Diversity and potential role of mammals in oil palm agroecosystem (case study in PT Permata Sawit Mandiri, West Kalimantan)

The palm oil industry as the mainstay sector is still accused of being unsustainable due to the high use of chemicals as fertilizer and pest control. These inefficiencies can cause environmental damage and increase production costs. Based on these problems, it is necessary to optimize the role of biodiversity to increase oil palm productivity. This study aims to identify the diversity of mammals in several types of land cover and to analyze the role of mammals in the oil palm agroecosystem. This research was carried out on 6 types of land cover at PT Permata Sawit Mandiri, West Kalimantan in January–April 2020. Diversity data was obtained using a combination of line transects and observation points, while role data was obtained through literature study. The transect method used measuring 100 × 1000 meters is one for each type of land cover. The observations were made in the morning (06.00-08.00) and afternoon (15.30-17.30) for three repetitions each time. The results showed that there were 60 individuals from 11 species belonging to 6 families. The highest number of encounters and species variation was found in HG land cover. Mammals are one of the taxa that play an important role in maintaining ecological processes. Based on the list of mammal species in the study area, five of these species have potential roles for the oil palm agorecosystem. These roles as seed dispersers include Callosciurus notatus; Callosciurus prevostii; and Macaca fascicularis, as well as pest controllers Prionailurus bengalensis and Helarctos malayanus. The HG land cover type has a complete composisition of the roles of mammals, while in the SS land cover, no mammal species play a role in the oil palm agroecosystem.


Introduction
Palm oil is a plantation commodity that has export value and contributes to the largest source of income in Indonesia [1] ranging from 15 billion rupiahs in 2020 [2].Palm oil as one of the palm oil products is the most consumed vegetable oil in the world because it can be used in various products such as processed and cosmetic products, detergents, and lubricating foods [3].The high global demand for CPO has caused the expansion of oil palm plantations in Indonesia to increase sharply [4].The area of oil palm in Indonesia increased from 4.158 million Ha in 2000 to 11.47 million Ha in 2017 [5].The development of oil palm has proven to be able to increase people's incomes and encourage economic growth in oil palm development centers [6], as well as expanding employment opportunities for more than 16.2 million workers in Indonesia [2].
The increase in community needs is directly proportional to the increase in the amount of palm oil production.In their growth, oil palm plants require sufficient nutrients including N, P, K, Mg, and B [7].
Fertilization and pest management are factors that determine plant productivity as well as a challenge for management.Dependence on the use of chemicals as fertilizers and pesticides can increase the impact of environmental damage and production costs.According to [7], fertilization costs are approximately 30% of total production costs or 40-60% of maintenance costs.In addition, global trends have paid attention to and demanded sustainability including procedures and governance of oil palm production [8].The use of chemicals in fertilizers and pesticides in the long term can damage ecosystems, especially soil [9].
Inefficiency in using chemicals and changes in world consumer trends demand the palm oil industry to carry out environment-based management.Optimizing the role of biodiversity in the oil palm agroecosystem can be an alternative solution to increase the productivity of oil palm which is more environmentally friendly.Mammals are essential in environmental indicators in oil palm plantations [10].Mammals are taxa that maintain ecosystem dynamics and the continuity of ecological processes [11,12].Mammals help with ecological processes such as seed dispersal, pollination, predation, and decomposition [12].PT Permata Sawit Mandiri is one of the oil palm agroecosystems in Ketapang Regency, West Kalimantan with 6 types of land cover that have the potential to become a habitat for mammals.Information on the diversity and role of mammals in the oil palm agroecosystem still needs to be made available.Therefore, research on diversity and the role of mammals in oil palm agroecosystems needs to be carried out.This study aims to identify the diversity of mammals in several types of land cover and to analyze the role of mammals in the agroecosystem of oil palm plantations.

Method
The research was conducted in the plantation area of PT Permata Sawit Mandiri (PT PSM), West Kalimantan.This data collection took place for four months from January to April 2020.Observations were made on 6 types of land cover, namely young palm (SM), medium palm (SS), old palm (ST), rubber plantations (KK), and two secondary forest areas namely block F12 (HF) and block G12 (HG).The tools used include binoculars GPS, camera, camera trap, tally sheet, and tape meter.An inventory of mammals was carried out using a combination of line transects and observation points, while data on the role of mammals were obtained through literature studies.There is 1 transect line for each line cover with a length of 1 km and a width of 100 m per lane (Fig. 1).Observations were made in the morning (06.00-08.00WIB) and afternoon (15.30-17.30WIB) with three repetitions each time.The data recorded included the time of encounter, the species of mammal found, the number of individuals of each species found, and activity traces (feces, sounds, and footprints).
Data analysis includes quantitative analysis and qualitative descriptive analysis.The diversity index was calculated using the species richness index (Dmg) (1).The species richness index serves to determine the species richness of each species in each community encountered.The formula used is as follows: The evenness of mammal species in each land cover type was calculated using the evenness index (E) (2).The community similarity index shows the level of community similarity between land cover types.The formula used is as follows: The community similarity index was used to analyze the level of community similarity between land cover types in oil palm plantations with the Sorensen species similarity index (3) The number of species that are only found in community A B : The number of species that are only found in community B C : The number of species found in community A and B

