ARTIODACTYLA

Ciervos, camellos, guanacos y otros

Artiodactyla

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The artiodactyls are a large and diverse group of mammals, containing around 220 living species placed in 10 families. The majority live in relatively open habitats, such as plains and savannas, but others dwell in forests, and one group is semiaquatic. Within the order can be found some of the fastest-running mammals, but the Artiodactyla also includes relatively slow and cumbersome species such as pigs and hippos.

Artiodactyls are paraxonic, meaning that the plane of symmetry of each foot passes between the third and fourth digits. In many species the number of digits is reduced. The third and fourth, however, remain large and bear weight in all. This pattern has earned them their name, Artiodactyla, which means "even-toed." Artiodactyls stand in contrast to the "odd-toed ungulates," the Perissodactyla, in which the plane of symmetry runs down the third toe. The most extreme toe reduction seen in any artiodactyls (living or extinct) is in forms such as antelope and deer, which have just two functional (weight-bearing) digits on each foot. In such forms the third and fourth metapodials fuse, partially or completely, to form a single bone called a cannon bone. Further, in the hind limb of these species, the bones of the ankle are reduced in number, and the astragalus becomes the main weight-bearing bone. These traits are probably adaptations for running fast and efficiently.

Artiodactyls tend to share a number of cranial and dental characteristics, but the group is so diverse that there are exceptions to each trait. The anterior part of the skull (in front of the orbits) tends to be long and narrow. Horns or antlers are often present, usually on the frontals, which are usually larger than the parietals. All artiodactyls have a postorbital bar or process. The number of teeth is variable, but in many species it is smaller than the number found in perissodactyls. A diastema usually separates anterior and posterior teeth, especially in the lower jaw. Cheek teeth are bunodont in some forms, but more commonly selenodont. The premolars tend to be relatively small and not fully molariform.

Most artiodactyls have modified stomachs, the extreme case being that of groups such as antelope and deer, which have distinctive, four-chambered stomachs. This arrangement appears to be an adaptation that allows members of these groups to make use of microorganisms to decompose cellulose into digestible components. Cellulose is an important constituent of plant tissue that most mammals cannot digest.

Artiodactyls are native to all continents except Australia and Antartica. The group contains a number of domesticated species. The fossil record of artiodactyls is ancient, going back at least to the earliest Eocene. The group expanded greatly and its members took on more-or-less modern form in the Miocene.

Artiodactyls are usually divided into several suborders. The Suiformes include the suids, tayassuids and hippos, plus a number of extinct families. These animals do not ruminate (chew their cud), and their stomachs may be simple and one-chambered or have up to three chambers. Their feet are usually 4-toed (but at least slightly paraxonic). They have bunodont cheek teeth, and their canines are present and tusk-like. The suborder Tylopoda contains a single living family, the Camelidae. Modern tylopods have a 3-chambered, ruminating stomach. Their third and fourth metapodials are fused near the body but separate distally, forming a Y-shaped cannon bone. The navicular and cuboid bones of the ankle are not fused, a primitive condition that separates tylopods from the third suborder the Ruminantia. This last suborder includes the families Tragulidae, Giraffidae, Cervidae, Moschidae, Antilocapridae, and Bovidae (plus a number of extinct groups). In addition to fused naviculars and cuboids, it is characterized by a series of traits including missing upper incisors, often (but not always) reduced or absent upper canines, selenodont cheek teeth, a 3 or 4-chambered stomach, and third and fourth metapodials usually partially or completely fused. 

Family Suidae: Pigs and hogs
Family Tayassuidae: Peccaries
Family Hippopotamidae: Hippopotamus
Family Camelidae: Camels, llamas, alpacas, vicugnas, guanacos.
Family Tragulidae: Mouse deer, chevrotain
Family Giraffidae: Giraffes and okapis
Family Moschidae: Musk deer
Family Cervidae: Deer
Family Antilocapridae: Pronghorn antelope
Family Bovidae:  Gazelles, African antelope, buffalo, mountain goats, cattle, sheep, and goats

Family Camelidae

Camels, llamas, alpacas, vicugnas, guanacos

Camelids are all large. The South American forms range in weight from 35 kg to almost 100 kg. Old World camels, however, are much larger, weighing 450 to 650 kg. Camelid bodies vary from slender to stocky, but all have long, gracile necks; a small head; and long, slender legs. The upper lip is deeply and distinctively cleft. Their toes are splayed, and camelids are the only plantigrade or fully digitigrade ungulates (camels are sometimes grouped with several extinct families in the infraorder Tylopoda, which means "padded foot").

