Moby Dick - Miniaturized

The White Whale swam before him as the monomaniac incarnation of all those malicious agencies which some deep men feel eating in them, till they are left living on with half a heart and half a lung. That intangible malignity which has been from the beginning; to whose dominion even the modern Christians ascribe one-half of the worlds…Ahab did not fall down and worship it like them; but deliriously transferring its idea to the abhorred white whale, he pitted himself, all mutilated, against it. All that most maddens and torments; all that stirs up the lees of things; all truth with malice in it; all that cracks the sinews and cakes the brain; all the subtle demonisms of life and thought; all evil…were visibly personified, and made practically assailable in Moby Dick. He piled upon the whale’s white hump the sum of all the general rage and hate felt by his whole race from Adam down; and then, as if his chest had been a mortar, he burst his hot heart’s shell upon it.
~ Ishmael explains Ahab’s hatred of Moby Dick (Herman Melville, Moby Dick)

Most of us are familiar with sperm whales, if only through school discussions or movie remakes of the classic tale of Moby Dick. They are massive, toothy whales that live in the depths of the ocean and prey on the equally formidable giant squid, surfacing only to cause misfortune and mayhem (or so Capt. Ahab would have us believe). But did you know they come in miniature? Dwarf and pygmy sperm whales are the chihuahuas of the whale world, smaller even than some dolphin species. These two whales are the only living species of their family, Kogiidae, and they are quite similar, even classified as a single species until 1966. They differ slightly in physical size, morphology, and other minor features, and it’s very difficult to distinguish between the two in the field. The geographic distribution and range for these species overlap in several areas; however, the dwarf sperm whale is a bit more coastal than the pygmy, so that’s our primary focus.

Taxonomically, dwarf sperm whales are treated as a single species, though genetic evidence suggests that there may be two separate species – one in the Atlantic and one in the Indo-Pacific. If confirmed, the taxon will change. Weighing in at up to 600 pounds, dwarf sperms are compact and streamlined, reaching lengths up to nine feet. The head is square, with a pointed snout and a small, under-slung jaw. Their scientific name, Kogia sima, comes from the Latin sinus, meaning “flat-nosed.” Unlike the larger sperm whales, they have very few teeth (only about thirty in total, and most of those on the bottom), though the ones they have are sharply pointed and curved. Because of these fang-like teeth, they’ve earned the nickname “rat porpoise” in the Lower Antilles. The tail fluke is sharply pointed, as is the dorsal fin, located midway down the back. Behind the eye is a pale false gill plate, resembling a fish’s gill cover. In fact, if it weren’t for their blowhole and languorous attitude, dwarf sperm whales might be mistaken for sharks.

Like their larger cousins, dwarf sperms have a spermaceti organ. Located inside the head, this organ was historically thought by whalers to produce sperm (hence the name), but it actually contains high-quality oil. Their single blowhole is located left of the melon on their somewhat asymmetrical skull. (The melon is a mass of fatty tissue found in the forehead of all toothed whales. It focuses and modulates vocalizations and acts as a sound lens.) Their eyes are dark and protruding with a light circular mark above them. The skin is brownish- to bluish-gray on the top and paler with whitish to pinkish color on the bottom. It is also wrinkly up close, especially on the throat below the jaw where there may be several longitudinal creases. The flippers are broad with round edges and located forward on the body. When observed at the surface, they have a low, flat profile due to the level position of the head and back. They can be found in warm tropical, subtropical, and temperate seas worldwide, most commonly along the continental shelf edge and slope. In the northern Gulf of Mexico, there is an estimated combined total of about 742 dwarf and pygmy sperm whales.

Dwarf sperm whales enjoy a similar diet to full-size sperm whales, but their particular prey are on a rather smaller scale than giant squid. They eat mostly squid and octopus, but will also take shrimp, crabs, and fish. It is thought that they can dive to at least 1,000 feet to hunt and probably use echolocation to search for likely meals. No solid information exists regarding possible predators, but it’s not unlikely that dwarf sperms are hunted by killer whales or sharks inhabiting the same environment, as both of these animals are known to prey on other whale species. Calves, unsurprisingly, have more predators than adults.