Diversity of mammal species
The number of mammal species found in the PT PSM oil palm plantation area was 60 individuals from 11 species.These species are grouped into 6 families namely Sciuridae (4 species), Viverridae (1 species), Felidae (1 species), Ursidae (1 species), Cercopithecidae (3 species), and Hylobatidae (1 species).A list of the species and number of individual mammals found in the study area is shown in Table 1.The results showed that each land cover had different types and numbers of individual mammals.Based on Table 1, the highest number and types of mammals were found in the HG area (9 species), followed by HF (4 species), SM (2 species), ST (2 species), KK (1 species), and the lowest was SS (0 species).The most common species were the long-tailed macaque (M.fascicularis) and the plantain squirrel (Callosciurus notatus) with 16 individuals each.M. fascicularis is commonly found in secondary forest (HG) because it provides an abundant source of food [13].The plantain squirrel (Callosciurus notatus) and prevost's squirrel (Callosciurus prevostii) are mammals that can be found in 4 types of land cover.Both animals are tolerant and adaptive to environmental disturbances and changes and have a wide distribution and large population [14] so they can be found in both oil palm and secondary forest areas.
There are two species of mammals obtained through indirect encounters, namely the leopard cat (Prionailurus bengalensis) observed through camera traps and sun bears (Helarctos malayanus) through scratch marks.Leopard cats are nocturnal and arboreal animals [15] so they are difficult to observe directly.Sun bear claws are generally found on large-diameter trees and are used by sun bears to climb trees [16].Food and fruiting season for forage trees are important factors influencing sun bear movement [17].
The diversity of mammal species in each land cover type is proportional to the level of mammal species richness.The greater the number of species found, the greater the species richness index [18].The species richness index serves to determine the species richness of each species in each community encountered.The highest diversity and species richness index was found in the HG land cover type (H'=1.73 and Dmg=2.23),while the lowest species richness and diversity index was found in the SS and KK land cover types (H'=0 and Dmg=0).The community similarity index shows the level of community similarity between land cover types.The highest evenness index was found in the SM area with a value of E=0.97, while the HG area which had the highest number of mammal species had a lower community similarity value (E=0.79).This is because there is a dominant species, namely Macaca fascicularis.The index of diversity, richness, and evenness of mammal species in various land cover is presented in Figure 1.

Figure 1. The index of diversity, richness, and evenness of mammal species in various land cover
The variation of mammal diversity in non-oil palm areas is relatively higher than in oil palm areas.Similar results were also shown in [19] with the acquisition of species richness in oil palm areas relatively lower than in forested areas (HCV).The variation in mammal diversity can be influenced by various factors such as the diversity of species and composition of vegetation and the availability of water sources [20].The high index of mammal diversity is thought to be related to the high diversity of vegetation [11].The higher the level of vegetation diversity, the higher the diversity of mammal species [21] because the more diverse the vegetation, the higher the potential for feed vegetation [22].The SS area is an oil palm plantation area with a planting age of about 1 year.This area is surrounded by oil palm plantations, has very sparse canopy cover, and no water source is found.The diversity of mammals in oil palm land cover types is relatively low because the oil palm plantation area is a monoculture plant, so the vegetation conditions do not support the fulfillment of animal needs [23].This condition is quite different from the HG area which is a natural forest area bordering oil palm land in the north.This area has very dense vegetation conditions and is dominated by large trees and there is a water source in the form of a large river that passes through the HG area.The high level of vegetation density in this area causes the canopy cover is also high.Conditions of dense canopy cover provide a haven from predators [24].Water sources are important for wildlife.Most animals meet their water needs by drinking surface water, so the presence of water sources affects the number of species found [25].Forest ecosystems close to oil palm plantation areas protect the remaining mammal species [11] and can serve as a sanctuary for biodiversity [26].Variations in species composition were determined by the Sorensen similarity index.Community similarity is the similarity of species composition between habitats which indicates that there is a tendency for habitats to have the same species composition.The similarity value of the mammalian community in PT PSM ranged from 0-0.67.Data on the similarity of mammalian communities are presented in Table 2.The similarity value of the mammal community between habitats in PT PSM was relatively low because the community similarity index, which ranged from 0 to 0.5, was more dominant.The SM-KK and SM-HF areas had the highest similarity index of mammalian communities with the same value, namely IS=0.67.The high similarity between SM-HK and SM-HF is because the SM area is adjacent to the HCV area which has environmental conditions similar to those of HF and KK.This is following with [27] who state that the value of community similarity can be influenced by distance from adjacent locations.The high similarity value indicates that the two habitats have almost the same characteristics or are compatible with each other [28].Likewise, HG-HF has a community similarity value of 0.62.The species of mammal found in the SM, KK, and HF land cover types is C. notatus.The lowest community similarity value was dominated by all land cover types paired with SS, which was 0. This was because there were absolutely no mammals found in the SS land cover type.

