|SREL Reprint #0266|
Use of Radioactively Tagged Bait to Study Movement Patterns in Small Mammal Populations
John B. Gentry, Michael H. Smith and Robert J.
Small mammal movement patterns were studied on a
14.1 ha grid with 26 lines and rows 676 trap stations) with 15 m intervals
between stations. The study area was located in a lowland mesic-hardwood forest in the southeastern United
States. All stations were prebaited with radioactive peanut butter for five days
prior to the initiation of snap-trapping. The radioactive isotopes 59Fe,
65Zn and 131I were mixed with the peanut butter.
After the five-day prebaiting period, two traps were set at each of 256
stations on the centrally located 16 x 16 (256 station) grid for a period of 18
days. At that time, traps were also
set on the remaining 420 stations arranged in a band around the 16 x 16 grid.
Traps were set on the entire 26 x 26 grid for the last 18 days.
Animals were taken to the laboratory and checked for the presence of
isotopes using a multi-channel pulse-height analyzer.
Most of the animals, consisting mainly of Blarina
brevicauda, were removed within 4 - 8 days. However, certain animals were
difficult to capture. Isotope-labeled
animals were captured on days 21, 25, 30 and 36.
Removal trapping caused animals to move into the grid from the border
zone. Also, many animals captured
on the inner 16 x 16 grid were double isotope-labeled (65Zn-131I).
Many animals captured on the surrounding outer bend were
single-isotope-labeled (I). Also, a
huge proportion of animals captured on the surrounding outer bend wore
Mean minimum distances traveled were calculated to
set a lower limit on movement distances. The
results indicated that the absolute minimum width of the border zone affected by
small mammal removal was about 15 m.
SREL Reprint #0266
Gentry, J.B., M.H. Smith, and R.J. Beyers. 1971. Use of
radioactively tagged bait to study movement patterns in small
mammal populations. Annales Zoologici Fennici 8:17-21.