Calving season likely occurs during the summer months. Dwarf sperm whales have one calf a year. Of course, one’s enough when it can weigh-in at birth at 110 pounds and four feet long. They become sexually mature between two and five years old, or when they reach about seven feet long. Males mature a little faster (and a bit shorter) than females. The estimated lifespan for this species is 22 years.

An unusual characteristic that distinguishes dwarf and pygmy sperm whales from other cetaceans (whales, dolphins, and porpoises) is the "squid tactic." In the lower portion of their intestine, there is a sac filled with viscous, dark reddish-brown liquid. Dwarf and pygmies are capable of ejecting over three gallons of this “ink,” creating a dense cloud that (hopefully) allows the whale to escape from its pursuers.

When it comes to social activities, dwarf sperm whales are fairly inactive, rarely performing acrobatic behaviors like breaching or tail slapping. They are usually seen traveling in small pods of ten or so individuals, though it’s not rare for one to travel alone. The pods vary based on age and sex, some consisting of females with calves, others of immature whales, and a third mix made up of adults of both sexes without calves. Their vocal communications include high-pitch clicks and whistles, which are used both for echolocation and social interaction. Dwarf sperms are slow, deliberate swimmers with a habit of floating motionless at the surface (a behavior termed ‘logging’). To dive, they slowly roll or sink, often disappearing from view without displaying their flukes. This species is very difficult to spot at sea due to these habits and their low profile. They’re usually only spotted in ideal conditions (calm seas, low wind speeds, little or no swells, etc.). While they don’t approach boats, they sometimes allow boats to approach them while basking at the surface.

Dwarf sperm whales are protected under the Marine Mammal Protection Act of 1972, as amended (mostly recently in 2015). The MMPA protects all marine mammals, including cetaceans, pinnipeds (seals and sea lions), sirenians (manatees and dugongs), sea otters, and polar bears within the waters of the United States. The Act makes it illegal to "take" marine mammals without a permit. This means people may not harass, feed, hunt, capture, collect, or kill any marine mammal or part of a marine mammal. Dwarf sperm whales are currently listed as Data Deficient on the IUCN Red List. They are fairly abundant, but there is no information on global population trends. Like many other marine species, they are susceptible to entanglement, incidental take, interactions with fisheries, and pollution. Evidence from stranded whales show that some dwarf sperms have ingested plastic and other garbage, which blocked their intestinal tracks. Additionally, they are vulnerable to ship strikes due to their logging behavior. High levels of anthropogenic sound also have the potential to impact all deep-diving toothed whales, and mass stranding events have been associated with such. Though historically dwarf sperm whales were targeted by whalers, these days there are few serious human impacts affecting this species. In fact, they are probably relatively less affected by human activities than many of their cetacean cousins.

Towards thee I roll, thou all-destroying but unconquering whale; to the last I grapple with thee; from hell’s heart I stab at thee; for hate’s sake I spit my last breath at thee. Sink all coffins and all hearses to one common pool! And since neither can be mine, let me then tow to pieces, while still chasing thee, though tied to thee, thou damned whale! Thus, I give up the spear!
~ Ahab’s final words (Herman Melville, Moby Dick)

Where I learned about dwarf sperm whales, and you can too!

National Oceanic and Atmospheric Administration
sero.nmfs.noaa.gov/protected_resources/outreach_and_education/documents/protected_species_gom.pdf
www.nmfs.noaa.gov/pr/species/mammals/whales/dwarf-sperm-whale.htmlswfsc.noaa.gov/textblock.aspx?ParentMenuId=230&id=1428

World Register of Marine Species
seamap.env.duke.edu/species/tsn/180492

IUCN Red List
www.iucnredlist.org/details/11048/0

The Pacific WildLife Foundation
www.pwlf.org/dwarfspermwhale.htm

Whale and Dolphin Conservation
us.whales.org/species-guide/dwarf-sperm-whale

Whale Facts
www.whalefacts.org/dwarf-sperm-whale-facts/

Save the Whales
savethewhales.org/dwarf-sperm-whale/

Animal Diversity Web
animaldiversity.org/accounts/Kogia_sima/

The Mammals of Texas
www.nsrl.ttu.edu/tmot1/kogisimu.htm

MarineBio
marinebio.org/species.asp?id=327

The Marine Mammal Center
www.marinemammalcenter.org/what-we-do/rescue/marine-mammal-protection-act.html