Guanacos are found in South America from northern Peru southward. Their range includes Peru, western Bolivia, Argentina, Chile, Tierra del Fuego, and Navarino Island (Fowler, 2010). Populations in the northern part of the distribution, between northern Peru and northern Chile, are assigned to the subspecies Lama guanicoe cacsilensis. The remaining populations are assigned to the subspecies Lama guanicoe guanicoe (Franklin, 2011). Guanacos were introduced from Argentina to Staats Island, one of the Falkland Islands, in the 1930's, and a thriving population remains there (Franklin and Grigione, 2005). (Fowler, 2010; Franklin and Grigione, 2005; Franklin, 2011)
Guanacos are the mostly widely distributed of the four species of South American camelids and they occupy the most diverse range of habitats (Franklin, 1982). Adapted to harsh, highly seasonal environments, guanacos are able to cope with such starkly contrasting climates as those of the hyper-arid Atacama Desert in northern Chile and the perpetually wet Tierra del Fuego at the southern tip of South America (Franklin, 1982). Guanacos prefer open, dry habitats, and they avoid steep slopes, cliffs, and rock (Franklin, 1982). They are found in 4 of the 10 major South American habitats: desert and xeric shrublands, montane and lowland grasslands, savannas and shrublands, and wet temperate forests (Franklin, 2011). In general, guanaco habitats are characterized by high winds, low precipitation, and low primary productivity (de Lamo et al., 1998; González et al., 2006). Guanacos are distributed over an elevation range from sea level to 4,500 m (Franklin, 2011). (Franklin, 1982; Franklin, 2011; González, et al., 2006; de Lamo, et al., 1998)
Guanacos have long, slender necks and long legs typical of camelids (Franklin, 2011). Adults are 90 to 130 cm high at the shoulders, and adult body mass is between 90 and 140 kg, with the smallest individuals found in northern Peru and the largest in southern Chile (Fowler, 2010; Franklin, 2011). All guanacos have pelage that is light to dark reddish brown, with white countershading on the chest, belly, and legs, and gray or black coloration of the head (Wheeler, 1995). Though the general appearance is similar in all populations, overall coloration can vary somewhat by region, with northern populations tending to be relatively light (Franklin, 2011). There is no sexual dimorphism in body size or coloration, although males have significantly enlarged canines (Franklin, 2011; Sarno and Franklin, 1999). (Fowler, 2010; Franklin, 2011; Rosenmann and Morrison, 1963; Sarno and Franklin, 1999; Wheeler, 1995)
All camelids have relatively small heads, no horns or antlers, and a split upper lip. South American camelids (Lama glama, , Vicugna pacos, and Vicugna vicugna) lack humps, and can be distinguished from Old World camelids (Camelus bactrianus and Camelus dromedarius) by their smaller size and slender, rather than broad, feet (Franklin, 2011). Guanacos are slightly larger than alpacas and significantly larger than vicuñas, though smaller and less heavily built than llamas (Rosemann and Morrison, 1963). Within the South American camelids, tooth characteristics can be used to distinguish guanacos and llamas (genus Lama) from vicuñas and alpacas (genus Vicugna). Guanacos and llamas have spatulate, closed-root lower incisors, and both the labial and lingual surfaces of each crown are enameled. Vicuñas and alpacas have elongate, ever-growing incisors with enamel only on the labial sides (Fowler, 2010). The general dental formula of South American camelids is 1/3, 1/1, 1–2/1–2, 3/3 = 28–32 (Franklin, 2011). (Fowler, 2010; Franklin, 2011; Rosenmann and Morrison, 1963)
To cope with the harsh and variable climates they encounter throughout their broad distribution, guanacos have developed physiological adaptations that allow them to respond flexibly to changes in environmental conditions (de Lamo, 1998). By adjusting their body position, for example, individuals can “open” or “close” thermal windows—areas of very thin wool located in their front and rear flanks—in order to vary the amount of exposed skin available for heat exchange with the environment (de Lamo et al., 1998; Franklin, 2011). This allows them to reduce heat loss quickly when the ambient temperature drops (de Lamo et al., 1998). (Franklin, 2011; de Lamo, et al., 1998)
