Document Type


Publication Date



Commensalism; Tamiasciurus; Yellow-bellied sapsucker; Hummingbirds; Itasca, Lake (Minn.)


This is an investigation of a relationship noted at the Lake Itasca Biological Station. It was noted that the Red Squirrel, Tamiasciurus hudsonicus, in some locations spent a considerable amount of time lapping sap from the rows of holes drilled in the White Birch, Betula papyrifera, by the Yellow-bellied Sapsuckers, Sphyropious varius varius (L.). After the invasion of the red squirrel the sapsuckers and the Ruby-throated Hummingbird, Archilochus colubris (L.) continued to utilize the same food supply as well as a considerably number of insects. The two general objectives of this endeavor were then to investigate some of the related ecological factors and to gain observation data to aid in determining the status of this relationship. Odum (1959) defines commensalism as a relationship that requires a mutual aid for survival. Guyer ( 1948) refers to commensalism as being an association of messmates. By noting all of the animals concerned it was hoped it could be determined if this was a true commensal situation.

The area under consideration was located in Clearwater County in Lake Itasca State Park. The study of the problem was restricted to the University of Minnesota Biological Station and the point of land extending into Lake Itasca known as Bear Paw Point.

First Page


Last Page


Primo Type


Included in

Zoology Commons



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.