Prenatal acoustic communication affects thermoregulation capacities in an arid-adapted bird.

Abstract

In birds, embryos use acoustic signals to synchronize hatching, learn calls or even solicit parental care. In zebra finches (Taeniopygia guttata), parents produce a peculiar “heat-call” during incubation at high ambient temperatures, which results in reduced nestling growth, in a temperature-dependent manner. Whilst being smaller may facilitate heat dissipation, we do not know whether being exposed to heat-calls prenatally affects thermoregulatory capacities and heat tolerance, and whether these effects persist into adulthood. Here, we tested the effects of experimentally delivered prenatal playback of heat-calls on thermoregulation at high temperatures at adulthood. We used a respirometry system to measure individuals’ metabolic rate and evaporative water loss at air temperatures (Ta) gradually increasing from 25°C to 44°C, while simultaneously monitoring their body temperature. Remarkably, prenatal exposure to heat-calls affected heat tolerance at adulthood, with individuals exposed to heat-calls as embryos more likely to reach the highest Ta in morning trials. This was despite higher metabolic rate and evaporative water loss in heat-call individuals, partly driven by a stronger metabolic effect of moderate activity. At low Ta, however, heat-call exposed individuals had greater relative water economy, as predicted if heat-calls improve offspring thermoregulatory capacities. These results provide the first evidence that prenatal sound can have long-term effect on thermoregulation. Moreover, our findings point to a novel mechanism underlying developmental plasticity of thermal tolerance.