From this collaboration, a standardized method was developed to survey the presence or absence of Hawaiian Hoary Bats on Kahoʻolawe by installing bat detectors across the island in varying habitats. An endangered species, theʻōpeʻapeʻa (Lasiurus cinereus semotus) poses many biological questions that need clarification, e.g. are they on island? If so, how do they utilize the island habitat?
After one year of data collection, preliminary analysis has confirmed the presence of ʻōpeʻapeʻa— with interesting discoveries unique to Kahoʻolawe:
- From the data recorders, the presence of the Hawaiian bats occur only seasonally.
- The first bat detection occurred in June 2016 and detections stayed low until late summer where detectors reached a peak detection rate of 26% probability across the island. Furthermore, all 8 of the Bat detectors recorded bats in all habitats across the Island.
- After September and into December, the detections dropped off until in January the detections ceased altogether.
In addition to this data, the time of night the bats were recorded revealed another interesting find: the bats were not recorded until 2-3 hours after sunset and only until 3-4 hours before sunrise. This information suggests that the ʻōpeʻapeʻa migrate to Kahoʻolawe and then return “home” on a nightly basis, but doesn’t rule out the possibility of a small resident population. The first year of data shows bats being most active from late summer into winter with the peak detection rate in September.
Questions to investigate:
- What is the density of ʻōpeʻapeʻa during the peak times?
- Is there a habitat type that could sustain a permanent population on Kahoʻolawe?
- How are the wind farms on Maui affecting the seasonal and nightly migrations to Kahoʻolawe?
The Hawaiian name ʻōpeʻapeʻa, is inspired by the Hawaiian hoary bat's image in flight, which is attributed to the resemblance of canoe sails and the bottom half of the much-celebrated taro leaf (kalo). The term “hoary” refers to their tan, reddish-brown, and silvery coats that appear frosted over. The ʻōpeʻapeʻa is our state mammal.