Born to be young? : Prenatal thyroid hormones increase early-life telomere length in wild collared flycatchers

Acknowledgements: We are grateful to many students and Szymek Drobniak for their help in the field, to three anonymous reviewers for their constructive feedback and to Pat Monaghan for providing access to TRF facilities. Funding: The project was funded by a Marie Sklodowska-Curie Postdoctoral Fellowship (#658085) and a ‘Turku Collegium for Science and Medicine’ Fellowship to AS, and an Academy of Finland grant (# 286278) to SR.Peer reviewedPostprin

Adaptive niche-based sampling to improve ability to find rare and elusive species: Simulations and field tests

This is the peer reviewed version of the following article: Chiffard, Marciau, Yoccoz, Mouillot, Duchateau, Nadeau, Fontanilles, Besnard. Adaptive niche-based sampling to improve ability to find rare and elusive species: Simulations and field tests. Methods in Ecology and Evolution. 2020;11(8):899-909, which has been published in final form at https://doi.org/10.1111/2041-210X.13399. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. Sampling efficiency is crucial to overcome the data crisis in biodiversity and to understand what drives the distribution of rare species.</li Adaptive niche‐based sampling (ANBS) is an iterative sampling strategy that relies on the predictions of species distribution models (SDMs). By predicting highly suitable areas to guide prospection, ANBS could improve the efficiency of sampling effort in terms of finding new locations for rare species. Its iterative quality could potentially mitigate the effect of small and initially biased samples on SDMs. In this study, we compared ANBS with random sampling by assessing the gain in terms of new locations found per unit of effort. The comparison was based on both simulations and two field surveys of mountain birds. We found an increasing probability of contacting the species through iterations if the focal species showed specialization in the environmental gradients used for modelling. We also identified a gain when using pseudo‐absences during first iterations, and a general tendency of ANBS to increase the omission rate in the spatial prediction of the species' niche or habitat. Overall, ANBS is an effective and flexible strategy that can contribute to a better understanding of distribution drivers in rare species. </ol

Acceleration predicts energy expenditure in a fat, flightless, diving bird

Funding The project was supported logistically by the French Polar Institute and funded by the PEW fellowship to Y.R.-C., the WWF-UK, and the Zone Atelier Antarctique et Terres Australes from the CNRS. D.M.W. received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska‐Curie Individual Fellowship Grant Agreement No. 748026.Peer reviewedPublisher PD

Corticosterone levels in relation to trace element contamination along an urbanization gradient in the common blackbird (Turdus merula)

International audienceIn a rapidly urbanizing world, trace element pollution may represent a threat to human health and wildlife, and it is therefore crucial to assess both exposition levels and associated effects of trace element contamination on urban vertebrates. In this study, we investigated the impact of urbanization on trace element contamination and stress physiology in a wild bird species, the common blackbird (Turdus merula), along an urbanization gradient (from rural to moderately urbanized areas). Specifically, we described the contamination levels of blackbirds by 4 non-essential (Ag, Cd, Hg, Pb) and 9 essential trace elements (As, Co, Cr, Cu, Fe, Mn, Ni, Se, Zn), and explored the putative disrupting effects of the non-essential element contamination on corticosterone levels (a hormonal proxy for environmental challenges). We found that non-essential trace element burden (Cd and Pb specifically) increased with increasing urbanization, indicating a significant trace element contamination even in medium sized cities and suburban areas. Interestingly, the increased feather non-essential trace element concentrations were also associated with elevated feather corticosterone levels, suggesting that urbanization probably constrains birds and that this effect may be mediated by trace element contamination. Future experimental studies are now required to disentangle the influence of multiple urban-related constraints on corticosterone levels and to specifically test the influence of each of these trace elements on corticosterone secretion

Effect of prenatal glucocorticoids and thyroid hormones on developmental plasticity of mitochondrial aerobic metabolism, growth and survival: an experimental test in wild great tits

International audienceDevelopmental plasticity is partly mediated by transgenerational effects, including those mediated by the maternal endocrine system. Glucocorticoid and thyroid hormones may play central roles in developmental programming through their action on metabolism and growth. However, the mechanisms by which they affect growth and development remain understudied. One hypothesis is that maternal hormones directly affect the production and availability of energy-carrying molecules (e.g. ATP) by their action on mitochondrial function. To test this hypothesis, we experimentally increased glucocorticoid and thyroid hormones in wild great tit eggs (Parus major) to investigate their impact on offspring mitochondrial aerobic metabolism (measured in blood cells), and subsequent growth and survival. We show that prenatal glucocorticoid supplementation affected offspring cellular aerobic metabolism by decreasing mitochondrial density, maximal mitochondrial respiration and oxidative phosphorylation, while increasing the proportion of the maximum capacity being used under endogenous conditions. Prenatal glucocorticoid supplementation only had mild effects on offspring body mass, size and condition during the rearing period, but led to a sex-specific (females only) decrease in body mass a few months after fledging. Contrary to our expectations, thyroid hormones supplementation did not affect offspring growth or mitochondrial metabolism. Recapture probabilities as juveniles or adults were not significantly affected by prenatal hormonal treatments. Our results demonstrate that prenatal glucocorticoids can affect post-natal mitochondrial density and aerobic metabolism. The weak effects on growth and apparent survival suggest that nestlings were mostly able to compensate for the transient decrease in mitochondrial aerobic metabolism induced by prenatal glucocorticoids

