Friday, June 7, 2013

TOPP tags elephant seals

In a feature posted on the Tagging of Pelagic Predators site in 2008, researchers show how they go about tagging elephant seals: Very carefully!

From the site:

Northern elephant seals (Mirounga angustirostris) dive deep, routinely to 1,800 feet (600 meters), sometimes to 4,650 feet (1,550 meters). Elephant seals are one of TOPP's star animals. They spend 10 months a year at sea, so they bring back lots of data. They're so large that a couple of robust satellite tags weighing two pounds makes up a mere one percent of a female seal's weight. That's a small pack of gum to a 150-pound human. And because they usually return to the same beach a couple of times a year, it's easy to attach and remove the tags.
Since 1983, when elephant seals first carried depth recorders, they've been central to the development of a variety of tags that:
-- use light level to determine location,
-- use digital electronics to gather physiological data,
-- use an acoustic data logger,
-- provide ocean temperature profiles.
We've also put crittercams on them to watch how they find food and swim.
We can marry elephant seals' migration tracks with satellite information about the ocean. We see males heading way out to sea and diving deep to find food, while females seem to linger around ocean "hot spots", slowly moving eddies where there's a lot of life (and hence a lot of grazing and feeding).

However, significant questions remain. It is important to know whether elephants seals from the Guadalupe, San Miguel, San Nicolas, and Año Nuevo colonies migrate to different places in the ocean. It's likely that weanling or juvenile elephant seals feed in different areas than adults. We'd also like to know where the weanling elephant seals go when they first venture to sea, because more than 50% do not survive. It's important to know so that we can predict how a population of seals might fare as the climate changes.

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