Circadian activity patterns of Magellanic penguins on land: the influence of light and temperature

ENTRINGER JR, H.; UDRIZAR SAUTHIER, D. E.; VANTREELS, R.E.T.; PUJOL IZQUIERDO, L.; SRBEK-ARAUJO, A.C.; BLANCO, G.

Viña del Mar

Congreso; XI International Penguin Congress; 2023

The activity pattern is evolutionary and responds to the balance between success in feeding, reproduction and predation risk. Therefore, its disturbance can impact the maintenance of populations. We determined if the activity pattern of Magellanic penguins (Spheniscus magellanicus) on land is affected by temperature and light. Data were obtained during 2022-23 breeding season by camera trapping (days=172; hours=4,200) in Cabo dos Bahías, Patagonia, Argentina. Activity peaks (grouping of classes with ≥10% of the total records of the modal class) were defined regarding hourly distribution, temperature, and light categories (night=0, twilight gradient=1 - 4; day=5). The influence of temperature and light on the daily activity (24h) and into night/twilight and daytime was analyzed using regression models. We obtained 1,531 records from which 92.2% were grouped in two activity peaks (%records=45.6/46.6; start=3h/15h; end=11h/23h; mode and mean=7h/19h) associated with sunrise and sunset and with beginning and end at twilight extremes. The temperature in the colony varied between -2 and 43ºC and the activity was unimodal (%records=96.1%; start=5ºC; end=28ºC; mode=15ºC; mean=15.7ºC±6.1). Daily activity was not influenced by light or temperature separately, but responded to their interaction (r2=0.589; F=4.061; p=0.010) increasing during twilight hours as temperature is lower and light starts to intensify. Nocturnal activity increases with light (r2=0.952; F=30.15; p