DAMAGE TO RANGE GRASSES BY THE ZUNI PRAIRIE DOG 7 
fewer shoots are produced each season. Under such conditions, 
sagebrush (Artemisia), rabbitbrush (Chrysothamnus), snakeweed 
(Gutierrezia), and finally annual weeds come in and tend to replace 
the wheat grass. All these were present on the areas during the 
spring of 1918. Under grazing conditions not so destructive the 
wheat grass is slowly replaced by blue grama. This had apparently 
in some measure occurred here. 
Under total protection the wheat grass increased to a remarkable 
extent the first two years, but very slowly afterward. By 1919 a 
stable relationship had apparently been reached between the number 
and size of shoots of all grasses and the amount of water available. 
The year’s rainfall was unusually favorable and the total amount of 
forage has not increased much since that time, but has fluctuated 
with the season. The wheat grass, however, has made consistent 
gains as a result of successful competition with the dropseed. Very 
little change has taken place in the wheat grass on the cattle-grazed 
area during the period of the experiment, a gradual increase occur- 
ring until 1919, probably as a result of eradicating the prairie dogs, 
after which time the growth fluctuated with the rainfall. In the 
rodent-grazed area, however, this grass showed a consistent decrease 
until 1922, when the amount of it, practically doubled as a conse- 
quence of lessened rodent infestation. 
Blue grama (Souteloua gracilis) occurred in small quantities on 
the areas in 1918. On the cattle-grazed portion it has shown a slow 
consistent increase each year. In the protected plot and in the ro- 
dent-grazed plot this grass more than doubled in quantity by the end 
of the growing season of 1919. This, as in the case of the other 
grasses, was the result of protection against cattle grazing and the 
decrease in number of prairie dogs in the inclosure. The grama 
showed little change in the protected area during 1920 and decreased 
somewhat in 1921 and 1922, as a result of competition with the other 
grasses. In the rodent inclosure it continued to increase somewhat, 
since rodent grazing favored this grass by comparison with the 
others. 
In 1922 (October 24) sand dropseed (Sporobolus cryptandrus) 
was found growing in the prairie-dog area somewhat more abun- 
dantly than before, indicating a decrease in grazing by prairie dogs 
since the last preceding inspection (fall of 1921). Needle-and-thread 
grass (Stipa comata) was found on the areas for the first time, 
there being an older plant surrounded by a considerable number of 
. younger but seeding individuals as well as several seedlings. June 
grass (Koeleria cristata) was commoner this year than on former 
occasions. Six-weeks grama (Bouteloua procumbens) appeared in 
quantity for the first time this year as an annual, principally out- 
side the fences. In general, the grasses did not look so well in 
1922 as on previous inspections, because the rains were late. The 
plot under total protection was becoming weedy from lack of grazing 
and trampling. | 
