Biology 102 Lab. Irem Yucel
2217065
Diversity of Life Report
The Koalas
General Information
The koala is a species (Phascolarctos cinerus) living natively in Australia. It is mammalian, it lives on trees (arboreal) and it is herbivorous. It belongs to mersupial infraclass. It is the only left alive members of Phascolarctidae. They live both on northern and southern sides of Australia. Individuals from northern population are smaller and have lighter furs compared to the ones living in south. They have live for 13-18 years in wild
Phylogenetic Tree and Hierarchical Classification
The koala is classified with wombats in family Vombatidae with several extinct families including marsupial tapirs, marsupial lions and giant wombats) in the suborder Vombatiformes within the order Diprotodontia (Long, 2002). The Vombatiformes are a sister group to a clade that includes macropods (kangaroos and wallabies) and possums (Asher, Horovitz&Sánchez-Villagra, 2004). Koalas are the only species alive left from familia Phascolarctidae. Some species, such as the Riversleigh rainforest koala (Nimiokoala greystanesi) and some species of Perikoala, were around the same size as the modern koala, while others, such as species of Litokoala, were one-half to two-thirds its size. (Archer et al., 1999).
Physical Features
Koalas have firm body and they do not own any kind of tail. They have white hairy ears and big round nose. Their fur coat has color both in grey and brown. On average they have height of 60-85 cm and weight of 4-15 kg. (Nowak,2005). These features make them to be the largest arboreal marsupials currently (Jackson, 2003). Males are %50 larger than females making them sexually dimorphic.
Koala’s fur is efficiently isolated and is protective against wind and rain, its body part furs reflect the radioactive rays from sun.
Their brain is among the smallest ones in proportion to body weight of mammals(Jackson, p.81). It may be the result of an adaptation to make them survive its low caloric diet from eucalyptus diet. The koala have incisor and cheek teeth which are separated by a large gap(Martin and Handasyde, pp. 46-49).
Feeding Behavior
Koala’s are herbivores and their only nutrition source is eucalyptus leaves which makes the koala gain its carbohydrates from the microorganisms who digest cellulose. Even though there are more than 600 species of eucalyptus trees koalas only prefer about the 30 of them.
They are willing to choose Eucalyptus microcrys, E. tereticornis and E. camaldulensis. Since the eucalyptus trees contain high amount of water, they do not need to drink water frequently. Females can satisfy their needs for water from leaves, males need the extra water from ground or inside of trees. They eat 4 to 6 meals a day each consisting 400 grams of leaves approximately. When they are around 6 years old, their sharpness decreases and finally they may die because of starvation.
Behaviors
Since koalas have low caloric diets, their energy consumption is limited. They sleep 20 hours a day and spend only 4 minutes actively. Koalas spend their days on the same tree. When it is hot, they lay back or on their stomach on branches, dangling their limbs. On cold days, they curl themselves to prevent heat loss.
They are asocial animals and spend only 15 minutes interacting with each others. They communicate with each other through the inhalations. Because of their low frequencies, these sounds can reach very distant places. Koalas especially generate these sounds during their breeding season in order to attract females.
Male koalas behave aggressively to each other on territorial fights. They chase and bite each other. In extreme situations they climb up trees and the large male chases the little one until they reach the end of the branch. In this case weaker koala runs away and climbs down. If the aggressive one catches the weaker one he repeatedly bites his shoulders. As stated by Smith, pregnant and lactating females are particularly aggressive and attack individuals that come too close (1980). Even though koalas do not behave aggressively in which they consume energy.
Reproduction
While mating, the female koala screams and attracts other males to create a fight between all males and she chooses the one she will breed with. Koalas breed only seasonally and they give birth between the months October and May. They have one baby but sometimes they may have twins too. Their gestation period lasts for 33-35 days(Gifford et al, 2002). The newborn has functional respiration, digestion and urinary system. It climbs up to his mother’s pouch and grows there. Unlike other marsupials they do not clean their pouch (Moyal, n.d.). They breastfeed their babies for 6 months and then mother predigests leaves until the baby itself eat leaves. If the mother gets pregnant again their relationship with the previous offspring ends completely with the aggressive behavior of mom against him.
