Encyclopedia of Marine Mammals

Group Behavior 511 Mexico recognized the importance of the breeding lagoons to the Reeves, R. R. et al . (2005). Report of the Independent Scientifi c Review recovery of the gray whale and it is the only nation to provide impor- Panel on the Impacts of Sakhalin II Phase 2 on Western North Pacifi c tant habitat protection for the eastern population. In 1972, it estab- Gray Whales and Related Biodiversity. IUCN, Gland, Switzerland. lished Ojo de Liebre Lagoon (the principle calving and nursery area) [Available from http://www.iucn.org ]. as the world’s fi rst whale refuge. In 1979, San Ignacio Lagoon became Rice , D. W. , and Wolman , A. A. ( 1971 ). Life History and Ecology of the Gray Whale ( Eschrichtius robustus ) . Am. Soc. Mamm. Spec. Pub. 3 . a Whale Refuge and Maritime Attraction Zone . In 1980, reserve sta- Rugh , D. J. , Roderick , C. H. , Lerczak , J. A. , and Breiwick , J. M. ( 2005 ). tus extended to Laguna Manuela and Laguna Guerrero Negro. All lie Estimates of abundance of the eastern North Pacifi c stock of gray whales within the El Vizcaíno Biosphere Reserve , created in 1988. In 1993, (Eschrichtius robustus ) 1997–2002 . J. Cetacean Res. Manag. 7 , 1 – 1 2 . the United Nations Educational, Scientifi c, and Cultural Organization Rychel , A. , Reeder , T. , and Berta , A. ( 2004 ). Phylogeny of mysticete (UNESCO) made Ojo de Liebre and San Ignacio Lagoons World whales based on mitochondrial and nuclear data. Mol. Phylogenet. Heritage Sites. Lastly, in 2002, all Mexican territorial seas and EEZ Evol. 32 , 892 – 901 . were declared a refuge to protect large whales. Scammon , C. M. ( 1874 ). “ The Marine Mammals of the Northwestern Coast of North America Together with an Account of the American Whale-Fishery . ” John H. Carmany and Co. , San Francisco . Tomilin, A. G. (1957). “Mammals of the U.S.S.R. and adjacent coun- See Also the Following Articles tries. Vol. IX. Cetacea. ” Akad. Nauk, SSSR, Moscow (transl. by Israel Baleen Whales (Mysticetes) ■ Whaling, Early and Aboriginal ■ Program for Sci. Transl., Jerusalem, 1967) . Whaling, Traditional Urbán-R. , J. , Rojas-Bracho , L. , Pérez-Cortés , H. , Gómez-Gollardo , A. , Swartz , S. , Ludwig , S. , and Brownell , R. L. , Jr. ( 2003 ). A review of gray whales (Eschrichtius robustus ) on their wintering grounds in References Mexican waters . J. Cetacean Res. Manag. 5 , 281 – 295 . G Andrews , R. C. ( 1914 ). Monographs of the Pacifi c Cetacea. I. The California gray whale (Rhachianectes glaucus Cope) . Mem. Am. Mus. Nat. Hist. 1 , 227 – 287 . Alter , S. E. , Rynes , E. , and Palumbi , S. R. ( 2007 ). DNA evidence for his- toric population size and past ecosystem impacts of gray whales. Proc. Natl. Acad. Sci. 104 , 15162 – 15167 . Bisconti , M. , and Varola , A. ( 2006 ). The oldest eschrichtiid mysticete and Group Behavior a new morphological diagnosis of Eschrichtiidae (gray whales) . Riv. Ital. Paleo. Strat. 112 , 1 – 1 1 . ALEJANDRO ACEVEDO-GUTIÉRREZ Cooke, J. G., Weller, D. W., Bradford, A. L., Burdin, A. M., and Brownell, R. L., Jr. (2007). Population assessment of western gray whales any animals spend part or all of their lives in groups. Their in 2007. IWC Scientifi c Committee meeting document SC/59/BRG41. size and composition have diverse effects on morphology and Darling , J. D. , Keogh , K. E. , and Steeves , T. E. ( 1998 ). Gray whale behavior including relative brain size and extent of sexual (Eschrichtius robustus ) habitat utilization and prey species off M dimorphism. A group may be viewed as any set of individuals, belonging Vancouver Island, BC . Mar. Mamm. Sci. 14 , 692 – 720 . to the same species, which remain together for a period of time inter- Dedina , S. ( 2000 ). “ Saving the Gray Whale: People, Politics, and acting with one another to a distinctly greater degree than with other Conservation in Baja California . ” University of Arizona Press , conspecifi cs. Thus, the study of group-living is the study of social behav- Tucson . Deméré , T. A. , Berta , A. , and McGowen , M. R. ( 2005 ). The taxonomic ior, and marine mammal societies can be remarkably diverse (Fig. 1 ) . and evolutionary history of fossil and modern balaenopteroid mysti- Groups can be classifi ed based both on the amount of time indi- cetes . J. Mammal. Evol. 12 , 99 – 143 . viduals interact with each other and on the benefi ts that individuals Geisler , J. H. , and Sanders , A. E. ( 2003 ). Morphological evidence for the receive. Schools last for periods of minutes to hours while groups phylogeny of Cetacea . J. Mammal. Evol. 10 , 23 – 129 . last for months to decades. Aggregations (or non-mutualistic groups) Henderson , D. A. ( 1972 ). “ Men and Whales at Scammon’s Lagoon . ” do not provide a larger benefi t to individuals than if they were alone, Dawson’s Book Shop , Los Angeles . while groups (or mutualistic groups) do provide such benefi t to their Highsmith , R. C. , Coyle , K. O. , Bluhm , B. A. , and Kona , B. ( 2006 ). members. Aggregations are formed because a nonsocial factor, e.g., Gray whales in the Bering and Chukchi Seas . In “ Whales, Whaling, food, attracts individuals to the same place; groups are formed because and Ocean Ecosystems ” ( J. A. Estes , D. P. DeMaster , D. F. Doak , they provide a benefi t to their members. T. M. Williams , and R. L. Brownell , eds ) . University of California Press . Recent studies have highlighted the challenges of defi ning marine Ichishima , H. , Sato , E. , Sagayama , T. , and Kimura , M. ( 2006 ). The oldest mammal groups in nature, particularly those of cetaceans. For record of Eschrichtiidae (Cetacea: Mysticeti) from the late Pliocene, instance, most scientists determine whether individual dolphins belong Hokkaido, Japan . J. Paleontol. 