REPRODUCTION AND LIFE-HISTORY IN THE RED-TAILED PHASCOGALE, PHASCOGALE-CALURA (MARSUPIALIA, DASYURIDAE) - THE ADAPTIVE-STRESS SENESCENCE HYPOTHESIS

A population of the red-tailed phascogale (Phascogale calura), a marsu pial with a restricted distribution, was studied during a three-year p eriod at a small reserve in the South-Western Wheatbelt of Western Aus tralia. This species shows a life-history pattern which is typical of many Antechinus species and is characterized by a synchronized winter mating period followed by a complete male post-mating mortality. Matin g occurs during a three-week period in July. In the field, males live only 11.5 months while females may live up to 36 months. Females are m onoestrous and polyovular and have eight teats which are usually all o ccupied by pouch young. The production of supernumerary young is commo n. Pregnant females become aggressive toward the males. To explain the semelparous life history in this species, an adaptive-stress-senescen ce hypothesis is proposed. As males enter the mating period they make major physiological adjustments which are beneficial to the success of mating. However, there may be a longer-term cost, that of hormonally accelerated ageing and senescence, which is finally expressed in impai rment of feedback control of adrenocortical function.