Radio New Zealand - Te Reo Irirangi o Aotearoa

Show notes for Thursday 19 February 2009

On This Programme

An adult female brown tree frog, or whistling frog. Image: Kalinka Rexer-Huber

Frozen frogs

Brown tree frogs, also known as whistling frogs, have a special claim to fame: they are the only vertebrates in the Southern Hemisphere able to completely freeze solid, and survive. University of Otago frog researcher Phil Bishop discovered this ability accidentally, and Master of Science student Kalinka Rexer-Huber is now investigating what temperatures the frogs can tolerate, and how they manage the remarkable trick of freezing and thawing. Pictured on the left is a frozen brown tree frog, whose body temperature is being monitored (image: J Germano).

For more information on this and many more aspects of frog research and conservation visit NZ Frogs.

Rose Thorogood at work with her spectrometer on Tiritiri Matangi Island. Image: Alison Ballance

Baby birds' mouths

Baby birds display brightly coloured mouths as they beg food from their parents. Rose Thorogood, a PhD student at the University of Cambridge, is investigating how mouth colour varies within and between different species of birds in New Zealand. She carries out some of her field work on Tiritiri Matangi Island, and, pictured on the right, is a saddleback, or tieke, chick, showing off its vivid mouth colour (image: Alison Ballance).

Giant kokopu is one of the rarer species that make up part of a whitebait run. Image: Mike Joy, Massey University

Whitebait recruitment

Most New Zealanders are aware of the annual spring migration of swarms of tiny fish known as whitebait. In most river systems, the dominant species is inanga, but a whitebait run is made up of the juveniles of five species of galaxiid fish, including banded kokopu and koaro, and the rarer giant kokopu and shortjaw kokopu (pictured below, image courtesy of Alton Perrie), which are threatened with extinction. The migration marks their return from several months at sea.

Andy Hicks is a PhD student with Gerry Closs at the University of Otago, where he studies the recruitment of whitebait in rivers throughout the country. The group found that not all whitebait species need a marine environment for larval development, but instead remain in freshwater, migrating between rivers and lakes. Using the ear stone, or otilith, Andy Hicks was able to trace the movement of different whitebait species and assess the quality of their habitat.

To find out more about the distribution of large galaxiids (four of the five whitebait species) have a look at research by Mike Joy and his students at Massey University or at NIWA's freshwater fish atlas.

Tuna tagging

Tim Sippel (pictured above, centre, image by Arthur Cozens) is a PhD student working with John Montgomery at the University of Auckland's Leigh Marine Laboratory. He is using satellite tags to study the movements of Pacific bluefin tuna and striped marlin (tracking map below, courtesy of Tim Sippel). This research is carried out co-operatively with Blue Water Marine Research, Stanford University's Tagging of Pacific Pelagics Program and with recreational game fishers.