The timing of pupping and molting of the Pacific harbor seal, Phoca vitulina richardii, at Punta Banda Estuary, Baja California, Mexico

Abstract

Pupping and molting of Phoca vitulina are processes that occur each year with high precision, although their timing varies according to location. Knowledge about the timing of these events allows us to determine when the highest numbers of individuals are hauled out, which is important to achieve a good abundance estimation. In this study we determined the timing of pupping and molting of P. v. richardii at Punta Banda Estuary, Baja California (Mexico), previously unknown at this site or along its entire distribution in Mexico. Observations were carried out during the 2011 and 2012 pupping seasons, as well as the 2012 molting season. We determined that the pupping season starts in mid-February and ends in mid-April, and that the maximum number of pups occurs in mid-March. The late premolt stage was observed from the end of March to the beginning of July, with the peak proportion of individuals in this stage at the beginning of May. The molting period extends from the end of April to mid-July, with the peak proportion of individuals molting at the beginning of June. The reverse molt pattern (starting on the torso and ending on the head and flippers) was the most common. The highest number of adult and subadult individuals on land was observed during the molting season; therefore, the best time to carry out counts to estimate seal abundance in this area is from the beginning of May to the beginning of June.

Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula, Mexico

“… and Fernández‐Martín et al . ), this trend is not observed, since the molt phase lasts 17 wk on San Roque Island and between 11 and 12 wk at Punta Banda Estuary, Todos Santos Island, and Tugidak Island.…”

“…Punta Banda Estuary and Todos Santos are located at similar latitudes and are separated by only 17 km yet seals started to molt 1 wk earlier at Todos Santos (Fernández‐Martín et al . ). The duration of the molt was similar (11.3 wk at Punta Banda and 11.9 wk on Todos Santos), although the peak molting date differed by nearly 2 wk (10 June for Punta Banda and 26 May for Todos Santos).…”

“…The San Roque colony, one of the southernmost colonies of this subspecies’ global distribution, is the first colony to begin molting (in February), followed by the colonies at Punta Banda Estuary (Fernández‐Martín et al . ) and Todos Santos Island in northern Mexico (in April). In California, colonies begin molting in June (Flynn et al .…”

“…References: (1) this study, (2) Fernández‐Martín et al . (), (3) Grigg et al . (), (4) Flynn et al .…”

“…, Fernández‐Martín et al . ). Also, timing of molt depends on the age and sex of individuals (Thompson and Rothery , Daniel et al .…”