Saturday, January 20, 2007

A Day in the Life of a Farallones Biologist

The winter crew watches the sun set on another beautiful day on the Farallones.

During the winter season we primarily study the demography (reproduction, survival, and population change) of the Farallones northern elephant seal population. These parameters can be determined by individually marking the elephant seals to see where they move, how long they live, how often they reproduce and whether their pups survive. We put permanent colored plastic tags with a unique number and letter combination in their hind flipper that we can re-read year after year – and we give each tagged animal a name.

For short-term tracking within the breeding season, we stamp a unique number on each adult elephant seal with blonde hair bleach and black hair dye generously donated by Clairol. The bleach and dye numbers disappear when the animal molts in a few months. But during the breeding season (December through March), these big, clearly stamped numbers allow us to efficiently keep a daily count of seals arriving, defending harems, giving birth, nursing, and departing. We check all the breeding beaches in the morning and again in the afternoon to get the count.

Every pup gets the same stamp number as its mother so we can monitor each female’s reproductive success and pup fate. Also, the number helps us to identify the pup so we can tag it once it is weaned and we’ll know the exact age and who its mother was when we see the animal again in future years. See the picture below of the cow Drip and her pup – they are both stamped “-25,” and Drip's tags are also visible.

At about 110-180 pounds, your average Homo sapiens biologist poses no threat to a 5,000-pound bull male northern elephant seal. These large males are remarkably tolerant of human presence and do not seem to mind if we get close enough to read their tags or stamp a number. But, of course, we still tread very carefully around these animals, as one misstep could yield some painful results!

In addition to intensively studying the elephant seals, we monitor the abundance of California and Stellar sea lions, northern fur seals, harbor seals, arboreal salamanders, and the huge variety of bird species that utilize the Farallones. As part of the overall research we record air temperature, wind speed and direction, and ocean conditions three times per day and we measure sea surface temperature once per day. This is so biologists from PRBO Conservation Science can investigate how atmospheric and ocean conditions over time affect the demography of birds and pinnipeds that breed on the Farallones. In doing so, the biologists document the impacts of climate change on the rich marine life of the Gulf of the Farallones.

Finally, we post a lookout at the lighthouse to observe and record whales, sharks, dolphins, and any other interesting and notable wildlife that come to the island’s waters to feed or just pass by on their annual migration. For example, the other day we saw a pod of 8 Orca in the waters just off West End Island, and another day 500 Risso's Dolphins swam by. Our one-day high count of grey whales migrating south to calve and breed in Baja California, Mexico is 58.

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