Attack on gray whales (Eschrichtius robustus) in Monterey Bay, California, by killer whales (Orcinus orca) previously identified in Glacier Bay, Alaska

1994 ◽  
Vol 72 (8) ◽  
pp. 1528-1530 ◽  
Author(s):  
P. Dawn Goley ◽  
Janice M. Straley

A group of at least 17 killer whales (Orcinus orca) were observed attacking a gray whale (Eschrichtius robustus) mother and calf on 2 May 1992 in Monterey Bay, California, U.S.A. (36°47.90′N, 122°00.17′W). Small groups of killer whales took turns harassing the gray whales and prevented them from leaving the area. Three of the killer whales participating in this attack previously had been photographed on 6 August 1989 in Glacier Bay, Alaska, U.S.A. (58°41′N, 136°04′W). This linear distance nearly doubles the maximum range of movement previously reported for killer whales.

2019 ◽  
Vol 133 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Yulán Úbeda ◽  
Sara Ortín ◽  
Judy St. Leger ◽  
Miquel Llorente ◽  
Javier Almunia

2021 ◽  
Vol 75 (3) ◽  
Author(s):  
Eva H. Stredulinsky ◽  
Chris T. Darimont ◽  
Lance Barrett-Lennard ◽  
Graeme M. Ellis ◽  
John K. B. Ford

Abstract For animals that tend to remain with their natal group rather than individually disperse, group sizes may become too large to benefit individual fitness. In such cases, group splitting (or fission) allows philopatric animals to form more optimal group sizes without sacrificing all familiar social relationships. Although permanent group splitting is observed in many mammals, it occurs relatively infrequently. Here, we use combined generalized modeling and machine learning approaches to provide a comprehensive examination of group splitting in a population of killer whales (Orcinus orca) that occurred over three decades. Fission occurred both along and across maternal lines, where animals dispersed in parallel with their closest maternal kin. Group splitting was more common: (1) in larger natal groups, (2) when the common maternal ancestor was no longer alive, and (3) among groups with greater substructuring. The death of a matriarch did not appear to immediately trigger splitting. Our data suggest intragroup competition for food, leadership experience and kinship are important factors that influence group splitting in this population. Our approach provides a foundation for future studies to examine the dynamics and consequences of matrilineal fission in killer whales and other taxa. Significance statement Group living among mammals often involves long-term social affiliation, strengthened by kinship and cooperative behaviours. As such, changes in group membership may have significant consequences for individuals’ fitness and a population’s genetic structure. Permanent group splitting is a complex and relatively rare phenomenon that has yet to be examined in detail in killer whales. In the context of a growing population, in which offspring of both sexes remain with their mothers for life, we provide the first in-depth examination of group splitting in killer whales, where splitting occurs both along and across maternal lines. We also undertake the first comprehensive assessment of how killer whale intragroup cohesion is influenced by both external and internal factors, including group structure, population and group demography, and resource abundance.


2019 ◽  
Vol 146 (5) ◽  
pp. 3475-3486 ◽  
Author(s):  
Marla M. Holt ◽  
M. Bradley Hanson ◽  
Candice K. Emmons ◽  
David K. Haas ◽  
Deborah A. Giles ◽  
...  

2004 ◽  
Vol 117 (3) ◽  
pp. 253-262 ◽  
Author(s):  
Joseph K. Gaydos ◽  
Kenneth C. Balcomb ◽  
Richard W. Osborne ◽  
Leslie Dierauf

2021 ◽  
Vol 150 (4) ◽  
pp. A251-A251
Author(s):  
Rianna Burnham ◽  
Svein Vagle ◽  
Pramod Thupaki ◽  
Caitlin O'Neill

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