Though 63% of the island is a nature reserve, development could still harm flying fox populations.
For example, the construction of a casino and possible losses to specific food resources is implicated in the abandonment of the Ethel Beach colony.

Several invasive species have been introduced to Christmas Island, including the barking gecko, Oriental wolf snake, African giant snail, black rat, feral cat, yellow crazy ants, Tanzanian blue ringleg centipede.
The last three are especially implicated in harming flying foxes.
However, though feral cats are known to consume the flying fox, there is no evidence they are actively hunting native wildlife; the yellow crazy ant, which sprays noxious formic acid, has formed destructive supercolonies, but it does not seem to affect roosting behaviour too much, indicating either minimal disturbance or maladaptive tolerance due to island tameness.
Nonetheless, ant supercolonies have been aerially bombed with the toxic insecticide Fipronil (but it has unknown effects on the flying fox) and these invasive species have the potential to negatively impact the ecosystem via outcompetition, overpredation, or acting as disease vectors.

Strong gale-force winds sweeping the island on 27 March 1988 coincided with the estimated start of population decline around 1988, and it was proposed that this destroyed colonies overnight and swept some bats off to sea.
This is highly unlikely, though it no doubt harmed the flying fox population.

Phosphate mining sends dust into the vicinity, which may contain traces of cadmium and suppress plant growth.
Ingestion of sufficient quantity, possibly through licking off the dust while grooming or consuming dust-covered food, can lead to cadmium poisoning and liver problems.
One roost near a phosphate drier was abandoned, and one Christmas Island flying fox liver was found to contain 0.69 mg/kg cadmium, which is higher than the 0.06–0.48 mg observed in various lab and wild animals, but lower than the toxic threshold, though even trace amounts can be harmful.
The Daniel Roux Cave colony was likely abandoned due to phosphate mining activity.
Though 63% of the island is a nature reserve, development could still harm flying fox populations. For example, the construction of a casino and possible losses to specific food resources is implicated in the abandonment of the Ethel Beach colony.
Several invasive species have been introduced to Christmas Island, including the barking gecko, Oriental wolf snake, African giant snail, black rat, feral cat, yellow crazy ants, Tanzanian blue ringleg centipede. The last three are especially implicated in harming flying foxes. However, though feral cats are known to consume the flying fox, there is no evidence they are actively hunting native wildlife; the yellow crazy ant, which sprays noxious formic acid, has formed destructive supercolonies, but it does not seem to affect roosting behaviour too much, indicating either minimal disturbance or maladaptive tolerance due to island tameness. Nonetheless, ant supercolonies have been aerially bombed with the toxic insecticide Fipronil (but it has unknown effects on the flying fox) and these invasive species have the potential to negatively impact the ecosystem via outcompetition, overpredation, or acting as disease vectors.
Strong gale-force winds sweeping the island on 27 March 1988 coincided with the estimated start of population decline around 1988, and it was proposed that this destroyed colonies overnight and swept some bats off to sea. This is highly unlikely, though it no doubt harmed the flying fox population.
Phosphate mining sends dust into the vicinity, which may contain traces of cadmium and suppress plant growth. Ingestion of sufficient quantity, possibly through licking off the dust while grooming or consuming dust-covered food, can lead to cadmium poisoning and liver problems. One roost near a phosphate drier was abandoned, and one Christmas Island flying fox liver was found to contain 0.69 mg/kg cadmium, which is higher than the 0.06–0.48 mg observed in various lab and wild animals, but lower than the toxic threshold, though even trace amounts can be harmful. The Daniel Roux Cave colony was likely abandoned due to phosphate mining activity.
Christmas Island flying fox