80 , 367 – 379 . to the same group based on the distance separating individuals (usu- Jones , M. L. , Swartz , S. L. , and Leatherwood , S. (eds) ( 1984 ). “ The Gray ally Յ 10 m) or the radius comprised by the group (usually Յ 100 m), Whale Eschrichtius robustus . ” Academic Press , Orlando, Florida, USA . and/or by whether individuals are engaging in the same behavior or Moore , S. E. , Wynne , K. M. , Kinney , J. C. , and Grebmeier, J. M. ( 2007 ). not. However, a study of bottlenose dolphins ( Tursiops truncatus ) in Gray whale occurrence and forage southeast of Kodiak Island, Alaska. Sarasota Bay, Florida, indicates that the communication range of social Mar. Mamm. Sci. 23 ( 2 ) , 419 – 428 . sounds between females and dependent calves could be at a minimum Nerini , M. ( 1984 ). A review of gray whale feeding ecology . In “ The 487 m and reach up to 2 km or more ( Quintana-Rizzo et al ., 2006 ). Gray Whale Eschrichtius robustus ” ( M. L. Jones , S. L. Swartz , and S. Leatherwood , eds ) . Academic Press , Orlando, Florida, USA . Hence, the traditional distinctions of a group—practical, replicable, Omura , H. ( 1984 ). History of gray whales in Japan . In “ The Gray and undoubtedly useful in advancing our understanding of group Whale Eschrichtius robustus ” ( M. L. Jones , S. L. Swartz , and behavior—are likely not meaningful to a cetacean. Because cetaceans S. Leatherwood , eds ) . Academic Press , Orlando, Florida, USA . rely on acoustic communication to maintain group cohesion, the study 512 Group Behavior costs outweigh the benefi ts but strong ecological constraints prevent dispersal from the natal territory (for instance, lack of high-quality breeding openings explains within-population dispersal decisions and family groups in birds), and the area where the group lives can accommodate additional individuals at no cost. A . Benefi ts and Costs of Group-Living Group-living is usually explained in terms of benefi ts to the individual group members via direct or indirect fi tness. Increases in direct fi tness include mechanisms such as direct benefi ts of group- living, direct and indirect reciprocity, and mutualism. Increases in indirect fi tness are achieved via kin selection. It has been argued that (A) when competition occurs at the level of groups rather than individuals, group-living is best explained in terms of benefi ts to the groups themselves, group selection. However, many scientists consider that whenever interactions occur at a local spatial scale, and dispersal is limited, then interactions occur among genetic relatives, and thus G kin selection rather than group selection is operating ( Nowak, 2006 ). Kin selection is perhaps the most frequently employed argument to explain benefi ts of group-living. For instance, kin selection explains the generalities of cooperative breeding in mammals and birds (Brown, 1987 ; Jennions and Macdonald, 1994), and the evolution of coopera- tion among male chimpanzees ( Pan troglodytes ) ( Morin et al ., 1994 ). Further, mammalian female kin (including several odontocete species) spend more time in close proximity and are more likely to help each other. Females may allosuckle or gain higher reproductive success by forming coalitions with kin. However, explanations based on kin selection are in some cases inadequate and some behaviors are best explained in terms of direct fi tness via diverse mechanisms. Direct (B) benefi ts from early detection of danger explain the sentinel behavior of meerkats ( Suricata suricatta ) ( Clutton-Brock et al ., 1999 ) and Figure 1 (A) Blue whales ( Balaenoptera musculus ) are usually delayed direct benefi ts to the subordinate male explain the occurrence found alone or in small numbers. (B) South American sea lions ( Otaria of dual-male courtship displays in long-tailed manakins ( Chiroxiphia fl avescens ) aggregate in large numbers during the breeding season. linearis ) (McDonald and Potts, 1994) . By-product mutualism explains Photos by A. Acevedo-Gutierez. territorial coalitions in Australian fi ddler crabs ( Uca mjoebergi ), which assist other crabs in defending their neighboring territories; in this highlights the importance of understanding communication range to manner, the neighbor keeps its territory and the ally pays to retain an defi ne cetacean groups. established neighbor rather than renegotiate boundaries with a new To describe the social structure of a population, it is essential to neighbor ( Backwell and Jennions, 2004 ).

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