Rock Elephant Shrews Research Articles

Heat tolerance and evaporative cooling capacity in an arid-zone elephant shrew

Endotherms vary widely in their capacity to defend sublethal body temperature (Tb) during acute heat exposure. Interspecific variation in the upper thermal limits of small mammals remains poorly studied, particularly in taxa other than bats. We hypothesised that rupicolous elephant shrews (Macroscelidae), on account of their occupancy of above-ground rock crevices in hot habitats and rapid cursorial locomotion, have evolved pronounced heat tolerance capacities. To test this hypothesis, we quantified relationships between Tb, resting metabolic rate (RMR) and evaporative water loss (EWL) in western rock elephant shrews (Elephantulus rupestris) exposed to air temperature (Tair) approaching or exceeding Tb under conditions of low humidity representative of the study population’s arid, winter-rainfall habitat in western South Africa. Our data revealed a pronounced capacity to tolerate Tair > Tb, with E. rupestris tolerating Tair up to 48.0 ± 0.1 °C while defending Tb > 7 °C below Tair (maximum Tb = 41.64 ± 0.16 °C). Three behavioural pathways were employed to dissipate heat: open mouth panting, flattening their body posture, and nose-licking. At the highest experimental Tair values achieved, EWL increased 15.05-fold relative to normothermic levels and heat was dissipated evaporatively at rates equivalent to 174%—240% of metabolic heat production. The heat tolerance limit of Tair = 48 °C in E. rupestris is one of the highest yet recorded in a non-volant small mammal, and our data support the notion that elephant shrews possess a pronounced capacity to avoid lethal hyperthermia during acute heat exposure.

Unravelling the taxonomy and distribution of two problematic small mammal genera in the Karoo biome

South Africa harbours remarkable biological diversity with three of the 34 recognised global biodiversity hotspots placed within its borders. One of these is the Succulent Karoo, which together with the Nama-Karoo, forms the Greater Karoo region. Notwithstanding a paucity of studies from this region, it would appear that, although mammal diversity is low, endemism is high. Here, as part of the Karoo BioGaps project, we use a molecular approach to assess small mammal diversity and endemism in the Karoo. We focus on rock rats (Micaelamys) and elephant shrews (Elephantulus and Macroscelides). Using a DNA-informed identification approach, we reveal two, well supported, monophyletic clades of Micaelamys; one that corresponds to M. granti. Our study is the first to publish sequence data for this species. Furthermore, when unverified records are excluded, the range of M. granti is far smaller (∼99 000 km2) than that given by the IUCN red list assessments (236 027 km2), which lends support to the species being a Karoo endemic. Our macrosceledid samples grouped into four well supported clades of the genera Elephantulus and Macroscelides. Very high intraspecific diversity was present within E. pilicaudus compared with other species in our study and this newly described species may harbour cryptic diversity. Our geographic analyses confirm that the range of this species, previously considered to be a Nama-Karoo endemic, extends beyond this region. This study adds more information to the nominal data currently available for the species, Elephantulus pilicaudus.

Analysis of gonadotrophin-releasing hormone-1 and kisspeptin neuronal systems in the nonphotoregulated seasonally breeding eastern rock elephant-shrew (Elephantulus myurus).

Of the 18 sub-Saharan elephant-shrew species, only eastern rock elephant-shrews reproduce seasonally throughout their distribution, a process seemingly independent of photoperiod. The present study characterizes gonadal status and location/intensity of gonadotrophin-releasing hormone-1 (GnRH-1) and kisspeptin immunoreactivities in this polyovulating species in the breeding and nonbreeding seasons. GnRH-1-immunoreactive (ir) cell bodies are predominantly in the medial septum, diagonal band, and medial preoptic area; processes are generally sparse except in the external median eminence. Kisspeptin-ir cell bodies are detected only within the arcuate nucleus; the density of processes is generally low, except in the septohypothalamic nucleus, ventromedial bed nucleus of the stria terminalis, arcuate nucleus, and internal and external median eminence. Kisspeptin-ir processes are negligible at locations containing GnRH-1-ir cell bodies. The external median eminence is the only site with conspicuously overlapping distributions of the respective immunoreactivities and, accordingly, a putative site for kisspeptin's regulation of GnRH-1 release in this species. In the nonbreeding season in males, there is an increase in the rostral population of GnRH-1-ir cell bodies and density of GnRH-1-ir processes in the median eminence. In both sexes, the breeding season is associated with increased kisspeptin-ir process density in the rostral periventricular area of the third ventricle and arcuate nucleus; at the latter site, this is positively correlated with gonadal mass. Cross-species comparisons lead us to hypothesize differential mechanisms within these peptidergic systems: that increased GnRH-1 immunoreactivity during the nonbreeding season reflects increased accumulation with reduced release; that increased kisspeptin immunoreactivity during the breeding season reflects increased synthesis with increased release.

