The Mauritian dodo — a global symbol of human-caused extinction, and one of the world’s largest pigeons — may not have deserved its reputation as silly simpleton and may have been the only member of its group to live in the dark.
An international study led 免费福利资源在线看片 of Lethbridge (Canada) PhD student Sara Citron and Prof. Andrew Iwaniuk in collaboration with Flinders 免费福利资源在线看片’s Weisbecker lab (Australia) and researchers from the Smithsonian Institution, National Museums Scotland, and 免费福利资源在线看片 of Copenhagen has shown that the dodo’s brain was not smaller than expected for a bird of its whopping size. The team also found several traits in its skull and brain that are usually only found in birds that are active at dusk or night.
“Dodos have always been portrayed as silly or confused birds, a reputation that probably came from their trusting behaviour that resulted in hundreds of animals being killed in a very short time,” says lead author Sara Citron. “Otherwise, very little was known about the dodo’s habits and behaviour, so we set out to change that.”
The team used computed tomography (CT) to scan the skulls of three dodos and a range of other pigeons from museums all over the world. They also included the dodo’s closest relative, the extinct Rodrigues solitaire which was the world’s largest pigeon. This allowed them to compare the skull and the imprint of the brain in the skull.
“The dodo has the most unusual skull with a strangely domed head, but the part of its brain that determines cognition was exactly as big as what one would expect for a bird of its size,” says Dr. Andrew Iwaniuk, senior author and Citron’s supervisor. “So, there is no evidence that the dodo was any less intelligent than its relatives — and we know that pigeons are pretty smart.”
The reputation of being a rather dim bird, the authors conclude, is probably due to its fatal tendency to curiously approach other dodos when they were in distress.
“These gentle animals were possibly quite social. Like many island species, they were also used to a life without predators. They may simply have had no reason to learn fearful behaviour,” says Citron. “Calling them “stupid” for being naive makes it sound like they deserved to go extinct, which is so unfair.”
Aside from this perfectly respectable brain size, the dodo’s skull turned out another surprise.
“We suspect that dodos were better adapted to seeing in darker conditions,” says co-author Dr. Vera Weisbecker. “They had slightly larger eyes, but unusually small optic lobes, an area of the brain that processes light. This could mean that its visual abilities are poorer, because small optic lobes often mean that the light reaches the brain through fewer nerves. Scientists suspect that the resulting vision is overall more light-sensitive, but also more “pixelated”. We see similarly small optic lobes in many nocturnal birds, like the Australian Night Parrot or the New Zealand Kakapo.”
These findings are detailed in their recent paper, , published in the Zoological Journal of the Linnean Society. The results give insight into likely dodo behavioural traits.
“We are quite confident that dodos were active at dawn, dusk, or night-time, which would make it the only nocturnal pigeon in the world,” adds Citron. “Perhaps this gave it an advantage over the many strictly day-active turtles that lived on Mauritius –— at night-time, it may have been able to escape competition for food sources with other species, such as the island’s many turtles.”
The team members agree that their results show how much we still have to learn about extinct wildlife.
“We found a range of other traits that we need more data to fully interpret. For example, we suspect that dodos may have relied quite strongly on their sense of smell because the area of the brain related to smell was quite large, unlike the Solitaire and other pigeons. But there just aren’t enough comparative data to truly test this,” says co-author Aubrey Keirnan, a PhD student at Weisbecker’s lab.
By releasing this recent data, the group is encouraging researchers to use it in their own studies to further broaden knowledge of the famous dodo.
“CT scanning is an excellent way to help ancient animal bones housed in the world’s museum collections give up their secrets,” says Weisbecker. “What’s more, we are sharing our 3D data with the world so others can gather more data and build on our research — and maybe learn even more about what the dodo’s world was really like.”