|Read http://losfarallones.blogspot.com/ to learn about PRBO biologists' latest Farallon observations.|
|Derek Lee looks over the breeding elephant seals on Sand Flat.|
Winter is elephant seal breeding season on the Farallones, and right now on Sand Flat, SEFI's main elephant seal beach, the number of elephant seal cows and pups is growing by the day. As in years past, the known-age cows named First Cow, Giovanna, Schnitzel, and Drip were the first to arrive and have pups. (Island tradition calls for these animals to go by nicknames, not tag numbers). They evidently like to arrive early to take advantage of the uncrowded beach to nurse their pups without too much wrangling for precious space.
Later in the season Sand Flat holds scores of cows and pups, and mayhem often ensues. Even this early in the season, the beach is starting to get a bit crowded, and the confusion has resulted in a few dead pups. As of 25 January, SEFI has106 cows and 73 pups, with three or four new cows and pups arriving each day! The beach resonates with the cries of the little seals and the gentle responding "pup sound" that the mother makes to reassure her pup that she is nearby.
The timing of cow arrival at the Farallones each year (known as phenology) has changed over the decades. This could be due in part to changes in the average age of the cows breeding here. These islands were first colonized, in the 1960s, by young animals dispersing from colonies at Año Nuevo and the Channel Islands of Southern California. Many demographic traits change with the overall age of the population.
|Monitoring data on Farallon populations includes tagging and following known individuals.|
The shifting phenology is also due to changes in the ocean-climate, with periods when food was more or less abundant and cows returning to SEFI earlier or later as a result. Our research has found that phenology is closely correlated with North Pacific sea surface temperature: cooler, more productive waters mean earlier phenology and higher reproductive success.
As I mull over the 30-plus years of marine mammal data that PRBO has collected at the Farallones, I look forward to the discoveries yet to be derived from this amazing resource. Throughout the winter, Common Murres attend their Farallon breeding colonies to reunite with their mates. A few hours spent in the murre blind, resighting banded individuals, gets me thinking about analyses and papers I might write about these seabirds of the California Current. With our new microwave link to the Internet, I can pursue a range of potential research questions and access some of the latest findings in the scientific literature.
What's more, working amidst the natural spectacle of the islands and surrounding ocean is incredibly inspiring. Early in the winter we see white shark attacks; then the elephant seal breeding season starts; then comes a stream of migrating grey whales. Every so often I witness something extraordinary--a "superpod" of 500 or 1,000 Risso's or common dolphins, or a family of orcas.
Being stuck on a tiny rock at the edge of the continental shelf all winter is the perfect situation f