Songsters with a lust for cheese
It is certainly true that unsubstantiated claims of all sorts of unusual animal behaviours have been made in that past either for reasons of sensationalism or simply because of faulty observations and ignorance. Sometimes, however, observations were correct, but sounded incredulous like for example honey-indicator birds in Africa leading humans to the nests of wild bees, beaver mothers carrying their young on their front paws or the Amphiprion clownfish feeding their sea-anemone partners. Another incredible story is that of singing mice and guinea pigs. Known from several reports in the last century, this behaviour apparently became rarer all the time and now may be at the verge of extinction.
A typical case history is that of Mrs William Le Roy Cahall, a member of the Natural History Museum of New York with a private collection of about 300 live cage birds. So wonderfully conveyed, one evening she heard what sounded like a canary singing from the bird-seed room. But when she opened the door to investigate, she discovered three mice sitting on a seed sac twittering away like birds. The mice were repeatedly heard singing thereafter and became subjects of scientific inquiry. In 1974 the Finnish researcher Alpo Arvola of the Zoological Institute of Helsinki University carried out a thorough study of singing guinea pigs and attempted to explain the unusual phenomenon. Imitation of bird song was one possibility, but why? Was it a warning device, a call for help, something related to hierarchy, a mating call?
The famous Swiss zoologist Heini Hediger likened it to the howl of wolves and dogs in the face of the light of the full moon; others believed that mice and other rodents perhaps sang more frequently than we realized, but that their songs were normally outside our range of auditory perception, in other words were “ultrasonic” vocalizations. More recent investigations have confirmed this latter explanation and moreover have shown that singing male and female mice engage in some kind of “love duet”, in which males start to serenade and females then reply with their own songs. Therefore, the songs must contain some social information, some “meaning”, and are not simply squeaks of pleasure or displeasure. Apparently learning and even varying the songs are involved, but why nowadays only extremely infrequently such songs can be heard by humans remains an enigma.
It is possible that mice in the past have more often sung at lower frequencies and that the lower frequency songs are evolutionarily on their way out, almost extinct by now, having been replaced by higher frequency songs, which are outside our own hearing capacity. But what might have caused this shift, if we assume the notion is correct? Is the overall noisier environment to blame or have there been changes in the physiology of the mice’s ears or their social interactions?Fact is that reports indicate that in some countries singing mice used to be sometimes kept in cages like songbirds. It seems that here is a great opportunity for someone with mice in his/her home to forget about mouse traps and to prick up his/her ears instead to see (or better ‘hear’), if the riddle of the singing mice can’t be solved.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2017.
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