Solar Radiation during Rewarming from Torpor in Elephant Shrews: Supplementation or Substitution of Endogenous Heat Production?

Many small mammals bask in the sun during rewarming from heterothermy, but the implications of this behaviour for their energy balance remain little understood. Specifically, it remains unclear whether solar radiation supplements endogenous metabolic thermogenesis (i.e., rewarming occurs through the additive effects of internally-produced and external heat), or whether solar radiation reduces the energy required to rewarm by substituting (i.e, replacing) metabolic heat production. To address this question, we examined patterns of torpor and rewarming rates in eastern rock elephant shrews (Elephantulus myurus) housed in outdoor cages with access to either natural levels of solar radiation or levels that were experimentally reduced by means of shade cloth. We also tested whether acclimation to solar radiation availability was manifested via phenotypic flexibility in basal metabolic rate (BMR), non-shivering thermogenesis (NST) capacity and/or summit metabolism (Msum). Rewarming rates varied significantly among treatments, with elephant shrews experiencing natural solar radiation levels rewarming faster than conspecifics experiencing solar radiation levels equivalent to approximately 20% or 40% of natural levels. BMR differed significantly between individuals experiencing natural levels of solar radiation and conspecifics experiencing approximately 20% of natural levels, but no between-treatment difference was evident for NST capacity or Msum. The positive relationship between solar radiation availability and rewarming rate, together with the absence of acclimation in maximum non-shivering and total heat production capacities, suggests that under the conditions of this study solar radiation supplemented rather than substituted metabolic thermogenesis as a source of heat during rewarming from heterothermy.

The forgotten pollinators – First field evidence for nectar-feeding by primarily insectivorous elephant-shrews

Pollination of plants by non-flying mammals, such as mice (Rodentia), is a rarely observed phenomenon. Previously, elephant-shrews (Macroscelidea), small African mammals looking similar to mice, but not being related to them, were believed to be purely insectivorous and occasional flower visits of elephant-shrews in captivity were interpreted as a by-product of the search for insects. Only recently it was demonstrated that under lab conditions elephant-shrews regularly lick nectar from flowers. However, field observations of flower-visiting elephant-shrews and their role as pollinators were completely missing. Here I present the first evidence for flower visits and nectar consumption for elephant-shrews in the field. With video camcorders and infrared lights I recorded Cape rock elephant-shrews (Elephantulus edwardii) beside Namaqua rock mice (Micaelamys namaquensis) visiting flowers of the Pagoda lily (Whiteheadia bifolia, Asparagaceae) under natural conditions in the Namaqualand of South Africa. With their long tongues, the elephant-shrews visited the flowers non-destructively, definitely licking nectar, but not eating insects. The footage clearly shows that the elephant-shrews’ fur around their long noses touches the pollen-sacs and the stigmas of the flowers and that the animals’ fur is being dusted with pollen. As the elephant-shrews visited several flowers of different plants, it is obvious that they transfer pollen between the plants. This observation contributes to the knowledge about the behaviour of these representatives of a unique clade of small African mammals – especially in their natural habitat. With their behavioural and anatomical uniqueness, it is not unlikely that elephant-shrews even play a role as selective force driving floral evolution. Appendices:Additional supporting information is to be found:Appendix I. With its long tongue Elephantulus edwardii licks nectar from Whiteheadia bifolia flowers, getting dusted with pollen on its nose. Infrared video.http://www.pollinationecology.org/user-files/ JPE349_Appendix1.mp4Appendix II. Micaelamys namaquensis licking nectar from Whiteheadia bifolia flowers, getting dusted with pollen on its nose. Infrared video.http://www.pollinationecology.org/user-files/JPE349_Appendix2.aviAppendix III. Micaelamys namaquensis feeding on pollen-sacs of Whiteheadia bifolia flowers. Infrared video.http://www.pollinationecology.org/user-files/JPE349_Appendix3.avi

Variation in body temperature is related to ambient temperature but not experimental manipulation of insulation in two small endotherms with different thermoregulatory patterns

