Life History
	Reproduction of red foxes is described by Storm et al. 
(1976) and Henry (1993).  The gestation period and time of 
weaning are constant over different populations.  Timing of 
mating and birth, by contrast, may vary geographically and is 
even subject to variation within a small area.  Dispersal of 
juvenile foxes takes place every year, and because of variation 
in the time of birth, one might suspect that the time at which 
dispersal begins would also reflect strong geographic variation.  
In fact, the time of year at which dispersal is initiated seemed 
to be constant over all the populations studied.  These and other 
aspects of the life of an urban fox over a single year are 
detailed in the following paragraphs.
	Courtship for foxes begins in mid to late December.  
Spermatogenesis begins in October (even in first-year males), and 
continues through March (Storm et al., 1976; Henry, 1993).  When 
courtship starts, previously solitary foxes travel in pairs, or 
sometimes in groups of three.  Mating usually takes place in 
January and February, although it may be earlier in more southern 
areas and later in northern areas.  
	In the city of Minneapolis, I observed fox cubs that were 
about six weeks old as early as 7 May, and as late as 5 August.  
Therefore, there is at least a three-month window during which 
mating can take place and result in production of viable 
offspring.  Given a gestation period of 52-53 days, which is 
consistent through the literature for all fox populations, these 
observations indicate that mating takes place in the Minneapolis 
area between late January and late April, and possibly earlier or 
later.
	Although Storm et al. (1976) claimed that breeding can take 
place as late as April, they noted that 94% of the rural foxes 
they studied bred between mid-December and mid-February, with a 
peak during the third week of January.  Only 1% of their sample 
had bred after mid-February.  Harris and Smith (1987) reported 
that for foxes in both London and Bristol the peak birth period 
was March, indicating a peak breeding period in January.  They 
noted that in those cities matings can also take place in early 
December (about 10%), or after the first week of February (about 
25%).
	No study has been conducted directly comparing the lengths 
of breeding seasons in urban areas as opposed to nearby rural 
areas, but it seems that the breeding season may be extended 
somewhat in urban areas.  If this is true, the most likely 
explanation is the protection an urban environment provides from 
the extremes of weather.  Most importantly, food is not scarce in 
urban areas in winter, as it often is in rural areas (Harris, 
1977; Storm et al., 1976).
	The availability of food also affects the composition of fox 
family groups (von Schantz, 1984; Zabel and Taggart, 1989).  A 
typical family group consists of the dog fox and vixen, plus up 
to four females that may or may not breed.  Macdonald (1979) 
referred to these females as "helpers," and observed a definite 
dominance hierarchy in the family group, wherein the "helpers" 
were subordinate to the breeding female.  Harris (1981a) also 
noted that some family groups in Bristol produced more than one 
litter of cubs in a given year, indicating that some of the 
"helpers" may also breed under certain conditions, presumably 
when resources are plentiful.  
	Space is an important resource for foxes.  Each family needs 
several safe den sites in which to raise their cubs in addition 
to safe resting sites outside of the den.  Den space seems to be 
readily available for urban and rural foxes alike.  Foxes 
maintain territories, and it is common for them to have several 
different dens within their territory.  Prior to parturition, the 
mated pair selects a den, called the natal den, in which to bear 
the cubs.  This den is usually larger than other available dens, 
and has several exits (Henry, 1993).  The other dens can be as 
simple as a single entrance leading to a hole where the foxes can 
take shelter.  In urban areas, a great variety of den sites is 
available to foxes, but places to rest during the day are 
scarcer.  Denning, home ranges, and daytime resting sites are 
covered in a separate section.
	The natal den must be safe, because the fox family is most 
vulnerable to predators during the first two weeks after 
parturition.  Fox cubs are blind and helpless for about ten days 
after birth.  The vixen stays with them constantly for up to two 
weeks (longer in colder climates than in warmer climates), during 
which time she is dependent on the dog fox and any "helpers" for 
food.  After this time, she may leave to hunt for herself, but 
will return regularly to nurse the cubs.
	The parents may first move the cubs to an alternate den when 
they are about two weeks old.  The cubs usually are moved at 
least once, and may be moved several times during their first 
summer.  For example, all the dens I located were abandoned in 
late spring.  In two of the rural dens, human disturbance might 
have led to the abandonment, but humans frequented the immediate 
areas of the urban dens at least every other day, so it is 
unlikely that human disturbance was the only cause of abandonment 
of the urban dens.  This suggests that urban foxes, like rural 
foxes, move frequently between dens.  Movement may help protect 
the fox family from humans and other predators when the cubs are 
most vulnerable.
	When the cubs are about five weeks old, they begin to 
venture outside the den.  Weaning takes place at this time, so 
the parents bring back prey for the cubs to eat.  Later in the 
summer the cubs learn to hunt for themselves, and their parents 
will provide less food and spend less time at the den.  The cubs 
range farther from the den as they grow older, hunting for 
themselves but remaining in the territory of their parents.
	October is the month during which dispersal of foxes is most 
likely to begin.  Not all cubs disperse, and not all of those 
that disperse leave in their first year.  In a study of 
dispersal, Harris (1988) found that only 3.5% of female cubs and 
10.8% of male cubs dispersed before 1 October.  By the end of 
December, Harris (1988) found that 32.5% of tagged females and 
58.5% of tagged males had dispersed.  Most of the animals that 
dispersed did so by the end of their second year, the final 
proportions being 37.8% for females and 75.8% for males.  This 
corresponds closely with data gathered by Storm et al. (1976) on 
rural foxes, which indicated that most of them also disperse in 
October.  The proportion of foxes dispersing in the rural 
population they studied was somewhat higher, reaching 58% for 
females and 96% for males.
	Population density is probably the most important factor 
affecting dispersal.  In urban areas, for example, Harris (1988) 
found that male cubs from large litters were more likely to 
disperse than male cubs from small litters.  He also found that 
animals from areas of low fox density (indicating poor fox 
habitat) dispersed farther than animals from areas of high or 
medium fox density.  
	Another factor affecting dispersal is the food supply in the 
territory.  Cubs might remain in their natal territory longer in 
urban areas, where food is plentiful, than in rural areas.  
However, the sample sizes and geographical areas of the studies 
by Harris (1988) and Storm et al. (1976) are too small to draw a 
definite conclusion.
	Once the cubs have dispersed, the adults and remaining cubs 
stay on the same territory, but continue to hunt alone.  They may 
rest with other foxes in areas where resting habitats are 
limited, but do not associate in regular pairs until courtship 
begins again in December.