Fox (Canidae family)

Foxes are small to medium-sized omnivorous mammals belonging to several genera of the Canidae family. Foxes have a flat skull, vertical triangular ears, a slightly pointed snout and a long, thick tail.

Twelve species belong to the monophyletic group of "true foxes" of the genus Vulpes. Approximately 25 other current or extinct species are part of the paraphyletic group of South American foxes or the peripheral group, which consists of the bat fox, the grey fox and the island fox.

Foxes live on all continents except Antarctica. By far the most common and widespread fox species is the red fox (Vulpes vulpes) with about 47 recognised subspecies. The global distribution of the foxes, together with their widespread reputation for cunning, have contributed to their prominence in popular culture and folklore in many societies around the world. Fox hunting with dog packs, long an established activity in Europe, especially in the British Isles, has been exported by European settlers to various parts of the New World.

Phylogenetic relations

Comparative illustration of skulls of a real fox (left) and a grey fox (right), with different temporal ridges and subangular lobes indicated

Within Canidae, DNA analysis results show several phylogenetic divisions:

• Fox-like dogs, which include the fox (Vulpes velox), red fox (Vulpes vulpes), cable fox (Vulpes chama), arctic fox (Vulpes lagopus), and fenugreek (Vulpes zerda).
• Wolf-like dogs (genus Canis, Cuon and Lycaon) include the dog (Canis lupus familiaris), grey wolf (Canis lupus), red wolf (Canis rufus), eastern wolf (Canis lycaon), coyote (Canis latrans), Golden Jackal (Canis aureus), Wolf-eye (Canis simensis), Black Jackal (Canis mesomelas), Striped Jackal (Canis adustus), Wild Asian Dog (Cuon alpinus), and Mabeco (Lycaon pictus).
• South American dogs, including the bush dog (Speothos venaticus), field fox (Lycalopex uetulus), bush dog (Cerdocyon thous) and maned wolf (Chrysocyon brachyurus).
• Several monotypic taxons, including the bat fox (Otocyon megalotis), grey fox (Urocyon cinereoargenteus), and raccoon dog (Nyctereutes procyonoides).

Biology

General morphology

Foxes are generally smaller than some other members of the Canidae family, such as wolves and jackals, although they may be larger than some within the family, such as raccoons. In the largest species, the red fox, males weigh on average 4.1-8.7 kg, while the smallest species, the fenugreek, weighs only 0.7-1.6 kg. Characteristics of foxes generally include a triangular face, pointed ears, an elongated rostrum and a thick tail. The foxes are digested; they walk on tiptoe. Unlike most members of the Canidae family, foxes have partially retractable claws. Foxes' vibes, or whiskers, are black. The moustaches on the snout, the vibrissas, average 100-110 mm in length, while the whiskers on all other places on the head are shorter. Whiskers (carpal vibrissas) are also on the forelimbs and are 40 mm long, pointing down and back. Other physical characteristics vary according to habitat and adaptive significance.

Fox species differ in colour, length and hair density. Coat colours vary from pearly white to black and white to black speckled white or grey at the bottom. Fenecos (and other species of foxes adapted to desert life, such as dwarf foxes), for example, have large ears and short fur to help keep the body cool. Arctic foxes, on the other hand, have small ears and short limbs as well as thick, insulating fur, which helps to keep the body warm. Red foxes have a typically red hair, the tail usually ends with a white tail patch. The colour and texture of a fox's coat can vary due to the change in seasons; fox skins are richer and denser in the colder months and lighter in the warmer months. To get rid of the dense winter coat, foxes change coats once a year around April; the process begins on the feet, goes up the legs and then along the back. The colour of the coat may also change as the individual ages.

Dentition

A fox's dentition, like all other dogs, is I 3/3, C 1/1, PM 4/4, M 3/2 = 42. (Bat foxes have six extra molars, totaling 48 teeth). Foxes have pronounced pairs of scavenger teeth, which is characteristic of a carnivore. These pairs consist of the upper premolar and the lower first molar, and work together to shear hard materials like flesh. Foxes' canines are pronounced, also characteristic of a carnivore, and are excellent for grasping prey.

Behaviour

Arctic foxes wrapped in snow

In nature, the typical life expectancy of a fox is one to three years, although individuals can live up to ten years. Unlike many dogs, foxes are not always pack animals. They usually live in small family groups, but some (such as arctic foxes) are solitary.

Foxes are omnivorous. Their diet is composed mainly of invertebrates, such as insects, and small vertebrates, such as reptiles and birds. They can also eat eggs and vegetation. Many species are general predators, but some (such as the bush dog) have more specialized diets. Most fox species consume about 1 kg of food every day. Foxes store excess food by burying it for later consumption, usually under the leaves, snow or soil. During hunting, foxes tend to use a specific attack technique, so they squat to camouflage themselves in the ground and then use their hind legs to jump with great force and land on the chosen prey. Using their pronounced canine teeth, they can grab the neck of the prey and shake it until it is dead or can be easily gutted.

The grey fox is one of only two dog species known to climb trees regularly; the other is the raccoon dog.

