By Iwan Shinyo
During the months of September and October 2015, our butterfly surveys and all OuTrop research was suspended due to the extreme fires that ravaged the forests near our study area. Fortunately, the areas we normally carry out butterfly surveys each month were not affected by the fires. However, the OuTrop Biodiversity Team decided to try to carry out butterfly surveys on the edge of the forest adjacent to the newly burnt forest towards the east of our study area. We started these surveys adjacent to the burnt area during April 2016 as part of a Master’s student’s project from the University of Leicester. The student and OuTrop’s Biodiversity Team wanted to see how butterfly populations near the burnt area of forest may or may not differ from butterfly populations within the forest interior.
The results from the month of April from the butterfly traps inside the forest were very different from the results we found from the burnt area traps. Only 5 different species of butterfly were caught (i.e. comparable to normal species distribution caught in the traps), with a total of 98 butterflies caught in the traps within the forest interior. In the butterfly traps adjacent to the burnt area, 11 different species of butterfly and a total of 178 butterflies in all were caught in the burnt area traps. Out of the 178 butterflies caught, the dominant species of butterfly caught (65% of total butterflies caught) was Melanitis leda. Two questions raised by these findings were: 1. why were so many butterflies caught adjacent to the burnt area and 2. why was the predominant species caught Melanitis leda?
The OuTrop Biodiversity Team then decided to continue the butterfly surveys next to the burnt area, in addition to the regular surveys within the forest interior, through May and June. After June, it became too dangerous to carry out the surveys near the burnt area because of the risk of falling dead trees, so unfortunately we had to suspend that research. In May, there were still 24 more butterflies caught in the burnt area traps than the traps within the interior of the forest. However, in June, the butterfly population caught within the burnt area traps fell to only 41 individuals, compared to 79 individuals caught in the forest interior butterfly traps. Throughout May and June, though, Melanitis leda was still the dominant species caught in the burnt area traps.
And still the questions persist…Why were more butterflies caught in the burnt area during April and May compared to the forest interior? Why did the burnt area population then fall in the month of June, but the species Melanitis leda appeared to still thrive in the burnt area? OuTrop’s Biodiversity Team hypothesizes that during the months of April and May, there was still a good amount of rainfall that created an abundance of dust and fungi near the burnt area from the rotting wood. This may have created more suitable conditions for the butterfly species to thrive than compared to the conditions within the forest interior, particularly ideal for the species Melanitis leda. During the month of June, we speculate that rainfall decreased significantly compared to the previous months, with the dry season fast approaching. The lessening rainfall could have caused a decrease in the amount of fungi and dust near the burnt area, which may have made the conditions less favorable for butterflies there and explain why the population fell. This is only a preliminary hypothesis from the team, because we still need more data to have a sufficient dataset to analyse. It is extremely important to monitor the butterfly populations within our forest post-fire to determine if the populations are experiencing any post-fire effects and what this could indicate for the rest of the forest, as butterflies are often used as indicator species. We hope to resume butterfly surveys adjacent to the burnt area in the future once the conditions there become safer, so stay tuned for more information from this project.
TO BE CONTINUED…