August 3, 2010

Does Granny Breach Less?

The oldest member of the Southern Resident Community is named Granny. She is estimated to be a 100 years old. She is also the matriarch of J-pod. Her cohort is a 60 year old male named Ruffles. Ruffle's dorsal fin is 5 to 6 feet tall, a common measurement for adult males, as compared to the 2 to 3 foot tall dorsal fin of the average female. A juvenile male is indistinguishable from a female with the exception of their ventral markings. A small black dot on each side of the ventral slit distinguishes female from male. Those are her mammary glands. When the juvenile male hits puberty around age 14, his dorsal fin starts sprouting. If these pubescent youngsters are anything like humans, they'd be horrified that we call them 'sprouters,' but its an accurate term considering that their dorsal fin may grow a foot in a year.

As the adult male orca ages, the water pressure combined with the renewed force of gravity as they surface to breathe results in a wavy dorsal fin, much like we start to get jowls and crow's feet. This effect is especially apparent in transients. These marine mammal eating orcas have dorsal fins that are broader and taller than the residents. As they age, the male's dorsal fin can take on an umbrella hook, in which the whole thing stands straight up with the exception of the very tip, which curls over creating the hook at the end of the umbrella handle.

Lately, people have been asking, "Does Granny breach less?" Because of her advanced age this seems like a distinct possibility, but we have seen Granny breach a few times over the past few years. Orcas breach for a myriad of possible reasons. Ruffles was traveling north with several pod mates a few miles behind him. Both groups turned around and started heading south at exactly the same time. This may have been coordinated through breaching or tail lobbing since the sound of their bodies slapping the surface of the water can travel for miles under water. Sound travels 2 miles per second underwater. They may breach as a hunting technique to shock and stun fish...and Granny still has to eat, even at her ripe age. They also breach as a mating display and believe it or not, we still see the old timers mating. Go Granny!

Lauren Sands

Naturalist

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