Silver Fox Development

Preparing a captive silver fox cub to cope with the different challenges they may face in a life living in a human environment is an important aspect of their care and welfare, one that has a continuing impact throughout their lives.

Fox behaviour is influenced by a wide variety of different factors such as; health, genetics, environment and individual learning experience. Nature and nurture have a complex relationship, and getting the balance right can sometimes be tricky. Understanding the natural behaviour of both wild and farmed foxes helps exotic pet keepers to gain a better understanding of the needs of their exotic pet. 

Some behaviour patterns only appear once an animals reaches a specific age or developmental stage. During these developmental periods certain behaviour's may be expected, as the nervous system and other structures complete their development. For example, young foxes begin teething at around 4 months of age. This alters their behaviour by driving them to chew on objects in order to relieve the discomfort they are experiencing with their teeth. 

Developmental milestones are behaviours or physical skills seen in infants as they grow and develop into adults. The milestones are different for each species and age range, however, there is a normal range in which an infant may reach each species-specific milestone, many of which can overlap.

Overview of Silver Fox Development
  • Gestational Development (pregnancy lasts around 49-58 days) - Good welfare and nutrition are required during this time to help ensure the development of healthy cubs. Silver foxes will have an average litter of around 4-6 cubs, however larger litters of up to 13 cubs have been recorded. 
  • Birth and Newborn Development (0-2 months) - Fox cubs must first learn to suckle. If they don't do so within the first day or so, they will not receive the maternal antibodies provided in their mother's "first milk" (colostrum) that they will need to survive. Feeding occurs every 3-4 hours and continues for 3 about weeks, when it begins to reduce. The cubs noses turn black at around 1 week of age, with their eyes and ears opening by around 2 weeks of age. By this point, they will have tripled their birth weight and are able to maintain their own body heat. At around 3 weeks of age the "critical period" for socialisation begins, just as the cubs begin moving around and exploring. By 4 weeks of age, the cubs will have established dominance hierarchies among their litter-mates and by 5 weeks their teeth and adult eye colour will have begun to develop, with their coats beginning to change texture and colour.
  • Weaning Period or "Puppy Phase" (2-5 months) - By 8 weeks, the socialisation window has closed and the fear response to novel and new stimuli has begun.  At this stage wild fox cubs will have to begun to eat prey items brought to them by their parents; starting with dead prey and then later moving on to injured prey, that allows them the ability to practice and refine the hunting skills they will need to survive. Learning how their bodies work through play and practice. At this time, squabbles with litter-mates are common and tension can be especially high around food. Their guard hairs and adult coats have developed and from around 16 weeks, they will begin to lose their baby teeth, developing a full set of adult teeth by around 20 weeks of age. 
  • Independence (5-10 months) - By 5 months of age fox cubs are now reaching adult proportions and are entering adolescence. Their adult teeth are now fully developed and they have begun to refine their hunting skills on live prey. Their physical and social development continues and they become more confident with their independence. Tensions within fox families is high at this time, behaviour that is thought to be a result of hormones changes. Ultimately, this behaviour facilitates dispersion of the cubs when they reach full maturity. It is a period known to fox keepers as the "October Crazies", as it usually begins around autumn and their behaviour can be a lot more challenging to handle. It is recommended foxes are provided their own enclosure by this point and that they are neutered, before they reach full sexual maturity.  
  • Maturity (10 -12 months) - By 10 months of age foxes have reached sexual maturity and ready to leave home and seek a mate. Hormone changes occur that drive changes in their coat and their behaviour. Both males and females undergo seasonal hormonal changes once a year (between late Dec and early Feb). On top of this, males testes are not fully developed until the following breeding, year after reaching sexual maturity. 

Growth And Development Of Fox Cubs

Foxes come into season and mate only once a year; with the exception of the experimentally domesticated foxes, which have been known to have 2 seasons per year (a result of their selective breeding for tame behaviour). The gestation period of the red fox ranges from 49-58 days and birth typically occurs in early spring with 4-6 cubs to a litter (silver foxes have been known to have litters twice as large).

After birth, the mother will clear the cub's nose and mouth and will begin to lick the cub clean, an act which also helps to stimulate the cubs breathing. The cubs first instinct is to suckle, and although born deaf and blind, they instinctively know their mother's scent and how to find their mothers teat. If they don't suckle in the first few hours after birth however, they will not receive the maternal antibodies provided in their mother's "first milk" (colostrum), which they need to survive. The cubs will remain reliant on their mothers milk for the first 6-7 weeks, requiring feeding every 2-4 hours under 2 weeks of age and every 4-6 hours until around 3-4 weeks of age. After this the frequency reduces to 3-4 feeds daily until weaning is complete, at around  6-7 weeks of age.  

Studies have shown that fox cubs have an average birth weight of around 100 grams (+/- 50 grams), are around 14-15 cm in body length and have an average tail length of around 7-8 cm. They are born with a fine and fluffy, dark grey coat (except in the case of leucistic foxes) and have a pink nose; which usually turns black over the space of around a week. Most cubs will also posses a white tail tip which is characteristic of the red fox and thought to be the result of both genetic and gestational processes. 

Their small size and short, sparse coats mean they are unable to maintain their body temperature during these first weeks, so the mother stays close and remains within the den during this time, keeping them warm and well fed until their size and coats can provide them with the ability to maintain their own body temperature (foxes will triple their birth rate within the first 10 days). During this time, the father will help feed the mother until she is able to spend time away from the cubs and hunt for herself again. 

The cubs will begin to open their eyes at around 2 weeks of age. Their eyes appear bule at first, the result of the Tyndell Effect, but by the age of 4-5 weeks they will have fully developed and changed to their adult colouration (which is usually amber in foxes). At about the same time, the first teeth will have begun to appear in the upper jaw, followed by teeth in the bottom jaw a few days later. It will take a further 3 weeks before they have developed a full set of 28 "milk teeth" (these are replaced by adult teeth by around 16-20 weeks of age). 

Foxes begin weaning at around 3-4 weeks of age, they complete the weaning process by 6-7 weeks of age, with an average weight of around 1-1.5 kg.

Foxes are capable of moving around and exploring from 2-3 weeks of age and will begin to leave the den for short periods from around 4-5 weeks of age, by which time their ears will have become erect, their muzzle will have begun to elongate and their coats will have begun to change. During this time fox cubs will fight viciously among themselves to establish dominance over resources in this new territory. At this age, they are eating partially digested food which is regurgitated by the parents, learning to develop the taste buds they will need for an adult diet.

By about 6 weeks of age their coat is similar to that of adults (though it is still quite fluffy in texture), and they are now eating dead and wounded prey which their parents bring them. By 8 weeks of age the cubs will begin developing shiny, long "guard hairs" in their coats, which will help keep them protected from the elements, and they will also have begun to develop the hunting skills they will need to survive, by making attempts to hunt insects and rodents that venture into the vicinity, as well as practicing their hunting skills through play with their siblings. 

From 3-4 months of age, the cubs have developed into their slender long legs, narrow chests and shiny coats, by 6-7 months of age they will have reached adult proportions (with an adult weight ranging from 3-12 kg), and are fully independent from their parents. From around 10 months of age, foxes begin to reach sexual maturity, (an ability that allows them to bare a litter by the age of 12 months), while many may leave home to find their own territory and start their own family, some foxes will remain within the mother's territory to help raise future litters. Foxes can live between 10-15 years in captivity, however, wild foxes have an average life expectancy of 4-5 years. 

Further Reading

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