scholarly journals Near-Shore Distribution of Heaviside's (Cephalorhynchus heavisidii) and Dusky Dolphins (Lagenorhynchus obscurus) at the Southern Limit of their Range in South Africa

2010 ◽  
Vol 45 (1) ◽  
pp. 78-91 ◽  
Author(s):  
S.H. Elwen ◽  
M. Thornton ◽  
D. Reeb ◽  
P.B. Best
Keyword(s):  
South Africa ◽  
Southern Limit ◽  
Lagenorhynchus Obscurus ◽  
Near Shore ◽  
Dusky Dolphins

Implications for the age of South African Devonian rocks in which Tropidoleptus (Brachiopoda) has been found

1983 ◽  
Vol 120 (1) ◽  
pp. 51-58 ◽  
Author(s):  
A. J. Boucot ◽  
C. H. C. Brunton ◽  
J. N. Theron
Keyword(s):  
South Africa ◽  
North America ◽  
South African ◽  
Early Carboniferous ◽  
Fossil Plants ◽  
Geological Time ◽  
Marine Sedimentation ◽  
History Of ◽  
Near Shore ◽  
First Time

SummaryThe Devonian brachiopod Tropidoleptus is recognized for the first time in South Africa. It is present in the lower part of the Witteberg Group at four widely separated localities. Data regarding the stratigraphical range of the genus elsewhere, combined with information on recently described fossil plants and vertebrates from underlying strata of the upper Bokkeveld Group, suggest that a Frasnian or even Givetian age is reasonable for the lower part of the Witteberg Group. The recognition of Tropidoleptus in a shallow water, near-shore, molluscan association, at the top of the South African marine Devonian sequence, is similar to its occurrence in Bolivia, and suggests a common Malvinokaffric Realm history of shallowing, prior to later Devonian or early Carboniferous non-marine sedimentation. It is noteworthy that Tropidoleptus is now known to occur in ecologically suitable environments around the Atlantic, but is absent from these same environments in Asia and Australia. Tropidoleptus is an excellent example of dispersal in geological time — first appearing in northern Europe and Nova Scotia, then elsewhere in eastern North America and North Africa, followed by South America and South Africa, while continuing in North America.

scholarly journals Birds and mammals off the northern coast of Argentina: first report of an association between birds and a feeding Pygmy Right Whale Caprea marginata

Ornis Svecica ◽  
2013 ◽  
Vol 23 (3–4) ◽  
pp. 117-122
Author(s):  
Henrik Kylin
Keyword(s):  
Cold Water ◽  
Northern Coast ◽  
Feeding Groups ◽  
La Plata ◽  
Lagenorhynchus Obscurus ◽  
Right Whale ◽  
Pachyptila Belcheri ◽  
Dusky Dolphins ◽  
Oceanites Oceanicus ◽  
Eleven Species

When the icebreaker Oden passed between 39°36'S, 57°46'W and 39°59'S, 58°11'W on 20 November 2007, an extraordinary observation was made. A feeding Pygmy Right Whale Caprea marginata, a species rarely seen, was attended by eight Grey Phalaropes Phalaropus fulicarius, two Slender-billed Prions Pachyptila belcheri, and four Wilson’s Storm Petrels Oceanites oceanicus. The birds returned to feed around the head of the whale every time it surfaced, presumably copepod plankton straining out between the baleen. The site is off Rio de la Plata estuary where nutrient rich freshwater meets cold water of the Malvinas (Falkland) Current, creating a hotspot with high levels of plankton food. The conditions were extraordinarily favourable for observation with a calm sea, no wind and only a very weak swell. Six multispecies feeding groups were seen with a total of 42 species of birds, eleven species of whales, dolphins and porpoises, and three species of seals. Dusky Dolphins Lagenorhynchus obscurus and Great Shearwaters Puffinus gravis were predominant in the groups.

Development of leaps in dusky dolphin (Lagenorhynchus obscurus) calves

Behaviour ◽  
2014 ◽  
Vol 151 (11) ◽  
pp. 1555-1577 ◽  
Author(s):  
Sierra Deutsch ◽  
Heidi Pearson ◽  
Bernd Würsig
Keyword(s):  
Adaptive Significance ◽  
Behavioral State ◽  
Lagenorhynchus Obscurus ◽  
Frequency Changes ◽  
Positive Correlations ◽  
Dusky Dolphins ◽  
Dusky Dolphin ◽  
The Relationship ◽  
Early Late ◽  
Age Category

