Supplementary data – Ecdysteroids in the blood of waterfowl, predatory birds, carnivorous mammals and primates – Hornok, 2026

Three further species of road-killed mammalian carnivores were sampled postmortem (n = 15). Finally, blood samples were also drawn and analyzed from six species of water-associated (n = 44) and three species of predatory birds (n = 47). Ecdysteroids were detected in two out of 136 samples: from a Common Kestrel (Falco tinnunculus) that contained 58.9 nM 20-hydroxyecdysone (20E), and from a beech marten (Martes foina) that contained 40.9 nM dacryhainansterone (a phytoecdysteroid).

Although these concentrations do not mean evidence for sustained biological or anabolic effects, 20E was reported to transactivate estrogen receptors β and α with EC50 values of 13.0 and 25.7 nM, respectively. Accordingly, our results show for the first time that ecdysteroids may be present in pharmacologically relevant concentrations in the blood of predominantly carnivorous species of birds and mammals. However, unlike in songbirds and bats which continuously feed on insects, detectable levels of ecdysteroids appear only rarely in the blood of opportunistic insectivores, therefore their health benefits remain questionable in artificially and occasionally insect-fed zoo animals.