has occurred in parts of Europe and the United States in locations
where anticoagulants were used intensively for a decade or so.

The purpose of this study was to: (1) gather baseline information
required to develop an efficient monitoring system for the control of
anticoagulant resistant rats in the Philippines including (a) develop-
ment of methods suitable for screening anticoagulant resistant rats
in two local pest species--R. r. mindanensis and R. argentiventer, and
(b) testing of compounds known to counteract deveTopment of anticoagu-
lant resistance in rat populations; (2) propose a system, based on the
above information, that could be used to regulate anticoagulant
resistance within acceptable ranges.

No-choice feeding tests, using 0.025-percent warfarin bait, were per-
formed on R. r. mindanensis (14 days) and R. argentiventer (10 days)
as a method for screening warfarin-resistant individuals. Animals
that survived for 10 days after withdrawal of the treated bait were
considered resistant.

The mean pretreatment plasma clotting time of R. r. mindanensis was
12.3 s. Animals treated (gavage) with 5 mg warfarin or 2.5 mg
diphacinone per kilogram of body weight had mean clotting times of
80.3 and 58.2 s, respectively, 48 h after treatment. These results
can be used to quantify anticoagulant-resistant or susceptible animals
of this species, granting that resistant rats will have lower clotting
times than the nonresistant animals used to establish the baseline
data.

Feeding tests with 0.1-percent calciferol, 0.1-percent calciferol plus
0.025-percent warfarin, 0.025-percent warfarin, 0.005-percent broma-
diolone, and 0.002-percent biodifacoum resulted in similar mean num-
bers of days to death--6.7, 4, 5.9, 6.5, and 5.6, respectively, for R.
r. mindanensis. All treatments resulted in 100 percent mortality.

The information gathered in this study may serve as a guideline in
establishing a national anticoagulant monitoring program. This pro-
gram would detect resistant rat populations and offer alternate
rodenticide recommendations to control crop damage by anticoagulant-
resistant rats (Hoque, Ph. D. thesis, in progress).

Sugarcane yield losses due to rodents with reference to species
distribution, in-field stalk damage, varietal preference, and movement
under Philippine conditions

Sugarcane fields, in 14 locations within 14 mill districts on Negros
Island, were surveyed for rat damage and yield losses. Five sampling
areas (4 m X 10 m) in fields of not less than 1 ha were selected