Rattus Tiomanicus Research Articles

Effectiveness of using the trap barrier system to control rats in palm oil plantations

Abstract. Efriansyah, Priyambodo S, Hindayana D. 2024. Effectiveness of using the trap barrier system to control rats in palm oil plantations. Biodiversitas 25: 2993-2998. Oil palm is one of the plantation crops that is the largest contributor to the country's income; increased market demand affects palm oil production, which continues to increase. Rats are among the most important pests in oil palm plantations because of their diverse habitats, large populations, and easy breeding. One of the mechanical control concepts that can be implemented is the Trap Barrier System (TBS) technique. This research method was implemented by installing a trap barrier between oil palm trees. This TBS research is divided into two methods. The first method used three treatments with three replications in the main plot, and there were three main plots. The second method used nine treatment sub-plots with three replications. The Ciliwung variety of rice was planted inside the TBS in a 3 m x 3 m plot. Field observations included the number of rats caught and the percentage of damage done at the trial's beginning and end. Species of rats found in oil palm plantations are Malaysian field rat (Rattus tiomanicus Miller, 1900), oriental house rat (Rattus tanezumi Temminck, 1845), and dan müller's giant sunda rat (Sundamys muelleri Jentink, 1879). The S. muelleri was the most frequently caught species in each block and method. TBS placement does not need to pay attention to the initial severity of the block. Providing additional bait in traps can increase the attraction of rats to TBS. The extent and intensity of attacks and yield losses in each block with TBS treatment showed a greater reduction than in blocks without TBS.

Surveillance of pathogenic Leptospira among rodents and small mammals in enzootic areas of plague in Pasuruan Indonesia

Leptospirosis is a globally significant yet often overlooked zoonotic infection. Several regions in Indonesia are endemic for leptospirosis, including East Java. Pasuruan a region located in the East Java province of Indonesia, has been recognized as an enzootic area of plague infection. However, the presence of other rodent-borne diseases has not been reported. This study aims to detect the presence of pathogenic Leptospira in rats and small mammals in the enzootic plague area of Pasuruan in Indonesia. This study belongs to the type of observational analytic research with a cross-sectional study design. Simple random sampling was conducted to trap a total of 119 forms 107 rats and 12 small mammal kidneys were analyzed molecularly (PCR) to detect Leptospira bacteria with the LipL32 gene as the target. The study revealed that 7.6% (9/119) of rats in the enzootic areas of plague (Sedaeng, Tosari, Surorowo, Petren, Pakis Bincil, Kutukan) were found to carry Leptospira DNA, indicating a significant difference between infection rates per region (p < 0.0001). Rattus tanezumi was identified as the Leptospirosis reservoir in settlements habitats with a percentage of 13.2%, Rattus tiomanicus was detected at 28.6% in forest habitats, and Rattus exulans was found at 4.4% in both habitats. The findings in our study, it is crucial for the community to increase awareness of the spread of rodent-borne diseases, including Leptospirosis.

Specific PCR primers for rapid detection of five rat and mouse species in Java, Indonesia

Identifying rat and mouse species quickly, affordably, and accurately is crucial for effective population management, as well as for eradication or conservation purposes. However, the sheer diversity of these species poses a challenge. To address this, a molecular approach has been developed, involving the amplification of a short genetic marker from materials commonly left by the animal, such as hairs and feces. Recent available PCR primers were not suitable for the surveillance of large sample sizes. As a solution, this study designed and validated a PCR primer set capable of detecting five species of rats and mice (Mus musculus, Rattus tanezumi, Bandicota indica, Rattus tiomanicus, and Rattus argentiventer) commonly found in Java, Indonesia. The specific primers were derived from the cytochrome c oxidase subunit 1 (COI) gene, designed using the SP‐Designer V7.0 application, and validated using both in silico and in vitro methods. The validation results demonstrated that all five pairs of primers were highly specific, generated correct amplicons, and successfully detected the five distinct species present in a Javan mongoose feces sample. These findings are significantly important as they enable the effective detection of rat and mouse species and potentially provide valuable ecological insights from the field.

