Habitat fragmentation is a word that makes most conservation biologists or any biologically inclined animal lover cringe. It carries with it the baggage of deforestation, industrialization, species extinction, etc., and is seen as largely detrimental to the survival of many species. However, some species have found temporary ways of adapting by changing their behavior, diet, or physical appearance. A recent study by Boyle et al. of Rhodes College found that habitat fragmentation influences the dietary consumption and quality of the bearded saki monkey (Chiropotes chiropotes) in the Brazilian Amazon. In comparison to populations that inhabited non-isolated fragments and continual forests, the populations in small fragmented areas had a flexible and diverse diet which included food items that were ignored in the larger habitats.
Changes in plant species richness, composition and diversity of plant communities in small areas are largely due to habitat fragmentation. This shift directly impacts the diet of the species within that habitat by altering the amount of available resources. The bearded saki monkey’s diet is made up of approximately 88% fruits and seeds, and therefore the plant composition of forest fragments plays a significant role on their diet. The solution to surviving in a fragmented habitat may appear contradictory at first. It would seem that having a smaller habitat with decreased plant diversity would restrict the saki’s diet. On the contrary, the decrease in habitat range results in a broader and more diverse diet. Since the plant composition is limited in fragmented areas bearded sakis do not have the luxury of only eating the foods they like because there is simply not enough to go around. Instead they must learn to like a larger variety of foods in order to survive in these smaller habitats.
In order to determine the extent to which plant composition has on the bearded saki’s diet, Boyle and her colleges conducted their study at the Biological Dynamics of Forest Fragments Project (BDFFP). This study site contains a variety of habitat sizes that range from 10 hectares(ha) to continuous areas of forest, and within these habitats there are distinct differences in the diversity and composition of plant species. Boyle et al. followed 6 groups of bearded saki’s spread across habitats of different sizes (2 groups in completely isolated 10-ha, 2 groups in non-isolated 100-ha, and 2 groups in continuous forest) and monitored their dietary intake over several days. The researchers observed that on 10-ha fragments no young juveniles or infants were present during the study which suggests that resources are very limited in habitats of this size. They also found that the more abundant a plant species was in the area the more prominent it was in the monkey’s diet, which shows that the plant composition of the area does have an effect on diet. Moreover, bearded saki’s in fragmented habitats were found to primarily consume the un-ripe fruit of the plant Protium hebetatum, a species that saki’s in non-isolated habitats and continuous forest ignored, even though it was abundantly present in their habitat s as well. Bearded saki’s on larger habitat fragments and on some islands can be found to eat Protium; however, they will only consume ripened fruit that is more nutritious.
It is clear that habitat fragmentation impacts the plant composition of isolated forest fragments and has driven the bearded saki to include in their diet fruits and seeds that would be ignored by individuals with a larger range. These less preferred fruits allow the saki to thrive in small fragments, but in the long run a broad diet may not be enough. A change in abundance of plant species of plant species that shifts towards an increase in inedible fauna would further limit the available resources and greatly impact the survival of the bearded saki. In order to provide long term success for the bearded saki there must be an increase in connectivity between the isolated fragments and the surrounding forest. Expanding their range would expose them to more resources allowing preferred and nutritional fruit to be the primary components of their diet.
By: Maya Carrillo
Source Article: Boyle, Sara A., Zartman, Charles E., Spironello, Wilson R., and Smith, Anrew T. (2012). Implications of habitat fragmentation on the diet of bearded saki monkeys in central Amazonian forest. Journal of Mammalogy . 93(4):959-976