So what does our research show attracts so many owls to our land? Rats. That's right. The creatures that would make most of us pack up and leave a neighborhood are exactly what encourage the owls to move in. And not just any rat - the dusky-footed woodrat.
The prey on which the owls feed proved to be key in understanding the presence and prosperity of the spotted owl in this region.
While spotted owls throughout much of the rest of the Northwest feed mostly on flying squirrels living in mature forests, studies indicated that spotted owls on California's North Coast feed primarily on dusky-footed woodrats living in very young forests.
This discovery prompted a study on the abundance of woodrats in redwood forests throughout our California ownership. This study indicated that woodrats were most abundant in young stands - those that were 10-20 years old.
Preliminary data from an additional, ongoing study through Humboldt State University shows a similar abundance of wood rats in Douglas-fir forests.
These results helped us understand why spotted owls in this region do well in areas that include both young and mature trees.
Wildlife biologist and others at Green Diamond have continued to study woodrats on California timberlands to better understand how different methods of harvesting trees effect woodrat numbers.
These studies, although not yet published, indicate that opening up the forest to allow sunlight to reach the forest floor allows the growth of the shrubs on which woodrats depend for food.
Given the importance of woodrats as the prey of spotted owls, these results would also suggest that spotted owl populations in this area are best supported in forests that are managed using even-age management.
Published studies and other scientific reports on dusky-footed woodrats:
Hamm, Keith A. 1995. Abundance of dusky-footed woodrats in managed forests of north coastal California.
M.S. thesis, Humboldt State University, Arcata, CA.
Hamm, Keith A., Lowell V. Diller and David W. Kitchen. In press. Comparison of indexes for estimating
abundance of dusky-footed woodrats. Wildlife Society Bulletin.
Hamm, Keith A. and Lowell V. Diller. Effects of forest age and silviculture on the abundance of
dusky-footed woodrats in coastal northern California. Will be submitted to the Journal of Wildlife Management.