Mariana Fruit Bat/Flying Fox/Fanihi - Nolan McWhorter

Mariana Flying Fox
(Pteropus mariannus mariannus)

By: Nolan McWhorter 

U.S. Air Force photo by Staff Sgt. Melissa B. White

Description and Ecology

Appearance: The Mariana Fruit Bat, or Flying Fox as some call it, is a dark brown, grey, and black bat that has an average length of 0.2 meters,  an average wingspan of almost 1 meter, and an average weight of 0.5kg. On the neck, some of the Flying Foxes have bright gold, yet some individuals just have a pale brown region. As far as the color of the head, it varies from brown to black. The males are slightly larger than the females.

Habitat:  Mariana Fruit bats are found within the tropical areas of Guam and the surrounding islands. The bats tend to roost in limestone forests, coconut groves, strand vegetation, and other plant vegetation. In the past, the bats have inhabited farms and savannas and a few urban type settings, but as the numbers have dwindled, these habitats are mostly deserted.

Behavior:  The Mariana Fruit bat spends most of it’s time sleeping during the day, and then during the evening hours it goes to forage for materials or food. Sometimes during the day, the bats defend their territory, groom, breed, and fly.

Diet:  Typically, the Mariana Fruit Bat primarily eats fruits such as breadfruit, papaya, fading, figs, kafu, talisai, and a select few flowers. On occasion, the bat feasts on plant material.

Geographic and Population Changes

Although data may be somewhat limited, with surveys conducted in 1983 and 2000, there has been a conservative estimate that puts the number of fruit bats to be down 40% from the 9,000 there was in 1983 according to the Fish and Wildlife Service. In particular, most of the decline is measured in 2 of the 3 largest islands that the bats inhabit near Guam: Anataham and Pagan. Along with this, it is said that while there is some travel for the bats in between the islands around Guam, there are no inhabitable areas on some of the island stops. Even when the islands that do have sustainable areas, they are very fragmented, resulting in isolated populations according to redlist.com.

   “Draft Revised Recovery Plan for the Mariana Fruit Bat or Fanihi.” U.S. Fish & Wildlife Service, Nov. 9.

Listing Date and Type of Listing

• 1996 – Endangered (EN)
• 1994 – Vulnerable (V)
• 1990 – Endangered (E)
• 1988 – Vulnerable (V)
• 1986 – Vulnerable (V)

“Pteropus Mariannus.” Red List, 2008, www.iucnredlist.org/details/18737/0.

 Mariana fruit bat - Photo credit Dave Worthingtonl/USFWS

Cause of listing and Main threats to its continued existence

There are currently 4 main reasons for the cause of each listing throughout the years for the Mariana Fruit Bat according to the U.S. Fish and Wildlife Service. From most important to least important, we start at habitat loss and degradation. Of the factors that cause this habitat loss are primarily development of infrastructure, invasive non-native plants, and invasive non-native animals. Of the animals, Brown treesnakes themselves are one of the main reasons for the drop-in numbers, since the snakes prey on the bat’s young. Moving from this predator, we also need to assess the illegal hunting that goes on inside the islands. Since the locals can remember, Mariana Fruit Bat dishes have been a cultural tradition, making it a target even though it is already illegal to hunt them. Even if the locals do not eat them, some locals kill them for consuming fruit crops. To make matters worse, the regulations are not properly enforced, especially in archipelago, so it is as if there were no regulations. Lastly, we land on the development and procedure of Military activities. It is said that these military activities have offset the bats’ normal biological routine, and in return has dropped the productivity of the species to reproduce. 

Description of Recovery Plan

If the following criteria is met by the year 2030, then we could see a major recovery resulting in the delisting of the species. According to the U.S. Fish and Wildlife Service, here are the official recovery actions:

1.    Immediate management to reduce risks and stabilize the existing population.

**(To meet this criterion, we propose that stable or increasing fanihi subpopulations should be distributed to at least three of the five southern islands, as well as 6 of the 8 northern islands, with two of the northern islands must at least be the two largest ones)

2. Specific actions to reduce or eliminate illegal hunting to allow increase in

fanihi numbers throughout the archipelago.

3. Protection of the best existing habitat and enhancement of additional suitable

habitat.

4. Effective control and interdiction of the brown treesnake.

5. Research to address gaps in our knowledge of fanihi life history and ecology

and improve our ability to model the population, assess its sensitivity to

specific threats and management actions, and forecast its persistence…

“Draft Revised Recovery Plan for the Mariana Fruit Bat or Fanihi.” U.S. Fish & Wildlife Service, Nov. 9, Page X.

Photo By: Merlin D. Tuttle

What can You do?

According to batcon.org, their bat conservation international group that accepts donations that “supports our efforts to protect bats, their habitat, and to educate the public on the importance of bats”. Among the listed donations, they also offer a service in which you could look up your employer, and if they are part of gift matching program, you can double your donation!

Donate Here!

 https://www.batcon.org/index.phpoption=com_content&view=article&layout=edit&id=1056

Other Resources

https://www.fws.gov/pacificislands/fauna/marianabat.html

http://www.andersen.af.mil/News/Features/Article/414704/save-the-fruit-bats-andersen-continues-conservation-effort/

https://ecos.fws.gov/docs/recovery_plan/100330.pdf

https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=A07X

http://www.iucnredlist.org/details/18737/0

http://animaldiversity.org/accounts/Pteropus_mariannus/