Novel object trials are commonly used to assess aversion to novelty (neophobia), and previous work has shown neophobia can be influenced by the social environment, but whether the altered behaviour persists afterwards (social learning) is largely unknown in wild animals. We assessed house sparrow ( Passer domesticus ) novel object responses before, during and after being paired with a conspecific of either similar or different behavioural phenotype. During paired trials, animals housed with a similar or more neophobic partner demonstrated an increased aversion to novel objects. This change did not persist a week after unpairing, but neophobia decreased after unpairing in birds previously housed with a less neophobic partner. We also compared novel object responses to non-object control trials to validate our experimental procedure. Our results provide evidence of social learning in a highly successful invasive species, and an interesting asymmetry in the effects of social environment on neophobia behaviour depending on the animal's initial behavioural phenotype.

There is good evidence that telomeres predict variation in health and longevity, yet it is unclear whether these patterns are causally derived from telomeres per se, in part because relatively little research directly manipulates telomere length during early life, when telomere shortening is most dynamic. Here, we test how the telomerase activator TA‐65 (i.e. cycloastrogenol) affects telomere length in five tissues during the peak of growth in the wild tree swallow Tachycineta bicolor. Following eight days of oral TA‐65 administration, chicks experienced telomere lengthening in the blood and accelerated feather growth, but no changes to mass over time. TA‐65 did not affect telomere length in the brain or spleen and led to shorter telomeres in the liver and adrenals. This whole‐organism experimental manipulation of telomere dynamics therefore reveals limitations to telomere protection and biological senescence. In doing so, this work advances our understanding of early‐life telomere dynamics and their potential role in generating future variation in health and lifespan.

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