Fruit-frugivore interactions in a Malagasy littoral forest - Universiteit ...

Chapter 3
dominant plant families seemed to be represented in the diets as represented in the
overall sample. The same is true for growth form (Table 3). Most consumers favour
berries and drupes, but for rodents there was a trend for selecting drupes. Even though
soft and juicy fruit made up most of the sample, nocturnal lemurs and flying foxes
selected this pulp type significantly more often than other pulp types. The latter also
favoured arillate fruits (Table 3). For colour a selection was noticed towards red and
purple fruits by all frugivore bird species, whereas mammals ate whatever colour was
available. Most fruits in the littoral forest had an odour and were probably selected in this
way, except for Coracopsis nigra, which fed mainly on odourless fruits (Table 3). For the
nocturnal lemur species fruits with a thin husk were favoured. The other consumers did
not seem to avoid the few dehiscent and thick-husked fruits present (Table 3). In all
animal species no difference in seed protection could be found between diet and the
overall dataset (Table 3). The few preferences indicated above appeared to be nonsignificant
after correction by sequential Bonferroni.
Flying foxes were the only consumer species, which preferred multi-seeded fruits,
while the diet of the other animals did not differ from what was available (Table 4). Initially
many significant preferences could be found related to fruit and seed size and weight.
However after sequential Bonferroni adjustment, only the frugivorous birds seem to select
significantly smaller and lighter fruits. Coracopsis nigra also prefers lighter fruits and
Pteropus rufus smaller seeds. Contrarily the rodents clearly favour heavier fruits and
larger seeds. (Table 4).
Biochemical Characteristics
Water was the dominant constituent of fresh pulp (median 76.0%). On a dry mass basis,
both acid (22.6%) and neutral (32.0%) detergent fibre contents were high. The median
sugar content was 19.2%. Median lipid content of fruits was 3.1%, total nitrogen 0.9%,
and extractable protein 2.8%. Tannin values were very low in our dataset with a median
value of 0.2%. Enzymatic analyses of all fruits yielded median values of 3.6%
saccharose, 1.8% glucose, and 1.8% fructose.
As for fats, frugivorous birds seemed to select fruits with a high lipid content, while
the opposite was true for E. f. collaris and P. rufus (Table 4). Neither total nitrogen nor
extractable protein seemed to influence fruit choice for any of the consumer species, nor
did water content or acid detergent fibre. Cheirogaleus spp. and Microcebus rufus
selected fruits with high sugar content but this trend was not significant (Cheirogaleus
spp. P=0.06, M. rufus P=0.19). However when looking at saccharose, glucose, and
fructose concentrations separately, preferences were significant for Cheirogaleus spp.
(Table 4). The same trend existed for M. rufus (saccharose P=0.17, glucose P=0.11,
fructose P=0.056). Tannins were consumed as present in the overall database but
Coracopsis nigra included fruits with significantly higher tannin content. In the diet of M.
rufus neutral detergent fibre was significantly lower than in fruits, which were not
consumed (Table 4). None of these preferences remained significant after sequential
Bonferroni adjustment.
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