INVESTIGADORES
RICCIALDELLI luciana
congresos y reuniones científicas
Título:
Contrasting foraging strategies in Gentoo and Magellanic Penguins breeding in sympatry in the Beagle Channel: niche segregation beyond competition
Autor/es:
RAYA REY ANDREA; HARRIS SABRINA; RICCIALDELLI LUCIANA; SCIOSCIA GABRIELA; SAENZ SAMANIEGO; PUTZ KLEMENS
Lugar:
Ciudad del Cabo
Reunión:
Congreso; 9th International Penguin Congress; 2016
Resumen:
Ecological niche theory predicts niche segregation to avoid potential competition between two closely related organisms. But what to expect when one species population is low in numbers? We investigated if segregation mechanisms exist in two closely related species, the Gentoo Pygoscelis papua and the Magellanic Spheniscus magellanicus penguin. Both species breed in sympatry on Martillo Island, Beagle Channel, Argentina, but while there are more than 6000 Magellanic penguin breeding pairs, the Gentoo colony holds only 31 active nests. We quantified and compared their ecological niche in space (horizontally and vertically) during the early chick rearing period using GPS-TDlogs to determine foraging parameters and stable isotope analysis techniques to investigate their diet. The foraging area, estimated as the 95% kernel density of dives >10m for Gentoo penguins, overlapped completely with the area for dives >5m for Magellanic penguins, while the 50% kernel density did not overlap. Magellanic penguins travelled further away from the colony compared with Gentoo penguins (45 km vs. 23 km), thus on average the trajectory was larger for Magellanic than for Gentoos (117 km vs. 77 km). Nevertheless, the trajectory sinuosity for both species was similar (0.67 for Magellanic and 0.62 for Gentoos). Accordingly, trip duration was longer for Magellanics (25 hs) in comparison to Gentoos (12 hs). Dive profiles revealed that Gentoos performed mainly benthic dives (63% of dives were U-shaped) while Magellanics presented pelagic dive profiles (49% were U-shaped, with W-dives twice as often as in Gentoos). This was also reflected in the bottom time per hour underwater being much higher in Gentoos (17 min/hs) compared with Magellanics (7 min/hs), while the number of wiggles per hour was much higher in Magellanics (33 wiggles/hs vs. 3 wiggles/hs). Mean dive duration also differed, with longer dives performed by Gentoos (80 s vs. 60 s). The differences in diving behaviour were also mirrored in their diet according to the stable isotope analysis. Magellanics consumed more Fuegian sprat (Sprattus fuegensis) while Gentoos preferred benthic prey (lobster Munida spp. krill among others). Our results indicate that segregation mechanisms in two related species persist even when one species is largely outnumbered by the other. This suggests that life history traits and physiological characteristics are strong forces that determine the foraging behaviour of penguins.