1936] MAMMALS OF OREGON 105 



pasture land has been reduced in its carrying capacity for stock 10 

 to 20 percent by the rabbits. 



In the Malheur Valley in August of 1920 on 1 square yard of salt 

 grass meadow 403 rabbit pellets were picked up; most of the sum- 

 mer's accumulation. These were mostly old and dried out until very 

 light, but they weighed 46 g, almost 2 ounces. One hundred fresh 

 pellets that had not been rained on weighed 20 g. These are rounded, 

 slightly flattened bodies about one-half inch in greatest diameter, 

 entirely the undigested particles of plant tissue, mainly the hard bits 

 of grass stems. At 2 ounces to a square yard there would be 605 

 pounds, or over a quarter of a ton of dry pellets to an acre. Just 

 how much green grass this would represent is at present only a con- 

 jecture, but certainly twice the weight of the pellets and probably 

 more. They must at least represent more than their weight in cured 

 hay. In most of the valley bottoms they covered the ground in 

 great abundance, often making a complete layer over the surface 

 where the rabbits had been feeding. Around the bases of the grease- 

 bushes they were especially numerous, but they had generally been 

 washed off the bare spots. The amount of vegetation represented by 

 these pellets is enormous. Various estimates of the forage taken by 

 the rabbits range from 20 to 90 percent, but these estimates are for 

 local areas. To be sure they return to the soil some slight value as 

 fertilizer, but nothing to compare with the heavy loss of vegetation. 



In fields of alfalfa and grain the depredations of these rabbits 

 are often serious, and small fields in a rabbit-infested valley are 

 sometimes entirely destroyed. Raising crops without rabbitproof 

 fences has been practically abandoned in many of the valleys. Even 

 so-called " rabbitproof fences " are not a complete protection, as some 

 of the rabbits almost invariably find their way under or over these 

 fences, so insistent are they on getting at the choice food supply. 

 A supplementary protection of corral traps in the corners of the 

 fields has in some cases proved effective in capturing the rabbits 

 after they obtain entrance into the fields. 



Young orchards of almost any kind of fruit trees are sure to 

 be injured, and in some cases completely destroyed, unless protected 

 by rabbitproof fences or by wrapping each tree with paper, wood 

 veneer, or tin as high as the rabbits can reach. 



Natural enemies. Babbits are extensively preyed upon by coyotes, 

 foxes, bobcats, badgers, skunks, eagles, hawks, owls, and ravens. 

 Many animals that cannot catch them in a fair race, pounce upon 

 them while hiding in their forms or pick them up when diseased 

 and unable to escape. In the Malheur Valley ravens kill and eat 

 a great many, but only in the last stages of their diseased condition. 



Diseases. During August 1920 at Malheur Lake the rabbits were 

 dying off rapidly from various diseases, almost as many dead as alive 

 being seen along the trails, and many sick individuals so far gone 

 as to be so stupid that they could be approached and picked up 

 by the ears without attempting to escape. Many were watched in 

 their last death struggles and then examined for symptoms. Most 

 of these were heavily infested with Cutere'bra larvae, and some had 

 both eyes destroyed or so crowded with these parasites as to be 

 unable to see. The writer counted as many as seven large grubs 

 in the head of one rabbit, and they were often scattered over the 



