By Matt Bowser, Entomologist at Kenai National Wildlife Refuge

In early June, I received multiple accounts of abundant black caterpillars stripping foliage along the Marsh Lake Trail on Kenai National Wildlife Refuge. Dark caterpillars were subsequently reported from Cooper Landing to Sterling to Kasilof. These larvae consumed leaves of aspen, highbush cranberry, birch, willows, roses, soapberry, and almost any other broad-leaved plant.  Steve Swenson of the USDA Forest Service tentatively identified them as caterpillars of the battered sallow moth (Sunira verberata). This identification was confirmed when caterpillars my kids and I raised in canning jars eventually emerged as adults in July.

Battered sallow moth caterpillars finish off a leaf on Marsh Lake Trail on Kenai National Wildlife Refuge. Multiple years of defoliation can lead to tree and shrub mortality. Credit: Cynthia Detrow

We periodically see outbreaks of these caterpillars in southern Alaska. The last event was in 2017, when  they were seen in numbers along the Richardson Highway and in the Mat-Su, Anchorage, and Kenai Peninsula.  The largest recorded outbreak of battered sallow moth caterpillars happened during 2003–2006 on the Alaska Peninsula, when up to 20,000 acres of alders and willows were damaged annually.  That outbreak, which may have included speckled green fruitworm moths, killed alders on mountain slopes over large areas. Deciduous trees and shrubs like alders and willows can usually withstand multiple years of their leaves being consumed without suffering lasting damage, so the severity of that event was notable.

Although the battered sallow moth naturally occurs from Alaska to central Canada and south to Colorado, there is no record of outbreaks of this species outside our state.  I wonder why battered sallow moths become so abundant in Alaska but nowhere else.  As with other forest caterpillars with periodic cycles of abundance, declines are likely caused mainly by diseases and parasites that pass through the populations.  At least one other sallow moth species is attacked by short-tailed ichneumon wasps.  The female wasp deposits an egg into a mature caterpillar, and the developing wasp larva will eventually kill its host during the moth’s pupa stage.

A Forest Service report links the 2003–2006 outbreak to higher than normal temperatures, but there’s not enough information yet to explain why higher temperatures might lead to increased populations. In related moths, outbreaks are often terminated by “zombie viruses” that rapidly sweep through dense caterpillar populations. The virus alters the caterpillars’ behavior, causing them to stop feeding and climb to the tops of trees. There the caterpillars die and disintegrate, spreading virus particles over the foliage below, where they can be eaten by other caterpillars. In some species the infected cadavers become attractive to other caterpillars, which cannibalize them and then become “zombie caterpillars” themselves.

An adult battered sallow moth that emerged from caterpillars raised by Matt Bowser (Kenai Refuge entomologist) and his kids this summer.  The caterpillars were provided by Dan Thompson (ADF&G biologist)

Adult battered sallow moths began emerging in late July, continuing into this fall when they presumably lay eggs. The life history of this species has not been worked out, so we do not know when the eggs hatch and larvae begin feeding. The larvae may hatch in the fall, feed and grow some, then overwinter as small caterpillars. Alternatively, the eggs may hatch in early spring. We do know that the caterpillars are out by the beginning of June.

I will pay attention to what happens on the Kenai Refuge this year and next. In general, we would expect trees and shrubs to recover quite well from this year’s damage unless there are high numbers of battered sallow moth caterpillars consuming leaves for multiple years. It’s also possible that other defoliators, like the recently introduced green alder sawfly, may have additive effects on mortality events, an increasing problem as nonnative insects and a warming climate collide.

Want to “Live Your Wild” in a refuge cabin?  Kodiak, Kenai and Tetlin all have public use cabins and Kodiak just added a new one.   There are now nine public use cabins scattered across the Kodiak National Wildlife Refuge.  The most recent addition to the cabin system came “online” in September, and graces a serene site along the Chief Cove shoreline. 

Since all of Kodiak’s cabins are remotely located, the logistics were a bit more involved to get construction crew and materials on-site.  Success was enhanced by all of the pre-planning and preparations that took place prior to leaving the refuge headquarters.  In most years, support could also be provided by refuge pilots, but this year because of COVID-19 concerns, gear and personnel transportation depended entirely on using the refuge vessel Ursa Major II.

We have maintenance workers Danny Hernandez, Darrel Fox, and Kyle Coleman to thank for their efforts and expertise in building the Chief Cove cabin over two weeks in early September.  The construction crew is happy that their work will allow increased access to and appreciation of refuge lands. 

