Search

Oxidative stress plays a crucial role in mediating life-history processes, where it can compromise survival and reproduction through harmful alterations to DNA, lipids, and proteins. In this study, we investigated oxidative stress in Cape ground squirrels (Xerus inauris), a longer-lived African ground squirrel species with a high reproductive skew and unique life history strategies. We measured oxidative stress as total antioxidant capacity (TAC), total oxidant status (TOS), and an oxidative stress index (OSI) in blood plasma from individuals of approximately known ages. Our results reveal a distinct pattern of decreasing oxidative stress with age, consistent across both sexes. Females exhibited lower OSI and TOS levels than males. Males employing different life-history strategies, namely natal (staying at home), had significantly lower oxidative stress compared to the band (roaming male groups), likely due to variations in metabolic rate, activity, and feeding rates. However, both strategies exhibited reduced oxidative stress with age, though the underlying mechanisms require further investigation. We propose that selection pressures favoring survival contributed to the observed reduction in oxidative stress with age, potentially maximizing lifetime reproductive success in this species. [ABSTRACT FROM AUTHOR]

Oxidative stress plays a crucial role in mediating life-history processes, where it can compromise survival and reproduction through harmful alterations to DNA, lipids, and proteins. In this study, we investigated oxidative stress in Cape ground squirrels (Xerus inauris), a longer-lived African ground squirrel species with a high reproductive skew and unique life history strategies. We measured oxidative stress as total antioxidant capacity (TAC), total oxidant status (TOS), and an oxidative stress index (OSI) in blood plasma from individuals of approximately known ages. Our results reveal a distinct pattern of decreasing oxidative stress with age, consistent across both sexes. Females exhibited lower OSI and TOS levels than males. Males employing different life-history strategies, namely natal (staying at home), had significantly lower oxidative stress compared to the band (roaming male groups), likely due to variations in metabolic rate, activity, and feeding rates. However, both strategies exhibited reduced oxidative stress with age, though the underlying mechanisms require further investigation. We propose that selection pressures favoring survival contributed to the observed reduction in oxidative stress with age, potentially maximizing lifetime reproductive success in this species.

The ecology, life histories, and physiology of many animals are changing in response to human-induced climate change. As the Earth warms, the ability of an animal to thermoregulate becomes ecologically and physiologically significant. Morphological adaptations to warmer temperatures include larger appendages and smaller bodies. We examined morphological features in a ground squirrel, Xerus inauris , living in the arid zones of South Africa, to examine whether squirrels have responded to increases in temperature and changes in seasonal rainfall with morphological modifications over the last 18 years. We found that over time, absolute hindfoot length and proportional hindfoot length increased, while spine length decreased. These changes are consistent with ecogeographical rules (Allen's rule and Bergmann's rule) and provide evidence in support of "shape-shifting" in response to climatic warming. Body mass also increased with time; however, these changes were not consistent with Bergmann's rule, indicating that mass is influenced by other ecological factors (e.g. resource availability). Our study adds to the growing evidence that animal morphologies are changing in response to changing climatic conditions, although it remains to be seen whether these changes are adaptive. [ABSTRACT FROM AUTHOR]

Male mating strategies respond to female availability such that variation in resources that affect spatial distribution can also alter cost–benefit tradeoffs within a population. In arid‐adapted species, rainfall alters reproduction, behavior, morphology, and population density such that populations differing in resource availability may also differ in successful reproductive strategies. Here, we compare two populations of Cape ground squirrels (Xerus inauris), a sub‐Saharan species with year‐round breeding and intense mating competition. Unlike most mammals where males resort to aggressive interactions over females, male X. inauris are tolerant of one another, relying instead on other nonaggressive pre‐ and postcopulatory strategies to determine reproductive success. Our findings suggest that differences in resource availability affect female distribution, which ultimately leads to intraspecific variation in male reproductive tactics and sexual morphology. Sperm competition, assessed by reproductive morphometrics, was more pronounced in our high resource site where females were distributed evenly across the landscape, whereas dominance seemed to be an important determinant of success in our low resource site where females were more aggregated. Both sites had similar mating intensities, and most males did not sire any offspring. However, our low resource site had a higher variance in fertilization success with fewer males siring multiple offspring compared with our high resource site where more individuals were successful. Our results lend support to resource models where variations in female spatial distribution attributed to environmental resources ultimately impact male reproductive behaviors and morphology. [ABSTRACT FROM AUTHOR]

