14 BULLETIN 1227, U. S. DEPARTMENT OF AGRICULTURE 
rodents destroy 83 per cent of the blue-grama crop, the most impor- 
tant forage grass of the region. These experiments were made under 
conditions where the vegetation is at present maintaining itself; in 
many areas the prairie dogs destroy 100 per cent of the forage and 
have to move out themselves. Such extreme destruction favors the 
growth of unpalatable weeds, makes range recovery difficult, and 
opens the way for soil deterioration through erosion. The prairie- 
dog has not been shown to have a single beneficial food habit. 
Prairie dogs and cattle come into direct, and, in times of drought, 
deadly, competition. The evidence from these experiments indicates 
that these rodents do not eat anything that cattle do not and that 
the two eat the grasses in the same order of preference; sand 
dropseed (Sporobolus cryptandrus) is preferred to western wheat 
grass (Agropyron smithiz) and, when present with these, blue grama 
(Bouteloua gracilis) appears to be third in order of preference. The 
wheat grass apparently endures grazing by both prairie dogs and 
stock better than the dropseed. 
The impressive total of forage that may be destroyed by prairie 
dogs clearly indicates the constant losses suffered almost unconsciously 
by stockmen who utilize the open range in places where the rodents 
have not. been eliminated. The possible destruction of 80 per cent 
of the forage, or even of a far smaller proportion, is serious enough 
at any time, but in periods of drought it is likely to be calamitous, 
especially if in normal years the range is stocked to capacity. In 
some overgrazed areas the total eradication of praine dogs, as well 
as the reduction of the number of cattle per unit area, apparently 
will be necessary if the forage grasses are to continue in profitable 
quantity. 
The original equilibrium between prairie dogs and grass has been 
upset by man, in his grazing of cattle and other livestock and in his 
extermination ot coyotes and other predatory animals. As an offset 
the Biological Survey and its cooperators have undertaken system- 
atic campaigns for the destruction of injurious rodents. Extension 
of such campaigns is necessary if the prairie dog is to be eliminated 
as a strong factor in the destruction of forage upon vast areas of 
good stock ranges and in reducing profits of the hvestock industry 
there. 
