Telomeres – small sections of protective DNA found at the end of each chromosome – have been repeatedly linked to ageing. But their complex dynamics remain poorly understood, especially in wild populations. Publishing in the journal Ecology and Evolution, researchers in New York studied the length of telomeres and their rate of decline with age in male common yellowthroats (Geothlypis trichas) – a species of warbler – in relation to the size of their bright yellow bib. The bib helps to make male warblers more attractive to females, but the authors found it comes with a cellular cost.
Young male warblers with brighter-coloured bibs tended to have slightly shorter telomeres to start with, and showed a significantly faster rate of telomere decline during the five-year study. This suggests that birds face a trade-off between producing bright plumage and protecting their cellular machinery from free radicals. This trade-off may help ensure that the warblers’ yellow bib is an honest signal of quality to females – only the healthiest males with the best genes can afford the cost of producing a bright bib.
These results add to those from a paper published in Biology Letters last July, which found that in Australian painted dragons (Ctenophorus pictus), males whose head colour faded faster during the 3-month study showed less erosion of their telomeres than those that maintained their bright colouration.
Together these studies are the first to demonstrate a correlation between telomere length and maintenance of a sexual signal, but the causal relationship remains unclear. Sexual signals have been linked to a host of physiological characteristics from immunity to metabolic rate. It isn’t clear yet whether telomere length is another interacting variable, or the overarching factor that links sexual signals like the warblers’ bib to the quality of a male.
It is remarkable that plumage produced in the first weeks of life can convey such accurate information about the condition of telomeres.
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Image by Cephas used under a GNU Free Documentation License 1.2 from Wikimedia Commons.