Summary: Female red deer with larger brains live longer and have more surviving offspring than those with less endocranial volume, a new study reports.
Source: University of Cambridge.
The size of a female animals’ brain may determine whether they live longer and have more healthy offspring, according to new research led by the University of Cambridge.
The study, published in the Royal Society Open Science journal, shows that female red deer with larger brains live longer and have more surviving offspring than those with smaller brains. Brain size is heritable and is passed down through the generations. This is the first extensive study of individual differences in brain size in wild mammals and draws on data comparing seven generations of deer.
Across species of mammals, brain size varies widely. This is thought to be a consequence of specific differences in the benefits and costs of a larger brain. Mammals with larger brains may, for example, have greater cognitive abilities that enable them to adapt better to environmental changes or they may have longer lifespans. But there may also be disadvantages: for instance, larger brains require more energy, so individuals that possess them may show reduced fertility.
The researchers, based at the University of Cambridge’s Zoology Department and Edinburgh University’s Institute of Evolutionary Biology, wanted to test if they could find more direct genetic or non-genetic evidence of the costs and benefits of large brain size by comparing the longevity and survival of individuals of the same species with different sized brains. Using the skulls of 1,314 wild red deer whose life histories and breeding success had been monitored in the course of a long-term study on the Isle of Rum, they found that females with larger endocranial volumes lived longer and produced more surviving offspring in the course of their lives.
Lead author Dr Corina Logan, a Gates Cambridge Scholar and Leverhulme Early Career Research Fellow in Cambridge’s Department of Zoology, says: “The reasons for the association between brain size and longevity are not known, but other studies have suggested that larger brains are a consequence of the longer-lived species having longer developmental periods in which the brain can grow. These hypotheses were generated from cross-species correlations; however, testing such hypotheses requires investigations at the within-species level, which is what we did.”
Dr Logan adds: “We found that some of the cross-species predictions about brain size held for female red deer, and that none of the predictions were supported in male red deer. This indicates that each sex likely experiences its own set of trade-offs with regard to brain size.”
The study also showed that females’ relative endocranial volume is smaller than that of males, despite evidence of selection for larger brains in females.
“We think this is likely due to sex differences in the costs and benefits related to larger brains,” adds Dr Logan. “We don’t know what kinds of trade-offs each sex might encounter, but we assume there must be variables that constrain brain size that are sex specific, which is why we see selection in females, but not males.”
Professor Tim Clutton-Brock, who set up the Rum Red Deer study with Fiona Guinness in 1972 and initiated the work on brain size, points out that the reason that this kind of study has not been conducted before is that it requires long term records of a large number of individuals across multiple generations and data of this kind are still rare in wild animals.
About this neuroscience research article
Source: Mandy Garner – University of Cambridge Image Source: NeuroscienceNews.com image is credited to Alex Thompson. Original Research: Full open access research for “Endocranial volume is heritable and is associated with longevity and fitness in a wild mammal” by C. J. Logan, L. E. B. Kruuk, R. Stanley, A. M. Thompson, and T. H. Clutton-Brock in Royal Society Open Science. Published online December 14 2016 doi:10.1098/rsos.160622
[cbtabs][cbtab title=”MLA”]University of Cambridge. “Larger Brain Size Linked to Longer Life in Deer.” NeuroscienceNews. NeuroscienceNews, 14 December 2016. <https://neurosciencenews.com/deer-brain-size-longevity-5746/>.[/cbtab][cbtab title=”APA”]University of Cambridge. (20114, December 14). Larger Brain Size Linked to Longer Life in Deer. NeuroscienceNews. Retrieved December 14, 2016 from https://neurosciencenews.com/deer-brain-size-longevity-5746/[/cbtab][cbtab title=”Chicago”]University of Cambridge. “Larger Brain Size Linked to Longer Life in Deer.” https://neurosciencenews.com/deer-brain-size-longevity-5746/ (accessed December 14, 2016).[/cbtab][/cbtabs]
Endocranial volume is heritable and is associated with longevity and fitness in a wild mammal
Research on relative brain size in mammals suggests that increases in brain size may generate benefits to survival and costs to fecundity: comparative studies of mammals have shown that interspecific differences in relative brain size are positively correlated with longevity and negatively with fecundity. However, as yet, no studies of mammals have investigated whether similar relationships exist within species, nor whether individual differences in brain size within a wild population are heritable. Here we show that, in a wild population of red deer (Cervus elaphus), relative endocranial volume was heritable (h2 = 63%; 95% credible intervals (CI) = 50–76%). In females, it was positively correlated with longevity and lifetime reproductive success, though there was no evidence that it was associated with fecundity. In males, endocranial volume was not related to longevity, lifetime breeding success or fecundity.
“Endocranial volume is heritable and is associated with longevity and fitness in a wild mammal” by C. J. Logan, L. E. B. Kruuk, R. Stanley, A. M. Thompson, and T. H. Clutton-Brock in Royal Society Open Science. Published online December 14 2016 doi:10.1098/rsos.160622