The pattern of reproduction in the African giant pouched rat, Cricetomys gambianus, from Tanzania : unravelling the environmental triggers for breeding

DATA AVAILABILITY : The datasets presented in this article are not readily available because rights to this raw data are held by the institute and further permission is needed to release such data. Requests to access the datasets should be directed to DWH, [email protected] research represents the first extensive study of the breeding behaviour and related environmental triggers of reproduction in the African giant pouch rat (Cricetomys gambianus Waterhouse, 1840) in and around the equator throughout a whole year. We measured the gross morphology and detailed histology of both female and male rats, along with plasma steroid hormone levels. Contrary to other tropical-dwelling small mammals, the African giant pouch rat is a seasonal breeder; however, rainfall is not to be the primary cue of reproduction. Our study suggests that ambient temperature and photoperiod are the primary environmental cues of reproduction, with breeding occurring during the cooler months of the year, namely in the dry season. During the wet and hot season, which succeeds the dry season, there is an increase in the availability of quality food, which results in nursing mothers and weaned pups achieving a positive energy balance and increased body condition. This, in turn, increases pregnancy success and offspring survival. Climate change, particularly global warming, could harm the reproduction of African giant pouched rats as rising temperatures in and around the equator, including Tanzania, may impact their circannual reproductive cycle.The World Bank through African Centre of Excellence for Innovative Rodent Pest Management and Biosensor Technology Development at the Sokoine University of Agriculture (SUA), in Tanzania.https://cdnsciencepub.com/journal/cjzhj2024Mammal Research InstituteZoology and EntomologySDG-03:Good heatlh and well-beingSDG-15:Life on lan

Small mammal diversity in response to land transformation and seasonal variation in South Africa

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 community assemblages in the Magaliesberg Biosphere, North West province, South Africa. Five anthropogenically transformed land-use types were investigated: an animal rehabilitation and ecotourism center, an agricultural farmstead, a residential farmstead, a mine-adjacent agricultural farmstead, and a protected nature conservancy. We used live traps to sample small mammals during the dry and wet seasons over three consecutive years and compared population numbers and species composition across study sites and seasons. Capture/recapture frequencies differed significantly between sites and seasons, with the highest capture frequencies recorded at the agricultural and residential farmsteads. Species richness and diversity were highest at the residential and mine-adjacent farmsteads, both of which experienced intermediate levels of anthropogenic disturbance throughout the sampling period. The study shows that while natural and protected landscapes with low levels of disturbance are preferred, transformed landscapes can also be managed effectively to benefit native small mammal populations by regulating the frequency and intensity of human-mediated activities.Supplementary Materials: Details of molecular methodology, Table S1: Summary information of reference sequences used in the construction of the maximum likelihood tree; Figure S1: Maximum likelihood tree.DSI-NRF Centre of Excellence for Invasion Biologyhttps://www.mdpi.com/journal/diversitydm2022Mammal Research InstituteZoology and Entomolog

Plasma oxidative stress in reproduction of two eusocial African mole‑rat species, the naked mole‑rat and the Damaraland mole‑rat

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 minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.SUPPLEMENTARY MATERIAL : Tables S1 and S2. Sample details and respective TOS (total oxidant status), TAC (total antioxidant capacity) and OSI (oxidative stress index) for Naked mole-rats and for Damaraland mole-rats. NBF: non-breeding females, NBM: non-breeding males, BM: breeding males, BF: breeding females.The SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST-NRF South Africa, the National Research Foundation and the University of Pretoria.http://www.frontiersinzoology.comam2022Mammal Research InstituteZoology and Entomolog

Is the Mahali mole-rat (Cryptomys hottentotus mahali) a spontaneous or induced ovulator?

