Rattus Argentiventer Research Articles

Field trials of warfarin and brodifacoum wax block baits for the control of the rice field rat,Rattus argentiventerin peninsular Malaysia∗

Abstract Replicated trials, in which 0.05% warfarin and 0.005% brodifacoum were used to control rice field rats, are described. In the first trial, 15 g wax blocks containing the poisons were applied, in 20–24 ha rice field plots, once a week for four weeks or twice a week for four weeks or once a week for 8 weeks. In the second trial, 5 g wax blocks were applied once a week for four weeks. In both trials baiting commenced at the time of transplanting, and the effectiveness of treatments was measured by mortality estimates, derived from pre‐ and post‐treatment census baiting in treated and reference plots and by damage reduction in post‐treatment damage assessments. Both poisons were equally effective when applied as 15 g blocks giving, on average, between 81% and 82% control, but gave significantly better control (87%) when applied twice a week rather than once (79%). However, when 5 g blocks were used, the more toxic poison, brodifacoum, gave 80% control compared with only 56% with warfarin. Tiller cutt...

Laboratory evaluation of the anticoagulants coumatetralyl and brodifacoum againstRattus argentiventerin Peninsular Malaysia1

Abstract In laboratory toxicity tests using individually‐caged rice field rats, Rattus argentiventer (Robinson & Klossl, complete mortality occurred when the rats were fed on broken rice/corn oil bait containing 0.0375% coumatetralyl for four days. Equivalent kills were obtained when rats we're fed 0.002% and 0.005% brodifacoum for one day. Both compounds were more toxic than warfarin at 0.025%. Choice tests showed that 0.001% and 0.0005% brodifacoum were as acceptable as 0.025% warfarin, but higher concentrations and 0.005% and 0.0375% coumatetralyl were poorly accepted. The potential advantages of coumatetralyl and brodifacoum over other rodenticides for the control of R. argentiventer in rice fields in Malaysia are discussed.

Rice‐field rats of Lower sind: abundance, reproduction and diet

Data on the abundance, reproduction and diet of rice field rats were collected during three rice seasons. At rice harvest, Bandicota bengalensis nearly doubled its litter size and tripled its pregancy rate and greatly increased in abundance. Millardia meltada remained abundant and maintained a relatively high pregnacy rate over all stages of crop development. These differences corresponded to differences in diet. Before the onset of grain ripening, the diet of Millardia contained more high‐energy food (weed seeds, insects and scattered grain) while the diet of Millardia contained more high‐energy food (weed seeds, insects and scattered grain) while the diet of Bandicota contained primarily low‐energy food (rice stems and unidentified plant fibres); although both species ate principally rice at harvest. During most months, Nesokia indica was seldom caught above ground and ate mostly unidentified plant fibres. However, when grain ripened, Nesokia was caught on the surface and stomachs contained principally rice grain. Nesokia showed a lower pregnancy rate and smaller litter size, but apparently greater adult survival. They bred more often in the cooler months, during and after harvest.Some information on other topics is also presented, such as: sexual activity in males; substrate preference; relative adult longevity; the effect of excessive flooding of rice paddies; and the importance of underground rice caches, rice field weeds and swamp land to overwintering Bandicota. Estimates of the relative damage to the crop caused by each species at different stages of crop development were made by using data on rodent diet and abundanc

Laboratory Evaluation of 0.025% Warfarin AgainstRattus argentiventer

Abstract Laboratory feeding tests were conducted to determine the efficacy of 0.025% warfarin against two separate populations of Rattus argentiventer (Robinson and Kloss) in Peninsular Malaysia. No-choice feeding periods of 2, 4, 6, 8, 10 and 12 days gave mortalities of 27.5, 57.5, 82.5, 87.5, 97.5 and 100% respectively for the pooled data. No significant heterogeneity was found between the sexes of the populations but there was marked individual variation in susceptibility to warfarin. A base-line for the susceptibility of R. argentiventer to warfarin was established; the upper 95% confidence limit calculated for the LFP (Lethal Feeding Period) 98 indicated that survival following an 18-day feeding period on 0.025% warfarin bait is a suitable test for the detection of warfarin resistance. It is concluded that warfarin is appropriate for use against R. argentiventer infesting rice fields and that poisoned bait would be best applied when alternative foods are most limited.

