Sexual Size Dimorphism in Vespertilionid Bats

Williams, Daniel F.; Findley, James S.

doi:10.2307/2425072

Cited by 79 publications

(89 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is unclear, however, why the female-biased size differential is negatively correlated with overall body size. The pattern of geographic variation in sexual dimorphism of C. sphinx is in direct contrast to the prediction of the Williams & Findley (1979) hypothesis. If the adaptive value of increased female size is related to thermal homeostasis during pregnancy, the degree of female-biased dimorphism should be inversely correlated with mean minimum daily temperature.…”

Section: Geographic Variation In Sexual Dimorphismcontrasting

confidence: 76%

“…Specifically, selection on females for reduced wing-loading should result in females having proportionally greater wing area relative to males. The hypothesis of Williams & Findley (1979) provides an equally clear prediction about variation in sexual dimorphism in response to climatic variation; selection on females for enhanced thermal inertia should result in a greater degree of female-biased size dimorphism in colder environments. The pattern of sexual dimorphism in C. sphinx appears to support Myers' (1978) wing-loading hypothesis.…”

Section: Geographic Variation In Sexual Dimorphismmentioning

confidence: 99%

“…The opposite pattern was observed, as males were larger than females in the northernmost localities where minimum temperatures are lowest (18.2-19.2°C). The hypothesis of Williams & Findley (1979) was originally formulated in terms of the relationship between body size and the energetics of temperature regulation in vespertilionid bats. Perhaps this hypothesis is not generally applicable to pteropodid bats in tropical environments.…”

Section: Geographic Variation In Sexual Dimorphismmentioning

confidence: 99%

“…According to this hypothesis, larger size of females is an allometric effect of selection for reduced wing-loading. By contrast, Williams & Findley (1979) argued that increased female size in vespertilionid bats reflects an adaptive response to the metabolic demands of maintaining thermal homeostasis during pregnancy. Both of these hypotheses are potentially applicable to a wider range of bat species beyond the Vespertilionidae.…”

Section: Introductionmentioning

confidence: 99%

“…Within the constraints imposed by genetic correlation between the sexes (Lande, 1980), the direction and magnitude of sexual dimorphism expressed in a given population may often reflect the interplay between fecundity selection on females and sexual selection on males (Ralls, 1977;Price, 1984). In bats, both male-biased and female-biased size dimorphism have been documented (Myers, 1978;Williams & Findley, 1979;Findley & Wilson, 1982;Ruedas et al, 1994;Willig & Hollander, 1995), although the underlying causes of sex-limited selection pressures have not been demonstrated for any species. Myers (1978) suggested that female-biased size dimorphism in vespertilionid bats reflects an adaptive response to the aerodynamic challenges of flight during pregnancy (and lactation, if it involves aerial transport of suckling young).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Storz

Balasingh²,

Bhat

et al. 2001

Biological Journal of the Linnean Society

View full text Add to dashboard Cite

Geographic variation in body size and sexual dimorphism of the short‐nosed fruit bat (Cynopterus sphinx) was investigated in peninsular India. Bats were sampled at 12 localities along a 1200 km latitudinal transect that paralleled the eastern flanks of the Western Ghats. The geographic pattern of variation in external morphology of C. sphinx conforms to the predictions of Bergmann's Rule, as indicated by a steep, monotonic cline of increasing body size from south to north. This study represents one of the first conclusively documented examples of Bergmann's Rule in a tropical mammal and confirms that latitudinal clines in body size are not exclusively restricted to temperate zone homeotherms. Body size was indexed by a multivariate axis derived from principal components analysis of linear measurements that summarize body and wing dimensions. Additionally, length of forearm was used as a univariate index of structural size to examine geographic variation in a more inclusive sample of bats across the latitudinal transect. Multivariate and univariate size metrics were strongly and positively correlated with body mass, and exhibited highly concordant patterns of clinal variation. Stepwise multiple regression on climatological variables revealed that increasing size of male and female C. sphinx was associated with decreasing minimum temperature, increasing relative humidity, and increasing seasonality. Although patterns of geographic size variation were highly concordant between the sexes, C. sphinx also exhibited a latitudinal cline in the magnitude and direction of sexual size dimorphism. The size differential reversed direction across the latitudinal gradient, as males averaged larger in the north, and females averaged larger in the south. The degree of female‐biased size dimorphism across the transect was negatively correlated with body size of both sexes. Canonical discriminant analysis revealed that male‐ and female‐biased size dimorphism were based on contrasting sets of external characters. Available data on geographic variation in the degree of polygyny in C. sphinx suggests that sexual selection on male size may play a role in determining the geographic pattern of sexual size dimorphism.

