Balancing energy budgets can be challenging, especially in periods of food shortage, adverse weather conditions and increased energy demand due to reproduction. Bats have particularly high energy demands compared to other mammals and regularly use torpor to save energy. However, while torpor limits energy expenditure, it can also downregulate important processes, such as sperm production. This constraint could result in a trade-off between energy saving and future reproductive capacity. We mimicked harsh conditions by restricting food and tested the effect on changes in body mass, torpor use and seasonal sexual maturation in male parti-coloured bats (Vespertilio murinus). Food-restricted individuals managed to maintain their initial body mass, while in well-fed males, mass increased. Interestingly, despite large differences in food availability, there were only small differences in torpor patterns. However, well-fed males reached sexual maturity up to half a month earlier. Our results thus reveal a complex trade-off in resource allocation; independent of resource availability, males maintain a similar thermoregulation strategy and favour fast sexual maturation, but limited resources and low body mass moderate this latter process.

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The diet of Western human societies is characterized by an excess of saturated fatty acids (FAs) and a high concentration of ω-6 relative to ω-3 polyunsaturated FA (PUFA). These unbalanced diets are suspected to trigger diseases and disorders. To alleviate this public health concern, the production of healthier meat with more PUFAs of higher ω-3 concentration could potentially be achieved by modifying livestock diets. The high nutritional value and limited breeding costs of edible insects have brought insect feed into the discussion as a promising fat source for animal and human diets. In this study, we sought to increase the amount of ω-3 PUFAs in mealworm (Tenebrio molitor) larvae. We investigated the effects of diets varying in ω-3/ω-6 ratio and FA concentration but similar in PUFA proportion on larva FA composition. Mealworm larvae showed significant plasticity in lipid composition. High dietary ω-3/ω-6 ratios induced an increase in the proportion of ω-3 and a decrease in ω-6, which resulted in higher larval ω-3/ω-6 ratios, but also in higher larval PUFA proportion. Increasing FA concentrations in larva diets also favored the accumulation of PUFAs to the detriment of monounsaturated and saturated FAs. Providing ω-3-rich seeds to mealworm larvae could allow the production of economical animal fat with healthier PUFA percentages (> 60%) and ω-3/ω-6 ratios (>0.5).