Limited survey likely undercounted fanihi population; volunteers sought for annual bat count

The 269 fanihi counted during the first-ever simultaneous survey of Guam, Saipan, and Tinian likely represent only a fraction of the Marianas fruit bat population, according to wildlife officials, who are calling for more community volunteers to improve coverage during the annual count each April.

Officials said the survey's results should be viewed cautiously because the count was based on a specific methodology and limited observer coverage, meaning more bats may have been present than were detected. Additional volunteers would allow survey teams to staff more observation stations and improve detection rates.

A second major limitation was the exclusion of Rota, which was not included because of logistical and staffing constraints. Yet wildlife officials estimate the island alone supports roughly 1,100 fanihi based on monthly colony counts, far exceeding the number recorded during the April survey on Guam, Saipan, and Tinian combined.

The survey, conducted last April, recorded 241 bats on Guam, 24 on Saipan, and four on Tinian. It marked the first coordinated count undertaken simultaneously across the jurisdictions.

Jill Liske-Clark, a natural resources specialist with Naval Facilities Engineering Systems Command Marianas, said the survey establishes a baseline for future monitoring.

“This is the first year that we have done a simultaneous count with Guam, Saipan, and Tinian, so we don't really have a basis for comparison with previous years,” she said. “This is how we plan to do it going forward in coordination with our Guam partners, and so we'll be able to learn more about the trajectory of fanihi through these simultaneous counts.”

Henry Fandel, wildlife section supervisor with the CNMI Division of Fish and Wildlife, stressed that the count should not be interpreted as a total population estimate.

“The 269 is not necessarily the number that represents how many bats there are,” Fandel said. “It's based specifically on that survey methodology and the effort put into it and should be interpreted in the context of that survey.”

To illustrate the point, Fandel noted that separate monthly colony surveys on Rota routinely record about 1,100 bats.

“On Rota alone during a separate survey conducted by DFW at colonies, we record on average 1,100 bats every month on the island,” he said.

Asked why Rota was omitted from the April count, Fandel cited capacity challenges.

“It is largely due to CNMI Division of Fish and Wildlife's capacity to organize and conduct the count on Rota and the time when it was scheduled,” he said. “Eventually, we would like to build capacity within our Rota office to organize and conduct the count across Guam, Rota, Saipan, and Tinian.”

Officials said volunteer participation is critical because more observers allow for greater island coverage and more reliable data.

“The more participants we have, the more stations we're able to have observers at the same time,” Fandel said. “The better coverage, the better detection, the more value we get from the survey if we have more participation.”

Liske-Clark said the annual survey also provides an opportunity for residents to contribute directly to wildlife conservation efforts.

“I think it's really important that this survey specifically is an opportunity for the community to participate in wildlife science, in becoming more closely familiar with really important, culturally important wildlife,” she said. “We're going to continue to advertise this specific survey annually as an opportunity for the community to jump on board.”

The agencies plan to continue conducting the coordinated count every April and are encouraging residents to participate in future surveys.