Researchers at the University of Southampton have forecast a worldwide move towards smaller birds and mammals over the next 100 years.

Researchers at the University of Southampton have forecast a worldwide move towards smaller birds and mammals over the next 100 years.

In the future, small, fast-lived, highly-fertile, insect-eating animals, which can thrive in a wide-variety of habitats, will predominate. These 'winners' include rodents, such as dwarf gerbil -- and songbirds, such as the white-browed sparrow-weaver. Less adaptable, slow-lived species, requiring specialist environmental conditions, will likely fall victim of extinction. These 'losers' include the tawny eagle and black rhinoceros.

The researchers predict the average (median) body mass of mammals specifically will collectively reduce by 25 per cent over the next century. This decline represents a large, accelerated change when compared with the 14 per cent body size reduction observed in species from 130,000 years ago (the last interglacial period) until today.

Findings are published in detail in the journal Nature Communications.

Rob Cooke is lead author on this work and a postgraduate researcher at the University of Southampton. He comments: "By far the biggest threat to birds and mammals is humankind -- with habitats being destroyed due to our impact on the planet, such as deforestation, hunting, intensive farming, urbanisation and the effects of global warming.