Digestive Efficiencies of Ex Situ and In Situ West Indian Manatees (Trichechus manatus latirostris)

AbstractDigestive efficiencies (Dm) of ex situ and in situ manatees (Trichechus manatus latirostris) were, for the first time, assessed using manganese (Mn2+) as a naturally occurring marker. The Dm of ex situ manatees determined using [Mn2+] did not differ significantly from the Dm assessed using lignin, supporting the efficacy of the manganese approach. Gastrointestinal tract samples, obtained from recently dead animals, showed [Mn2+] concentrations were lowest in the stomach and remained low in the duodenum and small intestine but increased in the cecum, colon, and rectum, consistent with colonic digestion and absorption. In situ manatees consuming marine vegetation had significantly lower Dm (mean ± SE, ; ) than did in situ manatees consuming freshwater vegetation (; ), which in turn had significantly lower values than did ex situ manatees consuming lettuce (; ). In situ manatees eating seagrasses had significantly higher Dm than did long-term ex situ animals consuming seagrass for short periods of ti...