PACK RAT AS AN ENEMY OF NATURAL REPRODUCTION 419 



area with a number of nests not far from the boundary of the plot. 

 Since the area was laid out there has been no attempt to reduce the 

 number of rats on the plot and an examination of the area in the 

 season of 1916 showed that 9 nests were still inhabited. 



The damage done by these rodents to the natural reproduction ex- 

 isting on the plot is shown in Table 1, in Which the location of the 

 trees with respect to the brush is indicated by the columns headed 

 "open," "open brush," and "dense brush." "Dense brush" indicates a 

 density of more than .5, "open brush" of less than .5, and "open" the 

 absence of brush or its presence in such small amounts and of such 

 intolerant species, as sage, as to make it practically negligible. 



In this table trees which are designated as being severely injured 

 are those which are so badly damaged that their existence is placed 

 in jeopardy. Only very little further work would be required to kill 

 the tree, while its growth is probably inhibited. The slightly injured 

 trees are those with small injuries such as the loss of side branches, 

 gnawings on twigs or stems, and superficial wounds which do not 

 affect seriously the growth and development of the tree. 



The trees that have been killed died as a result of girdling. In 

 nearly every case the bark on the main stem has been almost en- 

 tirely removed from the ground line up to the topmost branches or to 

 that point on the stem where the needles still persisted, while the side 

 branches have suffered in a similar manner. The presence of needles, 

 whether dead or alive, appears to act as a deterrent to further action 

 on the part of the rat, for it was noted that no damage of any nature 

 was in evidence beyond them except where the stem of an adjacent 

 bush came between the nodes. In this latter case, stems were cut off 

 or slight damage was done by barking. Tabde 2 shows the location 

 of the girdling for each size class where the trees were killed, though 

 some bark still remained in places on the stems. 



Table 2. — Number of Trees Girdled, According to Height Classland Height at which 

 the Girdling Occurred 



Height Total Location of Girdling by Feet from Ground 



trees trees 



in feet killed ^'^^^^ Second Third Fourth Fifth Sixth 



111... 



2 11... 



3 111. 



4 8 8 6 5 



5 2 2 2 2 2 



6 7 5 7 7 7 6 



7 2 2 2 2 2 2 



8 2-2 2 2 2 2 

 10 1 1 1 1 1 1 