The skulls of camelids have an elongated rostrum, a well developed sagittal crest, and a complete postorobital bar. They lack horns or antlers. The cheek teeth are selenodont. Upper incisors are present; young have 3 on each side, but adults have only one. The spatulate lower incisors project forward. The canines, which are present in both upper and lower jaws, are medium-sized and hooked. The dental formula for (adult) Old World camels is 1/3, 1/1, 3/1-2, 3/3 = 32-34; that for New World camels is 1/3, 1/1, 2/1, 3/3 = 30.

The postcranial skeleton is notable mostly because of the condition of the legs. The 3rd and 4th metapodials fuse to form a cannon bone, as in other paraxonic ungulates, but the fusion is complete only proximally. At the end away from the body, the metapodials separate and splay wide apart. The phalanges of these two toes are also distinctive. The first two of each digit are flattened and expanded, while the last is reduced and bears a nail, not a hoof. The middle (second) phalanges are imbedded in the broad pad that makes up the sole of the foot. The ulna and fibula are much reduced, present mainly as a splint on the ulna or tibia. Camelids have a complex 3-chambered, ruminating stomach.

Wild camelids generally live in groups. These are polygynous, each containing a harem male and his females. Bachelor males also form herds in some species. Males fight for dominance by biting and "neck dominance." All camelids are herbivorous and feed primarily but not exclusively on grasses. They are generally found in arid or semi-arid areas, and the much-studied Old World camels have a remarkable ability to conserve water.

The family Camelidae ranges back in time to the upper Eocene. It is first known from North America. Curiously, camelid feet were nearly unguligrade and probably hoofed by the Oligocene and early Miocene. The cannon bone was completely or nearly completely fused. During the Miocene and Pliocene, the ends of the cannon bones separated, and camelids returned to the digitigrade stance of their ancestors. The splayed toes of camelids give them additional surface area for supporting their weight on soft substrates like sand. Camelids probably spread to the Old World and South America during periods of low sea level during the Pliocene and Pleistocene, when land bridges connected those continents to North America.

Llama

Lama glama

Southern Peru, Bolivia, Northern Argentina.  Mass: 130 to 155 kg Llamas feet are slender and their limbs are long. They have long, dense fine wool on their bodies. The hair on their head, neck, and limbs is shorter than on their torso. Llamas have remarkable variety in their body sizes and shapes. The larger animals are more prevelant because of their use as "beasts of burden." Body length ranges from 153-200 cm, shoulder height from 100-125 cm, and tail length from 22-25 cm. The coloring of their fur is also variable, ranging from all white, to brown, yellow, blue and black, and sometimes with checks and spots.

Natural History Food Habits Llamas are herbivorous, feeding on many kinds of grasses and leaves. Reproduction Llamas reach sexual maturity at about 12-24 months. Females give birth every other year. Mating occurs in August and September. The gestation period is 348-368 days. Llamas produce one offspring at a time (rarely two). The weight at birth is 8-16 kg. Weaning occurs at 5-8 months. Behavior The Lama glama lives only in domestication. They are mostly kept grazing freely on grasslands and scrublands at elevations between 7,400-12,800 ft. (2,300-4,000 m). Llamas are very graceful in their movements. They run with a swinging stride, with their front and hind legs moving in unison on each side. Llamas lie down to rest and sleep. They are adept at spitting regurgitated food. Llamas use certain excretion sites that form dung heaps up to 2.4 meters in diameter. Fighting between males involves leg biting and "neck dominance." Copulation occurs while animals are in a prone position. Habitat Llamas are found in deserts, mountainous areas, and grasslands. Biomes: temperate grassland, desert, mountains

Family Cervidae

Deer

Cervids range in body size from the relatively small Andean Pudu (around 10 kg) to the very large moose of North America and Europe (800 kg). Some are stocky, others are slender and gracile in body shape. All have slender legs. Most are brown or gray in color, with white spots characterizing the young, and in a few species, the adults.

