The feeding ecology of yearling, juvenile and sub-adult Nile crocodiles, Crocodylus niloticus, in the Okavango Delta, Botswana

[摘要] The stomachs of 286 crocodiles (17 cm to 166 cm snout to vent length) werelavaged over a two year period. Crocodylus niloticus has a similar ontogenetic shiftin diet to that of other crocodilians. Yearlings predated primarily on aquatic insectaand arachnida, as crocodile size increased (juveniles) the diet became more diverseincluding crustacea, amphibia and fish. The largest size class (sub-adults)consumed primarily fish. Yearlings fed consistently throughout the year, however ahigher proportion of empty stomachs occurred within the juvenile and sub-adultsize classes during the winter months. A captive experiment with wild caughtcrocodiles (0.7 kg - 20 kg) indicated a decrease in satiation rate (maximum mass offood eaten as a percentage of crocodile body mass) from 11.3 % to 6.5 % with anincrease in crocodile size. Wild yearlings consumed 0.48 % of their body mass inprey per day, and juveniles, 0.23 %. The wild food conversion rates of natural preywere low, 32 % and 40 % for yearlings and juveniles respectively. This waspossibly due to a high percentage of indigestible (chitinous) invertebrate mass inthe diet. The percentage of stomach stone mass to crocodile body mass increasedwith crocodile size. Seven species of nematodes were found within the stomachs,four of which represent new geographic records.

[发布机构] Stellenbosch University