Exploring the interplay between nest vocalizations and foraging behaviour in breeding birds

International audienceIn many bird species, reproductive partners sing together each time they meet on the nest. Because these nest ceremonies typically correspond to the return of one partner from foraging and to the subsequent departure of the other partner, we hypothesized that the foraging decisions of departing birds may be facilitated by the vocalizations accompanying their partner's return on the nest, providing these vocalizations reflect foraging conditions. We examined this hypothesis in pairs of Adélie penguins, Pygoscelis adeliae, by longitudinally monitoring their nest vocalizations and their spatial distribution when foraging at sea across the guard stage, when both parents regularly alternate foraging at sea and chick attendance at the nest. We found that the acoustic characteristics of the vocalizations produced during nest relief ceremonies reflected some characteristics of the foraging trips of both the returning and departing partners. However, these acoustic characteristics differed between partners and were differently related to their foraging behaviour. Accordingly, departing individuals did not adopt the same foraging behaviour as that of returning individuals. Nest vocalizations therefore do not appear to represent cues facilitating the foraging decisions of departing birds, but they may rather reflect the arousal of partners, which differently correlates with the foraging behaviour of the returning and departing individuals. Our study highlights an interplay between the vocalizations produced on the nest by reproductive partners and their foraging behaviour, thereby broadening the scope of animal vocalizations and opening a novel perspective on the regulation of foraging strategies. However, our exploratory study also highlights the complexity of examining this interplay, as the effects of nest vocalizations on foraging decisions may be complicated by other factors (e.g. intrinsic foraging capacity). This calls for the use of additional and experimental approaches (e.g. vocalization playbacks) to clarify the role of nest vocalizations as potential mediators of foraging decisions

Shorter telomeres precede population extinction in wild lizards

International audienceIdentifying the early warning signals of catastrophic extinctions has recently became a central focus for ecologists, but species’ functional responses to environmental changes remain an untapped source for the sharpening of such warning signals. Telomere length (TL) analysis represents a promising molecular tool with which to raise the alarm regarding early population decline, since telomere attrition is associated with aging processes and accelerates after a recurrent exposure to environmental stressors. In the southern margin of their range, populations of the common lizard (Zootoca vivipara) recently became extinct at lowest elevations due to changes in climate conditions. However, the proximal signals involved in these demographic declines are still unknown. Here, we sampled 100 yearling lizards from 10 natural populations (n = 10 per population) along an extinction risk gradient. Relative lizard abundance dramatically dropped over 12 years in low-altitude populations characterized by warmer ambient temperatures and higher body growth of lizards early in life. A non-linear relationship was found between TL and population extinction risk, with shorter telomeres in populations facing high risk of extinction when compared to non-threatened ones. Our results identify TL as an extremely promising biomarker and imply that population extinctions might be preceded by a loop of physiological aging

Body condition and corticosterone stress response, as markers to investigate effects of human activities on Adélie penguins (Pygoscelis adeliae)

Introduction: In Antarctica, there is growing concern about the potential effect of anthropogenic activities (i.e., tourism, research) on wildlife, especially since human activities are developing at an unprecedented rate. Although guidelines exist to mitigate negative impacts, fundamental data are currently lacking to reliably assess impacts. Physiological tools, such as circulating corticosterone levels, appear promising to assess the potential impact of human disturbance on Antarctic vertebrates.Methods: In this study, we compared the body condition, and the physiological sensitivity to stress (i.e., basal and stress-induced corticosterone level) of adult and chick Adélie penguins between a disturbed and an undisturbed area (i.e., 2 colonies located in the middle of a research station exposed to intense human activities and 2 colonies located on protected islands with minimal human disturbance).Results: We did not find any significant impact of human activities on body condition and corticosterone levels in adults (incubating adults, brooding adults). In chicks, there were significant inter-colony variations in stress-induced corticosterone levels. Specifically, the chicks from the disturbed colonies tended to have higher stress-induced corticosterone levels than the chicks from the protected areas although this difference between areas was not significant. In addition, and independently of human disturbance we also found significant differences in adult body condition, and chick corticosterone level between colonies.Discussion: Overall, our study suggests that this species is not dramatically impacted by human activities, at least when humans and penguins have cohabited for several decades. Our results support therefore the idea that this species is likely to be tolerant to human disturbance and this corroborates with the persistence of Adélie penguin colonies in the middle of the research station. However, our results also suggest that chicks might be more sensitive to human disturbance than adults and might therefore potentially suffer from human disturbance. Our study also suggests that specific individual and environmental variables outweigh the potential minor impact of human disturbance on these variables. Combining corticosterone with complementary stress-related physiological markers, such as heart rate, may strengthen further studies examining whether human disturbance may have subtle detrimental impacts on individuals