Vocal panting: a novel thermoregulatory mechanism for enhancing heat tolerance in a desert-adapted bird

Animals thriving in hot deserts rely on extraordinary adaptations and thermoregulatory capacities to cope with heat. Uncovering such adaptations, and how they may be favoured by selection, is essential for predicting climate change impacts. Recently, the arid-adapted zebra finch was discovered to program their offspring’s development for heat, by producing ‘heat-calls’ during incubation in hot conditions. Intriguingly, heat-calls always occur during panting; and, strikingly, avian evaporative cooling mechanisms typically involve vibrating an element of the respiratory tract, which could conceivably produce sound. Therefore, we tested whether heat-call emission results from a particular thermoregulatory mechanism increasing the parent’s heat tolerance. We repeatedly measured resting metabolic rate, evaporative water loss (EWL) and heat tolerance in adult wild-derived captive zebra finches (n = 44) at increasing air temperatures up to 44 °C. We found high within-individual repeatability in thermoregulatory patterns, with heat-calling triggered at an individual-specific stage of panting. As expected for thermoregulatory mechanisms, both silent panting and heat-calling significantly increased EWL. However, only heat-calling resulted in greater heat tolerance, demonstrating that “vocal panting” brings a thermoregulatory benefit to the emitter. Our findings therefore not only improve our understanding of the evolution of passerine thermal adaptations, but also highlight a novel evolutionary precursor for acoustic signals

A prenatal acoustic signal of heat reduces a biomarker of chronic stress at adulthood across seasons

During development, phenotype can be adaptively modulated by environmental conditions, sometimes in the long-term. However, with weather variability increasing under climate change, the potential for maladaptive long-term responses to environmental variations may increase. In the arid-adapted zebra finch, parents emit “heat-calls” when experiencing heat during incubation, which adaptively affects offspring growth in the heat, and adult heat tolerance. This suggests that heat-call exposure may adjust individual phenotype to hot conditions, potentially compromising individual sensitivity to cool weather conditions. To test this hypothesis, we manipulated individual prenatal acoustic and postnatal thermal experiences during development, and sought to assess subsequent chronic responses to thermal fluctuations at adulthood. We thus measured heterophil to lymphocyte (H/L) ratios in adults, when held in outdoor aviaries during two summers and two winters. We found that birds exposed to heat-calls as embryos, had consistently lower H/L ratios than controls at adulthood, indicative of lower chronic stress, irrespective of the season. Nonetheless, in all birds, the H/L ratio did vary with short-term weather fluctuations (2, 5 or 7 days), increasing at more extreme (low and high) air temperatures. In addition, the H/L ratio was higher in males than females. Overall, while H/L ratio may reflect how individuals were being impacted by temperature, heat-call exposed individuals did not show a stronger chronic response in winter, and instead appeared more resilient to thermal variability than control individuals. Our findings therefore suggest that heat-call exposure did not compromise individual sensitivity to low temperatures at adulthood. Our study also reveals that prenatal sound can lead to long-term differences in individual physiology or quality/condition, as reflected by H/L ratios, which are consistent with previously-demonstrated reproductive fitness differences

A prenatal acoustic signal of heat afects thermoregulation capacities at adulthood in an arid‑adapted bird

Understanding animal physiological adaptations for tolerating heat, and the causes of interindividual variation, is key for predicting climate change impacts on biodiversity. Recently, a novel mechanism for transgenerational heat adaptation was identified in a desert-adapted bird, where parents acoustically signal hot conditions to embryos. Prenatal exposure to “heat-calls” adaptively alters zebra finch development and their thermal preferences in adulthood, suggesting a long-term shift towards a heat-adapted phenotype. However, whether such acoustic experience improves long-term thermoregulatory capacities is unknown. We measured metabolic rate (MR), evaporative water loss (EWL) and body temperature in adults exposed to a stepped profile of progressively higher air temperatures (Ta) between 27 and 44 °C. Remarkably, prenatal acoustic experience affected heat tolerance at adulthood, with heat-call exposed individuals more likely to reach the highest Ta in morning trials. This was despite MR and EWL reaching higher levels at the highest Ta in heat-call individuals, partly driven by a stronger metabolic effect of moderate activity. At lower Ta, however, heat-call exposed individuals had greater relative water economy, as expected. They also better recovered mass lost during morning trials. We therefore provide the first evidence that prenatal acoustic signals have long-term consequences for heat tolerance and physiological adaptation to heat.The Australian Research Council, the Holsworth Wildlife Research Endowment and international travel costs by the National Research Foundation of South Africa.https://www.nature.com/srepdm2022Zoology and Entomolog

Using an Electronic Monitoring System to Link Offspring Provisioning and Foraging Behavior of a Wild Passerine

