Adult moose mortality project

Causes of adult moose mortalities

February 2013 - June 2016 (n=49)

Moose 192 report

Moose 192, a 12-year old cow that DNR researchers collared in 2015, died in April along a Superior National Forest road not too far west of Finland.

Necropsy results showed three serious health problems:

• A winter tick infestation causing major hair loss and anemia from blood loss
• A liver fluke infection, one of the worst encountered so far in the study, that weakens moose and predisposes them to other illness
• The presence of brainworm, severe infections of which cause circling, weakness in the hindquarters, inability to stand, turning of the neck and head to one side, lethargy, apparent blindness, loss of fear and rapid eye movement.

Despite these conditions, the cow settled down in late April to give birth to a healthy bull calf. While calving, which made her extremely vulnerable, wolves attacked and inflicted massive injuries to her head and rump.

Moose 192 fought off her attackers though and, with her bull calf still in the birth canal, wandered about 1,000 yards north and laid down in a watery ditch along the roadside, tucking her front legs underneath. She likely drew her last breaths when under water as she and her unborn calf died.

The mortality study will consider Moose 192's official cause of death to be wolf kill. But facts gathered from the GPS collar and results of the necropsy show that this moose endured serious health conditions. Calving – not sickness – made her vulnerable to a wolf attack. But it's likely that health conditions eventually would have killed her.

Moose 21 report

An alert from the collar of Moose 21, a nine-year-old bull collared in 2013, sent the retrieval team to an alive but unable to stand animal on April 28. In fact, the moose didn't even try to move when the team arrived.

The moose was euthanized and a field necropsy was performed because the moose had sought shelter in dense cover, making extraction of the carcass impossible.

A severe winter tick infestation was apparent. There was significant hair loss and the animal was covered in ticks. The bull was emaciated and all his organs were pale, a condition caused by severe anemia.

Examination of organ samples done later in the lab revealed the moose also had meningitis in the brain and may have suffered from a mild brainworm infection.

Sickness caused by the winter tick infestation was the primary cause of death.

Moose 205 report

The mortality implant transmitter and collar on this six-year-old bull, which was collared in 2015, sent alerts at 7 a.m. on Thursday, Jan. 7. By 1:30 p.m., the crew had located the carcass. The moose had shed its antlers and was skinny before it laid down; it appeared to have collapsed where it laid.

Using snowmobiles and a special folding sled, crew members retrieved the entire carcass and hauled it the University of Minnesota laboratory by pickup truck that evening.

Necropsy results showed an emaciated animal with a weight of only 795 pounds. Bone marrow in its femur was red and jelly like, indicating that the moose was starving and its body had consumed its last source of remaining fat from its bone marrow.

The exam also revealed that the moose had a severe case of hepatitis, which had been induced by liver flukes. Infectious bacteria were isolated from the liver and lungs and the abdomen was inflamed. The bacterial infection, caused by liver fluke induced hepatitis, was the primary cause of death.