Guanaco reproductive strategy is a form of resource-defense polygyny: resident males defend feeding territories against the intrusion of other males (Franklin, 1982). These territories, which may offer protection from predators as well as the food resources essential to breeding females, are typically 0.07 to 0.13 km^2 in size and occupied either year-round or seasonally by family groups (Franklin, 1982; Franklin, 2011; Sarno and Franklin, 1999). Despite the name, the members of a particular family group are not necessarily related (Sarno et al., 2003, p. 23). Each family group is composed of one territorial male and a variable number of females and young, with total adult membership usually between 5 and 13 (González et al., 2006). Female membership in family groups is fluid, with the resident male generally allowing females and juveniles to leave freely, but regulating the entry of new females (Franklin, 2011). Guanaco males become territorial at 4 to 6 years old, and thereafter they engage in violent competition to establish residence in feeding territories and control of family groups (Fowler and Bravo, 2010). Although guanacos are not sexually dimorphic in body size, males have significantly enlarged canines, which they use in intense, frequently injurious male–male fights (Franklin, 2011). Aggressive behaviors seen in guanaco males include spitting (up to 2 m); making threatening displays; chasing and fleeing; biting at the legs, hindquarters, and necks of their opponents; ramming chests; and neck wrestling (Franklin, 2011). Fights are frequent and serious enough that neck, leg, and body wounds are commonly observed in territorial males (Franklin, 2011). (Fowler and Bravo, 2010; Franklin, 1982; Franklin, 2011; González, et al., 2006; Sarno and Franklin, 1999; Sarno, et al., 2003)
Guanacos reproduce seasonally and there is one breeding season per year. Mating occurs in family groups during the austral summer, typically between early December and early January (Franklin, 2011). The timing of birth is influenced by environmental conditions and thus varies widely by latitude, but offspring are generally born in November and December (González et al., 2006; Sarno et al., 2003). The gestation period is 11.5 months, and a single offspring, with birth weight about 10% of maternal weight, is born to each breeding female every year (Sarno and Franklin, 1999; Sarno et al., 2003). Twins are extremely rare, and only one neonate ever survives (Franklin, 2011). (Franklin, 2011; González, et al., 2006; Sarno and Franklin, 1999; Sarno, et al., 2003)
As expected in light of their long gestation, guanaco young, called chulengos, are precocial, able to stand as early as 5 to 76 minutes postpartum (González et al., 2006; Hofman, 1993). Chulengos exhibit following, rather than hiding, behavior; this may be a strategy to avoid predation in open habitats (González et al., 2006; Ralls, Kranz, and Lundrigan, 1986). Because of the need to grow quickly in advance of harsh winters, chulengos begin grazing within a few weeks of birth, and they forage almost exclusively by the time they are 8 months old (Franklin, 2011; González et al., 2006; Sarno et al., 1999). (Franklin, 2011; González, et al., 2006; Hofman, 1993; Ralls, et al., 1986; Sarno, et al., 1999)
Female guanacos reach sexual maturity at 2 years old and breed for the first time at age 3 (Franklin, 2011). Males reach maturity at 2 to 4 years old and begin breeding after obtaining a feeding territory between age 2 and age 6 (Fowler and Bravo, 2010; Franklin, 2011). Each year, 75% of adult females and 15 to 20% of adult males reproduce (Sarno and Franklin, 1999). (Fowler and Bravo, 2010; Franklin, 2011; Sarno and Franklin, 1999)
Guanacos are induced ovulators, like other South American camelids, and females undergo a follicular wave cycle rather than a regular estrous cycle (Franklin, 2011). Ovulation occurs 24 to 48 hours after copulation and is triggered by a hormonal signal in the semen (Fowler and Bravo, 2010; Franklin, 2011). (Fowler and Bravo, 2010; Franklin, 2011)
