Cheetahs, Acinonyx jubatus, balance turn capacity with pace when chasing prey.

Predator-prey interactions are fundamental in the evolution and structure of ecological communities. Our understanding, however, of the strategies used in pursuit and evasion remains limited. Here, we report on the hunting dynamics of the world's fastest land animal, the cheetah, Acinonyx jubatus. Using miniaturized data loggers, we recorded fine-scale movement, speed and acceleration of free-ranging cheetahs to measure how hunting dynamics relate to chasing different sized prey. Cheetahs attained hunting speeds of up to 18.94 m s(-1) and accelerated up to 7.5 m s(-2) with greatest angular velocities achieved during the terminal phase of the hunt. The interplay between forward and lateral acceleration during chases showed that the total forces involved in speed changes and turning were approximately constant over time but varied with prey type. Thus, rather than a simple maximum speed chase, cheetahs first accelerate to decrease the distance to their prey, before reducing speed 5-8 s from the end of the hunt, so as to facilitate rapid turns to match prey escape tactics, varying the precise strategy according to prey species. Predator and prey thus pit a fine balance of speed against manoeuvring capability in a race for survival.

Testosterone levels in dominant sociable males are lower than in solitary roamers: physiological differences between three male reproductive tactics in a sociably flexible mammal.

The relative plasticity hypothesis predicts that alternative tactics are associated with changes in steroid hormone levels. In species with alternative male reproductive tactics, the highest androgen levels have usually been reported in dominant males. However, in sociable species, dominant males show amicable behaviors to gain access to females, which might conflict with high testosterone levels. We compared testosterone, corticosterone, and resting metabolic rate in male striped mice (Rhabdomys pumilio) following a conditional strategy with three different reproductive tactics: (i) philopatric group-living males, (ii) solitary-living roamers, (iii) dominant but sociable group-living territorial breeders. Philopatrics had the lowest testosterone but highest corticosterone levels, suggesting that they make the best of a bad job. Dominant territorial breeders had lower testosterone levels than roamers, which have a lower competitive status. Roamers had the highest testosterone levels, which might promote risky behavior, such as invading territories defended by territorial males. Roamers also had lower resting metabolic rates than either type of group-living males. Our results suggest that dominant males' testosterone levels reflect a trade-off between low testosterone amicable behavior and high testosterone dominance behavior.

Osmoregulatory traits of broad-toothed field mouse (Apodemus mystacinus) populations from different habitats.

One mechanism for physiological adjustment of small mammals to different habitats and different seasons is by seasonal acclimatization of their osmoregulatory system. We examined the abilities of broad-toothed field mice (Apodemus mystacinus) from different ecosystems ('sub-alpine' and 'Mediterranean') to cope with salinity stress under short day (SD) and long day (LD) photoperiod regimes. We compared urine volume, osmolarity, urea and electrolyte (sodium, potassium and chloride) concentrations. Significant differences were noted in the abilities of mice from the two ecosystems to deal with salinity load; in particular sub-alpine mice produced less concentrated urine than Mediterranean mice with SD- sub-alpine mice seeming to produce particularly dilute urine. Urea concentration generally decreased with increasing salinity, whereas sodium and potassium levels increased, however SD- sub-alpine mice behaved differently and appeared not to be able to excrete electrolytes as effectively as the other groups of mice. Differences observed provide an insight into the kinds of variability that are present within populations inhabiting different ecosystems, thus how populations may be able to respond to potential changes in their environment. Physiological data pertaining to adaptation to increased xeric conditions, as modelled by A. mystacinus, provides valuable information as to how other species may cope with potential climatic challenges.

Interspecific visitation of cattle and badgers to fomites: A transmission risk for bovine tuberculosis?

