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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. Body mass, reproductive-tract morphometrics, gonad histology, and plasma reproductive hormone concentrations were studied for breeding and non-breeding males and females over 1 year. This study aimed to discern if this species exhibits a seasonal or aseasonal breeding pattern and whether there is a relaxation of reproductive suppression at any point in the year in non-breeding animals. The pattern of reproductive relaxation during the wetter months is similar to other African mole-rat species. Interestingly, births and pregnant breeding females were recorded throughout the year, thus indicating an aseasonal breeding strategy, despite inhabiting a region that experiences seasonal rainfall. However, there were periods of the year favouring increased reproduction to enable an increased likelihood of offspring survival. This suggests that the Mahali mole-rat may be an opportunistic breeder possibly brought about by the benefits of living in a cooperatively breeding group and potentially moving into more arid environments that were previously unexploited by the genus Cryptomys Gray, 1864. Key words: reproduction, opportunistic breeder, aseasonal, reproductive suppression, Mahali mole-rat, Cryptomys hottentotus mahali, cooperative breeding. Les rats-taupes africains ont fourni d'importants renseignements sur l'evolution de la socialite et des strategies de reproduction chez les mammiferes. Certaines especes qui n'ont pas reçu d'attention pourraient toutefois fournir encore plus d'information sur ces questions touchant a l'evolution. Le rat-taupe de Mahali (Cryptomys hottentotus mahali (Roberts, 1913)), dont la reproduction est cooperative, est une de ces especes. La masse corporelle, la morphometrie du systeme reproducteur, l'histologie des gonades et les concentrations d'hormones de reproduction dans le plasma ont ete etudiees chez des mâles et femelles reproducteurs et non reproducteurs sur une periode d'un an. L'etude visait a etablir si le motif de reproduction de cette espece est saisonnier ou non saisonnier et s'il y a relâchement de la suppression de la reproduction a quelque moment de l'annee chez les specimens non reproducteurs. Le motif de relâchement de la suppression de la reproduction durant les mois plus pluvieux est semblable a celui d'autres especes de rats-taupes africains. Des naissances et des femelles reproductrices gestantes ont notamment ete observees tout au long de l'annee, ce qui temoigne d'une strategie de reproduction non saisonniere, malgre la saisonnalite de la pluviosite dans la region etudiee. Certaines periodes de l'annee favorisent toutefois une reproduction accrue pour permettre une plus grande probabilite de survie de la progeniture. Cela refleterait la nature opportuniste de la reproduction du rat-taupe de Mahali, decoulant possiblement des avantages que conferent le fait de vivre au sein d'un groupe a reproduction cooperative et, eventuellement, le fait d'investir des milieux plus arides auparavant non exploites par le genre Cryptomys Gray, 1864. [Traduit par la Redaction] Mots-cles : reproduction, geniteur opportuniste, non saisonnier, suppression de la reproduction, rat-taupe de Mahali, Cryptomys hottentotus mahali, reproduction cooperative., Introduction The study of the subterranean family, the Bathyergidae (African mole-rats), has allowed for many essential revelations in mammalian evolution, behaviour, and physiology (Bennett and Faulkes 2000; Sherman et al. [...]

Our 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. [ABSTRACT FROM AUTHOR]

