Opportunistic carnivory by Florida manatees (<I>Trichechus manatus latirostris</I>)

Abstract

The Florida manatee (Trichechus manatus latirostris)i so ne of the most endangered marine mammals in the US To protect this species, it is important to understand the feeding ecology to define critical habitats. Manatees generally are considered to be strictly herbivious mammals that only incidentally consume animal species. This concept is based on the preponderence of freshwater vegetation, seagrasses, and algae that is found in most stomach content and fecal analyses. In the present study, manatees were observed feeding in areas of the Indian River Lagoon in Vero Beach and Fort Pierce, Florida, USA during June to August 2001. Most manatees were observed to be feeding on seagrasses and algae; however, on two occasions, manatees were observed apparently preferentially consuming invertebrates that were attached to ad ock. Although some fibrous algae were present on the dock structure, the majority of biomass present was made up of invertebrates. Manatees were heard crunching invertebrate shells and seen pulling animals, such as tunicates, into their mouths. These observations suggest that manatees actively, rather than incidentally, consume invertebrates in some cases.

An isotopic assessment of the feeding habits of free-ranging manatees

“…Incidental ingestion of insect larvae, amphipods, mollusks, shrimps, and other macroinvertebrates that live in vegetation has also been reported (e.g. Hartman 1971), although in some cases these may be intentionally ingested (Courbis & Worthy 2003), and it has been hypothesized that these organisms could contribute substantially to the manatee's protein consumption (Hartman 1979). …”

Florida manatees Trichechus manatus latirostris actively consume the sponge Chondrilla caribensis

“…Florida manatees (Trichechus manatus latirostris) are generally considered to be strictly herbivorous mammals (e.g., seagrasses, algae, seeds, acorns; O 'Shea, 1986;Guterres-Pazin, Rosas & Marmontel, 2012), only incidentally consuming invertebrates or fish (Powell, 1978). However, in spite of the fact that stomach and fecal analyses find mostly seagrasses and algae, there have been a few instances where manatees have been observed to eat invertebrates (e.g., Courbis & Worthy, 2003). Barnacles, tunicates, bivalves, gastropods, crustaceans, polychaetes, other small invertebrates and fish have been ingested by manatees and dugongs (Powell, 1978;Reeves, Tuboku-Metzger & Kapindi, 1988;Anderson, 1989;O'Shea et al, 1991;Preen, 1995;Courbis & Worthy, 2003;Guterres-Pazin, Rosas & Marmontel, 2012;Vélez-Juarbe, 2014).…”

“…However, in spite of the fact that stomach and fecal analyses find mostly seagrasses and algae, there have been a few instances where manatees have been observed to eat invertebrates (e.g., Courbis & Worthy, 2003). Barnacles, tunicates, bivalves, gastropods, crustaceans, polychaetes, other small invertebrates and fish have been ingested by manatees and dugongs (Powell, 1978;Reeves, Tuboku-Metzger & Kapindi, 1988;Anderson, 1989;O'Shea et al, 1991;Preen, 1995;Courbis & Worthy, 2003;Guterres-Pazin, Rosas & Marmontel, 2012;Vélez-Juarbe, 2014). Spicules of sponges seen in necropsy samples obtained from manatee carcasses are generally considered incidentally ingested with seagrasses and algae (e.g., Allen et al, 2017).…”

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

“…Coastally, seagrasses are a dietary staple (e.g., Campbell and Irvine 1977;Hartman 1979;Ledder 1986;Provancha and Hall 1991;Koelsch 1997;Lefebvre et al 2000), with manatees apparently preferring manatee grass (Syringodium filiforme) over turtle grass (Thalassia testudinum) in mixed-species stands (Hartman 1979;Provancha and Hall 1991). To a lesser extent manatees may also eat macroalgae (e.g., Gracillaria tikvahiae), invertebrates, terrestrial grasses growing close enough to the shore to reach, acorns that have fallen into the water, and fish caught in gill nets (e.g., Powell 1978;Hartman 1979;Reeves et al 1992;Courbis and Worthy 2003). Ex situ manatees are fed a diet consisting predominately of romaine lettuce (Lactuca sativa), which differs significantly from their in situ diet in both nutritional value and composition (Siegall-Willott et al 2010).…”