Transplants in Southeast Alaska

and the consequences of forced emigration

Since the 1920s, mammals of fourteen species have been transplanted from one location (mostly but not always in Alaska) to another location in Southeast. Many of the official transplants were done with the hope of establishing viable populations of game species in new places, with the goal of providing more prey for humans. The processes of capturing and transporting the unwilling immigrants commonly resulted in high mortality, even before the animals were deposited in their new sites.

Many of the transplantations failed. An attempt to establish a moose population near the Chickamin River in the 1960s failed altogether; all the transplanted young moose died. At that time, officials declared it was too expensive to do a preliminary habitat assessment and thought it more practical to just dump the moose there and see what happened. A number of other transplant attempts over several decades are said to have failed: deer to the Taiya Valley, goats to Chichagof, mink to Strait Island, muskrats and marmot to Prince of Wales, wolf to Coronation Island, snowshoe hare to Admiralty and other islands. Ill-advised attempts in the 40s and 50s to establish populations of non-native raccoons failed.

Some transplants were successful, apparently without any serious preliminary assessments: the mountain goats now living on Baranof are descendants of the transplants in the 1920s, and marten were moved to Prince of Wales, Baranof, and Chichagof in the 1940s and 1950s. After a habitat assessment in Berners Bay, a number of young moose were deposited there in 1958 and 1960; they established themselves successfully and that local population has grown. It may be emigrants from that area that we observe near Cowee Creek, Herbert River, and the Mendenhall Glacier. The possible effects of moose browsing on the structure of the vegetation in Berners Bay are apparently not known; given the notable cropping of willows and other shrubs in Gustavus, one might wonder about the effects on nesting habitats for birds—especially in the light of research elsewhere documenting that over-browsing can drastically reduce bird habitat.

Elk (a non-native species) were brought to four islands in Southeast in the mid to late 1900s. The elk, from Oregon and Washington, were exchanged for mountain goats from Alaska. Only the 1987 introduction of elk to Etolin Island was successful, and elk eventually dispersed from there to nearby Zarembo and other islands. Some preliminary habitat assessments were made, but post-facto concern about possible competition with existing deer populations arose, so continued monitoring and perhaps management are necessary.

After marten were transplanted to the three big islands, red squirrels were often introduced as prey for marten. It later became clear that marten really prefer voles and it is unlikely that the squirrel transplants had much effect on the introduced marten populations. However, it is very likely that the squirrels are having a negative impact on nesting birds on those islands, because they prey on eggs and nestlings.

Collectively, these attempts to establish new populations of mammals are a very mixed bag. There was a high cost in mortality of animals (not to mention dollar costs of capture and transport), many transplant efforts failed, and there was little attention paid to possible consequences. The impetus for game translocations in Southeast may have abated somewhat, and as our ecological understanding has grown over the years, it seems likely that any further transplants would be done with greater concern not only for the animals themselves but also for proper preliminary assessments and the ecological consequences.

Several additional transplants were done in attempts to augment existing populations or to re-establish a previously resident population. However, the effect of adding new animals to an existing population (deer to Kupreanof in 1979, for example) is usually not known. A transplant effort in 1989 attempted to restore a much-reduced population of mountain goats on Mt Juneau, with the stated intent of improved wildlife viewing (!). All the transported goats initially moved away, but by the early 2000s, goats were again seen on the ridge, although no one seems to know if these animals are related to the transplants or from a natural population on nearby ridges.

Sea otters have been re-introduced to many places in Southeast at various times, to restore the natural population that was extirpated by human activity. These transplants are apparently successful and the population of sea otters in Southeast is growing. The consequences of sea otter presence are currently being studied by faculty and students of UAF.

The historical information in this essay derived from Tom Paul’s 2009 ‘Game Transplants in Alaska”, ADFG Technical Bulletin #4. In addition to the official transplantations, there have been an unknown number of unofficial and mostly unrecorded ones, done by private citizens.

Weasels of the forests

martens and fishers in Southeast Alaska

The weasel family is well-represented in Alaska; of the nine species here, three are associated with water and the others are chiefly terrestrial. Of the terrestrial species, marten and fisher are particularly associated with forested habitats.

Marten range over most of Alaska. There are two species of marten here: the American marten lives in the boreal forests across North America including most of Alaska; the Pacific marten lives on Admiralty and Kuiu islands (and maybe some other islands in Southeast). Marten are highly arboreal, spending lots of time in trees but catching much of their prey on the ground. Voles are a favorite prey in most places, but marten can capture prey the size of a marmot or a grouse. Versatile feeders, they also eat carrion and fruit. They have a slender build and an orange-ish patch of fur on the chest.