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 maybeused to stimulate the cervix of the female during copulation. These findings suggest that the Mahali mole-rat is an induced ovulator. Key words: Cryptomys, Mahali mole-rat, Cryptomys hottentotus mahali, induced, ovulation, progesterone, corpora lutea, penile spines. Resume : Le rat-taupe de Mahali (Cryptomys hottentotus mahali (Roberts, 1913)) est un rongeur souterrain social a reproduction communautaire et non saisonniere. Seule une femelle de la colonie se reproduit, la reproduction des autres femelles etant supprimee. Quand l'occasion se presente, ces femelles non reproductrices quittent la colonie natale pour echapper a cette suppression et s'accouplent avec un male non apparente pour demarrer une nouvelle colonie. L'etude avait pour but de determiner si l'ovulation des rats-taupes de Mahali est induite ou spontanee une fois que les femelles sont separees de l'effet suppresseur de la femelle reproductrice sur leur reproduction. Quinze femelles separees ont subi trois traitements, a savoir : abritees separement sans un male (A), en contact chimique, mais pas physique, avec un male vasectomise (NPC) et en contact direct avec un male vasectomise (PC). De l'urine a ete recueillie de toutes les femelles pour chacun des traitements, tous les 2 jours pendant 40 jours. Seules les femelles du traitement PC presentaient une augmentation des concentrations de progesterone, ainsi que des corps jaunes d'ovulation dans leurs ovaires. Les males presentaient en outre des epines epidermiques sur la tige penienne qui pourraient etre utilisees pour stimuler le col uterin de la femelle durant la copulation. Ces constatations donnent a penser que l'ovulation chez le rat-taupe de Mahali est induite. [Traduit par la Redaction] Mots-cles : Cryptomys, rat-taupe de Mahali, Cryptomys hottentotus mahali, ovulation induite, progesterone, corps jaunes, epines peniennes., Introduction Ovulation and subsequent reproduction in female mammals requires a considerable investment of both energy and resources. Ovulation in mammals may occur by two methods, induced or spontaneous (Milligan 1974, [...]

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. Key words: Libyan jird, Meriones libycus, absence of rainfall, reproduction, temperature, seasonality, histology. Les habitudes de reproduction de la merione de Libye (Meriones libycus Lichtenstein, 1823) dans le centre de l'Arabie saoudite ont ete examinees en l'absence de pluie. La masse corporelle, la morphometrie de l'appareil reproducteur, l'histologie des organes reproducteurs et les concentrations d'hormones des males et des femelles ont ete etudiees sur 12 mois consecutifs dans une population sauvage de meriones de Libye du centre de l'Arabie saoudite. Des etudes precedentes ont constate que la saison de reproduction des meriones de Libye dans le desert du Sahara en Algerie etait pendant les mois pluvieux du printemps. En l'absence de pluie, la temperature et la photoperiode s'averent etre d'importants declencheurs de l'activite reproductrice. Les temperatures plus fraiches et les jours plus courts de l'hiver provoquaient le debut de l'ovulation chez les femelles et l'augmentation de la taille des testicules et du diametre des canalicules seminiferes chez les males. Seulement deux grossesses ont ete observees durant la periode d'echantillonnage, durant la periode plus froide de l'hiver et du debut du printemps, coincidant avec une augmentation de la concentration de progesterone plasmatique chez les femelles. Nous avons constate que les meriones de Libye se reproduisent durant les mois plus frais de l'hiver en l'absence de pluie. L'etude corrobore les observations a l'effet que des variations de la pluviometrie et de la temperature dans les deserts secs constituent des signaux declencheurs cles du debut de la reproduction chez les petits mammiferes. [Traduit par la Redaction] Mots-cles: merione de Libye, Meriones libycus, absence de pluie, reproduction, temperature, saisonnalite, histologie., Introduction Deserts, such as those of Saudi Arabia, are harsh environments where daily and seasonal temperatures are extreme and rainfall is scant or non-existent. Solar radiation is intense and there [...]

We studied the correlates of population density and body size, growth rates, litter size, and group size in Damaraland mole-rats (Fukomys damarensis (Ogilby, 1838)) at two study sites with contrasting population densities. Group size, litter size, and the probability of recapture were independent of study site. However, body size differed between the two study sites, suggesting that population density may affect life-history traits in social mole-rats. At the low-density site (0.13 groups/ha), individuals were significantly larger and subordinate males showed higher growth rates than at the high-density site (0.41 groups/ha), which may indicate that high population density in subterranean rodents enhances pace of life. The larger size of nonreproductive individuals at the low-density site could adapt individuals at lower population densities to larger dispersal distances. Key words: aridity food distribution hypothesis, body size, Damaraland mole-rat, density dependence, ecological constraints, Fukomys damarensis, subterranean rodents. Nous avons étudié les corrélats de la densité de population et de la taille du corps, des taux de croissance, de la taille des portées et de la taille du groupe chez les rats-taupes de Damara (Fukomys damarensis (Ogilby, 1838)) en deux sites d'étude de densités de population différentes. La taille du groupe, la taille des portées et la probabilité de recapture sont indépendantes du site d'étude. Cependant, la taille du corps varie entre les deux sites, ce qui porte à croire que la densité de population pourrait avoir une incidence sur des caractères du cycle biologique de rats-taupes sociaux. Dans le site de faible densité (0,13 groupe/ha), les individus sont significativement plus gros et les mâles subordonnés présentent des taux de croissance plus grands qu'au site de forte densité (0,41 groupe/ha), ce qui pourrait indiquer qu'une forte densité de population chez les rongeurs souterrains accroît le rythme de vie. La plus grande taille des individus non reproducteurs au site de faible densité pourrait refléter une adaptation d'individus dans des sites de faible densité de population à de plus grandes distances de dispersion. [Traduit par la Rédaction] Mots-clés : hypothèse de la distribution de nourriture dans des conditions arides, taille du corps, rat-taupe de Damara, dépendance de la densité, contraintes écologiques, Fukomys damarensis, rongeurs souterrains., Introduction Population densities are shaped by the availability and distribution of resources, and ultimately, the energy available to them in their specific habitats (Robinson and Redford 1986). The variation in [...]

