Diet and body condition of cave‐dwelling dwarf crocodiles (Osteolaemus tetraspis, Cope 1861) in Gabon

• Published in: African journal of ecology 2017-12, Vol.55 (4), p.411-422
• Main Authors: Shirley, Matthew H., Burtner, Brittany, Oslisly, Richard, Sebag, David, Testa, Olivier
• Format: Article
• Language: English
• Subjects: Animal populations; Aquatic reptiles; Bats; Biocompatibility; cavernicole adaptation; Caves; Conspecifics; Crickets; Crocodiles; Crocodylia; Crustaceans; Ecological monitoring; facultative cave use; Foraging habitats; Forests; Freshwater crustaceans; Fulton's K; Habitat utilization; Habitats; Insects; Juveniles; Osteolaemus tetraspis; Prey; Sciences of the Universe; Statistical analysis
• ISSN: 0141-6707; 1365-2028
• DOI: 10.1111/aje.12365

We present the first ever observations of dwarf crocodiles (Osteolaemus tetraspis) selectively utilizing a cave ecosystem. We analysed crocodile diet to preliminarily assess the degree of ecological isolation of cave‐dwelling crocodiles from their forest‐dwelling conspecifics despite their physical proximity. We additionally conducted the first study of body condition of dwarf crocodiles and compared cave‐dwelling individuals to surface‐dwelling individuals from a variety of alternative habitats and sites as a means to better understand the implications of a semihypogean life on this species. Crocodiles captured in the caves appeared to forage exclusively in the caves and ate mostly cave crickets and bats, whereas crocodiles captured in the surrounding forest habitat consumed primarily freshwater crustaceans and insects and were not found to consume cave‐dwelling prey. Juvenile cave crocodiles had significantly higher body condition compared to juvenile forest crocodiles, which did not vary amongst forest locations. The difference in body condition between adult cave and forest crocodiles was not statistically significant despite also being higher; we suspect this is an artefact of the low sample size rather than a real nondifference. Forest adult crocodiles generally had significantly higher body condition than juveniles, but did not vary by site or habitat. This lack of variation suggests that habitat type is not the most important factor influencing dwarf crocodile body condition. Our results provide a unique insight into facultative cave use by a principally surface‐dwelling species and reinforce the necessity for further research into this unique system to better understand the evolutionary‐scale implications of cave habitat use by dwarf crocodiles. Résumé Nous présentons ici la première observation de crocodile nain (Osteolaemus tetraspis) dans un écosystème cavernicole. Nous avons analysé leur régime alimentaire pour évaluer le degré d'isolement écologique par rapport à leurs conspécifiques forestiers indépendamment de leur proximité physique. Nous avons également effectué la première étude sur les conditions physiques des crocodiles nains et nous avons ensuite comparé les individus troglodytes par rapport à ceux de l'extérieur dans une variété d'habitats et de sites afin d'explorer les conséquences d'une vie semi‐hypogée sur cette espèce. Les crocodiles capturés dans les grottes semblent trouver leur nourriture exclusivement dans les cavités, la pl