Guanaco mothers play an important role in defending their young against predators (González et al., 2006). Predation accounts for a large proportion of juvenile mortality, and maternal aggressiveness toward potential predators, including threatening, spitting, charging, and kicking, has been shown to increase the survival of guanaco young (González et al., 2006; Sarno et al., 1999). Birth weight, growth rate, and suckling behavior are similar in male and female offspring (Sarno and Franklin, 1999). All chulengos are weaned between 4 and 8 months of age, although they return to nursing as yearlings after the birth of the next season’s young (Fowler and Bravo, 2010). This period of overlap, when neonates and older juveniles coexist and compete for resources in family groups, suggests a high level of parental investment in guanacos compared with other South American camelids (Franklin, 1982). Juvenile vicuñas, for example, are expelled from family groups before they reach one year of age, and thus are absent before the next birthing season begins (Franklin, 1982). It has been hypothesized that, for guanacos, additional time in the natal group is required for further growth or socialization (Franklin, 1982). (Fowler and Bravo, 2010; Franklin, 1982; Franklin, 2011; González, et al., 2006; Sarno and Franklin, 1999; Sarno, et al., 1999; Sarno, et al., 2003)
In guanacos, juveniles of both sexes are expelled from family groups in late spring and early summer, when they are between 11 and 15 months old (Franklin, 1982; Sarno et al., 2003). As the breeding season progresses, territorial males become increasingly aggressive toward juveniles born the previous year, until all yearlings are finally forced to disperse (Sarno et al., 2003). Since forced dispersal is not sex-biased, and since male aggression toward yearlings peaks when neonates are beginning to forage and feeding competition within the family group is high, the expulsion of juveniles is probably aimed at freeing up resources to reduce competition for food (Sarno et al., 2003). Upon dispersal, yearling females often travel alone or together among solitary territorial males (Sarno et al., 2003). Alternatively, they may join female groups or established family groups (Franklin, 2011). Yearling males usually join male groups, where they remain for 1 to 3 years while honing their fighting skills by means of aggressive play (Franklin, 2011). (Franklin, 1982; Franklin, 2011; Sarno, et al., 2003)
Guanacos have a fairly flexible social system, and populations may be sedentary or migratory depending on the year-round availability of forage (Franklin, 1982). During the breeding season, guanacos are found in three primary social units: family groups, male groups, and associations of solitary males (Franklin, 2011; González et al., 2006). Each family group is headed by a territorial adult male and contains a variable number of adult females and young (González, 2006). Outside of family groups, non-breeding, non-territorial juvenile and adult males form male groups of 3 to 60 individuals and forage in distinct male-group zones (Franklin, 2011). Mature males with territories but without females are called solitary males, and they may form associations of about 3 (Franklin, 2011). (Franklin, 1982; Franklin, 2011; González, et al., 2006; Ortega and Franklin, 1995)
Environmental conditions determine group composition after the breeding season ends (González et al., 2006). Where winters are mild and forage supply is stable, populations are sedentary and breeding males defend their feeding territories year round, though females may leave to form winter groups of 10 to 90 individuals (Franklin, 1982; Franklin, 2011; González et al., 2006). Where drought or snow cover reduces food availability in the winter, guanacos form mixed-sex herds of up to 500 individuals and travel to more sheltered or food-abundant areas (Franklin, 2011; González et al., 2006). These migrations may be altitudinal or lateral shifts, depending on climate and geography (Franklin, 1982). In migratory populations, increased group size during winter migrations may be a strategy for reducing predation, since snow cover and relative isolation in the environment make guanaco populations especially vulnerable during this time (Ortega and Franklin, 1995). (Franklin, 1982; Franklin, 2011; González, et al., 2006; Ortega and Franklin, 1995)
There is a good deal of variability in home range size. Populations in eastern Patagonia have ranges of 4 to 9 km^2, for example, while those in western Patagonia may have ranges twice as large (Baldi et al., 2010). (Baldi, et al., 2010)