Habitats
They are mainly live on east and south shores of Australia including Queensland, New South Wales, Victoria and South Australia. They are distributed among 1.000.000 km2 and 30 ecological areas. They are lately introduced to Adelaide and on other islands such as Kangaroo Islands and French Island(Gordon, Menkhorst, Robinson, Lunney, Martin & Ellis, 2008). The fossils showed that koalas could live also on Western Australia. Koalas like to live on forests and climates from tropical to cool weathers.
Threats Against Koalas
Even though they fall down a lot from trees, they are generally left with injures. They do not have many enemies but some pythons and wild birds for younger koalas. They are not target of many external parasites but according to a research made in Australian Zoo Wildlife Hospital in Queensland, 73.8% of 600 koalas in hospital were infected with parasitic genus Trypanosoma (McInnes, Gillet, Hanger, Reid & Ryan, 2011).
Koala Retrovirus ( KoRV) causes Koala Immunodeficiency Syndrome, just as AIDS in humans.
The biggest threats against koalas is their habitat destruction. Forest fires divides their habitats and causes limited movement, resulting decrease in genetic variation. Running away from fires, koalas climb up trees but in this case they are exposed to heat and flames. Dehydration and excess heat also result in death.
Koalas are also defenseless against global warming. Climate changes in Australia lead warmer temperatures in future will limit the areas in which koalas can live.
References
• Long, J. A. (2002). Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Johns Hopkins University Press. pp. 77–82
• Asher, R.; Horovitz, I.; Sánchez-Villagra, M. (2004). “First combined cladistic analysis of marsupial mammal interrelationships”. Molecular Phylogenetics and Evolution. 33
• Archer, M.; Arena, R.; Bassarova, M.; Black, K.; Brammall, J.; Cooke, B. M.; Creaser, P; Crosby, K.; Gillespie, A.; Godthelp, H.; Gott, M.; Hand, S. J.; Kear, B. P.; Krikmann, A.; Mackness, B.; Muirhead, J.; Musser, A.; Myers, T.; Pledge, N. S.; Wang, Y.; Wroe, S. (1999). “The evolutionary history and diversity of Australian mammals”. Australian Mammalogy. 21: 1–45.
• Nowak, R. (2005). Walker’s Marsupials of the World. Johns Hopkins University Press. pp. 135–36. ISBN 978-0-8018-8211-1.
• Jackson, S. (2003). Australian Mammals: Biology and Captive Management. CSIRO Publishing. pp. 147–51. ISBN 978-0-643-06635-9.
• Martin, R., Handasyde, K. A., & Lee, A. K. (1999). The koala: natural history, conservation and management. Sydney, Australia: UNSW Press.
• Smith, M. (1980). “Behaviour of the Koala, Phascolarctos cinereus (Goldfuss), in captivity IV. Scent-marking”. Australian Wildlife Research. 7 (1): 35–40. doi:10.1071/WR9800035
• Gifford, A.; Fry, G.; Houlden, B. A.; Fletcher, T. P.; Deane, E. M. (2002). “Gestational length in the koala, Phascolarctos cinereus”. Animal Reproduction Science. 70 (3): 261–66. doi:10.1016/S0378-4320(02)00010-6.
• Moyal, A., & Organ, M. (2008). Koala a historical biography. Collingwood, Vic.: CSIRO Publ.
• McInnes, L. M.; Gillett, A.; Hanger, J.; Reid, S. A.; Ryan, U. M. (2011). “The potential impact of native Australian trypanosome infections on the health of koalas (Phascolarctos cinereus)”. Parasitology. 138 (7): 873–83. doi:10.1017/S0031182011000369. PMID 21524321
• Stoye, J. P. (2006). “Koala retrovirus: A genome invasion in real time”. Genome Biology. 7 (11): 241. doi:10.1186/gb-2006-7-11-241. PMC 1794577Freely accessible. PMID 17118218.
• Gordon, G.; Menkhorst, P.; Robinson, T.; Lunney, D.; Martin, R.; Ellis, M. (2008). “Phascolarctos cinereus”. IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature.