Chazara briseis: Decline and Conservation

Bartoňová, Alena Sucháčková, Konvička, Martin, Marešová, Jana, Bláhová, Dana, Číp, David, Skala, Pavel, Andres, Miloš, Hula, Vladimír, Dolek, Matthias, Geyer, Adi, Böck, Oliver, Kadlec, Tomáš & Fric, Zdeněk Faltýnek, 2021, Extremely Endangered Butterflies of Scattered Central European Dry Grasslands Under Current Habitat Alteration, Insect Systematics and Diversity (AIFB) 5 (5), pp. 1-18 : 7-8

Chazara briseis: Decline and Conservation

Decline was rapid all across Central Europe.By 2020, there were three population systems in AT (Lower Austria, two at military training areas (MTA), one in a nature reserve); a single metapopulation occupying 8 steppe patches and covering two grid cells (area of 10′ latitude and 6′ longitude) in CZ (contrary to 106 cells in 1951–2000) ( Benes et al. 2002, Kadlec et al. 2010); and about 21 cells in DE (as opposed to 40 after 2000, when it occupied only 13.5% of all DE historical records ( Reinhardt et al. 2020) ( Fig. 1 ).

In DE after 2014, the observations came mainly from the metapopulation systems in the Rhön Mts (Thuringia), Kyffhäuser

(Thuringia), Unstrut Valley (Saxony-Anhalt), Ostalb (BadenWürttemberg), and a few scattered populations in Bavaria. The decline is well documented in some areas. In Bavaria, 33 sites were inventoried in 2007–2008 and positive records were obtained from seven of them, in very low densities ( Dolek et al. 2007, 2008). The largest remaining population in Bavaria inhabits a former MTA near Heidenheim (Weissenburg-Gunzenhausein), and there are further four isolated sites with small colonies. A monitoring program has been covering the four sites since 2012. At this site, goat grazing is now practiced on a three-cell rotation ( Geyer and Böck 2018). In contrast to sheep herding, this grazing method maintains a short turf with exposed bedrock and does not impact larval mortality, owing to the nocturnality of the 3rd instar larvae ( Königsdorfer 1997). Transect counts fluctuate between the years around 120 adults ( Geyer 2020). A population on the foreland of the Südliche Frankenalb (Southern Franconian Jura), first observed in 2008 ( Böck and Dolek 2008), is still on the verge of extinction so that managers use a ‘Robocut’ (a remote-controlled mulching vehicle with chain drive) to expose bedrock on selected slopes. The latest monitoring data show that in these newly established areas a few egg depositions have now taken place ( Geyer 2020). The remaining three sites in the Südliche Frankenalb are pastures grazed three times per year, one inhabiting also a disused quarry. In Baden-Württemberg (Ostalb), two metapopulation systems with originally 12 sites each have been managed for the benefit of the species since 1991. Scrub removal, adapted grazing, and recently small-scale soil disturbances are practiced there. As a result, both metapopulations persist with transect count numbers ≈ 60 adults in their core parts; nevertheless, this is much less than in the 1990s.

A mark-recapture program in the last CZ metapopulation in České středohoří (Central Bohemian Uplands) estimated ≈2000 individuals inhabiting ten, then mostly unmanaged, steppe patches in 2006 ( Kadlec et al. 2010). Subsequent monitoring documented a steep decline, combated by the re-establishment of sheep grazing in spring and summer. This initially reduced forbs but not the coarse steppe grasses ( Stipa spp. ), which suppress the short Festuca patches utilized by the larvae ( Kadlec et al. 2009, Vrba et al. 2021). Since 2017, the grazing has been supplemented by manual mowing of the Stipa patches, litter removal, and patchy raking of the ground ( John et al. 2018).

Identical management is currently practiced at slopes of the Hainburger Mts, AT, and the increase of individuals has been visually recorded. The remaining two AT sites are MTAs, and more intensive management is needed there. In the Bakony Mts, HU, a strong population system exists owing to traditional pastoralism.

With the aim to restore the CZ metapopulation, ex situ breeding started in 2014 with two males and two females from České středohoří, CZ, in a roofed semi-open facility. They oviposited on potted Festuca ovina L. protected against predators and parasitoids. Grown-up larvae were transferred to 60 × 40 × 30 cm containers for pupation, eclosion, mating, and oviposition. Adults were handfed daily with a sucrose solution. The initial fertility per female was ≈ 400 eggs, but combined losses at eclosion, moltings, and pupation were ≈60%. Suspecting a genetic influence (inbreeding), we added two wild-caught individuals to the ex situ population annually since 2017. After that, the mortality dropped considerably. Since 2016, surplus eggs (≈ 17,000 in total), larvae (≈1,500), and adults (≈500) were annually transferred back to pre-managed peripheral patches near their original site, restoring two additional colonies. Further releases took place in Český kras (Bohemian Karst), a historically occupied region about 60 km to the SE: Zlatý kůň (2,000 eggs in 2017, failed to establish), Třesina (590 postwinter larvae in 2020, resulting in an adult population of ≈50–60 individuals), and Radotín (350 postwinter larvae in April 2020, adult count ≈20–30).

We also bred individuals from Hainburger Mts , AT (3 males and 2 females), obtained in 2016, under identical conditions. The fecundity per female was ≈450– 500 eggs, with developmental failures. The obtained stock (2017: 40 larvae, 124 adults; 2018: ≈ 300 larvae) was released to the Mohelenská hadcová step reserve ( CZ), a site historically connected with the AT localities and prepared by targeted management, but the attempts failed .

Figures

Fig. 1. Localities of the study species in Central Europe (AT, CZ, four federal states of DE, HU, SK), distinguishing recently occupied (color), recently (i.e., post- 2010) extinct (white), recently not inventoried (light gray), and (re)introduced (including failed attempts, dark gray) populations of C. briseis (circles), P. damon (triangles), and P.dorylas (stars). See text for comments on their much denser distribution in the region just a few decades ago. Species P.damon and P.dorylas are present also in the Austrian Alps (not displayed on the map), and a few more (sub)recent populations of the two species are expected in lowland eastern AT.