North American Recent Soft-Shelled Turtles (Family Trionychidae)Webb, Robert G. (Robert Gravem)
Science
North American Recent Soft-Shelled Turtles (Family Trionychidae)
Webb, Robert G. (Robert Gravem)
Soft-shelled turtles
Food from the digestive tracts of 11 specimens of _T. m. muticus_ from
the Kansas River at Lawrence, Douglas County, Kansas, were examined
(Table 6). The turtles (KU 55296-306, eight adult males and three
immature females, ranging in plastral length from 9.0 to 12.5 cm.)
were collected in June, 1958, by Mr. Robert R. Patterson. All turtles
were caught on hook and line in a period of about four or five hours
at dusk. Patterson frequently fished below the bridge at Lawrence and
observed that heads of softshells were often seen there about dusk and
that the turtles seemed to prefer a rather shallow, quiet-water area
of swirls and eddies for feeding. The stomachs, and to a lesser
degree, the intestines, were nearly full. Some turtles contained plant
fragments, principally elm seeds. The kinds of food in this sample
were also identified by Dr. Byers and were mostly insects, the most
frequent item being trichopterans; many of the insects eaten
undoubtedly fell into the water. The remains of spiders were found in
four stomachs and crawfish fragments in five.
Stomachs of two adults of _muticus_ from Lake Texoma, Oklahoma, were
opened. The stomach of one (OU 27593) was full of naiads of the
burrowing mayfly _Hexagenia_; that of the other female (OU 27594)
contained exoskeletal remains of crawfish. The two specimens were
drowned in gill nets between the hours of 11 a. m. and 7 p. m., on
July 10, 1954; the intact condition of the mayfly naiads indicated
recent feeding.
The species of American softshells are mainly carnivorous. The presence
of vegetable matter (mentioned in previous paragraphs) in the digestive
tracts of many specimens and True's statement (1893:152) that
soft-shelled turtles include a variety of vegetable matter in their food
indicates omnivorous habits. Duellman and Schwartz (1958:272) stated
that _ferox_ is omnivorous and Carr (1952:430) made a similar statement
for _spinifer_. The diet seems to be determined by the food supply
available, which may vary seasonally or with adverse conditions such as
flooding; under normal environmental conditions, however, vegetable
matter probably is ingested incidentally to other food. There is no
indication of a preference in food habits according to species and
subspecies. Most of the food seems to be obtained by active foraging
that is triggered primarily by movement of the prey; the sense of smell
is probably secondary.
Reproduction
_Size of males at Sexual Maturity_
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