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
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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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