Abstract: The endogenous rhythmicity of the locomotor activity and subsequent entrainment by light cycles of the pygmy mouse (Mus minutoides A. Smith, 1834) was investigated under laboratory-controlled conditions. Seasonal trapping [...]

Abstract: Interpopulation variation in life-history patterns are influenced by intrinsic and extrinsic factors. Life-history patterns have been intensely studied in the eusocial African bathyergid species, largely neglecting the solitary species. [...]

Abstract: In seasonal breeders, periods of reproductive activity often coincide with high levels of glucocorticoids. We studied seven male and seven female African lesser bushbabies (Galago moholi A. Smith, 1836) [...]

Abstract: The genus Heliophobius Peters, 1846 comprises at least six cryptic, topotypical species in the Heliophobius argenteocinereus Peters, 1846 species complex. The current study investigated the breeding patterns of a [...]

Abstract: Many mammals use the change in day length to time physiological and behavioural activities on a seasonal basis. Particularly, mammals from temperate regions use photoperiod to regulate reproductive functions; [...]

Photoperiodism involves the use of both absolute measures of day length and the direction in which day length is changing as a cue for regulating seasonal changes in physiology and behaviour so that birth and lactation coincide with optimal resource availability, increasing offspring survival. Induced ovulation and opportunistic breeding is often found in species that are predominantly solitary and territorial. In this study, the photoperiodic reproductive responses of male greater red musk shrews (Crocidura flavescens (I. Geoffroy Saint-Hilaire, 1827)) were investigated in the laboratory. The presence of spermatozoa regardless of the light cycle, suggest that although the shrews are photoresponsive, they may be capable of breeding throughout the year. Significantly greater testicular volume and seminiferous tubule diameter following exposure to a short day-light cycle suggests that these animals may have breeding peaks that correspond to short days. The presence of epidermal spines on the penis indicates that the shrew is likely also an induced ovulator. Flexible breeding patterns combined with induced ovulation affords this solitary species the greatest chance of reproductive success. Key words: Crocidura flavescens, greater red musk shrew, seasonal breeding, shrew reproduction, testosterone concentration, gonad volume, seminiferous tubule diameter. Le photoperiodisme consiste en l'utilisation de mesures absolues de la longueur du jour et du sens du changement de cette longueur comme signal pour la regulation des changements physiologiques et comportementaux saisonniers permettant de faire coincider la naissance et la lactation avec la disponibilite optimale de ressources, ce qui accroit la survie de la progeniture. L'ovulation induite et la reproduction opportuniste sont souvent observees chez des especes principalement solitaires et territoriales. Dans l'etude, les reactions de reproduction photoperiodiques de musaraignes a crane plat (Crocidura flavescens (I. Geoffroy Saint-Hilaire, 1827)) males ont ete examinees en laboratoire. La presence de spermatozoides quel que soit le cycle de clarte, donne a penser que, bien que les musaraignes soient photoreactives, elles pourraient etre capables de se reproduire durant toute l'annee. Un volume des testicules et un diametre des canalicules seminiferes significativement plus grands apres une exposition a un cycle de clarte court indiqueraient que ces animaux pourraient presenter des pointes de reproduction correspondant aux journees courtes. La presence d'epines epidermiques sur le penis indique que l'ovulation des musaraignes est probablement induite. Des motifs de reproduction souples combines a l'ovulation induite conferent a cette espece solitaire la plus grande chance de succes de reproduction. [Traduit par la Redaction] Mots-cles: Crocidura flavescens, musaraigne a crane plat, reproduction saisonniere, reproduction des musaraignes, concentration de testosterone, volume des gonades, diametres des canalicules seminiferes., Introduction Animals adjust their physiology and behaviour according to environmental 'zeitgebers' to which they are entrained (Reiter 1974). Environmental regulation of reproduction is a well-studied phenomenon and annual cycles of [...]

