Environmental Engineering Reference
In-Depth Information
Crocodylus porosus has been good and bad for the Territory. Tourists flock here
to see the reptile that walked with dinosaurs and chic women in Tokyo and
Paris love carrying a bit of it over their shoulder. But there has been another
death this year, reminding us all that crocs are among the most dangerous
animals on earth.
Harm
Harmfulness is an essential element in the definition of invasive alien species, and
the reality of harmful invasions should not be denied. For Crocodylus johnstoni , the
spread of introduced cane toads ( Bufus marinus ) was initially disastrous, with
widespread die-offs first noted in 2005. Introduced to Queensland in 1935 to prey
on the (sugar) cane beetle, they spread westward, decimating reptiles that prey on
them, including crocodiles (Letnic et al ., 2008).
In this context, invasive or not, it is well to remember that crocodiles can be
dangerous to humans. Even freshwater crocodiles can and will bite humans, but
this is usually in self-defence, or as a result of mistaking a swimming human for
other, smaller prey. On the other hand, for large saltwater crocodiles, humans are
certainly on the menu. Male saltwater crocodiles reach an average maximum size
of 5m, with some reaching up to 6m in length. Data on crocodile attacks suggests
that most fatal attacks have been carried out by crocodiles longer than 4m. They
have good vision at night and during the day, a good sense of smell and good
hearing. The design of their heads, with raised eyes, ears and nose turrets, and
cryptic colouring, allows them to achieve a considerable degree of stealth when
hunting. They can remain underwater for long periods, with large crocs reputedly
able to remain submerged for up to 3 hours (Caldicott et al ., 2005: 145-146, 150).
In an analysis of crocodile attacks in Australia between 1971 and 2004, Caldicott
et al . found 62 cases of 'definite, unprovoked attacks by saltwater crocodiles,
resulting in injury or death to humans' (Manolis et al ., 2013 update this to 100
attacks by 2012). Attacks on researchers, rangers and farmers working with wild
crocodiles were excluded, as were attacks by captive animals (Caldicott et al ., 2005:
146). This study found a steady increase in overall attacks, but a relative decline in
fatal attacks, over the period (see Figure 15.2). The increase in attacks is perhaps
explicable in light of the increase in the wild population of saltwater crocodiles in
the Northern Territory - from around 5,000 in 1971 to around 75,000 non-
hatchlings in 2000. What is interesting is the relative decline in fatal attacks, given
that there has been a marked increase in average size of the crocodiles in the
population, following protection from hunting. Attacks have occurred at all seasons
of the year, with most in the wet-warm season (November to April) - see Figure
15.3. They are not closely linked to the tourist season (June to August) as most
attacks have involved locals or regular visitors, and also because most visitors avoid
the hottest, wettest months.
Search WWH ::




Custom Search