Influence of urbanization on morphometrics and extent of sexual size dimorphism of the African common toad Sclerophrys regularis in the Accra Plains of Ghana

Abstract

A thorough understanding of the effects of urbanization on wildlife is essential for designing effective strategies to conserve and manage wild animal populations in cities. Although the Afro-tropical region is experiencing rapid urbanization, the effect of this on wildlife in the region remains understudied. Here, we compared morphometric traits and extent of sexual size dimorphism of the African common toad Sclerophrys regularis among rural, suburban and urban areas in the Accra Plains of Ghana. We analyzed the morphometric data using univariate and multivariate statistics. Our data revealed that body mass and body condition, but not body size of toads varied significantly along the urbanization gradient. Urban and rural males were significantly heavier and had significantly higher body condition index value (in better condition) than their suburban counterparts, while urban females were significantly heavier and in better body condition than their suburban counterparts. The urban males and suburban females had significantly wider mouths than their rural conspecifics. We also found significant differences in head volume and length of limbs among sites, but the response direction varied with sex. Allometric analysis showed negative allometry in all the measured morphometrics with respect to SVL at all the sites for both sexes, except for suburban females, which showed positive allometry in most of the measured morphometrics. The toads exhibited female-biased sexual dimorphism (SSD) in SVL, body mass and head volume, with the extent of SSD being strongest for the suburban population. The variable responses of male and female S. regularis to urbanization could be due to phenotypic plasticity in its life history. Our findings highlight the potential role of individual-level response metrics in enhancing wildlife monitoring and conservation in cities.