Prince William Sound Black Bears: On the Rise?

Black bear (taken in Southeast Alaska). Photo by Allison Sayer. 

By Allison Sayer

How many black bears live on Prince William Sound? That’s a question that even Chugach National Forest Wildlife Biologist Milo Burcham and ADF&G Area Wildlife Biologist Charlotte Westing do not know the answer to, despite years of intensive work on Prince William Sound black bears. They shared a summary of their work at the 2021 Prince William Sound Natural History Symposium hosted virtually by the Prince William Sound Stewardship Foundation. 

According to Westing, 3,700 bears is a rough estimate of the Sound’s black bear population, but it is really just a “wild guess.” However, guides, transporters, researchers, hunters, fishers, and recreational users have all informally reported seeing fewer black bears on Prince William Sound since the early 2000s. 

Westing cites two major changes that have increased pressure on black bears. The Exxon Valdez Oil Spill raised the profile of Prince William Sound globally, bringing more people to the region. Opening the tunnel to Whittier in June of 2000 to passenger vehicles also greatly increased traffic on the Sound. The number of vehicles driving to Whittier increased from approximately 20,000 to between 100,000 and 120,000 annually. 

Prior to the tunnel opening, the number of black bears harvested annually was about 200. With the opening of the tunnel, the number soon doubled, and then almost tripled by 2007. After 2007, the number of bears taken began to decline. Whether this is a proxy for a dip in the population is not certain. During the early 2000s, some management tools were employed such as shortening seasons and restricting some areas from bear baiting. However, it was not known how much harvest of this subsistence resource was sustainable and how much management would be excessive. This is still an open question. 

The number of black bears successfully harvested dropped precipitously after the “snowpocalypse” event of 2011. During both the snowpocalypse and the year following, a much higher percentage of females was also taken. Westing believes one reason female harvest proportion increased during tough years was that there were fewer females with cubs. 

The presence of cubs is one of the main tools hunters can use to distinguish between males and females in the field. However, female bears delay implantation of embryos until they go into hibernation. If females are not healthy enough to have cubs, the embryo will not develop. 

Even in good years, females typically have cubs every other year, which means that every other year they are less distinct from males. However, male bears can be more conspicuous to hunters than even females without cubs because they tend to cover more ground, often on the coastlines, pursuing food or mates. An increase in the proportion of females harvested could indicate that hunters were working harder to find bears to harvest at all, or that the number of adult males available for harvest was already low. 

A higher female take is undesirable for long-term population recovery from an environmental event, and may have compounded its effect. Westing believes that hunting pressure on the population prior to the snowpocalypse event also made the population less resilient. However, she emphasized that this is based on her best guess as to what was happening. 

After 2012, Westing employed additional management tools in the hope of helping the population recover, and giving her more timely in-season information. This included changing the hunt to a registration hunt in 2015. 

According to Westing, trends seem to be going in a positive direction for black bears now. Biology seems to be on the bears’ side. 2015 seems to have been a good year for cub production and/or survival, as seen by a large cohort of 2015-born bears that are now in the adult population. 

The proportion of successful hunts is increasing, another good sign. It had dropped from about 50% to as low as 10% following 2012, but it is now climbing towards 30%. The proportion of female bears harvested has also dropped to below 25% which is thought to be a desirable target for sustaining the population. The number of bears harvested has settled at about 200 per year. 

A research study led by Burcham will help with black bear management by helping to increase managers’ understanding of how bears use the environment in Prince William Sound. Burcham and a team trapped, measured, and collared bears on Knight and Esther Islands, islands with abundant black bears but differing amounts of hunting pressure. Collaring began in 2016, and continued through 2018. Data is still coming in from collars.  

The goals of the research study are to learn more about black bear habitat use, and compare habitat use by bears subject to differing amounts of hunting pressure. Examining bear movement patterns during a berry failure in 2018 is showing how bears react to environmental pressure. The collar study is also helping researchers learn more about the basic life history of Prince William Sound bears. 

Complete results from the collaring study are not yet available. Habitat use patterns analyzed so far did help Westing confirm that higher female take rates are not a result of females using beach habitat at a higher rate than males. This strengthened her belief that higher female takes are more likely related to females having fewer cubs during tough times. As would be expected, it was also possible to see more bears swimming to other habitats during a time when berries were less abundant. Comparison of habitat use between years and between islands is ongoing. 

Collaring bears has also made it possible to learn more about bears’ dens. The favorite den type for Prince William Sound black bears seems to be a crevice between a tree root system and a rock or shelf. Researchers were able to visit some dens and learn more about cub production from 2017 through 2020. Collar data also show detailed information about bears’ activity entering and exiting the den through the seasons. 

The overall bear population of Prince William Sound and a target for sustainable harvest are still not known. Funding priorities are an obstacle towards performing Sound-wide population studies. However, the collared bear data, harvest data, and other tools may help to create a sustainable target for the future.