Photographic Identification

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Gray Whale Photographic Identification Surveys

Photo-ID Banner No. 2

Photographic Identification is one of the most powerful and useful tools used to research and understand gray whale movements, life histories, and behavior. Fortunately, gray whales are born with permanent distinctive marking on their skin, and they acquire white scars from injuries, barnacles, and killer whale tooth “rake marks” which aid in the identification of individuals over the years.

The re-identification of individual whales over time provides information on the number of times a whale returns to Laguna San Ignacio or Bahía Magdalena, the minimum amount of time it stayed in the lagoon during the winter, its movements, its health and nutritional state, and if compared to photographs taken in other portions of the gray whales’ range we learn about the whale’s movements within the range. By photographing breeding female whales each time they come to the winter aggregation and breeding lagoon areas with or without a new calf, we can estimate the “calving interval” or the average number of calves produced each year, which is an important index of reproductive health.

Below are tables and figures that summarize the results of the analysis of photo-ID images over the years.

 

NUMBER OF INDIVIDUAL GRAY WHALES PHOTO-IDENTIFIED IN LAGUNA SAN IGNACIO

Photo-ID annual numbers

 

 

 

LENGTH OF STAY IN LAGUNA SAN IGNACIO

Length of stay

 

ANNUAL RETURNS TO LAGUNA SAN IGNACIO

Annual Returns to LSI

 

FEMALE GRAY WHALE REPRODUCTIVE HISTORIES (CALVING INTERVALS)

Calving intervals

 

MOVEMENTS BETWEEN WESTERN & EASTERN NORTH PACIFIC POPULATIONS

W & E movements

 

ESTIMATION OF MINIMUM AGE FROM PHOTO-ID DATA

Minimum age estimates

 

 

 

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