Compensating for a stressful start: maternal corticosterone, offspring survival, and size at fledging in the Zebra Finch, Taeniopygia guttata

Abstract

All organisms are exposed to a variety of physical, environmental and psychological challenges throughout their lives. We administered repeated oral doses of the stress hormone corticosterone (CORT) to ovulating Zebra Finches (Taeniopygia guttata) in order to mimic a disruptive environment, and investigated the effect on their reproductive output as well as outcomes for their offspring. Although females treated with CORT produced larger clutches than control females, hatching success was significantly reduced in the CORT-treated group, though there was no evidence of bias in offspring sex-ratio. Both treatment and sex had an effect on the size of chicks at hatching and their growth rate. Chicks from the experimental group were smaller at hatching than control chicks but grew faster. Similarly, male chicks were smaller than female chicks at hatching but grew faster than females. However, there was no significant difference in overall condition at nutritional independence, indicating that increased growth rates resulted from compensatory growth. These results have broad evolutionary implications, as maternal CORT is capable of affecting viability of eggs and offspring phenotype, even when maternal diet and body condition remain unchanged. As such, glucocorticoids may play a role in regulating population productivity and offspring phenotype, which provides a promising area for further research into the effects of maternal stress on adult offspring in successive generations.

Additional keywords:

• compensatory growth
• embryo mortality
• glucocorticoids
• repeated stress
• survivorship