@article {1561,
	title = {Alternative reproductive tactics and male-dimorphism in the horne beetle Onthophagus acuminatus (Coleoptera: Scarabaeidae)},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {41},
	year = {1997},
	month = {Aug},
	pages = {335-341},
	keywords = {alternative reproductive behavior, horned beetles, male competition, male dimorphism, Onthophagus},
	author = {Emlen, Douglas J.}
}
@article {1793,
	title = {Offensive and defensive sperm competition roles in the dung beetle Onthophagus taurus (Coleoptera: Scarabaeidea)},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {60},
	year = {2006},
	pages = {131-136},
	abstract = {Sperm competition is predicted to generate op- posing selection pressures on males. On one hand, selec- tion should favour {\textquoteleft}defensive{\textquoteright} adaptations that protect a male{\textquoteright}s ejaculate from displacement, while, on the other hand, selection should favour {\textquoteleft}offensive{\textquoteright} adaptations that overcome paternity assurance mechanisms of rivals. Here, we use the sterile male technique to assess sperm pre- cedence when a male dung beetle Onthophagus taurus mates in both a defensive (first male) and an offensive (second male) role. Significant variation in a male{\textquoteright}s sperm precedence (both P1 and P2) was detected, and an individual{\textquoteright}s defensive (P1) and offensive (P2) abilities were positively correlated. Thus, it appears that sexual selection simultaneously selects for {\textquoteleft}defensive{\textquoteright} and {\textquoteleft}of- fensive{\textquoteright} adaptations in O. taurus. We discuss a variety of male traits in O. taurus that potentially contribute to a male{\textquoteright}s ability to be successful whenmatinginan{\textquoteleft}of-fensive{\textquoteright} and a {\textquoteleft}defensive{\textquoteright} role. },
	keywords = {Defensive role, male genitalia, Offensive role, Onthophagus taurus, Sperm competition},
	author = {House, Clarissa M. and Simmons, Leigh W.}
}
@article {1815,
	title = {Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {41},
	year = {1997},
	month = {may},
	pages = {109-114},
	keywords = {beetle horns, fluctuating asymmetry, honest signalling, Onthophagus taurus, sexual selection},
	author = {Hunt, John and Simmons, Leigh W.}
}
@article {1816,
	title = {Patterns of parental provisioning covary with male morphology in a horned beetle (Onthophagus taurus) (Coleoptera: Scarabaeidae)},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {42},
	number = {6},
	year = {1998},
	note = {June, 1998ArticleEnglish},
	pages = {447-451},
	abstract = {Male dung beetles, Onthophagus taurus, are dimorphic for a secondary sexual trait, head horns. Horned males participate in the production of brood masses while hornless male do not. Here we examine the reproductive performance of females mated with males exhibiting alternative horn morphologies. We found that exposure to males may be costly for females in that it reduced the total number of brood masses produced. However, females paired with horned males produced significantly larger brood masses than females paired with hornless males or females producing broods alone. We discuss the possible selection pressures that may underly horn evolution in this genus.},
	keywords = {Animalia-, Animals-, Arthropoda-, Arthropods-, Coleoptera-: Insecta-, Insects-, Invertebrata-, Invertebrates-, male-, male-dimorphism, morphology-, Onthophagus-taurus [horned-beetle] (Coleoptera-): female-, parental-care-patter, Reproduction-},
	author = {Hunt, John and Simmons, Leigh W.}
}
@article {1821,
	title = {Optimal maternal investment in the dung beetle Onthophagus taurus?},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {55},
	year = {2004},
	pages = {302-312},
	abstract = {Optimal investment theory is based on the assumption that the proximate constraint acting on parental investment is resource based. A trade-off between per offspring investment and total investment seems intuitive. Consequently, a parent{\textquoteright}s investment strategy is expected to represent a trade-off between the benefits of investment for current offspring and the costs to future reproduction for parents. In this study, we provide clear evidence that the costs and benefits of maternal provisioning in the dung beetle Onthophagus taurus influence the amount of provisions provided by the mother. Horse dung is typically of a higher nutritional value than cow dung and females were shown to provide 20\% less dung to offspring when provisioning with horse dung. By reducing their investment per offspring and exhibiting a clear preference to provision offspring with horse dung, females were able to produce significantly more offspring. Females provisioning with horse dung received greater fitness returns per unit of investment and experienced lower provisioning costs, in terms of the minimum amount of dung required to produce a surviving