Schistosoma incognitum from Cikurai, West Java, Indonesia

Schistosoma incognitum is reported for the first time from West Java, Indonesia where 84% of ricefield rats, Rattus argentiventer, were infected. Radix auricularia rubiginosa snails were intermediate hosts. The adult stage of the Javanese strain of S. incognitum and lesions in naturally-infected rodents are described. Rattus exulans, Rattus norvegicus and Mus musculus were experimentally infected. Epizootiology is similar to that described in other countries.

Food-Base Flavor Additive Improves Bait Acceptance by Ricefield Rats

Philippine ricefield rats (Rattus rattus mindanensis) that were accustomed to eating rice grain showed greatly increased preference for granulated rice when it was enriched by the volatiles from ground unpolished rice. This was the best of 11 formulations involving 8 rice components that were tested with an automated brief-exposure preference tester. This formulation was also highly preferred (P 2X ) of the treated bait and showed 88 percent mortality. These results indicate that intensifying the flavor cues associated with a familiar or preferred food is a fruitful approach in the development of an effective bait enhancer. J. WILDL. MANAGE. 41(2):290-297 The familiar problem of bait acceptance in rat control programs readily applies to the Philippine ricefield rat. In their 1971 Annual Report (p. 61) scientists of the Philippine Rodent Research Center (College Laguna, Philippines) stated: suspect that bait acceptance is a major factor limiting the effectiveness of acute toxicants as now used for rodent population reduction in Philippine ricefields; methods to improve acceptance need further investigation. Because of this need, we began a program to develop highly palatable baits for rat control in ricefields. The food preference behavior of wild rats is very complex. The drive to satisfy energy requirements affects preference (Schein and Orgain 1953, Cornwell and Bull 1967, Brooks and Bowerman 1973). Novelty also can be important (Welker and King 1962, Bronson 1966, Long and T pp 1967, Valle 1970). A novel stimulus may direct an animal's exploratory behavior and lead it to the bait, but consumption of the bait may or may not follow, depending n how much wariness the same novel cue elicits. As the bait's novelty decreases, so d es its ability to direct exploratory behavior (Long and Tapp 1967). Furthermore, novel factors such as taste, odor, color, and texture may provide cues for bait aversion (shyness). However, response to a familiar food is more predictable. Previous experience is an important factor (Barnett and Spencer 1953, Jackson 1965, Cornwell and Bull 1967, Reif 1969, Bull 1972, Howard and Marsh 1974). In tests and observations of feeding behavior, we have found that rats consistently prefer familiar foods over unfamiliar ones. The durability and strength of this response seem to increase when the familiar food has been a major diet item and is satisfying the animal's nutritional needs. Tigner (1972) found that when there is enough rice grain in the paddies to sustain ricefield rats, it makes up 60-85 percent of the 1 Investigations were supported by funds provided to the U.S. Fish and Wildlife Service by the Agency for International Development under the project Control of Vertebrate Pests: Rats, Bats and Noxious Birds PASA RA(ID) 1-67. 290 J. Wildl. Manage. 41(2):1977 This content downloaded from 207.46.13.148 on Sun, 11 Sep 2016 04:33:41 UTC All use subject to http://about.jstor.org/terms FLAVOR ENHANCEMENT OF RAT BAITS * Bullard and Shumake 291 volume of food in their stomachs. Thus, the most familiar food of the rats that damage rice plants is the rice grain itself. Could a rice fraction that intensified the familiar flavor cues of rice provide the key to developing a highly palatable bait? The series of studies described below was designed to answer this question. The authors gratefully acknowledge G. Holguin, S. E. Gaddis, and K. A. Crane for their technical assistance throughout the project. We also thank C. P. Breidenstein for statistical assistance and A. H. Bean for critical review of the manuscript.

Coulometric Recorder for Timing and Counting Events in the Field

An event recorder for timing and counting was developed specifically for field application. The new recorder uses inexpensive coulometers for data storage and requires only microwatts of power from long-lasting batteries. Stored data are retrieved from the recording cells with a simple laboratory readout instrument. Six of these recorders were used to record the number of visits and accumulated feeding time in a food preference experiment with ricefield rats (Rattus rattus mindanensis). The results indicated that such visit count and feeding time records can be used to estimate accurately food preference based on consumption and, with suitable regression equations, predict weight of food consumed. When accuracy was checked by simultaneous recordings at one of the feeders, readings from the coulometric recorders never deviated more than about + 6 percent from those obtained with conventional electromechanical counters and timers. These results show that valid measurements of activity can be made with the event recorders when used as rat feeding monitors. Other applications are suggested. J. WILDL. MANAGE. 40(2):278-282 Biological studies often require the counting and timing of events, and it is convenient if this can be done with automatic recording equipment. Unfortunately for the field biologist, most electromechanical counters and timers are expensive and complex devices that are designed for use in the laboratory. We developed a simple event recorder by using coulometers as data storage cells. These recorders offer several advantages to the field biologist: they are silent, battery-operated, long-lived, operationally simple, and relatively inexpensive (less than $20 in electrical parts). A special readout instrument recovers stored data and clears the cells for reuse. Our event recorders performed well when tested as feeding activity monitors in food preference tests with ricefield rats. The data recorded (number of feeding visits and accumulated feeding time) proved sufficiently accurate and sensitive to allow prediction of the food consumed. DESCRIPTION OF THE EVENT RECORDER The recorder system consists of two parts: a data recorder and a data readout instrument. The uniqueness of the recording syst m lies in its coulometric method of storing data for later retrieval.

