Energy acquisition and storage is extremely important for animals living in cold climates (high altitude and/or high latitude): as a matter of  fact, it affects both overwinter survival and reproductive success after hibernation. Differential intraspecific strategies are expected in populations faced with different environmental stressors (i.e.: low-elevation populations vs high-altitude populations). Furthermore, given the different reproductive investment of the sexes, differences in energy allocation are expected between males and females.

In order to  explore the variety of strategies for energy acquisition and allocation in Amphibians, a recent study analyzed 7 populations of plateau brown frog (Rana kukunoris) at different elevations in the Eastern Tibetan Plateau (China). For each site, annual mean temperature was obtained from the WorldClim database.

At the emergence from hibernation, variable numbers of individuals (ranging from 10 to 97) were collected from each population and preliminary sexed at the study site. Upon arrival at the laboratories, the specimens were weighed and their SVL was measured; the tip of a toe was clipped for age determination. After being euthanized, the individuals were dissected to confirm their sex, and their liver and fat bodies were collected and weighed to the nearest 0.1 g. 

Significant differences in the weight of livers and fat bodies were observed both between populations and between sexes. Individuals from higher-altitude populations generally showed heavier liver and fat bodies, suggesting larger energy reserves. Such a strategy might be necessary to survive harsher winters and to cope with extreme weather and less predictable environmental condition. In addition, the authors of the study also hypothesize that the increased energy store in high-elevation population might be indicative of a higher allocation in reproductive efforts in colder climate.

Male Rana kukunoris  in the study area were found to have higher energy stores that females. The difference is due to the different reproductive roles of the two sexes. Females allocate large amounts of energy in egg development before hibernation, thus deplete a large portion of their reserves well before entering the spawning season. Males, on the other hand, display a significant reproductive effort during the mating season, and therefore emerge from hibernation with higher energy reserves. All in all, the study underlines that both environmental conditions and reproductive roles influence energy allocation in Anurans.

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