The previously established cabins are in Blue Fox, Deadman, and Viekoda bays, North Frazer, South Frazer, and Uganik lakes, Uganik Island, and Little River.  Each cabin allows visitors to spend extended time exploring the beautiful and breath-taking Kodiak NWR lands and wildlife.  While the cabins are sturdy, nicely appointed, and comfortable, they will, no doubt, also serve as safe shelters from the elements.  All are priced at $45/night, and all have bunk beds to accommodate 4 people (except the Deadman Bay cabin that accommodates 8).

To browse refuge public use cabins and what they have to offer or reserve a cabin follow these links for Kenai and Kodiak on recreation.gov and this link to the refuge website for information on Tetlin’s.  All refuge cabins are very popular so plan ahead.

By Mark Bertram, Supervisory Wildlife Biologist, Yukon Flats National Wildlife Refuge

In recent years, you may have seen a Canada lynx, heard of a lynx sighting from a friend or read about one in your local newspaper.  Lynx populations have been high in much of Alaska, so they have been out and about.  That population high is fueled by snowshoe hares, the primary prey for lynx.  Every decade or so, hare populations skyrocket and then crash.  Lynx populations follow the same cycle as hares but lag by one or two years.  Interestingly, this predator-prey cycle occurs in sync across boreal Alaska.

Dr. Knut Kielland, with the University of Alaska-Fairbanks, has studied this intimate predator-prey relationship since the 1990s.  In 2014, he teamed up with Tetlin National Wildlife Refuge to examine a long-standing scientific theory that the peak of the 10-year hare cycle acts in a synchronous “traveling wave” across the Alaskan and Canadian boreal forest, similar to a rippling wave in a pond. 

But just what is it that sets the wave in motion and carries it over thousands of miles through the boreal biome?  Weather patterns have been suggested, perhaps related to cyclical sunspot activity, but these patterns are inconsistent.  The most likely explanation is long distance movements by predators.  Both lynx and great horned owls disperse over 700 miles in search of food.  Predators moving great distances from food-poor to food-rich areas could explain these 10-year patterns across the landscape.

Photo by Lisa Hupp, FWS

Kanuti, Koyukuk, and Yukon Flats Refuges and Gates of the Arctic National Park and Preserve have since partnered with Dr. Kielland and Tetlin Refuge to collectively examine lynx movements across the northwestern reaches of North America’s expansive boreal forest.  Our goal is to identify which habitat characteristics are critical as dispersal corridors so land managers can maintain viable lynx populations across Alaska conservation units.  To follow lynx movement, we capture lynx in walk-in live traps and attach a radio collar that records location every 4 hours.  Every few days, the collars upload stored locations to a satellite, from which we can subsequently download data. 

In the past four years, 163 lynx were captured and fitted with radio collars near Tok, Fort Yukon, Bettles, Galena and Wiseman, providing hundreds of thousands of locations.  Some lynx stay close to home while others disperse in all directions over great distances (Figure 1).  For instance, Tetlin Refuge biologists collared an adult male near Tok in 2017 that took a year-long sojourn through the Yukon and Northwest Territories, eventually settling west of Great Slave Lake, 2,100 miles away!  In February 2019, another adult male was collared near Bettles.  That April, he headed northwest 550 miles through the Brooks Range to the Chukchi Sea coast near Icy Cape.  In May, he beachcombed south for 200 miles, double-backed along the North Slope for 500 miles to the Dalton Highway at the Sagavanirktok River, and then meandered southwest through the Brooks Range.  Since October 2019, he has taken a respite in a secluded stretch of the Killik River headwaters.

Movements of 163 telemetered Canada lynx across Alaska and northwestern Canada, 2018-2020

We have recorded long distance dispersals for both young and old, male and female, with daily travel averaging 10 miles and up to 27 miles per day!  There appear to be no natural barriers to movement as lynx have trekked across the Brooks and Alaska ranges, and the Wrangell, Cassier and Mackenzie mountains while crossing the formidable waters of the Yukon, Tanana, Porcupine, Copper, Kuskokwim and Mackenzie rivers.  Collectively, this collared sample of Alaska lynx from four refuges and one park have traveled from the Chukchi Sea to British Columbia to the North Slope to the Yukon Delta, traversing through 20 conservation areas thus far. 

Hare populations are now decreasing across Alaska.  In response, we expect more collared lynx will disperse in search of food across the landscape.  As more than 1,000 lynx locations are downloaded daily, university, refuge and park biologists will look closely at these dispersal movement patterns in search of terrain that dispersing lynx prefer.  Identifying landscape corridors that link conservation units in Alaska and Canada will prove valuable in future land use planning.

