Rats and flax: traps reveal surprising facts

Dr Marion Donald using a waratah to install the camera posts next to the flax.

Manaaki Whenua senior researcher Dr Manpreet Dhami and NSF postdoctoral Fellow Dr Marion Donald, both from our Biocontrol and Molecular Ecology team were working to understand more about bird pollination of nectar in flowers, as well as the fascinating workings of microorganisms in nectar, when they made a surprise discovery.

For this study, recently published in the New Zealand Journal of Ecology, the team used seven camera traps to monitor vertebrate visitation to mountain flax (wharariki, Phormium cookianum) in a small, restored wetland area that borders a residential neighborhood in Lincoln. The camera traps were programmed to be motion activated and either take bursts of photos or short videos.

“Over the nine-day study, we photographed and video recorded a ship rat climbing across mountain flax flowers and feeding on mountain flax nectar on six different nights – which was a surprising finding,” says Manpreet.

In New Zealand, the ship rat (Rattus rattus) is considered at fault for the rapid declines of many bird populations.

“While seed masts have been associated in rat population booms, we think that alternative food resources, like floral nectar, may play a role in rat-bird interactions,” says Manpreet.

“This footage also indicates possible pollination services by rats, which opens other research questions.”

These findings suggest that attention should be paid to nectar as a limited resource that may support rat populations, as well as attract rats for pollination services. “This increased resource competition with birds could have important consequences,” says Marion.

Nocturnal consumption by rats may deplete the limited nectar resource on which the nectar-feeding birds rely.

These scientists write “studies tracking the amount of floral nectar removed during the night compared to the amount removed during the day would help determine whether rat consumption reduces nectar availability for diurnal birds.”

Interestingly during this study the rats did not damage the flax flowers while drinking the nectar, Marion says.

“As rats have a near global distribution we think their role as resource competitors and pollinators may be widespread, so we’re excited to explore this further.”