Architecture of the sperm whale forehead facilitates ramming combat

Panagiotopoulou,Olga, Spyridis, Panagiotis, Mehari Abraha, Hyab, Carrier, David R. and Pataky, Todd C. (2016) Architecture of the sperm whale forehead facilitates ramming combat. PeerJ, 4 . doi:10.7717/peerj.1895


 
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Author Panagiotopoulou,Olga
Spyridis, Panagiotis
Mehari Abraha, Hyab
Carrier, David R.
Pataky, Todd C.
Title Architecture of the sperm whale forehead facilitates ramming combat
Journal name PeerJ   Check publisher's open access policy
ISSN 2167-8359
Publication date 2016-04-05
Year available 2016
Sub-type Article (original research)
DOI 10.7717/peerj.1895
Open Access Status DOI
Volume 4
Total pages 11
Place of publication London, United Kingdom
Publisher PeerJ
Collection year 2017
Language eng
Formatted abstract
Herman Melville’s novel Moby Dick was inspired by historical instances in which large sperm whales (Physeter macrocephalus L.) sank 19th century whaling ships by ramming them with their foreheads. The immense forehead of sperm whales is possibly the largest, and one of the strangest, anatomical structures in the animal kingdom. It contains two large oil-filled compartments, known as the “spermaceti organ” and “junk,” that constitute up to one-quarter of body mass and extend one-third of the total length of the whale. Recognized as playing an important role in echolocation, previous studies have also attributed the complex structural configuration of the spermaceti organ and junk to acoustic sexual selection, acoustic prey debilitation, buoyancy control, and aggressive ramming. Of these additional suggested functions, ramming remains the most controversial, and the potential mechanical roles of the structural components of the spermaceti organ and junk in ramming remain untested. Here we explore the aggressive ramming hypothesis using a novel combination of structural engineering principles and probabilistic simulation to determine if the unique structure of the junk significantly reduces stress in the skull during quasi-static impact. Our analyses indicate that the connective tissue partitions in the junk reduce von Mises stresses across the skull and that the load-redistribution functionality of the former is insensitive to moderate variation in tissue material parameters, the thickness of the partitions, and variations in the location and angle of the applied load. Absence of the connective tissue partitions increases skull stresses, particularly in the rostral aspect of the upper jaw, further hinting of the important role the architecture of the junk may play in ramming events. Our study also found that impact loads on the spermaceti organ generate lower skull stresses than an impact on the junk. Nevertheless, whilst an impact on the spermaceti organ would reduce skull stresses, it would also cause high compressive stresses on the anterior aspect of the organ and the connective tissue case, possibly making these structures more prone to failure. This outcome, coupled with the facts that the spermaceti organ houses sensitive and essential sonar producing structures and the rostral portion of junk, rather than the spermaceti organ, is frequently a site of significant scarring in mature males suggest that whales avoid impact with the spermaceti organ. Although the unique structure of the junk certainly serves multiple functions, our results are consistent with the hypothesis that the structure also evolved to function as a massive battering ram during male-male competition.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Biomedical Sciences Publications
 
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Created: Thu, 07 Apr 2016, 10:50:01 EST by Olga Panagiotopoulou on behalf of School of Biomedical Sciences