Body size impacts nearly all aspects of an animal's life and can be subject to considerable variation in response to differences in climate and resource availability. We studied the impact of temperature and resource availability on arid‐living Cape ground squirrels (Xerus inauris), relative to body size and degree of sexual dimorphism, over three locations differing in annual rainfall and temperature to test Bergmann's rule, the resource rule and Rensch's rule. We found that squirrels were the largest where resources were the highest and temperatures were the lowest but squirrels were similar in mass where resources were medium or low and temperatures medium and highest, partially supporting Bergmann's rule and the resource rule. Hind‐feet were the largest where resources were medium and temperatures were medium and similarly small in low and high resource and high‐ and low‐temperature areas. The degree of sexual dimorphism of hind‐foot and mass was constant no matter the resource abundance or temperature, suggesting no impact of resource availability or temperature on the degree of sexual dimorphism, contradicting Rensch's rule. Our findings suggest that, while resource availability and temperature may have an impact on body size, other mechanisms may be important in limiting both body size and degree of sexual dimorphism in this species. [ABSTRACT FROM AUTHOR]

The tapeworm Taenia crassiceps has an indirect life cycle. Occasionally, metacestode stages have been reported from aberrant hosts as dogs, cats, lemurs and humans. This study describes an unusual series of serious cysticercosis cases: an 18-month-old male Yorkshire terrier dog with pleural cysticercosis accompanied by a cough, a 10-year-old male Shih Tzu dog with subcutaneous cysticercosis as well as a Cape ground squirrel and a Senegal bushbaby, both with generalised cysticercosis. Surgery was successful only in the Shih Tzu. The Yorkshire terrier died a few hours after surgery, while the Cape ground squirrel was euthanised and the Senegal bushbaby died before surgery. Cysticerci from the four cases were identified morphologically and using molecular methods. Fragments of genes coding for cytochrome oxidase subunit 1 were sequenced for each of the four isolates. Their affiliation to T. crassiceps was confirmed by comparison with the sequence data of other isolates available in the GenBank database. In general, the comparison of sequences of all isolates showed low variability in nucleotide composition (at most five positions). The cases from captive zoo animals represent the first findings of T. crassiceps in the Cape ground squirrel and Senegal bushbaby. The optimal treatment of cysticercosis caused by T. crassiceps remains unclear. Successful attempts usually include extensive surgical interventions and prolonged anthelmintic treatment. Chemotherapeutic options are limited. Although regular deworming targeting intestinal helminths of dogs is not effective against T. crassiceps cysticerci, it may help to prevent contamination of the environment by tapeworm eggs contained in dog faeces and reduce the risk of infection for susceptible animals and humans.

The tapeworm Taenia crassiceps has an indirect life cycle. Occasionally, metacestode stages have been reported from aberrant hosts as dogs, cats, lemurs and humans. This study describes an unusual series of serious cysticercosis cases: an 18-month-old male Yorkshire terrier dog with pleural cysticercosis accompanied by a cough, a 10-year-old male Shih Tzu dog with subcutaneous cysticercosis as well as a Cape ground squirrel and a Senegal bushbaby, both with generalised cysticercosis. Surgery was successful only in the Shih Tzu. The Yorkshire terrier died a few hours after surgery, while the Cape ground squirrel was euthanised and the Senegal bushbaby died before surgery. Cysticerci from the four cases were identified morphologically and using molecular methods. Fragments of genes coding for cytochrome oxidase subunit 1 were sequenced for each of the four isolates. Their affiliation to T. crassiceps was confirmed by comparison with the sequence data of other isolates available in the GenBank database. In general, the comparison of sequences of all isolates showed low variability in nucleotide composition (at most five positions). The cases from captive zoo animals represent the first findings of T. crassiceps in the Cape ground squirrel and Senegal bushbaby. The optimal treatment of cysticercosis caused by T. crassiceps remains unclear. Successful attempts usually include extensive surgical interventions and prolonged anthelmintic treatment. Chemotherapeutic options are limited. Although regular deworming targeting intestinal helminths of dogs is not effective against T. crassiceps cysticerci, it may help to prevent contamination of the environment by tapeworm eggs contained in dog faeces and reduce the risk of infection for susceptible animals and humans. [ABSTRACT FROM AUTHOR]

For food caching to be adaptive, the benefits of recovery must outweigh the costs of storing an item. One of the costs to cachers is the risk of theft, and therefore, it is predicted that individuals may be sensitive to this theft and show various behavioural strategies to minimise it. In this study, we gave wild Cape ground squirrels ( Xerus inauris) a choice between two different coloured items of the same food type: one item with a specific colour that was always artificially removed when cached and the other item with a different colour that was not removed when cached. During the choice presentations, subjects reduced the amount they consumed and cached of the food items with the colour that was experimentally removed when cached, despite the two items only differing in caching pay-off. This avoidance to choose the food with the colour that was removed occurred over time, which suggests that subjects were using information about the item's pay-off during cache recovery and this then impacted on successive decisions. This study highlights how the sensitivity to a food item's pay-off can affect an individual's choice towards items that offer the greater overall reward. [ABSTRACT FROM AUTHOR]

Burrowing and foraging of semi-fossorial rodents can affect species distribution and composition. Ground squirrels dig large burrow systems for refuge from predators and temperature extremes. Burrowing and foraging around burrows by squirrels may affect habitat and resource distributions for other organisms. We examined the impact of Cape ground squirrels ( Xerus inauris) on vegetation, small mammals and beetles during winter and summer in grasslands on the edge of the Namib Desert. At each burrow system and paired control site without burrows, we estimated plant cover and height using quadrats (N = 8 paired sites), small mammal abundance and species richness using mark-recapture techniques (N = 8 paired sites) and beetle abundance and species richness using pitfall traps (N = 6 paired sites, winter only). Squirrel burrowing and foraging activities resulted in lower plant cover and height, higher small mammal abundance and lower beetle abundance and species richness. Squirrels also reduced more plant cover in winter compared to summer, but had no effect on small mammal species richness. Furthermore, plant cover and height were higher in summer, whereas small mammal abundance and species richness were higher in winter. Our results suggest that Cape ground squirrels are important ecosystem engineers that influence plant and animal communities in the Namib Desert grasslands. [ABSTRACT FROM AUTHOR]

When social animals cache food close to their burrow, the potential for an audience member to observe the event is significantly increased. As a consequence, in order to reduce theft it may be advantageous for animals to be sensitive to certain audience cues, such as whether they are attentive or not to the cache event. In this study, observations were made on three groups of Cape ground squirrels ( Xerus inauris) in their natural habitat when they cached provisioned food items. When individuals cached within 10 m of conspecifics, we recorded the attentiveness (i.e. whether any audience members were orientated towards the cacher, had direct line of site and were not engaged in other activities) and identity of audience members. Overall, there was a preference to cache when audience members were inattentive rather than attentive. Additionally, we found rank effects related to cache avoidance whereby high-ranked individuals showed less avoidance to cache when audience members were attentive compared to medium- and low-ranked individuals. We suggest this audience sensitivity may have evolved in response to the difference in competitive ability amongst the ranks in how successful individuals are at winning foraging competitions. This study demonstrates that Cape ground squirrels have the ability to not only monitor the presence or absence of conspecifics but also discriminate individuals on the basis of their attentive state. [ABSTRACT FROM AUTHOR]

