Data from: Pee-cards: a new, inexpensive, and humane technique to index collared lemming abundance

Lemmings drive tundra vertebrate food webs, yet ethical and logistical
constraints still limit spatially explicit monitoring. We introduce and
evaluate a low-cost “pee-card” method that indexes collared lemming
(Dicrostonyx groenlandicus) abundance from urine marks, and compare it
with snap-traps and incidental observations. Across four transects (20
stations each) over three summers (2019, 2023, 2025) at Alert, Nunavut, we
deployed 240 pee-cards per year (3 per station; 720 total) and then placed
snap-traps at the same micro-sites. Each method was run for three
consecutive 24-h periods. Pee-card detections were positively associated
with snap-trap captures, with models including year and transect
explaining additional variation. Using traps as the reference, pee-cards
showed high sensitivity (93%), moderate specificity (52%), and balanced
accuracy of 72%, with very few false negatives. Patterns held with and
without fresh lemming signs of activity. Accumulation curves indicated
that pee-cards saturated by the second 24-h period and, after three
periods, identified presence at more than twice as many stations as traps.
Pee-cards may provide a scalable, non-invasive index of collared lemming
presence and abundance, potentially enabling efficient, ethical monitoring
at broad spatial scales.