Environmental Seasonality and Mammalian Brain Size Evolution


Ecology has been shown to be among the main drivers of brain size evolution. One important ecological aspect is environmental seasonality. Seasonality is related to brain size evolution in two different ways: On one hand, seasonality acts as energetic constraint on brain size because it forces animals to deal with periodic food shortages (expensive brain hypothesis). On the other hand, seasonality may act as a selective pressure to increase brain size, as cognitive and behavioural flexibility helps to overcome periods of food scarcity (cognitive buffer hypothesis). Current evidence suggests that energetic constraints imposed by environmental seasonality play a crucial role in mammalian brain size evolution, cognitive buffering; on the contrary, seems to be less ubiquitous and is mainly found in large‐brained species such as haplorrhine primates and birds.

Key Concepts

  • Ecology is one of the main drivers of brain size evolution.
  • Whether selection favours large brains depends on whether the fitness benefits of having a large brain exceed the high costs of brain maintenance.
  • Environmental seasonality is both cognitively challenging and energetically expensive.
  • Large‐brained species use their enhanced cognitive abilities in the form of behavioural flexibility to deal with environmental seasonality by keeping food consumption constant throughout the year (cognitive buffer hypothesis).
  • If species face periods of food scarcity, they will not be able to hold the energy supply for a large brain constant. In this situation, seasonality acts as energetic constraint on brain size (expensive brain hypothesis).
  • Seasonality constrains brain size in all mammalian groups investigated so far and might also play a role in other lineages.
  • Cognitive buffering is mainly found in primates and birds.

Keywords: brain size; environmental seasonality; cognitive abilities; cognitive buffer hypothesis; expensive brain hypothesis; behavioural flexibility; energy costs; periodic food shortage; mammals

Figure 1. The consequences of living in a seasonal habitat on energy intake. If the environmental seasonality and hence food resources drop below the minimal energetic need (blue area (a)), subjects can either decrease minimal energetic need (b) or buffer seasonally lean periods by keeping energy intake throughout the year more constant (c). Adapted from van Woerden et al. .


Allman J, McLaughlin T and Hakeem A (1993) Brain weight and lifespan in primate species. Proceedings of the National Academy of Sciences 90: 118–122.

Boutin S and Larsen KW (1993) Does food availability affect growth and survival of males and females differently in a promiscuous small mammal, Tamiasciurus hudsonicus? Journal of Animal Ecology 62: 364–370.

Brodin A and Lundborg K (2003) Is hippocampal volume affected by specialization for food hoarding in birds? Proceedings of the Royal Society B: Biological Sciences 270: 1555–1563.

Byrne RW and Whiten A (1988) Machiavellian Intelligence. Social Expertise and the Evolution of Intellect in Monkeys, Apes, and Humans. Clarendon Press: Oxford, UK.

Deaner RO, Isler K, Burkart JM, et al. (2007) Overall brain size, and not encephalization quotient, best predicts cognitive ability across non‐human primates. Brain, Behavior and Evolution 70: 115–124.

DeCasien AR, Williams SA and Higham JP (2017) Primate brain size is predicted by diet but not sociality. Nature Ecology & Evolution 1: 0112.

Estók P, Zsebők S and Siemers BM (2009) Great tits search for, capture, kill and eat hibernating bats. Biology Letters 6: 59–62.

Fisher J and Hinde RA (1949) The opening of milk bottles by birds. British Birds 42: 347–357.

Garamszegi LZ and Eens M (2004) The evolution of hippocampus volume and brain size in relation to food hoarding in birds. Ecology Letters 7: 1216–1224.

Gillooly JF and McCoy MW (2014) Brain size varies with temperature in vertebrates. PeerJ 2: e301.

Gittleman JL (1986) Carnivore brain size, behavioral ecology, and phylogeny. Journal of Mammalogy 67: 23–36.

Graber SM (2017) Social and Ecological Aspects of Brain Size Evolution ‐ A Comparative Approach. University of Zurich: Zurich.

Gu J, Li DY, Luo Y, et al. (2017) Brain size in Hylarana guentheri seems unaffected by variation in temperature and growth season. Animal Biology 67: 209–225.