Fishers live across North American boreal forests but reach their western limit (for some reason) in the southern Yukon and adjacent mainland Southeast Alaska. This species probably originated in eastern North America and spread westward since the last glaciation (but there is said to be an ice-age fossil in central Alaska…). They occur at low densities here and in the Yukon, although there is some evidence that they may be increasing. Fishers are not only rare here but tend to be elusive as well, so sightings of them in the wild are few—and thus they get much less attention than other species. However, in the limited space of this essay, I choose to write more about fishers.

Fishers tend to be larger and burlier than marten, although small female fishers and large male marten may overlap in size. Male fishers commonly weigh 3.5-5.5 kg (some get much bigger!) and females about 2.0-2.6 kg. The fur is usually dark brown, darker than marten, but it sometimes has pale patches here and there. Like all the terrestrial weasels, fishers can climb well, even coming down a tree head-first, like a squirrel. That’s possible because they (like squirrels) can rotate their feet so the curved claws, when extended, hook into the tree trunk.

Both marten and fishers have short legs, so travelling in soft snow can be difficult. Fishers tend to travel less then, or often use existing trails (their own or those of hares). The foot-loading (i.e., body weight per area of foot) of fishers is greater than that of marten, and male fishers have higher foot-loading than females, so they may have a harder time in soft snow. Fishers, perhaps especially males, often leave body-drag marks in soft snow.

Kits are born in spring, often in a tree cavity. Litter size varies with the food supply: usually two or three kits but sometimes more or none at all. Females mate soon after birthing, although the embryo does not implant in the uterus wall until ten or eleven months later (late in the following winter). Gestation takes five or six weeks and the young kits are nursed by the mother for about ten weeks. All mammalian females spend a lot of energy on lactation; for female fishers, the cost of lactation plus the cost of extra hunting activity to fuel that milk production means that the total cost of reproduction is almost three times the energy needed during non-reproductive times. The kits are competent hunters at the age of four of five months, but most females don’t breed until they are two or three years old.

The home range size of fishers varies enormously, from just a few square kilometers to well over a hundred, apparently depending on prey availability. Males range more widely than females. Hares and small rodents are common prey in most places, but fishers also scavenge carcasses opportunistically and eat fruit and invertebrates at times. They can capture prey as big as a chicken or a porcupine; they subdue porcupines by attacking the vulnerable, quill-less nose until the victim is worn out.

The English common name “fisher” is a misnomer. Fishers may scavenge a few dead fish, but fish are not a common item on the menu. The name might come from a French word for the European polecat.

Mustelids

weasels and their kin

One of the treats of a snowy winter is wandering around looking for animal tracks. When I counted up the species for which we’ve found tracks, I saw that one taxonomic family was disproportionately represented—the Mustelidae. Five species of mustelids are likely to leave tracks in snow in our region: ermine, mink, marten, river otter, and wolverine. I’ll first present some basics about mustelids in general, and then some specifics about each of these five species.

Mustelids are a widespread family, occurring on every continent except Australia and Antarctica. There are over fifty-five species, ranging in size from the diminutive least weasel, weighing as little as one or two ounces, to the sea otter, reported to reach over a hundred pounds. They tend to have relatively long, thin body shapes, although some, such as badgers, are stockier; legs are generally short. The claws do not retract (unlike most cats), but again there is an exception: the claws of the fisher are partially retractable. Males are generally larger than females of the same species; their home ranges are larger and tend to overlap those of several females.

They are typically carnivores, preying on a variety of small or middle-sized animals, and sometimes scavengers, although some, such as marten, also eat fruit (and serve as seed dispersers). Much of their ecology is related to availability of food: population abundance, litter size and survival, frequency of reproduction, rate of maturation of juveniles, adult survival (starvation is reported to be a common cause of death in wild populations).

Along with males of many other placental mammals, male mustelids possess a baculum or penis bone. The size of this bone in different species has been suggested to relate to the length of the copulatory act: long bacula are correlated with long copulations. Extended copulations are not generally possible when penile erections depend entirely on hydraulics, i.e. blood pressure. This begs the question of when and where long copulations are adaptive or, conversely, when and where short ones are adaptive. As you might imagine, the subject has attracted some discussion but with no definitive answer.

