WELCH, A.M.: What is good about “good genes” in gray tree frogs: How is call duration linked with larval quality?

Male displays traits are predictive of offspring quality in some species, although the basis of the relationship between display traits and offspring quality is not well understood. Female gray tree frogs prefer male calls of long duration, and offspring of males with long calls were of higher quality than were offspring of males with short calls in laboratory experiments. I tested whether variation in tadpole activity and metabolism contributed to an effect of call duration on larval period or mass at metamorphosis. I measured time spent feeding, ingestion rate, digestive efficiency, larval period, and mass at metamorphosis for tadpoles from eight maternal half-sibships (each sired by one long-calling male and one short-calling male) which were raised individually in the lab, at two food levels. In the low food treatment, offspring of long-calling males were larger at metamorphosis than were offspring of short-calling males, but had similar larval periods; in the high food treatment, offspring of long- and short-calling males did not differ in mass at metamorphosis or larval period. At both food levels, tadpoles that spent more time feeding tended to have higher ingestion rates, and tadpoles with higher ingestion rates tended to have shorter larval periods. In the low food treatment, higher digestive efficiency also contributed to shorter larval periods. Time spent feeding, ingestion rate, and digestive efficiency did not affect mass at metamorphosis in either food treatment. Thus, the effect of call duration on mass at metamorphosis detected in this experiment is not attributable to variation in activity, ingestion rate, or digestive efficiency. Nonetheless, variation in ingestion rate may have contributed to an effect of father’s call duration on larval period in previous experiments.