Every now and then an animal shows up where it is unexpected. Why just the other day a black bear had to be coaxed out of a tree down by the middle school, a couple of blocks form here. Even though our marshes, woodlands, and small patches of prairie house cougars, coyotes, deer, and all the smaller critters, both bears and wolves are not at present endemic to the Twin Cities suburbs.
When the unexpected appearance of a wild animal happens, there are usually one three factors at play. A migratory animal (typically a bird) is a bit off course, or lands where it normally flies over. The loon in the puddle by the gas station a couple of years ago, the rosette spoonbill up at the lake a few years ago, etc. A second reason, often used to explain moose in Massachusetts several years back, until it was realized that they were simply moving into the region, is disease. Some brain disease cause some mammals to wander aimlessly and that could result in the animal wandering far out of its range. The third reason which almost always applies, I think, to the occasional wolf or bear sighting ’round these parts, is dispersal. Without dispersal, nothing would be anywhere. Obviously. (Dispersal is linked to expansion of range, of course.)
And that, dispersal, is probably what is going on when a 3 meter long crocodile shows up at your barbecue in Queensland Australia. That, and of course, the steaks on the barbie which are irresistible to megafauna carnivores.
A team of researchers led by Craig Franklin, of the University of Queensland has been tracking crocodiles in the region for several years now. They discovered that smaller crocs don’t wander much, and the largest ones, those approaching five meters, don’t either. The small crocs are hiding out in good spots, and the larger ones are highly territorial, dominating a particular water hole. The in between size, mainly around 3 – 3.5 meters, are the the most nomadic. Some have traveled up to 1,000 kilometers over a year’s time, and up to 60 kilometers a day.
The team is now upgrading their equipment to include tracking devices that last longer.
You can observe the movements of some of their research subjects at the Franklin Eco-laboratory web site, here.