CANIDAE

Zorros gris y colorado

PHYLUM: Chordata

CLASE: Mammalia

SUBCLASE: Eutheria

ORDEN: Carnivora

SUPERFAMILIA: Caninae

FAMILIA: Canidae

CANIDAE

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The Canidae is a relatively samll but homogeneous family of generalized hunters, but it counts among its members such species as the wolf, fox, coyote and domestic dog. The wild dog family contains 35 different species, ranging in size from the tiny fennic to the little studied bush dogs of the Amazon Basin. Eight species of wild dog live in North America: red and grey wolves, coyote, and four species of fox. Canids are the most vocal of the carnivores, having a variety of barks, howls and whines. Those members of the family that hunt in packs can bring down large animals, but the solitary hunters usually live on small rodents, insects, birds and berries when hunting is poor.

The canids are specifically adapted to running, and to maintaining a trot or galloping gate for great distances. The skeletal structure of all members is remarkably consistent, largely a reflection of a lack of specialization in terms of lifestyle. The most notible feature of the canid skeleton, when compared with other carnivores, is the relative length of limbs compared to body size. Most canids stand tall and upright on elongate and semi-rigid legs which end in four well developed distinctive paws, having five toes on each forefoot and four, with nonretractable nails, on the hind foot. Canids actually walk on their toes (digitgrade), which are specially adapted as part of the foot structure, to withstand the shock of impact during running.

Canids possess an impressive set of dental equipment, consisting of 42 teeth, paired except for the molars, 20 on the upper and 22 on the lower jaws. Most noticable are the four canine teeth located at the front corners of the mouth, quite large although not particularly sharp when compared to the felids, which are utilized in holding prey and tearing large pieces of flesh from the carcuss. The lower canines are positioned so that they fit just infront of the corresponding canines in the upper jaw, leaving a small gap (diastema) allowing the canines to lock together when the mouth is shut. The incissors, slightly curved rearward and situated between the canines in the front of the mouth, are used to hold prey and tear at small pieces of food. The premolars and molars complete the canids dentition allowing for shearing, crushing and even a certain amount of grinding, although canids do not spend much time chewing, rather bolt food down in large chunks.

Unlike most domestic dogs, wild canids generally breed only once during the year, the period closely related to season so that the young are born in the spring or summer when food is abundant. Breeding behavior is conditioned by changes of daylight and temperature, resulting in an increase of aggression related to territorial claims, scent marking, and displays of dominance. After maiting over a period of several days, and a gestation period of between 52 and 80 days, a litter containing one to 16 blind pups are born. The young are unabe to hunt or to care for themselves for a period of time ranging from several weeks to several months. This extended dependency appears to strengthen the development of strong social or family ties typically observed in the canids.

The canids display many desireable traits that probably led to them being domesticated by humans. Both males and females are dedicated to raising the young, they eat a variety of foods, and prefer the company of others. Their tails are a visible indicator of mood, holding it erect when playing or well fed, wag it when seeking acceptance, and buckle it between the hind legs indicating fear or uncertainty.

Canids rely largely on a combination of hearing and eyesight to track their prey, with the relative significance of each sense depending on individual species and their lifestyle. Keen hearing is important in the case of the more social canids who communicate with eachother by a series of vocalizations including howling, yelping and growling. Interestingly, wild canids do not bark loudly like domestic dogs where domestication seems to have led to barking becoming more frequent, much louder and often challanging in nature. Direct long range communication between individuals is accomplished by a number of distinctive howling vocalizations. Howling helps group members to stay in touch during hunting forays, tends to unify a pack, proclaims territorial rights and once started by an individual member of the pack is rapidly picked up by all. Canid howling, although somewhat uniform to the human ear, distinguishes individual pack members with characteristic tones and assures that no territorial incursions or unnecessary conflicts develop with neighboring packs.

The hunting methods and patterns of social life permit three principal types of canids to be distinguished. Solitary: The fox, which hunts small prey, generally rodents, on its own. Solitary-social: A transitional type of canid, usually hunting and livein alone, but frequently associating in more or less temporary pairs. Social: The wolves live in packs which may be very large and employ a method of hunting which, for the killing of large prey, relies on close cooperation.

This family is represented by 14 genera and 34 species. Canids are widely distributed, occurring on all continents except Antarctica. It is the only member of the Order Carnivora that it represented in Australia (Canis familiaris dingo, the dingo; this species is thought to have been introduced by humans during prehistoric times). Fossil records of the Canidae date back to the Oligocene and the Miocene, making them one of the oldest extant groups of carnivores. Canids are probably an early offshoot of the caniform lineage (which includes mustelids, procyonids, ursids, phocids, otariids, and odobenids).

Primarily medium-sized flesh eaters, canids are more omnivorous than many carnivores, taking as food invertebrates, plant matter, and carrion as well as the prey they kill themselves. They are adapted more for endurance than for speed, and they catch prey by pursuit over long distances in relatively open terrain until the prey tires. Kills are made by grabbing for the nape of neck and tackling the prey to the ground. The neck grab is followed by a violent shake, which may dislocate the neck of the prey. Large prey may be immobilized by biting into the soft parts of the underbelly, often resulting in disembowelment and death from shock. Sense of smell is acute and appears to be critical to these animals, as is hearing, but sight is less developed. Canids have deep-chested bodies and a long muzzle.