DETEKSI YERSINIA PESTIS DAN PATOGEN ZOONOTIK LAINNYA PADA TIKUS DI DAERAH FOKUS PES DESA KAYUKEBEK KABUPATEN PASURUAN

Rats are known as carriers and transmissions of zoonotic diseases. About 60 types of zoonotic diseases that rats can transmit to humans. Some zoonotic diseases are Plague, Leptospirosis, Orthohantavirus infection, and Hepatitis E virus. This research aims to detect the bacteria Yersinia pestis, Leptospira, Hepatitis E virus, and Orthohantavirus in rats in Kayu Kebek Village, Pasuruan Regency. The research design used in this study is descriptive with a cross-sectional approach. The rats were captured for three days, two nights in the house, the neighborhood around the house, and the forest. The captured mice were identified as specimens of blood, spleen, kidneys, and liver. Detection of Yersinia pestis, Leptospira, and Hepatitis E is performed using PCR, while the detection of Orthohantavirus is performed using the ELISA method. A total of 45 mice were trapped, consisting of 2 genera and three species. The zoonotic pathogens detected were Leptospira and hepatitis E. Leptospira viruses were detected in Rattus tanezumi, Rattus tiomanicus, and Niviventer fluvescent. Hepatitis E virus is detected only in R. tanezumi. Transmission of leptospirosis and hepatitis E has the potential to occur in Kayu Kebek Village. Rat control is needed to prevent the transmission of leptospirosis and hepatitis E virus infection, and other zoonotic diseases transmitted by rats.

Preliminary checklist on species composition of small mammals and birds in Marine Research Excellence Centre (MAREC), Pulau Tuba.

Located in Langkawi archipelago, Andaman Sea, Pulau Tuba is one of the islands that is densely protected as a forest reserve. We investigated and documented the species composition of small mammals and birds at two different sites in the forest of UiTM Marine Research Excellence Centre (MAREC). Wire cage traps were used to capture non-volant small mammals while mist nets were used to capture bats and understorey birds. A total of 35 individuals were captured consisting of four species of small mammals and four species of birds. Among the most abundant species captured were Rattus tiomanicus, Leopoldamys sabanus and Cynopterus brachyotis. The calculated Shannon diversity index was 1.58 indicating a low diversity of small mammals and birds within the area. Our current study stipulated that few individuals were caught due to the rainy season affecting Pulau Tuba during the study period. Further surveys and studies should be conducted for a longer period in different seasons so that more species of fauna can be documented.

Rat composition and population in mature oil palm adjacent to paddy field

Rat is one of the main pests in an oil palm plantation, impacted at various types and stages of oil palm growth. Ungkaya estate has a historical & endemic infestation of rats, especially in several fields adjacent to paddy fields. This study aimed to find out the seasonal migration of rats from paddy fields to oil palm fields in Ungkaya Estate. Five plots were used for trapping, identifying rat species, monitoring of rat population, rat damage intensity, and rat habitat preference at each stage of the paddy season. Trapped rats were identified as Rattus tiomanicus (56.91%), Rattus argentiventer (36.17%), and Rattus tanezumi (6.91%). The intensity of rat damage to the palm was high during the vegetative phase of paddy season and the full moon phase. The regression analysis results showed that the number of trapped rats has a positive relationship to rat damage intensity for the vegetative and harvesting stage at full moon. The number of trapped R. argentiventer at vegetative stage was higher than the generative & harvesting phase of the paddy season. Moreover, there were rat footprints observed on the riverside leading to the oil palm field. The results of all observation parameters concluded that there was seasonal migration of rats between the oil palm fields and the paddy fields in Ungkaya estate. The information is pivotal in drawing up suitable mitigation measures to control and minimize rat damage to the oil palm.

