Adaptation

Physeter macrocephalus is capable of diving for food at depths greater than 3,000 meters (Evans, 1977). For a mammal to be able to function at depths that great, and pressures that high they need to have efficient transport systems. The sperm whale, with an extremely large body (females can weight up 15 tons while male sperm whales can weigh up to 45 tons) are capable of deep diving for long durations due to the ability of being able to store oxygen in the skeletal muscles (Noren & Williams, 2000). Research by Noren and Williams (2000) found that myoglobin acts as the primary oxygen carrier in the skeletal muscles of sperm whales. When the perfusion to a muscle region is decreased, oxygen depleating in that specific area will then be restarted by the release of myoglobin-bound oxygen into the tissue. This adaptation has allowed the sperm whale to survive in many different ecological environments, dive to considerable depths to find food and be able to withstand the changes between these environments.

    Oelschlāger and Kemp (1998) found that in most cetaceans, the optic and visual systems are reported to be fairly well developed. According to Oelschlāger and Kemp (1998), for the large body mass of the sperm whale it exhibits relatively small eyes and contains less than 200,000 axons, nearly a million less than humans. It is possible that sperm whales do not need such high resolution because of their narrow-banded high frequency biosonar signals. With their unique adaptation of being able to send out these sonar clicks the sperm whale is probably able to combine the acoustic input together with visual information into two- or even three-dimensional images to find their prey and scan their surroundings. With that being said, Oelschlāger and Kemp (1998) proposed that the auditory system has stamped the morphology, size, and connectivity of the whole odontocetes brain; this is due to the necessity of processing vast amounts of acoustic information and the high propagation velocity of sound in water. Studies by Carder, Bedholm and Ridgway (2012) show that the sperm whales biosonar signals carry all their energy at frequencies above the upper hearing limit of the killer whale Orcinus orca. This may also have been an evolutionary shaping factor of predator avoidance of the sonar signals from these non-whistling odontocetes.

  Being able to adapt to their environment and have these morphological changes, natural selection has possibly allowed them to survive and avoid predation. Oelschlāger and Kemp (1998) state that in addition to avoiding predation, communication between individuals by means of acoustic signals is especially important while hunting and when vision is reduced. While being able to communicate effectively, and navigate though dark waters by using sonar clicks at such high frequencies, the sperm whale also has a very unique corticospinal tract. According to Oelschlāger and Kemp (1998), sperm whales corticospinal tract is developed only weakly and there are no macroscopic pyramids that are seen in terrestrial mammals. They stated that the moderate development of the corticospinal tract in cetaceans can be attributed to the loss of hind legs and to the modification of the forelegs into flippers (Oelschlāger & Kemp, 1998). In the cerebellum of the sperm whale the functional implications of the very large paraflocculus in cetaceans are still very difficult to understand. Oelschlāger and Kemp suggest that its enormous size is related to their locomotion of the body stem and/or the dominant position of the auditory system within the brain. Sperm whales are able to swim through the water by using undulating movements, which are movements of their flukes (tails) up and down, with the help of their pectoral fins to maneuver through the water (Oelschlāger & Kemp, 1998).

We hope you enjoyed learning about the adaptations of Physeter macrocephalus and how it has evolved. You may follow this link to the home page or continue on and learn about the diet/nutrition of a sperm whale.