The Hermit moth is a species in sharp decline in France, where it has disappeared from 54 departments since the 1980s. Having identified it on the Domaine des Courmettes, our scientific teams have launched a pilot study to determine and estimate the actual size of the population on the site.
The Hermit: an endangered species that is still poorly understood
Although classified as “Endangered” on the PACA regional red list and “Vulnerable” at the national level, the Hermit is not a protected species in France. The main cause put forward to explain its decline is the abandonment of extensive grazing. The species depends on short vegetation to lay its eggs, and grazing helps to maintain this short vegetation. Several other causes are currently being studied, such as the presence of chemical pollutants in the plants consumed by the caterpillars. The Hermit is one of the target species of the National Action Plan (PNA) for butterflies.
Despite the challenges, few studies have been conducted on the Hermit, and several questions remain. What are the host plants used by the species at the local level? What is the dispersal capacity of this butterfly? How should sites favorable to the species be managed? How should the factors contributing to its decline be prioritized?
A pilot study at Les Courmettes
The Domaine des Courmettes provides habitats that are favorable to the species (dry grasslands and stony ground), and individuals of the species are regularly observed on the site. Given the lack of knowledge about the species’ ecology, our teams decided to launch a study with two objectives:
– To determine and estimate the actual size of the population on the site.
– Based on the data and time available, to estimate the average lifespan of the butterflies and identify the host plants used by the Hermit caterpillar.
This study is part of the PACA regional version of the PNA (National Action Plan).
Initial results
In 2021, we observed around 20 different individuals, the majority of which were males (62%). The mapping of observations does not show any difference in distribution between males and females. Furthermore, while females were observed equally throughout the five weeks of the study, 70% of males were observed before August 15, suggesting greater activity at the beginning of the flight period or earlier metamorphosis for males.
The protocol itself requires some adjustments, such as changing the times of day when observations are made. The majority of observations were made during sessions with the least favorable conditions (heavy cloud cover and/or wind). The protocol should therefore be followed outside the hottest hours of the day, early in the morning and at the end of the day. It is also necessary to increase the number of individuals captured in order to carry out the analyses required to meet the study’s objectives.
We plan to continue the study during the summer of 2022 and discussions are underway with other partners to prepare an interregional study on the species in 2023.
The full study report is available here.
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