Group size and activity patterns of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) during spring migration in Lancaster Sound

1991 ◽  
Vol 69 (6) ◽  
pp. 1630-1635 ◽  
Author(s):  
Susan E. Cosens ◽  
Larry P. Dueck
Keyword(s):  
Group Size ◽  
Predator Avoidance ◽  
Additional Data ◽  
Activity Patterns ◽  
Size Variation ◽  
Spring Migration ◽  
Delphinapterus Leucas ◽  
Interspecific Differences ◽  
Monodon Monoceros ◽  
Grouping Patterns

Aerial surveys of belugas (Delphinapterus leucas) and narwhals (Monodon monoceros) were conducted in Lancaster Sound and northern Admiralty Inlet, N.W.T., during spring migration in 1987. Interspecific differences in grouping patterns and associated behaviour were observed. Group size and behaviour varied with ice type and state of breakup but patterns of variation differed between species. Behaviour of narwhals but not of belugas varied significantly with group size. Variation in group size and activity suggests that aggregation patterns are not related to predator avoidance strategies. Additional data are needed to test hypotheses about grouping patterns and behaviour in relation to prey distribution.

Moonlight Avoidance Behavior in Leach's Storm-Petrels as a Defense against Slaty-Backed Gulls

The Auk ◽  
1986 ◽  
Vol 103 (1) ◽  
pp. 14-22 ◽  
Author(s):  
Yutaka Watanuki
Keyword(s):  
Predator Avoidance ◽  
Full Moon ◽  
Activity Patterns ◽  
Predation Rate ◽  
Activity Levels ◽  
Nocturnal Activity ◽  
Oceanodroma Leucorhoa ◽  
Risk Of Predation ◽  
Reduced Activity ◽  
Moonlight Avoidance

Abstract Diurnal activity patterns of Leach's Storm-Petrels (Oceanodroma leucorhoa) and Slaty-backed Gulls (Larus schistisagus) were investigated. The petrels reduced activity in moonlight in May and June when the predation rate by gulls was relatively high. Petrel activity levels were inversely correlated with light intensities and the corresponding risk of predation by the gull. This suggests that nocturnal activity and moonlight avoidance by the petrel in its colony are an effective defense against diurnal predators. Activity synchronization of the petrel was most marked during the full moon, further supporting the predator-avoidance hypothesis.

Habitat use, temporal activity patterns and foraging behaviour of raptors in the south-west of the Northern Territory, Australia

2001 ◽  
Vol 28 (4) ◽  
pp. 365 ◽  
Author(s):  
Tom Aumann
Keyword(s):  
Habitat Use ◽  
Foraging Behaviour ◽  
Activity Patterns ◽  
Northern Territory ◽  
Diel Activity ◽  
The South ◽  
Interspecific Differences ◽  
South West ◽  
Diel Activity Patterns ◽  
Vegetation Structures

On the basis of opportunistic observations, the preferred habitats of diurnal raptors in the south-west of the Northern Territory are quantified in terms of their vegetation structures and composition, and linked with foraging methods and information on local diets. Broad interspecific differences in diel activity patterns are also described. The evidence suggests that raptor species in this part of arid Australia differ with respect to their foraging times, habitats and methods, and that these differences relate to their partitioning of food resources.

scholarly journals Influence of seasonality, group size, and presence of a congener on activity patterns of howler monkeys

2012 ◽  
Vol 93 (3) ◽  
pp. 645-657 ◽  
Author(s):  
Ilaria Agostini ◽  
Ingrid Holzmann ◽  
Mario S. Di Bitetti
Keyword(s):  
Group Size ◽  
Activity Patterns ◽  
Howler Monkeys

scholarly journals Effects of group size on the threat-sensitive response to varying concentrations of chemical alarm cues by juvenile convict cichlids

2006 ◽  
Vol 84 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Grant E Brown ◽  
Tony Bongiorno ◽  
Daniel M DiCapua ◽  
Laura I Ivan ◽  
Ellie Roh
Keyword(s):  
Group Size ◽  
Predator Avoidance ◽  
Response Pattern ◽  
Distilled Water ◽  
Alarm Cues ◽  
Response Patterns ◽  
Alarm Cue ◽  
Convict Cichlids ◽  
Graded Response ◽  
Chemical Alarm Cues

