Technical note usda natural resources conservation service pacific islands area

Yüklə 1,86 Mb.
ölçüsü1,86 Mb.
  1   2   3   4   5   6


Biology Technical Note No. 20
Bats of the U.S. Pacific Islands

Hawaiian hoary bat Mariana fruit bat Samoan flying fox

‘Ōpe‘ape‘a Fanihi Pe‘a vao
Purpose. To provide an introduction to the habitat requirements of bats in Hawai‘i, American Samoa, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI) and general guidance on conservation practices to enhance and manage bat habitats.


INSECTIVOROUS BATS (insect-eating bats) Page

Hawaiian Hoary Bat 2

Pacific Sheath-tailed Bat 5

Potential Threats to Insectivorous Bats 7

Summary of Habitat Components – Insectivorous bats 9

Assessment of Limiting Factors - Insectivorous bats 9

Management Recommendations – Insectivorous bats 10

FRUGIVOROUS BATS (fruit-eating bats)

Mariana Fruit Bat 12

Samoan Flying Fox 15

Pacific Flying Fox 18

Potential Threats to Frugivorous Bats 21

Summary of Habitat Components – Frugivorous bats 23

Assessment of Limiting Factors - Frugivorous bats 24

Management Recommendations – Frugivorous bats 24

What to do with a sick or injured (or dead) bat? 26

Contacts for more info on bats and other wildlife 26

Common and scientific names of animals and plants in text 26

References 27

Web Resources 28

Appendices (plant lists, FAQs about bats and crops, summaries, range maps) 28


Written by Kimberly Uyehara and Gary Wiles for the USDA, Natural Resources Conservation Service, Pacific Islands Area. Improved by comments from Sandra Banack, Julia Boland, Frank Bonaccorso, Anne Brooke, Joy Browning, Mark Defley, Jacqueline Flores, Kathleen Friday, Dustin Janeke, Wallace Jennings, Gregory Koob, Ann Marshall, Theresa Menard, Thomas O’Shea, Athena Pratt, Joseph Ruak, P. Quentin Tomich, and Joseph Tuquero. Photos provided courtesy of Bat Conservation International, Honolulu Zoo, U.S. Geological Survey, Art Whistler, and many others credited below.


Federal – Endangered

State – Endangered

Species Profile

Hawaiian hoary bat, ‘ōpe‘ape‘a
Scientific name: Lasiurus cinereus semotus

Habit: Solitary, nocturnal

Average wingspan: 10.5 - 13.5 inches (26.9 - 34.6 cm)

Weight: male 0.5 oz (14.2 g); female 0.6 oz (17.9 g)

Range: main Hawaiian Islands

Approximate breeding period: April - December

No. of pups per year: 2 (twins)

Roosting habitat: Trees with dense foliage

Foraging habitat: Open and wooded landscapes and linear habitats such as windbreaks and riparian corridors

Food habits: Aerial insectivore - eats night-flying insects primarily moths, beetles, and termites

Population estimate: unknown

Photo Honolulu Zoo

The Hawaiian hoary bat or ‘ōpe‘ape‘a is a medium-sized member of the vesper bat family (Vespertillionidae) which consists of nocturnal, mostly insect-eating bats. It is an endemic subspecies of the North American hoary bat, a solitary tree-roosting species (does not use bat boxes). ‘Ōpe‘ape‘a has frosted brown and gray fur which gives it a hoary appearance. Fur color, frosted or reddish, may be related to location or age. The best time to observe Hawaii’s only native land mammal is at sunset when it comes out to feed. It’s a major predator of night-flying insects such as moths, beetles, and termites. Insectivorous bats play an important role in regulating insect populations of natural and agricultural ecosystems.


