Table 1.
Effects of age on foraging behavior, physiology, and reproductive performance in wandering albatross, age 6–48+ years
| Females | Males | Effect of age in selected model (males) | ||||||
| Independent variable | Date | Age | Date | Age | df | Estimate ± SEM | GLM | P |
| Foraging trip (24 males, 24 females) | ||||||||
| Total distance traveled, log | - | - | - | X | 22 | +0.047 ± 0.021 | z = 2.282 | 0.033* |
| Foraging range, log | - | - | - | X | 22 | +0.044 ± 0.019 | z = 2.350 | 0.028* |
| Latitude at maximum range | - | - | - | X | 22 | +0.304 ± 0.110 | F = 7.69 | 0.011* |
| Duration of foraging trip | X | - | - | - | ||||
| Activity at the sea surface (18 males, 22 females) | ||||||||
| Proportion of diurnal time spent on water | - | - | - | - | ||||
| Number of Diurnal Activity Sequences (DASs) per day | - | - | X | - | ||||
| Proportion of time spent on water during DASs | - | - | - | X | 16 | +0.113 ± 0.062 | F = 3.25 | 0.090 |
| Mean DAS duration | - | - | - | - | ||||
| Flying time between 2 DASs | - | - | - | X | 16 | +0.027 ± 0.012 | F = 5.16 | 0.037* |
| Variation of stress hormone levels over a foraging trip | ||||||||
| ∆Corticosterone (19 males, 21 females) | - | - | - | X | 17 | +0.312 ± 0.089 | F = 12.21 | 0.003** |
| Humoral immunity | ||||||||
| Haptoglobin levels (51 males, 37 females) | - | - | - | - | ||||
| Bactericidal activity (23 males, 24 females) | X | - | - | - | ||||
| Agglutination score (22 males, 22 females) | X | - | - | - | ||||
| Lysis score (21 males, 22 females) | - | - | - | - | ||||
| Oxidative stress and antioxidant defenses | ||||||||
| Antioxidant capacity of plasma (52 males, 47 females) | X | - | - | - | ||||
| Lipid peroxidation (53 males, 48 females) | X | - | - | - | ||||
| Superoxid dismutase activity (53 males, 48 females) | - | - | - | - | ||||
| Baseline hormone levels | ||||||||
| Stress hormone (corticosterone; 55 males, 49 females) | - | - | - | - | ||||
| Parental hormone (prolactin; 55 males, 47 females) | X | - | X | X | 52 | +0.660 ± 0.350 | t = 1.89 | 0.064 |
| Reproduction | ||||||||
| Laying date (116 nests) | - | - | - | - | ||||
| Reproductive performance (302 males, 289 females) | - | (age2) | - | age2 | 299 | −0.006 ± 0.001 | z = 6.36 | 0.018* |
Crosses denote which variable(s) appears in the most parsimonious model. Model selection (Tables S1, S2, and S3) shows a male-specific pattern of aging in foraging behavior, activity, and reproductive performance, independent of sampling date. Age2 denotes a quadratic effect of age, with greater statistical support in males than in females. ΔCorticosterone is a hormonal witness of foraging success (Discussion). df, degrees of freedom.
*
P < 0.05;
**
P < 0.01 (GLM).