Grazing horses benefit butterflies in Czech conservation initiative

Exmoor ponies in the Milovice Nature Reserve. Photo: Atillak, CC BY-SA 4.0 via Wikimedia Commons
Exmoor ponies in the Milovice Nature Reserve. Photo: Atillak, CC BY-SA 4.0 via Wikimedia Commons

A former butterfly hotspot in the Czech Republic has been rejuvenated by the return of grazing horses, European bison, and free-living cattle akin to the extinct auroch, researchers have found.

The success of the programme at the former Milovice military training range has been described in a paper published in the journal BMC Ecology and Evolution.

Martin Konvička and his fellow researchers said rewilding by large ungulates represents a cost-efficient approach to managing natural environments. It may be particularly useful for areas where biodiversity depends on disturbance dynamics, and is put at risk by successional changes in the vegetation, they said.

In their study, they focused on butterflies inhabiting the former military range, where a combination of Exmoor ponies, Tauros cattle and European wisent (bison) have been introduced since 2015. Tauros cattle are part of a European “back-breeding” initiative to create a modern-day equivalent of the extinct European auroch — a keystone cattle species hunted to extinction in 1627.

The study team analysed butterfly presence/absence patterns immediately after the end of military use in the early 1990s, and in 2009, before the reintroduction of the first animals. Further surveys were carried out from 2016 to 2019, after the animals’ introduction.

The researchers found that, after military use, several poorly mobile species inclined towards oceanic climates were lost, while the area gained mobile species preferring warmer continental conditions.

Following the introduction of the animals to grazing reserves within the former military range, the researchers monitored a series of plots both within and beyond the reserves.

Back-bred "aurochs" graze in the Milovice Nature Reserve. Photo: Atillak, CC BY-SA 4.0 via Wikimedia Commons
Back-bred “aurochs” graze in the Milovice Nature Reserve. Photo: Atillak, CC BY-SA 4.0 via Wikimedia Commons

They found that the plots grazed by the animals hosted higher butterfly species richness and abundance. They reported that larger-bodied butterflies developing on coarse grasses and shrubs were inclined towards the ungrazed plots, whereas plots within the grazed reserves supported smaller species developing on small forbs.

The study team said the butterfly richness seen within the former training range is arguably due to the exclusion of intensive agriculture and forestry, combined with the past disturbance-succession dynamics typical for military areas.

They said the presence of the cattle, horses, and wisents presumably increased per-plot butterfly species richness and abundance by manipulating vegetation conditions, thus supporting multiple species of conservation concern, including the critically endangered obligatorily myrmecophilous Phengaris alcon.

They said the changes seen after military use, which resulted in the successional overgrowth of the disturbed sparsely vegetated surfaces, leading to the gradual dominance of coarse grasses and tall forbs, probably led to shrinking habitats for poorly mobile butterflies.

While the introduction of the animals boosted species richness and abundance, it did favour smaller species developing on small forbs over larger species developing on large forbs, grasses or shrubs, they noted.

The authors concluded that the changes in species composition following military use were attributable in part to successional changes in the vegetation. By blocking this, large ungulates support butterflies depending on competitively poor plants, they said.

“Restoring large ungulate populations represents a great hope for conserving specialised insects, provided that settings of the projects, and locally adapted ungulate densities, do not deplete resources for species with often contrasting requirements.”

The study team comprised Konvička, David Ričl, Veronika Vodičková, Jiří Beneš and Miloslav Jirků, with a range of Czech institutions.

Konvička, M., Ričl, D., Vodičková, V. et al. Restoring a butterfly hot spot by large ungulates refaunation: the case of the Milovice military training range, Czech Republic. BMC Ecol Evo 21, 73 (2021).

The study, published under a Creative Commons License, can be read here

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