ten colors are available. The colors are numbered from 0 to 9 with
the color-number relationship based on the standard color code of the
electronics industry. When a purchase is made, a code is generated
and assigned exclusively to that buyer. The number of codes available
with different combinations and orders of colored layers is in the
millions. Two features that make recovery and/or detection of micro-
taggants easy are the incorporation of one or more fluorescent layers
and a ferromagnetic layer. Visual detection or magnetic recovery can
be made from a variety of materials. The manufacturer states that the
particles are chemically stable; the base material is an inert thermo-
set plastic that is unaffected by most solvents, acids, and bases.
The particles are also claimed to be thermally stable to 2000 C during
extended exposure and 3500 C for 30 seconds.

Bait-marking experiments: A number of tests were conducted to deter-
mine if microtaggants could be used to identify toxicants in baits,
rodenticides, or similar products in the digestive tracts of species
ingesting these materials. A 0.3-percent concentration of micro-
taggants was used in all bait tests.

Twelve Norway rats were used to test the acceptance of bait containing
microtaggants. The rats ate significantly (p = 0.03) more rolled oat
bait with microtaggants than without. In a toxic bait test, two
groups of white rats (n = 30/group) showed no significant difference
(p = 0.33) in mortality after being offered a 2-percent zinc phosphide
bait with microtaggants (22 of 30 died) or without them (26 of 30
died). To determine if microtaggants remained intact in the digestive
tract and fecal matter, the following species were tested on the
specified toxic bait: (a) six Norway rats and six white-footed deer
mice, 2-percent zinc phosphide on rolled oats; (b) five Richardson's
ground squirrels, 0.075-percent 1080 on oat groats; (c) two coyotes,
0.5 or 1 mg/kg 1080 on meat; (d) six red-winged blackbirds, 3-percent
Avitrol on cracked corn; (e) six starlings, 1-percent Starlicide
pellets. All species died within the expected time range for each
toxicant and all species, except three of the starlings, were well
marked in the digestive tract with intact particles that showed no
signs of degradation. Microtaggant detection was made under ultra-
violet light by dissection and gross observation of the digestive
tract, or by recovering microtaggants with a magnetic stirring rod
from a water suspension of fecal matter.

We also examined the potential of using microtaggants for determina-
tion of secondary hazards. Five Richardson's ground squirrels were
poisoned with 1080 bait containing the marker and subsequently fed to
a coyote. The coyote succumbed after 48 h. At least ten micro-
taggants were found in the digestive tract of the coyote, and fecal
samples collected before death were all well marked.