Karyotypes of Ten Rats (Rodentia: Muridae) from Southeast Asia

Karyotypes of nine species of Rattus from the mainland of South Vietnam and one from Thailand are presented. Members of the subgenus Rattus, including Rattus argentiventer, Rattus exiguus, Rattus exulans concolor, Rattus nitidus, Rattus norvegicus, Rattus rattus molliculus and Rattus sladeni, had diploid numbers of 42 and very similar karyotypes. Rattus surifer finis and Rattus moi, both in the subgenus Lenothrix, had identical diploid numbers, 52, but dissimilar karyotypes. The karyotype of Rattus sabanus revertens from South Vietnam was similar to that of Rattus sabanus reported from Malaysia.

Laboratory Studies of the Effect of U-5897 on the Reproduction of Wild Male Rats

The effects of U-5897 (3-chloro-l,2-propanediol), a male chemosterilant that acts by inducing epididymal lesions, were tested in the laboratory on ricefield rats (Rattus argentiventer), Polynesian rats (R. exulans), black rats (R. rattus), Norway rats (R. norvegicus), and laboratory rats (Long-Evans strain). For each species, seven treatment groups of five males each were given single oral doses ranging from 0-300 mg/kg. No lesions were induced in ricefield and Polynesian rats at any dose level. Some Norway and laboratory rats developed lesions at doses of 50 mg/kg, and all developed them at 100 mg/kg and above. Black rats developed lesions at 100 mg/kg, and higher, but the response was incomplete; at least one male at each dose level failed to develop lesions. Some Norway, laboratory, and Polynesian rats died from doses of 200 mg/kg and higher. The concept of controlling wildlife populations by interfering with one or more of the reproductive processes was discussed by Davis (1961), and attempts to apply the concept have been reported by several workers (Balser 1964, Linhart and Enders 1964, Linhart et al. 1968, Howard and Marsh 1969). Because reproductive inhibitors have advantages over traditional control chemicals in both safety and specificity, there is considerable interest in finding effective ones for use against species causing damage. One possible compound for rats is U-5897, a chlorohydrin. It was first shown to have a reversible antifertility effect in male monkeys, (Macaca mulatta), guinea pigs (Cavia cobaya), and white rats (Kirton et al. 1970, Ericsson and Youngdale 1970). Subsequent studies revealed that male white rats are permanently sterilized when given single oral doses of 45 mg/kg, approximately five times the minimum dose that produces reversible antifertility (Ericsson 1970). In both instances, the compound is a post-testicular artifertility agent that apparently does not affect libido (Ericsson 1970, Ericsson and Baker 1970). Sterility 1 Simonsen Laboratories, Gilroy, California. 508 induced in white rats is due to the formation of a lesion in the caput epididymidis that completely blocks passage of sperm to the exterior. Recently Ericsson and Connor (1969) reported that Norway rats also develop the epididymal lesion when treated by gavage or via drinking water. The unique properties of this compound suggested it might be a useful male sterilant for rat species causing agricultural damage. Accordingly, we tested its effects on Polynesian, black, ricefield, and Norway rats, and on laboratory rats for comparison.