Although the costs of parental care are at the foundations of optimal-parental-investment theory, our understanding of the nature of the underlying costs is limited by the difficulty of measuring variation in foraging effort. We simultaneously measured parental provisioning and foraging behavior in a free-living population of Zebra Finches (Taeniopygia guttata) using an electronic monitoring system. We fitted 145 adults with a passive transponder tag and remotely recorded their visits to nest boxes and feeders continuously over a 2-month period. After validating the accuracy of this monitoring system, we studied how provisioning and foraging activities varied through time (day and breeding cycle) and influenced the benefits (food received by the offspring) and costs (interclutch interval) of parental care. The provisioning rates of wild Zebra Finches were surprisingly low, with an average of only one visit per hour throughout the day. This was significantly lower than those reported for this model species in captivity and for most other passerines in the wild. Nest visitation rate only partially explained the amount of food received by the young, with parental foraging activity, including the minimum distance covered on foraging trips, being better predictors. Parents that sustained higher foraging activity and covered more distance during the first breeding attempt took longer to renest. These results demonstrate that in some species matching foraging activity with offspring provisioning may provide a better estimate of the true investment that individuals commit to a reproductive attempt

Thermal acclimatisation to heatwave conditions is rapid but sex-specific in wild zebra finches

DATA AVAILABILITY : Data are available on Mendeley: https://data.mendeley.com/datas ets/ kn6m7 cg2p8/1.Under climate change, increasing air temperature average and variability pose substantial thermal challenges to animals. While plasticity in thermoregulatory traits could potentially attenuate this impact, whether thermal acclimatisation can occur quickly enough to track weather variability in hot climates is unknown in any endotherm, and sex differences have never been tested. We investigated acclimatisation responsiveness of male and female wild zebra finches to short-term (< 2 weeks) summer temperature fluctuations in the Australian desert. Hotter weather before respirometry trials triggered a typical acclimatisation response (especially at chamber temperature Tchamb ≥ 40). However, acclimatisation occurred remarkably rapidly: metabolic rate responded within just one day, while body temperature ( Tb) and evaporative cooling capacity (EHL/MHP) were best predicted by weather on the trial day; whereas evaporative water loss responded more slowly (1 week). Nonetheless, rapid acclimatisation only occurred in males, and females had higher Tb and lower EHL/MHP than males, potentially increasing hyperthermia risk. Furthermore, acclimatisation did not translate into greater acute heat tolerance (i.e. ability to tolerate Tchamb = 46 °C). Our results therefore reveal surprisingly rapid acclimatisation and even anticipatory adjustments to heat. However, with no changes in acute heat tolerance, and in females, phenotypic flexibility may provide only limited buffering against the detrimental impact of heatwaves.The Holsworth Wildlife Research Endowment, the Australian Research Council and the Spanish Ministry of Science and Innovation grant.https://www.nature.com/srepam2024Zoology and EntomologySDG-13:Climate actio

The Adaptive significance of provisioning and foraging coordination between breeding partners

Sexual conflict over parental care relies on the fundamental assumption that parents do not share the cost of their partner’s effort on future reproduction. However, this is unlikely to be true whenever partners breed together more than once. In that case, individuals should try to optimize the cost and benefits for the pair, rather than only for themselves. Here we seek to establish whether the synchronization of parents’ provisioning visits to the nest could fulfill this function. We conducted a brood-size manipulation experiment on wild zebra finches to test whether nest visit synchrony was flexible and beneficial for nestlings’ growth, while controlling for the confounding effects of pair “quality” and synchrony away from the nest during foraging. Using a network of readers to track parents at nests and feeding stations, we found that nest visit synchrony responded directly to the brood manipulation and increased with brood size. Synchrony at the nest and while foraging were correlated, but the latter better predicted nestling mass, possibly because it was associated with more regular provisioning patterns. Our findings suggest that parental coordination could indeed play an important role in partners’ investment decisions, underpinning the evolution of the most prominent mating system in birds.11 page(s

Good vibrations in the nest

Exposing wild-caught eggs to audio playbacks in the lab reveals that avian embryos can communicate predation risk to their siblings before hatching. This prenatal communication, which possibly occurs through vibrational cues, coordinates the developmental trajectories of the clutch

all Datasets for Mariette Buchanan 2016 (1 per page)

page1: occurrence and duration of incubation calls in relation to ambient temperature and time to expected hatch date. page2: nestling mass from day 1 to 13 in relation to playback and nest temperature. page 3: survival to day 13 in relation toplayback and temperature. page 4: nestling begging in relation to playback and nest temperature. page 5: breeding output female year 1. page 6: breeding output female year 2. page 7: breeding output male year 1. page 8: breeding output male year 2. page 9: nest site selection year 1. page 10: nest site selection year 2

Calling in the heat: The zebra finch incubation call depends on heat and reproductive stage - A comment on McDiarmid et al. 2018

Calling in the heat: The zebra finch incubation call depends on heat and reproductive stage - A comment on McDiarmid et al. 201