show abstract

Section: Geographic Variation In Sexual Dimorphismcontrasting

confidence: 76%

Section: Geographic Variation In Sexual Dimorphismmentioning

confidence: 99%

Section: Geographic Variation In Sexual Dimorphismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Storz

Balasingh²,

Bhat

et al. 2001

Biological Journal of the Linnean Society

View full text Add to dashboard Cite

show abstract

Sexual dichromatism in the fur of a bat: An exploration of color differences and potential signaling functions

Beilke,

Sanchez,

Hews

et al. 2024

Ecology and Evolution

View full text Add to dashboard Cite

Sex differences in body color (i.e., sexual dichromatism) are rare in bats and, more broadly, in mammals. The eastern red bat (Lasiurus borealis) is a common tree‐roosting bat that occupies much of North America and has long been described as sexually dichromatic. However, previous research on this species found that absolute body size and collection year were better predictors of fur color in preserved specimens than sex. We revisited this issue and photographed 82 live eastern red bats under standardized conditions, then used image analysis to quantify pelage hue, saturation, and value. We used an information theoretic approach to evaluate four competing hypotheses about the principal drivers of color differences in the fur of eastern red bats. Our analyses demonstrated that sex was a better predictor of pelage color than body size; males had redder, more saturated, and lighter pelages than females. Additionally, the fur color of juvenile versus adult bats differed somewhat, as juveniles were darker than adults. In general, absolute body size (i.e., forearm length in bats) was a poor predictor of color in live eastern red bats. In an exploratory post‐hoc analysis, we confirm that fur color is related to body mass (i.e., a proxy for body condition in bats), suggesting color might serve as a sexually selected signal of mate quality in this partially diurnal species. Future work should investigate the functional role of sexual dichromatism in this species, which could be related to signaling or possibly thermoregulation.

show abstract

Seasonal phenology of the little brown bat (Myotis lucifugus) at 60° N

Reimer,

Barclay

2024

Ecosphere

View full text Add to dashboard Cite

To investigate the impact of short summers and long summer solar periods at high latitudes on the behavior of a nocturnal, hibernating mammal, we recorded the phenology of Myotis lucifugus (little brown myotis) at 60° N in the Northwest Territories (NWT), Canada. In particular, we assessed the timing of spring emergence from, and autumn entry into, hibernation, reproduction, and seasonal mass fluctuations. We used a combination of acoustic monitoring and capture surveys at two hibernacula and two maternity roosts during 2011 and 2012. Myotis spp. were active at the hibernacula from late April to late September/early October, suggesting that the “active” season length is similar to that of populations farther south. At maternity colonies, we detected M. lucifugus activity from early May to early October, with peaks during mid‐July in both years. Lactation, fledging, and weaning all occurred later in the NWT than at more southern locations, and reproductive rates were significantly lower than rates observed farther south. The average mass of individuals fluctuated throughout the season, with an initial decline immediately following emergence from hibernation likely reflecting increased energy expenditure due to flight and decreased use of torpor, coupled with relatively low prey intake due to low prey abundance associated with cool temperatures. Females did not appear to have lower pre‐hibernation masses than those in more southern populations, suggesting that despite the cool spring and autumn temperatures, and short summer nights, bats are able to obtain enough energy for reproduction and mass accumulation for hibernation. However, the lower reproductive rates may indicate that there are limitations to life at the northern limits of the species' range.

show abstract

Sexual Size Dimorphism in Vespertilionid Bats

Cited by 79 publications

References 33 publications

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Clinal variation in body size and sexual dimorphism in an Indian fruit bat, Cynopterus sphinx (Chiroptera: Pteropodidae)

Sexual dichromatism in the fur of a bat: An exploration of color differences and potential signaling functions

Seasonal phenology of the little brown bat (Myotis lucifugus) at 60° N

Contact Info

Product

Resources

About