Foraging in the subterranean social highveld mole‐rat (Cryptomys hottentotus pretoriae): an investigation into mass‐dependent geophyte use and foraging patterns

Abstract

The foraging behaviour of captive colonies of the highveld mole-rat Cryptomys hottentotus pretoriae was investigated in an artificial soil-filled burrow system provided with four trays (patches) that varied in geophyte density and mass. An initial trial involving empty trays (only soil) revealed that there was no preference for any specific tray. There were no statistically significant preferences for excavating in any of the patches of different geophyte density. No preferences were evident for excavation in patches containing geophytes of different mass classes. Empty patches seemed to be preferred over patches containing geophytes when combinations of geophyte density/mass were investigated. The duration of handling and the rate of consumption of geophytes were recorded for 23 individuals of two mass classes. Handling time of geophytes was not related to mole-rat sex, but was strongly linked to mole-rat mass class. Handling time of geophytes was related to geophyte mass class. Small geophytes were less profitable to consume. These findings are considered in light of optimal foraging theory and the situation in the field. It was concluded that the mole-rats generally followed the qualitative predictions of optimal foraging theory, although falling short of being energy maximizers.

Resource characteristics and foraging adaptations in the silvery mole‐rat (Heliophobius argenteocinereus), a solitary Afrotropical bathyergid

“…Whereas the largest tubers were usually left in situ and the smallest were either consumed in situ or transported to the nest. Similar behavior has been observed in other subterranean rodents (Jarvis et al 1998;Barnett et al 2003;Begall and Gallardo 2000;Malherbe et al 2003). 3.…”

“…Interestingly, in captive C. hottentotus and F. damarensis, behavior, which is the opposite to the area-restricted search have been observed (Malherbe et al 2003;Barnett et al 2003). The mole-rats, after finding a food resource, abandoned the area and started to burrow elsewhere, presumably in search of another food resource.…”

Energetics and Water Flux in the Subterranean Rodent Family Bathyergidae

“…African mole-rats do not share this pattern as the more arid dwelling species possessed higher WEI than the more mesic dwelling species. A more surprising fact is that African mole-rats do not drink freestanding water but obtain all water requirements from underground geophytes, which become more dispersed in arid regions (Bennett et al, 1994;Bennett and Jarvis, 1995;Spinks et al, 1999;Malherbe et al, 2003). African mole-rats need to forage for geophytes through the energetically expensive method of digging (Vleck, 1979), which becomes energetically more expensive the drier the soils become (Lovegrove, 1989).…”

“…In addition, excavation of tunnel systems is energetically more expensive than aboveground exploration (Vleck, 1979), with energy requirements of digging directly related to soil moisture and hardness (Lovegrove, 1989;Thomas et al, 2009Thomas et al, , 2016. The added energy expenditure necessary for digging, in conjunction with the fact that African mole-rats obtain all their nutrient and water requirements from the storage organs of underground geophytes (Bennett et al, 1994;Bennett and Jarvis, 1995;Spinks et al, 1999;Malherbe et al, 2003), has been suggested to exacerbate the selection pressures placed upon African mole-rats to enable them to locate adequate resources for survival and reproduction (Bennett and Faulkes, 2000). The energetic cost of digging under the unique microclimate within the tunnels they inhabit has been hypothesized to lead to lower RMRs and body temperatures displayed by African mole-rats in comparison to aboveground rodent species (McNab, 1966;Shkolnik and Schmidt-Nielsen, 1976;Bennett et al, 1992McGowan et al, 2020) and a social and eusocial lifestyle in species inhabiting very arid environments [the ' Arid-Food-Distribution-Hypothesis ; Lacey and Sherman (1997)].…”

The comparative anatomy of the abdominal gastrointestinal tract of six species of African mole‐rats (Rodentia, Bathyergidae)

“…Omnivory like consuming dead pups in captivity (H. glaber), insects, or gnawing on bone fragments seem to be the exception rather than the rule in the African mole-rats species studied here (Brett, 1991;Bennett and Faulkes, 2000). The size of tubers and bulbs plays a role in the availability of energy to the animal as larger storage organs provided more energy with less handling time in a study on captive Cryptomys hottentotus pretoriae (Malherbe et al, 2003). There are differences in terms of which part of the storage organ is ingested.…”