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Males of a strongly polygynous species consume more poisonous food than females.

Bravo C, Bautista LM, García-París M, Blanco G, Alonso JC - PLoS ONE (2014)

Bottom Line: The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness.A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females.Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.

View Article: PubMed Central - PubMed

Affiliation: Department of Evolutionary Ecology, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Madrid, Spain.

ABSTRACT
We present evidence of a possible case of self-medication in a lekking bird, the great bustard Otis tarda. Great bustards consumed blister beetles (Meloidae), in spite of the fact that they contain cantharidin, a highly toxic compound that is lethal in moderate doses. In addition to anthelminthic properties, cantharidin was effective against gastrointestinal bacteria that cause sexually-transmitted diseases. Although both sexes consumed blister beetles during the mating season, only males selected them among all available insects, and ingested more and larger beetles than females. The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness. This plausibly explains the intense cloaca display males perform to approaching females, and the meticulous inspection females conduct of the male's cloaca, a behaviour only observed in this and another similar species of the bustard family. A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females. Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.

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A great bustard male in courtship display shows its cloaca to prospective females (A–B; Photographs: C. Palacín).Detail of white feathers of cloaca during display of male great bustard (C; Photographs: F. Kovacs). Detail of other bird with an Otiditaenia conoides in extending from the cloaca (D; Photograph: C. Palacín). Detail of a Otiditaenia conoides individual separate from the body bird (E; Photograph: A. Lucas). Black arrows show the cloaca position.
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pone-0111057-g002: A great bustard male in courtship display shows its cloaca to prospective females (A–B; Photographs: C. Palacín).Detail of white feathers of cloaca during display of male great bustard (C; Photographs: F. Kovacs). Detail of other bird with an Otiditaenia conoides in extending from the cloaca (D; Photograph: C. Palacín). Detail of a Otiditaenia conoides individual separate from the body bird (E; Photograph: A. Lucas). Black arrows show the cloaca position.

Mentions: Another appealing hypothesis is that consumption of blister beetles could also enhance the attractiveness of males to females by reducing their parasite load. This would counter-balance the risk of cantharidin poisoning [25] with reproductive benefits. In addition, males could benefit from cantharidin during the display season, when they may be particularly vulnerable to infections due to their presumably depressed immune system associated to their strenuous investment in sexual display [26],[27]. This hypothesis predicts a male-biased blister beetle consumption (i.e., both sexes would consume blister beetles as a healing or prophylactic agent, but males with potential to attract females should consume them also to enhance their body condition and mating opportunities). Previous studies have shown that age, weight, and display effort are the main predictors of male mating success in this species, and that whiskers and neck plumage are reliable indicators of male age and weight [13],[14]. However, the function of the meticulous inspection females perform of the male's cloaca prior to copulation is still unknown. A male's sexual display consists of a series of extravagant body postures and movements that end, when an interested female approaches, with a reiterative and almost obstinate exhibition of the cloaca, which is fully surrounded by pure white feathers that allow an easy detection of possible parasites or their remains [28],[29] (Fig. 2 A–C). Female bustards are extremely choosy during mating, accepting on average only one of ten males attempting to copulate with them [13]. Females closely inspect the male's cloaca, pecking around it as an essential part of mate selection, after which they decide whether to mate or not with the male [30],[31]. Our interpretation of this cloaca pecking is that the female is checking the health status of the male in order to select a copulation partner with genes for tolerance to cantharidin, the consumption of which allows for resistance to pathogens [2], while avoiding immediate disease transmission during copulations (Fig. 2 D–E) [4],[32],[33]. Similarly, by showing the underwing feather shafts and other parts of their ventral plumage (Fig. 2C), which are preferred sites for adults and eggs of mites and lice to stay or lay eggs, great bustards might show to visiting females that they are free of these ectoparasites.


Males of a strongly polygynous species consume more poisonous food than females.

Bravo C, Bautista LM, García-París M, Blanco G, Alonso JC - PLoS ONE (2014)

A great bustard male in courtship display shows its cloaca to prospective females (A–B; Photographs: C. Palacín).Detail of white feathers of cloaca during display of male great bustard (C; Photographs: F. Kovacs). Detail of other bird with an Otiditaenia conoides in extending from the cloaca (D; Photograph: C. Palacín). Detail of a Otiditaenia conoides individual separate from the body bird (E; Photograph: A. Lucas). Black arrows show the cloaca position.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206510&req=5

pone-0111057-g002: A great bustard male in courtship display shows its cloaca to prospective females (A–B; Photographs: C. Palacín).Detail of white feathers of cloaca during display of male great bustard (C; Photographs: F. Kovacs). Detail of other bird with an Otiditaenia conoides in extending from the cloaca (D; Photograph: C. Palacín). Detail of a Otiditaenia conoides individual separate from the body bird (E; Photograph: A. Lucas). Black arrows show the cloaca position.
Mentions: Another appealing hypothesis is that consumption of blister beetles could also enhance the attractiveness of males to females by reducing their parasite load. This would counter-balance the risk of cantharidin poisoning [25] with reproductive benefits. In addition, males could benefit from cantharidin during the display season, when they may be particularly vulnerable to infections due to their presumably depressed immune system associated to their strenuous investment in sexual display [26],[27]. This hypothesis predicts a male-biased blister beetle consumption (i.e., both sexes would consume blister beetles as a healing or prophylactic agent, but males with potential to attract females should consume them also to enhance their body condition and mating opportunities). Previous studies have shown that age, weight, and display effort are the main predictors of male mating success in this species, and that whiskers and neck plumage are reliable indicators of male age and weight [13],[14]. However, the function of the meticulous inspection females perform of the male's cloaca prior to copulation is still unknown. A male's sexual display consists of a series of extravagant body postures and movements that end, when an interested female approaches, with a reiterative and almost obstinate exhibition of the cloaca, which is fully surrounded by pure white feathers that allow an easy detection of possible parasites or their remains [28],[29] (Fig. 2 A–C). Female bustards are extremely choosy during mating, accepting on average only one of ten males attempting to copulate with them [13]. Females closely inspect the male's cloaca, pecking around it as an essential part of mate selection, after which they decide whether to mate or not with the male [30],[31]. Our interpretation of this cloaca pecking is that the female is checking the health status of the male in order to select a copulation partner with genes for tolerance to cantharidin, the consumption of which allows for resistance to pathogens [2], while avoiding immediate disease transmission during copulations (Fig. 2 D–E) [4],[32],[33]. Similarly, by showing the underwing feather shafts and other parts of their ventral plumage (Fig. 2C), which are preferred sites for adults and eggs of mites and lice to stay or lay eggs, great bustards might show to visiting females that they are free of these ectoparasites.

Bottom Line: The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness.A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females.Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.

View Article: PubMed Central - PubMed

Affiliation: Department of Evolutionary Ecology, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Madrid, Spain.

ABSTRACT
We present evidence of a possible case of self-medication in a lekking bird, the great bustard Otis tarda. Great bustards consumed blister beetles (Meloidae), in spite of the fact that they contain cantharidin, a highly toxic compound that is lethal in moderate doses. In addition to anthelminthic properties, cantharidin was effective against gastrointestinal bacteria that cause sexually-transmitted diseases. Although both sexes consumed blister beetles during the mating season, only males selected them among all available insects, and ingested more and larger beetles than females. The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness. This plausibly explains the intense cloaca display males perform to approaching females, and the meticulous inspection females conduct of the male's cloaca, a behaviour only observed in this and another similar species of the bustard family. A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females. Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.

Show MeSH
Related in: MedlinePlus