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What's cost of development on dwindling moose population?

Rick Sinnott

Have you ever visited some part of Anchorage that you haven’t frequented for a month or so, only to discover a new hotel, office building, or subdivision arising from a freshly cleared patch of woods? Every time a new building, road, or parking lot is built in Anchorage, moose lose a little bit of living space.

I’ve always said that Anchorage is people habitat. I live in a house, too, so it’s not fair to expect everyone else to live in moss-covered mounds in the woods. But Anchorage is different from other cities, and one of the features making our city unique is the wildlife living around us. No other city the size of Anchorage is adorned with hundreds of free-ranging moose. Anchorage wouldn’t be Anchorage without its urban moose. They are so ubiquitous that some of us take them for granted.

A recent project on Joint Base Elmendorf-Richardson (JBER) will allow land managers to calculate the cost of development on moose. Ultimately, the technique could be employed throughout the Anchorage area. Preliminary results were presented in Anchorage at the annual meeting of the Alaska Chapter of The Wildlife Society. Joe Welch, a graduate student at the University of Alaska Fairbanks, is spearheading the research. Perry Barboza and Don Spalinger, both experts on wildlife nutrition with the University of Alaska, are advising. Sean Farley, a wildlife physiologist with the Alaska Department of Fish and Game is also supervising the work. JBER secured funding for the study.

Brief history of moose in Anchorage

Before Anchorage was established, moose were scarce in upper Cook Inlet, according to Wilfred Osgood, a biologist with the federal Division of Biological Survey who collected bird and mammal sightings and specimens in 1900. Osgood interviewed Dena’ina elders who told him moose had only recently appeared on the west side of Cook Inlet. No moose were there when they were boys. The mature forest in the area was a mix of deciduous trees, mostly birch and cottonwood, and spruce.

A mature forest is not ideal moose habitat. However, about the same time as Osgood’s visit, a period of explosive population growth was triggered by widespread regeneration of woody vegetation. The regrowth resulted from wildfires set by miners and the Alaska Railroad, followed by settlers and the military who cleared large tracts of mature forest.

After decades of complete protection, except from poachers, moose numbers in the Anchorage area probably peaked in the early 1950s. The first closely monitored hunt was held in 1954. Since then moose have been harvested to maintain their population at a level the habitat can support.

The 1960s, 1970s and 1980s saw more clearing throughout the Anchorage Bowl, Eagle River, and Chugiak as the growing city shouldered aside natural habitats. In some cases, sites were cleared but nothing was built for years; the resulting patches of young trees and shrubs proved better moose habitat than the native old-growth forest. However, beginning in the 1990s the amount of available moose habitat appears to have declined faster than new habitat was created by the regeneration of cleared areas. Anchorage has fewer moose now than it did two decades ago.

The founding of Anchorage created shrubby habitat welcomed by the now-familiar urban moose. But Anchorage’s welcome mat is shrinking. Ultimately, the nutritional model developed by Welch and his advisors will help measure the rate of shrinkage and predict the results of future development on moose.

Constructing the model

In the simplest terms, the nutritional model is based on what a moose requires nutritionally and the quantity and quality of forage in the area. But a lot of fieldwork was needed to fine-tune the model for local conditions.

Welch and his advisors captured, collected samples from, and radio-collared 19 adult female moose on JBER from 2009 to 2011. These moose were observed and recaptured periodically to take more samples. Moose pellets were collected to ascertain what the moose were eating.

A laboratory at Colorado State University analyzed the composition of the moose pellets and reported the proportion of various plants in the diet during summer and winter. Welch also collected leaves and stems from plant species consumed by moose to measure their nitrogen content, digestible dry matter, and energy content. This allowed him to determine the nutritional value of moose browse in different species and seasons. Welch measured each moose’s rump fat in early and late winter using a portable ultrasound machine. Rump fat thickness is correlated with total body fat, a critical measure of a moose’s condition.

Welch found that 70 percent of the local moose diet for a brief period in spring consists of forbs, broad-leaved, non-woody plants like fireweed. But the leaves and stems of woody plants dominated their diet the remainder of the year. In summer, the bulk of their diet was willow leaves. In winter, moose predominately ate the thin stems of willows, birches, and cottonwoods.

