Serenading the dolphins
Dusky dolphins (Lagenorhynchus obscurus)
Dusky dolphins (Lagenorhynchus obscurus) are commonly found in the coastal waters in the Southern Hemisphere, more notably around New Zealand, South America and South Africa (Wursig & Wursig, 1980). They are known for having a wide range of aerial behavior such as leaps, backslaps and spins as well as being diurnal creatures, meaning that they are more active in the day and less active at night (Ibid).
Dusky dolphins’ social behavior is characterized by fission-fusion dynamics, where individuals alter their grouping patterns according to their needs and activities (Markowitz, 2004; Pearson, 2009). For example, group size increases during foraging and decreases during mating, resting and traveling periods.
Studies of dusky dolphins off Kaikoura, New Zealand revealed that dolphins normally live in larger groups, before splitting into smaller sub-groups for social-sexual activities (Markowitz, 2004). The dusky dolphin’s mating system has commonly been described as “promiscuous”, because both males and females mate with multiple partners and unlike other species like the bottlenose dolphins, male dusky dolphins are unable to dominate the females (Markowitz et al, 2010).
The interesting mating behavior of dusky dolphins lies in the females’ preference for speed and agility rather than aggression or size of the male (Markowitz, 2004), hence high-speed activities are more common in mating groups than other sub-groups. Female dolphins also have a tendency to extend the high-speed chase for as long as until only the best males remain (Whitehead & Mann, 2000). Mating groups are unique compared to other groups because of their lack of swimming formation; tightly grouped structure with males crowding to get access to the females and a high frequency of re-entry leaps behavior display (Markowitz, 2004). It has also been discovered that it is possible for male dusky dolphins to form alliances with other males to increase their mating success (Markowitz, 2004).
Markowitz, T. M., Harlin, A. D., Würsig, B., & McFadden, C. J. (2004). Dusky dolphin foraging habitat: overlap with aquaculture in New Zealand. Aquatic Conservation: Marine and Freshwater Ecosystems, 14(2), pp 133-149.
Markowitz, T.M.; Markowitz, W.J.; and Morton, L.M. (2010). Mating habits of New Zealand dusky dolphins. In: Würsig, B., and Würsig, M. (eds), The Dusky Dolphin: Master Acrobat off Different Shores. Academic Press. Pp. 151–76
Parer, D. & Cook, E.P. “Dusky Dolphins in rough sea”. Photo. Arkive.org. Accessed date: 10 April 2013. <http://blog.arkive.org/2012/03/the-arkive-teams-favourite-species-ellie-dart/>
Pearson, H. C. (2009). Influences on dusky dolphin (Lagenorhynchus obscurus) fission-fusion dynamics in Admiralty Bay, New Zealand. Behavioral Ecology and Sociobiology, 63(10), 1437-1446.
Pusser, T. “Dusky Dolphin leaping.” Photo. Arkrive.org. Accessed date: 10 April 2013. <http://www.arkive.org/dusky-dolphin/lagenorhynchus-obscurus/#mediaCredit>
Whitehead, H. & Mann, J. (2000). Female reproductive strategies of cetaceans. In: Mann, J. (eds) Cetacean Societies. University of Chicago Press. Pp. 219–246.
Wursig, B. & Wursig, M. (1980). Behavior and ecology of the dusky dolphin, Lagenorhynchus obscurus, in the South Atlantic. Fish. Bull, 77, pp 871-890.