Clare Andrews

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Developmental history, energetic state and choice impulsivity in European starlings, Sturnus vulgaris

Animal Cognition

Chronological age, biological age, and individual variation in the stress response in the European starling: a follow-up study

PeerJ

The strength of the avian stress response declines with age. A recently published study of Europe... more The strength of the avian stress response declines with age. A recently published study of European starlings (Sturnus vulgaris) found that a marker of biological age predicted the strength of the stress response even in individuals of the same chronological age. Specifically, birds that had experienced greater developmental telomere attrition (DTA) showed a lower peak corticosterone (CORT) response to an acute stressor, and more rapid recovery of CORT levels towards baseline. Here, we performed a follow-up study using the same capture-handling-restraint stressor in a separate cohort of starlings that had been subjected to a developmental manipulation of food availability and begging effort. We measured the CORT response at two different age points (4 and 18 months). Our data suggest a decline in the strength of the CORT response with chronological age: peak CORT was lower at the second age point, and there was relatively more reduction in CORT between 15 and 30 min. Individual cons...

Developmental history and stress responsiveness are related to response inhibition, but not judgement bias, in a cohort of European starlings (Sturnus vulgaris)

Animal Cognition

Early-life begging effort reduces adult body mass but strengthens behavioural defence of the rate of energy intake in European starlings

Royal Society open science, 2018

Animals require strategies for coping with periods when food is scarce. Such strategies include s... more Animals require strategies for coping with periods when food is scarce. Such strategies include storing fat as a buffer, and defending the rate of energy intake by changing foraging behaviour when food becomes difficult to obtain. Storage and behavioural defence may constitute alternative strategies for solving the same problem. We would thus expect any developmental influences that limit fat storage in adulthood to also induce a compensatory alteration in adult foraging behaviour, specifically when food is hard to obtain. In a cohort of hand-reared European starlings, we found that higher manipulated early-life begging effort caused individuals to maintain consistently lower adult body mass over a period of two years. Using an operant foraging task in which we systematically varied the costs of obtaining food, we show that higher early-life begging effort also caused stronger behavioural defence of the rate of energy intake when food was more costly to obtain. Among individuals wit...

Evaluating the cyclic ratio schedule as an assay of feeding behaviour in the European starling (Sturnus vulgaris)

PloS one, 2018

The cyclic ratio (CR) schedule is a behavioural assay developed to study feeding in rats, in whic... more The cyclic ratio (CR) schedule is a behavioural assay developed to study feeding in rats, in which the number of operant responses required to obtain food reward (the ratio requirement) increases and then decreases in a repeating cycle. In a recent study, we used the CR schedule with European starlings (Sturnus vulgaris) to investigate the effects of an early-life manipulation on adult feeding behaviour. As this was the first time the CR schedule had been used with any bird species, a more in-depth evaluation is warranted. Here, we performed a fuller CR experiment with the same birds as the prior study, a year later. First, we examine the individual consistency of feeding behaviour between experimental sessions and also between CR schedules comprising different ratio requirement progressions. We found that between-session consistency was poor to moderate, and that a geometric ratio progression provided greater between-session consistency than an arithmetic ratio progression. Second,...

A marker of biological age explains individual variation in the strength of the adult stress response

Royal Society open science, 2017

The acute stress response functions to prioritize behavioural and physiological processes that ma... more The acute stress response functions to prioritize behavioural and physiological processes that maximize survival in the face of immediate threat. There is variation between individuals in the strength of the adult stress response that is of interest in both evolutionary biology and medicine. Age is an established source of this variation-stress responsiveness diminishes with increasing age in a range of species-but unexplained variation remains. Since individuals of the same chronological age may differ markedly in their pace of biological ageing, we asked whether biological age-measured here via erythrocyte telomere length-predicts variation in stress responsiveness in adult animals of the same chronological age. We studied two cohorts of European starlings in which we had previously manipulated the rate of biological ageing by experimentally altering the competition experienced by chicks in the fortnight following hatching. We predicted that individuals with greater developmental ...

Dissociating the effects of alternative early-life feeding schedules on the development of adult depression-like phenotypes

Scientific reports, 2017

Early-life adversity is associated with increased vulnerability to depression in humans, and depr... more Early-life adversity is associated with increased vulnerability to depression in humans, and depression-like phenotypes in animals. However, different types of adverse experience may leave different signatures in adulthood. We experimentally manipulated the Amount of food delivered to European starling nestlings and the begging Effort required to obtain food during early development. Here, we report behavioural data in adulthood from a task that assessed sensitivity to shifts in reward magnitude characteristic of depression-like low mood. Birds that had experienced Hard Effort were more food motivated than birds that had experienced Easy Effort. Both Effort and Amount affected sensitivity to shifts in reward magnitude: Hard Effort birds showed an enhanced negative contrast effect following loss of reward ('disappointment'), and Lean Amount birds failed to show a normal positive contrast effect following gain in reward (a lack of 'elation'). Therefore, the feeding sch...

