Moose in northern Southeast Alaska

latecomers to the coastal forest

In the past several years, the annual probability of sighting moose or their leavings has increased from something close to zero to a hundred percent. Moose have been reported from the shore of Mendenhall Lake and the airport area to Cowee Meadows and Echo Cove. Many, but not all, of these sightings were of bulls; I saw a cow followed by a young bull in Cowee Meadows a few years ago. I have also seen moose tracks in the Herbert River floodplain forest. It remains to be seen if moose will establish a resident population here; there are pockets of good moose habitat in several places, and I recently learned that moose can do quite well within conifer forests.

Moose arrived in Alaska just before the Bering Land Bridge flooded (14,000 to11,000 years ago). Eventually, by the early 1900s, they made their way down the Taku and Stikine river systems, and down the Alsek to the Yakutat coast a few years later. They arrived in the Chilkat Valley in the 1920s and the population was well established by the early 1930s, peaking in the mid 1960s.

Moose were introduced to Berners Bay almost six decades ago. In 1958 and 1960, twenty-two calves were released (but one died immediately) in the bay area. That local population increased steadily until it reached a point of relative stability in about twelve to fifteen years. Because female moose can reproduce when they are just two years old (occasionally even younger), a female can produce a calf every year, and twin calves are quite common, a rapid rate of population increase can be achieved, in good habitat. Through the 1970s and for the next thirty or more years, the population fluctuated roughly between 100 and 140 animals. Then the population declined sharply, after a couple of hard, snowy winters, but it rapidly re-stabilized at about the previous level.

The rapid rate of population increase in Berners Bay was similar to that following the introduction of moose to the Copper River delta. Mostly in the 1950s, twenty -four young moose were released there; in the following years, the population grew rapidly.

Over in Gustavus, moose were first noted in the 1960s. They are thought to have arrived by emigration from Haines, possibly moving through the Endicott Gap into Glacier Bay and thence to the Gustavus forelands. At first, the numbers were very low, presumably dependent upon occasional additional emigrants arriving in the area. It took several decades for the numbers to increase dramatically, despite the ability of moose to reproduce rapidly and despite what proved to be excellent moose habitat. The slow start in Gustavus, compared to the rapid increase in Berners Bay and the Copper River delta, might have been a result of the very small initial numbers in Gustavus. However, by the early 2000s, the population was extraordinarily high (several hundred moose per 100 square km), so high that a culling program was instituted, cutting the numbers down to about half the peak level (although the population density there is still relatively high, compared to the Interior).

moose-with-twins.jpg
GPS-collared moose with twin calves

It will be interesting to see what happens here in Juneau. The number of moose appears to be very low at the present time (2018), and population growth may be slow, at least at first, as it was in Gustavus.

But where did our moose come from? It’s not clear. Genetic studies would be needed to compare our local moose with those of other places. Previous genetic work has suggested that the established moose populations in Southeast are genetically distinct from each other. The emigrant individuals that founded each now-established population probably did not carry the entire array of genes from the source population but rather just a sample from that gene pool. Furthermore, our mountains and fjords restrict movement between populations, limiting gene flow. In any case, the genetic distinctiveness of established Southeast moose populations may allow future work to identify the source of our local animals.

Moose are herbivores that eat a variety of plant material. In summer, they consume many kinds of greens and twigs; in winter, when green things are scarce, they browse twigs. Their digestive system is very effective in extracting nutrition from plants, because bacteria in the stomach break down cellulose into digestible fragments. The stomach has four chambers: billions of symbiotic bacteria live in the first chamber (the rumen), which also starts to mix the food. The second chamber allows the animal to regurgitate a wad of partially digested food, to chew it again (chewing the cud), further breaking down the plant particles. Saliva from all the chewing helps to bind tannins, which are common defensive compounds of many plants but which can be toxic in high concentrations. The third chamber churns and mixes the processed material and passes it on to the fourth compartment, where the bacteria themselves are digested, releasing useful minerals and other items that moose need. Then all that material goes to the intestine, where nutrients are absorbed. There is not a lot of material left to be eliminated in the feces.

Dense populations of moose can have important effects on their ecosystem. Heavy browsing on willows reduces the number of catkins, an important source of food for bumblebees that pollinate many flowers, including blueberries. Intense browsing of shrubs and saplings might reduce the suitability of habitat for nesting birds by changing vegetation structure, reducing the amount of protective cover and reducing the abundance of insects that normally feed on vegetation. Leaf litter might be reduced, altering the nutrient quality of the soils—the consequences of such effects perhaps depending on the initial condition of the soils. At the present time, moose population density in Juneau seems likely to remain low, but we can be on the look-out for localized effects of browsing. Much more remains to be learned, as always.

Thanks to Kevin White, ADF&G, for helpful consultation and references.

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