Science Centres: Aquatic Biodiversity and Biosecurity

It might look cute, but the common mouse, Mus musculus, has been unmasked as a predator of whitebait eggs.

For the past two whitebait seasons, NIWA scientists have set up video cameras amongst intertidal vegetation where the most common whitebait species, inanga (Galaxias maculatus), lay their eggs, in an attempt to determine what is preying on the eggs. Previous studies have estimated that up to 80% of the eggs are removed between the time they are laid and the time they are washed out to sea (roughly one lunar month).

Last year, an intertidal mud crab (Helice crassa) ate all the eggs at one of the two sites studied. This year, two more sites were monitored. The video footage this season snapped a mouse repeatedly returning to the area and devouring all the eggs at both sites.

It’s too soon to say whether mice are a major predator of inanga eggs, but thanks to further funding from the Foundation for Research, Science & Technology the monitoring is set to continue next season. Mice be warned: we will be watching you.