Peterson Creek: the Platypus Place
By: Caroline Confort, Mackenzie Smith, Danielle Post
Have you ever heard of mammals that lay eggs? They are called monotremes and there are only three species of these animals left in the world today. The best known of these three species is the platypus, found only in Australia. With webbed front feet, and a duck-like bill these animals have dark colored fur that is denser than a polar bear’s! Platypus are mostly nocturnal, sleeping in burrows during the day and swimming and foraging in the water at night. When they forage, they close their eyes, ears and nose relying only on their bill which has receptors to detect minute electrical signals from their prey. Typically they eat aquatic invertebrates and occasionally small fish and frogs. These characteristics make them well suited for their habitat of river banks and lake sides.
Unfortunately, natural predators are not the only threat to these monotremes. While they are considered to be common in Australia, platypus habitat is extremely vulnerable to human activity. Water pollution, river damming, and live stock grazing continue to pose serious threats to habitat. More specifically, live stock grazing causes run-off of fertilizers and animal feces into platypus habitat. The addition of these substances into the water can cause nutrient levels to rise disturbing to the natural ecosystem. However there is increasing evidence indicating that this rise in nutrient levels is not always detrimental to the platypus. This moderate increase supplies an excess of food for the invertebrates that platypus prey on, creating a steady and reliable food source. Certain fishing methods including yabbie (freshwater crayfish) traps have also affected populations in the past. Land clearing and bank erosion decrease vegetation within their habitats; a substantial amount of vegetation is necessary for the platypus to line its burrow to protect its eggs from flooding and predators. In addition, surrounding vegetation provides shade, cooler, well oxygenated water, increases prey populations, and creates burrowing opportunities within its roots.
Peterson Creek is a well known platypus habitat near the town of Yunguburra in the Atherton Tablelands of northeast Queensland, Australia. Though cleared for farming and agriculture in the early 1900’s, more recently a restoration project of the site began in 1998. Today the natural ecosystem as a whole is recovering successfully and its trails are frequented by hikers, runners, and platypus enthusiasts.
In order to assess platypus populations in Peterson Creek, we conducted a visual monitoring survey. Our group of 19 students with synchronized watches recorded any platypus sightings in a continuous portion of the creek that stretched 814 meters. The study took place over a period of 3 days for 4 hours total. 3 hours of data were collected in the early evening and 1 hour of data was collected in the early morning. For each platypus sighting we recorded the time of day, time spent above and below the waters surface, and direction the animal was traveling. This information is important because time spent under water usually means the platypus is foraging and dive times can be an indicator of ecosystem health. All data collected were also pooled and analyzed to determine the minimum number of individual animals seen.
In a study done by Milione and Harding, it was determined that relatively shallow, slow moving, water is preferred habitat for platypus. The sections of Peterson creek observed in our study consisted almost entirely of this ideal platypus habitat. By comparing data on the time of sightings and the direction each platypus was headed, we conservatively estimated the minimum number of platypus in the sample section of the creek to be 5 individuals. In a study done by Kruck it was determined that decreased dive time relates to high foraging success. A small ratio of time underwater to time on the surface indicates high prey density. In the study it was found that there was higher insect levels in the streams that experienced agricultural runoff, and these sites found platypus dive times to be the lowest. Our study found the average ratio of time spent underwater to time on the surface to be 4.49. This ratio is relatively low, indicating that platypus in Peterson Creek do not have much difficulty finding prey when foraging.
Our study demonstrates that Peterson Creek is a suitable habitat for platypus populations to thrive. As more studies are being done, more evidence is appearing that platypus are increasingly inhabiting areas that are affected by farming and urban runoff as compared to areas of natural undisturbed vegetation. This may be caused by increased sediment and nutrient runoff that increases food resources for the platypus in streams and lakes. More studies must be done to determine if there are any negative effects of high runoff levels, but for now the platypus are safe and will remain an Australian icon for years to come.