The Hermit: protecting a vulnerable butterfly

The Hermit (Chazara briseis) is a butterfly that is in sharp decline in France, where it has disappeared from 54 departments since the 1980s. Identified on the Domaine des Courmettes, our scientific teams have started a pilot study to discover and estimate the real size of the population on the site.

[envira-gallery id=”6412″]

The Hermit: an endangered species that is still poorly known

Although classified as “Endangered” on the PACA regional red list and “Vulnerable” on 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 allows this short vegetation to be maintained. Several other causes are being investigated, such as the presence of chemical pollutants in the plants eaten by the caterpillars. The Hermit is one of the target species of the National Action Plan for butterflies.

Despite the challenges, few studies on the Hermit have been conducted and several questions remain: what host plants does the species use locally? What is the dispersal capacity of this butterfly? What are the management methods for sites favourable to the species? How can we rank the factors of decline?

A pilot study at Les Courmettes

The Courmettes estate has habitats that are favourable to the species (dry grassland and stony ground) and individuals of the species are regularly observed on the site. Given the lack of knowledge about the ecology of the species, our teams decided to launch a study with two objectives:

• To discover and estimate the real size of the population on the site
• Based on the data and the time available, to estimate the average life span of the butterflies and to identify the host plants used by the Hermit caterpillar

This study is part of the PACA regional version of the National Action Plan.

First results

In 2021 we observed at least twenty different individuals, mostly males (62%). The mapping of the observations of individuals does not show any difference in distribution between males and females. Furthermore, although the females were observed equally throughout the five weeks of the study, 70% of the males were observed before 15 August, which suggests greater activity at the beginning of the flight period or earlier metamorphosis for them.

The protocol itself requires some adaptations, such as modifying the time of day: the majority of observations were made during sessions with the least favourable conditions (heavy cloud cover and/or wind) suggesting that the protocol should be carried out outside the hottest hours, early in the morning and at the end of the day. It will also be necessary to increase the number of individuals captured in order to carry out the analyses required to meet the objectives of the study.

We plan to continue the study in the summer of 2022 and discussions with other partners are underway to set up an inter-regional study on the species in 2023.

You can read the complete report (in French) here.