Heldstab SA, Kosonen Z, Koski S, et al. (2016a) Manipulation complexity in primates coevolved with brain size and terrestriality. Scientific Reports 6: 24528.

Heldstab SA, van Schaik CP and Isler K (2016b) Being fat and smart: a comparative analysis of the fat‐brain trade‐off in mammals. Journal of Human Evolution 100: 25–34.

Heldstab SA, Isler K and van Schaik CP (2018) Hibernation constrains brain size evolution in mammals. Journal of Evolutionary Biology 31: 1582–1588.

Hemingway CA and Bynum N (2005) The influence of seasonally on primate diet and ranging. In: Brockman DK and van Schaik CP (eds) Seasonality in Primates: Studies of Living and Extinct Human and Non‐human Primates, pp 57–104. Cambridge University Press: Cambridge.

Herculano‐Houzel S (2017) Numbers of neurons as biological correlates of cognitive capability. Current Opinion in Behavioral Sciences 16: 1–7.

Isler K and van Schaik C (2006a) Costs of encephalization: the energy trade‐off hypothesis tested on birds. Journal of Human Evolution 51: 228–243.

Isler K and van Schaik CP (2006b) Metabolic costs of brain size evolution. Biology Letters 2: 557–560.

Isler K and van Schaik CP (2009) The expensive brain: a framework for explaining evolutionary changes in brain size. Journal of Human Evolution 57: 392–400.

Isler K and van Schaik CP (2014) How humans evolved large brains: comparative evidence. Evolutionary Anthropology 23: 65–75.

Jacobs LF and Liman ER (1991) Grey squirrels remember the locations of buried nuts. Animal Behaviour 41: 103–110.

Jacobs LF and Spencer WD (1994) Natural space‐use patterns and hippocampal size in kangaroo rats. Brain, Behavior and Evolution 44: 125–132.

Janmaat KR, Polansky L, Ban SD, et al. (2014) Wild chimpanzees plan their breakfast time, type, and location. Proceedings of the National Academy of Sciences 111: 16343–16348.

Jiang A, Zhong MJ, Xie M, et al. (2015) Seasonality and age is positively related to brain size in Andrew's toad (Bufo andrewsi). Evolutionary Biology 42: 339–348.

Kauffman AS, Bojkowska K and Rissman EF (2010) Critical periods of susceptibility to short‐term energy challenge during pregnancy: impact on fertility and offspring development. Physiology & Behavior 99: 100–108.

Köhler M and Moyà‐Solà S (2004) Reduction of brain and sense organs in the fossil insular bovid Myotragus. Brain, Behavior and Evolution 63: 125–140.

Krebs JR, Sherry DF, Healy SD, et al. (1989) Hippocampal specialization of food‐storing birds. Proceedings of the National Academy of Sciences 86: 1388–1392.

Lukas WD and Campbell BC (2000) Evolutionary and ecological aspects of early brain malnutrition in humans. Human Nature 11: 1–26.

Luo Y, Zhong MJ, Huang Y, et al. (2017) Seasonality and brain size are negatively associated in frogs: evidence for the expensive brain framework. Scientific Reports 7: 16629.

Mai C, Liao J, Zhao L, et al. (2017) Brain size evolution in the frog Fejervarya limnocharis supports neither the cognitive buffer nor the expensive brain hypothesis. Journal of Zoology 302: 63–72.

McGuire LP and Ratcliffe JM (2011) Light enough to travel: migratory bats have smaller brains, but not larger hippocampi, than sedentary species. Biology Letters 7: 233–236.

Milton K (1988) Foraging behaviour and the evolution of primate intelligence. In: Byrne RW and Whiten A (eds) Machiavellian Intelligence: Social Expertise and the Evolution of Intellect in Monkeys, Apes, and Humans, pp 285–305. Clarendon Press: Oxford, UK.

Mink JW, Blumenschine RJ and Adams DB (1981) Ratio of central nervous system to body metabolism in vertebrates: its constancy and functional basis. American Journal of Physiology—Regulatory, Integrative and Comparative Physiology 241: R203–R212.

