Stress exposure in early post-natal life reduces telomere length: an experimental demonstration in a long-lived seabird

Exposure to stressors early in life is associated with faster ageing and reduced longevity. One important mechanism that could underlie these late life effects is increased telomere loss. Telomere length in early post-natal life is an important predictor of subsequent lifespan, but the factors underpinning its variability are poorly understood. Recent human studies have linked stress exposure to increased telomere loss. These studies have of necessity been non-experimental and are consequently subjected to several confounding factors; also, being based on leucocyte populations, where cell composition is variable and some telomere restoration can occur, the extent to which these effects extend beyond the immune system has been questioned. In this study, we experimentally manipulated stress exposure early in post-natal life in nestling European shags (Phalacrocorax aristotelis) in the wild and examined the effect on telomere length in erythrocytes. Our results show that greater stress exposure during early post-natal life increases telomere loss at this life-history stage, and that such an effect is not confined to immune cells. The delayed effects of increased telomere attrition in early life could therefore give rise to a ‘time bomb’ that reduces longevity in the absence of any obvious phenotypic consequences early in life

Skin temperature reveals the intensity of acute stress

Acute stress triggers peripheral vasoconstriction, causing a rapid, short-term drop in skin temperature in homeotherms. We tested, for the first time, whether this response has the potential to quantify stress, by exhibiting proportionality with stressor intensity. We used established behavioural and hormonal markers: activity level and corticosterone level, to validate a mild and more severe form of an acute restraint stressor in hens (Gallus gallus domesticus). We then used infrared thermography (IRT) to non-invasively collect continuous temperature measurements following exposure to these two intensities of acute handling stress. In the comb and wattle, two skin regions with a known thermoregulatory role, stressor intensity predicted the extent of initial skin cooling, and also the occurrence of a more delayed skin warming, providing two opportunities to quantify stress. With the present, cost-effective availability of IRT technology, this non-invasive and continuous method of stress assessment in unrestrained animals has the potential to become common practice in pure and applied research

Dietary antioxidants in life-history trade-offs: differential effects of a-tocopherol supplementation on blue tit Cyanistes caeruleus mothers and offspring during reproduction

α-Tocopherol is assumed to be the most biologically active dietary antioxidant in vivo, but despite its potential importance little is known about its impacts on wild birds. Reproduction is presumed to be costly for parents through several routes, including increased oxidative stress, particularly for bird species producing large clutches. If dietary antioxidants can ameliorate oxidative stress associated with reproduction, mothers supplemented with dietary antioxidants are predicted to be in improved condition and/or invest more resources in reproduction than controls. We provided adult blue tit pairs with an α-tocopherol-enriched or control food supplement during nest building and egg laying, then cross-fostered half broods between treatment groups to test the theory that α-tocopherol-supplemented mothers would invest more in self-maintenance or reproduction than controls. We found that α-tocopherol supplementation had no effect on the maternal condition or reproductive investment. However, effects on nestlings were evident: nestlings from α-tocopherol-supplemented mothers were smaller at hatching. There was no effect on chick fledging mass, fledging success or lipid peroxidation, but the catch-up growth exhibited by chicks from α-tocopherol-supplemented parents may be considered costly. Thus, our results do not provide evidence for a benefit of maternal α-tocopherol supplementation at a biologically relevant dose on either themselves or their offspring. We discuss our findings in terms of ongoing research on the multifaceted roles that dietary ‘antioxidants’ can have in vivo, and the issues of disentangling their impacts on physiology and behaviour in the wild

Parental age influences offspring telomere loss

1. The age of the parents at the time of offspring production can influence offspring longevity, but the underlying mechanisms remain poorly understood. The effect of parental age on offspring telomere dynamics (length and loss rate) is one mechanism that could be important in this context. 2. Parental age might influence the telomere length that offspring inherit or age-related differences in the quality of parental care could influence the rate of offspring telomere loss. However, these routes have generally not been disentangled. 3. Here, we investigated whether parental age was related to offspring telomere dynamics using parents ranging in age from 2 to 22 years old in a free-living population of a long-lived seabird, the European shag (Phalacrocorax aristotelis). By measuring the telomere length of offspring at hatching and towards the end of the post-natal growth period, we could assess whether any potential parental age effect was confined to the post-natal rearing period. 4. There was no effect of maternal or paternal age on the initial telomere length of their chicks. However, chicks produced by older mothers and fathers experienced significantly greater telomere loss during the post-natal nestling growth period. We had relatively few nests in which the ages of both parents were known, and individuals in this population mate assortatively with respect to age. Thus, we could not conclusively determine whether the parental age effect was due to maternal age, paternal age, or both; however, it appears that the effect is stronger in mothers. 5. These results demonstrate that in this species, there was no evidence that parental age was related to offspring hatching telomere length. However, telomere loss during nestling growth was reduced in the offspring of older parents. This could be due to an age-related deterioration in the quality of the environment that parents provide, or because parents that invest less in offspring rearing live to an older age

Individual variation in corticosterone and personality traits in the blue tit Cyanistes caeruleus