The legs and feet of canids are moderately elongated, and their stance is digitigrade. Usually, five toes are found on the forefeet and four on the hindfeet (one genus, Lycaon, has only 4 toes on the forefeet). The metapodials are long but not fused. Unlike the Felidae, canids have non-retractile claws. This means that they are worn down by activity and are not the specialized weapons found in some other carnivores. All male canids have a well-developed baculum. The skulls of canids have an elongated facial region. An alisphenoid canal is present, and the paroccipital processes are long. Canids have nearly a full set of teeth with the following dental formula: 3/3, 1/1, 4/4, 1-2/2-3/3 = 38-42 (members of the genus Otocyon sometimes have additional molars). Canine teeth are large but unspecialized. Molars are of the crushing type. The carnassial pair is strongly built.

Some species (generally ones with larger body sizes) form packs with strict social hierarchies and mating systems. Hunting in packs allows canids to capture species much larger than themselves. In wolves, mating occurs only between the two dominant individuals in the pack. Pack-forming species, as well as less gregarious species such as foxes, are very territorial. Territory marking occurs in many species through repeated urination on objects on the periphery and within territories. Other scent glands are also important in the social behavior of these species; these include anal glands and glands on the dorsal surface of the tail near the base.

Many species are viewed as pests to humans, and populations of many species have been decimated. Coyotes and wolves are both persecuted by ranchers, who blame them for losses to sheep and cattle herds. Other species have been targeted as carriers of rabies (many of the foxes) and likewise have been the target of hunting. Some foxes are valued for their pelts, which have been used in the fashion industry. The domestic dog (C. lupus familiaris) has been domesticated for thousand of years and has been useful to humans in many ways, such as transport, guarding of livestock, and protection, although many are used primarily for companionship.

Zorros gris y colorado

Pseudalopex sp.

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Hay cuatro especies de zorros en Sudamérica  Pseudalopex sechurae: zona costera árida del sudoeste de Ecuador y noroeste del Perú. P. griseus: planicies y montañas bajas de Chile, oeste de Argentina y Patagonia, P. gymnocercus: praderas húmedas del sur de Brasil, Paraguay, norte de Argentina y Uruguay, P. culpaeus: Los Andes, región desde el Ecuador hasta la Patagonia

Se considera a Pseudalopex un subgénero de Canis y a las cuatro especies mencionadas se las suele incluir dentro del género Dusicyon, esta es la razón por la cual suelen aparecer bajo el nombre científico de Dusicyon. El largo de cabeza y cola va entre 600 a 1200 mm., el largo de la cola entre 300 a 50 mm. y su peso es entre 4 a 13 kgs. P. culpaeus es el más grande y P. sechurae el más pequeño.

El pelaje es usualmente pesado con un denso pelaje inferior y largos pelos de protección. Las partes más altas son usualmente grises con alguna coloración ocre. La cabeza, orejas y cuello son a menudo más rojizas. Las partes más bajas suelen ser más pálidas.. La cola es larga y muy peluda y la punta es negra. Los zorros de este género tienen algún parecido conel Coyote chico( Canis latrans). La dentición es propia de los zorros, los molares están bien desarrollados y los caninos son relativamente cortos.  

Ecología:  El hábitat incluye: deiertos arenosos (P. sechurae), praderas bajas y abiertas y bordes de bosques (P. griseus), pampas, cerros, desiertos y bosques abiertos (P. gymnocercus), tierras secas y áridas y áreas montañosas hasta los 450mts (P. culpaeus).  Su dieta Omnivora incluye: roedores, lagomorfos, aves, lagartijas, sapos, insectos, frutas y caña de azucar. P. culpaeus es más carnívoro que las otras especies y se sabe que come ovejas y liebre europa.

En el oeste de la Argentina, durante la primavera, parte de la población de P. culpaeus viaja entre 15 a 20 kms hacialas montañas más altas como respuesta del movimiento estacinal de liebres y ovejas. Su home range normal es de 4 kms. de diámetro. Comportamiento  Los dens están generalmente entre las rocas, bases de árboles, y arbustos bajos o madrigueras hechas por otros animales. Como viscachas y armadillos. La mayor actividad la tienen durante la noche pero algunos individuos ocasionalmente están activos durante el día.

Estas especies se congelan y quedan sin ningún tipo de movimiento frente a la presencia de seres humanos. La voz de Pseudalopex ha sido descripta como un aullido o una serie de ladridos. Se lo escucha principalmente de noche, especialmente durante la temporada de reprodución. P. culpaeus se aparea entre agosto y octubre y tiene sus crías entre octubre y diciembre (la primavera austral).Las hembra tienen un solo estro por año y el período de gestación es de 55 a 60 días. Pueden tener de 1 a 8 crías, con un promedio de 4 (5 en P. culpaeus P. culpaeus). El macho ayuda a proveer alimento a la familia. Después de 2 o 3 meses las crías comienzan a cazar con los padres.  Estos cánidos son cazados por la gente por que dicen que se come al ganado doméstico y por que su piel es muy codiciada. Por esto las poblaciones de zorro han declinado en algunas regiones.

¿Cómo verlos? En la Patagonia son muy comunes en los caminos y cerca de los lugares poblados. En la Península Valdés se suelen acercar mucho a las reservas, especialmente en Punta Cantor y Punta Norte, donde los guardafaunas los alimentan y protegen.

Referencias

Paradiso, J. L. 1975. Walker's Mammals of the World, Third Edition. Johns Hopkins University Press, Baltimore.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution, an Illustrated Guide. Facts of File Publications, New York. 259 pp.

Stains, H. J. 1984. Carnivores. Pp. 491-521 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vii+576 pp.

Wilson, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.

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