AbstractMaintaining a high and constant body temperature (T b) is thought to enhance performance in endotherms, but such a thermoregulatory pattern is energetically expensive. Thus, some variation in T b is probably universal among endotherms, and several recent attempts have been made to generalize the factors that should cause this variation. Two factors that may be closely tied to the thermoregulatory pattern expressed are the cost of thermoregulation and food availability. To test these predictions, we measured T b of eastern rock elephant shrews (Elephantulus myurus; a traditionally defined heterotherm) and Namaqua rock mice (Micaelamys namaquensis; a homeotherm) in the field and under semi‐natural conditions after experimentally reducing insulation by shaving a patch of dorsal fur. After accounting for ambient temperature (T a), there was no significant difference in the level of variation in T b between shaven and unshaven elephant shrews. In rock mice, the increase in heat loss paradoxically led to decreased variation in T b in the field, but no effect was evident in captivity. Furthermore, as predicted, both species displayed significantly less variation in T b under semi‐natural conditions when given food ad libitum and predation risk involved with obtaining that food was low. Our results show that small mammals, both homeothermic and heterothermic, are capable of altering their thermoregulatory patterns in response to ecological conditions (e.g. rapid changes in food availability). However, increasing the cost of thermoregulation, at least as it was done in this experiment, does not appear to affect the expression of T b as strongly as does T a.

Seasonal changes in thermogenesis of a free-ranging afrotherian small mammal, the Western rock elephant shrew (Elephantulus rupestris)

We report on the seasonal metabolic adjustments of a small-sized member of the phylogenetically ancient Afrotheria, the Western rock elephant shrew (Elephantulus rupestris). We recorded body temperature (T (b)) patterns and compared the capacity for adrenergically induced nonshivering thermogenesis (NST) in E. rupestris captured in the wild in summer and winter. Noradrenaline (NA) treatment (0.4-0.5mg/kg, s.c.) induced a pronounced elevation in oxygen consumption compared to controls (saline), and the increase in oxygen consumption following injection of NA was 1.8-fold higher in winter compared to summer. This suggests that the smaller members of Afrotheria possess functional brown adipose tissue, which changes in thermogenic capacity depending on the season. Torpor was recorded in both seasons, but in winter the incidence of torpor was higher (n=205 out of 448 observations) and minimal T (b) during torpor was lower (T (b)min: 11.9°C) than in summer (n=24 out of 674 observations; T (b)min: 26°C). In addition to cold, high air humidity emerged as a likely predictor for torpor entry. Overall, E. rupestris showed a high degree of thermoregulatory plasticity, which was mainly reflected in a variable timing of torpor entry and arousal. We conclude that E. rupestris exhibits seasonal metabolic adjustments comparable to what has been long known for many Holarctic rodents.

Body temperature patterns in two syntopic elephant shrew species during winter

We measured body temperature (T b) in free-ranging individuals of two species of elephant shrews, namely western rock elephant shrews ( Elephantulus rupestris) and Cape rock elephant shrews ( E. edwardii), during winter in a winter-rainfall region of western South Africa. These syntopic species have similar ecologies and morphologies and thus potential for large overlaps in diet and habitat use. Unexpectedly, they displayed different T b patterns. Western rock elephant shrews were heterothermic, with all individuals decreasing T b below 30 °C on at least 34% of nights. The level of heterothermy expressed was similar to other species traditionally defined as daily heterotherms and was inversely related to T a, as is commonly seen in small heterothermic endotherms. In contrast, Cape rock elephant shrews rarely allowed their T b to decrease below 30 °C. The level of heterothermy was similar to species traditionally defined as homeotherms and there was no relationship between the level of heterothermy expressed and T a. In both species, the minimum daily T b was recorded almost exclusively at night, often shortly before sunrise, although in some individuals minimum T b occasionally occurred during the day. The interspecific variation in T b patterns among Elephantulus species recorded to date reiterates the importance of ecological determinants of heterothermy that interact with factors such as body mass and phylogeny.

Nectar feeding by the Cape rock elephant-shrew Elephantulus edwardii (Macroscelidea) — A primarily insectivorous mammal pollinates the parasite Hyobanche atropurpurea (Orobanchaceae)

Cape rock elephant-shrews, Elephantulus edwardii (Macroscelidea) were found to be pollinators of Hyobanche atropurpurea (Orobanchaceae), a member of a holoparasitic plant genus, lacking up to now any detailed pollinator observations. The elephant-shrews were live-trapped near the plants in the Western Cape of South Africa. One animal was released in a terrarium, containing the plants. It licked nectar with its long and slender tongue while being dusted with pollen and touching the stigmas of the flowers with its nose and the fur above the snout. H. atropurpurea pollen was found in swabs of the fur around noses and snouts as well as in the faeces of captured animals. The occurrence of pollen in the faeces of the elephant-shrews is likely a result of grooming their fur as they visited the flowers without eating or damaging them. This is one of the first records of pollinating, nectar-drinking elephant-shrews, contributing to the very scarce knowledge about the behaviour of those primarily insectivorous animals, as well as small mammal pollination.

