Recently, my lab decided to ditch the whole “doing science on a Friday” thing, and instead, go on a field trip. Roughly 1.5 hours from Stanford lies Ano Nuevo, a California State Park, and home of the largest mainland breeding colony of northern elephant seals in the entire world.(1)
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There are two species of elephant seals, northern and southern. Northern elephant seals hang out in the North Pacific, ranging from Baja California to Alaska. Southern elephant seals, being aptly named, inhabit the sub-Antarctic and Artic waters.
Northern elephant seals are very large. The only seal bigger than a northern elephant seal is a southern elephant seal. They can be mistaken for very large logs (this, I have done). Adult males can grow to over 13 feet, 4,500 pounds; females generally weigh in at 10 feet, 1,500 pounds.
A “seal” can belong to one of three families of fin-footed mammals: Odobenidae (walruses), Otariidae (eared seals, e.g. sea lions), or Phocidae (earless, or true seals). Elephant seals are true seals - they don’t have external ear flaps, and they get around while on land by throwing themselves along the ground. It’s hysterical to watch, until you realize that 4,500 pounds of seal is throwing itself at you, at a rate of up 8 miles an hour.
For most of the year, elephant seals are solitary animals, spending most of their time migrating. Ano Nuevo female elephant seals, fitted with satellite tracking equipment, have ventured as far north as Alaska, and as far west as the International Date Line.(4)
During the 19th century, humans hunted the elephant seal nearly to extinction, for their blubber (used for lamp oil, similarly to whale blubber). Massive conservation efforts, and the invention of electricity, have restored population numbers from less than 100 seals in 1910, to approximately 150,000 today.(5)
During the breeding season, elephant seals throw a beach party during which time males fight to establish dominance, females give birth and then mate with the dominant males. During this time, the elephant seals will abstain from both food and water.
The “elephant” part of the elephant seal’s name is not a comment about its size. Instead, it refers to the adult male elephant seals nose (or proboscis), which, if you want to be excessively polite about it, looks like an elephants trunk. Dominant males inflate their noses to produce a noise that sounds like a cross between a stalling chain saw and an elephant with irritable bowel syndrome.(6)
The proboscis isn’t merely the elephant seal’s attempt to win the animal kingdoms Ugliest Mammal Award, the enlarged nose contains highly convoluted nasal cavities (measuring up to 3140 cm2 in an adult male); this enlarged surface area allows elephant seals to reabsorb enough moisture from their exhalations to maintain water balance during the extended fast of the breeding season.(7)
Despite being mammals, and thus needing air to breath, elephant seals spend most of their time deep underwater – 91% of their time at sea is spent diving Our Ano Nuevo docent stated that the movement of an elephant seal descending underwater is be best described as “the same motion as a leaf on the wind”. A 4,500 pound leaf.(8) An “integrative hierarchical Bayesian state-space” model of Southern elephant seal movements, used to quantify how environmental factors influence an individual seal’s movement, is a thing that exists.(9)
Elephant seals hunt deep underwater, where light is scarce. Elephant seals are not equipped with echolocation, one very useful way to find stuff to eat when hunting in very dark water (see: whales). Instead, elephant seals have adapted their vision to be highly sensitive to low intensity light, with peak sensitivity at 485 nm. Coincidentally, 485 nm is the wavelength of bioluminescence produced by the southern elephant seal’s main prey: myctophid fish.(10)
3. Methods: A Pubmed search for Mirounga generated an extensive list of journal articles relating to elephant seals. Journal articles were selected from said list on the basis the level of awesomeness evident in the abstract. Back to text
4. Source: Robinson et al (2012). Foraging behavior and success of a mesopelagic predator in the northeast Pacific Ocean: insights from a data-rich species, the norther elephant seal. PLoS One. 7(5):e36728. Back to text
6. Go home evolution, you are drunk. Back to text
8. Which is less like a leaf on the wind, an elephant seal, or Walsh, piloting Serenity? Thinking about which option just made you sadder? (This joke is dedicated to K.Bryant) Back to text
9. Source: Bestley et al (2013). Integrative modeling of animal movement: incorporating in situ habitat and behavioural information for a migratory marine predator. Proc Biol Sci. 280(1750):20122262. Back to text
10. Nicely done, evolution. Source: Vacquie-Garcia et al (2012). Foraging in the darkness of the Southern Ocean: Influence of bioluminescence of a deep diving predator. PLoS One: 7(8):e43565. Back to text