Stable isotope analysis is frequently applied as a tool to examine dietary patterns in animals. However, some of the underlying assumptions associated with using this approach are increasingly being questioned. We carried out a controlled diet experiment on the southern African spiny mouse (Acomys spinosissimus Peters, 1852) to test a number of aspects relating to these assumptions and also examine the hypothesis that stable isotopes, especially δ[sup.15]N, can be used to provide evidence of nutritional stress. We compared the δ[sup.13]C and δ[sup.15]N values of livers and blood from animals that were fed ad libitum with animals undergoing a 10% reduction in food supply. Food-restricted animals showed no significant difference in δ[sup.15]N; however, δ[sup.13]C values of both liver and blood were depleted. Restricted animals also had a significantly lower C:N ratio. We examined the role of lipids and found following lipid extraction that both livers and lipids still showed the same separation in carbon values. Tissue-diet discrimination values were also calculated and found to be higher for both Δ[sup.13]C and Δ[sup.15]N compared with other mice species. Empirical values for discrimination rates were then compared with values calculated using an alternative method based on employing generic values and were found to be dissimilar, suggesting the use of generic values are not always appropriate. Our results highlight the need for greater understanding of the assumptions associated with using stable isotope analysis to examine diet and we suggest that studying a single species under captive conditions presents an ideal method to begin to test these hypotheses. Key words: Acomys spinosissimus, discrimination, food restriction, spiny mouse, stable isotope. Resume: L'analyse des isotopes stables est frequemment employee comme outil pour examiner les habitudes alimentaires d'animaux. Certaines des hypotheses qui sous-tendent cette approche sont toutefois de plus en plus remises en question. Nous avons mene une experience d'alimentation controlee sur la souris epineuse d'Afrique meridionale (Acomys spinosissimus Peters, 1852), afin de verifier differents aspects associes a ces hypotheses et d'examiner l'hypothese voulant que les isotopes stables, en particulier les valeurs de δ[sup.15]N, puissent etre utilises pour fournir des indices de stress nutritif. Nous avons compare des valeurs de δ[sup.13]C et δ[sup.15]N du foie et du sang d'individus nourris fi volonte a celles d'animaux assujettis aune reduction de 10 % de leur approvisionnement. Les animaux dont l'approvisionnement etait restreint ne presentaient aucune difference significative du δ[sup.15]N; cependant, les valeurs de δ[sup.13]N tant pour le foie que pour le sang etaient appauvries. Les animaux restreints presentaient egalement un rapport C:N significativement plus faible. Nous avons examine le role des lipides et constate que, apres extraction de ces derniers, les foies et les lipides presentaient toujours la meme separation de leurs valeurs de carbone. Des valeurs de discrimination tissusregime ont egalement ete calculees et etaient plus elevees, tant pour le Δ[sup.15]C que le Δ[sup.15]N, que celles d'autres especes de souris. Les valeurs empiriques des taux de discrimination ont ensuite ete comparees fi des valeurs calculees par une autre methode basee sur des valeurs generiques et se sont averees differentes, donnant a penser que l'utilisation de valeurs generiques n'est pas toujours bien avisee. Nos resultats soulignent la necessite d'une meilleure comprehension des hypotheses associees a l'utilisation de l'analyse des isotopes stables pour etudier le regime alimentaire, et nous suggerons que l'etude d'une seule espece dans des conditions de captivite constitue une methode ideale pour commencer a verifier ces hypotheses. [Traduit par la Redaction] Mots-cles: Acomys spinosissimus, discrimination, restriction alimentaire, souris epineuse, isotope stable., Introduction Stable isotope analysis has been used to answer a number of questions relating to foraging and diet; for example, quantifying reliance on different food sources (Robb et al. 2012), [...]