Adaptive principles of weight regulation: Insufficient, but perhaps necessary, for understanding obesity

Behavioral and Brain Sciences

We reflect on the major issues raised by a thoughtful and diverse set of commentaries on our targ... more We reflect on the major issues raised by a thoughtful and diverse set of commentaries on our target article. We draw attention to the need to differentiate between ultimate and proximate explanation; the insurance hypothesis (IH) needs to be understood as an ultimate-level argument, although we welcome the various suggestions made about proximate mechanisms. Much of this response is concerned with clarifying the interrelationships between adaptationist explanations like the IH, constraint explanations, and dysfunction explanations, in understanding obesity. We also re-examine the empirical evidence base, concurring that it is equivocal and only partially supportive. Several commentators offer additional supporting evidence, whereas others propose alternative explanations for the evidence we reviewed and suggest ways that our current knowledge could be strengthened. Finally, we take the opportunity to clarify some of the assumptions and predictions of our formal model.

Effects of early life adversity and sex on dominance in European starlings

Animal Behaviour

Evolution of elaborate parental care: phenotypic and genetic correlations between parent and offspring traits

Behavioral ecology : official journal of the International Society for Behavioral Ecology

The evolution of elaborate forms of parental care is an important topic in behavioral ecology, ye... more The evolution of elaborate forms of parental care is an important topic in behavioral ecology, yet the factors shaping the evolution of complex suites of parental and offspring traits are poorly understood. Here, we use a multivariate quantitative genetic approach to study phenotypic and genetic correlations between parental and offspring traits in the burying beetle Nicrophorus vespilloides. To this end, we recorded 2 prenatal traits (clutch size and egg size), 2 postnatal parental behaviors (direct care directed toward larvae and indirect care directed toward resource maintenance), 1 offspring behavior (begging), and 2 measures of breeding success (larval dispersal mass and number of dispersing larvae). Females breeding on larger carcasses provided less direct care but produced larger larvae than females breeding on smaller carcasses. Furthermore, there were positive phenotypic correlations between clutch size, direct, and indirect care. Both egg size and direct care were positive...

Early-life adversity accelerates cellular ageing and affects adult inflammation: Experimental evidence from the European starling

Scientific reports, Jan 17, 2017

Early-life adversity is associated with accelerated cellular ageing during development and increa... more Early-life adversity is associated with accelerated cellular ageing during development and increased inflammation during adulthood. However, human studies can only establish correlation, not causation, and existing experimental animal approaches alter multiple components of early-life adversity simultaneously. We developed a novel hand-rearing paradigm in European starling nestlings (Sturnus vulgaris), in which we separately manipulated nutritional shortfall and begging effort for a period of 10 days. The experimental treatments accelerated erythrocyte telomere attrition and increased DNA damage measured in the juvenile period. For telomere attrition, amount of food and begging effort exerted additive effects. Only the combination of low food amount and high begging effort increased DNA damage. We then measured two markers of inflammation, high-sensitivity C-reactive protein and interleukin-6, when the birds were adults. The experimental treatments affected both inflammatory markers...

Brood size moderates associations between relative size, telomere length, and immune development in European starling nestlings

Ecology and Evolution, 2016

Food insecurity as a driver of obesity in humans: The insurance hypothesis

The Behavioral and brain sciences, Jan 28, 2016

Integrative explanations of why obesity is more prevalent in some sectors of the human population... more Integrative explanations of why obesity is more prevalent in some sectors of the human population than others are lacking. Here, we outline and evaluate one candidate explanation, the insurance hypothesis (IH). The IH is rooted in adaptive evolutionary thinking: the function of storing fat is to provide a buffer against shortfall in the food supply. Thus, individuals should store more fat when they receive cues that access to food is uncertain. Applied to humans, this implies that an important proximate driver of obesity should be food insecurity rather than food abundance per se. We integrate several distinct lines of theory and evidence that bear on this hypothesis. We present a theoretical model that shows it is optimal to store more fat when food access is uncertain, and we review the experimental literature from non-human animals showing that fat reserves increase when access to food is restricted. We provide a meta-analysis of 125 epidemiological studies of the association bet...