Does torpor of elephant shrews differ from that of other heterothermic mammals?

Torpor bouts of elephant shrews are intermediate in duration to those of daily heterotherms and hibernating mammals, but their body temperatures (Tbs) and metabolic rates are very low and similar to those of hibernating mammals. We quantified the thermal physiology of the Cape rock elephant shrew (Elephantulus edwardii), a species endemic to high-altitude regions of South Africa, where winters are cold and wet, and tested whether it displays multiday torpor characteristic of hibernators at low ambient temperature (Ta). E. edwardii regularly displayed torpor over a wide range of Tas. Occurrence of torpor and duration of torpor bouts increased with decreasing Ta. Whereas normothermic Tb was stable, Tb in torpid individuals fell with Ta. The mean Tb 2 Ta differential at the minimum Tb was 0.7uC, and the mean minimum Tb at Ta 8.9uC was 9.3uC. Duration of torpor bouts ranged from 6.5 to 44 h and was correlated negatively with Ta and Tb during torpor. Time required for the reduction of Tb to a Tb 2 Ta differential of ,2.0uC was faster for .1-day torpor bouts than those lasting 1 day, suggesting that the duration of a bout might be determined at the beginning, not during, a bout. The nature of heterothermy in E. edwardii seems qualitatively similar to that of other elephant shrews, although torpor is somewhat deeper and longer in this species. Temporal patterns of torpor in E. edwardii differ from those of most cold-climate hibernators, likely for ecological rather than physiological reasons.

Sticky snack for sengis: The Cape rock elephant-shrew, Elephantulus edwardii (Macroscelidea), as a pollinator of the Pagoda lily, Whiteheadia bifolia (Hyacinthaceae)

Following the recent discovery of rodent pollination in the Pagoda lily, Whiteheadia bifolia (Hyacinthaceae) in South Africa, now the Cape rock elephant-shrew, Elephantulus edwardii (Macroscelidea, Afrotheria) is reported as an additional pollinator. Elephant-shrews, live-trapped near W. bifolia plants, were released in two terraria, containing the plants. The animals licked nectar with their long and slender tongues while being dusted with pollen and touching the stigmas of the flowers with their long and flexible noses. The captured elephant-shrews had W. bifolia pollen in their faeces, likely as a result of grooming their fur as they visited the flowers without eating or destroying them. The animals mostly preferred nectar over other food. This is the first record of pollination and nectar consumption in the primarily insectivorous E. edwardii, contributing to the very sparse knowledge about the behaviour of this unique clade of African mammals, as well as pollination by small mammals.

Nuclear organization of cholinergic, putative catecholaminergic and serotonergic nuclei in the brain of the eastern rock elephant shrew, Elephantulus myurus

The organization of the nuclear subdivisions of the cholinergic, putative catecholaminergic and serotonergic systems of the brain of the elephant shrew ( Elephantulus myurus) were determined following immunohistochemistry for choline acetyltransferase, tyrosine hydroxylase and serotonin, respectively. This was done in order to determine if differences in the nuclear organization of these systems in comparison to other mammals were evident and how any noted differences may relate to specialized behaviours of the elephant shrew. The elephant shrew belongs to the order Macroscelidea, and forms part of the Afrotherian mammalian cohort. In general, the organization of the nuclei of these systems resembled that described in other mammalian species. The cholinergic system showed many features in common with that seen in the rock hyrax, rodents and primates; however, specific differences include: (1) cholinergic neurons were observed in the superior and inferior colliculi, as well as the cochlear nuclei; (2) cholinergic neurons were not observed in the anterior nuclei of the dorsal thalamus as seen in the rock hyrax; and (3) cholinergic parvocellular nerve cells forming subdivisions of the laterodorsal and pedunculopontine tegmental nuclei were not observed at the midbrain/pons interface as seen in the rock hyrax. The organization of the putative catecholaminergic system was very similar to that seen in the rock hyrax and rodents except for the lack of the rodent specific C3 nucleus, the dorsal division of the anterior hypothalamic group (A15d) and the compact division of the locus coeruleus (A6c). The nuclear organization of the serotonergic system was identical to that seen in all eutherian mammals studied to date. The additional cholinergic neurons found in the cochlear nucleus and colliculi may relate to a specific acoustic signalling system observed in elephant shrews expressed when the animals are under stress or detect a predator. These neurons may then function to increase attention to this type of acoustic signal termed foot drumming.

