Name: Qianru Liao
Date: 07/14/2026
Time (EST/EDT): 12:00 pm
Location: BRB 1103
Remote Access: email: mees@umd.edu

Committee Chair: William F. Fagan
Committee Members: Maria K. Cameron, Gerald S. Wilkinson, Henry Travis Gallo, Jennifer M. Mullinax
Dean’s Representative: Maria K. Cameron

Title: Frozen Pathways and Reused Routes: Caribou Movement Structure in a Changing Arctic

Abstract: Animal migration depends on the ability of individuals and populations to maintain connectivity across landscapes that change through time. In Arctic systems, this challenge is especially acute because snow, ice, open water, forage, insect harassment, and human disturbance can alter when and where movement is possible. This dissertation examines how dynamic landscape features shape movement-mediated connectivity in barren-ground caribou (Rangifer tarandus groenlandicus) across northern Canada. I combine long-term GPS telemetry, remote sensing, spatial analysis, and movement-network approaches to link individual movement decisions with broader route organization. The second chapter examines how seasonal lake-ice conditions shape caribou water-crossing behavior during migration. Focusing on Contwoyto Lake, I combined 20 years of GPS telemetry from 406 adult caribou with daily MODIS surface albedo to quantify ice conditions along potential crossing paths. Spring crossing decisions were best explained by path-scale ice conditions, with a behavioral threshold at a path-averaged annual albedo percentile rank of 0.56. In fall, when the lake was generally ice-free, movement-related variables better explained crossing versus circumnavigation. These results show that lake ice functions as a seasonal behavioral filter, allowing water bodies to act as temporary bridges during spring migration but as barriers when ice deteriorates or disappears. The third chapter examines post-calving summer route organization. Drawing from a broader telemetry archive of 1,589 individuals and 3,626 summer id-year tracks, I focused on female caribou from four consistently monitored mainland herds: Bathurst, Beverly, Bluenose East, and Bluenose West. I developed a segment-level route-skeleton framework that treats reused route segments as population-level network objects. Repeated summer movement formed an extensive and modular route skeleton. High-use core corridors and use-weighted bottleneck segments represented distinct forms of route-segment importance. Route reuse became more concentrated and connected through time, persistent route features were recovered across temporal blocks, and core corridors had a stronger landscape signature than bottleneck segments. Together, these chapters show that movement-mediated connectivity for Arctic caribou is dynamic, behavioral, and temporally contingent. By linking ice-mediated crossing decisions with long-term route reuse, this dissertation shows how changing landscapes influence immediate movement decisions and the persistence, concentration, and reorganization of movement infrastructure.