The open habitats that guanacos inhabit facilitate visual communication by allowing gestures to be seen over long distances (Franklin, 2011). Male guanacos perform a series of displays to assert dominance over potential rivals (Franklin, 2011). Broadside and S-neck displays may be used for advertising a male’s presence, asserting his status, or intimidating other males (Franklin, 2011). Other gestures, such as tail wagging, seem to be important for intra-group communication among both males and females (Franklin, 1975). Juvenile guanacos commonly use submissive displays to appease aggressive males attempting to drive them from family groups, and in doing so they can delay their forced dispersal (Sarno et al., 2003; Sarno et al., 2006). When approached or threatened by an adult male, a juvenile will enter a submissive crouch by lowering its neck, bending its knees, and raising its tail, a position that may strategically mimic the nursing posture (Franklin, 2011; Sarno et al., 2006). Guanacos produce a range of vocalizations for conveying information and negotiating social roles (Franklin, 2011). Notable among these are alarm calls, given to warn other group members of the presence of potential predators, and clicking noises, used in agonistic encounters between males (Franklin, 1982; Franklin, 2011). Odor is an important means of communication for many camelids (Franklin, 2011). Male guanacos use dung piles for territory marking and intra-group orientation, or keeping family groups together within territories (Franklin, 1975). (Franklin, 1975; Franklin, 1982; Franklin, 2011; Sarno, et al., 2003; Sarno, et al., 2006)
Guanacos are herbivorous. As browser-grazers, they are able to exploit a diverse range of food sources, and they exhibit flexible feeding behavior that varies across space and time (Franklin, 1982; González et al., 2006). In the Andean foothills of Argentina, two shrub species, Mulinum spinosum and Colletia spinosissima, constitute a large proportion of the year-round diet (Bahamonde, Martin, and Sbriller, 1986). When their preferred foods are not available, however, guanacos will eat lichens, fungi, cacti, fruit, and flowers in addition to grasses and shrubs (Franklin, 2011). Their generalist diet and efficient water and energy metabolism have enabled them to survive under harsh circumstances, including in extremely arid climates (Franklin, 1982). (Bahamonde, et al., 1986; Franklin, 1982; Franklin, 2011; González, et al., 2006)
The primary predators of guanacos are pumas, which coexist with guanacos throughout their distribution except on Navarino Island and the islands of Tierra del Fuego (González et al., 2006; Novaro et al., 2009). In some populations, predation by pumas accounts for up to 80% of chulengo mortality (Sarno et al., 1999). Although pumas were the only confirmed predators for many years, researchers have recently reported attacks on juvenile guanacos by culpeos, which are present on Tierra del Fuego as well as in other parts of the guanaco range (Novaro et al., 2009). (González, et al., 2006; Novaro, et al., 2009; Sarno, et al., 1999)
For guanacos, group living is an important anti-predation strategy (Franklin, 2011; Novaro et al., 2009). Thanks to the protective effects of dilution and early detection, individuals living in groups are able to invest less time in vigilance, and more time in foraging, than are individuals living alone (Franklin, 2011; Novaro et al., 2009). Guanacos generally exhibit a “see and flee” response when they encounter potential predators (Franklin, 1982; Novaro et al., 2009). An individual will maintain visual contact with the predator until it gets too close, then give an alarm call to alert the rest of the group and escape by running away (Franklin, 1982). This strategy tends to be effective against pumas, which do not pursue their prey for long distances. By contrast, a more aggressive approach may be advantageous in dealing with smaller, cursorial predators such as culpeos. In at least one instance, adult guanacos have been observed engaging in cooperative defense against a culpeo: they cornered it, kicked it, and eventually drove it away after it chased and attacked a chulengo (Novaro et al., 2009). (Franklin, 1982; Franklin, 2011; Novaro, et al., 2009)
