Lessons from a Magellanic penguins long-term monitoring in Southern Patagonia: unified methodology, scale-dependent density and stable population trends

RODRIGUEZ PLANES, LI; BARBE, I; VALENZUELA, AEJ; ROSKOS, G; PIMPER, L; MALMIERCA, L

Viña del Mar

Congreso; 11th International Penguin Congress (IPC); 2023

Global Penguin Society

The main touristic attraction of Monte León National Park (MLNP) in Patagonia (Argentina) is the colony of Magellanic penguins (Spheniscus magellanicus), which suffers predation from pumas (Puma concolor). For this reason, the colony is monitored since 2005 to assess population abundance, but using different methodologies during 10 years. Since 2015, a methodology was developed to unify the colony monitoring. Field methodology involves the counting of all nests on 44 fixed 20 m radius circular areas spaced systematically every 100 m in the entire colony, identifying number of occupied nests every concentric radii of 1 m. Total abundance is calculated using the total area of the colony from circles density. Density and abundance estimations of MLNP colony from 2015 to 2021, calculated with radii of 10, 15 and 20 m, are reported. Two analytical methods, quadrat-count and distance sampling with uniform distribution without adjustments, in R language were used. The colony showed no trend over the time, despite puma predation, with 43,764 nests in average (95% CI 31,076 - 56,452). Both methods did not show densities significant differences for each radii, with distance sampling being moretime-consuming for both fieldwork and analysis. Larger radii showed significantly lower values, suggesting a tendency towards regular distribution at 20 m. Results emphasize the scale-dependent nature of density, and highlights the importance ofusing standardized, comparable and cost-effective methods for long-term wildlife populations monitoring.