Moose falls through ice on MacDougal Lake

Moose 31189 met a fate that is unusual for moose. The first hint of what happened was when we downloaded the locations on the morning of April 18, 2011. The red square that indicates the last location was in the middle of a lake. It is not usual for moose to walk on ice, yet the locations were in the middle of MacDougal Lake and then they stopped.

We thought that there were two likely reasons why the collar would not be transmitting. One possibility was that 31189 had walked out on the ice, and had broken through and drowned. With the collar now underwater, it was not able to transmit to satellites. The other possibility was that wolves had broken through the collar housing. This could have happened whether 31189 had just died, or if he had been killed by wolves.

It took 2 trips to recover the collar. On the first trip we verified that 31189 had broken through the ice. There was too much ice to recover the collar or pull the carcass to shore. On the second trip we recovered the collar and pulled the carcass to shore. Samples were taken for necropsy. We classify this as an accidental death. The recovery of 31189 is documented in these pictures

Parts of an aerial photograph from GoogleEarth showing locations of 31189. The location in the red box is the last location we received, and was an indication of trouble.
That day we took a canoe up to MacDougal Lake to look for 31189. The ice was too thin to walk on, but too thick to break with a canoe paddle. We tied a rope to the canoe and pushed our way out to what looked like a hole in the ice.
We found an area about 6 to 10' wide and 20 feet long that 31189 had pawed out trying to get out of the water. In the upper portion of the picture you can see the hoofprints made by 31189 as he tried to walk across the lake just before falling in. The ice chunks had refrozen.
We tried to find the collar under the ice using our telemetry equipment. We could hear the signal, but it was not safe to move around enough to determine the exact location of the collar.
A week later the ice had melted enough to go out in the water with a canoe. We found 31189 floating head down in the water in a break in the ice.
We pulled 31189 to shore with the canoe after getting a rope around his hind leg. It actually wasn't too hard to move the 800+ pound carcass through the water.
He was too heavy to just lift onto shore though. The first thing we did was pull the collar off.
Next, we rolled him up on shore to prepare for the necropsy. Here we are getting ready to roll the hind legs over.
Winter ticks did not drop off the drowned moose. This image shows both engorged and unengorged ticks. When a moose dies on shore, the ticks move off when body heat is lost by the dead animal. 31189 had many ticks, most of them were on areas that he could rub easily.
Hair had probably been rubbed off the belly rather than slipping off into the lake. The crotch area had many ticks attached.
The whole carcass is too heavy to work with. We began by removing the legs so we could have access to the thoracic cavity where the heart and lungs are located.
We pulled two incisors for aging because we did not pull teeth during capture.
After pulling the carcass on shore, we began the necropsy. We collected tissue samples as part of the cooperative work with the MN DNR. The Wildlife Health Program will screen the moose for diseases and parasites.
The kidney is one organ that is checked for abnormalities. This is what a normal healthy kidney would look like, and because 31189 suffered an accidental death, we'd expect normal appearing organs. In addition, the ice-cold water was an almost perfect preservation temperature.
Another important tissue is the brain. After sectioning the skull, we can remove the brain. Here the brain is being transferred from the skull to the bucket.
This is the rumen of 31189. Rumen contents and other undigested food can be up to 10% of the weight of a moose. We pulled it away from the lake shore.
Cutting the rumen open shows the yellow-greenish color that would be typical. Soon we'll put up images of a moose that was malnourished at death. Rumen color on the malnourished animal was very different.
Close-up of rumen contents. On the rumen wall you can see the papilla which increase surface area to absorb nutrients. The rumen contents have twig particles and some balsam fir needles visible
We dragged the body parts of 31189 away from the lakeshore and left them for scavengers. As we were walking away we wished that we had brought a trail camera along. We will have to bring a camera next time.