Moose 5234 mortality

Moose #5234 was captured and radio-collared on Feb. 21, 2008 southwest of the hamlet of Murphy City, MN and west of Highway 1. She was 9 years old at capture. Her collar had a temperature logger attached to it to record the time and air temperature of whatever habitat she was using. She did not have a calf with her when she was captured in February 2008, although she gave birth to a calf in May 2008. Since the calf (now at almost a year old) wasn't with her when this picture was taken, it is likely the calf didn’t survive the winter of 2008-09.

Moose 5234 as seen from the air on May 4 2009. Her calf from 2008 is not with her and is assumed to have died. From this angle it is only possible to see her radiocollar if you know what to look for, it is much more visible in real life. Other information is also recorded on these flights. From this view we can see that there was relatively little loss of hair due to winter ticks If winter tick populations are high some moose have almost no hair on their back, shoulders, and neck at the end of a winter.

Skeleton of moose #5234 on May 23, 2009, about 4 days after she died. Nearly all of the carcass was consumed by wolves. Wolves fed on the carcass, but there was no clear evidence wolves killed her as opposed to finding and scavenging on a carcass. No evidence of a struggle, such as broken branches and blood stains on surrounding vegetation, was found.

The carcass had been almost entirely consumed in that 4-day time period. The hind legs had been removed from the skeleton and were about 20 feet away. There were several wolf scats around the carcass. Here, Moose biologist Mike Schrage records the GPS location and takes notes at the site of 5234’s carcass. Mike is a Wildlife Biologist for the Fond du Lac Band of Lake Superior Chippewa. After recording the GPS coordinates on the data sheet, he took notes on the condition of her remains and any evidence which might suggest cause of death.

Although flies were present, there were no maggots yet on the carcass. This suggests she hadn’t been dead very long before we arrived at the site of death as eggs laid by the flies had not had time to mature. This close-up of the rumen also gives an indication of what 5234 had been eating before she died. Twigs, some fir needles, new spring growth would be very digestible and not too visible.

Bone marrow fat is the last source of fat consumed if an animal is starving. When this happens the marrow looks red and jelly-like. We cut the femur in half with a bone saw and then look at the cross-section of the femur. From the center out the bone marrow on 5234 was still white with a waxy appearance, indicating starvation probably was not a factor in her death. The blood on the outer edge of the marrow is not what we would look at.

Although much of the hide was still there, only one male winter tick was found. The photo from May 4th and the remaining hide didn't indicate 5234 suffered much hair loss trying to groom away winter ticks so she probably didn’t carry many through the winter. Therefore, ticks are not thought to be a factor in her death. The blade of grass gives an indication of the approximate size of the winter tick when it is not engorged with blood.

The chewed up radio-collar was about 40 feet away from the carcass. Wolves (maybe especially the pups) seem to enjoy chewing on the collar belting material and often carry the collar some distance away. The temperature logger was missing. We don’t know if the wolves removed it or it came off the collar earlier.

We obtained locations on cow 5234 approximately every 2 weeks while she was radiocollared. The white star is where she was captured, and the red star is where we found the collar and skeleton. There was one unusual location, she was found near the railroad tracks on the calf survey flight in the spring of 2008. All of her other locations were west of Highway 1. The light green shading indicates the area within which she spent most of her time.

Mike is suspicious the wolves killed her, as opposed to finding and scavenging a carcass, based on how fresh the carcass was and how thoroughly it was consumed. At almost 11 years old, 5234 was probably past the prime of her life and the winter of 2008-2009 was long with deep snow. Although winter ticks were probably not a factor in her death, she may have suffered from some other disease or parasite making her an easy mark for a hunting wolf pack. However, if this was the case, the wolves ate all the evidence for it. Unfortunately, none of the evidence in her death is conclusive and the cause of death will officially be recorded as “unknown”. Although the cause of her death will be a mystery, while she was alive, 5234’s radiocollar helped moose biologists gain information about moose home range size, pregnancy rates, lifespan and adult and calf survival rates.