Elephant Seals
Elephant Seals About the Friends of the Elephant Seals The Elephant Seals View the Friends of the Elephant Seals Resources Join the Friends of the Elephant Seals Elephant Seal Shopping Friends of the Elephant Seal Home Elephant Seals

 

A recent study* produced some results and a presentation that is very interesting.

 

Data on the tracking of 321 adult female seals was used to produce a "chorus" that captured some characteristics of their sea voyages - roughly 80 days post breeding and 200 days post molting. Most of the seals were from Ano Nuevo but 20 were from a colony on Islas San Benito, Mexico. The trips took place between February 2004 and May 2014.

 

Data collected was considerable: over 90,000 seal-hours and over 1 million individual positions. The purpose of the study was to explore the utility of an acoustic presentation of part of this data. Each seal at sea contributes a tone that varies with latitude, lowering in frequency as it moves west. The combination of the tones of all the seals in the ocean at that time has a volume that depends upon the spread of the group: high when close together, low when widely separated.

 

Click on the Play arrow to see a time dependent picture of the travels of the seals over 21 trips, recorded over 10 years. The time scale is, however, reduced by a factor of 1/90,000 (1 second video time is 1 day real time) so that the whole decade is condensed to just under an hour. Seals in the image are different colored "worms" moving about the ocean. The length of these "worms" is a measure of their speed (except for a obvious glitch in the second year).

 

It is interesting to follow individual seals and see the various strategies. If the worm shortens to a dot, that seal has presumably found a rich source of food. One seal during the long migration of the third year (2006) went out to sea briefly and then spend many months in Monterey Bay. Some make a bee line for the Gulf of Alaska, outside the area generaly used by the females.

 

However you feel about the effectiveness of the acoustic signal in communicating the travels of the seals, you will probably find the presentation interesting. The labels are indistinct but the top graph below the image is the distance traveled by an individual (color coded) seal, the lower graph is the spread of the group at sea. The units along the horizontal axis are months. It is recommended that you view this full screen.

 

 

*Duarte CM, Riker P, Srinivasan M, Robinson PW, Gallo-Reynoso JP and Costa DP (2018) Sonification of Animal Tracks as an Alternative Representation of Multi-Dimensional Data: A Northern Elephant Seal Example. Front. Mar. Sci. 5:128. doi: 10.3389/fmars.2018.00128