Most mustelids also share a reproductive habit that (to humans) seems odd: After copulation, the fertilized egg divides just a few times and then rests; it does not implant immediately in the uterine wall, so no placenta is formed and the embryo does not develop further for some time. The delay of implantation lasts several months, during which the few-celled embryo just floats around in the uterus. Eventually, however, it does implant, a placenta develops, and active gestation (just a few weeks long) begins. Thus, the time of mating and the time of active pregnancy are well separated, and birthing is therefore postponed to a season well after the mating season. Delayed implantation is typical of numerous other mammals, including bears and seals.

The adaptive value of a seasonal separation of mating and birthing is often discussed. Most explanations address the importance of rearing young at times of year when food and other conditions are optimal.

This leaves unanswered the reason(s) why mating occurs so long before the season for rearing offspring, and I have not discovered good explanations. In some cases, other aspects of the life history may have created limitations on the convenience of getting male and female together; for instance, bears hibernate for the winter and sexual encounters shortly before birthing are not likely, summertime is surely more convenient; or males take advantage of freedom from child care to go roaming and foraging while females tend the young. I’d like to find a serious analysis of the conditions that favor the seasonal separation of mating and birthing.

Here are a few interesting factoids about our resident mustelids:

River otter—They are very aquatic, eating mostly fish, other aquatic animals in open water or tide pools, and sometimes capturing floating birds from underwater. They can dive to about twenty meters, staying under up to four minutes or so. Being heavy-bodied, they must tread water or scull with the tail to stay afloat. Otters are reported to forage cooperatively in some locations (e.g., Prince William Sound). Otters often travel overland between bodies of water, sometimes sliding over the snow. Their home ranges are said to be smaller on the coast than in the interior, presumably because food sources are more abundant. Otters usually mature at age two years.

Wolverine—They often favor remote areas but use a variety of habitats. In winter, this large mustelid mostly forages by scavenging carcasses left by other predators; its powerful jaws can crack the bones of moose. It is sometimes said that wolverines are too big to survive very long on small prey, too small to kill large game animals regularly, and too slow to chase fast prey. So scavenging becomes a good way to feed. In summer, carrion is less available and wolverines eat more small mammals and birds. They commonly den under deep snow in alpine areas, but commonly travel widely (many miles) to find food. If they get lucky, they will cache surplus food in a handy location. They are slower to mature than our other mustelid residents, usually maturing when three to five years old.

marten-5-Matt-Knutson
marten. Photo by Matt Knutson

Marten—Denizens of old-growth and mature forests, they are highly arboreal. They commonly feed on small mammals, as well as birds, eggs, and carrion, and are said to need the equivalent of at least three voles per day. However, they can also kill hares and marmots. They mature at age one or two years, depending on food supply. There are two species in Southeast; detailed genetic studies have shown that Kuiu and Admiralty islands are home to a distinct and strictly coastal species (which also occurs on Haida Gwaii and Vancouver).

Ermine—They eat almost anything that moves and need to eat almost continually; they are good swimmers and climbers. They make cozy nests, often usurping the nest of a prey mammal (after eating it), even lining the nest with fur of the prey. Well-insulated resting places are necessary for this small, slender predator that needs this help to keep warm in winter. Sometimes they cache their prey near the nest. Juvenile females can become sexually mature while still in the natal nest, at an age of only one or two months. So, when their mother mates after giving birth (which is the custom with these animals), sometimes the same male will fertilize her daughters as well! They have a short life span in the wild, often living less than two years. Ermine are represented by three distinct genetic lineages in our area, and one of them, with a very limited distribution, is considered to be of conservation concern.

Mink—Comfortable on land and in water, they eat fish, crayfish, various other small aquatic critters, and birds—they are said to be especially fond of bird eggs. They make short dives but usually forage in the shallow water or on land. Mink (and wolverines, ermine, and marten) are adept at climbing. They, like squirrels, are able to descend from a tree rapidly and skillfully, because they can rotate their hind ankles so the claws engage with tree bark. They breed as yearlings, and seldom live longer than three years in the wild.

The populations and historical geographic ranges of marten, wolverine, and river otters in North America have been seriously restricted by human activity: habitat loss including deforestation, over-trapping, pollution (especially otters), reduction of their prey populations. In some cases, reintroductions have restored local populations.

Footnote: (There are three other mustelids in Alaska but we don’t generally see evidence of them here. Least weasels live up north and do not occur here. Sea otters live in the sea, yes, and seldom come ashore. Fishers have only rarely been recorded in Southeast and, in any case, are very elusive.)