How Attractive Is the Girl Next Door? An Assessment of Spatial Mate Acquisition and Paternity in the Solitary Cape Dune Mole-Rat, Bathyergus suillus

Abstract

Behavioural observations of reproduction and mate choice in wild fossorial rodents are extremely limited and consequently indirect methods are typically used to infer mating strategies. We use a combination of morphological, reproductive, spatial, and genetic data to investigate the reproductive strategy of a solitary endemic species, the Cape dune mole-rat Bathyergus suillus. These data provide the first account on the population dynamics of this species. Marked sexual dimorphism was apparent with males being both significantly larger and heavier than females. Of all females sampled 36% had previously reproduced and 12% were pregnant at the time of capture. Post-partum sex ratio was found to be significantly skewed in favour of females. The paternity of fifteen litters (n = 37) was calculated, with sires assigned to progeny using both categorical and full probability methods, and including a distance function. The maximum distance between progeny and a putative sire was determined as 2149 m with males moving between sub-populations. We suggest that above-ground movement should not be ignored in the consideration of mate acquisition behaviour of subterranean mammals. Estimated levels of multiple paternity were shown to be potentially as high as 26%, as determined using sibship and sire assignment methods. Such high levels of multiple paternity have not been found in other solitary mole-rat species. The data therefore suggest polyandry with no evidence as yet for polygyny.

An Example of Burrow System Architecture of Dispersing Damaraland Mole-Rats

“…The present case of the newly immigrated male demonstrates that dispersing animals travel above ground for at least several hundred metres as I did not detect burrowing activities in the vicinity of the released colony. This observation confirms previous reports on aboveground dispersal in other social and solitary mole-rat species (Braude 2000;Patzenhauerova et al 2010;Bray et al 2012). …”

Postnatal development of the largest subterranean mammal (Bathyergus suillus): Morphology, osteogenesis, and modularity of the appendicular skeleton

“…In B. suillus , sexual maturity is hypothesized to happen when individuals are between 494‐529 g, therefore after dispersion and before they reach subadult stages (Figure ). This coincides with the beginning of deceleration of somatic growth in B. suillus, most probably resulting from different factors such as increasing digging demands and reproduction‐related energy allocation. Although our juveniles did not show signs of sexual maturity, some subadults already show them .…”

A proposed framework for establishing and evaluating hypotheses about the behaviour of extinct organisms

“…This seems tenuous as extant solitary bathyergids (e.g. B. suillus ) may often be present in high densities where food is plentiful (Bray et al ., ). Ideas not supported by, or contradicted by, the presented data. Hypotheses have been proposed based on a single line of evidence that are illogical or incorrect.…”

“…This seems tenuous as extant solitary bathyergids (e.g. B. suillus ) may often be present in high densities where food is plentiful (Bray et al ., ).…”