The locomotor activity rhythms of wild-caught Namaqua rock mice (Micaelamys namaquensis (A. Smith, 1834)) were examined under four light-cycle regimes to quantitatively describe the daily expression of locomotor activity and to study the innate relationship between activity and the light-dark cycle. Activity was always significantly higher at night than during the day; we note four trends. (1) The LD1 light cycle (12 h light: 12 h dark) established a distinct light-entrained and strongly nocturnal activity rhythm (99.11% nocturnal activity). The activity onset was prompt (zeitgeber time (ZT) 12.2 ± 0.04) and activity continued without any prominent peaks or extended times of rest until the offset of activity at ZT 23.73 ± 0.08. (2) Evidence for the internal maintenance of locomotor activity was obtained from the constant dark cycle (DD) in which locomotor activity free ran (mean τ = 23.89 h) and 77.58% of the activity was expressed during the subjective night. (3) During re-entrainment (LD2; 12 h light: 12 h dark), a nocturnal activity rhythm was re-established (98.65% nocturnal activity). (4) The inversion of the light cycle (DL; 12 h dark : 12 h light) evoked a shift in activity that again revealed dark-induced locomotor activity (95.69% nocturnal activity). Females were consistently more active than males in all of the light cycles, but only under the DD and LD2 cycles were females significantly more active than males. Although this species is considered nocturnal from field observations, information regarding its daily expression of activity and the role of light in its entrainment is lacking. To the best of our knowledge, this study is the first to report quantitatively on the species' daily rhythm of activity and to investigate its relationship to the light-dark cycle. Key words: circadian rhythm, entrainment, free-run, locomotor activity, Micaelamys namaquensis, Namaqua rock mouse. Les rythmes de l'activite locomotrice de souris de Namaqua (Micaelamys namaquensis (A. Smith, 1834)) capturees a l'etat sauvage ont ete examines pour quatre regimes de cycle lumineux afin de decrire de maniere quantitative l'expression journaliere de l'activite locomotrice et d'etudier le lien inne entre l'activite et le cycle lumiere-noirceur. L'activite etait toujours significativement plus grande la nuit que le jour; quatre tendances ont ete notees. (1) Le cycle lumineux LDI (12 h de lumiere, 12 h de noirceur) a etabli un rythme d'activite distinct entraine par la lumiere et fortement nocturne (activite a 99,11 % nocturne). Le debut de l'activite n'a pas tarde (temps de zeitgeber (ZT) 12,2 ± 0,04) et l'activite s'est poursuivie sans pointe proeminente ou longue periode de repos jusqu'a la fin de l'activite a ZT 23,73 ± 0,08. (2) Des indications du maintien interne de l'activite locomotrice ont ete obtenues du cycle de noirceur constante (DD) dans lequel l'activite locomotrice avait libre cours (τ moyen = 23,89 h) et 77,58 % de l'activite s'exprimait durant la nuit subjective. (3) Durant le reentrainement (LD2; 12 h de lumiere, 12 h de noirceur), un rythme d'activite nocturne s'est retabli (activite a 98,65 % nocturne). (4) L'inversion du cycle lumineux (DL; 12 h de noirceur, 12 h de lumiere) a provoque un changement de l'activite qui revelait encore une fois une activite locomotrice induite par la noirceur (activite a 95,69 % nocturne). Les femelles etaient uniformement plus actives que les males pour tous les cycles lumineux, mais les cycles DD et LD2 etaient les seuls durant lesquels les femelles etaient significativement plus actives que les males. Bien que cette espece soit consideree comme etant nocturne sur la base d'observations de terrain, de l'information concernant l'expression journaliere de son activite et le role de la lumiere dans l'entrainement de cette derniere fait defaut. A notre connaissance, cette etude est la premiere a rendre compte de maniere quantitative du rythme journalier de l'activite de cette espece et a examiner le lien de ce dernier avec le cycle lumiere-noirceur. [Traduit par la Redaction] Mots-cles: rythme circadien, entrainement, libre cours, activite locomotrice, Micaelamys namaquensis, souris de Namaqua., Introduction The perpetual rotation of the earth on its axis and the revolution of the earth around the sun are undoubtedly some of the strongest cyclical events to which organisms [...]