Feed Preference Tests of Carbohydrate, Protein, and Rodenticide to Tree Rat, House Rat, and Rice Field Rat

Rats are wild animals that coexistence with humans. The losses caused by these rats are damage to house building, agriculture, and plantation. Knowledge of the feed as bait and lure is very important in rat control, particulary with rodenticides and traps. The aim of this research was to find out feed preference to three species of rats and effect of feed availabili-ty toward rodenticide consumption. Tree rat (Rattus tiomanicus), house rat (R. tanezumi), and rice field rat (R. argentiventer) were tested with four stages i.e. (a) type of carbohydrate sources, (b) type of protein sources, (c) combination of carbohydrate and protein, and (d) carbohydrate, protein, and rodenticide. The method used was choice test. Carbohydrate tested were corn, rice, unhulled rice (grain), and oat. Protein were cricket, frog, fish, and mouse. Rodenticide (brodifacoum 0.005%) was tested to the rat. Each feed and rodenticide are weighed before and after testing to analyze the preference of rats. The data analyzed using SAS program for windows version 9.0, a further test with Duncan multiple range test with α = 5% and 1%. Unhulled rice (grain) and cricket were the kind of feed that most preferred or highest palatable by test animals. The existence of feed causes the lower consumption of brodifacoum rodenticide by three species of rats.

The Effect of Mealworm as an Additional Bait to the Consumption of Malaysian Field Rat (Rattus tiomanicus) and Rice Field Rat (Rattus argentiventer)

Rats is one of the important pest to human life, both in the agriculture and plantation, include rice field rat in rice and malaysian field rat in oilpalm. Various tactics and strategies have been conducted to control population of rat, one of them used poisonous bait (rodenticide). The attractiveness of poisonous bait is very important because rats do not like taste of the active ingredients of rodenticide. The aims of this research was to investigate the influence of mealworm (larvae of Tenebrio molitor) to the consumption of bait and poisonous bait. Therefore, it can increase the effective control to malaysian and rice field rat. There are four trial step in this research with choice test method. First trial, malaysian rat consumed more broken rice, while rice rat consumed more unhulled rice. Secondly, malaysian rat consumed more mealworm and broken rice, otherwise rice rat consumed more unhulled rice. Thirdly, the consumption of malaysian rat to mealworm showed significantlty difference with brodifacoum, while rice rat showed no difference. Fourthly, the consumption of malaysian rat to mealworm showed no significantly difference with bromadiolone, while rice rat showed difference. To increase the consumption of malaysian and rice field rats on rodenticides containing brodifacoum and bromadiolone, mealworm can be added as a flavoring to the rodenticide. By adding mealworm to rodenticide with a mixture of poisonous bait specifically for rats and placed in a special place for rats, it will increase rat’s consumption to the point of killing them, while not inviting non-target animals to consume it and save to the environment.

The Existence of Leptospira interrogans on Rats and The Transmission Potency in Public Areas: School, Traditional Market, and Settlement in Yogyakarta

Leptospirosis is a zoonotic disease caused by bacterial infection, Leptospira interrogans. Indonesia is known for being an endemic country of this disease and Yogyakarta Special Province has become one of the regions with high cases of Leptospirosis. There was lack of information on the L. interrogans prevalence on rats at the public areas, such as school and traditional market. This research was conducted to determine and predict the potential Leptospirosis transmission in public areas, especially in schools, traditional markets,. and the settlement of Yogyakarta. Wild rats were collected from several public places (elementary schools, traditional markets, and Settlement areas) by using single live traps. The rat's blood was centrifuged to obtain the serum. The serum was tested by using immunochromatography of Leptotek Lateral Flow. The collected rats and shrews were euthanized and then identified for the species and the morphological features. Total of 27 rats (67.5%) and shrews 13 (32.5%) were collected. There were six species of collected rats, namely Rattus argentiventer, Rattus norvegicus, Rattus tanezumi, Rattus tiomanicus, and Bandicota bengalensis, while the collected shrew species was Suncus murinus. The rats and shrews from traditional market were negative with L. interrogans, however the positive results was in elementary schools (14.28%), that were from R. norvegicus and S. murinus, moreover the positive infection also showed in the settlements (57.14%), that were from R. argentiventer, R. norvegicus, and R. tiomanicus. These findings indicated that school and settlement must be a concern for the leptospirosis transmission.

A cross-sectional study of Angiostrongylus malaysiensis in rats and gastropod hosts from recreational parks in Kuala Lumpur, Malaysia: Detection, risk factors and pathology.

