Pika habitat occupancy survey data for Niwot Ridge and Green Lakes Valley, 2016 - ongoing

Long-term monitoring of habitat occupancy can reveal patterns of
habitat use, population dynamics, and factors controlling species
distribution. The American pika (Ochotona princeps), a small mammal
found in rocky habitats throughout western North America, has been
targeted for occupancy studies due to its relatively conspicuous
behavior and its unusual adaptations for surviving long, cold winters
without hibernation. These adaptations include an unusually high
resting metabolic rate and maintenance of body temperatures near the
lethal maximum for this species, which would appear to compromise the
pika's ability to survive warmer summers. Recent monitoring as well as
projections based on future climate scenarios have suggested this
species is experiencing a period of range retraction due to warming
summers and/or loss of insulating winter snow cover. Niwot Ridge is
situated ideally to test competing hypotheses about the trajectory and
drivers of pika range shift. The pika is still common throughout the
Colorado Rockies, but published models differ markedly regarding
projections of the pika’s future distribution in this region. Niwot
Ridge has experienced warmer summers as well as shorter periods of
insulating snow cover in recent years, and there is evidence that
pikas are now less common than they once were in at least one area on
the ridge. This study is designed to provide robust data on pika
population trends through long-term monitoring of occupancy in a
spatially balanced random sample of pika habitat patches centered on
Niwot Ridge. Survey plots (n = 72) were selected according to a
Generalized Random-Tessellation Stratified (GRTS) algorithm,
stratified dichotomously by elevation, average annual snow
accumulation (SWE), and probabilities of pika occurrence based on
previous data. Each plot extends 12 m in radius from a GRTS point. To
ensure that each plot contains at least 10% cover of talus, plot
coordinates were adjusted (usually less than 50 m) or replaced using
the GRTS oversample to select the next available and suitable plot
within the same categories of elevation, SWE and probability of
occurrence (see
"pika-survey-GRTS-plot-tracking-record.cr.data.csv" for plot
strata, survey schedules, GRTS sequence, and records of plot
replacement or location adjustments). Trained technicians survey plots
for pikas and fresh pika sign (food caches and fecal pellets) as well
as metrics of habitat quality. Each year, 48 of the 72 plots are
surveyed in a rotating panel design (24 plots are surveyed annually,
24 in even years and 24 in odd years). Plots are surveyed in August
when pikas are engaged in food caching and other conspicuous behaviors
related to territory establishment and defense. Data collected at each
plot are detailed in a survey manual
("pika_survey.cr.methods.docx"). Each plot is outfitted with
a data logger (sensor) to record sub-surface temperature several times
each day. Photos of plot and sensor locations are used in navigation
and sensor retrieval. Each survey is completed during a brief
(half-hour) visit to the plot to service the sensor and to record
habitat and pika data. A subset of plots (n = 12) are selected for
double surveys each year to allow estimation of pika detection
probability. Estimates of detection probability are also informed by
data on time to detection of pikas and pika sign recorded during each
survey. Samples of fresh pika fecal pellets are collected from
occupied plots and are stored as vouchers of pika presence and for use
in studies of population genetics and physiology, including studies of
physiological stress in relation to habitat quality and microclimate.