The potential of wildlife diversity and possible roles in oil palm agrosystem management: case study in Riau province

The use of chemical fertilizers and control of pests/diseases and weeds in the management of oil palm plantations, besides causing very high production costs, is also feared to have a negative impact on the environment. Therefore and in the context of fulfilling the world community’s demands, “management of oil palm plantations that optimize the use of biodiversity” is a non-negotiable decision choice. This paper is a synthesis of research that has been carried out in 8 oil palm plantations spread across the provinces of Riau. The results showed that in the oil palm agrosystem found between 3 - 9 species of mammals (Macaca fascicularis; Macaca nemestrina, Presbytis cristata, Prionailurus bengalensis, etc.). The potential roles of several types of mammals are as pollinators (Callosciurus notatus); as seed dispersers (Paradoxurus hemaphroditus), and as pest control (Prionailurus bengalensis). Further research is needed to examine the role of each mammal species in oil palm agrosystems.


Introduction
One of the sectors in Indonesia with tremendous growth potential is the palm oil industry.According to estimates, Indonesia's oil palm plantations will cover 15.081.021ha by 2021, an increase of 0.91% yearly [1].Because it may increase the value of national exports, the palm oil sector is one of Indonesia's most important economic sectors.The amount of palm oil produced is directly proportional to the rise in community requirements.The management challenges of fertilization and pest control affect plant productivity.Dependence on chemical fertilizers and pesticides can have a more significant negative impact on the environment and raise production costs.[2] estimates that fertilization costs about 30% of the overall production cost or 40% -60% of the maintenance cost.Global trends have also demanded sustainability, which includes policies and governance surrounding the development of oil palms [3].Long-term usage of chemicals in pesticides and fertilizers can harm ecosystems, especially soil [4].
Another problem that affects oil palm plantations in Indonesia is that there are still high allegations that oil palm plantations can cause a decrease in biodiversity, especially biodiversity.In addition, the international community already wants the implementation of environmentally friendly oil palm plantations.The changing view of the world's consumers requires a more environmentally friendly palm oil production system.Optimizing biodiversity's roles, especially mammals in oil palm agroecosystems, could be a different approach to meet these issues.Mammals are one of the taxa that play critical roles in food webs and provide numerous ecosystem services such as seed dispersal, pollination, predation, and decomposition [5].The role of mammals in oil palm plantations is currently unknown, but several plantations use mammals as pest control.The ecological role of mammals is the primary key to explaining the ecological sustainability of oil palm plantations.Therefore, state-of-the-art research on mammalian diversity and its function in agroecosystems are essential as the scientific basis for planning biodiversity in oil palm plantations.Then, it is crucial to analyze the role of mammals in the agroecosystem of oil palm plantations.

Method
This study was conducted in 8 oil palm plantations located in Riau province.Data on mammal species diversity were obtained through direct observations and indirect encounters using GPS, binoculars, cameras, camera traps, tally sheets, and animal traps are used.Line transects and observation points were used to count the mammals.Each line cover has a single transect line that is 1 km long and 100 m wide (Fig. 1).With three repeats each; observations were conducted in the morning (06.00-08.00WIB) and the afternoon (15.30-17.30WIB).The data recorded included the date and time of the encounter, the types of mammals observed, the quantity of each species, and activity traces (feces, sounds, and footprints).After obtaining data related to the diversity of mammal species on the plantation, the potential role of each species was collected based on literature review (journals, publications, etc.).Thepotential roles are also categorized based on trophic level.

Figure 1. Line transect method
The diversity of mammal species found in the study site was then analyzed using several indexes.The species diversity index (H') (1) and species richness index (2) were used to calculate the diversity index (Dmg).The species richness index is used to calculate how numerous each species is in each community where it is encountered: Furthermore, the evenness index (3) was used to determine mammal species within each location (E).The community similarity index reflects the level of community similarity between various location.The results showed that each location had different species and numbers of individual mammals.Based on Table 1, the highest number and species of mammals were found in the 1 st location (6 species-43 ind), followed by 8 th location (5 species-14 ind), 5 th location (5 species-11 ind) and the lowest was 2 nd location (3 species-4 ind).The Bornean bearded pig (S. barbatus) and the plantain squirrel (Callosciurus notatus) were the most common species.Sus barbatus were found in 5 oil palm plantations, which is 63% of all location studies.The plantain squirrel (Callosciurus notatus) is species that found in 6 oil palm plantations.Both animals are tolerant and adaptive to environmental disturbances and changes and have a wide distribution and large population [6].They can be found in both oil palm and secondary forest areas.
The leopard cat (Prionailurus bengalensis) was observed through camera traps.Leopard cats are nocturnal and arboreal animals [7], so they are difficult to observe directly.Each location's mammal species diversity and mammal species richness are inversely correlated.The species richness index rises as the number of discovered species do [8].The species richness index calculates how numerous each species is in each community where it is encountered.The 5 th location had the highest diversity and species richness index (H'=1.55and Dmg=1.67),whereas the 7 th location had the lowest diversity and species richness index (H'=1.04and Dmg=1.4).Furthermore, the 2 nd location had the highest evenness index, with a score of E=0.95, while the 7 th area had the lowest.This is because Macaca fascicularis is the dominant species.Figure 1 shows each location's mammal species diversity, richness, and evennessindex.

