Monitoring an endangered species in the Vallée des Baux

The magnificent butterfly, the Southern Festoon (Zerynthia polyxena) (Diane in French), and its inseparable host, the nicely named birthwort have been the subject of a study by A Rocha France.

Southern festoon (Zerynthia polyxena) Photo : Nathan Horrenberger

The Southern festoon is said to be interdependent with the birthwort: that is to say that its existence is directly linked to that of the birthwort. Indeed, this pretty butterfly only lays its eggs under the leaves of this elegant perennial, which the caterpillars will then feed on (and the Southern Festoon even seems to have a preference for Round-leaved birthwort, which is native to Southern Europe). This means that the meadows where the birthworts bloom are indispensable to the survival of the Southern festoon. No birthworts, no Southern festoon.

Round-leaved birthwort (Aristolochia rotunda) Photo: Chloé Cornic

The A Rocha France teams in the Vallée des Baux, under the direction of Timothée Schwartz, took an interest in this magnificent butterfly, which is threatened and protected at a national level, and studied its population in the Etroit marshes over two scientific monitoring seasons.

The results showed that even though the Southern festoons are present in this area, it seems essential to favour late mowing to encourage the growth of the birthwort, and thus the survival of this beautiful butterfly.

The complete report (in English) can be downloaded here.

Well done to the Vallée des Baux team for this substantial work!

Mowing ends on the site of the Etroit Marsh to leave room for the growth of the birthworts in a few weeks, hoping that there will be many Southern Festoons to lay their eggs there this year!