FIELD RATS AND MOUSE IN MALAYSIA (PART 1)

RAT or TIKUS (in Malay) was a medium-sized and long-tailed rodents. Rat species are found throughout the order Rodentia. Stereotypical rats are found in the genus Rattus in which it includes some of the better-known species of rat such as the brown rat (Rattus norvegicus) and the black rat (Rattus rattus). As I know the Rice-field rat or known as the Malayan wood rat, the T greater bandicoot, greater bandicoot, the lesser bandicoot and the rice-field mouse are serious pests of ricefields, oil palm plantations and other field crops in Malaysia. These same five species are distributed throughout Southeast Asia. The ricefield rat and the Malaysian wood rat used to be treated as subspecies of Rattus rattus and were known as Rattus rattus argentiventer and Rattus rattus jalorensis. They are now recognized as separate species (Rattus argentiventer) and Rattus tiomanensis respectively. The bandicoots are large ground rats that build extensive burrows. In Malaysia two species occur they are the greater bandicoot (Bandicota indica) and the lesser bandicoot (B. bengalensis). The fifth species is the field mouse (Mus caroli) similar to the house mouse (Mus musculus) in size. In the question of what rat does in rice field usually the rats cut or pull up transplanted plants. They also chop down the young seedlings. At booting stage, they feed on rice panicles. On the other hand, during ripening stage, they feed on developing rice grains. Rats are found in lowland irrigated rice crops. Both the wet and dry seasons are favorable for rat reproduction and crop damage. In rainfed rice crops rodents have their greatest impact in the wet season. The availability of food, water, and shelter are the factors, which provide optimum breeding conditions. The presence of grassy weeds also triggers their development. Rice field rats feed at night with high activity at dusk and dawn. At daytime, they are found among vegetation, weeds, or maturing fields. During fallow period, they utilize major channels and village gardens as prime habitats. At tillering, 75% of time they are in burrows along the banks and after maximum tillering, 65% of time they are in rice paddies. Rat damage in the rice crop can be observed by the following symptoms such as missing germinating seeds, missing hills chopped young seedlings, missing plants, irregular cuttings of stem, chewed developing buds or ripening grains, tillers cut near base at 45° angle, retillering of stems, delayed grain maturity, missing grains and missing panicles. The feeding damage on the stem caused by the rice field rats may resemble insect damage although rat damage is usually distinguished by the clean cut at 45° of the tiller. The damage on the grains is similar to bird damage. Check muddy areas for runways, active burrows, and footprints of rice field rats. These are usually near the damage they have created. Check for presence of rice field rats: cut tillers and active holes on the bunds that surround the fields. When possible, catch rats to identify the species. Place traps along runways, or dug the rats from their burrows. This technical article in "Anim Agriculture Technology" I wrote about field rats and their species that found in Malaysia as a source of agronomic practices for all.

(1) THE RICEFIELD RAT (Rattus argentiventer) 

A medium sized rat with head and body (HB) 140-220 mm, hindfoot (HF) 35-38 mm, tail (T) 130-220 mm and uniformly dark. Its fur is coarse but not rough. Upperparts (dorsum) olive brown with black hairs intermixed among the brown; underparts (belly) silvery grey with or without a darker streak in the middle. One of the best characters is found in the pads on the soles of the hind feet (HF). Those of R. argentiventer are generally smaller and only slightly raised above the surrounding surface and the lamellae on the plantar pads are weakly developed in constrast to those of R. tiomanicus. These differences are presumably associated with the original habitats: grassland for R. argentiventer and scrub and plantation forest for R. tiomanicus. R. argentiventer has larger HF and 12 mammary tits. Distribution and status: The ricefield rat is widespread throughout Malaysia and present in all Southeast Asian countries except Singapore where it has yet to be discovered. Ecology and habitat: R. argentiventer is confined to grassland and rice fields. Before the 1960s, lalang (Imperata cylindrica) fields large and small, and rice fields were common sights throughout Peninsular Malaysia. The country was then self-sufficient in food-production for a population of about seven million people In the early 1950s, the Scrub Typhus Team at the Institute of Medical Research (IMR) Kuala Lumpur, were trapping commensal rodents (field rats) in lalang, scrub, oil palm plantations and secondary forest habitats in Selangor and the nearby states of Negri Sembilan and Malacca for the recovery of the vector mites (Leptotrombidum spp.), the causative agents of the scrub typhus disease. Our trapping results revealed that Rattus argentiventer was the predominant rat species in both lalang and rice field habitats. By 1965, the lalang habitat was reduced to scattered small plots due to development of highways and introduction of agricultural cash crops such as tapioca, sugar cane and banana that resulted in the mass migration of the rats to rice fields, rice itself being a grass. Nocturnal, terrestrial and omnivorous, with a natural diet of insects (termites and grasshoppers) in the lalang habitat, it caused tremendous damage by feeding on young rice plants in rice fields. In oil palm estates it feeds on insects, snails and slugs and young oil palm. It nests by digging burrows in well-drained soil or in the bunds between flooded puddles in rice fields.

(2) THE MALAYSIA WOOD RAT (Rattus tiomanicus)
This species is slightly smaller than the ricefield rat. The head and body length is 80-160 mm, Tail 85-170 mm and uniformly dark, HF 27-34 mm and uniformly dark. Upperparts olive brown; hairs smooth intermixed with spines which are not prominent. In the underparts it is usually pure white with occasional specimens dull white or yellowish white. It is distinguished from the ricefield rat by coloration of the silvery grey belly, shorter hindfoot length and 10 mammary tits Distribution and status: Widespread throughout Malaysia. It is also found in Thailand, Indonesia, Philippines and Singapore. Ecology and habitat: Nocturnal and semiarboreal. On the mainland in Malaysia, this rat is found more in oil palm plantations. It is also found in scattered communities in other habitats ranging from grassland, gardens, orchards to scrub and disturbed secondary forest, but not in primary forest. On some islands (e.g. Pulau Tioman) it ranges from lowland to hill forests. It climbs well and being semi-arboreal spends much of time in trees during the day and on the ground at night. In oil palm plantations it shelters in piles of cut palm fronds and in the crowns of palms. In scrub and woodland forest, its nest is built in holes in tree stumps, fallen logs and in thick bushes. It is omnivorous and its diet generally includes insects, land molluscs, roots, and fruits. It has become a very serious pest in oil palm estates. This article devided in three segments namely Part 1, Part 2 and Part 3 respectively. Thanks...

By,

M Anem,

Senior Agronomist,

Putrajaya,

Malaysia.

(January 2024).