On a misty, cool morning at the mouth of an estuary, we documented pink and chum salmon carcasses both in and along the stream bed, and taken into the surrounding forest for consumption.
A coastal sea wolf had been observed earlier that morning by team members on an early wildlife watch zodiac trip, so we knew a pack was in the area. Unfortunately a visiting charter fishing boat discharged a smaller vessel loaded with seven individuals who dispersed into the stream and up the estuary knee deep in waders hoping to snag the pink salmon heading up the river on fly fishing rods.
At this stage in the spawning cycle, salmon are uninterested in feeding and are approaching their terminal location so fishing on these streams usually involves casting into the schools of fish and hoping to snag one on a hook as it swims upstream. With the influx of human activity in and around the stream, further wolf sightings were unlikely.
Littered along the river bed were salmon carcasses left largely intact except for the heads, which had been meticulously consumed, likely by wolves. In contrast to the grizzlies and black bears that feed on salmon, wolves have developed a specialized consumption to avoid parasitic disease (1).
By eating the head alone, wolves may have found a way to avoid “salmon poisoning”, a bacterial toxicity, concentrated in the kidneys and muscles of raw salmon, that can be fatal to canid species. This selective consumption also allows the wolves to avoid tapeworms and other parasites that often infect bears during the salmon season.
In two separate locations, both along the lower river bank and on upper hillsides above the main creek, grizzly bear and wolf scat were observed. In one location approximately 8 scat piles were noted in a 10 metre radius at various stages of decomposition. At this first site a grizzly ‘mark’ tree was documented, with the deep gouges and unique claw formation, and hairs were observed where bears had rubbed to mark territory or passage.
At a second site farther upstream, the team made an exciting discovery: a very lengthy grizzly ‘mark’ trail, a kind of superhighway for grizzlies. In the majority of mark trails, the length from shore to a terminus point in the woods is quite short. The team followed a clearly defined and fresh trail of multiple grizzly prints markedly farther than had been previously observed.
All through the forest salmon carcasses were observed, often draped over logs and bush debris (think Salvador Dali’s watch painting). The transport of salmon for consumption inland is a major contributor to forest health and diversity and predators play a critical role in nutrient delivery to both ecosystems and other salmon-dependent species.
No bears were sighted in the three days at various anchorages – it’s likely bears and wolves were feeding nocturnally or at very early dawn and very late dusk. An outstanding amount of fresh scat observed daily, along with routine fresh tracks and carcasses, indicated a high level of habitat use by both bears and wolves along the salmon systems we visited.
Back in the inlet, we were lucky to witness a humpback whale solo bubble-net feeding; a spectacular surface feeding behaviour in which whales use bubbles blown from their blowholes to trap fish in tight schools close to the surface. After snapping a few ID photos, we were able to identify the whale as BCX1665, who had been recorded in this specific inlet in years past. BCX1665 is identifiable by the extensive rake mark scars (inflicted by mammal eating killer whales) along the underside of their tail fluke. It is unknown whether BCX1665 is male or female but it is known that this individual travels to Mexico for the breeding season and is a member of a threatened population under the Endangered Species Act in the United States.
It was a powerful experience to take up momentary space in this vast web of interconnectedness and see first-hand evidence of ecosystem balancing cooperation. We are so grateful for these moments in the field connecting us to our conservation work.
(1) Salmon can be infected by Neorickettsia helminthoeca via a trematode vector (Nano-phyetus salmincola). Neorickettsia helminthoeca causes “salmon poisoning disease”, which can be fatal to canids (Young and Goldman 1944; reviews in Philip 1955; Knapp and Millemann 1970). Metacercariae of N. helminthoeca occur in the head and dermal tissue of salmon but are thought to concentrate in kidney and muscles of infected fish (Bennington and Pratt 1960; Baldwin et al. 1967). Reports of this parasite exist throughout the Pacific Basin from the conterminous United States to far eastern Russia (Witenberg 1932; Knapp and Millemann 1970; Booth et al. 1984). Young and Goldman (1944) suggested that salmon poisoning influenced wolf abundance and might have been responsible for the almost total disappear-ance of wolves from Oregon by the early 1890s. (Foraging behaviour by gray wolves on salmon streams in British Columbia, C.T. Darimont, T.E. Reimchen, and P.C. Paquet, University of Victoria)
