Abstracts: 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 lifespans, and the expensive brain hypothesis, which holds that increases in lifespan 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 has in turn promoted longer lifespans.

Simeon Q Smeele 1 2 3 4Dalia A Conde 4 5 6Annette Baudisch 4Simon Bruslund 7 8Andrew Iwaniuk 9Johanna Staerk 4 5 6Timothy F Wright 10Anna M Young 11Mary Brooke McElreath 1 2Lucy Aplin 1 12 13

Proc Biol Sci. 2022 Mar 30;289(1971): 20212397.doi: 10.1098/rspb.2021.2397. Epub 2022 Mar 23.

1Cognitive and Cultural Ecology Research Group, Max Planck Institute of Animal Behavior, Radolfzell, Germany.

2Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.

3Department of Biology, University of Konstanz, Konstanz, Germany.

4Interdisciplinary Centre on Population Dynamics, University of Southern Denmark, Odense, Denmark.

5Department of Biology, University of Southern Denmark, Odense, Denmark.

6Species360 Conservation Science Alliance, Bloomington, IN, USA.

7Vogelpark Marlow gGmbH, Marlow, Germany.

8Parrot Taxon Advisory Group, European Association of Zoos and Aquaria, Amsterdam, The Netherlands.

9Department of Neuroscience, University of Lethbridge, Lethbridge, Canada.

10Biology Department, New Mexico State University, Las Cruces, NM, USA.

11The Living Desert Zoo and GardensPalm Desert, Palm Desert, CA, USA.

12Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany.

13Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, Australia.

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