scholarly journals Male killer whales unexpectedly hunt more than females

2019 ◽  
Vol 222 (3) ◽  
pp. jeb197798
Author(s):  
Kathryn Knight
Keyword(s):  
Killer Whales ◽  
Male Killer

Killer whales (Orcinus orca) attack and kill a Bryde's whale (Balaenoptera edeni)

1990 ◽  
Vol 68 (7) ◽  
pp. 1603-1606 ◽  
Author(s):  
Gregory K. Silber ◽  
Michael W. Newcomer ◽  
Héctor Pérez-Cortés M.
Keyword(s):  
Adult Male ◽  
Gulf Of California ◽  
Orcinus Orca ◽  
Adult Males ◽  
Killer Whales ◽  
Lower Jaw ◽  
Large Wound ◽  
The Right ◽  
Male Killer

On 3 May 1988, we observed a group of killer whales that pursued, killed, and partially consumed a Bryde's whale in the northern Gulf of California, Mexico (31°01′N, 114°15′W). The attack was observed from 06:54 to 08:53 while circling in a single-engine aircraft at an altitude of 160 m. The group comprised about 15 killer whales, including two adult males and at least two calves. Females and (or) subadult males pressed the attack most intently. The killer whales tore skin and blubber from the right flank of the Bryde's whale, and on 11 occasions the killer whales swam onto the head or back of the Bryde's whale, which hindered its breathing. The respiration intervals of the Bryde's whale were short and irregular, and blow rates differed significantly from those of undisturbed Bryde's whales. Fatiguing the whale may have facilitated an easier kill by asphyxiation. After the death of the Bryde's whale, the two adult male killer whales surfaced slowly about 200–300 m away from the remainder of the group, which presumably fed on the submerged Bryde's whale carcass. Two days later, the drifting Bryde's whale carcass was located. A large wound was visible on the abdomen, and sections of the lower jaw had been removed. Like those of canids and some felids that hunt cooperatively when preying on ungulates, attacks by Orcinus orca exhibit coordination of activities and efficiency in dispatching prey.

scholarly journals Circulating inhibin and testosterone during sexual maturation and reproductive seasonality of captive male killer whales (Orcinus orca)

2020 ◽  
Vol 19 (2) ◽  
pp. 209-222
Author(s):  
Hiroshi Katsumata ◽  
◽  
Etsuko Katsumata ◽  
Sukanya Jaroenporn ◽  
Yoko Ueda ◽  
...  
Keyword(s):  
Sexual Maturation ◽  
Killer Whale ◽  
Mature Stage ◽  
Killer Whales ◽  
Pubertal Stage ◽  
Seasonal Breeder ◽  
Northern Atlantic ◽  
Autumn And Winter ◽  
First Time ◽  
Male Killer

The present study aimed to investigate the reproductive biology of male killer whales. Changes in the concentrations of two circulating testicular hormones, inhibin and testosterone, were monitored during sexual maturation of two male Type 1 Eastern Northern Atlantic killer whales over a period of 20 years. The two killer whales grew rapidly at the pubertal stage and reached a plateau at the age of 23 and 20 years, respectively, after which growth slowed down. In the younger male, circulating inhibin was higher in the juvenile than in the pubertal and mature stages; whereas circulating testosterone exhibited the opposite trend. The pubertal period was estimated to last approximately 5 years, from 12 to 17 years of age. In the elder male, circulating testosterone was high from the onset of this study (12 years of age), when the animal also sired successfully for the first time. This finding shows that the male killer whale is possible to sire even if it is not socially matured, if there is opportunity for copulation. During the mature stage, both animals exhibited significantly higher circulating testosterone concentrations in spring compared to autumn and winter; whereas no seasonal change was observed for circulating inhibin. These results clearly demonstrate that the male killer whale is a seasonal breeder, even though it is fertile throughout the year. This is the first study to elucidate the inhibin concentration and secretory source in the male killer whale.

Personality in captive killer whales (Orcinus orca): A rating approach based on the five-factor model.

2019 ◽  
Vol 133 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Yulán Úbeda ◽  
Sara Ortín ◽  
Judy St. Leger ◽  
Miquel Llorente ◽  
Javier Almunia
Keyword(s):  
Factor Model ◽  
Five Factor Model ◽  
Orcinus Orca ◽  
Killer Whales

First record of Norwegian killer whales attacking and feeding on a harbour porpoise

2015 ◽  
Vol 8 ◽  
Author(s):  
A. Mel Cosentino
Keyword(s):  
North Atlantic ◽  
Marine Mammals ◽  
First Record ◽  
Harbour Porpoise ◽  
Sperm Whales ◽  
Killer Whales ◽  
Strait Of Gibraltar ◽  
Cetacean Species ◽  
The North ◽  
Northern Bottlenose Whales