In Great Britain and Ireland, badgers (Meles meles) are a wildlife reservoir of Mycobacterium bovis and implicated in bovine tuberculosis transmission to domestic cattle. The route of disease transmission is unknown with direct, so-called "nose-to-nose," contact between hosts being extremely rare. Camera traps were deployed for 64,464 hr on 34 farms to quantify cattle and badger visitation rates in space and time at six farm locations. Badger presence never coincided with cattle presence at the same time, with badger and cattle detection at the same location but at different times being negatively correlated. Badgers were never recorded within farmyards during the present study. Badgers utilized cattle water troughs in fields, but detections were infrequent (equivalent to one badger observed drinking every 87 days). Cattle presence at badger-associated locations, for example, setts and latrines, were three times more frequent than badger presence at cattle-associated locations, for example, water troughs. Preventing cattle access to badger setts and latrines and restricting badger access to cattle water troughs may potentially reduce interspecific bTB transmission through reduced indirect contact.

The energetics of huddling in two species of mole-rat (Rodentia: Bathyergidae).

Small rodents with a large surface-area-to-volume ratio and a high thermal conductance are likely to experience conditions where they have to expend large amounts of energy in order to maintain a constant body temperature at low ambient temperatures. The survival of small rodents is thus dependent on their ability to reduce heat loss and increase heat production at low ambient temperatures. Two such animals are the social subterranean rodents Cryptomys damarensis (the Damaraland mole-rat) and Cryptomys hottentotus natalensis (the Natal mole-rat). This study examined the energy savings associated with huddling as a behavioural thermoregulatory mechanism to conserve energy in both these species. Individual oxygen consumption (VO(2)) was measured in groups ranging in size from one to 15 huddling animals for both species at ambient temperatures of 14, 18, 22, 26 and 30 degrees C. Savings in energy (VO(2)) were then compared between the two species. Significant differences in VO(2) (p<0.05) were found within each species, indicating that both Damaraland mole-rats and Natal mole-rats saved more energy in larger as opposed to smaller groups. VO(2) was also different between the two species, with Damaraland mole-rats showing a higher decrease in VO(2) with increasing group size compared to Natal mole-rats. These findings suggest that huddling confers significant energy savings in both species and that the amount of energy saved is related to each species' ecology. More generally, these findings suggest that group living desert-adapted species are likely to be more prone to heat loss at low ambient temperatures than temperate-adapted species, especially at low group sizes. This is presumably offset against the advantages obtained by having a low metabolic rate and avoiding hyperthermia when temperatures are hot.

Identification of animal movement patterns using tri-axial magnetometry.

BACKGROUND: Accelerometers are powerful sensors in many bio-logging devices, and are increasingly allowing researchers to investigate the performance, behaviour, energy expenditure and even state, of free-living animals. Another sensor commonly used in animal-attached loggers is the magnetometer, which has been primarily used in dead-reckoning or inertial measurement tags, but little outside that. We examine the potential of magnetometers for helping elucidate the behaviour of animals in a manner analogous to, but very different from, accelerometers. The particular responses of magnetometers to movement means that there are instances when they can resolve behaviours that are not easily perceived using accelerometers. METHODS: We calibrated the tri-axial magnetometer to rotations in each axis of movement and constructed 3-dimensional plots to inspect these stylised movements. Using the tri-axial data of Daily Diary tags, attached to individuals of number of animal species as they perform different behaviours, we used these 3-d plots to develop a framework with which tri-axial magnetometry data can be examined and introduce metrics that should help quantify movement and behaviour.. RESULTS: Tri-axial magnetometry data reveal patterns in movement at various scales of rotation that are not always evident in acceleration data. Some of these patterns may be obscure until visualised in 3D space as tri-axial spherical plots (m-spheres). A tag-fitted animal that rotates in heading while adopting a constant body attitude produces a ring of data around the pole of the m-sphere that we define as its Normal Operational Plane (NOP). Data that do not lie on this ring are created by postural rotations of the animal as it pitches and/or rolls. Consequently, stereotyped behaviours appear as specific trajectories on the sphere (m-prints), reflecting conserved sequences of postural changes (and/or angular velocities), which result from the precise relationship between body attitude and heading. This novel approach shows promise for helping researchers to identify and quantify behaviours in terms of animal body posture, including heading. CONCLUSION: Magnetometer-based techniques and metrics can enhance our capacity to identify and examine animal behaviour, either as a technique used alone, or one that is complementary to tri-axial accelerometry.

