Keys to set the size of bats


Many endothermic or “warm-blooded” animals, such as mammals, typically have large bodies and short limbs in cold climates to reduce body heat loss. Like other mammals, bats invest energy in keeping their body temperature constant and, in contrast, most species are small in both hot and cold environments.

Measuring thermoregulatory and flight energy expenditure in wild animals is complicated and has made it difficult for the scientific community to understand how energy costs affect the evolution of bat body size. However, an international research team, led by URJC, presented an alternative model that predicts an optimal relationship between animal surface area and body mass.

The team, which includes experts in bat physiology, biogeography and evolution from Spain, Brazil and Mexico, studied the energy costs of bats using a mathematical model in which they simulated the aerodynamics and heat loss of the body and wings of bats. .bats. In this way, the energy required for flight and the heat transferred by the body and wing membranes were modeled.

As URJC researcher Juan G. Rubalcaba explains, “A large wing area to mass increases heat dissipation and the cost of maintaining body temperature, while high mass makes the cost of flight too high”.



Analysis of the relationship between wing area and mass of 278 bat species confirmed the model’s prediction that shape evolves toward an optimal relationship.

Moreover, statistical analyzes integrating relatedness between species have shown that natural selection towards this more favorable relationship is stronger among species from cold climates. The results show that in bats the high energetic costs of flight prevent the evolution towards a high body mass that maintains body heat.

These results, published in the journal Proceedings of the National Academy of Sciences of the United Statesare part of a research program funded by the European Commission (Marie Skłodowska-Curie to Juan G. Rubalcaba from the Laboratory of Biogeography and Global Change) and the Brazilian entities INCT – Ecologia, Evolução e Conservação da Biodiversidade (INCT-EECBio), FAPESP (Fundação de Amparo a Pesquisa do Estado de São Paulo) and CAPES (Coordenação de Perfeiçoamento de Pessoal de Nível Superior).

Character font: URJC-UCC+I, DICYT,

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