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with Alison Ballance & Veronika Meduna
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An adult female brown tree frog, or whistling frog. Image: Kalinka Rexer-Huber
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 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
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.
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.
Not all audio is available due to copyright restrictions.
Introduced brown tree frogs can survive being frozen solid, and Kalinka Rexer-Huber and Phil Bishop are finding out how. (13′42″)
Rose Thorogood is investigating the idea that the colour inside a baby bird's mouth tells the parents how healthy the chick is (12′30″)
Fish ecologist Andy Hicks studies whitebait life cycles and their recruitment in river systems (12′03″)
Tim Sippel is attaching satellite tags to striped marlin and Pacific bluefin tuna to find out where they travel to (12′47″)
Produced and presented by Veronika Meduna, Ruth Beran & Alison Ballance
Each week Our Changing World features an eclectic mix of sound-rich stories about science, the environment and medical research, recorded around New Zealand in labs and in the field.
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