Delayed mortality of males in Thylamys bruchi, a semelparous marsupial from Monte desert, Argentina

SOLEDAD ALBANESE; OJEDA, RICARDO A.; ASTIÉ, ANDREA

JOURNAL OF MAMMALOGY

ALLIANCE COMMUNICATIONS GROUP DIVISION ALLEN PRESS

Año: 2020

0022-2372

Male-only obligate semelparity is a well-studied reproductive strategy in some Australian marsupials. Thisstrategy has not been documented in South American species, although semelparity in both sexes occurs in someNeotropical didelphids. The fat-tailed mouse opossum, Thylamys bruchi, is an endemic species of the temperateMonte Desert, in Argentina. Seasonality and predictability of resources are two of the attributes associated withhabitats where marsupial semelparity has evolved, and both are characteristic of the Monte Desert. We aimedto characterize the life-history strategy of T. bruchi to explore if it can be considered a semelparous species. Westudied a fat-tailed mouse opossum population for 7 years with two different capture techniques (Sherman trapsand nest boxes). Thylamys bruchi showed strong seasonality in abundance, with the highest captures duringsummer and autumn. Reproduction and weaning coincided with the most favorable period of the year with respectto climate and resource availability. Every year we observed a single cohort with little overlap until weaning ofyoung. After breeding, all adults disappeared from the population; however, unlike any other didelphids, malesshowed delayed mortality and died, along with females, after weaning. We found no evidence of survival to asecond breeding season for either sex. We therefore propose T. bruchi as a desert-dwelling marsupial with asemelparous reproductive strategy. Because the severity of winters may be acting as an important constraint onthe energetic balance of adults in this population, we propose that challenging climatic conditions, coupled withthe seasonality and high predictability of food resources, may have contributed to the evolution of the extremereproductive strategy in this didelphid marsupial.