INTERBREEDING OF house mice from continental Europe and Algeria has resulted in a form of ‘super mouse’ that is resistant to rodent poisons.
The mice have shown up in Spain and in Germany and are likely to spread rapidly, given their ability to survive poisoning.
The mice evolved this resistance through an interbreeding process seldom seen in mammals, according to researchers who studied the mice and published their findings in Current Biology.
Human travel is providing a kind of dating agency service to help bring these distinct rodent species together.
The scientists believe the same process might also produce super rats that can survive dosing with the best rodenticides.
These could already exist but “we just haven’t detected them yet”, said lead researcher Prof Michael Kohn of Rice University in Texas. The European house mouse Mus musculus domesticus and the Algerian mouse Mus spretus do not normally have an opportunity to interbreed and have been genetically disconnected for at least 1.5 million years, the researchers said.
Nature normally prevents cross- breeding in separated species and when it occurs the offspring are usually sterile, something that blocks any further genetic mixing.
This did not stop successful mating between these species however, via a process called “introgressive hybridisation”, the researchers said.
The European mice can occasionally develop some resistance to blood-thinning warfarin-based poisons, but their Algerian cousins already have a strong resistance to warfarin.
Hitch-hiking mice who were travelling with humans moving between Algeria and the Continent most likely allowed the two species to meet and mate.
While most of the resultant offspring were sterile, “a few fertile females” occurred that interbred again and allowed the Algerian poison-resistance gene to move across to European mice, giving them this warfarin resistance, the researchers said.
These super mice are now widespread in Spain and Germany and are likely to spread given their ability to survive warfarin.
The same process could also help rats to develop a similar resistance, the authors said.
Interbreeding between related but distant species will enable this to happen.