“This supports the idea that in general larger brains make species more flexible and allow them to live longer,” says Smeele. Because brain size relative to body size can be an indicator for intelligence, the findings suggest that the parrots with relatively large brains had cognitive capabilities that allowed them to solve problems in the wild that could otherwise kill them, and this intelligence enabled them to live longer lives. Their results provide the first support that increased brain size has enabled longer lifespans in parrots. They then combined the data and ran models for each hypothesis, looking at which model best explained the data. For each species, they collected data on relative brain size, as well as average body weight and developmental variables.
Second, that relatively larger brains take longer to grow, and therefore require longer lifespans. In other words, smarter birds can better solve problems in the wild, thus enjoying longer lives. They examined two hypotheses: First, that having relatively larger brains enable longer lifespans. Next, the team employed a large-scale comparative analysis to determine whether or not parrots’ renowned cognitive abilities had any influence on their longevity. These values are really spectacular if you consider that a human male weights about 100 times more.” Comparative analysis “Some individuals have a maximum lifespan of over 80 years, which is a respectable age even for humans.
“Living an average of 30 years is extremely rare in birds of this size,” says Smeele who worked closely with Lucy Aplin from the Max Planck Institute of Animal Behavior and Mary Brooke McElreath from the Max Planck Institute in Leipzig on the study. Other long-lived species include the sulphur crested cockatoo from Australia, which lives on average 25 years. The analysis revealed an astonishing diversity in life expectancy, ranging from an average of two years for the fig parrot up to an average of 30 years for the scarlet macaw. This database allowed the team to gain the first reliable estimates of average life span of 217 parrot species-representing over half of all known species. Together, they compiled data from over 130,000 individual parrots sourced from over 1000 zoos. To generate an adequate sample size, scientists from the Max Planck Institute of Animal Behavior and the Max Planck Institute for Evolutionary Anthropology in Leipzig teamed up with Species360, which draws on animal records from zoos and aquaria. “Comparative life-history studies require large sample sizes to provide certainty, because many processes are a play at once and this creates a lot of variation,” says Smeele. Understanding what has driven parrot longevity is only possible by comparing living parrots. “The problem has been sourcing good quality data,” says Simeon Smeele, a doctoral student at the Max Planck Institute of Animal Behavior and lead author on the study.
Despite the fact that parrots are well known for their long lives and complex cognition, with lifespans and relative brain size on par with primates, it remains unknown whether the two traits have influenced each other.
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