Angiostrongylus malaysiensis is a potential zoonotic parasite, which reported to co-occur with A. cantonensis in human cerebrospinal fluid. It is a heteroxenous nematode that primarily develops through the early larval stages in gastropods and attains sexual maturity within rats. This study was conducted to determine the host species responsible for the reservoir of A. malaysiensis and investigate the risk factor for transmission among the hosts in Kuala Lumpur, Malaysia. Sampling was conducted in six recreational parks. The rats were trapped alive using steel wire traps with bait, while the gastropods were collected by active searching. The rats were euthanized and dissected to collect any adult worms observed. The molecular detection of A. malaysiensis was performed by PCR on gastropod tissue samples. Biotic and landscape factors were recorded for risk factor analysis. In total, 82 rats and 330 gastropods were collected throughout the study. Overall, 3.64% of gastropods and 32.9% of rats were infected with A. malaysiensis. Rattus tiomanicus (Malayan wood rat) and Parmarion martensi (Yellow-shelled semi-slug) were found as important hosts for A. malaysiensis. Host species, sampling site and macrohabitat type are risk factors associated with the prevalence of A. malaysiensis infection in rats. For gastropods, host species and sampling site are risk factors that correlate with the parasite detection. In total, 128 adult A. malaysiensis were recovered from the infected rats. The mean intensity of infection with adult A. malaysiensis was 4.65 for Rattus rattus complex and 4.90 for R. tiomanicus. Adult worms were found in the pulmonary artery or right ventricle, while eggs and first-stage larvae were found in capillaries of the caudal lung lobe. Infected lungs showed extravasated red blood cells in the alveolar spaces. The pulmonary arteries in the infected lung lobe were thickened. Kepong Metropolitan Park is the hotspot area for A. malaysiensis in Kuala Lumpur. These results provide essential information for public health officials to develop targeted interventions to reduce the transmission of A. malaysiensis in urban areas, particularly in recreational parks.

Short Communication: Diversity of small mammals (non-volant) in tropical peatland ecosystem of Orang Kayo Hitam Forest Park, Jambi, Indonesia

Abstract. Dara W, Iswandaru D, Wulandari C, Novriyanti, Prasetia H. 2023. Short Communication: Diversity of small mammals (non-volant) in tropical peatland ecosystem of Orang Kayo Hitam Forest Park, Jambi, Indonesia. Intl J Bonorowo Wetlands 13: 30-35. Peatlands areas dominate Orang Kayo Hitam Forest Park (OKH Forest Park), Jambi, Indonesia. The largest forest fire in the OKH Forest Park area occurred in 2015, damaging more than 70% of the area. The event subsequently affected the existing biodiversity, especially the diversity of small mammals. Small mammals have an important role in the ecosystem as agents in regeneration and restoration, including in the OKH Forest Park. The method used is the cage trap method which is placed by systematic sampling. Traps were placed in two types of habitats, namely shrubs, and forests. The bait variation consisted of coconut, sweet potato, banana, and oil palm fruit. All baits were treated by burning to give off an aroma. The resulting data were analyzed quantitatively using the Shannon-Wiener Diversity Index. Types of small mammals found in shrubs and forest habitats are Malaysian field rats (Rattus tiomanicus (Miller, 1900)) and plantain squirrels (Callosciurus notatus (Boddaert, 1785)) The diversity index shows a low category with a value of (H' = 0.17884). That indicates the condition of the habitat in the post-burnt peat ecosystem is still relatively depressed.

Efficacy of cholecalciferol rodenticide to control wood rat, Rattus tiomanicus and its secondary poisoning impact towards barn owl, Tyto javanica javanica

