Brustenga, L., D. Marini, F. M. Guarino & L. Lucentini

Davian behaviour and functional egg fertilization in the Italian Stream Frog Rana italica (Anura: Ranidae). pp. 297-301.

Abstract. Davian behaviour is a rare maladaptive trait in which a live animal, most commonly a male, attempts to mate with other deceased animals. There are reports of both intraspecific and interspecific Davian behaviour and the phenomenon is extensively reported in amphibians but was never reported before in the Italian stream frog (Rana italica). This work reports the finding of a deceased female sunk in a shallow stream that presented a breach in the trunk from which a cluster of eggs was protruding. Upon a closer inspection, viable embryos in early and late neurulation stages (Gosner stages 13 to 17) were observed confirming that a male fertilized the eggs after their passage in the oviduct. By analysing the embryonic stages and temperatures, fertilization was estimated to have occurred approximately 10 days before the observation. Nonetheless, this result cannot be directly compared to the animal's post-mortem interval due to the lack of precise estimation. While there is no evidence that the mating effort of a male externalized the egg mass, the occurrence of thanatophilia is supported by the fact that fertilization occurred shortly after the egg mass was expelled from the female’s body. This work adds R. italica to the other species of the genus Rana for which Davian behaviour was reported.

Key words. Thanatophilia, necrophiliac behaviour, Italy, Gosner stages, embryonic development.