Tracking movements in an endangered capercaillie population using DNA-tagging

Knowing the location and movements of individuals at various temporal and
spatial scales is an important facet of behavior and ecology. In
threatened populations, movements that would ensure gene flow and
population viability are often challenged by habitat fragmentation. Also
in those endangered populations capturing and handling individuals to tag
them, or to obtain tissue samples, can present additional challenges. DNA
tagging, i.e. non-invasive individual identification of samples, can
reveal movement patterns. We used fecal material genetically assigned to
individuals to indirectly track movements of a large-bodied, endangered
forest bird, Cantabrian capercaillie (Tetrao urogallus cantabricus). We
wanted to know how the birds were using the fragmented forest landscape,
and whether they showed fidelity to display areas. We used multi-event
capture-recapture models to estimate fidelity to display areas among three
consecutive mating seasons. We identified 127 individuals, and registered
movements of 22 females and 48 males. Most observed movements were as
expected relatively short, concentrated around display areas. We did not
find differences in movement distances between females and males within
mating seasons, or between them. Fidelity to display areas among seasons
was 0.62 (± 0.12 SE) for females and 0.77 (± 0.07 SE) for males. The best
CR model suggested no sex or season effects. Several longer movements, up
to 9.9 km, linked distant display areas, demonstrating that Cantabrian
capercaillies were able to move between different parts of the study area,
complementing previous studies on gene flow. Those longer movements may be
taking birds out of the study area, and into historical capercaillie
territories, which still include substantial forest cover. The
non-invasive DNA tagging approach provided a much larger sample size than
would have been feasible with direct tracking. Lack of information on the
social status of individuals and timing of movements are some
disadvantages of DNA tagging.