Ambient Temperature in Spring Affects Horn Growth in Male Alpine Ibexes

Giacometti, Marco; Willing, R.; Defila, Claudio

doi:10.1644/1545-1542(2002)083<0245:atisah>2.0.co;2

Cited by 38 publications

(44 citation statements)

References 14 publications

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“…Although the effect of nutrition and photoperiodicity spe-cifically on rhamphothecal growth is generally not known, support for these mechanisms can be found for other keratin-based structures. The effect of ambient temperature on nutritional status has been demonstrated in affecting the growth rate of horns in sheep (Hoefs and Nowlan 1997;Giacometti et al 2002) and photoperiod has been implicated in breeding season increases in horn growth as well (Santiago-Moreno et al 2012). Seasonal variation in growth rate has been documented in bovine hoofs, another keratinized structure (Hahn et al 1986).…”

Section: Discussionmentioning

confidence: 99%

Seasonal dimorphism in the horny bills of sparrows

Greenberg

Etterson

Danner

2013

Ecology and Evolution

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Bill size is often viewed as a species-specific adaptation for feeding, but it sometimes varies between sexes, suggesting that sexual selection or intersexual competition may also be important. Hypotheses to explain sexual dimorphism in avian bill size include divergence in feeding niche or thermoregulatory demands, intrasexual selection based on increased competition among males, or female preference. Birds also show seasonal changes in bill size due to shifts in the balance between growth rate and wear, which may be due to diet or endogenous rhythms in growth. Insight into the function of dimorphism can be gained using the novel approach of digital x-ray imaging of museum skins to examine the degree to which the skeletal core or the rhamphotheca contribute to overall dimorphism. The rhamphotheca is ever-growing and ever-wearing, varying in size throughout life; whereas the skeletal core shows determinant growth. Because tidal marsh sparrows are more dimorphic in bill size than related taxa, we selected two marsh taxa to investigate dimorphism and seasonality in the size of the overall bill, the skeletal core, and the rhamphotheca. Bill size varied by sex and season, with males having larger bills than females, and bill size increasing from nonbreeding to breeding season more in males. Skeletal bill size varied with season, but not sex. The rhamphotheca varied primarily with sex; males had a larger rhamphotheca (corrected for skeletal bill size), which showed a greater seasonal increase than females. The rhamphotheca, rather than the skeletal bill, was responsible for sexual dimorphism in overall bill size, which was particularly well developed in the breeding season. The size of the rhamphotheca may be a condition-based character that is shaped by sexual selection. These results are consistent with the evidence that bill size is influenced by sexual selection as well as trophic ecology.

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Section: Discussionmentioning

confidence: 99%

Seasonal dimorphism in the horny bills of sparrows

Greenberg

Etterson

Danner

2013

Ecology and Evolution

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“…Horn growth varies among Swiss populations because of different nutrition (Nievergelt 1966). Horn growth and dimensions are influenced by ambient condition such as weather, food availability, and population density (Giacometti et al 2002b;Michallet et al 1994Michallet et al , 1996Nievergelt 1978). Horn growth in C. ibex from the lower Engadin Valley in the eastern Canton Graubü nden, Switzerland, was significantly greater than in the upper Engadin Valley; horn growth was correlated with favorable ambient temperatures and plant phenology in spring in both regions (Giacometti et al 2002b).…”

Section: General Charactersmentioning

confidence: 99%

Capra ibex (Artiodactyla: Bovidae)

Parrini

Cain

Krausman³

2009

Mammalian Species

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“…Furthermore, horn development may be affected by space-or time-dependent variations in environmental parameters such as precipitations (Chirichella et al, 2013), temperature (Giacometti et al, 2002) or food availability (Festa-Bianchet et al, 2004).…”

Section: Introductionmentioning

confidence: 99%