Foraging in an oxidative environment: relationship between delta13C values and oxidative status in Adelie penguins

Abstract

The alternation of short/coastal and long/pelagic foraging trips has been proposed as a strategy for seabirds to reconcile self-feeding and parental care. Both types of foraging trips may result in different foraging efforts and diet qualities, and consequently are likely to modify the oxidative status of seabirds. We examined the relationship between the oxidative status of Adélie penguins and (i) the duration of their foraging trips and (ii) their plasma delta(13)C values reflecting their spatial distribution. The oxidative status did not correlate with the foraging trip duration but with the delta(13)C values: high values being associated with high levels of oxidative damage. This relationship is likely to be related to the prey properties of penguins as both parameters are largely determined by the diet. Two non-exclusive hypotheses can be proposed to explain this relationship: (i) penguins foraging in coastal areas feed on a diet enriched in (13)C and depleted in antioxidant compounds; (ii) birds with low antioxidant capacity are constrained to forage in coastal areas. Our study is the first to show that the adoption of different foraging strategies is associated with different levels of oxidative stress. However, further studies are needed to investigate the underlying mechanisms of this intriguing relationship.

Figure 1.

Scatter plots showing the relationships between (a) δ¹³C values and oxidative damage: r = 0.531; p = 0.001. (b) Oxidative damage and antioxidant capacity: r = −0.463; p = 0.005.

Figure 2.

Relationships between the spatial distribution and the oxidative status in male and female Adélie penguins and between males and females within pairs. Solid arrows: significant relationships; dashed arrows: non-significant relationships.

Figure 3.

Oxidative damage (white histograms) and antioxidant capacity (black histograms) in the same group of 11 stable pairs of Adélie penguins in 2006–2007 and 2007–2008.