Keeping count of our species
Just how bad is the plight of native frogs? How are kakapo or tuatara doing?
A Victoria University professor has used statistical techniques to estimate numbers in animal populations, providing accurate data that are essential to conservation efforts.
Professor Shirley Pledger, an international expert in this area, will explore how statistics has helped conservation in her inaugural professorial lecture at Victoria University next Tuesday.
Her research has built on the ‘capture-recapture’ method used by scientists.
“Capture-recapture is a technique that provides accurate estimates of animals, including any that remain hidden,” says Professor Pledger. “It gives us data so we know what we’re dealing with. For instance, do we need to concentrate more on removing predators? Where are numbers strong?”
Using the technique, scientists capture a sample of animals, mark them then release them. Later they capture another sample and use the proportion of marked animals that are recaptured to estimate the total animal population.
Professor Pledger’s research has focused on improving the capture-recapture method, trying different models to accurately estimate the numbers of animals.
“Some animals are bold, some shy, some move around. Scientists either surveyed ‘closed’ populations, which is a kind of snapshot, or ‘open’ populations over a length of time that saw births, deaths and migrations. The outstanding problem for 20 years or so was that most surveys typically underestimated population sizes—now that’s much less of an issue.”
As well as working with biologists at Victoria and other institutions in New Zealand, Professor Pledger has strong international connections.
Her statistical work forms part of a US computer package for surveying animal populations.
Vice-Chancellor Professor Pat Walsh says Victoria’s inaugural lecture series is an opportunity for professors to provide family, friends, colleagues and the wider community with an insight into their specialist area of study.
“It is also an opportunity for the University to celebrate and acknowledge our valued professors,” says Professor Walsh.
‘How many animals are in the area? When counting doesn’t work’Tuesday 21 June,
6pm Hunter Council Chamber,
Level 2, Hunter Building
Victoria University, Kelburn