No 8 - Endangered Wildlife Trust

Page 4
Conflict in the Karoo with Blue Cranes and agricultural lands
Bradley Gibbons
The Blue Crane Anthropoides paradiseus is a near-endemic to South Africa. Although the largest population is
found in the transformed wheat field / pasture mosaic found in the Western Cape, the Karoo population of Blue
Cranes is the largest population within a natural area with a combination of Karoo shrubs and grass (McCann
2000). Since 2005, there have been 25 complaints of Blue Cranes found on agricultural lands in the Karoo (and
one complaint included three agricultural lands). There have also been over 30 farmers who have had cranes
on their agricultural lands, but have not had problems. In fact, most of these farmers have reported that cranes
are beneficial to their lands, because of the insects and worms that are eaten by the cranes. Many of these
farmers have seen no damage as a result of the cranes being in the lands. These farms are visited very often in the
Karoo and are important to the Karoo Crane Conservation Project. One farmer has stated that he obtains a
better yield from the lucerne land where the cranes occur than the land adjacent to it where the cranes do not
visit. An additional three farmers have cranes on their lands every year, but are uncertain about their impact
and have not complained. Most of the farmers (19 of the 25 farmers) have complained about cranes found on
lucerne lands, but there have also been complaints about cranes on maize lands (3 farmers). The complaints
on maize lands are during the growing season, mainly a three week period when seeds have been sown as
well as in the late winter months where stubble remains in the lands, because these farmers want their sheep to
eat the stubble and not the cranes. Other lands where complaints have been received have been on rye lands
(two farmers) and ‘korog’ lands (one farmer), which is a mixture of wheat and rye. A visit was made to each
farmer by the EWT Field Officer, following each complaint. Two methods to reduce the presence of cranes on the
agricultural lands were presented to the farmers and in most instances, were installed by the Field Officer. These
included the use of chevron or danger tape fastened to the top of several fence droppers within the lands. The
fence droppers are placed in the rows with a spacing of 20 metres if possible (it depends on the size of the land,
as they could be spaced 30 metres apart in larger lands). There are between 15 and 30 fence droppers in total
used at each land. When the wind blows, the danger tape frightens the cranes with the sound it makes and the
colours. The second method is a gas cannon that makes an explosion to scare the cranes that has also been
used on large lands. There is one cannon used in the Karoo and it is made up of two cannon components that
blast. The explosion happens approximately every 10 seconds and farmers are told to only put it up when the
cranes are on the lands (and turn it off when there are no cranes).
However, damage by cranes has not been observed by the EWT Field Officer, but there has been damage
observed as a result of Kudu Tragelaphus strepsiceros, Steenbok Raphicerus campestris, and Duiker Sylvicapra
grimmia, where lucerne has been grazed by these mammals. Porcupines Hystrix africaeaustralis have also
uprooted lucerne. This can be seen where they have dug large holes around the plant. Egyptian Geese
Alopochen aegyptiaca and Spurwinged Geese Plectropterus gambensis have been seen feeding on lands
where Blue Cranes are also found and trampling and feeding damage has been observed, but not in the same
quantity as Kudus (pers. obs.). While visiting lucerne lands, it has also been possible to see bulbs from the
bulbous plants such as ‘uintjies’ (Cyperus spp.) found between the rows of lucerne that have been dug out by
the cranes. These plants are often found naturally in these areas and are not planted by farmers. These bulbs
are also not regarded as valuable to farmers (pers. obs.).
A stomach from a crane (that was entangled in a fence surrounding a lucerne land) was cut open with the help of
staff from Grootfontein Agricultural Institute in Middelburg, Eastern Cape, but no lucerne was found in its stomach.
Blue Cranes are omnivorous and mainly eat seeds, insects (such as locusts, caterpillars, and termites), bulbs,
worms, reptiles, small mammals, fish, frogs and crabs (Allan 2005). They feed mainly by pecking or digging in the
soil. Stomachs of 37 Blue Cranes in the Overberg were cut open and maize, lucerne and other vegetable matter
were found in the stomachs (Allan and Ryan 1996). It is not known if Blue Cranes eat more vegetable matter or
animal matter (Allan and Ryan 1996). The Blue Crane stomach study done by Allan and Ryan (1996) showed that
cranes do eat lucerne in the Overberg of the Western Cape. Egyptian Geese are known to feed on vegetable matter
including lucerne (Davies and Allan 2005) and Spurwinged Geese have also been known to eat lucerne (Colahan 2005).
Complaints of trampling by cranes in the Karoo have also been reported, but this has only been seen on short
lucerne (less than 10cm) and not in lucerne lands with tall lucerne (over 20cm) (pers. obs.). With the weight of a Blue
Crane varying from 4.6 to 5kg (Allan 2005) and the weight of Kudus varying from 112 to 268kg (Skinner and Smithers
1990), it would be assumed that Kudus will have more impact by trampling than cranes. A farmer in the Karoo put
up a high fence on his farm in order to exclude Kudus. He has recorded the amount of lucerne produced on these
lands before and after the fence was put up and has reported that he is now getting three times the yield of lucerne.
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