ELEPHANT BIRD OF MADAGSCAR X KIWI

We noticed that, among living birds, optic lobes were only tiny in species that are both flightless and nocturnal, like the kiwi and kakapo,” Torres says. “Thus, we hypothesize that elephant birds, which were very obviously flightless, were also nocturnal.”

First, elephant birds probably inherited some degree of nocturnality from the ancestor they shared with kiwi,” he explains. “Second, competition between species may have caused some species to continue further down the nocturnal evolutionary pathway than others.”

Elephant birds might have also relied on their nocturnal lives to avoid the pesky issue of humans. Torres says while this explanation is less likely that the others, it’s still possible that being nocturnal at least helped them avoid the hunters for a life-saving spell.

Abstract:

The recently extinct Malagasy elephant birds (Palaeognathae, Aepyornithiformes) included the largest birds that ever lived. Elephant bird neuroanatomy is understudied but can shed light on the lifestyle of these enigmatic birds. Paleoneurological studies can provide clues to the ecologies and behaviours of extinct birds because avian brain shape is correlated with neurological function. We digitally reconstruct endocasts of two elephant bird species, Aepyornis maximus and *A. hildebrandti, and compare them with representatives of all major extant and recently extinct palaeognath lineages. Among palaeognaths, we find large olfactory bulbs in taxa generally occupying forested environments where visual cues used in foraging are likely to be limited. We detected variation in olfactory bulb size among elephant bird species, possibly indicating interspecific variation in habitat. Elephant birds exhibited extremely reduced optic lobes, a condition also observed in the nocturnal kiwi. Kiwi, the sister taxon of elephant birds, have effectively replaced their visual systems with hyperdeveloped olfactory, somatosensory and auditory systems useful for foraging. We interpret these results as evidence for nocturnality among elephant birds. Vision was likely deemphasized in the ancestor of elephant birds and kiwi. These results show a previously unreported trend towards decreased visual capacity apparently exclusive to flightless, nocturnal taxa endemic to predator-depauperate islands.