Athesmia (Trematoda: Dicrocoeliidae) Odhner, 1911 Liver Fluke of Monkeys from Colombia, South America, and Other Mammalian Hosts

In addition to earlier reports of Athesmia foxi Goldberger & Crane, 1911, the writer has studied well-fixed, stained and mounted specimens of this dicrocoeliine trematode from five different species of monkeys from eastern Colombia, viz., Saimiri sciurea (Linn., 1758), Cebus capucinus (Linn., 1758), C. albifrons (Humboldt, 1912), C. apella (Linn., 1758) and Oedipomidas oedipus (Linn., 1758). The worms vary in length and breadth, not only in different host species but also in different speci- mens from the same host. Study of internal anatomy likewise indicates that consider- able variation exists in essential organs, including male and female genitalia. The writer agrees with Travassos (1944) that a liver fluke from a Cuban bat, Artibeus jamaicensis parvipes, designated A. parkeri (Perez Vigueras, 1942) should be trans- ferred to Travassos' 1942 genus Pseudathesmia, and may possibly be the same as his type species P. paradoxa. Comparison of the Colombian specimens of A. foxi with those from the liver of Malaysian feral rats, Rattus argentiventer Robinson & Kloss, confirms the view of Lee (1965) that the species is present in a new mammalian host in a geographically different area. A. foxi has also been recovered from a crab-eating raccoon, Procyon cancrivorus Cuvier, and a monkey, Chiropotes albinasa Geoffroy & Deville from separate states of Brazil (Teixeira de Freitas, 1962). Comparative life cycle investigations are required before A. heterolecithodes (Braun, 1899) Looss, 1899, with wide geographical and host distribution in birds, is proved to be identical with A. foxi of mammalian hosts, in which case the name A. heterolecithodes would take precedence over A. foxi.

Miniature radio-tracking studies of the hosts of vector mites in Malaysia.

Successful radio-tracking of hosts of vector mites has been accomplished in :Malaysia. The home ranges, centers of activity, times of movement and distances moved have been measured for Rattus rattus argentiventer and R. r. jalorensis . Study areas and methods of obtaining data are described, and the advantages of this method are briefly discussed. A bibliography of all radio-tracking literature known to the author is included.

Digenetic Trematodes of Feral Rats from Malaysia with Descriptions of Beaveria beaveri and B. microacetabulum gen. n., spp. n., of a New Subfamily Beaveriinae (Troglotrematidae)

From 295 individuals of four species of feral rats in Malaya and North Borneo, five species of trematodes were collected: Echinostoma malayanum Leiper, 1911, from Rattus argentiventer Robin- son and Kloss; Skrjabinus muris Stscherbakova, 1942, from R. sabanus Thomas and R. rajah surifer Miller (new hosts and distribution records); Athesmia foxi Goldberger and Crane, 1911, from R. argentiventer (new host and distribution records); Beaveria beaveri gen. n., sp. n. from R. sabanus; and B. microace- tabulum sp. n. from R. infraluteus Thomas. A new subfamily, Beaveriinae, is proposed for the new genus which appears to be most suitably placed in the family Troglotrematidae.

Range of Movement of Some Malayan Rats

Although accounts of experiments involving the trapping and retrapping of marked rodents are now numerous, no such studies seem to have been made of the many species of rats in Southeast Asia. Experiments of this sort have recently been carried out in Malaya on rats which are the hosts of the chiggers which transmit mite-typhus (scrub-typhus). Unlike most such studies, interest was centered rather on differences between species than on differences between individuals of the same species, and a method was sought of expressing an “average” home range for such species. In attempting to do this it became clear that the customary methods of estimating home range, such as those summarized by Stickel (1954), were not in fact applicable to the problem, since the “ home range,” as usually understood, could not be exactly delimited. The concept of the home range has, therefore, been replaced, for this purpose, by the concept of a series of probability contours surrounding a center of activity, and what appears to be a new way of calculating and expressing the result has been evolved. The major hosts of the trombiculid mites which convey mite-typhus are, in Malaysia, rats of the genus Rattus . Some account of the various mammals involved has previously been given in these pages (Harrison and Traub, 1950) and elsewhere (Audy and Harrison, 1954), while a detailed study of their habitat preferences has been published recently (Harrison, 1957). The species involved in the present account are: Rattus jalorensis (Bonhote), Malaysian wood rat. A member of the white-bellied Rattus rattus group, confined to cleared land and secondary forest, with a decided preference for the edges of woodland. Rattus argentiventer (Robinson & Kloss), ricefield rat. Also a member of the Rattus rattus group, confined to grassland and ricefields. Rattus exulans (Peale) = R. …

Effect of rain on the feeding of the Malaysian rice-field rat.

Rattus rattus argentiventer, the Malaysian rice-field rat, is a common pest of standing crops and of wasteland covered by the tall grass ‘lalang’ (Imperata cylindrica). It is widely distributed throughout the Malaysian Islands, and in Malaya it is the most important host of the scrub typhus mite-vector Trombicula akamushi s.l.