Good seed dispersers

Knowing the primates’ movements and their preferences for certain fruit species was a good first result. Yet this did not yet tell us anything about the effectiveness of the species in terms of seed dispersal. Like most macaques, the  “pig-tails” possess cheek pouches (pouches where the fruit can be stored before being consumed, a bit like a hamster) and three seed processing techniques: ingestion (followed by defecation), spitting out and finally, dropping them after manually opening the fruit. “A good seed disperser is an animal that consumes numerous fruits and which regularly goes toward trees bearing ripe fruit thus ensuring a high reproduction rate. However, these advantages can be nullified in the case where, for example, the gastric juices compromise the germination potential of the seeds or if they are dispersed in an inadequate environment unsuitable to germination”, explains the researcher.  Due to a lack of sufficient numbers of seeds of all fruit species consumed by the macaques, Aurélie Albert concentrated the germination tests on 21 species which ensured a sufficiently large diversity of seeds, from the very smallest to the longest, to be representative of what is to be found in the forest.


Many facts were discovered. Each northern pig-tailed macaque can disperse tens of thousands of seeds in one single feces. In addition, they can disperse large seeds by dropping or spitting, some of these reaching 58 millimeters in length. Thanks to the three techniques used by the primate to process the seeds when ranging, the primate can disperse them from primary to secondary forests. Moreover, for 14 of the 21 species tested, the passage through the digestive tract has a neutral or even positive effect on the germination and viability of seeds. All these observations lead Aurélie Albert to say that this species unquestionably satisfies most of the requirements to be defined as an effective seed disperser both in terms of quantity and quality. “Finally, more than being simple seed dispersers, pig-tailed macaques can play an important role in forest regeneration. Indeed, far from restricting itself to primary forests, they also accessed secondary forests which were damaged by various kinds of human activity. This distinguishes them from most other frugivores which are incapable of using treefall gaps and open habitats”.