Leaping is a highly conspicuous behavior in cetaceans that may function in cooperative hunting and social bonding, thereby converging with forms of intra-specific communication present in other social mammals. However, few studies have analyzed the ontogeny of leaping, an important aspect in determining the adaptive significance of this behavior. The objective of our study was to quantify the ontogeny of leaping in dusky dolphins, a highly acrobatic species that engages in a variety of aerial displays. We tested the hypotheses that: (1) leap frequency changes with calf age, (2) frequency of leap type varies with calf age and (3) frequency of leap type varies by behavioral state. Data were collected off Kaikoura, New Zealand through boat-based group focal follows of nursery groups from October 2006–May 2007. We analyzed data from 73 nursery group encounters according to age category (young calf, yearling) and season (early, late). Early young calves leapt less frequently than late young calves (), but leap frequency did not appear to differ among older calves. Calves learned noisy leaps first, followed by clean leaps, then coordinated leaps, and finally acrobatic leaps as indicated by the positive correlations between week (i.e., calf age) and frequency of clean (), acrobatic () and coordinated () leaps. The relationship between behavioral state and frequency of leap type was not significant. These results indicate that nursery groups represent an important environment for healthy physical and social development of calves. Furthermore, while calves appear to learn the mechanics of leaping individually, they appear to learn the context in which the leaps are performed from conspecifics. This indicates that, as for other socially-complex mammals such as other cetaceans, primates, and social carnivores, social learning may be an important component in the ontogeny of dusky dolphin behavior.

Acoustics of Dusky Dolphins (Lagenorhynchus obscurus)

2010 ◽  
pp. 75-97 ◽  
Author(s):  
Whitlow W.L. Au ◽  
Marc O. Lammers ◽  
Suzanne Yin
Keyword(s):  
Lagenorhynchus Obscurus ◽  
Dusky Dolphins

Unravelling the function of dolphin leaps using the dusky dolphin (Lagenorhynchus obscurus) as a model species

Behaviour ◽  
2017 ◽  
Vol 154 (5) ◽  
pp. 563-581 ◽  
Author(s):  
Heidi C. Pearson
Keyword(s):  
Social Facilitation ◽  
Foraging Behaviour ◽  
Prey Capture ◽  
Foraging Efficiency ◽  
Lagenorhynchus Obscurus ◽  
The Social ◽  
Negative Effect ◽  
Dusky Dolphins ◽  
Dusky Dolphin ◽  
Positive Effect

The prevalence of leaping across delphinids indicates it has an adaptive benefit. I examined leaping behaviour in dusky dolphins (Lagenorhynchus obscurus) according to signalling, social facilitation, and prey capture hypotheses. I quantified the effect of leaping on group behaviour and fission-fusion and the behavioural context of leaping. I observed dolphins in Admiralty Bay, New Zealand during 171 focal follows totalling 157 h. Data were analysed using generalized estimating equations. Clean leaping had a positive effect on party fission () and foraging behaviour (). Coordinated leaping caused a short-term wane in foraging behaviour () and had a positive effect on party fusion (). Noisy leaping had a negative effect on perpetuating resting and traveling cessation (both ). The signalling hypothesis was the most strongly supported. The social facilitation and prey capture hypotheses were moderately supported. Leaping may provide adaptive benefits such as reduced scramble competition, increased foraging efficiency, and social bonding.

scholarly journals Copulation rate declines with mating group size in dusky dolphins (Lagenorhynchus obscurus)

2015 ◽  
Vol 93 (6) ◽  
pp. 503-507 ◽  
Author(s):  
D.N. Orbach ◽  
G.G. Rosenthal ◽  
B. Würsig
Keyword(s):  
New Zealand ◽  
Group Size ◽  
Energy Costs ◽  
Indirect Benefits ◽  
Lagenorhynchus Obscurus ◽  
Mating Group ◽  
Copulation Rate ◽  
Mating Opportunities ◽  
Dusky Dolphins ◽  
Time And Energy

Males in polygamous species often engage in intrasexual competition for mates. If females actively evade mating attempts, it may benefit males to cooperate to restrict female movement, as has been found in some mammals. We tested if male dusky dolphins (Lagenorhynchus obscurus (Gray, 1828)) cooperate or compete during group mating chases. If they cooperate, then the per-male probability of copulating should increase with group size; if they compete, then the probability should decrease. We followed mating groups by boat during the breeding season (October 2013 – January 2014) off Kaikoura, New Zealand. The copulation rate per male decreased with increasing group size and with the number of noncopulating males in proximity to a copulating female. Male dusky dolphins have multiple mates and appear to use sperm and exploitative scramble competition. Males may remain in mating groups despite competition because there are alliances within the groups, they are unable to exclude rivals from joining a group, the time and energy costs of searching for unescorted females exceed the costs of reduced mating opportunities in a group, they receive other direct or indirect benefits that offset the costs of reduced mating opportunities, or they are in the group largely for social learning rather than procreation.

Reproduction of Dusky Dolphins, Lagenorhynchus obscurus, from Coastal Peru

1994 ◽  
Vol 75 (4) ◽  
pp. 1054-1062 ◽  
Author(s):  
K. Van Waerebeek ◽  
A. J. Read
Keyword(s):  
Lagenorhynchus Obscurus ◽  
Dusky Dolphins ◽  
Coastal Peru
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