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 reproductive suppression and pair up with an unrelated male to start a new colony. This study set out to determine whether female Mahali mole-rats are induced or spontaneous ovulators once separated from the reproductive suppression of the breeding female. Fifteen separated females were subjected to three treatments: housed separately without a male (A), allowed chemical, but not physical, contact with a vasectomised male (NPC), and placed in direct contact with a vasectomised male (PC). Urine was collected from all females under each treatment every 2 days for 40 days. Only females housed in the PC treatment exhibited heightened progesterone concentrations and corpora lutea of ovulation in the ovaries. Furthermore, males possessed epidermal spines on the shaft of the penises that may be used to stimulate the cervix of the female during copulation. These findings suggest that the Mahali mole-rat is an induced ovulator.The SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST–NRF South Africa, the National Research Foundation and the University of Pretoria.http://www.nrcresearchpress.com/journal/cjzhj2020Mammal Research InstituteZoology and Entomolog

Validation of enzyme immunoassays via an adrenocorticotrophic stimulation test for the non-invasive quantification of stress-related hormone metabolites in naked mole-rats

DATA AVAILABILITY: Data supporting the reported results will be sent by the corresponding author upon request.SUPPLEMENTARY MATERIALS : TABLE S1: Summary of saline volume and synthetic adrenocorticotropic hormone (Synacthen® depot, Novartis, South Africa (Pty) Ltd.) administered to each individual during the ACTH challenge; TABLE S2: Summary of EIA sensitivities and intra-assay and inter-assay coefficients of variation in high- and low-value quality controls for all EIAs applied to measure immunoreactive urine glucocorticoid metabolite (uGCM) and fecal glucocorticoid metabolite in naked mole-rats.Small size in mammals usually restricts long-term, frequent monitoring of endocrine function using plasma as a matrix. Thus, the non-invasive monitoring of hormone metabolite concentrations in excreta may provide an invaluable approach. The aim of the current study was to examine the suitability of enzyme immunoassays (EIAs) for monitoring responses to stressors in the naked mole-rat (Heterocephalus glaber, NMR) using urine and feces as hormone matrices. A saline control administration, and a high- and low-dose adrenocorticotropic hormone (ACTH) challenge were performed on six male and six female disperser morph NMRs. The results revealed that a 5α-pregnane-3β,11β,21-triol-20-one EIA detecting glucocorticoid metabolites (GCMs) with a 5α-3β-11β-diol structure is the most suitable assay for measuring concentrations in male urine samples, whereas an 11-oxoaetiocholanolone EIA detecting GCMs with a 5β-3α-ol-11-one structure appears the most suitable EIA for quantifying GCMs in female urine. An 11-oxoaetiocholanolone EIA detecting 11,17 dioxoandrostanes was the most suitable EIA for quantifying GCMs in the feces of both sexes. There were sex-related differences in response to the high- and low-dose ACTH challenge. We recommend using feces as a more suitable matrix for non-invasive GCM monitoring for NMRs which can be valuable when investigating housing conditions and other welfare aspects.SARChI Chair of Mammalian Behavioral Ecology and Physiology from the DST–NRF South Africa and the National Research Foundation.https://www.mdpi.com/journal/animalsMammal Research InstituteZoology and Entomolog

Ectoparasitic community of the Mahali mole-rat, Cryptomys hottentotus mahali : potential host for vectors of medical importance in South Africa

BACKGROUND: The endemic rodent family of Bathyergidae in Africa, particularly South Africa, are understudied as reservoirs of diseases of signifcant 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 assessed the ectoparasite community of the Mahali mole-rat (Cryptomys hottentotus mahali). We aimed to identify possible parasitic arthropods that may infest this mole-rat species and explore host preference, contributions of seasonality, host sex and body mass as well as social class and colony size on ectoparasite assemblage prevalence and abundance. RESULTS: A limited number of ectoparasite species were found on C. h. mahali belonging to two signifcant taxa: mites (Acari) and feas, with mites being the most prevalent and abundant. We recorded the presence of X. philoxera, a fea well known as the principal reservoir of plague in the southern African region on the Mahali mole-rats. Only three mite species were collected: Androlaelaps scapularis, Androlaelaps capensis and Laelaps liberiensis. Seasonal peaks in prevalence and abundance of X. philoxera and A. scapularis were observed during summer. Xenopsylla philoxera abundance and A. scapularis loads signifcantly increased on reproductive mole-rat individuals in comparison to nonreproductive individuals. CONCLUSION: Despite the wide distribution of the subterranean African mole-rats, studies investigating their parasitic fauna remain limited and scarce. This dearth in knowledge raises the concern regarding their potential role as an endemic reservoir for zoonotic diseases. Consequently, additional sampling of their ectoparasitic community throughout their distributional range and research addressing their role as a reservoir for zoonotic diseases in southern Africa are urgently needed.SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST-NRF South Africa; National Research Foundation and University of Pretoria, South Africa.https://parasitesandvectors.biomedcentral.compm2022Zoology and Entomolog

