Adaptations of Mammals to Arid Australian Environments :: Environment Australia Animals Essays

Adaptations of Mammals to Arid Australian Environments Abstract High temperatures and low rainfall characterize much of Australia. It is hard to believe that animals can survive in arid conditions, much less prosper. Yet there is a whole range of mammals, among other life forms, that do. These animals survive because they have adaptations that allow them to live in the hot, dry conditions. The function of the adaptations is to balance thermoregulation with water gain and loss. For instance, many mammals that live in the desert obtain much or all of their water from the food they consume. The reduced water intake is partially balanced through concentrated urine and dry faeces. Evaporative cooling helps to regulate temperature. To limit the water lost through evaporative cooling, mammals are nocturnal, have light coloration and other body features to help dissipate heat, and use microenvironments to reduce heat gain. This is only a short list of the many amazing adaptations Australian mammals have to survive the harsh arid conditions; howe ver, it serves to illustrate the balance between thermoregulation and water regulation. Introduction Seventy percent of Australia is considered arid or semi-arid (Climate averages, 2000). Arid regions are characterized by receiving 100-250 millimeters of rain a year, and semi-arid regions are characterized by receiving 250-500 mm of rain per year (Costa, 1995). The average rainfall in Australia is only 165 mm per year (Climate averages, 2002). Not only are these regions faced with sparse rainfall, but they are also confronted with extreme temperatures. During the summer months of January and February, temperatures regularly exceed 40Â °C in the arid regions (Climate averages, 2002). The temperatures are even more scorching for small animals that live close to the ground because the soil becomes much hotter than the air (Walsberg, 2000). Therefore, Australian mammals must have adaptations to cope with the heat and lack of available water. Additionally, they must have adaptations to balance thermoregulation with water regulation. This paper will address these adaptations and explain how they work. Homeothermy Mammals can be broadly classified as homeotherms, which means their body temperature is relatively independent of the external environmental temperature (Ricklefs, 2001). Mammals and birds keep their body temperatures between 37Â °C and 38Â °C, however there are exceptions (Walsberg, 2000). Maintaining a constant internal temperature requires animals to have mechanisms to regulate their body temperature.