An official website of the United States government
Here's how you know
A .mil website belongs to an official U.S. Department of Defense organization in the United States.
A lock (lock ) or https:// means you’ve safely connected to the .mil website. Share sensitive information only on official, secure websites.

Protecting the Hawaiian Hoary Bat During Pupping Season

20 July 2023

From MC2 Bodie Estep

PACIFIC MISSILE RANGE FACILITY, Hawaii - The endangered ʻŌpeʻapeʻa, or Hawaiian Hoary Bat, is a solitary, tree roosting bat. The pups, or babies, cannot fly and hang in the trees so it is recommended to not trim trees taller than 15 feet during pupping season, which is June1-September 15.

     Generally speaking, no one wants to be bitten and bothered by pests such as mosquitos. More than just the general annoyance mosquitoes cause, they are actually an invasive species that play a hand in population declines of native forest birds due to the diseases they carry. Luckily, there are a variety of animals that help with controlling insect numbers. Microbats are one such animal, eating about 40% of their body weight in insects every night.

     “One of Kauai’s lesser known cute critters is the endangered Hawaiian Hoary Bat - Hawaii’s only native land mammal,” said Capt. Brett Stevenson, commanding officer, Pacific Missile Range Facility (PMRF), Barking Sands. “The bats are highly beneficial in keeping the mosquito population in check here on base.” 

     There are over 900 species of microbats throughout the world and they can weigh as little as three grams. The Hawaiian Hoary Bat, or ʻŌpeʻapeʻa in Hawaiian, is considered large for a microbat, weighing in at up to 14 grams. However, comparably speaking that is still not very big when considering 14 grams is only about the weight of three quarters.

     The ʻŌpeʻapeʻa is solitary and tree-roosting, so they do not nest in caves like other bats. The Hawaiian name means “half-leaf.” This name stems from the fact that their wings resemble the bottom of a taro leaf. Hoary, which means grayish white, is a reference to the frosty color on its back.

     The ʻŌpeʻapeʻa differs from other bats for other reasons as well. They are one of the very few species of bat that use calls at a frequency low enough that humans can hear it. Also, thanks to Hawaii being rabies-free, these bats do not carry rabies, even though they are susceptible to it. 

     Despite these fun facts, there is actually very little known about the ʻŌpeʻapeʻa. They are very difficult to find, making it a challenge to learn much about them. This means that there isn’t even an accurate number for the population.

     Adding to the already difficult process of protecting this species, the babies, or pups, are unable to fly. Due to this, they hang in the tops of trees until they are old enough to ​​learn. Brooke McFarland, Natural Resources Manager for PMRF, stresses that in order to protect the pups hanging in the trees, it is crucial to avoid cutting or trimming trees that are over 15 feet tall during pupping season, which is June 1 to September 15. It is very difficult to see these tiny bats and the best way to avoid knocking them out of the trees or injuring them is to not cut the trees. If a pup is knocked from the tree, there is likely nothing that can be done to help it. Once it is down, it can reasonably be considered a loss.   

     “The bats are rare, so one is unlikely to be in a random single tree,” said Stephen Rossiter, a field biology coordinator with PMRF. “However, because they are rare, if there were one in that tree, it is important to protect it.” 

     To protect this endangered species, which has the benefit of minimizing invasive mosquitoes and other pests on base, PMRF will continue to regulate tree trimming during pupping season, June 1-September 15. 

     For any questions regarding tree trimming on base during this period, contact the PMRF environmental hotline at (808) 208-4416 or


Google Translation Disclaimer

  • Google Translate, a third party service provided by Google, performs all translations directly and dynamically.
  • Commander, Navy Region Europe, Africa, Central, has no control over the features, functions, or performance of the Google Translate service.
  • The automated translations should not be considered exact and should be used only as an approximation of the original English language content.
  • This service is meant solely for the assistance of limited English-speaking users of the website.
  • Commander, Navy Region Europe, Africa, Central, does not warrant the accuracy, reliability, or timeliness of any information translated.
  • Some items cannot be translated, including but not limited to image buttons, drop down menus, graphics, photos, or portable document formats (pdfs).
  • Commander, Navy Region Europe, Africa, Central, does not directly endorse Google Translate or imply that it is the only language translation solution available to users.
  • All site visitors may choose to use similar tools for their translation needs. Any individuals or parties that use Commander, Navy Region Europe, Africa, Central, content in translated form, whether by Google Translate or by any other translation services, do so at their own risk.
  • IE users: Please note that Google Translate may not render correctly when using Internet Explorer. Users are advised to use MS Edge, Safari, Chrome, or Firefox browser to take full advantage of the Google Translate feature.
  • The official text of content on this site is the English version found on this website. If any questions arise related to the accuracy of the information contained in translated text, refer to the English version on this website, it is the official version.

Commander, Navy Region Europe, Africa, Central   |   PSC 817, Box 108   |   FPO, AE 09622
Official U.S. Navy Website