"Long before it's in the papers"
January 27, 2015

RETURN TO THE WORLD SCIENCE HOME PAGE


Rats may take over the world and grow bigger, scientist predicts

Feb. 5, 2014
Courtesy of the University of Leicester
and World Science staff

When the band UB40 asked, “The­re’s a rat in my kitch­en—what am I go­ing to do?” in a 1986 hit sin­gle, they were look­ing for a prac­ti­cal so­lu­tion to a pesky ro­dent prob­lem. An ac­a­dem­ic from the Uni­vers­ity of Leices­ter, U.K. has an an­swer, but it may not be the one the band was hop­ing for.

Jan Za­lasiewicz of the uni­vers­ity’s De­part­ment of Ge­ol­o­gy sug­gests we get used to hav­ing rats around – and that their glob­al in­flu­ence is likely to grow in the fu­ture as larg­er mam­mals con­tin­ue to be­come ex­tinct.

“Rats are one of the best ex­am­ples of a spe­cies that we have helped spread around the world, and that have suc­cess­fully adapted to many of the new en­vi­ron­ments that they found them­selves in,” he said. “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…. they have out-competed many na­tive spe­cies and at times have driv­en them to ex­tinction.”

As a re­sult, ec­o­log­i­cal niches are “be­ing emp­tied – and rats are in a good po­si­tion to re-fill a sig­nif­i­cant chunk of” that space. As rats fill newly opened “eco­space,” he added, they, like many spe­cies of an­i­mal, will adapt and evolve. Changes in size are typ­i­cal in this pro­cess, he not­ed.

“An­i­mals will evolve, over time, in­to what­ev­er de­signs will en­a­ble them to sur­vive and to pro­duce off­spring,” he said. 

“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 [180 lbs]. If the eco­space was suf­fi­ciently emp­ty, then they could get larg­er stil­l.” The larg­est known ex­tinct ro­dent, Jo­seph­oar­te­ga­sia mon­esi, was larg­er than a bull; as an­oth­er com­par­i­son, an an­ces­tor of to­day’s blue whale was a wolf-sized crea­ture liv­ing close to shore.

“An­i­mals can evolve to smaller as well as larg­er sizes,” he added. “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.” So the next time the­re’s a rat in the kitch­en, we should per­haps get used to it – be­cause rats may be here to stay.


* * *

Send us a comment on this story, or send it to a friend

Sign up for
e-newsletter
   
 
subscribe
 
cancel

On Home Page         

LATEST

  • St­ar found to have lit­tle plan­ets over twice as old as our own

  • “Kind­ness curricu­lum” may bo­ost suc­cess in pre­schoolers

EXCLUSIVES

  • Smart­er mice with a “hum­anized” gene?

  • Was black­mail essen­tial for marr­iage to evolve?

  • Plu­to has even cold­er “twin” of sim­ilar size, studies find

  • Could simple an­ger have taught people to coop­erate?

MORE NEWS

  • F­rog said to de­scribe its home through song

  • Even r­ats will lend a help­ing paw: study

  • D­rug may undo aging-assoc­iated brain changes in ani­mals

When Reggae band UB40 asked, “There’s a rat in my kitchen—what am I going to do?” in a 1986 hit single, they were looking for a practical solution to a pesky rodent problem. An academic from the University of Leicester, U.K. has an answer, but it may not be the one the band was hoping for. Jan Zalasiewicz of the university’s Department of Geology suggests we get used to having rats around – and that their global influence is likely to grow in the future as larger mammals continue to become extinct. “Rats are one of the best examples of a species that we have helped spread around the world, and that have successfully adapted to many of the new environments that they found themselves in,” he said. “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…. they have out-competed many native species and at times have driven them to extinction.” As a result, ecological niches are “being emptied – and rats are in a good position to re-fill a significant chunk of” that space. As rats fill newly opened “ecospace,” he added, they, like many species of animal, will adapt and evolve. Changes in size are typical in this process, he noted. “Animals will evolve, over time, into whatever designs will enable them to survive and to produce offspring,” he said. “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 [180 lbs]. If the ecospace was sufficiently empty, then they could get larger still.” The largest known extinct rodent, Josephoartegasia monesi, was larger than a bull; as another comparison, an ancestor of today’s blue whale was a wolf-sized creature living close to shore. “Animals can evolve to smaller as well as larger sizes,” he added. “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.” So the next time there’s a rat in the kitchen, we should perhaps get used to it – because rats may be here to stay.