Humans aren't the only animals with energy-hungry brains

Robin Smith-Duke, Human Brains Aren't 'Hungrier' Than Other Animals', Futurity, 11.6.17:

Relative to resting metabolic rate—the total amount of calories an animal burns each day just to keep breathing, digesting, and staying warm—the human brain demands more than twice as many calories as the chimpanzee brain, and at least three to five times more calories than the brains of squirrels, mice, and rabbits.

But other animals have hungry brains too.

In terms of relative brain cost, there appears to be little difference between a human and a pen-tailed treeshrew, for example.

Even the ring-tailed lemur and the tiny quarter-pound pygmy marmoset, the world’s smallest monkey, devote as much of their body energy to their brains as we do. [...]

The results suggest that the ability to grow a relatively more expensive brain evolved not at the dawn of humans, but millions of years before, when our primate ancestors and their close relatives split from the branch of the mammal family tree that includes rodents and rabbits, Harrington says.

Based on research in:

Doug M.Boyer and Arianna R.Harrington, Scaling of bony canals for encephalic vessels in euarchontans: Implications for the role of the vertebral artery and brain metabolism, Journal of Human Evolution, Volume 114, January 2018, Pages 85-101, https://doi.org/10.1016/j.jhevol.2017.09.003:

Abstract: Supplying the central nervous system with oxygen and glucose for metabolic activities is a critical function for all animals at physiologic, anatomical, and behavioral levels. A relatively proximate challenge to nourishing the brain is maintaining adequate blood flow. Euarchontans (primates, dermopterans and treeshrews) display a diversity of solutions to this challenge. Although the vertebral artery is a major encephalic vessel, previous research has questioned its importance for irrigating the cerebrum. This presents a puzzling scenario for certain strepsirrhine primates (non-cheirogaleid lemuriforms) that have reduced promontorial branches of the internal carotid artery and no apparent alternative encephalic vascular route except for the vertebral artery. Here, we present results of phylogenetic comparative analyses of data on the cross-sectional area of bony canals that transmit the vertebral artery (transverse foramina). These results show that, across primates (and within major primate subgroups), variation in the transverse foramina helps significantly to explain variation in forebrain mass even when variation in promontorial canal cross-sectional areas are also considered. Furthermore, non-cheirogaleid lemuriforms have larger transverse foramina for their endocranial volume than other euarchontans, suggesting that the vertebral arteries compensate for reduced promontorial artery size. We also find that, among internal carotid-reliant euarchontans, species that are more encephalized tend to have a promontorial canal that is larger relative to the transverse foramina. Tentatively, we consider the correlation between arterial canal diameters (as a proxy for blood flow) and brain metabolic demands. The results of this analysis imply that human investment in brain metabolism (∼27% of basal metabolic rate) may not be exceptional among euarchontans.