Nocturnal Haul-Out Patterns of Harbor Seals (Phoca vitulina) Related to Airborne Noise Levels in Bellingham, Washington, USA

Abstract

Given their distribution, harbor seals (Phoca vitulina) are likely to interact with human activities and potentially be disturbed. However, it is unclear how human development affects the haul-out behavior of harbor seals near urban areas. Because disturbance related to human development may increase noise levels in air, one might expect seals to haul-out at times when airborne noise levels are low. This study examined the number of harbor seals hauled-out relative to time of day, noise levels in air, and tide level at two haul-out sites in the city of Bellingham, Washington, USA. Harbor seals were observed from May 2008 to April 2009. Two surveys were conducted every 1 to 2 wks-one during the day and one at night. Harbor seal counts and in-air noise levels were recorded approximately 100 m from each haulout site with binoculars and a sound level meter, respectively. Given the strong correlation between time of day and noise levels, one set of linear mixed effects models examined the interactive influence of time of day and tide level on harbor seal numbers. Another set of models examined the effect of noise level and tide level on harbor seal numbers. Despite fluctuations in harbor seal numbers in relation to time of year and haul-out site, more harbor seals hauled-out during the night than during the day. The best model for the number of harbor seals hauled-out included an interaction between time of day and tide level, and an interaction between noise level and tide level. This study indicated that numbers of harbor seals hauling-out in Bellingham were correlated with time of day and in-air noise levels. However, it is unclear if the nocturnal haul-out behavior of harbor seals was a consequence of human development. It is still possible that an unknown factor associated with time of day was responsible for the observed results. To tease out the correlation between time of day and in-air noise levels, a future comparative study between nearby haul-out sites-one close to human activities and one away from them-is recommended.

A METHOD FOR PREDICTING HARBOR SEAL (PHOCA VITULINA) HAULOUT AND MONITORING LONG‐TERM POPULATION TRENDS WITHOUT TELEMETRY

“…On Kanem Point, haulout was inversely related to tide height. This is consistent with most local, national, and international studies, which have shown that during pupping or molting season, haulout was inversely related to either state of tide or tide level, even at sites whose availability was unaffected by tide (Sullivan [], Schneider and Payne [], Pauli and Terhune [], Thompson et al [], Thompson and Harwood [], Moss [], Kroll [], Frost et al [], Simpkins et al [], Ver Hoef and Frost [], Patterson and Acevedo‐Gutiérrez [], Cunningham et al [], Acevedo‐Gutiérrez and Cendejas‐Zarelli []). In contrast, Hayward et al [] showed that on Violet Point, Protection Island, haulout was directly related to tide height if all other variables were held constant.…”

“…In Orkney, Scotland, during molting season, tidal effects were negligible in the afternoon with peak haulout occurring at about 16:00 hours (Thompson and Harwood []). Simpkins et al [] found that during molting season at two Alaskan haul‐out sites, ideal haul‐out times were near noon if all other factors were held constant, and Acevedo‐Gutiérrez and Cendejas‐Zarelli [] found that haulout on fuel docks at Drayton Harbor, in the north Salish Sea, Washington, increased throughout the day until 19:00, then declined in the hours immediately before sunset.…”

“…Although Frost et al [] found that many surveys ignored environmental effects, Cunningham et al [] point out that an understanding of the factors influencing haulout is crucial for reducing the large variability between surveys. These factors include time of year, time of day, state of tide, tide height, current velocity, substrate, weather, wave intensity, El Niño effects, and level of disturbance (Sullivan [], Schneider and Payne [], Allen et al [], Pauli and Terhune [], Yochem et al [], Thompson et al [], Olesiuk et al [], Thompson and Harwood [], Helander and Bignert [], Moss [], Kroll [], Suryan [], Frost et al [], Baird [], Henry and Hammill [], Simpkins et al [], Ver Hoef and Frost [], Hayward et al [], Patterson and Acevedo‐Gutiérrez [], Becker et al [], Cunningham et al [, ], Acevedo‐Gutiérrez and Cendejas‐Zarelli []).…”

Mother–pup vocal recognition in harbour seals: influence of maternal behaviour, pup voice and habitat sound properties

“…Exposure to waves and substrate as well as anthropogenic disturbance and noise levels are known to influence pinniped haul out site choice (e.g. Acevedo-Gutierrez & Cendejas-Zarelli, 2011;Ban & Trites, 2007;Cordes, Duck, Mackey, Hall, & Thompson, 2011;Suryan & Harvey, 1999). As they are likely to affect motherepup recognition efficiency, acoustic properties could represent additional characteristics influencing harbour seal haul out and reunion site selection during the rearing season.…”

The difference between night and day: The nocturnal and diurnal activity budget of gray seals (Halichoerus grypus) during the breeding season

“…The paucity of studies investigating nighttime activity budgets of pinnipeds on land (breeding colonies or haul‐out sites) has previously been attributed to technological limitations in commercially available night‐vision equipment (Shipley and Strecker , Acevedo‐Guitiérrez and Cendejas‐Zarelli ). Where recent technological advances in telemetry devices, for example, have given ecologically important insights into the circadian behavior of pinnipeds at sea ( e.g., Jessopp et al .…”