Moose are the iconic big game species of the north woods. The largest subspecies is found throughout much of Canada and Alaska, while the lower 48 states have populations of three different subspecies in New England, the Upper Midwest, and Rocky Mountain states. Moose had largely been extirpated through much of their southern range by the late 1800’s, but populations rebounded due to conservation efforts by wildlife managers. Within the last twenty to thirty years, limited hunting programs were established in most states with moose populations. However, in recent years managers have seen declines in moose across most of their range in the lower 48 states causing concern and spurring new research efforts and hunting restrictions. This increased focus should help managers better understand what factors are contributing to the population declines, reports the Wildlife Management Institute.
On February 6, the Minnesota Department of Natural Resources announced they were suspending their moose hunting program in the state indefinitely. The decision was made after the state’s strongest population in the northeast corner of the state saw a 35 percent decline from 2012 to 2013 (4,230 to 2,760) and a 70 percent decline since 2006 (8,840 to 2,760). Just weeks earlier, the DNR had initiated an aggressive moose mortality research project to determine just what is killing the animals. The $1.2 million project will focus on collaring 110 moose and tracking their activity. As of February 13, the agency had reported that they lost the signal for three of the collared moose – if the animals have died, the researchers may have the first opportunity to recover the carcasses and assess cause of death.
While Minnesota is reporting the most dramatic declines, other states throughout the animals’ southern range are also seeing declining populations. In New Hampshire, there are now estimated to be 4,600 moose when the population was once around 7,000 animals. In the Rocky Mountain west, Montana and Wyoming have reported population declines as well and have reduced hunting tags as a result. Montana reported a 40 percent drop in available tags from 769 to 463 between 1995 and 2010. In addition, the Jackson Hole, WY moose herd is at 919 animals, about a quarter of the state’s objective of 3,600 animals. Only Maine has shown a growing population of moose with a recent aerial study estimating more than 75,000 animals, mostly in the more isolated northern part of the state.
The greatest challenge for state wildlife managers is not knowing what is causing the population dips and whether they are symptoms of a longer trend. Historically, most research on moose focused on basic biology and habitat quality assessments. Hunter sampling provided information about diseases and parasites. Some population estimates centered on sampling hunters on their observations while afield, others used infrared techniques and aerial surveys. In Montana, only one of the fifteen studies that were reviewed by the state’s Fish, Wildlife and Parks agency was focused on recruitment and survival and that study was conducted in Glacier National Park.
“There has definitely been a change. Something has been going on and we’ve seen it in the hunter success rates, the amount of effort required to fill a tag and in what hunters report seeing while in the field,” said Justin Gude, Wildlife Research & Technical Services Bureau Chief with Montana Fish, Wildlife and Parks. “But the one thing that is very clear is that there is not enough information – we don’t have substantial evidence of a long term decline, but we need to figure out what is going on.”
With the seemingly precipitous moose population declines, researchers are now scrambling to determine what’s killing the animals and what changes have occurred to tip the scales against them. Winter tick infestations seem to have increased with animals carrying as many as 150,000 ticks. This causes animals to be anemic and have patchy, thinning coats when the animals rub themselves to get rid of the ticks - this leads to a lack of vigor and higher risk of death. The ticks tend to increase in quantity in years with lower snow pack levels and early snow melt.
In addition, brain worm – a common parasite in white tailed deer – will sometimes be ingested in its larval form by moose. While deer can survive the parasites, it is almost always fatal to moose. Kris Rines, New Hampshire Fish and Game’s moose project leader notes that North American research suggests that areas with deer densities about 10-13 per square mile often fail to support a viable moose population. In the western US, arterial worms carried by mule deer and sometimes transmitted by horse flies to moose, have a similar potential to kill moose.
Another factor seems to be habitat changes. In Maine, where moose populations are increasing, the spruce-fir forests that moose prefer are actively managed for commercial timber harvest providing plenty of forage, according to Lee Kantar, deer and moose specialist for the Maine Department of Inland Fisheries and Wildlife. These dynamic changes to the more than 3.5 million acres of privately owned timberlands in Maine’s northern forests have created optimal habitat conditions for the animals.
However, in other regions, these periodic forest disturbances aren’t occurring with the same regularity as in recent years limiting the amount of early successional habitat. Catastrophic fire and insect infestations in spruce forests are also negatively changing habitat dynamics where moose populations occur. In addition, moose appear to have temperature tolerances and become stressed with summer temperatures that top 60 degrees. These disease, parasite and habitat related factors have some pointing towards climate change as a key culprit in the population changes.
In the Rocky Mountains and the Upper Midwest, increasing wolf populations have led others to point the finger toward increased predation as a primary factor. A news article published in Jackson Hole, Wyoming on February 13 reports that 43 moose, including 25 cows were killed by wolves in Grand Teton National Park the winters of 2010 and 2011. Wolves killed another 13 moose in the park in the winter of 2012. But the full implications of predation from wolves, grizzly bears and mountain lions – all of which have had increases in their populations – is not known.
Other science suggests that the declines may not be cause for concern. While populations were higher ten to twenty years ago, the social carrying capacity may have been reached with increased vehicle collisions and agricultural damage occurring. In fact, populations declined in key areas such as the Northeast Kingdom in Vermont and northern New Hampshire due to intentionally increased harvest. Moose have also moved down into more areas with dense human populations in Massachusetts and New York, and biologists located on the Rocky Mountain Front and the northeast plains in Montana have also reported increased moose sightings.
Amidst all the speculation, however, is an increased recognition of the need to gather data that will help answer questions on moose mortality and recruitment. New research is beginning in most of the lower 48 states with moose populations that may help answer these questions. In addition, there is increased collaboration amongst moose biologists in the various states to ensure methodologies are consistent so data will be relevant across states. In May of 2013, the North American Moose Conference & Workshop will be held in New England providing biologists another venue in which to share information.
Perhaps as research data is compiled in the coming years, there will be more answers than questions. As with all wildlife conservation challenges, the “answer” comes back to the combination of factors that are influencing moose populations throughout their range. But when it comes to moose, the larger body of knowledge will hopefully lead to better understanding of the various factors that influence how we manage the great deer of the north woods. (jas)