Orcinus orcais a cosmopolitan species and the most widely distributed marine mammal. Its diet includes over 140 species of fish, cephalopods, sea birds and marine mammals. However, many populations are specialised on certain specific prey items. Three genetically distinct populations have been described in the North Atlantic. Population A (that includes the Icelandic and Norwegian sub-populations) is believed to be piscivorous, as is population C, which includes fish-eating killer whales from the Strait of Gibraltar. In contrast, population B feeds on both fish and marine mammals. Norwegian killer whales follow the Norwegian spring spawning herring stock. The only description in the literature of Norwegian killer whales feeding on another cetacean species is a predation event on northern bottlenose whales in 1968. Daily land-based surveys targeting sperm whales were conducted from the Andenes lighthouse using BigEyes®binoculars (25×, 80 mm). The location of animals at sea was approximated through the use of an internal reticule system and a graduated wheel. On 24 June 2012 at 3:12 am, an opportunistic sighting of 11 killer whales was made off Andenes harbour. The whales hunted and fed on a harbour porpoise. Despite these species having overlapping distributions in Norwegian waters, this is the first predatory event reported in the literature.

scholarly journals Survival of the fattest: linking body condition to prey availability and survivorship of killer whales

Ecosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Joshua D. Stewart ◽  
John W. Durban ◽  
Holly Fearnbach ◽  
Lance G. Barrett‐Lennard ◽  
Paige K. Casler ◽  
...  
Keyword(s):  
Body Condition ◽  
Prey Availability ◽  
Killer Whales

scholarly journals Mixture models as a method for comparative sociality: social networks and demographic change in resident killer whales

2021 ◽  
Vol 75 (4) ◽  
Author(s):  
Samuel Ellis ◽  
Daniel W. Franks ◽  
Michael N. Weiss ◽  
Michael A. Cant ◽  
Paolo Domenici ◽  
...  
Keyword(s):  
Mixture Models ◽  
Demographic Change ◽  
Social Preferences ◽  
Social Bonds ◽  
Killer Whales ◽  
Animal Populations ◽  
Binomial Mixture ◽  
Opposite Sex ◽  
Social Associations ◽  
Social Association

Abstract In studies of social behaviour, social bonds are usually inferred from rates of interaction or association. This approach has revealed many important insights into the proximate formation and ultimate function of animal social structures. However, it remains challenging to compare social structure between systems or time-points because extrinsic factors, such as sampling methodology, can also influence the observed rate of association. As a consequence of these methodological challenges, it is difficult to analyse how patterns of social association change with demographic processes, such as the death of key social partners. Here we develop and illustrate the use of binomial mixture models to quantitatively compare patterns of social association between networks. We then use this method to investigate how patterns of social preferences in killer whales respond to demographic change. Resident killer whales are bisexually philopatric, and both sexes stay in close association with their mother in adulthood. We show that mothers and daughters show reduced social association after the birth of the daughter’s first offspring, but not after the birth of an offspring to the mother. We also show that whales whose mother is dead associate more with their opposite sex siblings and with their grandmother than whales whose mother is alive. Our work demonstrates the utility of using mixture models to compare social preferences between networks and between species. We also highlight other potential uses of this method such as to identify strong social bonds in animal populations. Significance statement Comparing patters of social associations between systems, or between the same systems at different times, is challenging due to the confounding effects of sampling and methodological differences. Here we present a method to allow social associations to be robustly classified and then compared between networks using binomial mixture models. We illustrate this method by showing how killer whales change their patterns of social association in response to the birth of calves and the death of their mother. We show that after the birth of her calf, females associate less with their mother. We also show that whales’ whose mother is dead associate more with their opposite sex siblings and grandmothers than whales’ whose mother is alive. This clearly demonstrates how this method can be used to examine fine scale temporal processes in animal social systems.

scholarly journals Family feud: permanent group splitting in a highly philopatric mammal, the killer whale (Orcinus orca)

2021 ◽  
Vol 75 (3) ◽  
Author(s):  
Eva H. Stredulinsky ◽  
Chris T. Darimont ◽  
Lance Barrett-Lennard ◽  
Graeme M. Ellis ◽  
John K. B. Ford
Keyword(s):  
Killer Whale ◽  
Group Structure ◽  
Group Living ◽  
Orcinus Orca ◽  
Learning Approaches ◽  
Killer Whales ◽  
Internal Factors ◽  
Individual Fitness ◽  
Leadership Experience

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.

RESIGHTINGS AND BEHAVIOR OF FALSE KILLER WHALES ( PSEUDORCA CRASSZDENS ) IN COSTA RICA

1997 ◽  
Vol 13 (2) ◽  
pp. 307-314 ◽  
Author(s):  
ALEJANDRO ACEVEDO‐GUTIÉRREZ ◽  
BERNARD BRENNAN ◽  
PATRICIA RODRIGUEZ ◽  
MOLLY THOMAS
Keyword(s):  
Costa Rica ◽  
Killer Whales ◽  
And Behavior
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