AFRICAN HERP NEWS N A T U R A L H I S T O R Y notes BUFONIDAE dimorphism in which males and females difer in colour, usually results from Sclerophrys poweri sexual selecton for conspicuous colours (Hewit, 1935) in males and natural selecton for cryptc Western Olive Toad colours in females and its prevalence and diversity in frogs and toads is increasingly recognized (Doucet and Mennill 2010; COLOURATION Bell and Zamudio 2012; Bell et al. 2017). Dynamic dichromatsm refers to P. BERG & F. S. BECKER a temporary colour change between the sexes in the context of breeding, as opposed to a permanent or ontogenetc Natural and sexual selecton drive the colour change, and is probably under- diversity of communicaton strategies documented due to its ephemeral nature in the animal world. Colour displays can (Bell et al. 2017). functon as visual signals transmitng In the late evening of 26 April 2014, in informaton to inter- and intraspecifc the rain, a female Sclerophrys poweri was receivers, thereby impactng the observed sitng in a hotel garden puddle ftness of an animal substantally. For (Fig. 1A) in Oshakat, Oshana region, example, in the context of predaton, Namibia (17° 47’ 08.1” S 15° 41’ 56.4” E, it may be protectve to blend in with 1102 m a.s.l.). The toad displayed a very the environment (camoufage) or warn distnctve red dorsal body colouraton, potental predators (aposematsm) which covered the head, back, and, to (Rojas 2017). Moreover, visual signals a lesser extent, limbs and lateral body can facilitate mate recogniton and parts (Fig. 1 B, C). The normal colouraton choice, and complement acoustc of S. poweri is yellow-brown to olive- communicaton in anurans. Whereas green with pairs of dark-edged brown or conspicuous colour displays may increase reddish-brown patches and red infusions an individual’s reproductve success, they on the hindlegs (Du Preez and Carruthers may at the same tme increase predaton 2017). A light throat and the absence of risk, hence resultng in a trade-of nuptal pads on the feet suggest that the between diferent selectve pressures. encountered individual was female. Sexual dichromatsm, a form of sexual A similarly coloured female S. poweri NUMBER 73 | APRIL 2020 25 AFRICAN HERP NEWS >>>>>>>NATURAL HISTORY notes>>>>>>> Figure 1. Conspicuous red pigmentaton in the Western Olive Toad, Sclerophrys poweri, in Namibia. The frst toad was encountered in a rain puddle in the late evening in Oshakat, Namibia (A). Dorsolateral (B) and frontolateral view (C) of the same individual. A second individual of S. poweri with a reddish dorsal body colouraton was encountered in the rain at night in Windhoek, Namibia (D). (Photos: A–C: P. Berg; D: F. S. Becker) was observed 550 km away in Windhoek, amphibians (Gomez et al. 2009; Gomez Khomas region, Namibia, on the frst et al. 2010; Robertson and Greene rainy night in the season on 23 October 2017). While colouraton linked to sexual 2018 (Fig. 1D), about 10 m from a pool selecton is usually associated with where these toads have been known to males, the recogniton of conspecifcs breed. afects both sexes, and can have several Both observatons were made in advantages in the breeding context. the rain, under low light conditons. For example, males of the nocturnal Amphibians possess two types of rod treefrog Hyla versicolor are more likely photoreceptors, which may allow for to give courtship calls if they detect an rod-based colour discriminaton at very approaching female (Reichert 2013), low light levels (Yovanovich et al. 2017). which may represent a strategy to Bright colouraton has been suggested balance the risk of being conspicuous to play a role in both sexual selecton to predators and the chances to atract and mate recogniton in nocturnal atenton of potental mates. NUMBER 73 | APRIL 2020 26 AFRICAN HERP NEWS >>>>>>>NATURAL HISTORY notes>>>>>>> In the literature, informaton for the toad Pelobates fuscus (Kolenda et on the reproducton biology of S. al. 2017). Environmental factors, namely poweri is scarce with the excepton high iron concentratons in water and of Channing (2001), who states that soil, rather than mutatons afectng the frst rain in the season initates pigment producton or chromatophores breeding. Hence, there may be a link distributon, were hypothesized as a between the observed conspicuously trigger in the later case (Kolenda et al. red pigmentaton and rain-triggered 2017); alternatve explanatons, including breeding actvity. In related species dynamic sexual dichromatsm, were not breeding has been recorded at various discussed. tmes of the year (Conradie and Bills Dynamic dichromatsm has been 2017). Anecdotal observatons indicate described for males of other toads of the that S. poweri may breed throughout genus Sclerophrys, but not for females spring and summer in perennial, usually of any species. Males of S. lemairii artfcial, water bodies, but that breeding (Lemaire’s Toad) turn bright yellow during actvity is more pronounced afer the breeding periods (Bitencourt-Silva 2014; frst rain of the season. Although the Conradie and Bills 2017) as do males of S. toads were not collected and observed kisoloensis (Kisolo Toad), which revert to later, it is assumed that this colouraton their normal colouraton afer a few hours is temporal, because it is atypical for the (Channing and Howell 2006). According species, even compared to sightngs of to an overview presented by Bell et al. conspecifcs in Windhoek and northern (2017), dynamic dichromatsm occurs Namibia. Moreover, if this conspicuous fairly commonly in the family Bufonidae colouraton was of permanent nature, and a transient yellow or yellow-brown the predaton risk would be augmented colouraton has also been described for S. and it seems unlikely that the individuals guturalis, S. maculatus and S. togoensis. reached adult age. While colour or patern Other colours have been reported for polymorphism has been described for male toads of the genus Altphrynoides, many anuran species, aberrant colour which change to lime green or orange morphs characterized by an unusual (Channing and Rödel 2019). However, a reddish pigmentaton (erythrism) have temporary shif to yellow coloraton is by been reported less commonly. For far the most common display colour in example, erythristc specimens with red dynamically dichromatc frogs (Bell et al. pigmentaton confned to dorsal body 2017). If the colouraton of the observed parts and less pronounced on the limbs, individuals of S. poweri represents sexual similar to the case described here, have dichromatsm, this case would be an been documented for (female) Bufo excepton to the norm in terms of colour viridis (Lanza and Canestrelli 2002) and and sex. While reports of “reverse” NUMBER 73 | APRIL 2020 27 AFRICAN HERP NEWS >>>>>>>NATURAL HISTORY notes>>>>>>> ontogenetc sexual dichromatsm (i.e., ACKNOWLEDGEMENTS more ornate coloraton in females than Many thanks to Alan Channing (University in males) exist, it is assumed to have of the Western Cape) for valuable evolved in species with sex role reversal comments and to the reviewers whose (e.g., Engelbrecht-Wiggans et al. 2019; advice improved the manuscript. PB Portk et al. 2019; but see Heinsohn et owes special thanks to Jessica and Rainer al. 2005 for an excepton in a bird). For Berg for travelling and sharing so many dynamic sexual dichromatsm, all known observatons together. cases refer to a temporary colour change in breeding males but one case of mutual dynamic colour change in both males and REFERENCES females of the bufonid Xanthophryne Bell RC, Webster GN, Whitng MJ. 2017. tgerinus (Bell et al. 2017). 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