Monday, December 11, 2006

River otters

I don't know what's going on. There's been water in the swamp since September, the ditch system is full, fields remain flooded and the Mississippi River isn't at flood stage. I don't think the engineers of the area are thrilled with this, but it's good to see water where it should be, even if it's the wrong time of year. Winter is traditionally the time of year when swamps dry out. Late fall and winter rains slowly fill swamp systems, often peaking in the spring, but a swamp with standing water since September is not natural. Footage from the White River basin in Arkansas shows birders paddling through the swamps during early spring and walking through the cypress knees during the fall. Water is important when it nourishes cypresses and kills drought-tolerant trees that don't belong in bottomland hardwood systems. But when trees are dormant, as they are now, all the water in the world won't kill them.

I'm not complaining about all the water. The habitat benefits have been great. Wood ducks hang out all day, four hooded mergansers were paddling around the shrub swamp this morning and pied billed grebes are seen there every afternoon. With all the extra water for the past few months now, I've seen a group of 6 otters playing in the swamp and running the waterlogged ditches through the park. They clearly wouldn't be able to do this without all the water. During any one season, otters can be active along as few as 3 to 10 miles of shoreline but during one year they can run along 50 to 100 miles of shoreline. They've created a circuit of the local ditches, traveling from behind the house to the park along a manmade ditch, eating oversized carp and catfish all along the way. They leave the head skulls and tails for Molly to find.

Otters burrow in the abandoned homes of beavers and muskrats but make their own noticeable entrances, with part of the entrance above water and the rest underwater. The ears and nose close when the animal goes underwater, and the eyes are arranged on the top of the head so they can see above water. When they're out looking for food, otters cruise along the water's surface, using the tail as a rudder. When fish are found, they arch the back and dive in with strong leg strokes to capture the animal. They then pull their prey out of the water onto land and rip it to bits. Last winter, when the swamp was dry, I found a collection of at least 30 southern painted turtle shells that had been ripped apart by otters on a log. I was able to conduct an informal mussel survey thanks to their midden that included 6 different mussel species.

Otters are one of the few animals whose social nature has been recorded. They enjoy sliding down muddy slopes with all four feet folded out of the way with no purpose in mind. They toss mussels and rocks to one another and are generally sociable animals. I mainly see them when they are playing in a small group, yipping, diving and swimming in circles. Before this year I had only known sea otters from the aquarium. My friend Peter is an expert with these animals; sea otters indulge in the same playful behavior and exhibit the same violence towards their prey as river otters. I remember too well the day aquarium staff, without Peter, threw a bunch of grain-fed trout in with the sea otters. The tank turned into a bloodbath, with trout ripped apart in front of Friday's school groups and the water clouded by all the gore. While playful, otters are not gentle animals.

Otter populations in Missouri were at an all-time low in the late 1930s, when the fur trade knocked down the population to roughly 70 individuals in southeast Missouri. In 1982, a state agency released a few hundred otters along the Missouri River and affiliated streams to help repopulate the state. Thanks to stocked farm ponds and fish hatcheries around the state, otters have rebounded and have actually become a nuisance to sport fishermen. The trapping industry is not as active as it was in the 1930s, and otters are thriving. The state agency conducted a survey last summer along the Current River investigating the population density of these playful animals. Now, they've discovered, there are too many otters in Missouri. It's sounding a lot like the white-tailed deer issue...

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