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"Animal weapons."
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Prickly animals
\"Carefully leveled text and vibrant photographs introduce readers to prickly animals such as the sea urchin, hedgehog, porcupine, and thorny devil, and explore how they use spines to defend themselves against predators. Includes activity, glossary, and index.\"-- Provided by publisher.
Book
Muscle mass drives cost in sexually selected arthropod weapons
Sexually selected weapons often function as honest signals of fighting ability. If poor-quality individuals produce high-quality weapons, then receivers should focus on other, more reliable signals. Cost is one way to maintain signal integrity. The costs of weapons tend to increase with relative weapon size, and thereby restrict large weapons to high-quality individuals who can produce and maintain them. Weapon cost, however, appears to be unpredictably variable both within and across taxa, and the mechanisms underlying this variation remain unclear. We suggest variation in weapon cost may result from variation in weapon composition—specifically, differences in the amount of muscle mass directly associated with the weapon. We test this idea by measuring the metabolic cost of sexually selected weapons in seven arthropod species and relating these measures to weapon muscle mass. We show that individuals with relatively large weapon muscles have disproportionately high resting metabolic rates and provide evidence that this trend is driven by weapon muscle mass. Overall, our results suggest that variation in weapon cost can be partially explained by variation in weapon morphology and that the integrity of weapon signals may be maintained by increased metabolic cost in species with relatively high weapon muscle mass.
Journal Article
Horned animals
\"Carefully leveled text and vibrant photographs introduce readers to horned animals such as the kudu, yak, and cape buffalo, and explore how they use their horns to defend themselves against predators. Includes activity, glossary, and index.\"-- Provided by publisher.
Book
Population differences in the strength of sexual selection match relative weapon size in the Japanese rhinoceros beetle, Trypoxylus dichotomus (Coleoptera: Scarabaeidae)
Exaggerated weapons of sexual selection often diverge more rapidly and dramatically than other body parts, suggesting that relevant agents of selection may be discernible in contemporary populations. We examined the ecology, reproductive behavior, and strength of sexual selection on horn length in five recently diverged rhinoceros beetle (Trypoxylus dichotomus) populations that differ in relative horn size. Males with longer horns were better at winning fights in all locations, but the link between winning fights and mating success differed such that selection favored large males with long horns at the two long-horned populations, but was relaxed or nonexistent at the populations with relatively shorter horns. Observations of local habitat conditions and breeding ecology point to shifts in the relative abundance of feeding territories as the most likely cause of population differences in selection on male weapon size in this species. Comparisons of ecological conditions and selection strength across populations offer critical first steps toward meaningfully linking mating system dynamics, selection patterns, and diversity in sexually selected traits.
Journal Article
Venomous animals
\"Carefully leveled text and vibrant photographs introduce readers to venomous animals such as the cobra, stonefish, and flower urchin, and explore how they use venom to defend themselves against predators. Includes activity, glossary, and index.\"-- Provided by publisher.
Book
Fight intensity correlates with stronger and more mechanically efficient weapons in three species of Aegla crabs
In many species, individuals contest resources using specialized morphologies to overpower rivals, hereafter referred to as weapons. Despite their importance in fights, little is known about the selective forces affecting weapon evolution. This may be particularly important to understand why weapons are highly variable among species. Due to their role during fighting, we expect that whenever fighting becomes more important for individual fitness so should the intensity of selection on weapon strength and morphology (which affect the efficiency of a weapon during combat). If true, we expect species that fight more intensely to have stronger and more mechanically efficient weapons. We tested this idea using males of three species of Aegla crabs (A. longirostri, A. abtao, and A. denticulata) that vary in their fight intensity. We compared the muscle size, the mechanical advantage (a proxy for the efficiency of the movable finger of the claw), and the correlation between weapon biomechanics and overall weapon shape (a proxy for the efficiency of the entire claw) among the species. We found that species with more intense fights presented stronger claws, higher mechanical advantage, and less variation in the regression between biomechanics and overall shape. Interestingly, the species with the largest claws were not the most mechanically efficient, suggesting that weapon size is not the sole factor behind weapon evolution. We conclude that fight intensity might be an important factor affecting weapon biomechanics, which ultimately might lead to a better understanding of weapon evolution.
Journal Article
Electric animals
\"Carefully leveled text and vibrant photographs introduce readers to electric animals such as the stargazer, torpedo ray, electric eel, and and explore how they use electricity to defend themselves against predators. Includes activity, glossary, and index.\"-- Provided by publisher.
Book
Mutual assessment during ritualized fighting in mantis shrimp (Stomatopoda)
Safe and effective conflict resolution is critical for survival and reproduction. Theoretical models describe how animals resolve conflict by assessing their own and/or their opponent's ability (resource holding potential, RHP), yet experimental tests of these models are often inconclusive. Recent reviews have suggested this uncertainty could be alleviated by using multiple approaches to test assessment models. The mantis shrimp Neogonodactylus bredini presents visual displays and ritualistically exchanges high-force strikes during territorial contests. We tested how N. bredini contest dynamics were explained by any of three assessment models—pure self-assessment, cumulative assessment and mutual assessment—using correlations and a novel, network analysis-based sequential behavioural analysis. We staged dyadic contests over burrow access between competitors matched either randomly or based on body size. In both randomly and size-matched contests, the best metric of RHP was body mass. Burrow residency interacted with mass to predict outcome. Correlations between contest costs and RHP rejected pure self-assessment, but could not fully differentiate between cumulative and mutual assessment. The sequential behavioural analysis ruled out cumulative assessment and supported mutual assessment. Our results demonstrate how multiple analyses provide strong inference to tests of assessment models and illuminate how individual behaviours constitute an assessment strategy.
Journal Article
The king of sting
\"Wildlife expert Coyote Peterson brings his 12.5 million YouTube subscribers and legions of kid fans a highly designed, full-color exploration of his 'Sting Zone' adventure series, culminating in his ... encounter with the 'King of Sting'--the executioner wasp\"-- Provided by publisher.
Book
Selection on an extreme weapon in the frog-legged leaf beetle (Sagra femorata)
Biologists have been fascinated with the extreme products of sexual selection for decades. However, relatively few studies have characterized patterns of selection acting on ornaments and weapons in the wild. Here, we measure selection on a wild population of weapon-bearing beetles (frog-legged leaf beetles: Sagra femorata) for two consecutive breeding seasons. We consider variation in both weapon size (hind leg length) and in relative weapon size (deviations from the population average scaling relationship between hind leg length and body size), and provide evidence for directional selection on weapon size per se and stabilizing selection on a particular scaling relationship in this population. We suggest that whenever growth in body size is sensitive to external circumstance such as nutrition, then considering deviations from population-level scaling relationships will better reflect patterns of selection relevant to evolution of the ornament or weapon than will variation in trait size per se. This is because traitsize versus body-size scaling relationships approximate underlying developmental reaction norms relating trait growth with body condition in these species. Heightened condition-sensitive expression is a hallmark of the exaggerated ornaments and weapons favored by sexual selection, yet this plasticity is rarely reflected in the way we think about—and measure—selection acting on these structures in the wild.
Journal Article