SOLVING MONTANA’S MOOSE MYSTERIES FWP researchers search for answers to help conserve these popular big game animals in the face of rising temperatures, shrinking habitat, and more predators. BY TOM DICKSON DONALD M. JONES 12 | SEPTEMBER–OCTOBER 2019 | FWP.MT.GOV/MTOUTDOORS MONTANA OUTDOORS | 13 each year, compared to 25,000 elk and 95,000 mule deer and white-tailed deer. Moose managers have long been frus- In winter, the Big Hole valley looks like a trated by the scant information, especially re- garding population sizes and trends, which vast white lake lapping against the Pioneer help them determine hunting harvest quotas. “It’s a major dilemma,” says Ryan Rauscher, Mountains to the east and the Beaverhead FWP wildlife biologist in Conrad, whose Mountains to the west. The 15-mile-wide expanse of work area includes moose range along the Rocky Mountain Front. “If a moose popula- snow sits atop a mix of sagebrush prairie, pasture, tion is trending down and we overharvest by hayfields, and willow swamp. Within this broad valley issuing too many licenses, we could set re- covery back for years.” and surrounding forests resides one of the state’s At the same time, if managers don’t know largest moose populations. that a population is growing and could sustain additional harvest, they must be On a frigid February morning, the tem- and possessing a noble snout, moose are cautious and issue fewer licenses than if they perature hovering around -20 F., Montana one of western Montana’s most popular had more accurate data. “That means Fish, Wildlife & Parks wildlife research biol- wildlife species. Tourist shops sell sweat- denying some hunters a hunt of a lifetime,” ogist Nick DeCesare and I are driving across shirts, mugs, and postcards adorned with says Rauscher. the valley near Wisdom searching for a cow images of this largest member of the deer The need for information grew in the moose he has radio-collared. Two miles out family. “Landowners, hunters, residents, mid-1990s, as hunters and others started of town, he parks his pickup along a frozen nonresidents—you name it—I’ve found that reporting fewer moose in parts of western county road. After picking up a strong signal almost everyone loves moose,” says Jesse Montana. Hunter success rates began with his radio receiver, we wade through Newby, an FWP wildlife research technician declining too, as did annual harvest. The hot, knee-deep snow in pursuit. working with DeCesare. dry years of the early 2000s raised “There,” DeCesare says a few minutes Despite the popularity of Alces alces, Mon- concerns further. Moose require cool, wet later, pointing to two distant dark shapes. A tana wildlife managers lack information about climates and can overheat in summer cow moose sporting a bright white collar the species’ diet, movements, pregnancy rates, temperatures above 60 degrees. Large and her calf pause against a stand of wil- and other basic “vital rates.” FWP lacked mammals that need Alaskan weather were lows. Then they amble off, long legs carrying funds to study a species that generates rela- enduring Arizona-like conditions. them easily through the deep drifts. Trudg- tively little hunting license revenue. Only British Columbia, Maine, Vermont, ing after the pair, DeCesare gathers a hand- about 300 moose are harvested in Montana Wyo- ming, and other provinces and states ful of the cow’s fresh thumb-sized droppings to be tested for progesterone, indicating pregnancy. DeCesare, who earned his doctorate in wildlife biology at the University of Mon- tana, makes his way back to his truck. He mentions that he’s been following this par- ticular moose for six years, watching her raise calves to young adulthood as part of a study he’s doing with other research scien- tists. “It’s great getting all this broad popu- lation-wide data that will eventually be S; DONALD M. JONES used to manage moose,” he says. “But it’s also pretty neat that we get to intimately OUTDOOR OFFICE know these individual moose year after FWP wildlife research biologist Nick DeCesare, who runs the 10- MONTANA OUTDOOR MONTANA year. They’re such cool animals.” year moose study, logs data after gathering droppings from a cow moose in the Big Hole WELL-LOVED valley. Chemical analysis will determine if Few would disagree. Nearly as large as a she’s pregnant. Later surveys will monitor horse, graceful and stately in movement, whether the cow gives birth, and how well the calf (or calves, if twins) survives (right). LEFT TO RIGHT: TOM DICKSON/ TOM RIGHT: LEFT TO 14 | SEPTEMBER–OCTOBER 2019 | FWP.MT.GOV/MTOUTDOORS MONTANA OUTDOORS | 15 FACTORS AFFECTING also were reporting moose declines (though if so, whether to single calves or twins. The clude Safari Club International, The Nature VARIABLES MOOSE POPULATIONS in some parts of North America, including