Larger brains indicate flexibility to adjust to urban areas
.jpg "Photo: Horia Varlan")
AN animal’s ability to acclimatise to urban surroundings is believed to depend on its brain size. Evolutionary biologists have for the first time provided evidence of it.
Alexei A Maklakov and his team from Evolutionary Biology Center, Uppsala University, Sweden, have found that relative brain size in birds is a key predisposing factor to their successful establishment in cities.
The researchers chose passerine or perching birds for the study. They compared the actual brain mass of different birds from 12 cities in Europe, obtained from scientific literature. Estimates of brain size were also obtained from skull measurements given in published data.
The team generated an evolutionary tree representing the ancestral lineage of bird species. Analysis showed that a large brain size is positively linked to city dwelling birds. Birds which breed in at least one city have relatively larger brains and are more likely to belong to large-brained families than their counterparts who avoid urban habitats.
The brainy birds that do well in cities included the tits (Great Tit and Blue Tit), crows (Carrion Crow, Jack-daw, magpie), nuthatch, wren, and the Long-tailed Tit. Bird species with small brains that avoid city centres include buntings (Yellow-hammer, Reed Bunting), warblers (White-throat and Lesser Whitethroat), Pied Flycatcher and Golden Oriole.
“Some birds with relatively small brains do very well in cities, possibly because their ecological niches fit nicely into urban environment. For example, the White Wagtail and the Barn Swallow,” said Maklakov.
Although it is possible that such an effect is mediated through increased size of particular brain structures such as the size of the isocortex, a region of the brain correlated to one’s tendency to innovate, but such details are yet to be explored. The study suggests that birds of small-brain size lineages are exposed to greater risks as a result of urbanisation.
Evolutionary ecologist Suhel Quader from the National Centre of Biological Sciences (NCBS), Bengaluru said, “It would be interesting to see if possible correlates of urban living, like degree of sociality of the different species, and brain size were compared with each other.”
Quader adds that it remains to be seen whether large brains are associated with the specific ability to adjust to human-modified environments or whe-ther large brains enable species to deal more with changing environments.
The findings of the study have been published online in Biology Letters on April 27 this year.
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