Obstacles to flight. Obstacles during flight are a major source of mortality for some continental species, particularly during mass migrations. Major sources of mortality include windfarms for migratory tree-roosting bats like the North American hoary bat (25) and barbed wire fences for some migratory bats in Australia (26). Hawaiian hoary bats are not known to migrate in large aggregations. Nevertheless, a small number of individuals have been documented colliding with obstacles (e.g., wall, vehicle, windmill, barbed wire fence), presumably while foraging (2).
Dr. Ben Okimoto monitors the health of a Hawaiian hoary bat with an injured wing (Photo Honolulu Zoo).
ntroduced predators. Young Hawaiian hoary bats may be vulnerable to cats, rats, and other predators during rearing and fledging periods. On Aguiguan, rats and monitor lizards are potential predators of Pacific sheath-tailed bats, and brown tree snakes would be a threat if they reached the island (20).
Pesticides. Insecticides can affect the abundance of insect prey available to Hawaiian hoary bats and Pacific sheath-tailed bats through reduction in insect populations or insect habitat, and may cause bats to fly further in search of food or feed in unfamiliar landscapes. Some insecticides can also affect bats through bioaccumulation of chemicals through the food chain. Herbicides can alter vegetation structure and community composition in foraging habitats, likely influencing the availability of insect prey.
‘Ōpe‘ape‘a skeletal specimen (Photo P.Q. Tomich).
atural phenomena. Natural phenomena can become a factor in species decline for populations already in danger of local extinction. In Guam, CNMI, and American Samoa, typhoons/hurricanes can cause flooding of seaside caves and potentially damage food resources of Pacific sheath-tailed bats. Although storms typically last only a day, storm surges, flooding, tree defoliation, and insect depletions associated with severe storms have longer term effects (22). In American Samoa, coastal caves are small, shallow, and vulnerable to tidal surges (19).
SUMMARY OF HABITAT COMPONENTS – Insectivorous bats
Hawaiian hoary bat
Pacific sheath-tailed bat
Moths, beetles, termites, leafhoppers, flies, bugs and other night-flying insects
Small night-flying insects
Open, wooded, and linear habitats
Forest edges and gaps, croplands with structural diversity
Native and nonnative forests
Forages in forest understory, also in and above upper canopy
Natural phenomena (e.g., severe storms, tidal surges)
ASSESSMENT OF LIMITING FACTORS – Insectivorous bats Using the habitat characteristics above, subjectively rate the (a) availability and quality of bat habitat and (b) presence or absence of potential threats within a planning area. Habitat components rated “low” or “absent” or potential threats rated “present” could be limiting habitat quality.
(a) Habitat component
Quality / Availability
Minimum habitat area
(b) Potential threat
Loss of habitat
Obstacles to flight
MANAGEMENT RECOMMENDATIONS – Insectivorous bats Management treatments should address the habitat components and potential threats that appear to limit habitat potential for bats. Specific management options are lacking for both species. Thus, general advice for insectivorous bats is given below that may increase the quality or availability of each habitat component. NRCS Conservation Practices and various programs that may provide financial or technical assistance to carry out practices are also listed.
Minimize adverse effects of pesticides on non-target species (i.e., reduction in prey and prey habitat) by developing an integrated pest management plan; include role of bats and other native species in reducing pest outbreaks
If insectivorous bats are known or suspected to be foraging in area:
In native forest, protect and enhance habitat especially mature trees and understory; restore new forest patches
Restore forest community structure and function to benefit multiple species of native birds and bats
Consult with NRCS Biologist, Forest Ecologist, or Plant Materials Center for best plant sources, spacing, care, and maintenance (See Appendix A for native plants used by Hawaiian hoary bat)
For Island of Hawai‘i, see NRCS Ecological Site Descriptions for your planning area: http://esis.sc.egov.usda.gov/
314, 382, 550, 612, 643, 645
In orchards, increase horizontal and vertical vegetative structure by enhancing windbreaks; plant multi-species, tree-shrub windbreaks with varied leaf forms; use native species when feasible
380, 612, 645, 650
In tree plantations, avoid extensive clearcuts; integrate selective harvest techniques that leave young trees and snags; create gaps, bays, or irregular forest edges
Leave snags (dead or dying trees) and downed wood; old trees and decomposing woody debris provide good habitat for insects and other organisms eaten by bats
Exclude feral ungulates through fencing or control feral ungulate populations through trapping or hunting
If insectivorous bats are known or suspected to be roosting in area:
