Breath rate of passerines across an urbanization gradient supports the pace‐of‐life hypothesis and suggests diet‐mediated responses to handling stress

Abstract

The pace‐of‐life hypothesis predicts no impact of urbanization on stress responses. Accordingly, several studies have been inconsistent in showing differences in breath rate (BR), a proxy of acute stress responses to handling in passerines, between rural and urban areas. However, this evidence is limited to a single bird species and a limited geographic region (SW Europe). No study addressed whether this pattern is also apparent in other species or regions, such as in tropical environments, or whether it is dependent on the level of diet specialization, given that diet restriction and change influence stress responses. Here, we tested whether there were differences in BR between habitats and diet groups using eight highly diverse passerine assemblages experiencing different levels of anthropogenic disturbance (i.e., natural, rural, and urban locations) in SW China. We predicted that insectivores and herbivores (frugivores, nectarivores, and seed‐eating species) would show higher BR than omnivores. We also predicted no differences in BR among habitat types. BR was a moderately repeatable trait, which showed a negative relationship with body mass and a positive relationship with the time of the day. We also recorded a relatively strong phylogenetic bias in the expression of this trait. Confirming our predictions, our results showed no differences in BR among natural, rural, and urban locations. Similarly, within species, there were no differences in BR between rural and urban locations. However, we also found that herbivores showed higher BR than omnivores. Overall, our results provide support to the pace‐of‐life hypothesis, but suggest acute stress responses can be diet‐mediated, which may help to explain the marked decline of specialized trophic guilds around the world in response to anthropogenic disturbance.

Wake respirometry may quantify stress and energetics of free-living animals

“…There is abundant literature on how amniote breathing frequency, together with tidal volume, modulates metabolic rate (Hallam & Dawson 1993; Kohin, Williams & Ortiz 1999); on its uses in the measurement of stress responses (Greenacre & Lusby 2004; Fucikova et al . 2009; Torné- Noguera, Pagani-Núñez & Senar 2013; Doss & Mans 2016; Doss & Mans 2017; Liang et al . 2018); its involvement in temperature regulation ((El Hadi & Sykes 1982; Brent et al .…”

Wake respirometry allows breath-by-breath assessment of ventilation and CO2 production in unrestrained animals

“…There is abundant literature on how amniote breathing frequency, together with tidal volume, is modulated to meet metabolic demands (Hallam and Dawson, 1993;Kohin et al, 1999); on its uses in the measurement of stress responses (Greenacre and Lusby, 2004;Fucikova et al, 2009 , 2016Liang et al, 2018); its involvement in temperature regulation (El Hadi and Sykes, 1982;Brent et al, 1984;Bucher and Bartholomew, 1986); entering, and arousing from, torpor (Withers, 1977); and how it scales with body mass (Frappell and Baudinette, 1995;Frappell et al, 2001;Mortola and Seguin, 2009). Here, we demonstrate that a NoDIS system can be used to quantify real-time changes in respiration rate with breath-by-breath resolution when the sensor is positioned in the wake of an animal, rather than integrated into a mask or alternative system that requires restraint or tethering (Butler et al, 1977;Franz and Goller, 2003;Wilson et al, 2019).…”

From maternal glucocorticoid and thyroid hormones to epigenetic regulation of gene expression: an experimental study in a wild bird species

“…Nestlings were visited 2, 7, and 14 days after hatching for identification, phenotypic measurements (weight, wing length) and blood sampling (day 7 and 14) as described in Cossin-Sevrin et al (2022). Additionally, 14 days after hatching, we measured handling stress response as a proxy of different stress-related coping strategies (Carere & van Oers 2004;Fucikova et al 2008) by calculating the individual's breath rate (see below) in response to handling (Carere & van Oers 2004;Fucikova et al 2008;Liang et al 2018). Breath rate was measured from one to three randomly-selected chicks per nest, immediately after taking each individual from the nest (before other measurements) following the protocols described in Carere and van Oers (2004) and Fucikova et al (2009).…”

“…The role of receptor methylation in mediating the effects of prenatal thyroid hormones has received less attention in previous studies: Van Herck et al (2012) discovered that TH supplementation to chicken egg yolk increased TH concentration in the brains of chicken embryos 24h after manipulation and altered TH membrane transporter expression; however, the effects on thyroid hormone receptor (THR, transcribed by THRA and THRB) expression or methylation have not been investigated. The few studies (Ahmed et al 2014;Zimmer & Spencer 2014;Van Herck et al 2012) that have addressed the epigenetics of prenatal hormonal effects by directly manipulating the egg hormone concentrations have (1) mainly focused on glucocorticoids, and (2) hormone manipulation occurred when incubation already started. Manipulations during incubation do not mimic maternal deposition and could lead to different effects since CORT and TH are likely to be at least partly metabolized by the growing embryos (CORT: Vassallo et al 2019;TH: Ruuskanen et al 2022).…”