Crocodile Nomadism: Size Matters

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.

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4 thoughts on “Crocodile Nomadism: Size Matters

  1. There is also hunger. While it is not unusual to find a bear in our neighbourhood in late fall – early winter, we’ve been seeing them earlier and earlier each year. This year there have been 4 maulings (luckily no deaths) by grizzlies just over the hill (Monashee Mountains) from here as unwary hikers came across bears that were feeding. The berry crops up in the mountains has been finishing earlier and earlier in the year for quite some time and the bears have not had enough time to put on sufficient fat reserves for winter denning.

    While this isn’t the same as what you are discussing Greg it is in the sense of unexpectedly seeing wildlife in place but out of time.

  2. Spring is coming earlier and winter later up here. It’s warmer at the higher altitudes. I’ve lived in the West Kootenays since ’97 and I’ve noticed a trend to milder winters, earlier springs and hotter, drier summers. My garden was at least a week, possibly two weeks early this year. Maybe it’s a cyclical pattern but I’d be more likely to bet on global warming affecting the local weather patterns maybe the shift in the jet stream that pushed all that arctic air down your way – I don’t know. The change in climate is probably affecting denning. Waking up too early and struggling to put on enough fat reserves to make it through the winter.

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