Thiruvananthapuram’s urban green patches act as refuges for forest butterflies

Urban green spaces in Thiruvananthapuram support a surprisingly rich diversity of butterflies, including protected and forest-dependent species, according to a new scientific study published in the peer-reviewed journal Urban Ecosystems.

It also found that around half of the Kerala’s known fruit-feeding butterfly species are present within the city limits.

The collaborative research by Dutch biologist Freerk Molleman, who presently works at the Department of Systematic Zoology, Adam Mickiewicz University, Poland, and Berke Can Aydin, Department of Molecular Biology and Genetics, Afyon Kocatepe University, Turkey, focused on fruit-feeding butterflies, a group that is considered sensitive indicators of habitat quality.

Using fruit-baited traps, the team sampled butterflies across four urban sites in Thiruvananthapuram and a natural forest in Vithura.

Nymphalidae family

The researchers recorded 3,625 butterflies belonging to 29 species, all from the Nymphalidae family of butterflies. Open habitats within the city, such as abandoned paddy fields with coconut farming and grazing land, supported up to 17 species, while closed-canopy urban habitats like agroforestry plots and semi-natural forest patches recorded even higher diversity. A natural forest site near Vithura, on the fringes of the Western Ghats, showed the highest species richness.

According to Dr. Molleman, a former postdoctoral fellow at Indian Institute of Science Education and Research (IISER) Thiruvananthapuram, the study also documented the presence of the Gaudy Baron, a butterfly protected under Schedule IV of the Wildlife (Protection) Act, 1972, in urban open habitats.

Charismatic forest species such as the Clipper butterfly were also found in small wooded valleys inside the city, providing an indicator that fragments of near-natural vegetation can act as refuges even within dense urban landscapes.

Seasonal patterns

However, the study also found that species composition varied significantly between open and closed habitats and changed markedly over time, largely influenced by seasonal patterns such as the monsoon. Butterfly abundance peaked shortly after the onset of monsoon rains. The role of fresh plant growth in supporting insect populations was reflected in the study.

The researchers observed that Thiruvananthapuram’s landscape, characterised by a gradual transition from protected forests to mixed agroforestry and residential areas, may help explain why many forest-associated species persist in the city. Cultivated trees such as coconut, mango and banana, along with semi-natural vegetation on rocky outcrops and wetlands, provide host plants and food sources for several species.

The study comes amid concerns over rapid urban expansion in the region. Urban land in Thiruvananthapuram district has more than doubled over the past two decades, leading to a corresponding decline in farmland and natural habitats.