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Abstract:
We used stable isotope analyses to characterise the feeding dynamics of a population of red swamp crayfish in Lake
Naivasha, Kenya, after the crash of submerged macrophytes and associated macroinvertebrates, and during a natural drawdown
of the lake water level. We expected a heavy reliance upon a diet of detrital matter to sustain the population as a
consequence, and indeed, for the majority of the crayfish population caught from the lake, we saw a concomitant shift in
isotopic values reflecting a dietary change. However, we also caught individual crayfish that had occupied the footprints of
hippopotamus and effectively extended their range beyond the lake up to 40 m into the riparian zone. Isotopic analysis
confirmed limited nocturnal observations that these individuals were consuming living terrestrial plants in the vicinity of the
footprints. These are the first empirical data to demonstrate direct use of terrestrial resources by an aquatic crayfish species
and further highlight the traits that make red swamp crayfish such opportunistic and successful invaders.
