24.08.2021

The six most important things to know about butterfly habitats

The butterflies are in decline worldwide. In Denmark alone, every fourth butterfly is endangered. This is a result of the lack of habitats and pronounced use of pesticides and fertilizers following the intense agricultural use in the open landscape. However, cities have great potential to become oases of biodiversity, as it is easier to assign space and create suitable habitats for biodiversity in urban environments. This article introduces the six most important landscape and design parameters that must be considered if the butterfly is to be attracted as a permanent resident or frequent visitor.

The design should target the butterfly —
In Denmark, for example, 73 butterfly species are considered to be native. In order to create optimal conditions for the butterflies, it is important to understand their life cycle and habitat requirements.

Butterflies go through 4 life stages; egg, larva, pupa and imago (adult). The larva has a one-sided diet and is, most often, associated with a specific host plant. The adult butterfly lays its eggs on the host plant, where the larva begins to eat the moment it hatches. Therefore, it is crucial for the larva to have access to a suitable quantity of the host plant so that it does not run out of food. The adult butterfly feeds on nectar and therefore needs nearness to flowers that produce large amounts of nectar.

The habitat requirements are important for the butterfly. The biotope, that you create, is the basis for which butterfly species are attracted. Some species prefer open landscapes (meadow, heath, beach, grassland), others different forest habitats (forest clearing, coppice forest, beech forest) and some prefer a mix of the two. (Eskildsen, 2015).

Some butterfly species prefer very specific host plants or specific habitats – the so-called ‘specialists’. On top of that, they often have low mobility, meaning that they fly within a small radius all their lives and thus easily come into trouble if their ecosystem is disturbed. Most of the endangered and vulnerable species are in these groups.

Another group of butterflies can live in many habitats and has many hostplants – this is the so-called ‘generalists’. At the same time, some are able to fly long distances.

The Silver-washed fritillary / Kejserkåbe / Argynnis paphia The Silver-washed fritillary is a species in decline in Denmark and what you would refer to as 'a specialist'. It lives in open forests and has violets as host plants: Heath dog-violet, common dog-violet, pale wood violet, and English violet.
The Small Copper / Lille Ildfugl / Lycaena phlaeas The small copper is a 'generalist' and is commonly seen everywhere in Denmark on grassland. This one is shot at 'DTU Campus' in Lyngby where SLA's biologists have made a 'biodiversity baseline' for the 100 ha campus in connection with recommendations for a biodiversity strategy.

Here is a list of the six most important habitat requirements, presented as design parameters:

— 1. Many flowering plants: The adult butterflies feed on nectar from flowers. Make sure to have many different nectar-containing flowers with different flowering times

— 2. A good microclimate: Shelter for the wind, exposure to the sun and warmth are essential conditions.

— 3. The right soil conditions: The nutrient content of the soil must be low, otherwise the grass will grow tall and outcompete the flowers.

— 4. Create many edge environments: Butterflies have adapted to ‘a life on the edge’. This can be: The edge between forest and field, high and low, dry and moist, the edge of the field lane, etc.

— 5. Plant host plants: Larvae are picky. Most often, the larvae feed on only one or two host plants. Plant a rich occurrence of the individual butterflies’ host plants, so there are good opportunities for laying eggs.

— 6. An appropriate grass height: The microclimate between the grasses must not be too shady and humid for the larvae. It must therefore be kept at a height that takes this into account. Also, you need to consider the life cycle of the specific butterfly. If you are doing nature design for an urban environment, the grass height can be regulated through the maintenance plans. If you have animals grazing on the site, the ‘grazing pressure’ has to be appropriate.

The design parameters can be used as a basis to attract all sorts of butterflies and provide a good rule of thumb if you generally want to create attractive and rich natural spaces with high biodiversity – both in urban and in natural landscapes.

However, there are many butterfly species, so before the actual design phase begins, you should consider which species you want to attract. In this way, the biotope, the habitat design, and the vegetation can be targeted the butterflies.

 

Not all butterflies are city creatures – but a lot can be

As a rule of thumb, it can be said: Since the ‘specialists’ need stable ecosystems, the natural landscapes and large areas laid out for nature will be the best suited habitats for them.

If it is desired to create butterfly habitats in urban contexts, or in smaller areas where changes can occur, it is more suitable to go for the species belonging to the so-called ‘generalist’ group.

“Butterflies are considered to be a sort of ‘nature thermometer’ that can give us an indication about the general state of health of our nature.”

— Anne Eskildsen, Ph.D. and butterfly expert
The common blue butterfly / Polyommatus icarus / Almindelig blåfugl This generalist butterfly lives on many different types of warm dry habitats with many flowers, including wild gardens. It can be seen almost everywhere in the landscape though, since especially the males fly far from the natural habitat.
The Glanville Fritillary / Okkergul pletvinge / Melitaea cinxia The Glanville Fritillary is a species in decline, very vulnerable to negative impacts from agriculture such as fertilizer and mowing. The preferred host plants are different types of plantago. The butterfly is normally found on dry pastures, heaths, and old dunes – and it prefers flower-rich localities where it can often occur in numbers.

Literature:

Anne Eskildsen (2015): Ecological specialization matters: long term trends in butterfly species richness and assemblage composition depend on multiple functional traits

Miljøministeriet (2008): Hedepletvinge – Et LIFE-Nature projekt

Christina Troelsen (2018): Danske sommerfugle er i stærk tilbagegang • Anne Eskildsen (2015): Ecological specialization matters: long term trends in butterfly species richness and assemblage composition depend on multiple functional traits

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