After trial and error, researchers may have found a way to reduce calf abandonment
REGIONAL— Wildlife researchers hoping to learn more about the causes behind the decline of moose in northeastern Minnesota were frustrated last year when a number of moose mothers abandoned their calves following the capture and GPS-collaring of their newborns.
Glenn DelGiudice, who oversees the calf study, and his research team spent much of the past year looking for possible reasons for the high rate of abandonment, with little success. In other parts of North America, moose mothers will fight humans, wolves, or anything else that threatens their young. But in Minnesota, researchers found moose mothers were more likely to shrink into the forest. While most eventually returned to their calves, about one in five did not. It not only dismayed researchers, it prompted significant criticism from the public of the study, since all of the abandoned calves ultimately died.
Now, after adjusting their capture methods, biologists believe they may finally have found a solution, and it wasn’t what they were expecting.
“The initial consensus was to capture without the use of helicopters,” said DelGiudice. Last year, researchers had hired an Alaskan helicopter crew that specializes in capturing wildlife to corral the moose calves and give the research team time to attach a GPS-collar, take a blood sample and other readings. After consulting with other biologists, DelGiudice and his team concluded that the disturbance of the helicopter was likely the cause of the high rate of abandonment.
So this year, a team of four biologists dispensed with helicopters and traveled by foot through the woods to sites where GPS-collared female moose had recently given birth. They hoped the new method would reduce abandonments— but their hopes were soon dashed, as mother moose continued to abandon their young, at an even higher rate than last year.
Between May 15-18, the team captured a total of 12 calves, and seven were ultimately abandoned. Unlike last year, however, the research team had a plan to rescue the abandoned newborns. Six of the seven abandoned calves were ultimately captured and sent to the Minnesota Zoo, which had been looking for young moose to add to its collection. The seventh calf died before the team could retrieve it.
But for DelGuidice and his team, saving most of the calves from certain death was slim comfort, and he was ready to call off the collaring effort, which would have essentially ended his research. But after taking a few days to regroup, he devised one last-ditch plan— to send in a two-person crew, with scent block, that would attach a GPS-collar and immediately leave. They would collect no blood samples or take other readings or measurements. Rather than the usual four minutes of contact with the calves, they would be gone in mere seconds.
He told his team if any more of the calves were abandoned, they would call off the study. “I was very close to ending this,” said DelGiudice.
From May 21-June 7, the team collared 11 calves from nine females using the new method, with not a single capture-related abandonment. “We’ve had 100 percent success since then,” said DelGiudice.
But for the young moose, abandoned or not, life in the wild is often short. Of the 16 calves that were collared and not abandoned, six have already died— three from wolf attack, one from a bear, one from natural abandonment due to illness, and one that had not yet been recovered for analysis. Two of the calves slipped their collars, so their fate remains unknown.
Last year, of the 40 moose calves that were not abandoned by their mothers, only eight remained alive going into the winter. The team has since removed the radio collars from those moose, so it’s not known how well they survived the harsh conditions this past winter.
Another focus for research
Why Minnesota moose mothers are so quick to abandon their young remains a mystery, and it’s one that has now become a secondary focus of DelGiudice’s research. In the past, he said, abandonment has never been a research focus, but is usually mentioned only anecdotally in study reports. But with the new GPS technology that DelGiudice’s team uses to track the movements of both adult moose and their calves, biologists can now track the movements of mother and calf much more closely than was possible in the past. Surprisingly, said DelGiudice, in many cases the mother moose did return to their collared calves following capture, sometimes repeatedly, before ultimately abandoning them.
DelGuidice said it still isn’t clear why the maternal bond isn’t stronger in Minnesota moose, and it’s in sharp contrast to his earlier experience studying whitetail deer.
“In the early 2000s, we did a study on fawns. We captured and collared nearly 100 newborns and would regularly have 10-12 people with us, including the media. We often handled them up to 30 minutes, and had no capture-related abandonments.”
Having finally found an apparent solution to the abandonment problem, DelGiudice and his team are making plans for a bigger effort next year. “We plan to use two teams to get 50 calves collared,” he said. That should provide the biologists a clear sense of whether their method really is the magic bullet for reducing abandonment by mother moose. If so, DelGiudice said it’s an important advance in wildlife research. “We really feel this will have positive implications for studies of other large animals,” he said.