Ecological and histological aspects of tail loss in spiny mice (Rodentia :Muridae, Acomys) with a review of its occurrence in rodents

Many individual nocturnal common spiny mice Acomys cahirinus and diurnal go lden spiny mice A. russatus in the field are found missing all or part of t heir tails. Possibly, this is a predator avoidance mechanism. A 25-month fi eld study revealed that at Fin Gedi (Israel) percentage tail-loss is 63% in male and 44% in female golden spiny mice, and 12% in male and 25% in femal e common spiny mice. Tail loss is significantly more common in golden spiny mice than in common spiny mice, possibly reflecting differences in predati on risk or predator efficiency between the different microhabitats used by these species and in their different activity times. However, inter- and in traspecific aggressive interactions may also account in part for this patte rn. Few significant differences in longevity, body mass, or reproductive co ndition were found between tailed and tail-less spiny mice, suggesting an a dvantage to tail-less individuals. Histological sections revealed a plane s eparating the skin layer from the underlying muscles and vertebrae, facilit ating loss of the skin with little bleeding. The remainder (muscles and bon e) is later chewed off by the mouse. A survey of published cases of tail lo ss in rodents revealed that this phenomenon occurs in at least 35 species a nd has evolved separately in eight rodent families, with no clear pattern i n systematics, geography, or habitat use.