Protect roost sites and surrounding habitat by excluding areas from or minimizing activities related to resource extraction, grazing, or vehicular traffic
Hawaiian hoary bat:
Minimize chances of negatively impacting roosting bats by conducting activities such as vegetation clearing or timber harvesting when bats are not or not likely to be present
In windward Hawai‘i, bats are not likely to be present Jan-Apr in lowlands and Jun-Nov in highlands (>5250 ft [1600 m] elevation)
Pacific sheath-tailed bat:
Control feral ungulate access to caves through fencing, gating, trapping, or hunting
Control human access to caves through gating and signage
382, 472, 528, 595, 645
Protect roost sites and surrounding habitat from potential predators
Hawaiian hoary bat:
Keep cats and dogs restrained and away from bat roost sites, particularly during breeding
Hawaiian hoary bats bear young May-Aug and fledge pups Jul-Sep which is the most critical time (see pg. 3)
Pacific sheath-tailed bat:
If rats or monitor lizards are suspected predators, control them through trapping or other wildlife agency approved methods
382, 595, 645
General advice to conserve and enhance insect diversity for bats
If river bank management (e.g., dredging) is necessary, restrict management to small areas or one bank at a time; protect habitat by retaining natural meanders, shallow pools and riffles, and bankside trees and shrubs
Establish riparian buffer zones through fencing, managing roads, runoff, feral ungulates, livestock, and vegetation (for large properties, conduct a watershed analysis to identify and halt or control activities contributing to habitat degradation)
382, 390, 391, 395, 528, 560, 578, 614
Protect and enhance wetlands; including small temporary pool complexes with varied depths, aquatic vegetation, and high insect diversity
644, 646, 659
Avoid introducing nonnative fish to water bodies; fish can deplete aquatic insect communities and degrade water quality
Interspersion and minimum habitat area
Consider relationship of planning area to habitat components on property or neighboring lands. Landowners can manage for bats if one of more of the habitat components is present on their property and adjacent lands provide other habitat components.
Options to prevent potential bat entanglement in barbed wire fences:
Foraging habitat:Forests, farmlands, and coastal strand
Food habits: Frugivorous - eats primarily fruit, also nectar, pollen, flowers, and leaves
Population estimate: 5000 (Marianas)
INTRODUCTION The Mariana fruit bat or fanihi is a medium-sized member of the ecologically important old world fruit bat family (Pteropodidae), which consists of bats that forage primarily on fruit, flowers, nectar, and pollen. It is a striking dark brown to black bat with a golden “cape” around its neck and back. On islands, fruit bats (also known as flying foxes) are often important seed dispersers, playing a critical role in plant reproduction, diversity, and distribution, including post-typhoon plant regeneration (27-29).
STATUS & DISTRIBUTION The species is known from the Caroline (Palau, Ulithi, Yap, Kosrae), Mariana, and formerly Ryukyu islands (6 subspecies). In the Marianas, it was once a common sight. On Guam, fanihi became less common in the 1930s-1940s, then plunged from about 3000 in the 1950s to <50 bats twenty years later. Today, there are an estimated 5000 bats in the CNMI and <100 on Guam (22). Overall, bat numbers in the southern and some northern islands in the chain are in decline, while numbers on some northern islands appear stable (30). Few fanihi survive on Saipan or Tinian. Colonies are believed to move infrequently between islands, probably in response to severe food limitations or colony disturbance (e.g., typhoons followed by poaching), which may explain sudden increases or decreases in bat numbers on individual islands (31). Historically, fanihi coexisted on Guam with little Mariana fruit bats, which are now extinct.
Fanihi are a traditional food source of the people in the Marianas. However, overhunting is a major cause in the bats’ decline, both in the past and presently. Fanihi are Federally-protected as a Threatened species throughout the Mariana Islands. Hunting is prohibited by law until fanihi populations can be restored to larger levels that may allow for sustainable harvests. Recent studies linking regular consumption of fanihi to a disease of the nervous system (known as lytico-bodig) in people on Guam suggest this practice may have negative health effects (32).
REPRODUCTIVE CYCLE Fanihi breed year-round with no apparent seasonal peak. Females bare one pup at a time. Although unknown for fanihi, other fruit bats have a gestation period (pregnancy) of 4.5-6 months, and pups reach maturity between 6-18 months of age. Historically on Guam, the species roosted in large colonies (60-800 bats) made up of harems, bachelor groups, and solitary males. Harems consisted of 1 male to 2-15 females. On Sarigan (CNMI), there are more solitary bats and smaller colonies than on some of the larger islands in the chain (33).
Periods of breeding activity in fanihi(34)