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permanent resident of these swamps (see Fig.
1-2). Swamp antelope called the lechwe (
Kobus
leche
) are also found in large numbers within
the permanent swamps. Estimates suggest
approximately 40,000 individuals, making them
one of the greatest concentrations of large
mammals within the delta (Bass 2009). During
the l ood season, they spread across the delta
to take advantage of new foraging sites.
Seasonally or occasionally l ooded swamps
and grasslands found in shallow depressions
are generally observed beyond the permanent
swamps (Bass 2009). Elsewhere, mopane or
mopani (
Colophospermum mopane
) dominant
woodlands are found across the outer edges of
the delta and across northeastern Bostwana.
These dry open woodlands also include sparse
grass and brush cover. Lastly the salt pans of
the Makgadikgadi observe high concentrations
of salts and minerals and virtually no vegetative
cover when dry. During particularly wet seasons
when excess water from the delta makes its way
to the pans, algal blooms are not uncommon
(McIntyre 2007).
The duration of l ooding within the delta is
dependent on precipitation rates, water-table
levels and evapotranspiration rates. The delta
acts as an oasis across a particularly arid region
of Africa providing a critical resource through
the dry season of the year and attracting fauna
from great distances. A prime example of this is
the elephant (
Loxodonta africana
). Estimates
suggest up to 30,000 individuals consider the
Okavango Delta home for part of the year (see
Fig. 14-19). Once the delta's l oods have receded,
the elephants migrate farther northeast to seek
refuge in the mopane woodlands (Bass 2009).
Other commonly found seasonal fauna include
large numbers of buffalo (
Syncerus caffer
),
zebra (see Fig. 7-40) and impala (
Aepyceros
melampus
) (Ramberg et al. 2006, p. 329). Giraffe
(Fig. 15-6), kudu antelope (
Tragelaphus strep-
siceros
), and African lion (Fig. 15-7) are also
found across the delta. Thousands of slightly
elevated tree-covered islands dot the landscape
and serve as a terrestrial refuge for animals
during the full l ood season.
The human fossil record dates back several
thousands of years across this region of
Figure 15-5.
Space-shuttle photograph of the
Okavango Delta, Botswana, Africa. Dark gray indicates
active vegetation. Linear stripes to the north and west
are dunes in the Kalahari Desert. Image courtesy of K.
Lulla; STS61A-43-29, November 1985.
Makgadikgadi salt-pan depression within the
greater Kalahari Basin. The Makgadikgadi salt
pans are remnants of a vast ancient lake system
that covered this region. Evidence from paleo-
l oodplains suggests signii cant l uctuations in
alluvial deposition patterns across the region
with a delta that could easily be two or three
times its current size. Ramberg et al. (2006) sug-
gested a combination of tectonic activity, climate
and precipitation changes as possible causes for
the delta's variable size through geologic history.
At present, precipitation combined with the
Okavango River's waters give rise to a montage
of seasonal and permanent wetlands that in full
l ood may extend over 15,000 km
2
, displaying
remarkable species richness (Heinl et al. 2007).
Ramberg et al.'s (2006) review of recorded
species indicated a delta with some 1300 species
of plants, 71 species of i sh, 444 birds, and 122
mammals. Permanent wetlands are found along
the panhandle and the proximal reaches of
the delta. Here, reeds (
Phragmites
), papyrus
(
Cyperus papyrus
), sedges, bulrushes and other
aquatic plants dominate the landscape. The hip-
popotamus (
Hippopotamus amphibious
) is a
