Christmas Island Flying-fox (Pteropus melanotis natalis) Monitoring 

Nocturnal drive-by monitoring survey design: A large set (124) of sites are spaced evenly across the entire extent of Christmas Island, mostly located alongside roads or tracks. Sites are generally spaced between 0.5 and 1km apart with their overall distribution being reasonably representative of the environmental variation across the Island. All sites are sampled at night on four separate occasions over a short sampling period (the mid-dry season of June-July). At each site an observer records whether bats were present or absent (either seen or heard) and the sampling provides an incidence index varying from 0 to 4 (i.e. recorded on each of the four visits) for each site. Nocturnal drive-by surveys were first conducted in 2006, and from 2012 onwards have been conducted once a year. 

Nocturnal drive-by monitoring: Sites, mostly located alongside roads or tracks, are visited and observations are made from near the parked vehicle. Survey observations are 10 minutes in duration with the start time of each survey being noted. If a flying-fox is seen or heard, the time from the start of the survey is recorded along with the distance from the observer and the number of flying-foxes present in a group. Any subsequent flying-fox activity within the 10 minute period is recorded in the same way. Additional information regarding the presence and abundance of other species of interest Ninox natalis (Christmas Island Hawk Owl), Crytodactylus sadleiri (giant gecko), Scolopendra morsitans (giant centipede), Lycodon aulicus capucinus (wolf snake), and Hemidactylus frenatus (barking gecko) is also recorded for other studies/monitoring programs. 

Sampling design: Repeated Measures Systematic Sampling 

Measurements: Raw Observations Raw Observations - Count Data 

Measurement Attributes: Incidence Population Size Presence/Absence 

Ground & Exit monitoring survey design : An existing set of known roost sites are visited to conduct visual ground counts of individual bats in trees during the day, after which locations above these sites are visited to count bats exiting from the respective roost sites. These counts are unlikely to provide robust overall population estimates but serve to provide minimum population measures. Although total abundance cannot be extrapolated from these counts, patterns in the data can suggest population trends. Ground and exit monitoring was first conducted in 2004, and surveys are undertaken quarterly. 

Method Drift Description: The number of sites has varied over the years as some camps are no longer used. Currently there are four active camps: Hosnies Spring, McMicken Point, Ethel Beach and the Golf Course. 

Ground and exit monitoring: At the known roost sites, 24 observers undertake ground counts. Using a GPS and map all known (and numbered) roost trees are located, and the number of individual flying foxes in each tree are recorded. If flying foxes are found roosting in new trees, these trees are physically marked using a numbered cattle tag and flagging tape and the coordinates of the location are recorded. For exit monitoring, at least 2 observers visit existing vantage/viewpoints overlooking the ground count roost sites and count individual flying foxes as they leave the roost. Observers alternate every 15 minutes to count, from 3:00pm to 6:15pm, recording an overall exit total. General weather data is also recorded.