Sightings and follow-up of mothers and calves in the PCFG and implications for internal recruitment

We document the occurrence of mothers and calves in the PCFG area over a more than 20-year period. Over the course of the study 62 moms were documented with 102 calves with a high proportion of these seen in recent years (11 to 18 per year in each of the last four years, 2012-15). This appeared to be a combination of higher number of calves in recent years and greater focus on accurately documenting mothers with calves in more recent years. Overall 59 of 91 (65%) calves documented through 2014 were resighted in a year subsequent to their birth year and indicates a higher degree of internal recruitment to the PCFG than had been suggested by previous less complete data. Average weaning date appeared to be around 1 August, a date earlier than the initial encounters with some whales and indicates how especially in past years with more limited effort, the number of calves would have been underestimated. 

Citation:

Calambokidis, J., and A. Perez. 2017. Sightings and follow-up of mothers and calves in the PCFG and implications for internal recruitment. IWC Report SC/A17/GW/04 for the Workshop on the Status of North Pacific Gray Whales. 27-29 April 2017. La Jolla, CA. 8pp.