Nature Notebook, September 13, 2018

09/12/2018

The autumnal equinox, the first calendar day of fall, approaches on Saturday, Sept. 22 with equal hours of daylight and darkness. It is closely followed by the full moon on Sept. 24, this year’s harvest moon, traditionally providing extra light for the fall harvest in many communities. The Cree people of Ontario call it the rutting moon, for the many species of deer—like our tule elk—that breed this season.

Winter brings the annual gray whale migration along the coast, but fall brings humpbacks. Reports of humpbacks from Bolinas and the lighthouse, as well as the Monterey Bay, have added extra excitement this year. They may cooperatively forage for krill, herring and other schooling species in small groups of two to three and then move on to other groups. The seafood diet builds up fat reserves that they live off of during the winter. Humpbacks are distinguished from other whales by the light-colored patterns on their flukes, their long flippers and the lumps, or tubercles, on their head and jaw.

A shiver of sharks—leopard sharks, that is—is sometimes visible behind the Inverness Store and along the west side of Tomales Bay. The sharks travel on the high tide into the shallow mudflats along the coast to eat worms and clams, digging in the mud for innkeeper worms and grabbing clams by their siphons (or necks) and yanking them out of their shells. Leopard sharks, common in the bay and the Pacific Coast, are so named because of their mottled skin.