The pattern of ovulation in mammals is generally considered to be either spontaneous or induced by copulation, with environmental and social factors playing a key role in determining the specific mode of ovulation that would maximize the reproductive potential of the species. This study aims to determine whether the Namaqua rock mouse (Micaelamys namaquensis (A. Smith, 1834)) is a spontaneous or induced ovulator. Females were divided into three treatments differing in the degree of contact with a male. Namely, seven control females had no contact with a male; a further seven separated females had only chemical, auditory, and visual contact with a male; whereas six females had intermittent periods of full contact with a vasectomized male. Ovarian size, follicular development, and plasma progesterone concentrations were compared between the three treatments. Penile morphology was also investigated. Corpora lutea were found in all three treatments and the penis was smooth without any ridges or spikes, indicating that M. namaquensis is a spontaneous ovulator. Interestingly, however, the presence of a male (physical as well as just visual and olfactory) positively affected ovarian size, ovulation, and plasma progesterone concentrations. This signifies that although M. namaquensis ovulates spontaneously, male contact significantly influences ovulation rate and ultimately reproductive success. Key words: Micaelamys namaquensis, Namaqua rock mouse, corpora lutea, folliculogenesis, induced ovulation, penile morphology, progesterone, spontaneous ovulation. L'ovulation chez les mammiferes est generalement consideree comme etant soit spontanee ou induite par la copulation, des facteurs ambiants et sociaux jouant un role cle dans la determination du mode d'ovulation precis qui maximise le potentiel de reproduction d'especes donnees. L'objectif de l'etude etait de determiner si l'ovulation chez la souris Micaelamys namaquensis (A. Smith, 1834) est spontanee ou induite. Des femelles ont ete assujetties a trois traitements qui differaient selon le degre de contact avec un male : sept femelles de reference n'ont pas ete mises en contact avec un male, sept autres femelles n'ont eu que des contacts chimiques, auditifs et visuels avec un male, alors que six femelles ont ete en contact direct, de maniere intermittente, avec un male vasectomise. La taille des ovaires, le developpement folliculaire et les taux de progesterone plasmatique des trois groupes ont ete compares. La morphologie du penis a egalement ete examinee. La presence de corps jaunes a ete notee chez les femelles des trois groupes et le penis etait lisse, sans crete ni pointe, ce qui indique une ovulation spontanee chez M. namaquensis. Il est toutefois interessant de noter que la presence d'un male (physique ou seulement visuelle ou olfactive) a un effet positif sur la taille des ovaires, l'ovulation et les taux de progesterone plasmatique. Cela signifie que, bien que l'ovulation soit spontanee chez M. namaquensis, le contact avec un male a une influence significative sur le taux d'ovulation et, en bout de ligne, sur le succes de reproduction. [Traduit par la Redaction] Mots-cles: Micaelamys namaquensis, souris, corps jaune, folliculogenese, ovulation induite, morphologie du penis, progesterone, ovulation spontanee., Introduction The timing of ovulation, the release of an ovum from a mature Graafian follicle, is vital for successful reproduction (Kauffman and Rissmann 2006). Generally two patterns of ovulation are [...]

The Cape dune mole-rat (Bathyergus suillus) is a solitary, seasonally breeding, rodent mole. Body mass, reproductive tract morphometrics, ovarian histology, and plasma estrogen and progesterone concentrations were measured in females during 1 calendar year to elucidate if this species had an inclination toward seasonal breeding. Qualitative analyses of ovarian histology revealed that females retain the potential for ovulation and subsequent production of corpora lutea from early austral winter to spring (June-October). Seasonal differences were found in ovarian morphometrics and hormone concentrations that are associated with follicular activation from April and subsequent conceptions from June to November. Body mass, reproductive tract morphometrics, testicular histology, and plasma testosterone concentrations were obtained for males over the period of 1 calendar year. There was a gradual increase in seminiferous tubule diameter from May to October, which was mirrored by fluctuations in testosterone concentration. The current data support a strong seasonality to reproduction in the Cape dune mole-rat from April to October with a peak that is linked to the period of maximal rainfall within the distributional range of this species. Key words: Bathyergidae, Cape dune mole-rat, hormone concentration, mole-rat, seasonal reproduction