Sexual characteristics

The male fox's scrotum is held close to the body with the testicles inside, even after they descend. Like other canines, the male fox has a crosier, or penis bone. The testicles of the red fox are smaller than those of the arctic fox. The formation of sperm in red foxes starts in August-September with the testicles reaching their highest weight in December-February.

Female foxes are in heat for one to six days, making their reproductive cycle last twelve months. As with other canines, the ova are eliminated during oestrus without the need for stimulation of copulation. Once the egg is fertilised, the fox enters a gestation period which can last from 52 to 53 days. Foxes tend to have an average litter size of four to five, with a success rate of 80 percent in getting pregnant. Litter size can vary greatly according to species and environment - the arctic fox, for example, can have up to eleven cubs.

Vocalization

The fox's vocal repertoire is vast:

• Crying - Done right after birth. It occurs at a high rate when the puppies are hungry and when the body temperature is low. Crying stimulates the mother to take care of her children; it also stimulates the male fox to take care of his mate and the cubs.
• Ganido - Done about 19 days later. The crying of the puppies turns into childish barking, ganido, which occurs strongly during play.
• Explosive call - At the age of about one month, the puppies can emit an explosive call that has the objective of threatening intruders or other puppies; an acute howl.
• Combative call - In adults, the explosive call becomes an open-mouthed combative call during any conflict; a sharper bark.
• Rosnado - An indication of an adult fox to its young to feed or to go to the adult's place.
• Barking - Adult foxes warn against intruders and in barking defense.

In the case of domesticated foxes, groaning seems to remain in adult individuals as a sign of excitement and submission in the presence of their owners.

Relations with humans

Foxes are often considered pests or annoying creatures for their opportunistic attacks on domestic birds and other small animals. Fox attacks on humans are not common.

Many foxes adapt well to human environments, with several species classified as "urban resident carnivores" for their ability to sustain populations entirely within urban boundaries. Foxes in urban areas may live longer and may have smaller brood sizes than foxes in non-urban areas. Urban foxes are ubiquitous in Europe, where they display altered behaviours compared to non-urban foxes, including increased population density, smaller territory and fodder packs. Foxes have been introduced in various locations, with varying effects on indigenous flora and fauna.

In some countries foxes are the main predators of rabbits and chickens. The population oscillations of these two species were the first non-linear oscillations studied and led to the derivation of the Lotka-Volterra Equation.

Fox hunting

Fox hunting originated in the United Kingdom in the 16th century. Hunting with dogs is now banned in the UK, although hunting without dogs is still allowed. Red foxes were introduced to Australia in the early 19th century for sporting purposes and have since spread throughout much of the country. They have caused population decline among many native species and prey on animals, especially new lambs. Fox hunting is practised as recreation in several other countries including Canada, France, Ireland, Italy, Russia, the United States and Australia. In Portugal, fox hunting is allowed (Decree-Law No. 202/2004), but there has been popular protest and initiatives for its abolition.

Domestication

There are many records of red-domestic foxes and others, but rarely of continuous domestication. A recent and notable exception is the silver fox, which has resulted in visible and behavioural changes, and is a case study of modelling an animal population according to the needs of human domestication. The current group of silver domestic foxes is the result of almost 50 years of domestication in the Soviet Union and Russia. This selective breeding has resulted in physical and behavioural characteristics that often appear in domestic cats, dogs and other animals, such as pigmentation changes, fallen ears and curly tails. Notably, the new foxes have become more domesticated, allowing themselves to be caressed, whining to attract attention and sniffing and licking their caretakers.

Urban foxes

Foxes are among the relatively few mammals that have been able to adapt to a certain degree to live in urban (mainly suburban) human environments. Their omnivorous diet allows them to survive on wasted food that is discarded, and their nervous and often nocturnal nature means that they are often able to avoid detection, despite their larger size. Urban foxes, however, have been identified as threats to cats and small dogs and for this reason there is often pressure to exclude them from these environments.

In culture

The fox appears in many cultures, usually in folklore and mythology. However, there are small variations in their representations. In Western and Persian folklore, foxes are symbols of cunning and naughtiness - a reputation derived especially from their ability to escape from hunters. This is usually represented as a character that possesses these characteristics. These traits are used in a wide variety of characters, making them a nuisance to the story, a misunderstood hero or a crooked villain. In Asian mythology, foxes are represented as a familiar spirit, possessing magical powers. Foxes are also often portrayed as cross-dressers, usually deceiving other people with the ability to disguise themselves as an attractive woman. However, there are other representations of foxes as mystical and sacred creatures that can cause admiration or ruin. The nine-tailed fox appears in Chinese folklore, literature and mythology, in which, depending on the tale, they can represent a good or a bad omen. The theme was eventually introduced from Chinese culture to Japanese (Kitsune) and Korean culture.

The constellation Vulpecula represents a fox.

The fox is also the official mascot of the Cruzeiro Esporte Clube, created by the charlotte and professor Fernando Pieruccetti, also known as Mangabeira, in 1945. Characteristics such as the cunning and speed of the animal were attributed at the time to the then president of the celestial club, Mario Grosso, known for his cleverness in player negotiations.