Hawaiian Hoary Bat

Bats in Hawaii: No April Fool’s | Islands’ Only Native Land Mammal

This is no April Fool’s. There are bats on the islands called Hawaiian Hoary. It may be even more of a surprise to learn that these Hawaii animals are the only endemic land mammals in Hawaii and one of only two species of endemic Hawaiian mammals. The other one is the beloved Hawaiian monk seal.

We’ve both lived here for a long time and had never seen a Hawaiian Hoary bat until recently. Then one evening while walking along Kauai’s Hanalei Bay, we noticed what we thought were birds flying at sunset over the shoreline. Upon closer inspection of their unique flying patterns, we realized that these were the endangered Hawaiian Hoary bats.

The presence of Hoary bats was recently confirmed on a remote island west of Maui, Koolawe. That in addition to Kauai, Maui and the Big Island. There have also been sightings on Oahu and Molokai.

Hawaiian Hoary bats | Native terrestrial mammal.

Before there were people in Hawaii, everything in the Hawaiian Islands got here by wing or wave. And so it is with Hoary bats, which are one of 1,300 species of bats. It’s thought that the animals migrated to Hawaii from North America at two separate times. Scientists believe that occurred about a thousand years ago and before that about ten thousand years ago.

These bats, whose technical name is lasiurus cinereus semotus, are the only remaining native land mammal in the state, and are considered an endangered species. ‘They go by the Hawaiian name ʻōpeʻapeʻa. That transates to half-leaf, and relates to the appearance of the bat’s open wing, which can have a wingspan of up to 1 foot.

Hoary bats roost in trees, which is where we have seen them, although people believed they nested in lava tubes. During the evening they can be seen eating insects. The bats are brown/gray with white tips at their extremities and have a unique fur pattern.

Since 1970, they have been on the U.S. Fish and Wildlife Service’s and Hawaii’s lists of endangered species. Damage to their populations has probably been the result of loss of habitats due to deforestation and pesticide use, barbed wire fences, and collisions with the blades of wind turbines, among other things.

Kawailoa Wind Farm on Oahu, Hawaii’s largest, is using sound to encourage bats to move away. Bat deaths do still occur there, however. Conservation studies on bats have been ongoing for the past two decades. A prior study estimated that up to 100,000 bats of multiple species died from wind turbine collisions in the United States and Canada.

The hoary bat eats insects and lives in forests. They’re solitary creatures and grow to about 6 inches, with a body weight of about an ounce, and have a wing span of only 12 inches. Recent research indicates that Ōpe‘ape‘a dart to and from, eating up to 40% of their body weight in prey during a single night, and that includes insects, such as moths, mosquitoes, beetles, termites, and crickets.

Mother bats typically give birth to pups in sets of twins during the spring.

Hoary Bats. Where to find them.

Beautiful to watch, Hawaiian hoary bats typically seek solitude, so you won’t find them flying around in Honolulu. Their largest populations are on the Big Island and Kauai, although they can still be seen on all of the islands. Most people we’ve spoken with have rarely, if ever, seen them. As is common with other bats, they’re mostly seen in the early evening, just before dark. At that time they’ll be feeding over streams, bays, or in our recent sighting, along the coast.

Other Interesting Facts About Hoary Bats.

While relatively little is still known about them, they’re believed to roost in trees and live at altitudes varying from sea level to the tallest peaks of Hawaiʻi. They’re found on all of the major Hawaiian Islands as well as Lanai and Kaho’olawe.

Hoary bats emit various sounds. These include high frequency calls used to detect their insect diet as well as low frequency, humanly audible social sounds. It’s also thought that some Hawaiian moths can even hear the high pitched sounds and thus avoid becoming part of the bat’s diet.

Have you seen a Hawaiian Hoary bat?

Photo by USGS.

12 thoughts on “Bats in Hawaii: No April Fool’s | Islands’ Only Native Land Mammal”

  1. Aloha Rob and Jeff!
    This is a great article about the cutest mammals in the islands!
    I’ve never seen one, but it’s always because I’m going a thousand miles an hour and don’t always take the time to pay attention to the awesomeness around us.🌺
    I lost my best friend on Saturday and I’m still trying to wrap my head around the fact that she was fine a couple weeks ago and then gone. She forgot to live like there’s no tomorrow. We’re never promised another day.
    Mahalo for reminding me to look.

    1. Hi Pam.

      Thanks for checking in. We both send condolences on learning of you’re loss. She they is an important message.


  2. Love bats. I watch them all summer from my second deck here in Arizona getting bugs. I see them from my light shining on my American and Arizona flags. They fly circles in the night to get bugs. Very cool to watch. I would love to see them from my place in Kauai. I even had one fly in my house in the summer and circled the ceiling fan several times but luckily he found his way out of the French doors. Fascinating creatures.

  3. BOE,

    We have bats in our backyard – in the summer, we watch them dive down to catch flying insects. Southern California, high desert.

    I don’t understand why bats that arrived there 1,000 and 10,000 years ago are endemic – doesn’t that mean “native to?”


    1. Hi Rod.

      They’re considered native and yes, they arrived here 10k years ago. Both are true – we aren’t sure why that is. Hopefully someone who knows more can help.


      1. Thanks. Maybe if something has been in a place for a very long time, and obviously adapted, it’s endemic/native.

      2. Endemic is when something is only found in an area, another example in Hawai’i is the nene.

  4. Mahalo, Guys I will use this information as I talk about a lot about Hawaii being the extinction capital of the world. I also mention your web site often as you were so helpful explaining the ins and outs of the Covid restrictions.

  5. Anything that eats mosquitoes is OK with me. Are there still red dragonflies on Kauai? I remember seeing some there.

  6. Aloha BOH,
    We have seen the Hoary Bats at sunset at Napili Bay on Maui – my husband had binoculars and we were both surprised at the sight of them flying out of palm trees! Thanks for this information!

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