Temporal Variations of Interactions between Endemic Pseudophilautus regius (The Polonnaruwa Shrub Frog) and Two Carnivorous Plants in Sri Lanka

Abstract

The Polonnaruwa shrub frog, Pseudophilautus regius is an endemic Rhacophoridae species in Sri Lanka whose ecological interactions are crucial for its conservation. This study examined temporal variations in interactions between the Polonnaruwa shrub frog and two carnivorous plants, Sarracenia flava and Nepenthes in an open greenhouse in Polonnaruwa (7.946140N, 81.013930E). Associations of shrub frogs with pitchers of five Sarracenia and ten Nepenthes plants were studied. Focal animal sampling was employed to quantify the behaviour. Observations were conducted from August to November 2024 from 06:00 h to 22:00 h. Mean daytime (06:00 h to 18:00 h) and nighttime (18:00 h to 06:00 h) temperatures during the study were 33 °C and 26 °C, respectively. A total of 36 frogs were observed inside Sarracenia pitchers during daytime, with no observations after 18:00 h. Inside Nepenthes pitchers, frogs were mostly observed between 17:00 h and 19:00 h (2 individuals) and 20:00 h and 22:00 h (4 individuals), with no observations between 07:00 h and 16:00 h. All observed behaviours inside Sarracenia pitchers were resting (100%). In contrast, frogs inside Nepenthes spent 83.33% of the total observation time on foraging and 16.67% on resting. This significant difference in plant use indicates that frogs utilise Sarracenia pitchers for daytime roosting to avoid temperature variations and high light intensity and Nepenthes pitchers as a foraging platform during low light hours. These findings demonstrate the importance of both Sarracenia and Nepenthes for P. regius in terms of foraging, thermoregulation, and adaptability to environmental variations presented by novel plant species. This provides valuable insights into the adaptability of Polonnaruwa shrub frogs to such novel microhabitats.

Keywords: Nepenthes, Polonnaruwa shrub frog, Pseudophilautus regius, Sarracenia, Temporal interactions