In all but one genus of cervids, at least the males have antlers. These structures are made of bone. They arise from a permanent bony base on the frontals called a pedicel. In temperate-zone cervids, the antlers begin growing in the spring as skin-covered projections from the pedicels. The dermal covering, or "velvet," is rich in blood vessels and nerves. When the antlers reach full size, the velvet dies and is rubbed off as the animal thrashes its antlers against vegetation. The antlers are used in combat by males during the breeding season, and drop off afterwards. Antlers vary from simple spikes to enormous, complexly branched structures, depending on the species and age of the individual bearing them. In most cervids, only males have antlers (but both sexes bear them in caribou). Curiously, the few species that lack antlers or that have small antlers usually have enlarged, sabre-like upper canines.

Their cheek teeth of cervids are selenodont but not usually as high-crowned as the teeth of the bovids. Upper incisors are absent; in the lower jaw, three incisors are present on each side of the jaw and are joined by an incisor-like canine. The dental formula is 0/3, 0-1/1, 3/3, 3/3 = 32 - 34.

Other traits of cervids include a vacuity (gap or opening) between the nasal and the lacrimal; lacrimal duct with two openings; presence of a postorbital bar; no sagittal crest; fusion of the third and fourth metacarpals (front limbs) and metatarsals (hind limbs) to form an elongated cannon bone (like bovids); reduction of lateral toes so that cervids (like bovids) bear their weight on digits three and four (paraxonic), which are hooved; reduction of the tarsals to five bones (calcaneus, astragalus, fused navicular and cuboid, fused ectocuneiform and mesocuneiform, and internal cuneiform); and a four chambered stomach with rumination and bacterial digestion of cellulose.

Some cervids are solitary but most live in herds that vary from a few individuals to many (depending on species, sex, and age). Most species are polygynous, and the males use their antlers in combat to obtain and defend females. Most species are browsers, but some include a substantial proportion of graze in their diets.

Cervids first appear in the late Oligocene. Some Pleistocene cervids had spectacular antlers; these include the "Irish elk" (Megaloceros, not an elk and not restricted to Ireland!), which had large palmate antlers with a span up to 3.7 m and a weight around 45 kg; and Eucladoceros, a large deer whose antlers were made up of large numbers of irregularly branched tines.

Southern pudu

Pudu puda

Pudu puda is a neotropical specie, can be found in the rainforests in the temperate zones of Argentina and Chile. Mass: 580 to 1340 g The southern pudu is the smallest deer in the world, ranging from 600-825mm in total body length and with a shoulder height from 250-430mm. The coat is composed of long coarse hair. The body color is a buffy agouti pattern. The middle back is reddish brown color, while the face, outer surface of the ears, narial patch, chin and under side are reddish. The fawns have a white spotted coat. The body is low to the ground with short thick legs. The eyes and the ears are small compared with the body size. The tail is almost non-exsistent. Males have short, less than 100cm, spike antlers.

The southern pudu's diet consists of fallen fruit, ferns, vines and small tree foliage. Pudus move slowly along as they look for food, often standing up on their hind legs to test the wind. They reach food by standing on their hind legs and jumping on fallen trees. They also may press down on ferns and saplings until they break off. Pudu bend over bamboo shoots and walk across them while they are horizontal to feed on upper foliage. They feed on the bark of young saplings approximately 6-12 inches off the ground. Pudu can go great lenghts of time without drinking water. It is thought that plants satisfy their need for water.

Pudu mate in the fall, November to January, and give birth in the spring. The gestation period is approximately 202-223 days. Only one fawn is born a year. At birth the young weigh less than one kilogram. It takes three months for the fawn to become full sized, and six months for females and eighteen months for males to reach sexual maturity. They are solitary animals that only come into contact with others of their species during rut. During rut, the male lays his chin on the female's back, smells her rear end, curls his upper lip, lays his forelegs on her back, and mounts her. Pudu navigate through the dense jungle by a network of well marked trails. The trails lead to spots for resting and feeding. The form dung piles, the majority of which are found near resting places. Each pudu has its own territory, approximately 40-60 acres in area.

The climate in the habitat of P. pudu consists of a short dry summer and a mild wet winter. The yearly rainfall is 74-150 inches. Pudu prefer dense and dark underbrush and bamboo groves because they offers protection from predators. They can be found anywhere from sea level to 9,600 feet above. They main biome is the temperate forest and the rainforest.

