Lawrence Perretto
NASA Life & Marine Science 
Online Analysis Journal Two
4/25/12
While exploring various species on the ACES website for this second journal analysis, I was struck by the consistency of movements apparent in the data on the Northern Elephant Seal. Lacking adequate background knowledge, I was intrigued when initial research revealed that except for mating and molting, elephant seals are offshore marine mammals that spend most of their lives thousands of miles from the Pacific coast. This is an interesting and somewhat mystifying life history, for the habits of many open-ocean, “pelagic” animals, are largely unknown. Elephant seals are native to the eastern Pacific Ocean. They travel from their breeding colonies in Mexico and California to the Aleutian Islands in Alaska to feed. Migration repeats every six months as elephants seals return to their breeding colonies to molt. While traveling the open ocean, I find it remarkable that elephant seals spend most of their time below the ocean surface, diving to the staggering depths of 1,500 meters feet to hunt for food.  The elephant seal is adapted to a varied diet, feeding opportunistically on skates, rays, octopus ,small sharks and other deep dwellers. Northern elephant seals have large eyes for light gathering in the depths. However, with sunlight penetration terminating at 200 meters, elephant seals are clearly proficient predators in the dark.  It would be fun to research elephant seal anatomy and physiology to study other ways in which elephant seal are adapted to deep diving conditions to feed on bottom dwelling fish and other benthic organisms. I am particularly fascinated by a behavior from which scientists infer that elephant seals rest in a sleep-like state while diving. Specifically, what physiological mechanism engages during these periods of rest while diving that enables elephant seals to avoid their only known predators, the orca and great white shark? I am also curious about the physical adaptation enabling elephant seals to withstand the enormous water pressure at such depths while lacking external ear flaps that protect the inner ear. There must be an anatomical adaptation that protects the inner ear assuming, that it, that elephant seals have an inner ear. 
Source: Marine Mammal Center: http://www.marinemammalcenter.org/education/marine-mammal-information/pinnipeds/northern-elephant-seal/
When analyzing the ACES data one cannot help notice the pattern of movements indicative to all fifteen elephant seals being tracked.  It is clear that for the Northern Elephant Seal, all roads lead to the Monterey Bay National Marine Sanctuary.  However, in terms of correlating ACES data sets with elephant seal movements the mysterious habits of the northern elephant seal remains elusive.  For example, Pacific Ocean bathymetry is relatively smooth and does appear to be a factor in elephant seal migration except for seals # 03429 (black) and # 044364 (grey) both of whom show a preference for the narrow continental shelf stretching northward from Monterey  to the coast of Alaska in water less than 100 meters deep. For the remaining seals being tracked by ACES, there does not appear to be any features of bathymetry directly connected to seal movement. Considering elephant seal diet and the duration of feeding dives, it might be inferred that elephant seals cruise the mostly featureless Pacific floor in search of food.  
Surface temperature is another data set with tacit correlation to elephant seal movements. At first glance, we observe thirteen of fifteen elephant seals in the area of surface water ranging in temperature from 10-14 degrees Celsius. However, one wonders the extent to which surface temperature influences the movements of an animal that spends less than half an hour per day at the surface.  Again, life history and the pattern of remaining at the surface for two–three minutes for a quick breath of air before returning to the depths calls into question a correlation between sea surface temperatures and elephant seal movements.  Likewise the plankton data set below. Considering that sunlight does not penetrate the ocean beyond 200 meters and that elephant seals are feed at depths up to 1,500 meters, it can be inferred that the connection between plankton and elephant seal prey is not well established. Except for #3429 & #44364, all elephant seals under observation are feeding below the euphotic zone of maximum light penetration. As opportunistic feeders, we can infer elephant seals will feed while diving. However, the fact that elephant seals do not appear to track migrating pacific salmon supports the inference that elephant seals prefer to feed on or near the bottom. 

I remain hard-pressed to justify why the northern elephant seal inhabits the Pacific Ocean. Elephant seals do not appear to be greatly influenced by Pacific Bathymetry, sea surface temperature or plankton concentrations. The elephant seal is therefore enigmatic with more questions than answers. What is it about the open ocean that attracts elephant seals? How frequently do elephant seals feed in the eupohtic zone that would support a connection to plankton concentrations?  If feeding is simply a matter of finding fish, why don’t elephant seals demonstrate a greater reliance on migrating salmon? Knowing very little about elephant seals prior to this analysis I must admit I am deeply (pardon the pun) intrigued by the mystery of their habits. As previously observed, all roads for Northern Elephant Seals lead to and from the Monterey Bay National Marine Sanctuary. MBNMS must be the most important, perhaps even omnipotent factor in the lives of elephant seals. It is no wonder considering the abundant habitat and food resources in and around the Sanctuary.  However, I am stymied and cannot justify elephant seal movements based on the data sets above. 
Now you can understand why I am unable to present at the marine educators conference.