Figure 2. The index of diversity, richness, and evenness of mammal species in various location
Numerous variables, including the variety of plant species, their composition, and the accessibility of water sources, can impact the variation in mammal diversity [9].The high diversity of flora is assumed to correlate with the high animal diversity index [10].The diversity of mammal species increases with the level of vegetative diversity [11] because more diverse flora has tremendous potential as a source of food [12].Because Oil palm plantation is a monoculture plants, and the vegetative circumstances do not allow the fulfillment of animal needs so the diversity of animals in oil palm plantations is relatively low [13].Water availability is critical for wildlife.Because surface water is the principal water supply for most animals, the availability of water sources influences species diversity [14].Forest habitats near oil palm plantation areas conserve the surviving animal species [10] and can serve as a refuge for biodiversity [15].

The ecologic role of mammal
Mammals are one of the taxa that play an essential role in ecosystem dynamics and maintain the continuity of ecological processes [10].Mammals occupy the level of consumers I and II and the apex predators in the food chain.Mammal species that have the potential role for oil palm include plantain squirrel (Callosciurus notatus), long-tailed macaque (Macaca fascicularis), and leopard cat (Prionailurus bengalensis).
Leopard cats, or Prionailurus bengalensis, are mammals found in oil palm plantations and may serve as a pest management measure.Regarding the food chain, the leopard cat's presence in oil palm plantations acts as a predator [16].Rats, lizards, frogs, birds, and insects are among the carnivorous animals that the leopard cat eats [6].The wood rat (Rattus tiomanicus), which nests in the heaps of old palm fronds that have been cut off or in the crowns of the palm trees, is the rat species that cause harm to oil palms [17].Mammals were essential predators of artificial caterpillars.Predation by mammals was considerably higher in fruit orchards and rubber trees than in oil palm plantations, likely due to their ability to support higher abundances of insectivorous mammals [18].
According to the list of potential mammal species, such as C. notatus, M. fascicularis, Tupaia splendidula, Macaca nemestrina, Presbytis cristata, and Paradoxurus hermaphroditus have the potential role to be seed dispersers.C. notatus and Tupaia splendidula feed on oil palm fruit and insects 1243 (2023) 012003 IOP Publishing doi:10.1088/1755-1315/1243/1/0120035 [19].Long-tailed macaques have been observed eating oil palm fruit in other studies.Because longtailed macaques have an access to various foods, palm kernels may be useful for food [6] [19].Animals contribute significantly to the natural seed distribution system by ingesting or swallowing seeds, which are then dispersed by the animal's excrement [21].Because stomach acids can weaken the harsh seed coat, seeds expelled through feces germinate faster [22].
Long-tailed macaques have been observed eating oil palm fruit in other studies.Because long-tailed macaques have access to various foods, palm kernels may be useful for food [6] [19].Animals contribute significantly to the natural seed distribution system by ingesting or swallowing seeds, which are then dispersed by the animal's excrement [21].Because stomach acids can weaken the harsh seed coat, seeds expelled through feces germinate faster [22].Furthermore, mammals such as Callosciurus notatus and Macaca fascicularis have the potential to be pollinators.This species can be found in nearly every research facility.Several studies have been carried out to determine the role of both in plantations.However, more research on the subject is required.Squirrels (C.notatus), macaques (M.fascicularis), and other mammals are known to feast on flowers, particularly durian blooms.However, these two species fed devastatingly.C. notatus may easily move from one tree to another by exploiting closely spaced branches as bridges.Flower corollas were likely damaged due to C. notatus pecking holes into the flower bases to extract nectar.As a result, this species is often known as a pollinator.Callosciurus notatus was diurnal, with most interactions with flowers occurring between mid-morning and mid-afternoon [23].The composition of mammals in the oil palm agrosystem is different.The composition of mammals based on potential roles is explained below:

Ecological roles Species Location
Table 3 shows that the 5 th , 6 th , and 8 th location have a complete composition of potential mammals.Because this location has a secondary forest cover with a higher level of vegetation diversity than other land covers, the potential for mammals feed trees is relatively more abundant.In addition, that location has very tight vegetation conditions and can act as corridors, covers, and shelters suitable for mammals.Mammals with the potential role of seed dispersers are scattered in the study area, containing various species.
Even though oil palm plantations are not mammals' principal habitats, Table 3 demonstrates the potential for utilizing them as such [24].The richness of mammalian species depends on the presence of forests with complex vegetation structures near oil palm plantations, such as secondary forests and HCV areas [25].Stable secondary forests impact other nearby ecosystems' biodiversity conditions.
species N : Total number of individuals of all species

Table 1 .
Number of species and individuals of mammals Muridae (1 species), Tupaiidae (1 species), Sciuridae (1 species), Suidae (1 species), and Viverridae (1 species) are the families that these species belong to (1 species).Table1lists of the species and the number of individuals found in the study area.