Conservation: Pudu es an endangered. specie, that are listed as endangered by the International Union for the Conservation of Nature and Natural Resources. The main factors that are threatening P. pudu include the destruction of habitat, the introduction of roe and fallow deer from Europe, and domestic dogs. Pudu cannot compete for food with the roe and fallow deer. The population of pudu has stabilized in Chile as a result of the tapering off of habitat destruction. The Game Preservation Director of Chile's Natural Forest Administration issued a statement saying that P. pudu will survive, as long as its habitat does. P. pudu is not currently threatened with immediate extinction, but its future is uncertain. Despite a study conducted by the World Wildlife Fund, the number of P. pudu in the wild is still unknown.

Wapiti or red deer

Cervus elaphus

The red deer is a nearctic, but there exist in Patagonia because was introduced at the  begining of this century. Although elk were once found throughout much of the Northern Hemisphere, today large populations are found only in the western United States from Canada through the Eastern Rockies to New Mexico, and in a small region of the northern lower peninsula of Michigan. Elk were reestablished in the eastern United States with three transplantations throughout the 1900's. Various elk populations in the western US, including Yellowstone National Park in Wyoming, contributed to the reestablishment.

Biology: Mass: 230 to 450 kg Elks range in color from dark brown in winter to tan in summer and have a characteristic buff colored rump. The head, neck, belly and legs are darker than both the back and sides. Elk generally have a long head with large ears and widely branching antlers as long as 1.1-1.5 m from tip to tip. A dark shaggy mane hangs from the neck to the chest. With a thick body, short tail and long slender legs, most elk stand approximately 0.75-1.5 m high at the shoulder and are 1.6-2.7 m from nose to tail. Most males are 10 percent larger than females and weigh twice as much.

Elk are browsers feeding on grasses, sedges, and forbs in summer and woody growth (cedar, wintergreen, eastern hemlock, sumac, jack pine, red maple, staghorn, and basswood) in the winter months. Favorites of the elk include dandelions, aster, hawkweed, violets, clover, and the occasional mushroom. Elk are ruminant animals and therefore regurgitate their food and remasticate to aid in digestion. This is also known as chewing cud. Breeding among elks takes place in early September. Males initiate the autumn courtship with a bugling call to attract their mates. Both males and females are sexually active at sixteen months, although young males do not usually mate due to competition from more mature elks.

Gestation generally lasts between 249-262 days (8-9 months) and results in a single birth (twins are rare). This low annual production is offset by a high investment in protective maternal care. At birth, calves weigh around 15-16 kg and have creamy spots on their back and sides. Their hooves are soft. Just after birth, a cow and her calves will live alone for several weeks. At 16 days the calf is able to join the herd, and weaning is completed within 60 days. Bulls form harems consisting on average of 1 bull, 6 cows, and 4 calves in the early summer months. Behavior Elk are very social animals; they live in summer herds with as many as 400 individuals. These herds are matriarchical and are dominated by a single cow. As the fall mating season approachs, bulls form harems, which they defend with their large size and aggressive nature. In spring, the sexes separate; the females leave to give birth, while bulls form their own separate bands. After birth, the cows and their calves form nursery groups until the calves are ready to join the herd. Pairing is seasonal and pairs are not maintained throughout the lifetime of the elks. Bulls are only territorial during the mating season and are otherwise not aggressive toward other elk. Elk browse in the early morning and late evening . They are inactive during the day and the middle of the night, when they spend most of their time chewing their cud.

Elk have a close association with white-tailed deer, sharing similar environments and similar habitats. Predators of elk do include the mountain lion, gray wolf, and bears. Calves may fall victim to bobcats and coyotes.

Elk prefer open woodlands and avoid dense unbroken forests. Elk can be found in coniferous swamps, clear cuts, aspen-hardwood forests, and coniferous-hardwood forests. Elk have a home range of approximately 600 square miles. Biomes: taiga, temperate forest & rainforest, temperate grassland

References

Baker, R. H. 1983. Michigan Mammals. Michigan State University Press. East Lansing, MI. 566-577. Kurta, A. 1995. Mammals of the Great Lakes Region. University of Michigan Press. Ann Arbor, MI. 261-264.

Nowak, R.M. and J.L. Paradiso. 1983. Walker's Mammals of the World, 4th edition. John Hopkins University Press, Baltimore, MD.

Simpson, C. D. 1984. Artiodactyls. Pp. 563-587 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.

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