Rats as big as sheep: Rodents could evolve to fill niches as larger mammals go extinct
Tuesday 04 February 2014
Scientists believe rats could eventually grow to the size of sheep or even bigger as they evolve to fill vacant ecological niches.
The scenario could become a reality as super-adaptable rats take advantage of larger mammals becoming extinct, an expert predicts.
"Animals will evolve, over time, into whatever designs will enable them to survive and to produce offspring," said geologist Dr Jan Zalasiewicz, from the University of Leicester.
"For instance, in the Cretaceous Period, when the dinosaurs lived, there were mammals, but these were very small, rat and mouse-sized, because dinosaurs occupied the larger ecological niches. Only once the dinosaurs were out of the way did these tiny mammals evolve into many different forms, including some very large and impressive ones: brontotheriums, horses, mastodons, mammoths, rhinoceri and more.
"Given enough time, rats could probably grow to be at least as large as the capybara, the world's largest rodent, that lives today, that can reach 80 kilos (176 pounds). If the ecospace was sufficiently empty, then they could get larger still."
The largest extinct rodent known, Josephoartegasia monesi, which lived three million years ago, was larger than a bull and weighed over a ton. Like its modern-day relative, the sheep-sized capybara, it lived in South America.
A hint of what could be ahead can be seen on "rat islands" - isolated regions where rats introduced by humans have quickly risen to become the dominant species.
"They are now on many, if not most, islands around the world - and once there, have proved extraordinarily hard to eradicate. They're often there for good, essentially. Once there, they have out-competed many native species and at times have driven them to extinction.
"As a result, ecospace is being emptied, and rats are in a good position to re-fill a significant chunk of it, in the mid to far geological future."
Gigantism is a well known evolutionary response that occurs when a small creature steps into an ecological niche left by a larger species. Fifty million years ago, a distant ancestor of the blue whale was the size of a wolf, Dr Zalasiewicz pointed out.
He expected rats to adapt in a host of other ways, besides some of them growing to a large size.
"Animals can evolve to smaller as well as larger sizes," he said. "This will depend on what particular circumstances they find themselves in and what the selective pressures on them are.
"Each island that rats are now present on is in effect a laboratory of future evolution, and each will produce different results.
"So there will be future thin rats, future fat rats, slow and heavy rats, fast and ferocious rats, probably future aquatic rats - the list goes on. Other animals will likely follow the same pattern, such as domestic cats, rabbits, goats and more."
He suspected that rats will have a major influence on the geological future of the Earth and over time were likely to produce "some remarkable descendants".
Humans are a 'plague on Earth': Sir David Attenborough warns that negative effects of population growth will come home to roost
Greenland’s dark snow may start global warming ‘feedback loop’
Cornwall hotter than California? British sea temperatures hit all-time high
Climate change march: Investors pledge to take their money out of firms blamed for climate change
Climate change means rate of growth of trees has gone up by 77%
- 1 Rihanna 'nude photos' claims emerge on 4Chan as hacking scandal continues
- 2 Hilary Mantel 'should be investigated by police' over Margaret Thatcher assassination story, says Lord Bell
- 3 Stamford Hill council removes 'unacceptable' posters telling women which side of the road to walk down
- 4 Kim Kardashian 'nude photos' leaked on 4chan weeks after Jennifer Lawrence scandal
- 5 Scotland could still declare independence – even without referendum, says Alex Salmond
Scottish independence referendum: A nation divided against itself
Scottish referendum results: Cross-party consensus collapses amid Tory-Labour spat on the 'English question'
Scotland could still declare independence – even without referendum, says Alex Salmond
Scottish independence: David Cameron is becoming the 'George Bush of Britain'
Hilary Mantel 'should be investigated by police' over Margaret Thatcher assassination story, says Lord Bell
Plebgate MP Andrew Mitchell called officer a 'little s**t', claim court documents 'exposing ex-Chief Whip's 'record of abusing police'
£120 - £130 per day: Randstad Education Luton: Year 2 maternity cover, startin...
£95 - £150 per day: Randstad Education Birmingham: Key Stage 1 teacher require...
£120 - £150 per day: Randstad Education Birmingham: Upper Key Stage 2 teacher ...
£110 - £130 per day + ?110 - 130: Randstad Education Reading: English Teacher ...