Influences on dusky dolphin (Lagenorhynchus obscurus) fission-fusion dynamics in Admiralty Bay, New Zealand

Pearson, Heidi C.

doi:10.1007/s00265-009-0821-7

Cited by 59 publications

(72 citation statements)

References 30 publications

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“…Such very small group sizes related to foraging have previously been suggested as a strategy to reduce scramble competition in bottlenose dolphins (Pearson, 2009). This means individuals distribute themselves among patches of resources to minimise competition (Gowans et al, 2007) and lower their time travelling between patches of food (Pearson, 2009). This way intraspecific competition is reduced, and individual fitness is increased (Würsig, 1986).…”

Section: Seasonal Variation In Foraging Behaviour and Group Sizementioning

confidence: 87%

Diurnal and Seasonal Variation in the Behaviour of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Vermeulen¹,

Holsbeek²,

Das³

2015

Aquat Mamm

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Diurnal and seasonal patterns in the behaviour of a small population of bottlenose dolphins were assessed in Bahía San Antonio (BSA), Patagonia, Argentina, between 2006 and 2011. Results indicated that dolphins used the study area mainly to rest, travel, and forage, with a marked diurnal and seasonal pattern in their activity. During the early morning, most dolphin groups were resting, while towards the afternoon and evening, surface feeding and social activities peaked. During winter, social activities and surface feeding increased notably; during summer, diving behaviour reached its peak, presumably associated with a tail-out/peduncledive foraging strategy. The observed seasonal variation in foraging strategies is hypothesised to be related to the seasonal behavioural changes of prey species in the area that are linked to spawning. The variation in group size further appears to reflect the regulation of feeding competition while reconfirming the low predation risk within the study area. Results of this study indicate the behavioural and social flexibility of bottlenose dolphins in BSA and suggest a link to the seasonal variations in prey availability. Considering the general bottlenose dolphin population declines in Argentina presumably related to prey depletion, it could be argued that the temporal occurrence of spawning shoals and a general low presence of other top predators directly and indirectly make this a favourable area for this population. Additional information is required to more comprehensively address this hypothesis. The information presented herein serves as vital baseline data for future conservation management protocols.

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Section: Seasonal Variation In Foraging Behaviour and Group Sizementioning

confidence: 87%

Diurnal and Seasonal Variation in the Behaviour of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Vermeulen¹,

Holsbeek²,

Das³

2015

Aquat Mamm

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show abstract

“…Mussel farm buoys and associated closely-spaced vertical lines extending to the seafloor appeared to restrict dolphins by acting as threedimensional obstructions. A previous study found that dolphins travelled less near mussel farms, suggesting that mussel farms may obstruct prey-finding capabilities (Pearson 2009). Our underwater observations indicated that mussel farms interfere with dolphin prey herding and capture behaviours.…”

Section: Discussionmentioning

confidence: 99%

“…Focal follows were conducted for dusky dolphin groups sighted while on survey or opportunistically while driving to/from a transect line according to methods described in Pearson (2009). We defined groups using the 10-m chain rule (Smolker et al 1992).…”

Section: Methodsmentioning

confidence: 99%

Avoidance of mussel farms by dusky dolphins (Lagenorhynchus obscurus) in New Zealand

Pearson

Vaughn-Hirshorn

Srinivasan

et al. 2012

New Zealand Journal of Marine and Freshwater Research

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We describe fine-scale interactions between dusky dolphins and mussel farms in Admiralty Bay, New Zealand. We examined dusky dolphin presence in nearshore mussel farms, coordinated feeding behaviours in and near mussel farms, and long-term changes in regional population abundance. Sampling methods included boat-based surveys, focal follows, underwater observations, and photoidentification. Correcting for area, dusky dolphins spent significantly less time inside mussel farms versus outside mussel farms and other nearshore areas (both PB0.001). Prey balls entered or moved adjacent to mussel farms during 2/52 feeding bouts, after which dusky dolphin feeding behaviour ceased. Total estimated abundance during winter 2005Á2006 was 712 (95% CI: 511Á1134) with a declining trend in annual abundance after 2003. Results suggest that: (1) dusky dolphins rarely use mussel farms; (2) mussel farms may hinder coordinated feeding strategies; and (3) the number of dusky dolphins using this foraging habitat varies between years and may be declining.

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“…A subset of data collected as part of a larger group of studies (Markowitz et al , 2010Vaughn et al 2007Vaughn et al , 2008Vaughn et al , 2010Pearson 2009) was examined to assess changes in dusky dolphin encounter rates in Admiralty Bay during 2001Á2006. We investigated oceanographic and climatic factors that could affect inter-annual dolphin encounter rate patterns.…”

Section: Introductionmentioning

confidence: 99%

Using climate downscaling to hypothesise impacts on apex predator marine ecosystem dynamics

Srinivasan

Pearson

Vaughn-Hirshorn

et al. 2012

New Zealand Journal of Marine and Freshwater Research

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Climate downscaling studies help to connect global predictions and projections with regional dynamics and generate a better understanding of past and future conditions. Adding ecological variables and trophic relationships into the climate equation is challenging since there are few clear connections. The present study is an exploratory data analysis to explain dusky dolphin (Lagenorhynchus obscurus) encounter rate patterns in Admiralty Bay, New Zealand. During 2001Á2006, dolphin encounter rate in winter decreased from 6 to 0.8 groups/h and the proportion of dolphin groups observed feeding decreased from 80% to 38% in Inner Admiralty Bay. These trends generally corresponded to cooler and moderate El Nin˜o Southern Oscillation years, lower sea surface height, southwesterly winds, increased surface mixing and decreased sea surface salinity. To fully grasp the significance of these relationships and potential impact(s) on dolphin population trends, directed long-term studies that synthesise dolphin, prey, water quality, anthropogenic pressures and climatic information into regional climate-ecosystem models are needed.

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Influences on dusky dolphin (Lagenorhynchus obscurus) fission-fusion dynamics in Admiralty Bay, New Zealand

Cited by 59 publications

References 30 publications

Diurnal and Seasonal Variation in the Behaviour of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Diurnal and Seasonal Variation in the Behaviour of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina

Avoidance of mussel farms by dusky dolphins (Lagenorhynchus obscurus) in New Zealand

Using climate downscaling to hypothesise impacts on apex predator marine ecosystem dynamics

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