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".
Sales of the tablet are set to fall again, say analysts
World's most lethal spider found under a bunch of bananas
I Am Bread could actually be a challenging and nuanced title
Company decides to go for simply scary after criticising other sites for 'creepy and targeted' advertising
Footage shot by a passerby shows moment an ill man was carried out of his burning home
Peter Biaksangzuala died from his injuries in hospital on Sunday
- 1 Jack the Ripper: Scientist who claims to have identified notorious killer has 'made serious DNA error'
- 2 Ebola outbreak: What is bushmeat – and is it to blame for the disease that has killed thousands?
- 3 Star Wars memorabilia called a 'bit of plastic' on Antiques Roadshow by Fiona Bruce valued at £50,000
- 4 Meet Thea, Norway's 12-year-old child bride
- 5 Russell Brand might seem like a sexy revolutionary worth getting behind, but he will only fail his fans
Cameron is warned 'no possibility' of UK reducing immigration and that bid to bring in quota on migrant workers would be illegal
Sorry Judy Finnigan – Ched Evans is no less sickening than an alleyway rapist
Residents should throw a street party and mix with immigrant neighbours, councils told
Workers 'could be forced to pay £5 a week' to get benefits
Russell Brand threatened with arrest after filming outside Fox News headquarters
Amal Alamuddin calls for the return of the Elgin Marbles from Britain: 'Injustice has persisted for too long'
£35000 - £40000 per annum: Sauce Recruitment: As the Programmatic Business Dev...
£110 - £130 per day + Competitive rates of pay: Randstad Education Reading: Ma...
£110 - £130 per day + TBA: Randstad Education Reading: Geography Teacher neede...
£50 - £70 per day: Randstad Education Preston: This role has arisen due to inc...