diet in an almost endless number of qualitative 

 and quantitative combinations, which differ with 

 such environmental properties as emergencies, 

 season, year, and the general ecological character 

 of the specific area. At one extreme is the situa- 

 tion in which the feeding fox may pay little or no 

 attention to mice, rabbits, and other vertebrate prey 

 animals when it finds an abundance of insects and 

 fleshy fruits. At the other extreme, and of much 

 less frequent occurrence, is the situation in which 

 the fox may exert very severe pressure on vulner- 

 ably situated prey animals, as was witnessed in 

 the case of muskrats when a marsh went dry 

 (Errington & Scott 1945). Thus, environment plays 

 an important part in establishing the pattern of 

 the diet of the red fox. 



The diet of the red fox does not reflect pre- 

 cise, automatic adjustments to changes in popula- 

 tion levels of specific prey. For example, during 

 the spring and summer, when prey such as rabbits, 

 mice, and birds are found in increasing numbers, 

 the frequency of occurrence of these items in the 

 fox's diet declines where acceptable fleshy fruits 

 and insects are available. Thus, it seems apparent 

 that the relative availability of foods is important. 

 It seems obvious, too, from the fact tiiat prey pop- 

 ulations frequently show strong year-to-year popu- 

 lation trends that do not coincide with or follow 

 population trends of red foxes, that these foxes 

 surely do not normally limit prey numbers to an 

 important degree. 



Red fox predation and other forces of reduc- 

 tion do not control prey populations in the sense 

 of constantly limiting them to certain levels. Prey 

 populations frequently show year-to-year gains de- 

 spite the pressure of all the mortality factors in 

 their environment. Prey populations may also de- 

 cline at rates in excess of the rate which could 

 be induced by predation alone and may reach such 

 low levels that foxes find subsistence difficult. 

 The difficulty of finding food may be particularly 

 noticeable when there are cubs to feed at the dens. 



It is a mistake to claim or expect an increase 

 in numbers of prey species in response solely to 

 the reduction or elimination of red foxes. A large- 

 scale experiment with reduction of a fox popula- 

 tion as a means of increasing a pheasant popula- 

 tion in New York (Anonymous 1951:22) resulted in 

 the conclusion that "despite reducing the fox 

 population to a very low level, fox control on the 

 Seneca County area did not increase pheasant 

 abundance appreciably and certainly not to a de- 

 gree commensurate with the cost." 



Prey animals show differences in vulnerabil- 

 ity to predation by red foxes. Mice, especially 

 meadow mice, appear to be taken by red foxes with 

 considerable ease, and, while foxes do not control 

 these forms, they constitute a force for mouse re- 

 duction. Perhaps fox-caused losses to such de- 

 structive forms of prey may be thought of as a 

 compensation for losses among more desirable 

 forms of prey. 



Among the game species, bob-white quails 

 seem to be relatively secure against fox predation 

 (Scott & Klimstra 1955:94-6). Ring-necked pheas- 

 ants appear to be more vulnerable than bob- whites, 

 but pheasant losses do not reach alarming propor- 

 tions. Arnold (1952i:127) failed to find a cause 

 and effect relationship between an "irruption" in 

 the numbers of red foxes in Michigan in 1945 and 

 low numbers of pheasants in 1947 and concluded 

 "that foxes have no major influence on pheasant 

 populations and in all likelihood have little or no 

 effect on them." Rabbits are highly vulnerable to 

 capture by red foxes; however, no instance has 

 been observed by the writer where fox predation 

 has become so severe that it might not easily have 

 been replaced by losses of another kind if foxes 

 had been eliminated. It may prove enlightening to 

 think of predation by red foxes as an age-old ac- 

 tivity to which nature has adjusted long ago. If 

 prey populations were not well endowed with the 

 means of survival and if red foxes lived up to 

 their reputations as deadly predators, it seems 

 reasonable to believe that these foxes would have 

 eliminated their means of subsistence and them- 

 selves generations ago. 



Foxes unquestionably prey upon vulnerably 

 situated poultry, small pigs, and lambs. It seems 

 certain that only the poultry losses reach signif- 

 icant proportions. Losses of poultry to foxes, 

 however, result largely from failure of poultrymen 

 to follow recommended poultry husbandry prac- 

 tices. The restriction of laying flocks and broilers 

 to pens and houses is a method of improving on 

 egg and meat production, and even poultrymen who 

 doubt that production is raised enough to justify 

 the initial cost of this practice must admit that it 

 is an effective means of eliminating losses to 

 foxes and other predators. Important losses occur 

 among pullets at times because leaving them on 

 unfenced range until they reach laying age con- 

 stitutes approved husbandry. However, even here 

 something may be done to minimize the probability 

 of loss. If such birds are not released from their 

 roosting pens until after the sun is well up and 

 are securely penned by the time the sun goes 



