Kangaroo Managment Plan - Territory and Municipal Services - ACT ...

ACT KANGAROO MANAGEMENT PLAN
being estimated at about 20 years (Kirkpatrick 1965b). There may be higher survivorship in older
age classes where populations are not heavily culled or predated (e.g. some ACT reserve areas)
(Fletcher 2006a).
The importance of nutrition for sub-adult kangaroos has been discussed above. In the ACT the
mortality of eastern grey kangaroos is concentrated in late winter and early spring, and the
evidence suggests that the ultimate cause of this is starvation. Parasites, hypothermia, pneumonia,
other diseases and predation contribute to this mortality as proximal causes (Fletcher 2006a).
Kangaroos evolved with predators some of which existed until relatively recently or are still
present: the marsupial lion (Thylacoleo carnifex) in the Pleistocene; the thylacine (Thylacinus
cynocephalus); Tasmanian devil (Sarcophilus harrisii) and the dingo (Canis lupus) (Robertshaw
and Harden 1989). Hunting by Aborigines, European hunting, culling, commercial harvesting
and accidental death through vehicle collisions may be considered as forms of, or equivalent to
predation. The flight response of kangaroos is positively related to the likelihood of collisions with
vehicles, implying that flight by kangaroos may not be an effective defence against vehicles (Lee
et al. 2010). The importance of predation sensitive foraging, rather than simply direct predation,
in limiting kangaroo population numbers has been noted previously (see s. 3.3.2).
Speare et al. (1989) reviewed the range of diseases that affect Macropodoidea, noting that while
individuals in populations die from specific diseases; these are end points of environmental
fluctuations and habitat changes that influence population dynamics. Generally, major diseases
in wild animals should be treated as multi-layered processes (Dawson 1995). Significant disease
outbreaks which cause population ‘crashes’ often are associated with some form of stress such as
extreme environmental conditions e.g. drought, flooding or severe hot or cold weather. In these
circumstances the disease may be only the proximal cause of death (Dawson 1995).
Examples of common afflictions of kangaroos are lumpy jaw and the presence of large numbers of
nematodes. Lumpy jaw is a chronic infection caused by the bacterium Fusobacterium necrophorum
and is associated with lowered host resistance due to stress factors (Speare et al. 1989). Kangaroos
often have large numbers of benign nematodes in their guts, but the presence of high numbers
of harmful internal parasitic nematodes, especially Globocephaloides trifidospicularis, has been
associated with kangaroo mortality (e.g. Quin 1989). This nematode species can cause heavy
mortality in juvenile kangaroos in enclosed populations when winter feed is depleted and when
small animals with no fat reserves experience maximum cold stress (Arundel et al. 1990). In these
circumstances, starvation is probably both the ultimate cause of death and a necessary precursor
for high parasite levels across a population (Fletcher 2006a).
3.3.8 Determination of kangaroo body condition
The definitive measures of condition in wild mammals are kidney fat index and percent marrow
fat (Caughley and Sinclair 1994). These can only be derived by taking samples from dead animals
and it would be desirable to find measurements which can be taken on living kangaroos that
correlate with these standards. Visual assessments of the condition of kangaroos are commonly
stated but are rarely checked against independent measurements and can easily be wrong. For
example, the post mortem results from 306 of the kangaroos shot in a cull at Belconnen Naval
Transmitting Station in 2008 contradicted some visual assessments (e.g. National Kangaroo
Protection Coalition 2008b). In fact the kangaroos had not been in good condition when visually
assessed. Many (42% of females and 56% of males) had no kidney fat remaining and 38% of
females and 47% of males had less than 50% marrow fat remaining (unpublished data, ACT Parks,
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