April 16, 2013

Peer Review: Students Study Platypus Populations

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The platypus is one of the most unique mammals on this planet and can only be found in eastern Australia. Even if you look in the right places, chances are, you might not get to see one. However,  Heather Delanty ’14 and Shira Ellenson ’14 saw at least five when they spent a week in Yungaburra, Queensland, conducting a population density research study on platypus.

They also wrote a popular science article to wrap up the project, with two other study abroad students, Gene Fukui ’14, Oberlin College, and Patrick Mershon ’14, Kenyon College. They are all studying abroad for the semester with the School of International Training, which has a rainforest, reef and cultural ecology program located in Australia.

The unique characteristics of platypus make them excellent species for studying evolution. Aside from their physical idiosyncrasies which include a duck-like bill, otter-like fur, a beaver-like tail, retractable webbing between toes, and venomous spurs in males, platypus have many other distinctive features.

Platypus belong to the order monotremes, defined as being a mammal that lays eggs. Genetically, they also have ten different sex chromosomes which are not fully understood, and their genome contains both mammalian and reptilian components.

Platypus are elusive animals which spend most of their time diving underwater searching for food. According to the SIT research group, however, when they dive to search for small invertebrates their eyes, nostrils, and ears close, so they must rely on another sense. Platypus hunt using electroreception – they are receptive of electric current, which is generated by nerves and muscle contractions in a living animal. Platypus also have pressure sensors to receive changes in pressure waves caused by movement, which, combined with their electric sense, allows them determine the distance to their prey.

The platypus does surface for air and to eat and digest its prey. This is when the students were able to see the mammals and note travel direction and record surface and dive times. 20 students were stationed in pairs along Peterson Creek equipped with synchronized watches ready to conduct a visual survey over a span of 810 meters. They recorded sightings four times throughout the week for an hour each time, three evening times, and one in the morning.

After data was compiled, the students made a conservative estimate that at least five individual platypus inhabit the creek. They also found that the platypus remained underwater for about 73 percent of the time with an average surface time of 10 seconds and an average dive time of 35 seconds.

The purpose of this week long study was to gather baseline information about the habitat quality and platypus population of Peterson Creek. Shorter dive times are indicative of a quality habitat because the platypus does not have to spend as much time searching for food, Delanty said. The area around Peterson Creek used to be farmland, and the area has recently been reforested in a community effort to restore the natural ecosystem. Previously, there had been almost no platypus habitat research in this area.

According to their paper, “The relatively short dive intervals found in this survey suggests that Peterson Creek remains a high quality habitat for platypus despite its moderate level of human disturbance.”

Based on scientific readings, Delanty said that platypus prefer creeks at least four meters wide and between 0.5 and 2 meters deep. Platypus also prefer slow moving pools over fast moving shallow waters. Peterson Creek was observed to be a good fit within these parameters.

The community effort to restore vegetation to the rural creek has been an important factor for the platypus population in Peterson Creek. The area is also unique in that agriculture effects such as “runoff from high fertilization have artificially elevated nutrient pools in these ecosystems, causing high productivity of certain prey species at the expense of overall system diversity. Higher prey densities tend to favor larger numbers of platypus in these areas,” Fukui said.

Human activity generally has a negative impact on the quality of the habitat. Many tourists also go to the viewing platform to see the platypus.

Fukui commented that additional morning surveys should have been done to get a better count, as there would have been less tourist traffic.

Original Author: Lisa Gibson