Friday, January 05, 2007

Crowds of Cows (and pups)

The number of cows and pups on SEFI’s main elephant seal beach, Sand Flat, is growing by the day. Once again, First Cow, Giovanna, Schnitzel, and Drip had the first pups of the breeding season – they like to arrive early so they can take advantage of the uncrowded beach to nurse their babies without too much wrangling for precious space. Later in the season Sand Flat will have scores of cows and pups and mayhem often ensues. In fact, it is starting to get a bit crowded already. There are 21 cows and 12 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 possibly be due to changes in the average age of the cows breeding here. The islands were first colonized in the 1960s by young animals dispersing from colonies at Año Nuevo and the Channel Islands of Southern California. The graph here shows the median arrival date of females to SEFI from 1974 until 2006. The shifting phenology could also be due to changes in the ocean climate causing periods when food was more or less abundant and cows returned to SEFI earlier or later as a result. Our research has found that during the last 15 years, earlier phenology means higher reproductive success.

Below, we profile a few of the cows we’ve been tracking since their birth.

Mercury was born on Sand Flat in 1990, making her a whopping 17 years old this year! She’s given birth 10 times on the very beach where she was born, producing seven healthy weaners. Furthermore, Mercury’s pup from 1999, Princess Superstar, returned to SEFI this year as a pregnant cow. Both of them just gave birth in the past couple of days, resulting in three generations together on the beach. Mercury and Princess Superstar spend a lot of time near each other – perhaps the bonds of kinship reduce antagonistic behavior that decreases nursing time and hinders pup development.

Another relatively old female on Sand Flat is Drip. Drip was born in 1992 at Shell Beach on West End Island. Like Mercury, Drip has been returning to Sand Flat for the past 10 years. In her first year breeding, her pup washed out to sea but since then she has also successfully produced seven weaners. Drip was one of the first cows to give birth this year and her pup is one of the fattest on the beach.

Queen Latifah was born on Sand Flat in 1999. This is her first year returning to SEFI and she’s now nursing her pup that was born on New Year’s Eve. She is a relatively calm cow who really seems to enjoy her sleep – unlike some of the others who spend lots of time snarling at neighboring cows. Since this is her first year back at SEFI, we’re not sure where and with whom she mated last year, but we’re happy to see her back home.

Maddy also was born on Sand Flat in 1999, first returned in 2003, first pupped in 2004, and has given birth here every year since. Unfortunately, she is only “one for three” so far, with only one successful weaner, but she is young yet. She hasn’t pupped yet this year but we’re checking the beach every day.

Schnitzel is a relatively young cow, born on Sand Flat in 2000. This is Schnitzel’s third year returning to SEFI to pup. Hopefully the third time’s the charm. In 2005, she did not nurse her newborn pup and it died, but we chalked it up to the terrible wounds Schnitzel had on her head and back from an attack by an over-enthusiastic male elephant seal. Last year Schnitzel abandoned her pup as soon as it was born, which often happens with younger, inexperienced cows. Happily that year, First Cow adopted Schnitzel’s abandoned pup and nursed it for several weeks. This year Schnitzel hit her stride and her pup is looking nice and fat. This year, in an interesting karmic twist, Schnitzel herself appears to have adopted an abandoned pup.

Christine is another relatively young cow from the class of 2000. She pupped successfully on Sand Flat in 2004 but she didn’t breed here for the past two years. We’re glad that she is back. She hasn’t given birth yet but it will probably happen any day now.


Anonymous said...

Have you tracked any males, ala Mercury, and if so results, and if not, why?

Los Farallones said...

Hi rcferris! In answer to your question, we do track the males as well as the females. If you scroll down to an earlier posting (Bulls on the Beach) you'll see a profile of just some of the males we've tagged and been tracking each year. The current reigning bull on Sand Flat, Nero, was tagged on Point Reyes Peninsula. We also have several males who were born here and tagged as weaners, and have returned to try their luck with the Farallones females. Of course, we can't be too sure about paternity of the pups (the way we know maternity) se we can't determine actual reproductive success of the males. We could determine paternity only by taking genetic samples of each pup and male.