offspring, than females provisioning with cow dung. Females provisioning in soil of low moisture content were found to have higher tunneling costs than those provi- sioning in soil of high moisture content, while the fitness returns per unit of investment did not differ. We adopted a marginal value theorem (MVT) approach to calculate the theoretical optimal level of investment for each dung type and for each soil moisture. Predicted levels of provision- ing were lower for horse dung than for cow dung and for moist soil than for dry soil. Therefore, the results of this study are in qualitative agreement with MVT predictions and provide empirical support for the proposal that females can adaptively adjust their level of investment in response to resource and/or habitat quality. However, the theoretically predicted optimal investment yielded a poor quantitative fit with our observed levels of investment, with females providing over twice the investment predicted by the MVT approach. We suggest that this difference may reflect either our inability in directly quantifying all the necessary costs and benefits of investment in O. taurus and/or the applicability of the underlying assumptions of MVT.},
	keywords = {Habitat quality, Onthophagus taurus, Optimal investment strategies, Parental care, Resource quality, {\textperiodcentered}},
	author = {Hunt, John and Simmons, Leigh W.}
}
@article {1858,
	title = {Optimal investment in sons and daughters when parents do not know the sex of their offspring},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {62},
	year = {2008},
	pages = {607-615},
	abstract = {Optimal parental i nvestment usually differs depending on the sex of the offspring. However, parents in most organisms cannot discriminate the sex of their young until those young are energetically independent. In a species with physical male{\textendash}male competition, males are often larger and usually develop sexual ornaments, so male offspring are often more costly to produce. However, Onthophagus dung beetles (Coleoptera; Scarabaeidae) are highly dimorphic in secondary sexual characters, but sexually monomorphic in body size, despite strong male{\textendash}male competition for mates. We demonstrate that because parents provide all resources required by their offspring before adulthood, O. atripennis exhibits no sexual size dimorphism irrespective of sexual selection pressure favoring sexual dimorphism. By con- structing a graphic model with three fitness curves (for sons, daughters, and expected fitness return for parents), we demonstrate that natural selection favors parents that provide both sons and daughters with the optimal amount of investment for sons, which is far greater than that for daughters. This is because the cost of producing small sons, that are unable to compete for mates, is far greater than the cost of producing daughters that are larger than necessary. This theoretical prediction can explain sexual dimorphism without sexual size dimorphism, widely observed in species with crucial parental care such as dung beetles and leaf- rolling beetles, and may provide an insight into the enigmatic relationship between sexual size dimorphism and sexual dimorphism.},
	keywords = {dung beetle, Onthophagus, Optimal investment, Sexual dimorphism, Sexual size dimorphism},
	author = {Kishi, Shigeki and Nishida, Takayoshi}
}
@article {1603,
	title = {Sperm competition and evidence of sperm fertilization patterns in the carrion ball-roller Canthon cyanellus cyanellus LeConte (Scarabaeidae: Scarabaeinae)},
	journal = {Behavioral Ecology and Sociobiology},
	volume = {59},
	year = {2005},
	pages = {38-43},
	abstract = {Field observation and laboratory experiments were conducted to investigate sperm competition and pat- terns of sperm fertilization under different experimental conditions in the carrion ball-roller beetle Canthon cyanel- lus cyanellus. Males in nature can mate with females whose spermathecae contains fertile sperm from other males. Sperm precedence was investigated using a visible genetic marker. The progeny of red (homozygous recessive) virgin females mated once with a red male and afterward, once with a green beetle (homozygous dominant) and vice versa, revealed that regardless of its color, the last male to mate fertilized c.a. 50\% of the eggs, suggesting strong sperm competition. Males were able to achieve higher levels of pa- ternity (more than 80\%) when mated ad libitum with previ- ously mated females, although large amount of variance in paternity does not exclude the possibility of first male sperm precedence or female cryptic choice. These results suggest that repeated mating and sperm replacement are the mech- anisms by which last males achieve sperm precedence.},
	keywords = {Canthon cyanellus, Fertilization patterns, Genetic marker, Scarabaeidae, Sperm competition},
	author = {Favila, Mario E and Nolasco, Janet and Chamorro Florescano, Ivette and Equihua, Miguel}
}