Navarrete AF, Reader SM, Street SE, et al. (2016) The coevolution of innovation and technical intelligence in primates. Philosophical Transactions of the Royal Society 371: 20150186.

Powell LE, Isler K and Barton RA (2017) Re‐evaluating the link between brain size and behavioural ecology in primates. Proceedings of the Royal Society B: Biological Sciences 284: 20171765.

Reader SM and Laland KN (2002) Social intelligence, innovation, and enhanced brain size in primates. Proceedings of the National Academy of Sciences 99: 4436–4441.

Roth TC and Pravosudov VV (2009) Hippocampal volumes and neuron numbers increase along a gradient of environmental harshness: a large‐scale comparison. Proceedings of the Royal Society B: Biological Sciences 276: 401–405.

Sayol F, Maspons J, Lapiedra O, et al. (2016) Environmental variation and the evolution of large brains in birds. Nature Communications 7.

Sayol F, Downing PA, Iwaniuk AN, et al. (2018) Predictable evolution towards larger brains in birds colonizing oceanic islands. Nature Communications 9: 2820.

Schuck‐Paim C, Alonso WJ and Ottoni EB (2008) Cognition in an ever‐changing world: climatic variability is associated with brain size in Neotropical parrots. Brain, Behavior and Evolution 71: 200–215.

Smith C and Reichman O (1984) The evolution of food caching by birds and mammals. Annual Review of Ecology, Evolution, and Systematics 15: 329–351.

Taylor AB and van Schaik CP (2007) Variation in brain size and ecology in Pongo. Journal of Human Evolution 52: 59–71.

Vincze O (2016) Light enough to travel or wise enough to stay? Brain size evolution and migratory behavior in birds. Evolution 70: 2123–2133.

Volman SF, Grubb TC Jr and Schuett KC (1997) Relative hippocampal volume in relation to food‐storing behavior in four species of woodpeckers. Brain, Behavior and Evolution 49: 110–120.

Weisbecker V, Blomberg S, Goldizen AW, et al. (2015) The evolution of relative brain size in marsupials is energetically constrained but not driven by behavioral complexity. Brain, Behavior and Evolution 85: 125–135.

Weston EM and Lister AM (2009) Insular dwarfism in hippos and a model for brain size reduction in Homo floresiensis. Nature 459: 85.

van Woerden JT, van Schaik CP and Isler K (2010) Effects of seasonality on brain size evolution: evidence from strepsirrhine primates. American Naturalist 176: 758–767.

van Woerden JT, van Schaik CP and Isler K (2014) Brief communication: seasonality of diet composition is related to brain size in New World monkeys. American Journal of Physical Anthropology 154: 628–632.

Zhao CL, Jin L, Zhong MJ, et al. (2018) Cerebellum size is positively correlated with geographic distribution range in anurans. Animal Biology 68: 309–320.

Further Reading

Brockman DK and van Schaik CP (2005) Seasonality in Primates: Studies of Living and Extinct Human and Non‐human Primates. Cambridge University Press: Cambridge, UK.

Burkart JM, Schubiger MN and van Schaik CP (2016) The evolution of general intelligence. Behavioral and Brain Sciences 40: 1–65.

Lefebvre L, Reader SM and Sol D (2004) Brains, innovations and evolution in birds and primates. Brain, Behavior and Evolution 63: 233–246.

Mettke‐Hofmann C (2014) Cognitive ecology: ecological factors, life‐styles, and cognition. Wiley Interdisciplinary Reviews: Cognitive Science 5: 345–360.

Nunn CL (2011) The Comparative Approach in Evolutionary Anthropology and Biology. University of Chicago Press: Chicago and London.

Sol D (2009) The Cognitive‐Buffer Hypothesis for the Evolution of Large Brains. Chicago University Press: Chicago.

Striedter GF (2005) Principles of Brain Evolution. Sinauer: Sunderland, MA.

Wells JC (2010) The Evolutionary Biology of Human Body Fatness: Thrift and Control. Cambridge University Press: Cambridge, UK.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Heldstab, Sandra A, and Isler, Karin(Oct 2019) Environmental Seasonality and Mammalian Brain Size Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0028741]