The threat-sensitive predator avoidance model predicts that prey should balance the intensity of antipredator responses against perceived predation risk, resulting in a graded response pattern. Recent studies have demonstrated considerable interspecific variation in the intensity of threat-sensitive response patterns, ranging from strongly graded to relatively nongraded or "hypersensitive" threat-sensitive response patterns. Here, we test for intraspecific plasticity in threat-sensitive responses by varying group size. We exposed juvenile convict cichlids, Archocentrus nigrofasciatus (Günther, 1867), as individuals or in small (groups of three) or large (groups of six) shoals to a series of dilutions of conspecific chemical alarm cues and a distilled water control. Singleton cichlids exhibited significant reductions in time spent moving and in frequency of foraging attempts (relative to distilled water controls) when exposed to a 12.5% dilution of conspecific alarm cue, with no difference in response intensity at higher stimulus concentrations, suggesting a nongraded (hypersensitive) response pattern. Small shoals exhibited a similar response pattern, but at a higher response threshold (25% dilution of stock alarm cue solution). Large shoals, however, exhibited a graded response pattern. These results suggest that group size influences the trade-off between predator avoidance and other fitness related activities, resulting in flexible threat-sensitive response patterns.

Mating ecology of beluga (Delphinapterus leucas) and narwhal (Monodon monoceros)as estimated by reproductive tract metrics

2014 ◽  
Vol 31 (2) ◽  
pp. 479-500 ◽  
Author(s):  
Trish C. Kelley ◽  
Robert E. A. Stewart ◽  
David J. Yurkowski ◽  
Anna Ryan ◽  
Steven H. Ferguson
Keyword(s):  
Reproductive Tract ◽  
Delphinapterus Leucas ◽  
Monodon Monoceros

Observations on Distribution and Intraspecific Variation in Pigmentation Patterns of Odontocete Cetacea in the Western North Atlantic

1973 ◽  
Vol 30 (8) ◽  
pp. 1111-1130 ◽  
Author(s):  
M. C. Mercer
Keyword(s):  
Intraspecific Variation ◽  
North Atlantic ◽  
Intraspecific Variability ◽  
Delphinapterus Leucas ◽  
Phocoena Phocoena ◽  
Western Atlantic ◽  
Stenella Coeruleoalba ◽  
West Greenland ◽  
Monodon Monoceros

This paper comprises sight records for nine species and morphometries, color descriptions, and miscellaneous notes on the food and parasites of seven species of small odontocetes observed from West Greenland to Florida 1967–72. Of interest are the first western Atlantic extralimital record of Monodon monoceros, first Newfoundland records of Stenella coeruleoalba, and extralimital records of Delphinapterus leucas from Newfoundland. Intraspecific variability is described in the pigmentation patterns of Phocoena phocoena.

Eye size variation reflects habitat and daily activity patterns in colubrid snakes

2012 ◽  
Vol 273 (8) ◽  
pp. 883-893 ◽  
Author(s):  
Yang Liu ◽  
Li Ding ◽  
Juan Lei ◽  
Ermi Zhao ◽  
Yezhong Tang
Keyword(s):  
Daily Activity ◽  
Activity Patterns ◽  
Size Variation ◽  
Eye Size ◽  
Daily Activity Patterns

scholarly journals Do Peers Affect Student Achievement? Evidence from Canada Using Group Size Variation

2010 ◽  
Author(s):  
Vincent Boucher ◽  
Yann Bramoulle ◽  
Habiba Djebbari ◽  
Bernard Fortin
Keyword(s):  
Student Achievement ◽  
Group Size ◽  
Size Variation

scholarly journals The Infertility Trap: The Fertility Costs of Group-Living in Mammalian Social Evolution

2021 ◽  
Vol 9 ◽  
Author(s):  
Robin I. M. Dunbar ◽  
Susanne Shultz
Keyword(s):  
Group Size ◽  
Social Evolution ◽  
Low Cost ◽  
Social Groups ◽  
Group Living ◽  
The Other ◽  
Risk Averse ◽  
Limit Group ◽  
Grouping Patterns ◽  
Environmental Demands

Mammal social groups vary considerably in size from single individuals to very large herds. In some taxa, these groups are extremely stable, with at least some individuals being members of the same group throughout their lives; in other taxa, groups are unstable, with membership changing by the day. We argue that this variability in grouping patterns reflects a tradeoff between group size as a solution to environmental demands and the costs created by stress-induced infertility (creating an infertility trap). These costs are so steep that, all else equal, they will limit group size in mammals to ∼15 individuals. A species will only be able to live in larger groups if it evolves strategies that mitigate these costs. We suggest that mammals have opted for one of two solutions. One option (fission-fusion herding) is low cost but high risk; the other (bonded social groups) is risk-averse, but costly in terms of cognitive requirements.

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