Want to learn more and see more stunning lynx photos?  Author Mark Bertram will be our speaker at our October membership meeting, October 20 at 5 p.m. on zoom.  Put it on your calendar and watch next month’s newsletter and our web site meetings page for the zoom link.

By John Morton, retired USFWS wildlife biologist

Dr. Lew Coggins, the supervisory biologist at Yukon Delta National Wildlife Refuge, sent me an article he co-authored recently entitled Incorporating harvest–population diversity trade-offs into harvest policy analyses of salmon management in large river basins.  The body of the paper was as technical as the title, so I called Lew to get more context about his research.   

Like other Refuges in Alaska, the 1980 Alaska National Interest Lands Conservation Act mandated that Yukon Delta Refuge conserve natural diversity, but also provide the opportunity for continued subsistence uses by local residents.  In this case, Lew tells me, he initiated the study to help current and future refuge managers evaluate this trade-off and address the concern that current harvest levels based on escapement goals could be impacting the stock diversity of Chinook salmon in the Kuskokwim River. 

Federal and local managers discuss Kuskokwim River fisheries management during a KYUK radio program

Chinook spawn in at least two-dozen tributaries of the main-stem Kuskokwim. Monitoring of harvest, escapement and age composition for Chinook has occurred since the mid-1970s with a focus on 13 stocks (Figure 1).  Recent declines in Kuskokwim Chinook abundance have sharply reduced subsistence harvest, closed commercial fisheries, prompted widespread stakeholder concern about the future of subsistence, and led to disagreement among managers and stakeholders about appropriate management.

Spawning distribution of 13 Chinook populations in the Kuskokwim River basin for which spawner abundance estimates exist based on weir or aerial surveys

The Yukon Delta Refuge has helped host several workshops since 2015 with influential community members as well as USFWS and Alaska Department of Fish and Game biologists and fishery managers. These workshops, funded by the National Fish and Wildlife Foundation, included discussion of existing and potential Kuskokwim Chinook fishery and biological objectives and alternative management actions associated with them.  Lew and his colleagues developed a team that used these capacity building workshops to inform two other, more technical projects funded by the Arctic-Yukon-Kuskokwim Sustainable Salmon Initiative.


Capacity-building workshop with Kuskokwim River stakeholders in Aniak, Alaska

This research considered three contrasting harvest policies that emerged from the workshops:  (1) the “MSY policy” maximizes potential harvest by setting a basin-wide escapement goal and target harvest to produce maximum sustained yield under equilibrium conditions; (2) the “subsistence policy” evaluates a fixed harvest where the harvest goal is equal to that required to meet minimum subsistence needs; and (3) the “conservation policy” maximizes yield from the system but only once biological risks of extirpation to the least productive populations are minimized.  The current management policy seeks to ensure that the total number of Chinook making it to the spawning grounds fall within the range predicted to provide annual harvest greater than 100,000 to fully meet subsistence needs.

Using computer simulation that captured both biological and fishery dynamics, their study shows the trade-offs of these three alternative policies on harvest (a) and harvest stability (b), stock equity (c), and conservation (d).  Figure 2 shows that the policy which focuses on MSY (1) provides the greatest harvest but poor stock equity and a chance that some populations may be extirpated.  In contrast the subsistence policy (2) provides the smallest harvest but greatest harvest stability, whereas the conservation policy (3) provides a middle road with respect to harvest, less harvest stability, but good stock equity and protection.  “The bottom-line”, as Lew explained to me, is that “under current levels of harvest and escapement goals, our modelling suggests the existing levels of stock diversity are protected.”  This is precisely the kind of information that the Yukon Delta Refuge Manager needs to know.

Modeled trade-offs among three harvest policies:  maximum sustained yield (1), subsistence (2), and conservation (3)  to meet fishery (a: harvest and b: harvest stability), equity (c: proportion of population tributaries with spawner abundances that exceeded a tributary-specific spawner goal) and conservation (d: proportion of populations extirpated) objectives. Each bar is the median performance of a given policy over the last 20 years of each simulation

The larger significance of this study is that it scientifically addresses the trade-off between harvests and the protection of diversity, known as the “weak stock problem” in fisheries management. This problem can be acute in large river basins with low levels of management control, like the Kuskokwim, where fisheries for multiple species and stocks in the marine environment or lower river overlap both spatially and temporally.  Doesn’t this sound like many of the salmon fisheries systems in Alaska?

By Jaime Welfelt, Biological Science Technician at Alaska Peninsula and Becharof National Wildlife Refuges

Aerial insectivores, birds that capture their invertebrate prey from the air, have declined more than any other group of North American birds. To monitor aerial insectivore populations in Alaska, a dedicated group of federal, state, university, and nonprofit biologists formed the Alaska Swallow Monitoring Network (ASMN) in 2015. This coordinated effort aligns existing long-term swallow monitoring sites in Fairbanks and McCarthy, while providing a support system to add more sites across the state.

