DOI: 10.5061/dryad.81rp6
title: Data from: Architecture of the sperm whale forehead facilitates ramming combat

description: 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 the load-redistribution functionality
 of the former is insensitive to 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.
description: Probabilistic Simulation
 for FEAPython script used for
 the probabilistic simulation of all finite element
 modelsMODEL
 AThis
 folder contains all finite element models and the simulation results for
 Model A and its subsequent modifications in terms of impact force angle
 and location; and the thickness of the connective tissue partitions. All
 sub-folders contain a "read me.txt" file that describes all
 metadata.MODEL_A.zipMODEL BThis folder contains all finite element models and the simulation results for Model B and its subsequent modifications in terms of impact force angle and location.All sub-folders contain a "read me.txt" file that describes all metadata.MODEL_B.zipMODEL CThis folder contains all finite element models and the simulation results for Model C and its subsequent modifications in terms of impact force angle and location.All sub-folders contain a "read me.txt" file that describes all metadata.MODEL_C.zip