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Bonacic C  (2012)  Vicuña Ecology and Management.  ECOLOGY.INFO 27

Vicuña Ecology and Management

Note: This online review is updated and revised continuously, as soon as results of new scientific research become available.  It therefore presents state-of-the-art information on the topic it covers.

The vicuña (Vicugna vicugna) is the smallest living member of the camel family (Camelidae). It dwells 3,000 to 4,600 meters above sea level on the high Andean plateau of central and southern Peru, western Bolivia, northern Chile and northwestern Argentina.  There it inhabits the puna, a high altitude steppe-like grassland and desert that is treeless and located above the zone of cultivated crops. 

The vicuña is well adapted to living in this harsh environment.  It is clothed in a fleece of the finest known wool, one that has been valued and harvested by man since pre-Columbian times.  This fleece protects the vicuña from the extreme cold and winds of the puna, and also provides a cushion for its body when resting on the ground.  In comparison to old world camels, the vicuña has more deeply cloven feet, which allow it to walk and run more adeptly on the rocky slopes, cliffs and rockslides that are common on the puna (Koford 1957).

Another important adaptation is the vicuña's rodent-like teeth, which grow continuously and allow the vicuña to "graze upon small forbs and perennial grass close to the ground (Franklin 1983; Renaudeau D'Arc et al. 2000)." The vicuña is the "only ungulate that has these open-rooted, continuously growing incisors (Miller 1924; Franklin 1983; Renaudeau D'Arc et al. 2000)." 

The vicuña shows interesting similarities to the pronghorn antelope (Antilocapra americana) of North America (Koford 1957).  Although unrelated, both of these inhabitants of windswept grasslands are of similar size and extremely swift of foot, running away at incredible speeds to escape danger.  Both are also strongly inquisitive, walking "toward any moving object that is partly hidden, as if to identify it by closer inspection (Koford 1957)."

The vicuña  is one of four living representatives of the camel family that are found in South America, the other three being the guanaco (Lama guanicoe), llama (Lama glama) and alpaca (Vicugna pacos). Figure 1, Figure 2.  The vicuña and guanaco are wild species, while the llama and alpaca are domesticated.  In this review, I discuss the ecology and management of the vicuña.

Geographic distribution and races

The vicuña currently inhabits the high Andes between latitudes 9o 30' south and 29o 00' south.  In the past, however, its range extended much further to the north.  For example, in the sixteenth century, Cieza de Leon ([1550] 1984) mentioned vicuñas living near Huamachuco, Peru, and in the regions of Loja and Riobamba, Ecuador.

Thousands of years ago, in the late Pleistocene and Early Holocene, vicuñas were also found further south than they are today, all the way to the southern tip of South America (Weinstock et al. 2009).

Two geographic subspecies of the vicuña are recognized: a southern race Vicugna vicugna vicugna, and a northern race Vicugna vicugna mensalis (Torres 1992; Palma et al. 2001; Marin et al. 2007).   The approximate dividing line between these two races is 18o south latitude, however, the exact boundary has not been mapped and the recent rapid population recovery makes it difficult to elucidate past distributions of the two subspecies. The southern race is both larger and lighter in color than the the northern race.

Relationship to Domestic Camelids

For many years, the origins of South America's domestic camelids, the llama and alpaca, were unclear due to "hybridization, near extirpation during the Spanish conquest and difficulties in archaeological interpretation (Kadwell et al. 2001)."

Biologists long assumed that both the alpaca and llama were descended from the guanaco, and that the vicuña had never been domesticated.  However, recent genetic research suggests that while the llama is indeed descended from the guanaco, the alpaca is descended from the vicuña (Kadwell et al. 2001; Marin et al. 2007).  The time and place of the domestication of the alpaca is now estimated to be "6000–7000 years before present in the Peruvian Andes (Kadwell et al. 2001)." 

The genetic studies also show that the northern race of the vicuña, V. v. mensalis is the one most closely related to the alpaca, while the southernmost vicuña V. v. vicugna is most closely related to a basal taxon (i.e. a primitive South American camelid)  (Kadwell et al. 2001).

Food

The vicuña feeds mainly on grasses, but also includes shrubs, annual forbs and graminoids in its diet (Mosca Torres et al. 2010; Borgnia et al 2010).

Social organization

The vicuña is a social animal and typically occurs in herds.  Solitary individuals are rare.  Herds are of two kinds: (1) family groups, and (2) male troops.

