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

HILTON ENTRINGER JR; DANIEL EDGARDO UDRIZAR SAUTHIER; LAIA PUJOL IZQUIERDO; RALPH E.T. VANSTREELS; ANA CAROLINA SRBEK-ARAUJO; GABRIELA BLANCO

Viña del Mar

Congreso; XI International Penguin Congress; 2023

The activity pattern is evolutionarily defined by the interactions with physical and biotic variables, and may be modulated by the success in foraging, reproduction, and predation risk. We investigated the relationship between air temperature (recorded by camera traps) and light in the activity pattern of Magellanic penguins (Spheniscus magellanicus) on land. Data were obtained during 2022-23 breeding season by camera trapping (days=172; hours=4,200) in Cabo dos Bahías (44°55′S 65°33′W), Argentina. Activity patterns were defined regarding hourly distribution, temperature, and light categories (night=0, twilight gradient=1-4; day=5). Activity peaks were defined by grouping classes with ≥10% of the records of the most frequent class. We obtained 1,531 records from which 92.2% had a bimodal distribution peaking: 45.6% of the records from 3:00 (beginning of twilight) to 11:00h, mode and mean=07:00h (sunrise); and 46.6% from 15:00 to 23:00h (end of twilight), mode and mean=19:00h (sunset). Temperature varied between -2 and 43ºC, whereas penguin activity was unimodal with 96.1% of records from 5ºC to 28ºC (mode=15ºC; mean±SD =15.7±6.1). Circadian activity was not influenced by light or temperature separately, but responded to their interaction (R2=0.589; p=0.010) increasing during twilight as temperature is lower and light starts to intensify. At night (19:00h-7:00h), activity increased with light (R2=0.952; p