The effects of tooth wear on the activity patterns of free-ranging koalas (Phascolarctos cinereus Goldfuss)

Abstract

The free-ranging activity patterns of five adult males and one sub-adult male koala (Phascolarctos cinereus) with varying degrees of tooth wear were investigated using acoustically sensitive radio-telemetry. Increased tooth wear was found to be associated with a significant decrease in the amount of time spent sleeping and being inactive. Furthermore, compared with individuals with low degrees of tooth wear, individuals with high tooth wear were found to spend considerably less time moving within and between trees, and had home ranges an order of magnitude smaller. Hence, feeding compensations were found to come at the expense of other activities such as sociality and therefore have important consequences for reproductive output. Individuals with high tooth wear also spent longer feeding per bout, and spaced feeding bouts out more evenly throughout a 24-h period, thereby exhibiting reduced degrees of nocturnality. The sub-adult was found to range over a disproportionately large area and spend a relatively large amount of time moving between trees, indicative of a dispersing individual. Moreover, the activity patterns of this individual were found to differ slightly from the adult trends and were perhaps affected by the extra energetic demands associated with dispersal.

Daylight saving time can decrease the frequency of wildlife–vehicle collisions

“…Yet in southeast Queensland, vehicles cause more than 300 koala deaths every year and are one of the greatest causes of their population decline in this area (Australian Department of Sustainability, Environment, Water, Population and Communities). Koalas typically rest during the day and become active during the early evening and throughout the night, when they move from resting to foraging trees [16,17]. They spend only 10% of their time on the ground.…”

The biomechanics of browsing and grazing

“…In koalas (Phascolarctos cinereus), tooth wear increases food particle size in the gut (Lanyon and Sanson, 1986), the number of chews per leaf, and the feeding time (Logan and Sanson, 2002c). The consequences for activity patterns (Logan and Sanson, 2002a) and social behavior (Logan and Sanson, 2002b) can be profound, with older koalas being forced to feed into the day and abandoning attempts to maintain home ranges and social status. As a koala's teeth wear, the modal particle size increases and particle size is critical for the selective retention of fine particles in the caecum where fermentative food breakdown by bacteria takes place (Cork and Sanson, 1991).…”

Faecal particle size and tooth wear of the koala (Phascolarctos cinereus)

“…Logan and Sanson (2002b) found that male koalas with advanced tooth wear spent more time and effort feeding, with a daily increase in the amount of leaves consumed, and an increase in chew rate, chews per leaf, and total number of chews. This means that male koalas invested more time and energy in processing each leaf and spent less time moving between trees, resulting in a decrease in homerange size and sociality.…”

“…The efficiency by which koalas can produce small particles is dictated by tooth wear: animals with worn teeth produce fewer small particles, and such animals may have to depend on strategies such as merycism (rumination-like behaviour) (Logan 2001) or selection of younger leaves to produce small particles. Indeed, the relationship between tooth wear and digestive efficiency is considered so close in koalas that tooth wear is described as the most significant consequence of ageing because it impacts on many life-history attributes such as resource protection and socialisation (Logan and Sanson 2002b). Ultimately, like other herbivores, the decrease in chewing efficiency is accompanied by a decrease in nutritional uptake and loss of body condition until the koala becomes too weak to survive (Lanyon and Sanson 1986).…”

“…The leaf particle sizes in the digestive tract of koalas have been shown to reflect tooth wear, which, in turn, is an index of age and consequently an important parameter in understanding the dynamics and life history of species (Logan and Sanson 2002b). Non-invasive methods of evaluating koala distribution, such as mapping faecal pellet distributions, are important tools for conserving such cryptic species because they produce an unequivocal record of presence with minimal effort Ellis et al 2013).…”