What is it about?

The potential influence of the mother's body condition on the social behaviors that earwig offspring direct towards their mother and their siblings. +++++++++++++ Parental care benefits juveniles, but can come at substantial costs for the caring parents. These costs often depend on the parents' condition (parents in poor condition pay higher relative costs of caring), and parental condition is thus considered a key parameter affecting the expression of care during family life. However, how parental condition affects the behaviors that juveniles express toward their siblings and parents remains poorly explored. Here, we investigated this question in the European earwig Forficula auricularia, an insect in which mothers provide extensive forms of care to their juveniles. We measured maternal body condition at egg hatching, subsequently manipulated maternal nutritional state, and finally assessed both the food transfer among siblings and the nature of mother–offspring interactions. We found that food transfer among siblings increased with brood size when the tending mothers were in a deteriorated nutritional state. This effect was masked when the nutritional state of mothers was enhanced. The frequency of care-related behaviors that juveniles expressed toward their mother was higher when she was in a deteriorated rather than an enhanced nutritional state, while it overall increased with brood size. Finally, increasing values of maternal body condition entailed a shift from a positive to a negative association between maternal care behaviors and brood size, but only when the mothers’ nutritional state was deteriorated. Overall, our results demonstrate that parental condition and brood size do not only affect parental behaviors but can also be important and entangled drivers of offspring behaviors during family life.

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Why is it important?

A number of studies have tested the influence of parental body condition on the expression of parental care and the (begging) behavior of offspring toward their parents. However, it remains poorly explored how parental condition affect the behavior of juveniles toward their own siblings. Here, we shed light on this issue by showing that the mother's condition affects the sharing of food among earwig juveniles.


This study illustrates that life-history traits (such as the level of parental care) and environmental conditions (e.g. via their impact on body condition) interact in shaping the complex interplay of behaviors characteristic for family life.

Dr Jos Kramer
ETH Zurich, D-USYS

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This page is a summary of: Maternal condition determines offspring behavior toward family members in the European earwig, Behavioral Ecology, October 2015, Oxford University Press (OUP),
DOI: 10.1093/beheco/arv181.
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