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Our understanding of state-dependent behaviour is reliant on identifying physiological indicators of condition. Telomeres are of growing interest for understanding behaviour as they capture differences in biological state and residual lifespan. To understand the significance of variable telomere lengths for behaviour and test two hypotheses describing the relationship between telomeres and behaviour (i.e. the causation and the selective adoption hypotheses), we assessed if telomere lengths are longitudinally repeatable traits related to spring migratory behaviour in captive pine siskins ( Spinus pinus ). Pine siskins are nomadic songbirds that exhibit highly flexible, facultative migrations, including a period of spring nomadism. Captive individuals exhibit extensive variation in spring migratory restlessness and are an excellent system for mechanistic studies of migratory behaviour. Telomere lengths were found to be significantly repeatable ( R = 0.51) over four months, and shorter pre-migratory telomeres were associated with earlier and more intense expression of spring nocturnal migratory restlessness. Telomere dynamics did not vary with migratory behaviour. Our results describe the relationship between telomere length and migratory behaviour and provide support for the selective adoption hypothesis. More broadly, we provide a novel perspective on the significance of variable telomere lengths for animal behaviour and the timing of annualmore »
Physiological preparations for migration generally reflect migratory strategy. Migrant birds fuel long-distance flight primarily with lipids, but carrying excess fuel is costly; thus, the amount of fat deposited prior to departure often reflects the anticipated flight duration or distance between refueling bouts. Seasonal pre-migratory deposition of fat is well documented in regular seasonal migrants, but is less described for more facultative species. We analyze fat deposits of free-living birds across several taxa of facultative migrants in the songbird subfamily Carduelinae, including house finches ( Haemorhous mexicanus ), American goldfinches ( Spinus tristis ), pine siskins ( Spinus pinus ) and four different North American ecotypes of red crossbills ( Loxia curvirostra ), to evaluate seasonal fat deposition during facultative migratory periods. Our data suggest that the extent of seasonal fat deposits corresponds with migratory tendency in these facultative taxa. Specifically, nomadic red crossbills with a seasonally predictable annual movement demonstrated relatively large seasonal fat deposits coincident with the migratory periods. In contrast, pine siskins, thought to be more variable in timing and initiation of nomadic movements, had smaller peaks in fat deposits during the migratory season, and the partial migrant American goldfinch and the resident house finch showed no peaksmore »
Building on the predictions of state‐dependent life‐history theory, telomeres are hypothesized to either correlate with or function as an adaptive, proximate mediator of an individual's behaviour and life‐history strategy. To further understand the relationship between telomeres, behaviour and life‐history strategies, we measured male behaviour, telomere lengths and telomere dynamics in a free‐living population of known‐age, male wire‐tailed manakins
Male wire‐tailed manakins perform coordinated displays with other males at leks and these displays form the basis of long‐term coalition partnerships. Males exhibit consistent individual differences in the number of social partners within their social network and the frequency of social interactions. Male sociality is also positively correlated with both social rise and reproductive success.
We measured male behaviour using a telemetry‐based, proximity datalogging system and blood telomere lengths were quantified using qPCR. We examined the relationships between telomere length, telomere dynamics, social status, and male behaviour. We also quantified the repeatability of telomere lengths, examined age‐related changes in telomere length, and tested for instances of telomere elongation that exceed residual error in telomere length.
Telomere length was found to be highly repeatable. More social males exhibited shorter telomeres and higher rates of telomere attrition. Telomeres did not significantly vary with age withinmore »
Here we show that telomeres consistently vary between male wire‐tailed manakins and these differences are related to variation in male social behaviour. In this relatively long‐lived species, telomeres appear to be flexible traits that can increase or decrease in length. Overall, this study provides observational support for the hypothesis that telomeres act as a molecular marker that relates to behaviour in a state‐dependent manner. We also provide insight into the molecular consequences of individual variation in male social behaviour.
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