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RESEARCH NOTE LS-16 



• LAKE 



STATES FOREST EXPERIMENT STATION • U.S. DEPARTMENT OF AGRICULTURE 



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Porcupine Winter Feeding Activity in Merchantable Stands 

 of Northern Hardwood— Hemlock 





Porcupine sometimes cause considerable 

 damage to both hardwood and conifer species 

 in Lake States forests. But little is known of 

 the population levels that result in appreci- 

 able damage or of the animal's behavior pat- 

 terns. Although recent injury can be readily 

 tallied from the ground, assessment of past 

 animal activity on the standing tree is dif- 

 ficult. A complete picture for a period of 

 years can be obtained only by examining the 

 tree crowns after a cutting operation. 



In the fall of 1961, a study of porcupine 

 activity in northern hardwoods was conducted 

 by the University of Michigan in cooperation 

 with the Station. Tree tops from a commercial 

 lumbering operation near Golden Lake on the 

 Ottawa National Forest in northern Michigan 

 were examined. A sample of 288 tops was 

 chosen objectively, and current and past por- 

 cupine damage was recorded as to year of 

 feeding, feeding intensity, and location on 

 the tree. The sample was biased in that selec- 

 tive marking favored the removal of trees of 

 poor form and low value. Yellow birch, bass- 



wood, and sugar maple were favored for re- 

 tention, while proportionately more hemlock 

 and elm were removed. Since hemlock is a 

 preferred winter food and elm is also favored 

 by the porcupine, the sample probably in- 

 cluded more trees likely to have suffered 

 from feeding than those uncut. 



The size of the trees cut ranged from 5 to 

 35 inches d.b.h., although most were between 

 14 and 24 inches d.b.h. Within this range, 

 neither tree height nor d.b.h. had a significant 

 effect on porcupine activity. 



Kind and location of trees used by the 

 porcupines were also studied as related to 

 other habitat components such as the pres- 

 ence of den trees and stand composition. 



Fifty-eight percent of the trees examined 

 had been gnawed on sometime during the 

 past 20 years (table 1). Of the total sample, 

 30 percent (50 percent of those gnawed) 

 showed a high degree of activity, defined as 

 girdling or stripping of large patches of bark 

 ( fig. 1 ) . Eleven percent of the trees had been 

 gnawed within the previous 2 years and 5 



Table 1. — Porcupine activity by tree species at Golden Lake, Mich. 



Species 



Number of 

 tops in 

 sample 



Percent 



mawed within 



each species 



Species preference — 

 expressed as a ratio 1 



Sugar maple 



170 



51.8 



Yellow birch 



55 



50.9 



Hemlock 



32 



90.6 



Elm 



17 



94.1 



Basswood 



8 



75.0 



Red maple 



2 



50.0 



Ironwood 



2 







Black cherry 



1 







White spruce 



1 







.89 

 .87 

 1.55 

 1.61 

 1.29 

 .86 

 0.0 

 0.0 

 0.0 



Total 



288 



58.3 



This ratio is the percent of trees gnawed within a species divided by the 

 percent of all trees gnawed. 



MAINTAINED AT ST. PAUL 1, MINN E S OTA , IN COOPERATION WITH THE UNIVERSITY OF MINNESOTA 



