Abstract
Many species show individual variation in neophobia and stress hormones, but the causes and consequences of this variation in the wild are unclear. Variation in neophobia levels could affect the number of offspring animals produce, and more subtly influence the rearing environment and offspring development. Nutritional deficits during development can elevate levels of stress hormones that trigger long-term effects on learning, memory, and survival. Therefore measuring offspring stress hormone levels, such as corticosterone (CORT), helps determine if parental neophobia influences the condition and developmental trajectory of young. As a highly neophobic species, jackdaws (Corvus monedula) are excellent for exploring the potential effects of parental neophobia on developing offspring. We investigated if neophobic responses, alongside known drivers of fitness, influence nest success and offspring hormone responses in wild breeding jackdaws. Despite its consistency across the breeding season, and suggestions in the literature that it should have importance for reproductive fitness, parental neophobia did not predict nest success, provisioning rates or offspring hormone levels. Instead, sibling competition and poor parental care contributed to natural variation in stress responses. Parents with lower provisioning rates fledged fewer chicks, chicks from larger broods had elevated baseline CORT levels, and chicks with later hatching dates showed higher stress-induced CORT levels. Since CORT levels may influence the expression of adult neophobia, variation in juvenile stress responses could explain the development and maintenance of neophobic variation within the adult population.
Highlights
Neophobia, or the fear of novelty, allows animals to avoid unknown danger, but may prevent the exploitation of new resources (Greenberg and Mettke-Hofmann, 2001)
The majority of evidence for connections between object neophobia and fitness come from studies in which behavioral measures and/or subsequent reproductive success were assessed in captivity (Bremner-Harrison et al, 2004; Janczak et al, 2003; Korhnonen et al, 2002; Korhonen and Niemela, 1996; Korhonen et al, 2001)
We examined the connections between parental neophobia levels, provisioning rates, and breeding success in wild breeding jackdaws
Summary
The fear of novelty, allows animals to avoid unknown danger, but may prevent the exploitation of new resources (Greenberg and Mettke-Hofmann, 2001). Even if parents’ neophobia does not influence the net number of chicks they produce per season, it could still broadly impact the quality of the rearing environment and the subsequent physiological stress responses of their offspring. Such influences are critical to determining the potential costs and benefits of neophobic behavior because the effects of developmental impairment could occur after chicks fledge. Instead neophobic variation could influence offspring in other, less direct ways by reducing provisioning rates to an extent that impacts fledging chicks’ body condition or alters baseline circulating CORT and juveniles’ propensity to mount a stress-induced hormone response. Even if parents’ neophobia does not directly impact chicks’ survival in the nest, it could have other long-term impacts on offspring development that would explain selection for or against neophobic behavior
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