Methods and Materials My goal was to locate five urban den sites and five rural den sites. Den sites were located by direct investigation of sites recommended by personal communications with residents of the metropolitan area and surrounding rural areas. To pinpoint den sites and areas frequented by foxes, two field assistants and I searched for signs of foxes such as tracks, scat, and prey remains as described in Henry (1993). The classification of den sites as "urban" is somewhat subjective. Dickman and Doncaster (1987) arbitrarily designated any site within city limits as urban; Harris and Rayner (1986) used a much more restrictive definition that excluded corridors of natural habitat such as a river valley. In Minneapolis-St. Paul, there is a great variety of urbanization within the city limits; the central downtown areas have been in existence for over 100 years, but certain areas within the city limits are much less disturbed than some more remote suburbs. In addition, there is an extensive park system in the city. For the purposes of this study, a den site was considered part of an urban habitat if it was within a quarter mile of at least five occupied buildings and one paved road. I planned to make observations weekly at each site for 10 weeks, from early May until late July. This covers the time period from the first appearance of the cubs outside the den at about 4-5 weeks of age (Storm et al., 1976; Henry, 1993) until the cubs are 14-15 weeks old. The adults no longer provide food for the cubs after this time, although the cubs remain in the territory of their parents for another 3 months (Storm et al., 1976). Observation periods were 4 hours long. Prior to the study, I planned to observe one urban den and one rural den twice each for 24 consecutive hours. Based on these observations, the observation periods for the study would be set to cover the widest possible range of fox activity and interactions. Observations were made by a single observer from a location that provided a clear view of the den, but was not close enough to alarm the foxes. Use of a blind was considered, but Henry (1993) asserted that because foxes have a sensitive sense of smell, a blind is not very effective in hiding a human observer. He found that it is more important to determine the distance at which a human will be tolerated from each fox or group of foxes and to remain at that distance. The distance differs for each fox and must be determined carefully, starting at a large distance and gradually moving forward over several hours. Data recorded during each observation were to be: maximum number of cubs seen at once, number of times that adults return with food for the cubs, the type of food brought back by the adults for the cubs, any food the cubs take for themselves (not provided by the adults), all intraspecific and interspecific interactions, and all behavior toward man-made structures. All data collection was to be made using the cubs as the focal group for observations and also recording all occurrences of the above behavior in the adults, as described in Altmann (1974). The data for the urban sites were to be compared to the data for the non-urban sites, and the differences tested for significance by the Chi-squared test. Results In seven weeks of searching the Minneapolis-St. Paul area, my field assistants and I were only able to locate five fox dens, two urban and three rural. We found many signs of fox, such as scat, trails, and prey remains, but were unable to trace these signs to a den in most cases. Three possible reasons can explain our inability to locate many urban fox dens. The first is that we were all inexperienced at tracking foxes and finding their dens. The second is that urban foxes must take extra care to conceal their dens, because of the high risk of encounters with humans and dogs. The third is that because of the variety of habitats available in an urban area, urban fox dens look different than rural fox dens. Although I am certain that inexperience was a contributing factor, I believe that extra concealment of urban fox dens was also important. My assistants and I spent most of our search time in urban areas, where we did not find any dens that had not been pointed out to us. In rural areas, by contrast, we were shown the locations of two dens, and found a third one in only a couple hours upon further investigation of the area. The biggest problem in rural areas was that many more species inhabit underground dens in those areas than inhabit dens in urban areas, so we could not always be sure that a den was inhabited by foxes. Despite having found only half the number of dens I had hoped for, I prepared to carry out the study on the dens I had located. My assistants began observations on the rural dens, which were located in Maple Plain, Minnesota (about 45 minutes west of Minneapolis). I began observations on the urban dens, both located on land owned by the U. S. Army, formerly used for the Twin Cities Army Ammunition Plant (commonly called the Arsenal). In our initial observations, neither my assistants nor myself saw any foxes at the dens, although we had seen fresh sign there recently, and in one case we had seen two fox cubs playing. I ended my observation of one of the den sites after seeing a striped skunk (Mephitis mephitis) enter the den; that was the only wild mammal I saw in several observations of the urban den sites. We concluded that the foxes had abandoned the dens. Foxes rearing cubs often move the cubs to different dens, but in these cases abandonment might have been precipitated by the disturbance my assistants and I caused while investigating the den sites. By the time we discovered that none of the sites we had located were still inhabited, it was too late to locate more den sites. By the middle of June, most fox cubs in the Minneapolis- St. Paul area are between six and twelve weeks old, so even in the best case, I would be starting my observations in the middle of the period I was most interested in. I decided to review the literature on urban foxes again, and see where the observations I did make fit into other studies. I also spent some time during the summer working with a woman who rehabilitates injured foxes and releases them to the wild. Many of the foxes she receives for treatment come from the Minneapolis-St. Paul area, so I was able to get a little more data from observing some of her patients. The most interesting observation I made at this location was of a young cub, about six to eight weeks old on 5 August. She must therefore have been born in early June, which is very late in the year relative to parturition dates listed in the literature. I will discuss this and other observations I made in the rest of this paper. First, I will discuss the general life history of red foxes as described in the literature, noting differences between urban and rural foxes. Next, I will examine in more detail the aspects of fox life history that differ most between urban and rural areas: diet, home ranges and dens (which are partially determined by diet), and mortality and life expectancy. Last, I will examine the scope of fox-human interactions in urban areas.