Conservation Management of the Mariana Eight Spot Butterfly

Abstract

Approximately two hundred acres of non-contiguous limestone forest habitat at AAFB NWF were surveyed to determine distribution and abundance of hostplants (Elatostema calcareum and Procris penduculata) for the federally listed Mariana eight spot butterfly, Hypolimnas octocula marianensis. State of the art GIS techniques were employed to carry out 5-10m wide transects throughout the entire survey area from November 2016 through January 2017. Both host plant species were generally restricted to a narrow band of pinnacle karren habitat adjacent to and paralleling the NWF cliffline and less often in pockets of subdued karren. Elatostema calcareum was more greatly dispersed than Procris pendunculata, but more of the latter plant occurred as mature individuals. The highest ever recorded densities of eight spot butterfly eggs were observed, particularly on P. pendunculata during the survey. Larvae and adults were also evident. The scarcity of host plants in subdued karren implicates the role of ungulates in restricting these plants to hard-to-access pinnacle karren substrate. These results underscore the importance of cliff line pinnacle karren habitat for the conservation of the butterfly and supports the need to control populations of ungulates and other invasive species, which are threats to the host plants.