Source: Variation in personality traits is predicted to reflect physiology, but the extent to which variations in stress hormones derive from differences in personality and/or state-dependent factors remains unclear. To investigate this, wild blue tits (Cyanistes caeruleus) were briefly brought into captivity and scored for personality and corticosterone (Cort) concentrations. More active females had lower baseline Cort than less active individuals. Exploratory tendency and neophobia did not co-vary with baseline Cort. Stress-induced Cort concentrations were correlated negatively with exploratory tendency and haematocrit, but positively with mass gain in captivity. Therefore, baseline and stress-induced Cort concentrations in wintering blue tits were associated with state-dependent variables, sex, age and personality traits. Key to interpreting the physiology of personality traits seems to be their interactions with other traits that mediate ability to utilise resources, and thus influence an individual’s perception of its current and future energy balance

State education policy 1900-1930 The nature of the socialist and teacher trade unionist response

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Personality predicts behavioral flexibility in a fluctuating, natural environment

In captivity, personality types differ in behavioral flexibility: “fast” (neophilic, exploratory, and aggressive) types quickly form routines, whereas “slow” types continually adjust their behavior with environmental changes. If these differences extend to pertinent natural environmental changes, which indicate changing predation or starvation threat, then personality may reflect important variation in how animals manage risk. We examined whether personality traits classified in captivity would predict the behavioral flexibility of blue tits Cyanistes caeruleus as they foraged in the wild. Behavioral flexibility was defined as the tendency to adjust feeder use with changing winter air temperature, an indicator of starvation risk. At the population level, birds reduced their feeder use on warm days. Individuals, though, varied widely, with some instead using feeders at a relatively fixed, temperature-independent rate. Sex and size, correlates of dominance in blue tits, did not predict behavioral flexibility. Instead, behavioral flexibility was predicted by age and 2 personality traits: old, neophobic, and exploratory birds were more behaviorally flexible than young, neophilic, and nonexploratory birds. Our findings suggest that personality types differ in how they use information about their environments and hence cope with environmental change

Oxidative profile varies with personality in European greenfinches

Where behavioural responses differ consistently between individuals, this is termed 'personality'. There is the suggestion, but with little supporting data, that personality traits reflect underlying variation in physiology. Here, we tested whether greenfinches Carduelis chloris differing in personality traits differed in various plasma indices of oxidative profile: antioxidant capacity (OXY), pro-oxidant status (reactive oxygen metabolites, ROMs), oxidative stress (OS) and an end-product of oxidative damage: malondialdehyde (MDA). We measured two personality traits: neophobia (latency to approach food near novel objects) and object exploration (latency to approach novel objects). These traits were uncorrelated. ROMs, OXY, OS and MDA were also uncorrelated with each other. Highly neophobic birds had lower OXY, higher ROMs and higher OS than less neophobic birds. Fast exploring birds had higher OXY than slow explorers, but did not differ in ROMs or OS. Variation in MDA was described by a quadratic relationship with neophobia: birds with extremely high or low neophobia had lower MDA than birds with intermediate neophobia, despite highly neophobic birds exhibiting lower OS than intermediately neophobic birds. Additively in that model, fast explorers had lower MDA than slower explorers. To conclude: first, personality types can differ in oxidative profile. Second, although physiological differences (e. g. hormonal stress responsiveness) between personality types generally range along a linear continuum, physiological costs may not. Finally, relationships with oxidative profile differed between neophobia and object exploration. Understanding how oxidative profile and thus physiological costs vary within and between personality traits may explain how differences in personality traits can predict fitnes

Data from: Do glucocorticoids predict fitness? Linking environmental conditions, corticosterone and reproductive success in the blue tit, Cyanistes caeruleus

Glucocorticoids, including corticosterone (CORT), have been suggested to provide a physiological link between ecological conditions and fitness. Specifically, CORT, which is elevated in response to harsh conditions, is predicted to be correlated with reduced fitness. Yet, empirical studies show that CORT can be non-significantly, positively and negatively linked with fitness. Divergent environmental conditions between years or study systems may influence whether CORT is linked to fitness. To test this, we monitored free-living blue tits (Cyanistes caeruleus) during breeding over 3 years. We quantified foraging conditions during brood rearing, and examined whether they were correlated with parental baseline CORT and reproductive success. We then tested whether CORT predicted fitness. Elevated parental CORT was associated with lower temperatures, greater rainfall and lower territory-scale oak density. Whereas asynchrony with the caterpillar food peak was correlated with reduced nestling mass and fledging success, but not parental CORT. Only low temperatures were associated with both reduced nestling mass and elevated parental CORT. Despite this, parents with elevated CORT had lighter offspring in all years. Contrarily, in 2009 parental CORT was positively correlated with the number fledged. The absence of a direct link between the foraging conditions that reduce nestling quality and elevate parental CORT suggests that parental CORT may provide a holistic measure of conditions where parents are working harder to meet the demands of developing young. As the positive correlation between parental CORT and fledging success differed between years, this suggests that contrasting conditions between years can influence correlations between parental CORT and fitness. Ultimately, as CORT concentrations are intrinsically variable and linked to the prevalent conditions, studies that incorporate environmental harshness will improve our understanding of evolutionary endocrinology