Kerala groves sustain insect predation
A new study finds caterpillar predation rates are significantly higher in Kerala's sacred groves than in nearby home gardens, showing these small, culturally protected forest patches help sustain predator-prey interactions.
A study in Kerala has found that caterpillar predation is significantly higher in sacred groves than in nearby multi-storied home gardens. The research, conducted in the Kasaragod district, indicates these small, culturally protected forest patches help sustain predator-prey interactions that regulate insect populations.
Gopika Viswan, a researcher at the Ecology Lab of the Central University of Kerala and a study co-author, explains the importance of these findings. The study suggests that sacred groves, often relics of ancient forests, preserve ecological functions in human-dominated landscapes.
Testing fragmentation effects
The fieldwork was carried out during January and February in 2024 and 2025. Researchers selected 12 sites located between 8 and 44 kilometres from the Western Ghats biodiversity hotspot. At each site, they paired one sacred grove with one nearby multi-storied home garden, located 1-2 kilometres apart, to compare interactions.
Palatty Allesh Sinu, the study's corresponding author, noted the setup allowed them to test aspects of island biogeography theory.
To measure predation, the team deployed 1,296 artificial plasticine caterpillars across the habitats. After 48 hours, they retrieved the models and analysed distinctive bite marks left by predators. In the second year, they also deployed 864 freeze-killed mealworms wrapped in adhesive to help identify the insects involved.
Predator patterns and surprising results
Overall predation rates were significantly higher in sacred groves. The study broke down the attacks by predator type and caterpillar colour.
| Predator Group | Attack Contribution |
|---|---|
| Arthropods (e.g., ants) | 57-61% |
| Birds | 22-35% |
Green caterpillars were attacked less frequently than brown ones, largely due to lower arthropod predation. Attacks were also less common on leaves than on branches or stems.
Some results challenged expectations. Predation did not show a uniform decline with increasing distance from the Western Ghats. While predation declined with distance within sacred groves, it actually increased in home gardens. The contrasting responses suggest fragmentation effects depend strongly on habitat type.
The role of habitat complexity
The researchers also found that the size of a sacred grove did not explain the observed predation patterns. This indicates that habitat quality and structural complexity, rather than patch size alone, were driving predator activity. Consistently high predation was maintained within sacred groves despite their small size and isolation.
Bhavya Lakshmi, another co-author, emphasised this point, noting that sacred groves maintained high levels of predation across all major predator guilds, demonstrating that habitat complexity can buffer the negative effects of fragmentation.
The study recorded relatively high levels of bird predation compared to many previous tropical studies. Viswan suggested the relatively large size of the artificial caterpillars used, coupled with the region's diverse community of insectivorous birds, likely contributed to this result.
The findings reinforce that conservation in fragmented landscapes cannot rely solely on large, continuous forests. Small, culturally conserved forest patches like sacred groves can maintain ecological functions even when isolated. The research was published on the Mongabay-India website.