A banded female Tree Swallow collects grass to build a nest in the specially designed box. Once the grass nest cup is complete, the male will bring her white swan or duck feathers to insulate the cup. The side of the nest box is hinged so observers can quickly open the box and record its contents. Using fishing line, we can close the flap on the front of the box, allowing us to capture and band adult birds (photo by Carl Ramm).


The ASMN focused their efforts on Tree Swallows, a wide-ranging aerial insectivore in decline across the northern U.S. and Canada. Tree Swallows make an ideal avian study species because they readily use nest boxes and easily acclimate to human presence. Studies show that Tree Swallow breeding phenology and nesting success are sensitive to extreme weather events and changes in weather patterns over time.   

Alaska Peninsula and Becharof National Wildlife Refuges (AKPB) began monitoring a few Tree Swallow nest boxes in King Salmon in 2007. In 2015, with support from ASMN and a grant from the Environmental Protection Agency, AKPB increased the number of nest boxes and expanded the project to include the neighboring community of Naknek. Yukon Delta Refuge in Bethel joined the ASMN in 2017, as did the Alaska Songbird Institute (Fairbanks), University of Colorado (McCarthy), University of Alaska (Anchorage) and Juneau Audubon Society.

Tree Swallows lay one egg per day, with a typical clutch of 3-7 eggs. Occasionally, in Alaska, we see nests with eight eggs! (photo by Jaime Welfelt).

The Alaska Peninsula encompasses the southwestern-most boundary of the Tree Swallow’s range in Alaska, making it an ideal place to study population changes. On the peninsula, we installed nest boxes on buildings maintained by AKPB, Katmai National Park, Alaska Department of Fish and Game, local businesses, schools, and private residents. Refuge biologists, technicians, student interns, and volunteers check nest boxes regularly and record the number of eggs, when and how many chicks hatch, and when the chicks leave the nest box at the end of the season. The specially designed boxes have a trap door that allows us to capture and band both adults and chicks. The uniquely numbered leg bands allow us to identify individuals and estimate survival rates of recaptured birds. Data from this project will help us better understand the factors affecting Tree Swallow breeding phenology, productivity, and survival in Alaska.

Because AKPB can only be accessed by boat or plane, the Tree Swallow Project provides a unique opportunity to involve the communities of King Salmon and Naknek in our research.  The Tree Swallow Project has reached students across the Alaska Peninsula, including the remote villages of Chignik Lake and Perryville. During summer, Bristol Bay summer camps, homeschool students, and community members in King Salmon and Naknek join Refuge biologists in Tree Swallow banding demonstrations, providing an exciting opportunity to see science in action and live birds in the hand. Statewide, ASMN outreach events and social media posts have reached over 53,000 people.

This project has also been a great avenue for young scientists and summer interns to gain experience in biological field work, managing data, and leading educational events. Since 2016, interns have logged close to 5,000 hours of volunteer time monitoring birds. Business owners and private residents who have volunteered to host nest boxes have expressed much joy in watching the Tree Swallows attend their boxes each summer.

Refuge intern Emily Leung holds an adult Tree Swallow captured at the Bristol Bay School in Naknek (USFWS photo).

A joint analysis of the Tree Swallow data collected in King Salmon, Bethel, Fairbanks, Anchorage, and McCarthy between 2014 and 2019 is currently underway in cooperation with University of Alaska Anchorage and other partners statewide. The results of this analysis will provide a comprehensive look at how aerial insectivores at northern latitudes are responding to changes in their breeding environment. The citizen science approach has allowed us not only to collect excellent data, but has engaged youth and the community in science and natural resource management at AKPB.

Nothing much has changed since last month.  Campgrounds, trails and refuge lands are open as they have been and visitors are flocking to road accessible Kenai.  Visitors need to be extra responsible as there are no campground hosts and few seasonal staff.  Bring correct change for camping fees and firewood from home.  Offices and visitor centers are still closed with no timetable for reopening as the infection rate in Alaska is accelerating.  Kenai Refuge has found a safe way to reach out to visitors in a parking lot,open-air, tent staffed Thursdays through Saturdays.  

If you are traveling to Alaska, be sure to consult State of Alaska regulations which requires testing prior to flights or quarantine after.  If you are thinking of visiting a refuge off the road system, be aware that many rural communities have their own restrictions on travel.  Check with the State, the communities and the refuge you wish to visit for the latest information.