Kangaroo Teeth: A Lifelong Growth and Indicators of Age and Sex

Kangaroo Teeth: A Lifelong Growth and Indicators of Age and Sex

A recent study published in the Archives of Oral Biology has revealed that the age and gender of Australian marsupials, such as kangaroos, can be determined through their teeth. This information is crucial for veterinarians, ecologists, and conservationists in assessing wildlife welfare and population health.

The majority of Australia’s marsupials belong to a group called Diprotodontia, which have large, straight incisor teeth in their lower jaws. Kangaroos, wallabies, koalas, wombats, and possums are all examples of diprotodontian marsupials. The study focused on measuring the growth of incisor teeth in kangaroos and honey possums, and found that these teeth continue to grow throughout their lives. This continuous growth can be used to accurately determine the age of marsupials.

Similar to tree rings, teeth have growth lines that form as different hard tissues (enamel, dentine, and cementum) are added over time. The study examined growth lines in kangaroo incisor teeth and discovered that yearly growth lines can be observed in two different regions of these teeth.

Another interesting method used to determine the age of kangaroos is by measuring the movement of their molars. Kangaroos have a unique adaptation where their molar teeth gradually move forward in their jaws due to the rapid wear caused by eating grass. Old, worn teeth are pushed forward and eventually fall out to make way for new, unworn teeth that are more efficient at chewing. This process continues until the oldest kangaroos have only a few teeth left. Scientists have measured the rate at which molar progression occurs and found that it corresponds accurately with age.

The study also examined differences in incisor teeth between male and female kangaroos. It was discovered that incisors belonging to male kangaroos tend to grow faster and wear down more quickly than those of females. This information is valuable for understanding animal ecology and the different foraging and feeding behaviors of males and females in the wild.

In addition to providing insights into the age and gender of modern kangaroos, these new methods can also be applied to ancient kangaroo species. Thousands of years ago, Australia was home to a variety of giant kangaroos, some of which weighed up to 250 kilograms. Determining the age and gender of fossils from these extinct species can be challenging, but the study’s findings offer hope that incisors can provide valuable information about their lives.

Overall, this research highlights the importance of teeth in understanding the age, gender, feeding behaviors, and evolution of marsupials. By studying teeth, scientists can gain valuable insights into the lives of both modern and ancient kangaroos.