Science round-up

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The whitebait frenzy is now in full swing and passionate New Zea­landers are donning their waders at the crack of dawn and heading for various rivers in pursuit of the some­times elusive delicacy. However, if Daphne Lee from Otago University’s geology department invites you for lunch, you might think twice about tackling one of her whitebait patties.

Whitebait is the name given to the juvenile form of up to six spe­cies of native fish from the family Galaxidae. Galaxiids are diadro­mous, meaning they have both a freshwater and marine phase to their life-cycle. It is the return of the ju­venile fish from the oceans to their freshwater maturation grounds that gets fisherman so excited. However, Lee and coauthors McDowall and Lindqvist (published in the Journal of the Royal Society, freely available from­lish/jrsnz/2007/009.php) are more excited by the inland dusty bowls of central Otago, where whitebait heavily sandwiched between layers of rock can be caught a mere 23 million years past their best-by date. Otago’s Miocene lake deposits have proved fruitful for Lee, who reports on the recovery of the world’s earliest galaxiid fossils. Three fos­sil species from three different lake environments have been recovered and provide concrete proof of spe­cies diversity and abundance in the region between 10 and 23 million years ago.


Ever had that lost feeling, unable to find your way home after a long night out because you strayed into an unfamiliar part of town? Well, that’s how a few LONG-TAILED BATS must have felt when they were translocated from their home at the Grand Canyon cave in Waikato. Homing instincts are well-studied in domesticated pigeons and have been observed in some overseas species of bat at distances of over 500 km. However, here we know little about the potential homing response of our native bats. Josh Guilbert, a PhD student from Auckland University has been experimenting on bat homing behaviour using small radio transmit­ters. Translocating nine long-tailed bats up to 20 km from their home reference point, he found that eight of the nine returned safely, most of them on the following day. His work, published in the New Zealand Journal of Zoology (­lish/nzjz/2007/025.php) is important as an ability to locate “home” has significant implications for conserva­tion management of these secretive nocturnal mammals.


New Zealand’s flora has an unusual combination of plants but, as is well-known, this diversity is under threat from human activities and inva­sive exotic species. Many community groups are trying to reverse the de­cline in native plants and numerous revegetation projects are underway throughout the country, from back­yard to landscape scale. However, native plants can be somewhat fussy when it comes to growing them from seeds, and germination and subsequent establishment can be difficult, especially on large areas. While we know that many New Zealand seeds are viable for comparatively short periods, research into the germination requirements of native seeds is a te­dious and painstaking process.

Jacqueline Rowarth and co-authors in the New Zealand Journal of Bota­ny have recently compiled a review of the last two decades of research on seed germination requirements. Although possibly a little complex for some, it is an authoritative refer­ence that includes limitations to seed set, germination patterns, dormancy and how to break it, and seedbanks. Further information on any subject can be reached via the paper’s com­prehensive reference list.


In December 2004 a breath of fresh air blew through New Zealand’s pubs and clubs as the Smoke Free Environments Amendment Act 2003 came into full force. At the time, controversy raged over the benefits to bar staff versus the loss of income to bar owners. Publicans were fore­casting doom and gloom as many smokers vowed to boycott their premises.

Several years have now passed and most people seem to have settled down. Bars remain vibrant. But has the legislation worked, or are we now just exposed to less SEC­OND-HAND SMOKE?  Dinusha Fernando and co-authors from ESR (a crown research institute) found that anti-smoking legislation has resulted in a 90 per cent reduction in the level of cotinine in the saliva of bar patrons.

Cotinine is the main metabolite of nicotine and is a well recognised marker of sec­ond-hand smoke. Levels of cotinine in the saliva of bar patrons prior to anti-smoking legislation were highly correlated with smokiness of bars. The authors conclude that the law change has significantly protected patrons’ health, although exposure to second hand smoke has not been totally eliminated. Smoke drifting in from designated outdoor smoking areas is the likely culprit.


The ability to construct and effective­ly use tools is comparatively rare in animals. However, METATOOLING, or the ability to use one tool on another, is even rarer. Humans can do this, as can our close relatives the apes, although monkeys struggle with this task. Probably the most un­usual metatool animal in the world is the New Caledonian crow, the subject of many research projects to investigate its tool-making abilities. Alex Taylor from Auckland Univer­sity reports in a Marsden-funded research paper published in Current Biology that New Caledonian crows not only have the ability to make and use tools, they possess an advanced level of physical cognition that ap­pears to be based on analogical reasoning rather than trial-

and-error learning. Taylor’s experi­ments showed that New Caledonian crows could spontaneously solve a metatool task in which a short tool was required to retrieve a longer tool that could then be used to obtain a reward of food. Check out the video clips and images on http://language.


New Zealanders have played a prom­inent role in the development of pest control techniques that utilise insect semio-chemical attractants, oth­erwise known as PHEROMONES. Control approaches such as mating disruption, lure-and-infect and at­tracticides have been trialled on a number of species. Sex pheromones are used to entice unsuspecting in­sects to doses of pathogens or insec­ticides or into other situations which interfere with mating.

A prime example of mating disrup­tion is those twisty ties one can buy to prevent codling moths from attack­ing apples. However, Max Suckling from HortResearch has taken the use of insect pheromones to a new level by introducing a novel multiple-spe­cies interference system or ménage­a-trois for insects, described in a re­cently published article in the Journal of Chemical Ecology.

The concept is simple, but inge­nious. Take two species with differing sex pheromones and spray species A with a powerfully attractive odorant derived from species B. The odorant will interfere with the mating system of one or both of the species.

During controlled wind tunnel experiments, Suckling and his col­leagues found that males spent long periods of time physically chasing and disrupting the behaviour of males from another species sprayed with attractive odorants. So does much time spent chasing a chemical transvestite actually influence insect breeding success?

Large caged field trials conducted in Hawaii showed a marked reduc­tion in mating success of oriental fruit flies and melon flies when the chemical confusion was employed compared to control situations. However, in small cage experiments insect breeding success was unaf­fected. The concept is relatively new and much further testing is required, however in time it may prove to be a successful addition to the array of pheromone-mediated insect pest control techniques.


Border biosecurity has a high profile with both the government and public these days. Preventing exotic species from reaching New Zealand is critical to the safety of our native plants and animals. Many nas­ty species are already here, like the Argentine ant that threatens native insect communities. Analysing what is here can help prevent further es­tablishments of unwanted organisms by identifying introduction pathways.

Steve Corin and co-authors from Victoria University have been using molecular techniques to try to iden­tify the route by which we received Argentine ants in the early 1990s. By comparing cytochrome b mito­chondrial DNA sequences, Corin discovered that all New Zealand Argentine ant colonies derive from a single overseas source population. The genetic signature of this popu­lation matches a population from Bundoora in Victoria, Australia and a population in the ants’ native range, Ocampo, Argentina.

Based on the frequency of Ar­gentine ant interceptions at New Zealand ports—Australia 38 per cent and Argentina 0 per cent—Corin has concluded that our free-trade partners from across the Tasman are the most likely source of our Argen­tine ants. This study highlights the need for extra vigilance to ensure additional invasive ant species don’t manage to sneak in.

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