discussed by Richardson (1977). As the chances are remote that the lichen growth of
the area
will
be
used as a food source by non-ruminant mammals no further consi-
deration was given to this aspect.
In ruminant diets the amino acid composition
is
of
less impo'rtance than the total
protein and carbohydrate content. The use of lichens
as
a food source by vertebrates
has been summarized by Richardson (1975) and Richardson
& Young (1977). It'was
mentioned by Richardson (1975) that lichens preferred by reindeer were not those with
the highest protein content but the ones which contained a high proportion
of
com-
plex carbohydrates. He also stated that a deer requires the equivalent
of
about 2
kg
of
dry lichen daily. To obtain that amount an animal browses about 12 m
2
of
lichen
which amounts to approximately 2160 m
2
of pasture every 180 days. Because
of
the slow growth of lichens a particular lichen range
is
not ready for regrazing for
2-5
years after modest grazing. This period increases to
10-15
years after intense grazing
(Richardson, 1975).
It seems that the lichen fields of the Namib Desert are utilized by animals (springbuck
in particular) as a supplementary food source, especially during prolonged drought
periods inland (sightings by D.C.J.W.; CoetzeeI, 1978 and Loutit
2
,
1979
personal communications). The existence
of
such an association
will
hardly be
surprising in
view
of
the universal occurrence of such relations.
Wessels, Wessels
& Holzapfel (1979) reported on the relationship between two lichen-
feeding Coleoptera species and Teloschistes capensis in the Namib Desert., The vast
literature that exists on such relationships has been extensively reviewed 'by Gerson
(1973) and Gerson
& Seaward (1977). According to Gerson & Seaward (1977) in-
sects, mites and mollusc constitute important components of the terrestrial fauna and
are the main lichen grazers while the Protozoa, Rotifera and Tardigrada 'belong to the
aquatic lichen-feeding fauna. The report
of
Wessels et al (1979)
is
unique in the sense
that it
is
the first report on the existence of such an association between members
of
the terrestrial fauna and lichens from an arid region.
As no tests for digestibility were carried out nor the true protein or carbohydrate
content determined, conclusions can not
be
drawn regarding the usefulness
of
these
lichen species as a food source for animals.
In
view
of
the relationships that exist
between lichens and animals
of
the Namib Desert, it is intended to pursue this
aspect further, concentrating on insect-lichen relationships as research has already
been completed.
Other low-molecular compounds, such
as
carbohydrates are reported to be abundant:
in lichens (Aspinall,
Hirst&
Warburton, 1955; Lindberg, Misiorny &
Wachtmeist~r,
1953). The carbohydrates and amino sugars that could
be,
detected
in
the three
inyi~ti
gated species are shown in Table
3.
No
attempt was madelto investigate the occtfrrence
of
polyols or polyol glycosides for which lichens are
n~ted.
Glucose, fructose and
I
I
i
i
I Mr. F. Coetzee; Nature Conservation and Tourism, P.O. Box 51, 9000 Swakopmund.
2 Mrs.
B.
Loutit;
c/o
The Senior Game Ranger, Ugabmond, Skeleton
<I:oast
Park, Private Bag 5001, 9000
Swakopmund. -
I
40
Reproduced by Sabinet Gateway under licence granted by the Publisher (dated 2012)
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