The molecular and biochemical basis of nonshivering thermogenesis in an African endemic mammal, Elephantulus myurus

Uncoupling protein 1 (UCP1) mediated nonshivering thermogenesis (NST) in brown adipose tissue (BAT) is an important avenue of thermoregulatory heat production in many mammalian species. Until recently, UCP1 was thought to occur exclusively in eutherians. In the light of the recent finding that UCP1 is already present in fish, it is of interest to investigate when UCP1 gained a thermogenic function in the vertebrate lineage. We elucidated the basis of NST in the rock elephant shrew, Elephantulus myurus (Afrotheria: Macroscelidea). We sequenced Ucp1 and detected Ucp1 mRNA and protein restricted to brown fat deposits. We found that cytochrome c oxidase activity was highest in these deposits when compared with liver and skeletal muscle. Consistent with a thermogenic function of UCP1 isolated BAT mitochondria showed increased state 4 respiration in the cold, as well as palmitate-induced, GDP-sensitive proton conductance, which was absent in liver mitochondria. On the whole animal level, evidence of thermogenic function was further corroborated by an increased metabolic response to norepinephrine (NE) injection. Cold acclimation (18 degrees C) led to an increased basal metabolic rate relative to warm acclimation (28 degrees C) in E. myurus, but there was no evidence of additional recruitment of NE-induced NST capacity in response to cold acclimation. In summary, we showed that BAT and functional UCP1 are already present in a member of the Afrotheria, but the seasonal regulation and adaptive value of NST in Afrotherians remain to be elucidated.

Coalescence methods reveal the impact of vicariance on the spatial genetic structure of Elephantulus edwardii (Afrotheria, Macroscelidea)

Within the Macroscelidea 15 species of elephant-shrews are recognized, of which nine occur in the southern African subregion. The Cape rock elephant-shrew (Elephantulus edwardii) is the only strictly endemic South African elephant-shrew species. Recent distribution data suggest that E. edwardii is continuously distributed from Namaqualand in the Western Cape Province to Port Elizabeth in the Eastern Cape Province. Molecular sequences from the mitochondrial cytochrome b gene and variable control region indicate significant substructure within the Cape rock elephant-shrew across its distribution. Our data unequivocally showed the presence of a northern Namaqua and central Fynbos clade with four evolutionary lineages identified within the latter. The geographical delimitation of the northern and central clades corresponds closely with patterns reported for other rock-dwelling vertebrate species, indicating a shared biogeographical history for these taxa in South Africa. A coalescent method revealed the effects of ancestral polymorphism in shaping the Namaqua and Fynbos populations since their divergence ~1.7 million years ago. Furthermore, our analyses uncovered a distinct Karoo lineage(s) that does not correspond to any of the previously described and/or currently recognized species, and we therefore argue for the possible recognition of a new sister taxon to E. edwardii. The taxonomic affinities of this clade were examined by sequencing corresponding regions from the type specimens of species described in the past, but which presently are synonimized within E. edwardii. Our results reveal the morphological misidentification of one of these types, accentuating the problems of field identification.

The presence and function of uncoupling proteins in a phylogenetically ancient mammal, the rock elephant shrew, Elephantulus myurus

The presence and function of uncoupling proteins in a phylogenetically ancient mammal, the rock elephant shrew, Elephantulus myurus

Noradrenalin induces thermogenesis in a phylogenetically ancient eutherian mammal, the rock elephant shrew, Elephantulus myurus

The evolution of endothermy is thought to have been facilitated by the advent of endothermic energy sources such as brown adipose tissue (BAT), the principal site of non-shivering thermogenesis (NST). In marsupials, heat is primarily produced through shivering and NST in skeletal muscle because BAT is either absent or appears to be non-functional. The most basal group of the eutherian lineage are the Afrotheria. Rock elephant shrews, Elephantulus myurus are amongst the smallest members of the Afrotheria and are also known to use exogenous passive heating. The aim of this study was to determine whether the reliance on passive heating compromised the capacity for thermogenesis in E. myurus. We measured the thermogenic response to noradrenalin (NA) injection in E. myurus acclimated to short photoperiod. The thermogenic response at 25 degrees C was 1.58 ml O(2) g(-1) h(-1). We used phylogenetically independent analyses to establish how this thermogenic response compared to other eutherians that display classical NST. The thermogenic response of E. myurus was not significantly different from phylogenetically independent allometric predictions. However, it is unclear whether this thermogenic response is indicative of classical NST and molecular data are required to verify the presence of BAT and UCPs in elephant shrews.

