Foraging segregation in tropical and polar seabirds: Testing the Intersexual Competition Hypothesis

2013 ◽  
Vol 449 ◽  
pp. 186-193 ◽  
Author(s):  
Patrícia L. Mancini ◽  
Alexander L. Bond ◽  
Keith A. Hobson ◽  
Leandro S. Duarte ◽  
Leandro Bugoni
Keyword(s):  
Competition Hypothesis ◽  
Intersexual Competition

scholarly journals Temporal patterns in prey size between sexes in a raptor with extreme size dimorphism: testing the intersexual competition hypothesis using web-sourced photographs

2021 ◽  
Author(s):  
Connor T. Panter ◽  
arjun amar
Keyword(s):  
Sexual Dimorphism ◽  
Prey Size ◽  
Ingestion Rate ◽  
Size Dimorphism ◽  
Accipiter Nisus ◽  
Competition Hypothesis ◽  
Nestling Period ◽  
Dietary Niche ◽  
Reversed Sexual Dimorphism ◽  
Intersexual Competition

In most vertebrates, males are larger than females. For raptors, sexual size dimorphism is reversed, with females being larger. Reversed sexual dimorphism (RSD) in raptors is strongly linked to diet, with species feeding on the most agile prey, for example bird-eating raptors, showing the greatest size differences between the sexes. Hypotheses for reversed sexual dimorphism (RSD) include the ‘intersexual competition’ hypothesis, which proposes that RSD evolved to enable pairs to expand their dietary niche (taking a wider range of prey sizes) during the nestling period when both sexes occupy and hunt within the same territory, and thereby reduce competition between the sexes. If intersexual competition is responsible for the evolution of RSD, we predict that sex-related differences in prey size and dietary niche breadth will be particularly pronounced during the nestling period (cf. the non-nestling period). We explore this prediction in the highly dimorphic Eurasian Sparrowhawk (Accipiter nisus), which displays the largest degree of RSD of all raptors, using web-sourced photographs to identify diet throughout the entire year. We analysed 666 photographs of sparrowhawks on their prey over time. In contrast to our predictions, sex-specific prey sizes were most similar during the nestling period compared to any other time of the year. Both males and females reduced the size of their prey during the nestling period which may be a result of the ‘ingestion rate’ hypothesis, or a strategy employed to prevent hunting-related injuries during this critical period of the year.

Intersexual and Intrasexual Competition and Their Relation to Jealousy

2019 ◽  
pp. 214-236
Author(s):  
Abraham P. Buunk ◽  
Karlijn Massar ◽  
Pieternel Dijkstra ◽  
Ana María Fernández
Keyword(s):  
Sex Differences ◽  
Individual Differences ◽  
Menstrual Cycle ◽  
Attachment Styles ◽  
Mate Guarding ◽  
Intrasexual Competition ◽  
Online Infidelity ◽  
Intersexual Competition

This chapter discusses sex differences in intersexual competition and describes particularly the consequences of such competition for conflict between the sexes, as well as for sex differences in mate guarding and, relatedly, in the types of infidelity that evoke jealousy, including online infidelity. It also discusses individual differences in jealousy as related to attachment styles and describes the effects of height, hormones, and the menstrual cycle on jealousy. Next, the chapter moves on to intrasexual competition and discusses, among other topics, intrasexual competition among men and among women, the role of sex differences in rival characteristics in evoking jealousy, the role of attachment styles and hormones, and individual differences in intrasexual competitiveness.

scholarly journals Wolf, Canis lupus, Pup Mortality: Interspecific Predation or Non-Parental Infanticide?

2011 ◽  
Vol 125 (2) ◽  
pp. 158 ◽  
Author(s):  
A. David M. Latham ◽  
Stan Boutin
Keyword(s):  
Canis Lupus ◽  
Resource Competition ◽  
The Other ◽  
Gray Wolf ◽  
Gps Collar ◽  
Competition Hypothesis ◽  
Interspecific Predation ◽  
Pup Mortality ◽  
First Time

A breeding male Gray Wolf, Canis lupus, equipped with a GPS collar was documented going to the den site of another Gray Wolf pack. This trip was coincident with an attack on the den of the other pack and the occurrence of a dead and partially consumed Gray Wolf pup at the same location. We present two possible explanations - interspecific predation and non-parental infanticide - to account for this observation. Because the Gray Wolf with the GPS collar and his mate were first-time breeders and were attempting to establish a territory space of their own, we speculate that, based on the available evidence, this observation most likely represents a case of non-parental infanticide that fits the predictions of the resource competition hypothesis.

