novaeangliae. In this study, rake marks on the fluke were used as a proxy for predatory attacks in a sample of 2909 adult humpback whales and 133 calves from 5 breeding and 2 feeding locations in the eastern South Pacific and the Antarctic Peninsula. The goal of this study was to evaluate how often, at what age, where, and when humpback whales were more susceptible to attacks. Overall, 11.5 % of adults and 19.5 % of calves had rake marks on their flukes. Significant differences were found in the prevalence of scars in calves when comparing breeding (9 %) vs. feeding areas (34 %) (chi(2) = 10.23, p < 0.01). Multi-year sighting analysis of scar acquisition in 120 adults (82 % site fidelity) and 37 calves in the Magellan Strait showed no new marks after the initial sighting for the subsequent 15 yr. This finding indicates that rake marks were most probably acquired when whales were calves, which supports the belief that scar acquisition is a once in a lifetime event. The odds of having rake marks increased with time but with a significantly higher rate in calves (chi(2) = 5.04, p < 0.05), which suggests an increase in predation pressure over time. Our results support the earlier hypothesis that killer whale attacks occur mostly on calves, near breeding sites, and during the first migration to feeding areas.
Scopus© Citations 11 4
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DOI 10.1016/j.marpol.2020.103990
Humpback whale movements in a narrow and heavily-used shipping passage, Chile
2020-8
Guzman, Hector M.
;
Capella, Juan J.
;
Valladares, Carlos
;
Gibbons Escobar, Jorge Eduardo
;
Condit, Richard
The Magellan Strait is a narrow passage connecting the Pacific and Atlantic oceans in South America. An average of 2023 ships per year transit this corridor with 80% representing the international fleet. The southwestern part of the Strait in Chile is an important summer feeding area for humpback whales. Considering the risk to whales of feeding among dense ship traffic, the movements of 25 satellite-tagged whales relative to vessel density were analyzed, to provide policy recommendations for protecting the species from vessel collisions. A total of 3694 filtered whale positions from 21 individuals were obtained along the southwest passage. The daily range covered by individual whales was 8.8 km, and <25 km on 90% of all days. Ship density in the same square kilometers where whales were encountered was 0.27 per week, slightly more often than once per month, however this encounter rate varied by 100-fold between individuals, depending on how often animals were in the central shipping lane. One of the tagged whales stopped transmitting and washed up dead suggesting a ship strike. In the last decade, four other humpback whales and three sei whales were killed by probable ship strikes, all near Isla Carlos III, the core of the humpback feeding area. A 10-knot speed restriction and onboard observers are recommended during the five months of maximum whale abundance, applying to all merchant vessels traveling through the Strait, between Cabo Holland and Isla Bonete north of Carlos III Island, for a distance of 28 nautical miles (52 km).
Scopus© Citations 8 1

Gibbons Escobar, Jorge Eduardo

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