Although the number of bats is unknown, resident populations occur on Kaua‘i, Maui, and Hawai‘i and possibly other main islands, with the largest numbers on Kaua‘i and Hawai‘i. Bats occur at all elevations, with the majority of sightings below 7500 ft (2286 m) on Hawai‘i and in lowlands on Kaua‘i. Local occurrence is influenced by insect prey abundance (1). It is a Federal and State endangered subspecies, but many have questioned whether the subspecies is truly endangered with so little known about its status. In 2002, the Hawaiian Hoary Bat Research Cooperative was formed to overcome the challenges of recovering Hawaii’s elusive ‘ōpe‘ape‘a. The cooperative includes over 25 entities representing wildlife conservationists, foresters, agriculturalists, land managers, and researchers working toward sustainable conservation and development.

Photo Honolulu Zoo

‘Ōpe‘ape‘a appear to make altitudinal migrations between lowland breeding and highland wintering grounds, at least in windward Hawai‘i, spending about May-November in lowlands and January-April in highlands (>5250 ft [1600 m]) (2,3). Although a fall mating period has been suggested (4), the mating period is unknown. Pregnant females have been observed April to August. A 2-3 month gestation (pregnancy) is followed by about a 2-3 month nursing period (5). Females are believed to give birth to twins between May and August and rear pups between May and September. Pups fledge (take first flights) from about July-September, which is a critical time in the reproductive cycle. Although unknown for the Hawaiian subspecies, hoary bat pups in Canada fledge within 4-5 weeks and are weaned at about 7 weeks of age (6).

Approximate periods of breeding activity in ‘ōpe‘ape‘a (2,4,5)


















Pup births


Pup fledging

Wet season Dry season

‘Ōpe‘ape‘a occur in nearly every habitat within their range including native, nonnative, agricultural, and developed landscapes. Habitat examples:

  • Barren land. Volcano craters and lava fields for foraging

  • Cropland. Macadamia nut farms with tall windbreaks and other orchards for foraging and roosting

  • Developed land. Golf courses, urban areas, suburban yards, rural roads, and farmsteads for foraging and roosting

  • Forest land. Eucalyptus plantations, albizia-dominant forest, ‘ōhi‘a-dominant forest, koa-dominant forest, and māmane-naio forest for foraging and roosting

  • Other rural land. Rural yards and windbreaks for foraging and roosting

  • Pastureland. Grazed lands with a forest component for foraging

  • Rangeland. Fallow fields near forest for foraging

  • Water areas. Reservoirs, wetlands, river corridors, and coastal waters for foraging

Food. ‘Ōpe‘ape‘a forage on moths, beetles, termites, leafhoppers, flies, bugs, and other night-flying insects (7). Prey is located using an advanced technique known as echolocation (bats detect size, distance, and shape of prey by emitting and interpreting sound pulses that bounce off objects). In open habitats, medium-sized moths (0.6-0.8 inches [16-20 mm] long) are preferred over large moths (>0.8 inches [20 mm]) and small moths and flies (<0.4 [10 mm]) (8). In forested habitats, bats feed on a variety of small insects (9).

A North American hoary bat echolocates and captures moth prey (Photos © Merlin D. Tuttle, Bat Conservation International).

over (foraging).
‘Ōpe‘ape‘a forage in open, wooded, and linear habitats. Vegetation varies widely. On Hawai‘i, bats fed 65-165 ft (20-50 m) above an ‘ōhi‘a forest-pasture patchwork and >50 ft (15 m) above māmane-naio forest (10). Bats also forage regularly below the forest canopy down to within 2 ft (0.5 m) of ground (11), along forest edges and gaps (e.g., eucalyptus plantations adjacent to fallow fields), and in croplands with structural diversity (e.g., macadamia nut farms with tall windbreaks) (5).
Bats are attracted to flying insects attracted to macadamia flowers, and also feed along the edges of tall windbreaks (11) (Photo K. Uyehara).

