According to the previous observations, certain differences in lizard’s activity during wet and dry season have been noticed. These differences are reflected in enhanced activity of lizards during the wet season, since the resources are more abundant (Koening et al 2012, Leu & Bull 2016). Since the abundance of resources is driven by the environmental factors (mainly temperature, rainfall and humidity), and temperature also affects daily activities of ectotherm animals, lizard´s highest activity is consequently linked with specific temperature values (Huey 1991, Seebacher & Shine 2004). The results of this research suggest that the bluetongues’ activity is confined by the same temperature values in both wet and dry season (around 31°C), showing no obvious difference in their peak activity temperature between the seasons.
We can see that credible intervals in Figure 6 show the highest values for calculated movement parameters while temperatures are far from extremes – not too cold or too warm. Mean values of temperature, during which bluetongues have their activity peak (around 31°C) are the temperatures measured during morning and late afternoon, which suggests that those are the times of the day when lizards are mostly active.
Previous research on related species of sleepy lizards (Tiliqua rugosa) revealed that these animals are quite flexible in adapting to the environmental changes (Koening et al). However, our study does not propose that. Seeing that the peak activity temperatures of bluetongues do not differ between two tropical seasons, it is reasonable to assume that their movements are dependent on specific temperature values, and that they are not able to adjust their peak activity to changes in temperature regimes. Anyhow, the calculated 95% credible intervals for the peak activity temperature were quite wide, which suggests that differences maybe exist, but the analysis failed to reveal it.
According to previously mentioned reports of BOM, the years during which data was collected were years with extreme weather patterns. The rain levels were enormously increased throughout the whole year, causing the humidity and temperature to rise, especially during the dry season. These extreme events caused small variation in weather patterns between two tropical seasons. Decreased variation in seasonal temperature ranges could explain why 95% credible intervals for both measured population parameters did not differ when compared for two seasons.
Despite differences in habitat characteristics between two study sites (Harrison 2009), and temperature differences between the Kununurra area (generally colder) and the Keep River area, calculated 95% credible intervals show no difference between populations inhabiting these two study sites.
As it has been presented in our results, bluetongues seem to have fixed temperatures for their peak activity in both seasons, which does not look good in climate change scenario. Taking into consideration that lizards are mostly active during the “middle” temperature values, shift to lower or higher temperature values could drastically decrease their movements. Study from 2009 by Kearney et al, suggests that cold-blooded terrestrial animals inhabiting tropical areas tend to cool down, not to attain high body temperatures. This means that if the temperature rises in tropical areas, it could be extremely hard for these animals to accommodate their activity patterns in order to avoid overheating.
Responsible for this page: Agneta Johansson
Last updated: 05/19/17