International Giant Otter Studbook Husbandry and Management

Section 19
Diet and Feeding
Only good quality, mostly fresh water, fish low in thiaminase and fat should be offered as
the main diet (Wünnemann 1995). Most salt-water fish contains too much fat that can
cause health problems if it is fed as the main diet. Saltwater fish should only be offered
occasionally (see below). Offering a variety of highest quality fish is advisable to maintain
good health and a balanced diet, accommodate eating preferences, avoid fixed
dependencies on a particular fish type and add enrichment (Crissey 1998).
The following is excerpted from Wünnemann (1995 b ). “Giant otters are the only real 'fisheaters'
among the otters. All studies in the wild say that the main part of their diet is fish....The
broader the spectrum of items, the better. The fish has to be first quality, freshwater fish.
Saltwater fish is taken, but contains too much fat. The amount of food they need is enormous; 3
to 4 kg of food per day per animal, at best given at three to five different times. The ingestion is
very rapid and the remains of the food can be found after two or three hours at the defaecation
point.” Also Hagenbeck & Wünnemann (1992) explain, “Marine fish, such as herring (Clupea
harengus) and mackerel (Scomber scombrus) are preferred by the otters but are not given as we
consider them too oily to offer a good balanced diet.” “Marine products contain high levels of
poly- and mono-unsaturated fatty acids.” (Reed-Smith 2001).
Six out of 16 institutions surveyed fed live fish for enrichment, freshwater rainbow trout (Salmo
gairdneri) or Tilapia. Caution should be taken as feeding live, freshly caught and/or poor
quality fish could cause diseases, malnutrition or/and transmit parasites. Feeding fish in the
reproductive state (i.e. when they carried eggs) has caused diarrhea and loss of appetite, so fish
eggs should be removed before fish is fed (Lazzarini, pers. comm.; Gatz & Sykes-Gatz pers.
comm.)
Giant otters should be fed 3-5 times per day (usually 2 - 3 kg [4.4 - 6.6 lbs.] fish/day/adult)
to accommodate fast metabolisms with rapid digestion, prevent accumulation of uneaten
fish left-overs and provide enrichment. Amounts eaten can vary with air temperature and
activity level changes, but if food is refused for one day this could be a sign of sickness.
Excess weight gain or loss and daily amounts and food types eaten should be monitored and
recorded.
Fish should be fed in amounts that otters can finish, so that excess uneaten fish is not left
in enclosures during the day and overnight. Uneaten fish can attract rats and rats could
transmit leptospirosis to the otters. A couple giant otters have contracted leptospirosis and this
is suspected to have occurred because large amounts of uneaten fish were left daily in
enclosures overnight/during the day (see Chapter 1 Section 4). When fish remains exist, they
should be removed from all water and land areas daily. Otters will eat their fish in the water or
take their fish into the water, as well as eat fish on land. Caution must be taken, as illness may
also occur if otters (esp. cubs) eat spoiled fish remains or are exposed to harmful bacteria ridden
swim water (other than exposure to leptospirosis, neither of these events have been reported to
occur). Note: it is not uncommon that otters will pick up small pieces of left over fish
within their pools and land area and eat them; this although has not been reported to
cause problems. It is nearly impossible, even with filtration systems, to remove all small
fish pieces from the water. If a significant amount of left-over uneaten fish, that has been
sitting in the enclosure for a while, is regularly consumed, vitamin deficiencies may occur.
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