Who’s Coming Home? Shorter Early-Life Telomeres Predict Return to the Natal Colony in an Arctic Seabird

In wild animals, the length of their telomeres, the noncoding DNA sequences protecting the ends of chromosomes, in early life has been shown to predict their performance (e.g., survival, reproduction) later in life. However, literature has reported mixed relationships between telomere length (TL) and individual performance, possibly because many previous studies overlooked the effects of the resource-modulated trade-off between growth and telomere maintenance. We investigated the effects of early-life conditions (e.g., sibling competition [one or two chicks] and trophic level [nitrogen isotopic values]) on the TL of black-legged kittiwake (Rissa tridactyla) chicks while accounting for the growth-TL trade-off. We also tested whether early-life TL was related to their return probability to the natal colony within 6 yr after fledging (a proxy of survival to adulthood). Although there was no strong evidence for direct effects of the early-life conditions on TL, we found that in broods of two chicks, larger individuals tended to receive a higher-trophic-level diet and have shorter telomeres. This suggests that sibling competition might have imposed stronger resource constraints on the chicks, making them prioritize the limited resources toward growth at the expense of TL. Surprisingly, we found that chicks with shorter telomeres were more likely to return to their colony, whereas body size was not related to return probability, suggesting that TL may be a more comprehensive predictor of return probability than body size. Therefore, our study supports that early-life TL can be a predictor of later-life performance, but it should be used with caution when considering the effect of the resource allocation trade-off with growth, which can influence the direction of prediction.