Yes, yes, you say. Anyone who knows Alaska’s moose is fully aware they eat the leaves and twigs of willows, birches, and cottonwoods. What wasn’t known was what proportion of the diet was comprised of these species and how much forage was available in the various habitats in the Anchorage area. If we knew these two points, we’d know which areas were most important to Anchorage’s foraging moose, and we’d be able to estimate approximately how many moose we’d lose if those areas were turned into something else. Like the Seawolf Arena currently under construction on the University of Alaska–Anchorage campus – 14 acres of former moose habitat being converted into a sports arena and parking lot.

Converting habitat into browsing moose

And that’s exactly what Welch and his advisors have come up with. By plugging Welch’s measurements of the quantity, quality, and distribution of moose browse into the model, it is possible to calculate the number of “animal units” supported by each habitat type.

An animal unit is the amount of food needed to support one adult cow, in this case a cow moose. A related term, the animal-unit month, is the amount of food needed to support one adult cow for one month. The concept of animal units and animal-unit months has been used by range and pasture managers for cattle, sheep and other domesticated livestock for decades. Wildlife managers use it less because managing moose in the woods is much more difficult and complex than fine-tuning the number of cattle that a pasture can support. For one thing, a rancher doesn’t usually have to account for a significant level of predation. But Welch’s application – measuring the loss of moose per unit of habitat – may be a useful tool in land planning.

Cataloging important moose habitat

Previous scientific studies on JBER mapped more than 50 distinct types of habitat. Welch condensed the categories into seven habitat types relevant to moose. He then sampled the foods moose eat from each of these habitat types to ascertain total available forage and nutritional value of each habitat type. Because the habitat types are mapped in a GIS database, their areas can be precisely determined.

Welch modeled nutritional demands to determine the relative value of habitats based on the daily requirements of female moose. Nitrogen is an essential nutrient in limited supply. In winter, low concentrations of available nitrogen in stems limited the number of animal units that a habitat could support. In summer, energy content and digestible dry matter of leaves were more limiting than nitrogen, mainly because there’s a limit to how much bulk a moose can process through its four-chambered stomach. In all habitats, animals were most limited by winter nutrition.

Welch found some habitats were more valuable to moose than others. The most extensive habitat type in the Anchorage area is mixed deciduous-spruce forest. But shrub lands have the most palatable leaf and stem material per acre. An acre of shrub lands has 17 times more moose forage than an acre of mixed forest. Shrub lands – 12 percent of local habitat – provide 74 percent of the forage. Shrub lands are located in subalpine areas, predominantly in Chugach State Park, but they are also abundant in fragmented patches in and around developed areas.

Habitat in the cleared and more developed parts of JBER supports a greater density of moose than many more natural habitats because the developed areas include proportionately more shrub lands. However, like the rest of Anchorage, this is likely to be a temporary phenomenon because the shrubby areas are subsequently developed or grow out of reach. Furthermore, nutrition is not a moose’s only concern. Negotiating the maze of fences, especially with a calf in tow, and dodging motor vehicles also constrain moose numbers in developed areas.

A little too much like Albuquerque

JBER commissioned the study to better assess the impact of military development on moose. However, the information is not solely applicable to JBER. The Anchorage Bowl, Eagle River, and other developed areas share similar habitats. When Welch’s thesis is completed, peer-reviewed, and published, with a few tweaks, land managers will be able to calculate the number of moose that will be lost irrevocably by a proposed development project in the Anchorage area. This information should prove useful to the public and decision-makers.  

Describing the headlong history and cookie-cutter strip development of Anchorage, the author Joe McGinniss, in “Going to Extremes”, wrote “When in Anchorage, in other words, you might as well be in Albuquerque…” What redeems the city, keeps it from becoming Los Anchorage in spirit, are the little Alaskan touches. Like moose in the streets.

Few people would want to proscribe development to protect the moose of Anchorage, but even fewer will be satisfied to sit back and let rampant development snuff out most of the local moose. Anchorage already looks a little too much like Albuquerque for some tastes.

Rick Sinnott is a former Alaska Department of Fish and Game wildlife biologist. The views expressed here are the writer's own and are not necessarily endorsed by Alaska Dispatch. Contact him at  rickjsinnott@gmail.com