Evaluation of nutritive condition and reproductive status of migrating gray whales (Eschrichtius robustus) based on analysis of photogrammetric data

Vertical aerial photographs were collected of gray whales migrating along the California Coast between 1994 and 1998 to readdress some published findings on biology life history this population based examination specimens. For each whale, an attempt was made measure standard total length, width whale at its widest point, distance from tip rostrum flukes. southbound whales, early migrants longer average more likely be parturient than those later. Near-term pregnant females wider relative their length other whales. This difference easily detected by visual inspection images through statistical evaluation data. There 100% agreement identification linear regression analysis discriminate all measurements. Based proportion with calves during sampling median calving date estimated 13 January. Southbound averaged 4.6m in length; photographed northbound late April, age about three months, 7.1m. Average for yearlings, combined data, 8.5m. Residuals a compared, significant changes relationship which consistent nutritive condition or fatness described taken 1959 1969 (Rice Wolman, 1971). Parturient cows narrowest sample. The that not associated calf, showed significantly approximately 60 days These results indicate predictable but relatively small fasting winter migration can reliably measurements vertical photographs.