researchers check a few months later to Conservancy, and dozens of local landown- northeastern Montana, numbers were in- monitor calf survival, then fly again the fol- ers, as well as other wildlife agencies in the INFLUENCES FACTORS AFFECTING POPULATION POPULATION TREND creasing). A population in Minnesota, one of lowing March to see if the young are still United States and Canada studying moose the largest in the lower 48 states, crashed alive and thus have been “recruited” into and sharing results. Successful moose HUNTER HARVEST NUTRITIONAL CONDITION from roughly 4,000 in the mid-1980s to the population. “The first year is critical,” hunters also assist by sending in blood sam- almost zero in the mid-2000s. “We started Newby says. “That’s when calves are most ples and measuring rump fat to provide addi- PREDATION to wonder: Is there a continent-wide trend vulnerable to predators, disease, and mal- tional data. ADULT FEMALE SURVIVAL that Montana is a part of?” says Justin Gude, nutrition. If they make it through their first FORAGE & HABITAT or head of FWP’s wildlife research program. MAJOR FINDINGS ADULT FEMALE FECUNDITY Meanwhile, wolf and other large carni- Now on year seven of the study, researchers PARASITES & DISEASE vore numbers were increasing. And logging, have already learned much about Montana’s which opens forests to sunlight that gener- moose. Perhaps most significantly, none of HEAT STRESS & SNOW CALF SURVIVAL ates more willows and other shrubs that the three studied populations appears in dire moose prefer, had declined for decades. straits. “We didn’t know what we’d find, so The main factors that determine whether a moose population increases or decreases: survival of adult females (which produce young and thus drive a population), Were these factors driving moose numbers that’s definitely good news,” DeCesare says. cow moose pregnancy rates (fecundity), and calf survival. Driving fecundity and calf survival is the animals’ health (nutritional condition), which is influenced by down? What about parasites—winter ticks, The main discovery in the Big Hole is that habitat, disease, and stress; other influences are hunter harvest and predation. FWP researchers are monitoring and measuring all these influences and factors. brain worms, arterial worms, and liver many adult moose are being killed by three- flukes—to which moose are particularly vul- inch-long parasites transmitted from horse- nerable? “With so many possible factors, it flies. These arterial ormsw congregate in the 1.00 was impossible to figure out the right course arteries at the base of the animal’s head and Population growth rates: 2013–2018 +4% +8% +12% +16% +20% of action for managing moose,” says Gude. apparently restrict blood flow to the brain. This chart shows the two main factors affecting “We needed answers.” Researchers found Big Hole pregnancy moose populations: cow survival rates and rates 0.95 -4% MOOSE MONITORING Nick DeCesare with rates and calf survival comparable to the of calf recruitment (survival to age one). The dark +3% a cow moose tranquilized from a dart fired line in the middle indicates a stable population. 10 YEARS, 3 AREAS other areas, but that hasn’t fully offset the -8% STABLE POPULATION +11% from a helicopter. After drawing blood Populations above the line are growing, and the one 0.90 Since 2013, FWP research scientists have decline in adult cow numbers. The result has samples and taking body measurements, below the line is shrinking slightly. Note that even worked to answer these and other moose he attaches a collar fitted with a radio been a slight annual population decline of though calf survival in the Cabinet-Salish is relatively -12% management questions with an unprece- transmitter. Transmitters on 162 moose 3 percent over the past six years. “The two low, the population is still increasing at 3% per year .085 -3% dented 10-year study. Its two primary goals tracked in the three study areas (below) drivers of moose populations are adult due to the high cow survival. allow scientists to locate individual animals -16% are (1) understand the relative importance of female mortality and calf survival,” Newby On the Front, both rates are and see which habitats they use and how high, leading to an 11% adult cow survival, cow pregnancy, calf sur- explains. “And of the two, cow mortality is 0.80 well they survive from year to year. annual population growth. survival female Adult -20% vival, and other factors driving moose popu- the biggest factor. That’s why the Big Hole lation ups and downs; and (2) find a cost- population is struggling a bit.” n Cabinet-Salish Moose Population Ecology Study Areas 0.75 effective way to monitor moose numbers in Researchers’ most important finding in n Big Hole Valley 0.00 0.10 0.20 0.30 .040 0.50 the future.