Daniel William Hart

Daniel William Hart
University of Pretoria | UP · Department of Zoology and Entomology

Doctor of Philosophy

About

33
Publications
3,180
Reads
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252
Citations
Additional affiliations
May 2019 - July 2019
Sokoine University of Agriculture (SUA)
Position
  • Research Associate
April 2019 - May 2019
University of Pretoria
Position
  • Lecturer
Description
  • Evolutionary physiology with focuses on osmoregulation and reproduction

Publications

Publications (33)
Article
Full-text available
The social mole-rats of the family Bathyergidae show elaborate social organisation that may include division of labour between breeders and non-breeders as well as across non-breeders within their groups. However, comparative behavioural data across the taxa are rare and contrasts and similarities between species are poorly understood. Field studie...
Article
Full-text available
The doubly labeled water (DLW) technique and indirect calorimetry enable measurement of an animal's daily energy expenditure (DEE, kJ/day), resting metabolic rate (RMR, kJ/d), sustained metabolic scope (SusMS), body fat content (BF, %) as well as water turnover (WTO, ml/day), and water economy index (ml/kJ). Small mammals have been the primary focu...
Article
Cooperative behaviour, sociality and reproductive suppression in African mole-rats have been extensively studied. Nevertheless, endocrine correlates of some species of social mole-rats have been neglected, and these species may hold the key to understanding the behavioural and physiological complexity that allows the maintenance of social groups in...
Article
Full-text available
Sub-lethal effects, such as oxidative stress, can be linked to various breeding and thermophysiological strategies, which themselves can be linked to seasonal variability in abiotic factors. In this study, we investigated the subterranean, social living Natal mole-rat (Cryptomys hottentotus natalensis), which, unlike other social mole-rat species,...
Article
Full-text available
Naked mole-rats (NM-R; Heterocephalus glaber) live in multi-generational colonies with a social hierarchy, and show low cancer incidence and long lifespans. Here we asked if an immune component might underlie such extreme physiology. The largest lymphoid organ is the spleen, which plays an essential role in responding to immunological insults and m...
Article
Full-text available
Anthropogenic land transformation is a consequence of human population growth and the associated agricultural, residential, and industrial needs. This study aimed to investigate the effects of anthropogenic activity and human-mediated land transformation on capture/recapture frequencies, species richness, and diversity of native small mammal commun...
Article
Full-text available
Differences in individual locomotor activity patterns may be linked to a number of ecological factors, such as changes in ambient temperature or photoperiod. Observations on subterranean mammals suggest that they exhibit diel rhythms despite the lack of visual cues in their underground burrows, but it is unknown how seasonality and individual chara...
Article
Full-text available
Naked mole-rats are among the most hypoxia-tolerant mammals. During hypoxia, their body temperature (T b) decreases via unknown mechanisms to conserve energy. In small mammals , non-shivering thermogenesis in brown adipose tissue (BAT) is critical to T b regulation; therefore, we hypothesize that hypoxia decreases naked mole-rat BAT thermogenesis....
Article
Full-text available
Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investig...
Article
Full-text available
It has been proposed that naked mole-rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non-breeding individuals. Earlier studies suggested that non-breeders belong to distinct castes that specialise permanently or temporarily in specific cooperative tasks. In contrast, recent research on...
Article
In arid regions, unpredictable rainfall patterns and extreme temperature variation occurs; this poses severe constraints on reproduction in small mammals. In the present study, the gonad morphometrics, gonadal histology and endocrine profiles of the female Lesser Egyptian jerboas (Jaculus jaculus) were studied over one year in a wild population fro...
Article
Full-text available
One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and...
Article
African mole-rats have provided great insight into mammalian evolution of sociality and reproductive strategy. However, some species have not received attention, and these may provide further insights into these evolutionary questions. The cooperatively breeding Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is one such species. Bod...
Preprint
Full-text available
Naked mole-rats (NM-R; Heterocephalus glaber) live in multi-generational colonies with a social hierarchy, show low cancer incidence and long life-spans. Here we asked if such extreme physiology might have an immune component. The spleen is the largest lymphoid organ and plays an essential role in response to immunological insults and may participa...
Article
Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature (Ta), has received much less attention. To address th...
Article
The effect of the macro- and microclimate on small mammal thermoregulation in the past has been studied independently instead of investigating the dual effect of both the components. This study addresses this dearth in knowledge by exploring the dual effect of both micro- and macro-climate on the thermoregulatory responses of two subterranean roden...
Preprint
Full-text available
