The distribution and abundance of harbor seals (Phoca vitulina concolor) in the Woods Hole region

• Main Author: deHart, Pieter A.P.
• Format: Thesis
• Language: English
• Published: Boston University 2002
• Subjects: Biology; Phoca vitulina
• Online Access: https://hdl.handle.net/2144/44792

The presence of Harbor seals (Phoca vitulina concolor) has been noted in the Woods Hole, Massachusetts region in ecological studies for more than two decades, but their seasonal distribution, abundance, and haulout behavior have not been reported. To collect information about the activities and occurrence of this species in the local area, as study was designed to: 1) provide basic ecological information about the population, including baseline distribution and abundance, 2) determine whether these seals exhibit fidelity at the Woods Hole site, and 3) establish how harbor seals react to environmental influences in this non-breeding portion of their range. The study was conducted over two wintering seasons (2000-2001 and 2001- 2002), and utilized both land- and boat-based surveys. Hauled out seals were observed during mid-day low tides to ensure maximum counts. Seals were present in the study area from late September to mid-May. A maximum daily count of 184 seals was observed (mean= 50.95), with the peak numbers of seals hauled out occurring in early May (Season 1) and February (Season 2). Throughout the surveys, environmental conditions, such as wind speed/ direction, cloud cover, temperature, tide, and human presence, were recorded and analyzed with respect to observed behavior. In season 1, wind direction significantly influenced the number hauled out; westerly winds yielded higher counts. Totaling the seasonal and environmental factors demonstrated that tide height had the greatest influence on seal abundance. Seals were photographed and a few were individually identified and resighted, indicating potential intra-seasonal site fidelity. This study opens the door to further research on the population biology of harbor seals in the Woods Hole region.