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In oil palm, damage is not confined to fruitlets alone: the shoots of young palms are also occasionally devoured in nurseries and replants where there is an established population in mature palms (Wood et al., 1970). C. notatus has also been observed to secure strips from oil palm fronds for nest material (Hafidzi, 1992). Attacks on cocoa are directed on the pods where the squirrels feed on the cocoa mucilage that surrounds the seeds (Han and Bose, 1978; Kamarudin and Lee, 1981). However, young cocoa plantings may also be affected by the bark stripping behaviour of this species which kills some of the yearlings (Hafidzi, 1992). Bark stripping has also been recorded on young rubber plantings (Edgar, 1958; Harrison, 1962; Barlow, 1978).
Generally, populations stabilise at much smaller numbers than those of rats. In plantations this limits the extent and severity of the damage potential. It is chiefly small orchards and isolated fruit trees that can sustain severe devastation, up to complete loss of production. There is no one effective method of dealing with C. notatus. Trapping and shooting are the two traditional means of dealing with the pest. The former is labour-intensive and of doubtful effectiveness because C. notatus is difficult to trap (Han, 1982), and the latter is not cost-effective and only works on a short-term basis as squirrels are introduced as quickly as they are removed.
To date in the environments where C. notatus is a pest, biological control by manipulating natural predators has only been practised against rats (e.g. rearing of barn owls, Tyto alba, to control rat infestation in oil palm).
Sanitary measures such as pruning and removing fronds may provide limited control of an infestation; destroying nests may also have this effect.
C. notatus is one of two important vertebrate pests of cocoa in Peninsular Malaysia (Han and Bose, 1978; Han, 1982; Kamarudin, 1984), the other being the wood rat, Rattus tiomanicus. Although R. tiomanicus has been ascribed as the most important pest of cocoa, cage trials indicated that C. notatus can inflict twice as much damage as the rat (Han and Bose, 1978; Kamarudin and Lee, 1981). These feeding studies in captivity showed that C. notatus has between three and fives times the potential to attack cocoa than R. tiomanicus.
C. notatus may cause extensive damage, especially near forest fringes and areas fringing or contiguous with oil palm plantations in which it has become fully adapted (Duckett, 1982). Damage can vary from less than 5% to almost 100% loss depending on the areas of planting, season and crop yield (Conway, 1971; Han and Bose, 1978). C. notatus has also been reported to attack cocoa yearlings by bark stripping; the damage documented in one such case was >50% (Hafidzi, 1992).
C. notatus has been established to be a major vertebrate pest in oil palm (Duckett, 1982; Ng and Khoo, 1982; Hafidzi, 1993c). There are no reports documenting the extent of damage caused by C. notatus to oil palm due to the difficulties in distinguishing between damage caused by squirrels and that caused by rats (Wood, 1968). Evidence from the field indicates that oil palm makes up a substantial portion of the squirrel's diet (Hafidzi, 1993c).