A family group is created by a dominant male that establishes and maintains a permanent year-round territory (Macdonald 1985), the size of which varies depending upon the quality of grazing forage and other resources (Franklin 1983).  A family group consists of this dominant male, multiple adult females, juvenile females (one or more years of age) and offspring of both sexes younger than one year of age (Franklin 1982; Wilson 1975; Bonacic et al. 2002).

A male troop is composed of juvenile males (one to four years old) that have been expelled from their family groups, and ageing males that have lost their territories. Unlike family groups, male troops do not hold territories and do not seem to have leaders (Koford 1957).  They constitute a temporal non-reproductive category (Franklin 1983). Male troops are also called "bachelor groups."

Solitary vicuñas are either single adult males without territories, or single adult males with territories but without females. Some are former leader males that have been displaced from their territories by new males.  Solitary vicuñas constitute another non-reproductive unit (Glade and Cattan 1987).

Because male and female vicuñas look so similar, it is sometimes difficult to tell whether a band of vicuñas is a family group or a male troop.  However, during autumn, winter and early spring, family bands can be recognized because they include offspring younger than one year of age (Koford 1957).

Communal Dung Piles

Vicuñas and other South American camelids defecate and urinate on communal dung piles.  All individuals of a band, whether it be a family group or a male troop, use the same dung piles, and " displaced bands freely use dung piles situated on the territories of other bands (Koford 1957)."  Even more remarkable is the fact that "alpacas and lamas use the same dung piles that are used by vicuñas (Koford 1957)."

A typical communal dung pile is said to be "one foot thick at the center and five yards in diameter (Koford 1957)."  Where vicuñas are common and the ground is flat, dung piles may be regularly spaced, about fifty yards apart (Koford 1957).

An important ecological question that needs to be answered is: "what effect do these dung piles have on the growth, distribution and abundance of the various plants and animals of the puna?"  According to Koford (1957), "most of the plants that grow on or close to these piles are conspicuously different from the plants of the surrounding pasture," and "late in the wet season, brilliant green circular spots mark the location of dung heaps, and on many barren hills these spots are the only greenery that can be seen from a distance."

Predators

In settled areas, domestic dogs from local villages kill vicuñas more frequently than any other non-human predator (Koford 1957).  Nevertheless, there are also native carnivores that prey upon vicuña and these include the puma (Puma concolor) and Andean fox (Pseudalopex culpaeus) (Cajal and Lopez 1987).  The latter species has been called the "ecological equivalent" of the coyote (Canis latrans) of North America (Koford 1957).

Like the pronghorn antelope of North America,  newborn vicuñas can run away from predators soon after birth.  For example, an infant vicuña observed by Koford (1957), held its neck and head up 20 minutes after birth, and walked a hundred meters up across a rocky moderate slope following its mother one hour after birth.  Within 3 hours of birth, it was seen running 200 meters across a rocky slope at a speed of 24 kilometers per hour with its mother.

The newborn vicuña is thus most vulnerable to predators during the first hour after birth.  Koford (1957) observed a vicuña giving birth and found that within a minute after the young dropped to the ground, 5 adult Andean Condors (Vultur gryphus) landed 9 meters uphill from the newborn.  Within 20 minutes, more condors arrived swelling the total to 14 condors.  Defensive behavior of the mother vicuña, and other pregnant females in the family group, prevented the condors from approaching closer than about 2 meters of the helpless newborn.  Within a half hour the condors departed.  This bird is otherwise unable to prey upon living vicuñas, despite the fact that it is often seen eating the carrion of dead vicuñas.

Habitat Selection

Although the vicuña is restricted to the puna, it does not use all parts of this arid ecosystem.  In the Argentinian Andes, vicuñas are absent from the most common habitat of the puna, the peladar, which is a wide open area of "rocky bare soil where isolated shrubs of Acantholippia hastulata" sometimes occur (Renaudeau d'Arc et al. 2000). 

In contrast, vicuñas prefer grazing in the least common habitat of the puna: the bofedal, a swampy area usually less than one hectare in area that is "associated with ground water, lagoons or streams," and that creates "locally moist edaphic conditions, where hardy grass and green herb, represented by Oxycholoe sp. and rizomateus species, cover almost 100% of the soil  (Renaudeau d'Arc et al. 2000)."

Preference for bofedales is also reported by Glade (1987), Lucherini and Birochio (1997) and Lucherini et al. (2000).  See color photo:  Figure 3.

In the Laguna Pozuelos Reserve, Argentina, vicuñas preferred habitats dominated by tall grasses (Parastrephia lepidophylla or Festuca spp.) and also habitats with dense vegetation, such as those in and around wetlands (Arzamendia et al. 2006).