Burrowing mammals that disproportionately affect their physical environment, creating habitat and providing resources for other organisms, are considered ecosystem engineers. Such modifications are particularly important in dry grassland environments, where low precipitation and soil nutrients limit plant growth. We tested 5 hypotheses about the impact of Cape ground squirrels (Xerus inauris) on plants and animals in a semi-arid grassland of South Africa. At each burrow cluster and paired control site without burrows, we estimated plant cover, height, and richness using quadrats, and invertebrate and small mammal abundance and richness using pit-fall traps and mark-recapture, respectively. We determined nitrogen concentrations in grasses on and off burrows and measured carbon and nitrogen stable isotopes in plants and squirrel hair to determine squirrel diet. Burrows had greater plant cover and richness, particularly more shrubby vegetation, but plant height and nitrogen concentrations did not differ on and off burrows. Invertebrate and small mammal abundance and richness were greater on burrows. Squirrel disturbances in semi-arid grassland improved conditions for disturbance-dependent shrubs, which were rarely consumed by squirrels but are valuable forage for antelope and provide cover for invertebrates and small mammals. By altering habitat for plants reliant on disturbance, Cape ground squirrels enhance grassland biodiversity. • Environmental modifications by burrowing mammals are critical to semi-arid grasslands. • Squirrel burrowing led to greater plant cover and richness, particularly in shrubs. • Small mammal and invertebrate abundance and richness were higher on burrow areas. • Squirrel activity in semi-arid grasslands increased the plant and animal diversity. [ABSTRACT FROM AUTHOR]

Differential reproductive success commonly reflects variations in reproductive physiology, behavior, and morphology. In some species, competition among males results in the evolution of alternative reproductive tactics that confer a fitness advantage relating to social status, density, or myriad other factors. In the Cape ground squirrel ( Xerus inauris), a species that is highly competitive but lacks typical mammalian aspects of intrasexual competition (e.g., territoriality and aggression), 2 alternative reproductive tactics occur relating to dispersal. While physiological and behavioral differences have been demonstrated between dispersed males and males that delay dispersal, we used microsatellite markers to quantify variations in reproductive success between tactics. We found that dispersed males are in better body condition with larger home ranges likely allowing greater encounter frequencies with estrous females. However, we found no difference in copulation frequency between tactics, and the decision to delay dispersal does not preclude reproduction. Over 70% of males did not sire any offspring, yet the average number of offspring sired was equal between tactics. Thus, all males are equally likely of copulating, but paternity is strongly skewed toward a few males regardless of tactic. Natal philopatry may be a condition-dependent tactic that does not reduce reproductive success. [ABSTRACT FROM AUTHOR]

The article discusses the impact of black-backed jackal towards small carnivores, and prey. It mentions that the black-backed jackal is a mesocarnivore which inhabits two areas of the African continent. It reflects on the role of mesocarnivores in the ecosystem which is an animal whose diet consists of 50-70% meat with the balance consisting of non-vertebrate foods which may include fungi, fruits, and other plant material.

Predator harassment is an anti-predator behaviour that may increase an individual's risk of predation, as individuals approach, threaten and harass a potential predator, yet this behaviour is still not well understood. The Cape ground squirrel (Xerus inauris) is a highly social facultative cooperative breeder from southern Africa that harasses several species of venomous snakes. We examined whether harassment was part of alloparental care by comparing harassment behaviours among different age and sex classes in Cape ground squirrel social groups. We also assessed how individuals adjusted their behaviour dependent on levels of risk by examining the Cape ground squirrel's harassment behaviour among non-venomous, and two species of venomous snakes. We found adult females with emerged juvenile offspring took the most risk, harassing for longer durations and at higher intensities than other group members, suggesting that snake harassment was a maternal behaviour. Females with juvenile offspring only harassed the highest risk elapid snake but increased vigilance and inspection with increasing snake risk suggesting that the Cape ground squirrel can discriminate between different types of snake predators. [ABSTRACT FROM AUTHOR]

The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non-human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale-multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non-functional by-product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free-ranging male rhesus macaques ( Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower-ranking males mated less and tended to masturbate more frequently than higher-ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys ( Procolobus badius) and Cape ground squirrels ( Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species. [ABSTRACT FROM AUTHOR]

