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.