Daily torpor during the active phase in free‐ranging rock elephant shrews (Elephantulus myurus)

AbstractIn highly seasonal environments animals that use daily torpor usually do so during the rest phase. In subtropical and tropical environments, however, daily torpor may not necessarily be confined to the animals' rest phase. Animals may display torpor during the active phase. We investigated the daily rhythms and seasonal rhythms of body temperature (Tb) in normothermic and torpid free‐ranging rock elephant shrews Elephantulus myurus at Weenen Game Reserve, KwaZulu‐Natal, South Africa. Tbs were recorded using miniature dataloggers from May 2001 to May 2002. Daily patterns of Tb in normothermic E. myurus suggested polyphasic Tb patterns that nevertheless suggested a rest phase that was coincident with the daytime. When the elephant shrews used torpor, the lowest Tbs were observed during the night‐time, such that torpor was used during the coldest part of the night and arousal was associated with the 3‐h period around sunrise. We suggest that the principal benefit of a flexible daily rhythm of Tb was that it facilitated arousal by passive exogenous heating using ambient temperature cycles.

Exogenous passive heating during torpor arousal in free-ranging rock elephant shrews, Elephantulus myurus

In the laboratory rock elephant shrews (Elephantulus myurus; mean body mass 56.6g) displayed the lowest torpor T bmin yet recorded (ca. 5°C) in a placental daily heterotherm. It was unknown whether these low T bs were characteristic of daily heterothermy in free-ranging animals. It was also unclear how cost effective these low T bs were since considerable energy is required to arouse from low T bs on a daily basis. We continuously measured body temperature once every hour for 85days in 13 free-ranging E. myurus from May to August 2001 (winter) in Weenen Game Reserve, KwaZulu-Natal, South Africa. We recorded a total of 412 torpor bouts. Free-ranging E. myurus had a high propensity for torpor with females displaying higher torpor frequency than males. The lowest T b recorded was 7.5°C at T a=2.7°C and the minimum torpor T b was strongly correlated with ambient temperature. Torpor arousal was tightly coupled with ambient temperature cycles. Low torpor T bmin at low T as was therefore cost-effective because the animals offset the high cost of arousal through exogenous passive heating. Laboratory studies under constant ambient temperatures may therefore underestimate the energetic benefits of torpor in free-ranging small mammals that inhabit regions where seasonality is moderate.

The effect of feeding immature Karoo paralysis ticksIxodes rubicundus (Acari: Ixodidae) on the metabolic rate of the rock elephant shrew

The effect of feeding immature Karoo paralysis ticks (Ixodes rubicundus) on the resting metabolic rate (RMR) of their principal natural host, the rock elephant shrew (Elephantulus myurus), was investigated under laboratory conditions. The elephant shrews were artificially infested with numbers of ticks simulating natural burdens. The RMR of the elephant shrews was quantified by measuring the oxygen consumption in an open through-flow system. The RMR of hosts infested only with larvae did not differ from that of the control group. Those infested with nymphs, or nymphs and larvae, had significantly lower RMR's compared to the control animals. There were no signs of paralysis in any of the infested hosts.

The Relative host status of rock elephant shrewsElephantulus myurusand Namaqua rock miceAethomys namaquensisfor economically important ticks

Several tick species of medical and veterinary importance occur in the southern Orange Free State. The purpose of the present study was to determine the host status of rock elephant shrews ( Elephantulus myurus) and Namaqua rock mice ( Aethomys namaquensis) for these ticks. Infestation levels were used as a criterion. The seasonal abundances of the ticks as well as the effects of landscape topography and sex of the host on infestation levels were also investigated. Incidental observations were made on the pouched mouse (Saccostomys campestris). No adult ticks were recovered from any of these small mammals. Seven tick species were found on the elephant shrews of which only Ixodes rubicundus and Rhipicephalus punctatus occurred in high numbers on a large proportion of the animals. Both these ticks cause paralysis in domestic stock. The Namaqua rock mice harboured eight tick species. Only Haemaphysalis leachi/spinulosa and R. punctatus had a relative abundance exceeding 15%. Three of the 10 pouched mice exam...