over (roosting).
Vegetation cover and structure appear to be more important than tree species, as bats readily use both native and nonnative trees such as eucalyptus, mango, lychee, avocado, albizia, ‘ōhi‘a, and pandanus (12). On Hawai‘i, roosts are located in dense canopy foliage (or subcanopy when canopy is sparse) with open access for launching into flight. Bats generally roost below 15 ft (5 m) in macadamia and Cook pine and above 15 ft (5 m) in eucalyptus (13). There are a few records of bats occurring in lava tubes and other cavities (14,15).
Water. Foods presumably meet water requirements. ‘Ōpe‘ape‘a are not known to drink from water bodies, but are regularly observed foraging over streams, reservoirs, wetlands, stream mouths and out to about 330 ft (100 m) offshore (10). Bats may be attracted to insects of lush riparian vegetation or insects emerging from water, as many flying insects have aquatic larval stages (11).
Interspersion of habitat components. Suitable foraging and roosting habitat near one another is preferable. Although the optimal interspersion (mix of habitat types) is unknown, varied habitat structure near riparian corridors or other insect-rich habitats appears beneficial.
Minimum habitat area. ‘Ōpe‘ape‘a are capable of both high altitude and interisland flight. They require large areas that may encompass multiple landowners. For example, home range (area a bat normally uses for foraging and roosting) for males on a macadamia nut farm averages 124 ac (50 ha), but bats can also commute >7 miles (11 km) from roosts to foraging areas. Home range size varies with habitat type and territories may overlap (5).


Federal – Candidate

Guam – Endangered

CNMI – Threatened/Endangered

American Samoa – Protected


Species Profile

Pacific sheath-tailed bat

fanihin liyang, fanihen toyu, payesyes (Guam)

liyang, payesyes, pai‘scheei (CNMI)

peapea vai (American Samoa)

Photo E. Valdez, USGS

Scientific name: Emballonura semicaudata

Habit: Colonial, nocturnal

Total length: 2.4 - 2.9 inches (60 - 74 mm)

Weight: male 0.19 oz (5.5 g); female 0.25 oz (7.2 g)

Range: Micronesia, Melanesia, Polynesia

Breeding period: Unknown

No. of pups per year: Probably 1

Roosting habitat: Caves, crevices, and other cavities

Foraging habitat: Mainly forests

Food habits: Aerial insectivore - eats small night-flying insects

Population estimate: 400 - 500 (Aguiguan, CNMI); extirpated (Guam); possibly extirpated (American Samoa)

The Pacific sheath-tailed bat is a member of the sheath-tailed, sac-winged, and ghost bat family (Emballonuridae), which consists of mainly nocturnal, colonial, cavity-dwelling, insect-eaters. Its name comes from the sheath (little tube) around the tail formed by the uropatagium (skin connecting the tail and hind legs). The sheath allows the bat to adjust the length of its uropagatium in flight and skillfully maneuver the forest understory. The Pacific sheath-tailed bat is a small bat, often mistaken for a swiftlet with which it commonly roosts in caves. Little is known about this rapidly declining species.
Pacific sheath-tailed bats occur in the islands of the Marianas, the Carolines, Vanuatu, Fiji, Tonga, and Samoa (4 subspecies). They are common in Palau and Pohnpei in the Carolines, but have greatly declined or disappeared in many other parts of their range in recent decades. One subspecies is known only from the Mariana Islands. The only population of this subspecies contains about 400-500 bats on Aguiguan in the CNMI (16). Bats are now extirpated (locally extinct) on Guam and possibly American Samoa (17-19). They are protected locally in Guam, the CNMI, and American Samoa and are a candidate for Federal listing under the Endangered Species Act.
Almost nothing is known about their breeding biology. A pregnant female with one embryo was collected on Aguiguan in the month of June (17).

Although information is lacking on habitat requirements, research on the Aguiguan population and general observations from other islands shed light. Pacific sheath-tailed bats generally roost in caves, but large tree hollows are also occupied in Pohnpei. Detailed studies on their echolocation sounds at night show that on Aguiguan they feed mainly in native limestone forest (16). General observations elsewhere suggest that they can also use other native, nonnative, agricultural, and developed landscapes. Habitat examples:

  • Barren land. Caves, crevices, and other cavities for roosting

  • Cropland. Coconut groves for foraging

  • Developed land. Rural roads, windbreaks, rural yards for foraging

  • Forest land. Native forest, secondary forest, agroforest for foraging; tree hollows and other cavities for roosting

  • Rangeland. Shrublands or fallow fields near forest for foraging

Aguiguan is a 1779-acre (720 ha) limestone island located 5.6 miles (9 km) southwest of the Island of Tinian, CNMI. Here, Pacific sheath-tailed bat habitats include caves along sea cliffs and native forest (Photos P.M. Gorresen, USGS).
Food. Pacific sheath-tailed bats forage on small night-flying insects. Prey is located by echolocation (bats detect size, distance, and shape of prey by emitting and interpreting sound pulses that bounce off objects).

