Small mammal species composition data for Niwot Ridge, 1981 - 1990.

Small mammals were live trapped during the summer of each year at
various locations on Niwot Ridge. Species trapped included pikas
(Ochotona princeps), marmots (Marmota flaviventris), deer mice
(Peromyscus maniculatus), voles (Microtus longicaudus, Microtus
montanus, and Phenacomys intermedius), and pocket gophers (Thomomys
talpoides). Pocket gophers were only trapped through the summer of
1983. Mice and voles were trapped using Sherman traps, while Tomahawk
traps were used to trap both the pikas and marmots. Sherman gopher
traps were used to trap gophers. The mice and vole traps were placed
10 meters apart in parallel rows in grids containing from 25 to 100
traps. Weather permitting, the traps were placed for 3 consecutive
nights every 1 or 2 weeks from June to August. The pikas, marmots, and
gophers were trapped during a 10-day census period beginning around 15
August of each year. The traps were selectively placed in areas where
evidence of the animals existed. In the case of the pocket gophers,
the traps were placed below ground in active mounds. The traps were
set during the day, and traplines were run every 2 hours. Consult the
appropriate figures in Halfpenny et al. (1984; 1987) for these trap
locations, as well as descriptions of baiting and handling techniques
and surrounding vegetation communities. After determining and
recording the species, gender, age, reproductive status, weight,
health, and trap location, the animals were permanently tagged and
released. An additional quality-controlled derived data-table
(smammals_no_recap.cr.data.csv) was added to the original dataset in
2022. This data table is derived from the original capture data, but
includes only year-unique captures, where each year-unique capture is
the "best" one for comparison with other year-unique
captures. For comparability among years, the “best” capture for
comparability among years is usually the first capture of the year,
representing the animal's baseline weight for the year (weight appears
to drop rapidly with repeated captures, probably due to
capture-induced stress; this weight-loss is most evident in adults,
because they're no longer growing, but may also affects juvies by
retarding their normal weight gain). These derived data were prepared
by Chris Ray using several lines of evidence to make these
determinations. In some cases determinations were complicated by
eartag loss, etc., and best judgement was used in all cases reviewing
every data entry and make a determination