SF Natural History Series

Opossums (and introduced species) and their “cousins” skunks, raccoons and others are doing well with those teeth, living in amongst us, and living off of us. Skunks love our lawns for their grubs and worms, raccoons love our garbage cans, and opossums seem to like to eat anything. With restoration efforts some of the less human adapted meso predators are doing well, ringtail cats in riparian environments, mink in the delta, and river otters.

Meso predators are defined by a certain mass and a certain function — they are not the top tier predator, but if the top is eliminated they can actually do quite well as the apex predator. This is what has happened to the coyote where wolves have been eliminated. The apex predators are often extremely unforgiving of the mesopredators: wolves will kill coyotes, lions will kill cheetahs and hyenas.

Of course meso predators can also have devastating effects. A guest of Mr Martin’s: Dr Frank talked about his experience studying (as a FWS tech) the Aleutian Goose in the Aleutian Islands, and how a fox introduced for their fur (in 1750), wiped clean of birds island after island. The foxes managed to survive after this decimation by living off of the abundance of isopods on the beach. More details of the Foxes here.

Glen Martin discussed feral cats as being a significant cohort of this type of predator, and their potential as a force for habitat discussion.

This most interesting part of the evening was the talk around the interrelation of predators and how changing those relationships adding or removing predators can have profound impacts on the local environment. The most famous example is that of Yellowstone where the re-introduction of wolves has  kept elk moving and out of the plains, which has allowed things like river side Willows to grow, which has provided fodder for beaver who also had been gone from the park.

But if you want to find out more about the meso-predators we live with, you can get an intro to the subject through his Bay Nature article from July 1st of 2011, the Middle Way.