Koford (1957) reported that although vicuña territories include wetlands, they were usually located near ascending slopes.  He noted that vicuña escape from many predators by running to steep slopes, and that vicuña use dry sites on "moderate slopes, well downhill from ridgetops" as bedding places to spend the night.  Another value of slopes is that the bases of slopes are often good places for grazing because the soil there is deeper and moister than higher up on the slope (Koford 1957).

Habitat use varies according to time of day.  In extensive zones of the Andes, vicuñas spend the night, early morning and late afternoon on the slopes.  Later in the morning, they descend to the bofedales where they graze extensively (Glade 1987; Renaudeau d'Arc et al. 2000).

Vicuñas drink water every day and are usually found within two kilometers of water (Koford 1957).  This water can be a lake, stream or spring, but often even a pool alongside a road or a puddle on a mat of vegetation will suffice (Koford 1957).

In a part of the Argentinian Andes that lacks permanent human settlements, Lucherini et al. (2000) found that during a year when pumas invaded their study site, male troops of vicuñas decreased time spent in the bofedales and other vegetation within 100 meters of a river, and increased time spent in more sparsely vegetated areas over one-half kilometer from the river.  These researchers believed that the reason for the vicuña habitat shift was fear of the pumas, which hunted more frequently along the river and killed more vicuñas there.

Activity Patterns

During autumn in Argentina, vicuñas spend more time foraging for food and less time resting than during summer (Vila and Cassini 1993).  In both seasons, vicuñas drink water throughout the day, with peak drinking at noon (Vila and Cassini 1993).   However, vicuñas drink water more frequently in the afternoon during summer than during autumn (Vila and Cassini 1993). An explanation for these differences is that ambient temperatures and humidity are also higher in summer than in autumn (Vila and Cassini 1993).

In Chile, Glade (1987) observed that the birth season occurred between the second week of February and last week of March, with 65-68 live young per 100 births.  Fourteen percent of calves died within 3 months, and calf mortality reached 17.6% by one year of age. The surviving calves were rejected from the family groups when they were between 6 and 12 months old and 54.5% of total expulsions occurred in February. Glade also described the sex ratio in adult vicuñas as 33 males per100 females, and the mean family group size as 5.6 individuals (1 leader male, 3 females and 1.6 calves).

Interactions between camelids

Vicuñas can be seen foraging near domestic herds of llamas, alpacas and even sheep during the day, mainly in meadows or bofedales.  Daily herding practices are very low intensity, and shepards typically move their domestic herds from corrals to the meadows for grazing during midday.  Such close distance grazing is common on the altiplano, with little disturbance caused to the vicuñas.  However, the close proximity of vicuñas with domestic herds facilitates inter-specific disease transmission.  In addition, vicuñas are sometimes herded back to corrals with llamas and alpacas, and orphan vicuñas are raised by farmers.

Vicuñas can be forced to crossbreed with alpacas, producing a fertile offspring called "paco-vicuña."  The fine fiber of the vicuña becomes a bit coarser in the paco-vicuña, and the latter is less tame than an alpaca.

Physical Characteristics

The vicuña is the most distinct of the South American camelids.   It is smaller in size than the alpaca, with an adult body weight of only 40 to 50 kilograms and height of about 1.5 meters (Macdonald 1985).  Total body length (tip of nose to base of tail) varies from 1.1 to 1.9 meters (Paucar et al. 1984; Burton and Pearson 1987) . 

The vicuña can be distinguished from the alpaca, guanaco and llama by its smaller size, slimmer build and coloration.  It is maroon-dark on top with a white belly and inner thighs.  Sometimes vicuña-colored alpacas are present in domestic herds, but they can be distinguished from vicuñas by having a larger fleece and sturdier build.  Small guanacos (chulengos) can be similar in size and behavior to juvenile or adult vicuñas, but typically have dark faces compared to the light faces of vicuñas.

Population Censuses

The ecological habits of the vicuña and the open visibility of the puna make it possible to use total count techniques to census and estimate populations (Cueto et al. 1985; Hoffmann et al. 1983).  These estimates have been a key aspect of programs that assess both the effectiveness of anti-poaching measures and the conservation of vicuñas. Annual censuses were started in Perú in 1969 and in Chile in 1975.   Recent population estimates are 120,000 individuals in Perú, 30,000 in Bolivia, 25,000 in Chile and 23,000 in Argentina (Figure 2) (Galaz 1998; Hoces 1999; Rendon 1998).

Finish reading this review on Page 2

Photograph at top of page:  A herd of vicuñas on the Peruvian puna.  In the center of the photo is a bofedal (a wetland that provides rich grazing habitat for the vicuñas).  Photo by Stuart Pattullo.

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