Cover (foraging). Bats forage in native and nonnative forested landscapes. On Aguiguan, bats emerge from their caves around the time of sunset to begin foraging. Bats feed on insects in the understory down to <3 ft (1 m) above ground, but also in and above the upper forest canopy and around tall ironwood trees (16,20). On Pohnpei, bats were observed during the day in dense native forest, presumably foraging (21).

Cover (roosting). Bats roost in caves, but also crevices, lava tubes, rock depressions, overhanging cliffs, hollows of large trees (22), rock falls, and even under bridges (19). On Aguiguan, bats roost in large to medium-sized caves ranging from 13-82 ft [4-25 m] tall, 3-148 ft [1-45 m] wide, and 30-165 ft [9-50 m] long on cave ceilings and upper walls in areas of darkness or dim ambient light (23).

Water. Foods presumably meet water requirements. Like other insectivorous bats, they probably forage in insect-rich mangrove swamps and riparian zones when available.

Interspersion of habitat components. Suitable roosting habitat near insect-rich foraging habitats is favorable.

Minimum habitat area. Home range is unknown. On Aguiguan, 400-500 bats rely on 741-988 ac (300-400 ha) of native limestone forest (16). On Palau, some bats fly ≥3 miles (5 km) to forage (24).
POTENTIAL THREATS – Insectivorous bats

USGS research biologists and associates collect data to assess the status of Pacific sheath-tailed bats on Aguiguan, the site of the last known population in the Mariana Islands (Photo E. Valdez, USGS).

Descriptions of threats to Hawaiian hoary bats and Pacific sheath-tailed bats are mostly speculative. Thus, for Hawaiian hoary bats we address potential threats to help prevent these factors from becoming a problem in the future. For Pacific sheath-tailed bats we address suspected threats because populations are disappearing before threats can be identified.

Roost disturbance. Roost disturbance is a common threat to bats worldwide. For Hawaiian hoary bats, this may include: (a) clearing trees that bats roost in, (b) loud unpredictable activities such as building a structure near a bat roosting site, or (c) other human activities that alter normal feeding and breeding patterns or cause direct mortality, which would be violations of Federal and State endangered species laws. Roost disturbance when juvenile hoary bats are fledging (Jul-Sep) has the highest potential for negative impacts (11). Hawaiian hoary bats don’t seem to have high roost site fidelity (may return to the same area but not necessarily the same tree), use roosts seasonally, and are adaptive to human-modified landscapes (5). Pacific sheath-tailed bats readily flush from caves during the day when disturbed. On Aguiguan, some remaining colonies are found in large cliff-side caves inaccessible to humans and feral ungulates (20), suggesting that these bats are sensitive to noise caused during cave intrusions.

Pacific sheath-tailed bat habitat on Aguiguan, note over-browsing by feral goats (Photo P.M. Gorresen, USGS)

oss of habitat.
Loss of native forests from agricultural conversions, other types of development, and/or WWII destruction historically contributed to Hawaiian hoary bat and Pacific sheath-tailed bat habitat loss. Although secondary forests and plantations have replaced some native forests, invasive plants and animals such as feral ungulates continue to contribute to Pacific sheath-tailed bat habitat loss and degradation (16). Cave destruction, especially during WWII, eliminated some Pacific sheath-tailed bat roosting habitat in the Marianas and perhaps elsewhere.

Yüklə 1,86 Mb.

Dostları ilə paylaş:
  1   2   3   4   5   6

Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2020
rəhbərliyinə müraciət

    Ana səhifə