Studies were conducted on the potential use of cholecalciferol as an alternative to anticoagulant rodenticides to control common rat pest in oil palm plantations, i.e., wood rats, Rattus tiomanicus, and the secondary poisoning impact of cholecalciferol on barn owls, Tyto javanica javanica. The laboratory efficacy of cholecalciferol (0.075% a.i.) was compared with commonly used first-generation anticoagulant rodenticides (FGARs): chlorophacinone (0.005% a.i) and warfarin (0.05% a.i). The 6-day wild wood rat laboratory feeding trial showed cholecalciferol baits had the highest mortality rate at 71.39%. Similarly, the FGAR chlorophacinone recorded a mortality rate of 74.20%, while warfarin baits recorded the lowest mortality rate at 46.07%. The days-to-death of rat samples was in range of 6–8 days. The highest daily consumption of bait by rat samples was recorded for warfarin at 5.85 ± 1.34 g per day while the lowest was recorded in rat samples fed cholecalciferol, i.e., 3.03 ± 0.17 g per day. Chlorophacinone-treated and control rat samples recorded consumption of about 5 g per day. A secondary poisoning assessment on barn owls in captivity fed with cholecalciferol-poisoned rats showed after 7 days of alternate feeding, the barn owls appeared to remain healthy. All the barn owls fed with cholecalciferol-poisoned rats survived the 7-day alternate feeding test and throughout the study, up to 6 months after exposure. All the barn owls did not show any abnormal behavior or physical change. The barn owls were observed to be as healthy as the barn owls from the control group throughout the study.

Molecular Surveillance for Vector-Borne Bacteria in Rodents and Tree Shrews of Peninsular Malaysia Oil Palm Plantations

Many human clinical cases attributed to vector-borne pathogens are underreported in Malaysia, especially in rural localities where healthcare infrastructures are lacking. Here, 217 small mammals, consisting of rodents and tree shrews, were trapped in oil palm plantations in the Peninsular Malaysia states of Johor and Perak. Species identification was performed using morphological and DNA barcoding analyses, and 203 small mammals were included in the detection of selected vector-borne bacteria. The DNA extracted from the spleens was examined for Orientia tsutsugamushi, Borrelia spp., Bartonella spp. and Rickettsia spp. using established PCR assays. The small mammals collected in this study included Rattus tanezumi R3 mitotype (n = 113), Rattus argentiventer (n = 24), Rattus tiomanicus (n = 22), Rattus exulans (n = 17), Rattus tanezumi sensu stricto (n = 1) and Tupaia glis (n = 40). Orientia tsutsugamushi, Borrelia spp. and Bartonella phoceensis were detected in the small mammals with the respective detection rates of 12.3%, 5.9% and 4.9%. Rickettsia spp., however, was not detected. This study encountered the presence of both Lyme disease and relapsing fever-related borreliae in small mammals collected from the oil palm plantation study sites. All three microorganisms (Orientia tsutsugamushi, Borrelia spp. and Bartonella phoceensis) were detected in the R. tanezumi R3 mitotype, suggesting that the species is a competent host for multiple microorganisms. Further investigations are warranted to elucidate the relationships between the ectoparasites, the small mammals and the respective pathogens.

OBSERVATION ON THE FRUIT DEVELOPMENT, FRUIT RIPENING AND PREFERENCE OF RATS IN DAMAGING PINEAPPLE MD2 BASED ON HORMONAL FLOWER INDUCED DAYS AND PHENOLOGY

A study was carried out to determine the preferences of rats in damaging pineapple MD2, based on hormonal induced days. Biologische Bundesantalt, Bundessortenamt and Chemische Industrie (BBCH) coding system, a phenology scale for all flowering plants, was used to describe the vegetative growth stage of MD2 pineapple in this study. The evaluation of MD2 phenology was carried out between 60 and 173 days after hormonal flower induction activity. Rat damage was studied at two growth stages, namely fruit development and fruit ripening of MD2 pineapple. The results showed that MD2 pineapple takes around 72 to 95 days to ripen from fruit development. The pineapple is best to be harvested around 140-145 days after hormonal flower induction activity or at BBCH scale 801-805. At this time, the pineapple turns from light green to yellowish green. Two species of rats, namely Rattus tiomanicus and Rattus argentiventer preferred matured fruits in between BBCH scales 800 to 805. Chemical control through rodenticide baiting campaign for rats needs to be done as early as 70-78 days after hormonal flower induction activity or before the BBCH scale 700 as best control measures. Keywords: Biologische Bundesantalt, Bundessortenamt and Chemische Industrie coding system, pineapple, rat damage.

