MFR PAPER 1056 



A Note on Gray Whale Behavioral 

 Interactions with Other Marine Mammals 



J. S. LEATHERWOOD 



With the exception of reports of 

 killer whales, Orciniis urea, attacking 

 gray whales. Esihricltuus nihti.siii\. 

 (Scammon, 1874; Andrews. 1914; 

 Gilmore. 1961; Burrage. 1964; More- 

 John, 1968; and Baldridge. 1972) there 

 are no accounts in the literature on 

 the behavioral interactions between 

 gray whales and other marine mam- 

 mals. During aerial surveys of south- 

 ern California cetaceans, (Leather- 

 wood. 1974). I often observed gray 

 whales in close association with other 

 marine mammals (Figure I). Though 

 the abundance of all these species in 

 the area during the winter and spring 

 makes coincidental association likely. 

 the following incidents represent be- 

 havioral interaction; 



Four days after her release, when 

 she was first relocated by aircraft, the 

 gray whale Gigi (Evans. 1974) was 

 swimming with a small group of Pa- 

 cific bottlenose dolphins Tiirsiops sp. 

 in the surf zone just north of the San 

 Clemente. Calif, pier. Though the 

 dolphins left the whale shortly after 

 the aircraft began to circle the area. 

 when first seen they were closely 

 clustered about the head of the gray 

 whale as if riding its pressure wave. 

 Since Gigi was housed during almost 

 her entire internment at .Sea World 

 with an Atlantic bottlenose dolphin. 

 iursiops iniiu alii.s. this association 

 in the wild may have been a result of 

 the captivity. However. I have ob- 

 served gray whales swimming with 

 bottlenose dolphins in the wild in six 

 other instances, in three of which the 

 porpoises were also riding the whales' 

 pressure waves. Further, bottlenose 

 dolphins arc common along the Baja 

 California portion of the gray whales" 



migration route and in the breeding 

 lagoons and have been reported mov- 

 ing freely among California gray 

 whales (Evans and Dreher, 1962). 



On 19 January 1972. three adult 

 gray whales were observed heading 

 southwest over Sixty-Mile Bank (lat. 

 32°()5'N. long. 1 18° lO'W). The entire 

 area was rich with birds and the sur- 

 face action of many schools of small 

 fishes and a large aggregation of odon- 

 tocetes (including over 1.000 northern 

 right-whale dolphins. Liwoclclphis 

 htircalis. approximately 500 Pacific 

 common dolphins. Dclphiiiiis dclphis. 

 approximately 500 North Pacilic 

 white-sided dolphins. Liiiicnoihynclius 

 ohUqKuicns. and at least 3 Dall por- 

 poises. Phocoenoidex dcilli) was pres- 

 ent. The whales were observed at 

 close range from a helicopter for nearly 

 45 minutes and dolphins and porpoises 

 were observed riding the pressure 

 waves of the whales for the entire 



J. S. Leatherwood is with the 

 Naval Undersea Center Bio- 

 Svstems Program, San Uiego, 

 CA 92132. 



time. All species were involved in the 

 interaction. 



In addition, during this same period 

 gray whales were observed riding the 

 large glassy swells which moved 

 through the area. This behavior is 

 common among small dolphins (e.g.. 

 1 iirsidps. Di'lphiiuis. La^enorhyiuhiis, 

 Lissodctphis) and is perhaps not sur- 

 prising for the gray whale in the 

 light of its reported surf-riding (Cald- 

 well and Caldwell. 1963), 



In March 1971. several gray whales 

 were observed along the west side of 

 Catalina Island where an estimated 

 200 pilot whales. Glchiccpliald sp., 

 were distributed in small groups from 

 Ben Wesson Point to the northwest 

 tip of the island. One gray whale was 

 turned belly up in the midst of a pod 

 of 12 or 15 pilot whales, and an adult 

 pilot whale was swimming over the 

 belly of the inverted gray whale. Both 

 were alarmed by the aircraft and 

 sounded on our approach. 



In the other instances (Figure 1) 

 the animals were simply swimming 

 close to each other. With one excep- 

 tion, that of Gigi. all the observed 

 associations between gray whales and 

 other cetaceans involved adult whales. 



Figure 1. — Locations ol 

 sightings of gray whales 

 associated with other ma- 

 rine mammals (1969-1972). 



IURSIOPS SP 

 DEIPHINUSDELPHIS 

 GLOBICEPHALASP 

 PHOCOENOIOES DALLI 

 LAGENORHYNCHUS OBLIQUIOENS 

 LISSODEIPHISBOREALIS 



- Z = ZALOPHUS CALIFORNIANUS 



120 



iir 



118° 



117 



50 