It has been proposed that naked mole-rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non-breeding individuals. Earlier studies suggested that non-breeders belong to distinct castes that specialise permanently or temporarily on specific cooperative tasks. In contrast, recent research on...
Article
Naked mole-rats ( Heterocephalus glaber ) form some of the most cooperative groups in the animal kingdom, living in multigenerational colonies under the control of a single breeding queen. Yet how they maintain this highly organized social structure is unknown. Here we show that the most common naked mole-rat vocalization, the soft chirp, is used t...
Article
Full-text available
Background The endemic rodent family of Bathyergidae in Africa, particularly South Africa, are understudied as reservoirs of diseases of significant medical importance. Considering the diversity and wide distribution of African mole-rats in South Africa, many of these bathyergids could act as carriers of zoonoses. Methods The present study assesse...
Article
Full-text available
Understanding the reproductive biology of the roan antelope (Hippotragus equinus) (É. Geoffroy Saint-Hilaire, 1803) is crucial to optimise breeding success in captive breeding programmes of this threatened species. In this study, the pattern of faecal androgen metabolite (fAM) production related to reproductive events (calving or birthing, mating,...
Article
Full-text available
We report instances of mole snakes (Pseudaspis cana) inhabiting mole-rat burrows in various locations of southern Africa. We also report instances that we believe to be predation of mole-rats by mole snakes.
Article
The animal-environment interaction is complex, and the ability to temporally organise locomotor activity provides adaptive and survival advantages. The daily and circadian rhythms of locomotor activity in the Desert hedgehog, Paraechinus aethiopicus, from the central deserts of Saudi Arabia were investigated under controlled laboratory conditions....
Article
This study aimed to assess the seasonal reproductive strategy occurring in the male Lesser Egyptian jerboa (Jaculus jaculus) and determine which environmental cues are responsible for initiating reproductive recrudescence. Body mass, morphometry of the reproductive tract, the histology of the testes and the circulating testosterone concentrations i...
Article
The Mahali mole-rat (Cryptomys hottentotus mahali (Roberts, 1913)) is a social, cooperatively breeding subterranean rodent that breeds aseasonally. Only one female in a colony breeds and the remaining females are reproductively suppressed. When the opportunity arises, these non-reproductive females disperse from the natal colony to escape reproduct...
Article
Mole-rats are champions of self-preservation, with increased longevity compared to other rodents their size, strong antioxidant capabilities, and specialized defenses against endogenous oxidative stress. However, how the brains of these subterranean mammals handle acute in vivo hypoxia is poorly understood. This study is the first to examine the mo...
Article
Aims: Burrowing mammals tend to be more hypoxia tolerant than non-burrowing mammals and rely less on increases in ventilation and more on decreases in metabolic rate to tolerate hypoxia. Naked mole-rats (Heterocephalus glaber, NMRs), eusocial mammals that live in large colonies, are among the most hypoxia-tolerant mammals, and rely almost solely o...
Article
Noxious substances, called algogens, cause pain and are used as defensive weapons by plants and stinging insects. We identified four previously unknown instances of algogen-insensitivity by screening eight African rodent species related to the naked mole-rat with the painful substances capsaicin, acid (hydrogen chloride, pH 3.5), and allyl isothioc...
Article
Full-text available
Colonies of naked mole-rats (Heterocephalus glaber, NMRs) are characterised by an extreme skew in lifetime reproductive success with only one female and one to three male consorts in a colony. The rest of the individuals in a colony are reproductively suppressed and much research has been focussed on elucidating that mechanism. The dopamine system...
Article
African mole-rats (family: Bathyergidae) are strictly subterranean mammals that reside in extensive networks of underground tunnels. They are rarely, if ever, exposed to light and experience muted temperature ranges. Despite these constant conditions, the presence of a functional circadian clock capable of entraining to external light cues has been...
Article
Full-text available
The reproductive pattern of the Libyan jird (Meriones libycus Lichtenstein, 1823) from central Saudi Arabia was investigated in the absence of rainfall. In this study, body mass, morphometry of the reproductive tract, the histology of the reproductive organs, and the hormone concentrations of males and females were studied over 12 consecutive month...
Article
We set out to test whether the Ethiopian hedgehog, Paraechinus aethiopicus is a seasonal or aseasonal breeder and assess which environmental cues bring about both reproductive recrudescence and its subsequent regression. In this study, the body mass, morphometry of the reproductive tract the histology of the reproductive organs and the hormone conc...

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Projects

Projects (2)
Project
Assessing the correlation between abiotic variables and land use and group size and body mass of mole-rats to further investigate the Aridity Food Distribution Hypothesis. Comparing relatedness and population differentiation between the highveld mole-rat and the Mahali mole-rat.
Project
Establish the relevant importance of various zeitgebers in synchronising circadian rhythms of African mole-rats