DIVERSITY OF NON-VOLANT SMALL MAMMALS IN PULAU TINGGI, JOHOR, MALAYSIA

A non-volant small mammal survey was conducted at Pulau Tinggi between July and September 2019. This study aimed to provide baseline data for non-volant small mammals in Pulau Tinggi by setting 55 cage traps and 20 pitfalls for 44 trapping nights. A total of 20 individuals of non-volant small mammals were documented, representing five species from three families: Soricidae, Sciuridae and Muridae. The Rajah spiny rat (Maxomys rajah) and the Red spiny rat (Maxomys surifer) were the most abundant species (n=6) of non-volant small mammals in Pulau Tinggi. The Malayan field rat (Rattus tiomanicus) was the least species (n=1). The Malayan shrew (Crocidura malayana) is the only shrew recorded on the island. The analysis of similarities between our study site and other Malaysian islands reveals that Pulau Tinggi shares more similarities with Pulau Pangkor and Pulau Perhentian than Pulau Tioman. The small mammal richness on Pulau Tinggi is relatively low compared to other islands, most likely due to the study site’s limited coverage and time constraints. Long-term monitoring is required to determine the true diversity of species and distribution of small mammals on Pulau Tinggi.

Keanekaragaman Mamalia Kecil Pada Empat Tipe Tutupan Lahan Di Kesatuan Pengelolaan Hutan (KPH) Batutegi, Provinsi Lampung

The diversity of small mammals has a vital role as a bioindicator of a managed area in the forest. This research was conducted to determine the small mammals in four types of land cover in the agroforestry management area of ​​KPH Batutegi. Sampling was carried out using traps in the four types of land cover. Species diversity was analyzed by diversity index, evenness, dominance, and abundance. The results of this study indicate that the variety, evenness, and abundance of small mammals are low due to land cover conditions, elevation, and the behavior of small mammals in their habitat. The dominant small mammals are Rattus tiomanicus sabae and Maxomys baeodon because they have a high level of adaptation to various habitats. Twelve small mammals were found in the agroforestry cover, ten individuals in the forested cover, four individuals in the monoculture coffee cover, and two individuals in the private land. The management of the Batutegi KPH shall counsel the community to prevent land clearing, which causes damage to forest sustainability, to maintain the existence of small mammals.

Prevalence of Pathogenic Leptospira spp. in Non-Volant Small Mammals of Hutan Lipur Sekayu, Terengganu, Malaysia.

Leptospirosis is an important zoonotic disease that is transmitted worldwide through infected small mammals such as rodents. In Malaysia, there is a paucity of information on the animal reservoirs that are responsible for leptospirosis transmission, with only a few studies focusing on leptospirosis risk in recreational areas. Therefore, in this study we characterized the species composition and the prevalence of pathogenic Leptospira spp. in non-volant small mammals of Hutan Lipur Sekayu, Terengganu. We performed ten trapping sessions totaling 3000 trappings between September 2019 and October 2020. Kidney samples from captured individuals were extracted for the PCR detection of pathogenic Leptospira spp. Overall, we captured 45 individuals from 8 species (1.56% successful trapping effort), with 9 individuals testing positive for pathogenic Leptospira, that is, a 20% (n = 9/45) prevalence rate. Rattus tiomanicus (n = 22) was the most dominant captured species and had the highest positive individual with pathogenic Leptospira (44.4%, n = 4/9). Despite the low successful trapping effort in this study, the results show the high diversity of non-volant small mammals in Hutan Lipur Sekayu, and that they could also maintain and transmit pathogenic Leptospira.

Molecular Identification and Genetic Variation of Rattus Species From Oil Palm Plantations of Malaysia Based on Mitochondrial Cytochrome Oxidase Subunit I (COI) Gene Sequences.

Rats (Rattus species) are the most notorious vertebrate pests in Malaysian oil palm plantations. Although many studies have been conducted on Asian rats, little attention has been paid to their species composition and phylogenetic relationships in oil palm plantations in Peninsular Malaysia. We determined the mitochondrial cytochrome oxidase subunit I (COI) gene sequence (708 bp) for 216 individual rats collected from five oil palm plantations in Peninsular Malaysia. Phylogenetic analysis in conjunction with comparison with sequences from the nucleotide sequence database revealed five distinct lineages in the Malaysian oil plantations: Rattus tiomanicus, Rattus argentiventer, Rattus exulans, Rattus tanezumi, and a taxon corresponding to the Malayan house rat, which was most frequently observed (∼50%). The last taxon has traditionally been classified as a synonym of Rattus rattus (Rattus rattus diardii) or Rattus tanezumi, but our phylogenetic analysis placed it as an independent lineage, which is not particularly closely related to R. rattus or R. tanezumi, and which we refer to as Rattus diardii. The construction of the network showed that there is considerable genetic variation within the lineages of R. diardii and R tiomanicus, suggesting that these two species are native to the Malay Peninsula.