Throughout their distribution, guanacos play an important role in maintaining ecosystem function. They disperse seeds in their feces, control vegetation growth by grazing and browsing, and serve as food sources for scavengers and predators (González et al., 2006). Guanaco carcasses are commonly eaten by foxes (Lycalopex griseus, Lycalopex culpaeus) and birds of prey (Caracara plancus, Vultur gryphus), and guanacos are hunted by pumas and culpeos (González et al., 2006; Novaro et al., 2009). (Franklin, et al., 1999; González, et al., 2006; Novaro, et al., 2009)
Throughout the Andes and in parts of Patagonia, guanacos have historically been the primary prey species for pumas (Franklin et al., 1999; González et al., 2006). But as hunting pressures and habitat degradation have caused guanaco population densities to decline, they have been largely replaced in predator diets by introduced and domesticated species, such as red deer, sheep, and European hares. In some areas, interactions with pumas and other species have fallen to negligible levels and guanacos are said to be ecologically extinct (Novaro, Funes, and Walker, 2000). Guanacos compete with introduced domesticated species for forage, including compete for forage with sheep, goats, horses, donkeys, and cattle. (Franklin, et al., 1999; González, et al., 2006; Novaro, et al., 2000)
Guanaco wool is highly valued on the international market and prized for its softness and warmth (Baldi et al., 2010; Franklin, 2011). Although some guanacos are kept in captivity for the purpose of producing wool, efforts to capture, shear, and release wild guanacos have increased rapidly since these initiatives began in the late 1990's (Baldi et al., 2010). The demand for guanaco shearing is growing and Argentina now produces 1500 kg of guanaco wool per year (Baldi et al., 2010; Franklin, 2011). In addition, specialists called chulengueros hunt chulengos in Argentina for their pelts (Franklin, 1982). (Baldi, et al., 2010; Franklin, 1982; Franklin, 2011)
Guanacos compete for forage with domesticated sheep, goats, horses, donkeys, and cattle and are considered by many ranchers to be pests (Baldi et al., 2010; González et al., 2006). (Baldi, et al., 2010; González, et al., 2006)
Because guanacos remain widespread in South America, they are classified as Least Concern on the IUCN Red List. Still, careful management of local populations is necessary to prevent population declines (Baldi et al., 2008). This is true especially in light of the increasing demand for live shearing, which has resulted in capture myopathy in some wild guanacos and which may have further negative consequences for the growing number of populations involved (Baldi et al., 2008; Baldi et al., 2010). Guanaco populations are also threatened by disease transmission from domestic livestock; by overhunting, especially of chulengos for pelts; and by land degradation due to intensification of agriculture and overgrazing by sheep (Baldi et al., 2004; Baldi et al., 2008; Baldi et al., 2010; Franklin, 1982; González et al., 2006). Fences erected by sheep ranchers can interfere with guanaco migratory routes and can kill chulengos that become entangled in the wires (Baldi et al., 2010; Franklin, 1982). (Baldi, et al., 2004; Baldi, et al., 2008; Baldi, et al., 2010; Convention on International Trade in Endangered Species of Wild Fauna and Flora, 2013; Franklin, 1982; González, et al., 2006)
As a result of human pressures, guanacos now occupy less than 40% of their original distribution in South America and existing populations are frequently small and fragmented (Baldi et al., 2010; Franklin, 2011). The governments of Argentina, Bolivia, Chile, and Peru regulate the use of wild guanacos within their borders, but enforcement of conservation laws tends to be weak, and most guanaco habitats are not under effective protection (Baldi et al., 2008). (Baldi, et al., 2008; Baldi, et al., 2010; Franklin, 2011)
Eva Hoffman (author), Yale University, Eric Sargis (editor), Yale University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
ovulation is stimulated by the act of copulation (does not occur spontaneously)
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
having more than one female as a mate at one time
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
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