Flexibility of nuptial colouration in a unique ecotype of Threespine Stickleback (Gasterosteus aculeatus)

2021 ◽  
Author(s):  
Rachel Corney ◽  
Anne Haley ◽  
Laura Weir
Keyword(s):  
Breeding Season ◽  
Gasterosteus Aculeatus ◽  
Colour Change ◽  
Threespine Stickleback ◽  
Relative Role ◽  
Mate Quality ◽  
Breeding Seasons ◽  
Potential Signal ◽  
Intersexual Competition

Nuptial colouration in animals may serve as a signal of competitor and/or mate quality during breeding. In many temperate fishes, nuptial colouration develops during discrete breeding seasons and is a target of sexual selection. We examine nuptial colouration and behaviour of a unique ecotype of Threespine Stickleback (Gasterosteus aculeatus Linnaeus, 1758), wherein males turn from dull brown-grey to pearlescent white during the breeding season. The main goal of this work was to determine the relative role of white colouration in intersexual competition and mate choice. In a combination of a field and laboratory work, we found that males are brightest white when engaging in courtship activities in the presence of a female; this indicates that white colouration may be primarily related to enhancing signalling during mate attraction. White colouration intensity increased as the breeding season progressed and may be related to an influx of conspecifics. Colour change from cryptic grey to bright white occurred rapidly (< 90 seconds) and may be deployed to enhance behavioural signals. We conclude that bright white colouration in the white ecotype is a potential signal of mate quality and may have evolved from a previously existing capacity for colour plasticity in common Threespine Stickleback.

scholarly journals Multi-scale habitat use analysis and interspecific Ecology of the Critically Endangered Black-breasted Puffleg Eriocnemis nigrivestis

2015 ◽  
Vol 25 (4) ◽  
pp. 479-488 ◽  
Author(s):  
ESTEBAN A. GUEVARA ◽  
ELISA BONACCORSO ◽  
JOOST F. DUIVENVOORDEN
Keyword(s):  
Habitat Use ◽  
Habitat Degradation ◽  
Physiological Stress ◽  
Selection Process ◽  
Habitat Model ◽  
Critically Endangered ◽  
Use Patterns ◽  
Multi Scale ◽  
The North ◽  
Competition Hypothesis

SummaryThe Black-breasted Puffleg Eriocnemis nigrivestis is a hummingbird endemic to Ecuador and considered Critically Endangered, given its limited distribution, low population numbers, and ongoing habitat degradation. We investigated habitat use patterns using landscape and microhabitat variables. In addition, we explored a previously postulated competition hypothesis involving the Black-breasted Puffleg and the Gorgeted Sunangel Heliangelus strophianus. Our results suggest that landscape variables may play a role in the habitat selection process; specifically the distance to nearest forest border seems to have a significant effect on our habitat model. We speculate that, as the species is known to perform seasonal movements, the avoidance of forest border might reduce the physiological stress caused by altitudinal migration. At microhabitat level, Black-breasted Puffleg seems not sensitive to forest structure variables. Our findings suggest that ensuring forest tract connectivity, between the altitudinal extremes of the species’ range at the north-western flanks of the Pichincha volcano, might be crucial for survival of the species during its annual cycle. However, non-metric multidimensional scaling (NMDS) indicates that Black-breasted Puffleg and the Gorgeted Sunangel do not overlap spatially, but this finding is not conclusive considering our field observations.

Competition, Constituencies, and Welfare Policies in American States

1979 ◽  
Vol 73 (2) ◽  
pp. 414-429 ◽  
Author(s):  
Edward T. Jennings
Keyword(s):  
Electoral Politics ◽  
Party Systems ◽  
State Policies ◽  
Welfare Policies ◽  
Economic Class ◽  
American States ◽  
Competition Hypothesis ◽  
Different Types ◽  
Party Characteristics ◽  
Generous Welfare

This article examines the logic underlying standard formulations of the interparty competition hypothesis in the comparative state policy literature, suggests a reformulation which provides some new insights into the conditions under which we might expect state policies to change as a result of party characteristics, and undertakes an initial test of the reformulation.I develop two propositions. The first is that party systems which divide the electorate along economic class lines will generate more generous welfare policies than party systems which do not so organize the electorate. The second is that within states with class-based electoral systems, change in welfare policy will be positively related to the degree to which the party or faction with lower- and working-class support gains control of government.I analyze welfare policies of selected American states for the period 1938 to 1970. My analysis suggests that (1) the class basis of electoral politics does influence state welfare policies and (2) parties and factions which differ in their constituency bases produce different types of policies when they are in control of government.

scholarly journals The effect of interspecific competition on habitat selection by voles: an experimental approach

2001 ◽  
Vol 79 (1) ◽  
pp. 110-120 ◽  
Author(s):  
Yu-teh K Lin ◽  
George O Batzli
Keyword(s):  
Habitat Selection ◽  
Interspecific Competition ◽  
Field Experiments ◽  
Dispersal Ability ◽  
Habitat Segregation ◽  
Vegetative Cover ◽  
Prairie Voles ◽  
Meadow Voles ◽  
Competition Hypothesis ◽  
Central Illinois

Both meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster) prefer habitats with high vegetative cover, but in east-central Illinois, meadow voles tend to be associated with higher cover and prairie voles with lower cover. The competition hypothesis proposes that this pattern of habitat segregation reflects the effects of interspecific competition on habitat selection. To test this hypothesis we conducted field experiments that allowed the two species to select from among several habitats when alone and when together. We expected to find a lower proportion of each species in the habitat most associated with the other species, and a negative correlation between the demography and density of each species and the density of the competing species, but this was not the case. Inter specific competition did affect movement patterns of prairie voles. In the presence of meadow voles, net movement (immigration minus emigration) of prairie voles in high-cover habitats decreased and net dispersal of individuals from high- to low-cover habitats increased. Thus, our results indicated only a weak effect of competition on habitat selection. We suggest that other mechanisms, such as differences in habitat preference (or tolerance), differences in dispersal ability, and the advantage of first residency, need to be considered in conjunction with interspecific competition to explain the habitat segregation observed in these species.

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