COMPARISON OF WARFARIN AND BROMADIOLONE BAITS FOR RAT CONTROL IN OIL PALM PLANTATIONS - EXPERIENCES IN THE 1990S

In rat population studies conducted in an oil palm plantation near Kulai, the 19-, 20- and 21-year-old plantings with low percentage fresh damage of 2-3 per cent had low to high rat population of Rattus rattus diardii (R. r. diardii) ranging from 83-542 rats per hectare. Although, the percentage of fresh damage of rat detected in the tall and older planting palms were low, the rat population on the ground was still high on per hectare basis. When single plot of warfarin and bromadiolone baits were tested to control R. r. diardii in the oil palm plantation near Kulai, three treatments were found to be effective. The treatments were ten rounds of bromadiolone bait (0.005%, 14.5 g) at one bait per palm and 50 per cent application density, five rounds of bromadiolone bait (0.005%, 14.5 g) at five baits per palm and 50 per cent application density, and nine rounds of bromadiolone bait (0.005%, 21 g) at one bait per palm and 50 per cent application density. In labour short situation, five rounds of bromadiolone bait (0.005%, 14.5 g) at five baits per palm and 50 per cent application density may be recommended, bearing in mind a higher material cost will be incurred in such application of multiple baits per palm. In another single plot of warfarin and bromadiolone baits were tested to control Rattus tiomanicus (R. tiomanicus) in an oil palm plantation near Bekok and all the four bromadiolone bait treatments gave good control and recorded no fresh damage in post-baiting assessments. In terms of total bait applied per hectare basis, the best treatment was bromadiolone bait (0.005%, 14.5 g, one bait per palm) at 5.95 kg requiring eight baiting rounds followed by bromadiolone bait (0.005%, 21g, one bait per palm) at 7.71 kg requiring eight baiting rounds per campaign. Baiting with bromadiolone bait (0.005%, 14.5 g, one bait per palm) and 50 per cent application density is recommended for the control of R. r. diardii and R. tiomanicus, especially if the rat population is in high number in oil palm plantations. In plantations facing labour shortage, baiting with bromadiolone bait (0.005%, 14.5 g, five baits per palm) at 50 per cent application density is recommended as the stopgap measure. Once control is achieved, it is recommended to reverse back to standard baiting of one bait per palm in normal routine six-monthly programmes. Keywords: Rats, oil palm plantations, baiting, warfarin, bromadiolone.

Invasive rat drives complete collapse of native small mammal communities in insular forest fragments

As tropical forests are becoming increasingly fragmented, understanding the magnitude and time frame of biodiversity declines is vital for 21st century sustainability goals. Over three decades, we monitored post-isolation changes in small mammal species richness and abundance within a forest landscape fragmented by the construction of a dam in Thailand.1,2 We observed the near-complete collapse of species richness within 33 years, with no evidence of a recolonization effect across repeatedly sampled islands. Our results further revealed a decline in species richness as island size decreased and isolation time increased, accelerated by the increasing dominance of the ubiquitous Malayan field rat, Rattus tiomanicus. This species was already hyper-abundant on smaller islands in the initial surveys (1992-1994, 66% of individuals) but became monodominant on all islands, regardless of island size, by the most recent survey (2020, 97%). Our results suggest that insular forest fragments are highly susceptible to rapid species loss, particularly due to the competitive nature of Rattus accelerating the rate at which extinction debts are paid. To mitigate these impacts, reducing the extent of habitat degradation, as triggered by fragmentation and exacerbated by isolation time, can help to sustain native biodiversity while averting Rattus hyper-abundance.