Data for "Fragments of open- and closed-canopy habitat host significant fruit-feeding butterfly diversity in a large city in Southern India"

Summary: To gauge the diversity, community composition, and temporal variation of butterflies in urban habitats, we sampled fruit-feeding butterflies in a large city in southern India. We performed longer-term sampling in two sites with mainly open habitats (fragments of rural landscape), and more modest sampling in two closed-canopy urban sites (semi-natural and agroforestry) and a nearby natural forest. We caught 3625 butterflies belonging to 29 species, of which seventeen species were recorded in the open habitats, and a further five species in the closed-canopy sites in the city. The natural site had the highest number of species. Also taking into account published data on another natural site in the wider region, about half of the region’s fruit-feeding butterfly fauna was recorded from the urban sites. The community composition differed significantly between the open- and closed-canopy sites. Notably, the open habitats in the city featured a protected species, and closed-canopy sites harboured charismatic forest species. There was extensive temporal variation in butterfly community composition that was partly seasonal. Methods: We sampled fruit-feeding butterflies in and near Thiruvananthapuram (Kerala State, southern India), a city with a metropolitan population estimated to be about 1.68 million as of March 2025. We trapped butterflies in four urban sites in Thiruvananthapuram (Pongumoodu, Technpark, Church Forest, and Mookkunimala) and one natural site near Vithura. We sampled the Pongumoodu site (open habitat; 8°32’06.5”N, 76°54’53.9”E) for the longest period. The site is along a small stream and is mainly comprised of abandoned paddy fields, which now feature extensive coconut farming and grazing by cows and goats. There are also some gardens with bananas, papaya, mango, and cashew. The Technopark site (open habitat; 8°32’52.4”N, 76°53’23.3”E), is next to the Technopark campus and is similar to the Pongumoodu site, but more extensive, with some open Eucalyptus forest and grassland and wetland grazed by cows, goats, and water buffalo. Church Forest (closed canopy; 8°33′40.3″N 76°54′29.9″E), is a small forested valley owned by a church. It has some coconut and old fruit trees (mango, cashew), and on higher ground a small rubber plantation. Mookkunimala (closed canopy; 8°47’11.1”N, 77°01’16.3”E) is a rocky hill partly covered in rubber plantations, and steep and rocky sections are covered in wild thicket vegetation. Rubber trees are about 5–10 meters high, and the understory is regularly cut to allow easy access for rubber tapping and to reduce competition for the rubber trees, thus forming a forest-like habitat with a dense herb layer. The site also features stone quarries, and part of the hill is used as a shooting range. Notably, our sampling was cut short here as bonnet macaques started to break our traps, as they eat both the bait and trapped insects. The Vithura site (natural forest; 8°41'01.3"N, 77°08'18.5"E) is a natural semi-deciduous forest within the campus of the Indian Institute for Science Education and Research, Thiruvananthapuram. It borders the protected forest of the Peppara Wildlife Sanctuary in Agasthyamalai Biosphere Reserve. We also sampled a rubber plantation next to the forest. Butterfly sampling At each site, we caught butterflies with fruit-baited traps. These traps consisted of a white mesh cylinder, 125 cm tall and 35 cm wide, fitted with a bait plate, so that butterflies fly up into the trap after feeding on the bait. Traps were hung from tree branches so that the base of the traps was about 40 cm from the ground. The distance between traps was at least 30 m. The bait consisted of bananas that were sliced and mashed, and then left to ferment for at least three days in a loosely closed bucket. We baited traps with a serving spoon of bait, and we then typically documented the butterflies caught in the traps during the subsequent 2–3 days. Traps were usually visited during the early afternoon (2–3 PM), adding bait when necessary. The timing and frequency of sampling differed greatly between sites, depending on accessibility (e.g. Church Forest was blocked by a building site), conflict with monkeys (Mookkunimala), weather, and scheduling of other activities. To document the butterflies caught, we photographed them before release, usually against a standard background. We identified the butterflies on the photographs with the help of the iFoundButterflies website (Kunte, Sondhi, and Roy 2025) and Kunte (2000). Occasional captures of nectar-feeding species were excluded from analyses.