Emma Marks

Cohort Profile: Growing Up in New Zealand

Centre for Longitudinal Research – He Ara ki Mua, University of Auckland, Auckland, New Zealand, Growing Up in New Zealand, University of Auckland, Auckland, New Zealand, School of Medicine, University of Auckland, Auckland, New Zealand, Starship Children’s Hospital, Auckland District Health Board, Auckland, New Zealand, School of Population Health, University of Auckland, Auckland, New Zealand, Department of Public Health, School of Medicine and Health Sciences, University of Otago, Wellington, New Zealand, Office of the Deputy Vice-Chancellor (Māori), Massey University, Wellington, New Zealand, Bioinformatics Institute, University of Auckland, Auckland, New Zealand, Ministry of Pacific Island Affairs, Auckland Office, Auckland, New Zealand, Department of Psychology, University of Auckland, Auckland, New Zealand, Roy McKenzie Centre for the Study of Families, Victoria University, Wellington, New Zealand, Department of Psychology, University of Otago, Dunedin, New Zealand and School of Medical Sciences, University of Auckland, Auckland, New Zealand

Ecstatic display calls of the Adélie penguin honestly predict male condition and breeding success

The Adelie penguin ( Pygoscelis adeliae ) breeds in large, noisy Antarctic colonies and has evolved a communication system of complex intra- and inter-sexual visual and vocal behaviours. The Ecstatic Display Call (EDC) given by males whilst at the breeding colony is composed of introductory beats, short repeated syllables and a climactic long syllable. Here, we show that spectral qualities of the short syllables of the EDC can predict body condition and breeding success and suggest that in addition to its role in territory defence, the EDC may function as an honest signal of male quality for female mate choice. In the short repeated syllables frequency modulation, mean frequency, and pitch were all significantly lower in birds of better condition, with frequency modulation changing concomitantly with changing condition during the breeding season. Furthermore, during the period of mate attraction, a males frequency modulation predicted both his latency to pair and likelihood of successfully breeding. Due to the long incubation fasts in this species we propose that female Adelie penguins may reliably use frequency modulation of the EDC as a potentially honest signal of early season male condition and the likelihood of a successful breeding outcome.

Widespread prevalence of a CREBRF variant amongst Māori and Pacific children is associated with weight and height in early childhood

Objective:Investigating a large and ethnically diverse cohort from the Pacific region, we aimed to replicate and extend the recently reported findings that a CREBRF genetic variant is strongly associated with body mass index in Samoans.Methods:A birth cohort of more than six thousand children was utilised. In this study, genotyping of two markers (rs12513649 and rs373863828) was undertaken in Māori, Pacific, European and Asian individuals in the cohort.Results:We report that these CREBRF genetic variants are not confined to Samoans but are prevalent in all other Pacific populations sampled, including Māori. We found that the rs373863828 variant was significantly associated with growth at 4 years of age. On average, we observed allele-specific increases in weight (P=0·004, +455 g, s.e. 0.158), height (P=0·007, +0·70 cm, s.e. 0.26) and waist circumference (P=0·004, +0·70 cm, s.e. 0.24) at 4 years of age. The rs373863828 variant was not associated with birth weight (P=0·129).Conclusions:We replicated the finding that a CREBRF variant is associated with increased body mass. We then built on the original findings by demonstrating the prevalence of the rs12513649 and rs373863828 variants in multiple Pacific population groups and by demonstrating that the rs373863828 variant is associated with growth in early childhood. Pacific population groups experience a disproportionately high burden of obesity, starting in early childhood. This new knowledge offers potential for evidence-based interventions aimed at establishing healthy growth trajectories from the earliest possible age.

Using logistic regression models to predict breeding success in male Adélie penguins (Pygoscelis adeliae)

Measures of breeding success are traditionally derived using the proportion of total nests that successfully reach strategic stages across a breeding season, such as pair formation, egg laying or fledging chicks. The use of logistic regression has recently become a popular tool in avian literature for identifying influential factors that predict nest and/or individual breeding success. In this study, we use logistic regression models to assess the importance of a range of factors affecting male Adélie penguin (Pygoscelis adeliae) breeding success during the 2002–2003 austral summer, when the presence of icebergs and extensive sea-ice meant overall breeding success of Adélie penguins was low (16/51 focal males had chicks reach fledging point). Logistic regression models for the early breeding season showed that good/average nest quality and central/middle nest location within the sub-colony were the best predictors of successful pair formation. Later, during incubation, the most successful males were those that not only returned earlier but were also heavier upon arrival and built nests of at least average quality. During the final stage when chicks had begun to fledge, the combined parameters of heavier male weight, early arrival time and good nest quality were the best predictors of breeding success. The logistic regression approach used here showed that the predictive ability of these parameters varied as the season progressed. However, most importantly, our logistic models fit the data well across all breeding stages.

Agreement between Future Parents on Infant Feeding Intentions and Its Association with Breastfeeding Duration: Results from the Growing Up in New Zealand Cohort Study

Maternal intentions are believed to have the strongest influence on infant feeding. However, what has rarely been studied, are the associations of maternal and partner intentions, and the influence these factors have on infant feeding. Our objective was to describe breastfeeding intentions of pregnant women and their partners, agreement about these intentions, and whether this agreement is associated with breastfeeding initiation and duration. This study was completed within the Growing Up in New Zealand study. Agreement between mothers and partners on intended initial infant feeding method was fair (κ = 0.21, 95% confidence interval (CI) 0.17–0.25) as was intended breastfeeding duration (κ = 0.25, 95% CI 0.22–0.28). Infants whose parents agreed antenatally on breastfeeding only were more likely to have been breastfed for >6 months, after adjustment for maternal (odds ratio (OR) = 6.3, 95% CI 3.9–10.2) and partner demographics (OR = 5.7, 95% CI 3.6–9.2). Likewise, infants whose parents agreed antenatally to breastfeed for >6 months were more likely to have been breastfed for >6 months, after adjustment for maternal (OR = 4.9, 95% CI 3.9–6.2) and partner demographics (OR = 5.0, 95% CI 4.0–6.3). Interventions that promote breastfeeding to both mothers and partners which enable parents to reach agreement about intended feeding methods have the potential to increase both breastfeeding initiation and duration.