Haul-Out Behavior of Harbor Seals (Phoca vitulina) in Hood Canal, Washington

Abstract

The goal of this study was to model haul-out behavior of harbor seals (Phoca vitulina) in the Hood Canal region of Washington State with respect to changes in physiological, environmental, and temporal covariates. Previous research has provided a solid understanding of seal haul-out behavior. Here, we expand on that work using a generalized linear mixed model (GLMM) with temporal autocorrelation and a large dataset. Our dataset included behavioral haul-out records from archival and VHF radio tag deployments on 25 individual seals representing 61,430 seal hours. A novel application for increased computational efficiency allowed us to examine this large dataset with a GLMM that appropriately accounts for temporal autocorellation. We found significant relationships with the covariates hour of day, day of year, minutes from high tide and year. Additionally, there was a significant effect of the interaction term hour of day : day of year. This interaction term demonstrated that seals are more likely to haul out during nighttime hours in August and September, but then switch to predominantly daylight haul-out patterns in October and November. We attribute this change in behavior to an effect of human disturbance levels. This study also examined a unique ecological event to determine the role of increased killer whale (Orcinus orca) predation on haul-out behavior. In 2003 and 2005 these harbor seals were exposed to unprecedented levels of killer whale predation and results show an overall increase in haul-out probability after exposure to killer whales. The outcome of this study will be integral to understanding any changes in population abundance as a result of increased killer whale predation.

Dynamic habitat corridors for marine predators; intensive use of a coastal channel by harbour seals is modulated by tidal currents

“…These results support preliminary surveys in this area which observed that hauled-out seal numbers increased during the ebbing tide, with highest numbers observed from about 3.5 h before low tide until half an hour after (Cunningham et al 2010). So in addition to the in-water behaviour, the haul-out patterns appear relatively unusual and contrasts with the more traditional understanding that haul-out behaviour peaks at the transition of ebb and flood tides (Schneider and Payne 1983; Pauli and Terhune 1987); this adds to increasing evidence that haul-out patterns of harbour seals in some locations may not be driven by tide but by a complex interaction of environmental variables such as diel rhythms (Calambokidis et al 1987; Hamilton et al 2014), predation risk (London et al 2012) and weather conditions (Schneider and Payne 1983; Grellier et al 1996). …”

Long-term effects of land use on perinatal mortality in the Endangered Saimaa ringed seal population

“…Harbour seals Phoca vitulina have also been observed to avoid contact with humans (Henry & Hammill 2001, London et al 2012, Blundell & Pendleton 2015, and the most critical time for this is thought to be the breeding period. Several studies of pinniped species have indicated that the presence of humans in creases pup mortality (Kenyon 1972, Mattlin 1978, Kovacs & Innes 1990, Stevens & Boness 2003, and there have been suggestions that such disturbance can also affect the breeding success of Saimaa ringed seals (Sipilä 2003, Ministry of the Environment 2011), although the long-term effects on the population are difficult to quantify.…”

Post‐disturbance haulout behaviour of harbour seals

“…For example, Henry and Hammill (2001) suggested that increased leisure activity increased the number of occasions harbour seals were flushed into the water in Métis Bay, Canada. Harbour seals may also switch to a nocturnal haulout pattern to avoid hauling out during the day when daytime anthropogenic activity is high (London, Hoef, Jeffries, Lance, & Boveng, 2012). Harbour seals may also switch to a nocturnal haulout pattern to avoid hauling out during the day when daytime anthropogenic activity is high (London, Hoef, Jeffries, Lance, & Boveng, 2012).…”