Q. What is the difference between a bog, fen, marsh, and swamp?
A. The difference depends on the source of water and the type of vegetation that thrives there, says DNR water-permit supervisor Bruce Gerbig. A bog's primary source of water is precipitation, while groundwater feeds a fen. Woody plants dominate in a swamp, while nonwoody plants characterize a marsh. To learn more, see www.dnr.state.mn.us/wetlands/types.html.
Q. When I was exploring by the river, I found a clamshell that was 7.5 inches wide. How large can clams grow in Minnesota? How old is a clam of this size?
Trevor Duerr, age 7, and Dad
A. DNR mussel expert Mike Davis thinks you found a shell from a pink heelsplitter (Potamilus alatus). These clams can grow to be up to 10 inches across. The one you found might have been 10 to 20 years old. Some clam species live almost 100 years. Minnesota Conservation Volunteer published a Young Naturalists article on mussels in 2000. You can find it at www.dnr.state.mn.us/young_naturalists/mussels.
Q. During the past decade it seems like there are fewer and fewer nesting mallards in our bay on Pelican Lake. A bald eagle has moved nearby, and a slot limit was instituted to help increase the size and number of northern pike on our lake. What impact do bald eagles and northern pike have on mallard populations?
A. Both northern pike and eagles eat ducklings, but loons, mink, turtles, and other large fish will also kill ducklings. Any of these predators could explain the declining number of ducklings you are seeing, says Jeff Lawrence, DNR wetland wildlife populations and research group leader. In your area, water levels, habitat quality, and development may also have an impact on duckling survival.
The decline in the number of mallard pairs could also be due to redistribution of pairs to more favorable areas, such as nearby ponds in the woods or places farther away. Generally, mallard breeding populations have been doing well in Minnesota recently, though there are local exceptions.
Q. Sometimes in late summer we find walkingsticks clinging to the warm side of our cabin. What brings them out? What do they eat? Does anything eat them?
A. Northern walkingsticks (Diapheromera femorata) hatch from tiny eggs in the spring. The nymphs, which look like tiny green adults, eat the leaves of plants such as roses, beaked hazel, and strawberries. In August, they become adults and feed on deciduous trees. Robins and other birds will eat walkingsticks—if they can find them. When a walkingstick feels threatened, it freezes with its front legs stretched out in front of it, making it look almost exactly like a twig.
Q. I shot a chipmunk in our yard, and when I went to throw it into the woods, my brother noticed something very strange. Right above its leg there was something moving. It was about 3 centimeters long and dark with segments. At the protruding end, there was a leechlike opening. The other end sported a pair of retractable hooks. It had burrowed under the skin right up to its head. What is it?
A. Welcome to the wiggly world of the bot fly larva. Scampering around the neighborhood, the chipmunk must have picked up a bot fly egg or larva. When a bot fly larva encounters an animal, it crawls into a body opening, then makes its way to the underside of the skin. There it hangs out and feasts on its host. After about five weeks the bot eats its way out of the animal, leaving a tubular tunnel in the skin. Then the bot falls to the ground and works its way into the soil, where it lives as a pupa until it changes into an adult fly, starting the cycle again.
Q. I have been fishing Lake Ida in Douglas County for 50 years. Lately I have noticed that the mayflies have almost disappeared. Also the tulibee population has diminished. Is something happening to the ecology of the lake?
A. In the past 150 years, the Lake Ida watershed has changed dramatically as farms and housing moved into undeveloped areas. Those changes altered the physical and chemical makeup of the lake and its ability to support the creatures you describe, says Minnesota Pollution Control Agency limnologist Tim James. You haven't seen the end of it: As development continues, James says, the ecosystem impacts will likely grow too.