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Resource ID
10542
Access
Open
Full Title
Gray whales’ body condition in Laguna San Ignacio, BCS, México, during 2019 winter breeding season
Author
F. Ronzón-Contreras, S. Martínez-Aguilar, S.L. Swartz, E. Calderon-Yañez and J. Urbán R.
Abstract
The Eastern North Pacific (ENP) gray whale (Eschrichtius robustus) population feeds during the summer around the Bering, Chukchi and Beaufort seas, and migrates to winter breeding and calving grounds along the Pacific coast of Baja California, in Mexico. Measurements of the whales’ body condition upon arrival at the breeding grounds is an indicator of “health and reproductive condition,” and indirectly is an indicator of the health of the environment. We photographed and evaluated the body condition of 569 gray whales in Laguna San Ignacio (LSI) in Baja California Sur in 2019. Photographs were sorted into two reproductive-sex categories: Females with calves, and Single whales (male or female without a calf). Condition was scored as “good”, “fair”, or “poor” using a method developed for the Western North Pacific (WNP) gray whales. In 2019 the proportion of single whales with “good condition” was 22.1%; "fair" 54.3% and "poor" 23.6%. The percent of “poor” body condition in 2019 is the highest observed in LSI in the last ten years. The proportion of females with calves with “good,” "fair", and "poor"; condition in 2019 were 50.0%, 50.0%, and 0%, respectively. The decrease of single whales in “good” condition during 2019 was not reflected in the percent of females with calves, but may be the result of a small sample of female-calf pairs photo-identified in 2019 (n=41), compared to the average of 226 pairs photo-identified each year from 2011 to 2017. We conclude that the body condition of all whales was probably similarly affected; however, comparison and correlation with environmental data from the feeding grounds is needed to understand the factors that contribute to the whales’ body and reproductive condition.