Associations among organisms are thought to form because the benefits, such as increased foraging efficiency or decreased risk of predation, outweigh any costs, such as resource competition. Though many interspecific associations have been described for closely related mammals, few studies have examined the associations between mammals in different orders. The yellow mongoose ( Cynictus pencillata), a carnivore, and the Cape ground squirrel ( Xerus inauris), a rodent, co-occur in arid and semi-arid South Africa where they share sleeping burrows, predators, a similar body size, and the capability to emit alarm calls in response to predators. To investigate enhanced predator avoidance as a potential benefit explaining the persistence of this association, we assessed individual mongoose vigilance alone and with squirrels or other mongooses, and with varying interspecific group size, using field observations. We also tested for responses to conspecific and heterospecific alarm calls in both study species using playback experiments. The proportion of time mongoose individuals spent vigilant decreased in the presence of squirrels or other mongooses and was negatively correlated with interspecific group size; a similar pattern was previously shown for conspecific groups of Cape ground squirrels. These results are predicted by both the dilution and collective detection hypotheses. In addition, hetero- and conspecific alarm calls elicited vigilance responses in both species. These results suggest that both species can benefit from the collective detection and dilution arising from their interspecific association and that this interspecific association could be mutualistic. [ABSTRACT FROM AUTHOR]

Small mammals have a number of means to detect and avoid predators, including visual, auditory and olfactory cues. Olfactory cues are particularly important for nocturnal or fossorial species where visual cues would not be as reliable. The Cape ground squirrel ( Xerus inauris) is a semi-fossorial, diurnal mammal from southern Africa. Cape ground squirrels encounter multiple species of predatory snake that pursue individuals underground where visual and social cues are limited. We assessed whether Cape ground squirrels use odours to discriminate between snakes by presenting a non-venomous snake, a venomous snake and a control odour collected on polyethylene cubes to 11 adult female squirrels from 11 different social groups. Cape ground squirrels responded by inspecting the cube, displaying snake harassment-associated behaviours and decreasing time spent in close proximity to snake odours when compared with a control. They also displayed discrimination between two snake species by increasing the frequency of cube inspection and increasing harassment behaviours with venomous snake odours when compared with non-venomous snake odours. We conclude that Cape ground squirrels respond with snake-specific antipredator behaviours when presented olfactory cues alone. Olfactory discrimination may be maintained by the decreased utility of other methods of predator detection: sight and group detection, in below-ground encounters. [ABSTRACT FROM AUTHOR]

Urbanisation critically threatens biodiversity because of habitat destruction and novel selection pressures. Some animals can respond to these challenges by modifying their behaviour, particularly anti-predator behaviour, allowing them to persist in heavily transformed urban areas. We investigated whether the anti-predator behaviour of the Cape ground squirrel Xerus inauris differed in three localities that differed in their level of urbanisation. According to the habituation hypothesis, we predicted that ground squirrels in urban areas would: (a) be less vigilant and forage more; (b) trade-off flight/vigilance in favour of foraging; and (c) have shorter flight initiation distances (FID) when approached by a human observer. Observations were made in winter and summer at each locality. As expected, ground squirrels in urbanised areas were less vigilant and had shorter FIDs but did not trade-off between foraging and vigilance. In contrast, a population in a non-urbanised locality showed greater levels of vigilance, FID and traded-off vigilance and foraging. A population in a peri-urban locality showed mixed responses. Our results indicate that Cape ground squirrels reduce their anti-predator behaviour in urban areas and demonstrate a flexible behavioural response to urbanisation. [ABSTRACT FROM AUTHOR]

Abstract: Many mammalian species that interact with venomous snakes show resistances to venoms. The family Sciuridae has several North American members that harass venomous snakes and show proteolytic resistances in their sera. We examined sera collected from an African ground squirrel (Xerus inauris) against two sympatric venomous snakes (Bitis arietans and Naja annulifera) and found no support for proteolytic resistance. Our results add to our understanding of the risks in predator defense within the family Sciuridae. [Copyright &y& Elsevier]

