DAMAGE TO RANGE GRASSES BY THE ZUNI PRAIRIE DOG 9 
quadrats through the season did not yield reliable results, though 
check quadrats show that clipping reduces the forage and starves 
‘out the plants far more than does grazing by cattle. Trustworthy 
methods are now being worked out, however, which, to date, indicate 
that growth inhibition effects have been exaggerated. Nevertheless, 
allowing the 35 pounds of dry forage per day per cow, and estimat- 
ing that plants weakened by average rodent grazing produce only a 
50 per cent crop, the forage saved by extermination of rodents should 
suffice to support 37 head of cattle additional per section if forage 
of this type formed a continuous ground cover and if it were possible 
to utilize the forage when in a “eondition such as at the time of 
clipping. Of course, no extensive areas of western range afford such 
forage, but the figures are indicative of the quantitative reduction 
due to these rodents that may be expected in the best forage types, 
which are the ones most affected. A corresponding reduction may: 
be expected in more typical forage. 
THE WILLIAMS EXPERIMENT. 
THE AREA. 
The experimental tracts at Williams, Ariz., which were installed in 
the spring of 1918 shortly after the Coconino field test was maugu- 
rated, are situated near the Sweetwood Ranch, 34 miles north of the 
town, near the point at which the Red Lake Colony road crosses the 
Grand Canyon Railroad. They are in typical blue grama (Soute- 
lowa gracilis) forage areas on a tract of land which slopes gradually 
to the west. This forage type is one of the most widely distributed in 
the country, being found in abundance from north of the Canadian 
boundary south to the tableland of Mexico and from east of the one 
hundredth meridian westward to the Rocky Mountains and beyond, 
particularly across New Mexico and Arizona. Hence the results of 
art experiment should be especially suggestive and of broad appli- 
cability. 
A short distance from the experimental tracts is the lower edge 
of the juniper-pinyon formation, so that they are not far from the 
upper border of the grassland proper. Although this border is 
more favorable than the lower areas for grass maintenance, overgraz- 
ing has progressed so far that the grasses are more than half replaced 
already by various shrubs, as snakeweed (Gutzerrezia) and rabbit 
brush (CArysothamnus). The soil is composed of a fine silt pro- 
duced largely from the weathering and decomposition of basalt; 
it is a deep reddish-brown and very stony. The effects of washing 
are quite noticeable, the grass tufts often having half an inch or more 
of their roots exposed. This washing renders “the grasses unusually 
susceptible to damage by grazing. 
The Williams plots are smaller than those at Seligman and Coco- 
nino, yet large enough for the purposes of the experiment. The 
fenced part is 148 feet square and is divided by another fence, so 
that two plots each 148 by 74 feet have been inclosed. The north plot 
(planned for a prairie-dog inclosure) was first fenced with galvan- 
ized net wire, 1 inch mesh, 3 feet high, buried about 4 inches - under- 
ground and topped with a 6-inch strip of galvanized iron, strung 
