Apparent chitin digestibilities in the Eastern screech owl (Otus asio) and the American kestrel (Falco sparverius)

Abstract

Chitin, which is found in arthropod exoskeletons as a structural and defensive material, is one of the most abundant carbohydrates in nature. Chitin digestibility was studied in two partially insectivorous raptors, Eastern Screech Owls (Otus asio) and American Kestrels (Falco sparverius). When owls were fed crab shell chitin (5% or 2% of total dried food, by weight), 10.6 ± 7.1% (SD) to 30.4 ± 7.8% was digested (species digestibility means were 26.2 ± 4.4% and 18.6 ± 6.6%). Kestrels consuming a 5% or 2% chitin diet had 15.7 ± 3.9 to 25.7 ± 5.3 percent digestibilities. The mean apparent digestibilities for kestrels were 18.5 ± 2.5% and 22.3 ± 3.0%, respectively, for the 5% and 2% chitin diets. In an effort to improve chitin digestibilities in owls and kestrels, chitin was added to daily meals for 3 or 6 weeks, but no statistically significant increase in digestibilities was found. Relatively low apparent chitin digestibilities in those two raptorial species suggest that chitin is not an important energy source for raptors. Further investigation is required to clarify the magnitude of potential benefits. J. Exp. Zool. 283:387–393, 1999. © 1999 Wiley-Liss, Inc.