The ecologic role of mammal
Mammals are a good indicator of biodiversity decline and conservation conflicts [29].Mammals are one of the taxa that play an important role in ecosystem dynamics [12] and maintain the continuity of ecological processes [11].Mammals occupy the level of consumers I and II and the apex predators in the food chain [30].Mammal species that have the potential role for oil palm include Prevost's squirrel (Callosciurus prevostii), plantain squirrel (Callosciurus notatus), long-tailed macaque (Macaca fascicularis), leopard cat (Prionailurus bengalensis), and sun bear (Helarctos malayanus).
Based on the list of potential mammal species, three species have the potential to be seed dispersers, including Prevost's squirrel (C.prevostii), Plantain squirrel (C.notatus), and long-tailed macaque (M.fascicularis).Prevost's squirrel is a species of mammal found in four land cover types: SM, ST, HG, and HF.Plantain squirrel can also be found in four land cover types: SM, KK, HG, and HF.Both species use oil palm fruit and insects as feed sources [31,32].Other studies have also shown that long-tailed macaque eat oil palm fruit.Although only found in secondary forests, long-tailed macaque has a wide range of food [33], so it is possible to benefit from palm kernels as a source of feed [14,32].Animals greatly help the mechanism of natural seed dispersal, with seeds that are ingested or swallowed and then spread through the feces of the animal [34].Seeds removed through feces generally germinate faster due to the help of gastric juices which can soften the hard seed coat [35].
Leopard cat (Prionailurus bengalensis) and sun bear (Helarctos malayanus) are mammals found indirectly but have a potential role as pest control in oil palm plantations.Concerning the food chain, the presence of leopard cat act as a predator in oil palm plantations [36].The leopard cat is a carnivorous mammal that feeds on rats, lizards, frogs, birds, and insects [14].The rat species responsible for damage in oil palms is the wood rat (Rattus tiomanicus) which lives on the ground-nesting in the piles of old fronds cut from palms, or in the crowns [37].Sun bear (H.malayanus) is an omnivore eating plants and animals such as termites (Isoptera) as well as beetles and beetle larvae (Coleoptera) [17].Horn beetles or Oryctes rhinoceros (Coleoptera: Scarabaeidae) are one of the main pests for oil palm plants [38].This pest attacks the leaf blades at the point of growth and kills the tops of the plant so that it can reduce oil palm production [39].Omnivore ✓ Table 3 shows the HG land cover type has a complete composition of potential mammals.Secondary forest cover has a higher level of vegetation diversity than other land covers, so the potential for feed trees for mammals is relatively more abundant.In addition, HG blocks have very tight vegetation conditions and can act as corridors, covers, and shelters suitable for mammals.These conditions are hugely different from the SS land cover type.Potential mammals are not found in SS land cover because the SS land cover has less favorable habitat conditions for mammals.After all, this area is surrounded by oil palm plantations, so vegetation conditions tend to be homogeneous.
Mammals that have the potential role of seed dispersers are scattered in the land cover of SM, ST, KK, HG, and HF.Squirrels (Callosciurus sp.) can be found in SM and ST land cover because the block is adjacent to the HCV area.Mammals that have a potential role as pest controller are found in the land cover of ST and HG.Leopard cat is found in the ST block because the block has a higher potential for rat pest attacks than the SM and SS palm blocks.The wood rat feeds on bunches of emerging fruit and fruit that fall to the ground when ripe [37].The availability of prey animals influences the presence of predators in oil palm plantations [14].Meanwhile, traces of sun bear activity are found in HG land cover because the variety of feed in the block is abundant.
Table 3 also shows a potential for using oil palm plantation ecosystems as mammalian habitats even though they are not their primary habitat [40,41].The existence of forests with complex vegetation structures around oil palm areas, such as secondary forests of HG and HF blocks and HCV areas, plays an essential role in preserving mammalian species diversity [10].Stable secondary forests affect biodiversity conditions for other adjacent ecosystems.

Conclusion
The diversity of mammals in PT PSM consists of 60 individuals from 11 species belonging to 6 families.The highest number of encounters and species variation was found in HG land cover, while the lowest was in SM land cover.There are two potential roles for mammals, specifically seed dispersers and pest controllers.The HG land cover type has a complete composition of the roles of mammals, while in the SS land cover, no mammal species play a role in the oil palm agroecosystem.

Table 1 .
Number of species and individuals of mammals *=indirect encounter (activity traces)

Table 3 .
Potential mammals and their distribution by land cover type