Aggression, boldness, and exploration personality traits in the subterranean naked mole-rat (Heterocephalus glaber) disperser morphs

Animal personality traits (consistent behavioral differences between individuals in their behavior across time and/or situation) affect individual fitness through facets, such as dispersal. In eusocial naked mole-rat (Heterocephalus glaber) colonies, a disperser morph may arise with distinct morphological, behavioral, and physiological characteristics. This study aimed to quantify the personality traits of a cohort of disperser morphs of naked mole-rat (NMR). Behavioral tests were performed on twelve disperser morphs (six males and six females) in an observation tunnel system that was novel and unfamiliar. Novel stimuli (fresh snakeskin, tissue paper, and conspecific of the same sex) were introduced for fifteen minutes, and the behavioral acts of the individual were recorded. A total of 30 behaviors were noted during the behavioral tests of which eight were used to quantify aggression, boldness, and exploration. The NMR disperser morphs showed consistent individual differences in boldness, and exploration across time and test, indicating a distinct personality. In addition, new naked mole-rat responses including disturbance behaviors; confront, barricade, and stay-away, were recorded. Further investigations into the relationships between animal personality traits and social hierarchy position in entire colonies are needed for more informative results as we further investigate the role of personality in cooperatively breeding societies.The SARChI Chair of Mammalian Behavioral Ecology and Physiology from the DST–NRF South Africa, the National Research Foundation, and the University of Pretoria. J.U.M Jarvis, G. Lewin and A. Barker for equipment donation.https://www.mdpi.com/journal/animalsam2023Zoology and Entomolog

The pattern of reproduction in the Libyan jird (Meriones libycus; Rodentia: Muridae) from central Saudi Arabia in the absence of rainfall

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 months in a wild population of the Libyan jird from central Saudi Arabia. Previous studies have found the breeding season of the Libyan jird from the Sahara desert of Algeria to occur during the wet months of spring. In the absence of rainfall, temperature and photoperiod were found to be important activators of reproductive activity. The cooler temperatures and shorter days of winter triggered the onset of ovulation in females and increased testes size and seminiferous tubule diameter in males. Only two pregnancies were found during the sampling period, which occurred during the cooler winter and early spring and coincided with a rise in plasma progesterone concentration in females. The Libyan jird was found to shift its breeding to the cooler months of winter in the absence of rainfall. This study strengthens the findings that changes in rainfall and temperature in dry deserts are critical cues for the onset of reproduction in small mammals.The Deanship of Scientific Research at the King Saud University through Vice Deanship of Research Chairs and King Abdulaziz City for Science and Technology (KACST) through Graduate Research Program. N.C.B. acknowledges funding from the SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST–NRF South Africa, the National Research Foundation (grant No. 64756), and the University of Pretoria.http://www.nrcresearchpress.com/journal/cjzhj2019Zoology and Entomolog

Cultural transmission of vocal dialect in the naked mole-rat

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 to transmit information about group membership, creating distinctive colony dialects. Audio playback experiments demonstrate that individuals make preferential vocal responses to home colony dialects. Pups fostered in foreign colonies in early postnatal life learn the vocal dialect of their adoptive colonies, which suggests vertical transmission and flexibility of vocal signatures. Dialect integrity is partly controlled by the queen: Dialect cohesiveness decreases with queen loss and remerges only with the ascendance of a new queen.The European Research Council and a South African Research Chair for Mammalian Behavioral Research.http://www.sciencemag.orghj2022Mammal Research InstituteZoology and Entomolog

The cost of reproduction in a cooperatively breeding mammal : consequences of seasonal variation in rainfall, reproduction, and reproductive suppression

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 investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.The SARChI chair of Mammalian Behavioural Ecology and Physiology from the DST-NRF South Africa, the National Research Foundation and the University of Pretoria.http://www.frontiersin.org/Physiologyam2022Mammal Research InstituteZoology and Entomolog