Coevolution of relative brain size and life expectancy in parrots

Previous studies have demonstrated a correlation between longevity and
brain size in a variety of taxa. Little research has been devoted to
understanding this link in parrots; yet parrots are well-known for both
their exceptionally long lives and cognitive complexity. We employed a
large-scale comparative analysis that investigated the influence of brain
size and life history variables on longevity in parrots. Specifically, we
addressed two hypotheses for evolutionary drivers of longevity:
the Cognitive Buffer Hypothesis, which proposes that increased
cognitive abilities enable longer life spans, and the Expensive
Brain Hypothesis, which holds that increases in life span are caused by
prolonged developmental time of, and increased parental investment in,
large-brained offspring. We estimated life expectancy from
detailed zoo records for 133,818 individuals across 244
parrot species. Using a principled Bayesian approach that addresses data
uncertainty and imputation of missing values, we found a consistent
correlation between relative brain size and life expectancy in parrots.
This correlation was best explained by a direct effect of relative brain
size. Notably, we found no effects of developmental time, clutch size, or
age at first reproduction. Our results suggest that selection for enhanced
cognitive abilities in parrots have in turn promoted longer lifespans.