Management of limiting factors in anticoagulant baiting of lowland
ricefield rats

The effectiveness of an agricultural rodent control program (e.g.,
sustained baiting with anticoagulants) may be influenced by a number
of variables. The identification of these limiting factors and appro-
priate modifications relative to the species, crop, or other condi-
tions would contribute to increased effectiveness in reducing damage,
greater economic return, and increased acceptance of the technology by
farmers. The purpose of this study was to determine: (1) the rela-
tive acceptance by ricefield rats of several common bait carriers; (2)
the effects of shape, size, and structural material used for bait sta-
tions; (3) the effect of location or placement of bait stations; and
(4) the ability of ricefield rats to discriminate between fresh and
moldy baits. Data were collected in a study area established within a
40-ha ricefield along the western rim of Laguna de Bay at barrio
Lungus, 2 km NE of Kalaya-an, Laguna, Philippines.

Populations of R. r. mindanensis in ricefields showed marked
responses to a variety of factors pertinent to the effective use of
sustained anticoagulant baiting. In bait acceptance trials, for
example, significantly greater amounts of rice shorts were taken when
compared to corn grits (p <0.005), cornmeal (p <0.001), rice bran (P
<0.001) and polished rice (p<0.005). Apparently, the shape, size,
and material used to construct bait stations caused discrimination
among animals. Ricefield rats preferred standard bamboo tube bait
stations to the nipa baiting hut (p<0.01), coconut husk (p <0.001),
plastic quart oil can (p <0.001), narrow-gauge bamboo (p <0.001) and
plastic "floating saucer" bait platforms (p <0.005).

Intake from bamboo tube bait stations located in three different sites
during the vegetative and booting stages of rice varied significantly.
During the vegetative stage, bait stations located either atop or
alongside paddy dikes were preferred (p <0.001) to in-paddy stations.
No statistical difference in intake was demonstrated between bait
stations located along paddy dikes and within paddies during booting
stage, but both sites had greater consumption than those atop the
dike.

Ricefield rats consumed significantly greater (p<0.001) amounts of
fresh bait (1,365 g) than moldy bait (41 g) over a 13-day field trial
using 12 paired bamboo bait stations. (Castro, M.S. thesis.)

Assessment of rat damage to corn

Actual crop losses caused by vertebrate pests, both in terms of yield
reduction and economic significance, are not readily defined without a