Early Oxidative Stress May Prevent a Red Ornament From Signaling Longevity.

Area of Science:

• Animal behavior
• Physiological ecology
• Evolutionary biology

Background:

• Harsh early environmental conditions can have lasting effects on adult phenotypes, including reproductive traits and sexual signals.
• Red ketocarotenoid colorations, potentially linked to mitochondrial function and oxidative stress, are hypothesized to be reliable signals of individual quality and longevity.
• Antioxidants like glutathione play a crucial role in mitigating oxidative stress, especially during early development.

Purpose of the Study:

• To investigate the correlation between red bill coloration and longevity in captive zebra finches.
• To examine how experimentally inhibited glutathione synthesis during early development affects the relationship between coloration and longevity.
• To determine if red ketocarotenoid-based signals are truly unfalsifiable indicators of condition.

Main Methods:

• Captive zebra finches were used to test the red color-longevity correlation.
• Glutathione synthesis was experimentally inhibited in early life to simulate harsh environmental conditions.
• Bill redness and longevity were recorded for individual birds over approximately nine years.

Main Results:

• Males with redder bills in early adulthood lived longer than those with paler bills.
• This correlation between bill redness and longevity was absent in males whose glutathione synthesis was inhibited early in life.
• No significant correlation was found between bill redness and longevity in females.

Conclusions:

• Environmental factors, such as early oxidative stress, can influence the reliability of sexual signals.
• Red ketocarotenoid-based ornaments may not be as unfalsifiable as previously thought, as their signaling capacity can be modulated by early life conditions.
• The findings highlight the complex interplay between early environment, physiological condition, and the honest signaling of fitness components like longevity.