Organisms respond to cyclical environmental conditions by entraining their endogenous biological rhythms. Such physiological responses are expected to be substantial for species inhabiting arid environments which incur large variations in daily and seasonal ambient temperature (Ta). We measured core body temperature (Tb) daily rhythms of Cape ground squirrels Xerus inauris inhabiting an area of Kalahari grassland for six months from the Austral winter through to the summer. Squirrels inhabited two different areas: an exposed flood plain and a nearby wooded, shady area, and occurred in different social group sizes, defined by the number of individuals that shared a sleeping burrow. Of a suite of environmental variables measured, maximal daily Ta provided the greatest explanatory power for mean Tb whereas sunrise had greatest power for Tb acrophase. There were significant changes in mean Tb and Tb acrophase over time with mean Tb increasing and Tb acrophase becoming earlier as the season progressed. Squirrels also emerged from their burrows earlier and returned to them later over the measurement period. Greater increases in Tb, sometimes in excess of 5°C, were noted during the first hour post emergence, after which Tb remained relatively constant. This is consistent with observations that squirrels entered their burrows during the day to 'offload' heat. In addition, greater Tb amplitude values were noted in individuals inhabiting the flood plain compared with the woodland suggesting that squirrels dealt with increased environmental variability by attempting to reduce their Ta-Tb gradient. Finally, there were significant effects of age and group size on Tb with a lower and less variable Tb in younger individuals and those from larger group sizes. These daTa indicate that Cape ground squirrels have a labile Tb which is sensitive to a number of abiotic and biotic factors and which enables them to be active in a harsh and variable environment. [ABSTRACT FROM AUTHOR]

Parasites can be detrimental to the health, longevity, and reproduction of their hosts, but these costs are rarely quantified in nature. We removed ectoparasites and endoparasites from Cape ground squirrels (Xerus inauris), a highly social sciurid in southern Africa. Parasites were removed for 3 months during the dry winter season, when fewer resources are available and the impact of parasites may be greatest. We examined changes in female body mass, reproduction, grooming, and burrow use. Female body mass did not increase with parasite removal, but reproductive success (number of offspring raised to emergence) was nearly 4 times higher for treated females. Rates of allogrooming were lower for treated females, but we were unable to detect a significant change in burrow movements, perhaps because factors other than parasites (e.g., predator avoidance) affect such movements. Gestation and lactation are the most physiologically stressful processes that females undergo, and the dramatic increase in reproductive success in treated females suggests that parasites drain resources that would otherwise be allocated to reproduction. Our results suggest that nonparasitized females put the extra energy into reproduction rather than into their own body weight, which appears to enhance juvenile survival. [ABSTRACT FROM PUBLISHER]

How individuals balance time spent satisfying nutritional needs and time spent being vigilant to protect against potential predation has received abundant attention from researchers. Evidence indicates that both social conditions and predator risk affect how individuals perceive environmental threat, however, the relative influence of each type of risk remains unclear. The risk allocation hypothesis considers how individuals respond to predation risk over time by adapting their investment in high-quality or low-quality vigilance. Here we use the risk allocation hypothesis as a guide to examine how different risk factors influence vigilance quantity and quality in Cape ground squirrels, Xerus inauris. We tested how the social conditions of age, sex, distance to a safe refuge, distance from a nearest neighbour and predator risk affect the amount of time (quantity) individuals spend vigilant. Individuals were more vigilant in areas with more potential predators and when they were further from a safe refuge or nearest neighbour. We then tested whether these risk factors that affected vigilance quantity also affected vigilance quality by measuring exclusive vigilance (high-cost, high-quality) and shared-foraging–vigilance (low-cost, low-quality). Individuals in high-predation risk areas invested more time in high-cost vigilance behaviour than in low-cost vigilance/foraging behaviour compared with individuals in low-predation risk areas. Since squirrels invested in high-cost vigilance significantly more than in low-cost vigilance regardless of distance to a refuge or other squirrels, we suggest that combined foraging with vigilance compromises vigilance to lower its quality. [Copyright &y& Elsevier]

