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

Abstract

We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt.

Temporal variations in terrestrial counts of Pacific harbor seals in the southern California Current System

“…Previous studies reported late April as an optimal period for finding the highest number of individuals on land on San Roque Island (Tapia‐Harris et al . ), which coincides with the results of this study. In contrast, for Todos Santos Island, previous studies suggested early May as optimal for finding the highest aggregation of individuals on land (Fernández‐Martín et al .…”

“…, Tapia‐Harris et al . ); however, the results obtained by this study point to early June as the main aggregation peak for this island. In conclusion, these results suggest that future counts for abundance estimations should be performed during the last days of April in the southern colonies near San Roque Island (including Asuncion, Natividad, and Cedros Islands, as well as the San Benito Archipelago) and during the first days of June in the northern colonies near Todos Santos Island (including Coronado, San Martín, and San Jerónimo Islands).…”

“…, Tapia‐Harris et al . ): a haul‐out site on the coast, Punta Banda Estuary, and two on islands off the west coast of the Baja California Peninsula, Todos Santos and San Roque Islands. The latter together with Asuncion Bay, comprise the southernmost colonies of this subspecies’ global range (Fig.…”

The Pacific harbor seal gut microbiota in Mexico: Its relationship with diet and functional inferences

“…The coordinates of the specific beaches where samples were collected are available in the metadata of the sequencing project in the database repository. Samples were collected during the molting season, when the highest numbers of individuals haul out [30] tending to remain on shore for many hours [31]. Each sample was collected individually using a disposable sterilized spatula.…”

Climate causes shifts in grey seal phenology by modifying age structure

“…Phenological shifts in life-history events, including breeding [37][38][39], pupping [40] and moulting [41] have been reported in many seal species. Many species of seal are known to undergo delayed implantation, or embryonic diapause [42][43][44], in common with other large carnivore species [45][46][47][48][49].…”