Anderson and Ruxton (Mammal Review, 2020) reviewed the evolution of powered flight and laryngeal echolocation in bats. They hypothesised that powered flight and laryngeal echolocation evolved in separate lineages of handwing gliders. We note that fossil, character evolution, and developmental evidence contradicts their hypothesis, and we test their handwing gliding model, finding it aerodynamically implausible. We conclude that the traditional view of bat evolution (that flight and laryngeal echolocation evolved in the common ancestor of all bats, with the latter being lost in pteropodids) is more plausible than the proposed novel hypothesis.
Bears, Ursidae, are considered omnivores, except for giant pandas Ailuropoda melanoleuca and polar bears Ursus maritimus. However, omnivory includes a wide range of dietary variation and trophic positions, making bear dietary ecology unclear. We inferred bear trophic positions from δ15N (‰) values and examined their correlation with diets reported in the literature, including frequency of human–bear conflicts (livestock predation and crop damage incidents). Overall, 15N signatures were consistent with diet estimates. Bear species with higher 15N signatures differed more from each other, including cases of large regional intraspecific variance, than bear species with lower 15N signatures. Bear trophic position and frequency of reports of human–bear conflicts were uncorrelated, suggesting that livestock predation by bears is an opportunistic behaviour rather than a response to food availability dynamics.
Ecdysteroids are steroid hormones involved in moulting and development of arthropods. Blood samples of 32 individual bats of eight insectivorous species were analysed for the presence of ecdysteroids, using liquid chromatography and mass spectrometry. Nine ecdysteroids were detected. The spectrum of these ecdysteroids was similar in bat species which take their preferred food items from the same insect order. The spectrum of blood-borne ecdysteroids was broader in the autumn than in the summer, and higher concentrations of 20-hydroxyecdysone (the most common ecdysteroid) occurred in samples from large bat species than from small ones. Ecdysteroids may have anabolic effects on insectivorous bats and may also affect their blood-feeding arthropod parasites.
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