The suitability of a habitat to an animal includes food availability, physical and climatic factors, population interactions, and safety from predators. Mappings of vegetation, soils, and microclimates across ecological landscapes have become standard and important tools for assessing an animal's habitat. More elusive to the researcher, yet of equal importance to the animal, has been the ability to map the predation risk perceived by an animal. Laundré et al., in developing the concept, defined the landscape of fear as the spatial map of the animal's predation cost of foraging. We mapped this landscape of predation costs by measuring the use of depletable food patches (yielding giving up densities [GUDs]) arranged as a grid across the landscape of interest. The landscapes of fear for 3 colonies of Cape ground squirrels (Xerus inauris) in Augrabies Falls National Park, South Africa, revealed large and distinct spatial variation in predation costs that appeared to be governed primarily by proximity to burrows and open sight lines. By converting the GUDs into quitting harvest rates (joules per minute), we believe we have translated the animals' perceptions of risk into a physical map whose contours across the landscape represent lines of equal foraging costs. Among the 3 colonies only 3-22% of the space resulted in low foraging costs (<2,500 J/min), whereas 31-92% of the sampled areas represented very high foraging costs (>5,000 J/min). [ABSTRACT FROM AUTHOR]

Mixed-species associations have been described in many vertebrate species, but few behavioral studies have investigated associations between species from different mammalian orders. Cape ground squirrels ( Xerus inauris) are highly social rodents that inhabit burrows with two species of mongoose, but the benefits of these interspecific associations to ground squirrels remain unresolved. We compared the behavior of squirrels while solitary, with conspecifics, and in the presence of suricates ( Suricata suricatta) and yellow mongooses ( Cynictis pencillatus). Squirrels spent less time alert and more time feeding when suricates were present, but increased vigilance in the presence of yellow mongooses. In a series of mobbing trials with a puff adder ( Bitis arietans), a common predator of all three species, Cape ground squirrels were the most active in mobbing the snake. Our results suggest that Cape ground squirrels benefit from associating with suricates, but not necessarily with yellow mongooses. Both mongoose species benefit from the burrowing activities of the squirrels for thermoregulation and escape from predators, and a suite of other organisms may similarly benefit from the habitat modifications by Cape ground squirrels, suggesting they could be considered ecosystem engineers of the arid and semi-arid regions of southern Africa. Thus, the association between Cape ground squirrels and suricates appears mutually beneficial, whereas yellow mongooses may merely be commensals of the squirrels. [ABSTRACT FROM AUTHOR]

The optimal dose of medetomidine-ketamine-buprenorphine was determined in 25 Cape ground squirrels (Xerus inauris) undergoing surgical implantation of a temperature logger into the abdominal cavity. At the end of anaesthesia, the squirrels were given atipamezole intramuscularly to reverse the effects of medetomidine. The mean dose of medetomidine was 67.6 ± 9.2μg/kg,ketamine13.6 ± 1.9mg/kgandbuprenorphine 0.5 ± 0.06μg/kg.Induction time was 3.1 ± 1.4 mm. This produced surgical anaesthesia for 21± 4.2 mm. Atipamezole 232 ± 92μg/kg produced a rapid recovery. Squirrels were sternally recumbent in 3.5 ± 2.2 min. [ABSTRACT FROM AUTHOR]

The immunocompetence handicap hypothesis (ICHH) proposes that testosterone has both beneficial effects on male reproductive potential and negative effects by suppressing the immune system. However, support for the ICHH has been variable and an alternative hypothesis suggests that testosterone may be acting indirectly via cortisol to suppress immunity (the stress-linked ICHH). A third hypothesis is that increased energetic investment in immunity results in the suppression of testosterone. We tested these hypotheses in male Cape ground squirrels ( Xerus inauris ) through two separate manipulations: first, by triggering a strong immune response using a lipopolysaccharide (LPS) injection and, secondly, by increasing circulating testosterone using silastic testosterone implants. Responding to an immune challenge significantly reduced testosterone, supporting the immune suppression hypothesis, while increasing circulating testosterone had no effect on immunocompetence, body mass, ectoparasite abundances or cortisol levels, failing to support either the ICHH or stress-linked ICHH. Our results add to the increasing body of literature that challenges the ICHH, and we conclude that the trade-off between testosterone and immunity is mediated through immune activation and not through testosterone in male Cape ground squirrels. Being able to test the ICHH, stress-linked ICHH and immune suppression hypotheses in a free-ranging mammal gives us a unique opportunity to examine the mechanisms mediating this trade-off., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)