Mole-rats from higher altitudes have greater thermoregulatory capabilities.

Subterranean mammals (those that live and forage underground) inhabit a challenging microenvironment, with high levels of carbon dioxide and low levels of oxygen. Consequently, they have evolved specialised morphological and physiological adaptations. For small mammals that inhabit high altitudes, the effects of cold are compounded by low oxygen partial pressures. Hence, subterranean mammals living at high altitudes are faced with a uniquely demanding physiological environment, which presumably necessitates additional physiological adjustments. We examined the thermoregulatory capabilities of two populations of Lesotho mole-rat Cryptomys hottentotus mahali that inhabit a 'low' (1600 m) and a 'high' (3200 m) altitude. Mole-rats from the high altitude had a lower temperature of the lower critical point, a broader thermoneutral zone, a lower thermal conductance and greater regulatory non-shivering thermogenesis than animals from the lower altitude. However, minimum resting metabolic rate values were not significantly different between the populations and were low compared with allometric predictions. We suggest that thermoregulatory costs may in part be met by animals maintaining a low resting metabolic rate. High-altitude animals may adjust to their cooler, more oxygen-deficient environment by having an increased non-shivering thermogenesis whilst maintaining low thermal conductance.

Optimal body size and energy expenditure during winter: why are voles smaller in declining populations?

Winter is energetically challenging for small herbivores because of greater energy requirements for thermogenesis at a time when little energy is available. We formulated a model predicting optimal wintering body size, accounting for the scaling of both energy expenditure and assimilation to body size, and the trade-off between survival benefits of a large size and avoiding survival costs of foraging. The model predicts that if the energy cost of maintaining a given body mass differs between environments, animals should be smaller in the more demanding environments, and there should be a negative correlation between body mass and daily energy expenditure (DEE) across environments. In contrast, if animals adjust their energy intake according to variation in survival costs of foraging, there should be a positive correlation between body mass and DEE. Decreasing temperature always increases equilibrium DEE, but optimal body mass may either increase or decrease in colder climates depending on the exact effects of temperature on mass-specific survival and energy demands. Measuring DEE with doubly labeled water on wintering Microtus agrestis at four field sites, we found that DEE was highest at the sites where voles were smallest despite a positive correlation between DEE and body mass within sites. This suggests that variation in wintering body mass between sites was due to variation in food quality/availability and not adjustments in foraging activity to varying risks of predation.

Effects of parasitism and morphology on squirrelpox virus seroprevalence in grey squirrels (Sciurus carolinensis).

Invasive species have been cited as major causes of population extinctions in several animal and plant classes worldwide. The North American grey squirrel (Sciurus carolinensis) has a major detrimental effect on native red squirrel (Sciurus vulgaris) populations across Britain and Ireland, in part because it can be a reservoir host for the deadly squirrelpox virus (SQPV). Whilst various researchers have investigated the epizootiology of SQPV disease in grey squirrels and have modelled the consequent effects on red squirrel populations, less work has examined morphological and physiological characteristics that might make individual grey squirrels more susceptible to contracting SQPV. The current study investigated the putative relationships between morphology, parasitism, and SQPV exposure in grey squirrels. We found geographical, sex, and morphological differences in SQPV seroprevalence. In particular, larger animals, those with wide zygomatic arch widths (ZAW), males with large testes, and individuals with concurrent nematode and/or coccidial infections had an increased seroprevalence of SQPV. In addition, males with larger spleens, particularly those with narrow ZAW, were more likely to be exposed to SQPV. Overall these results show that there is variation in SQPV seroprevalence in grey squirrels and that, consequently, certain individual, or populations of, grey squirrels might be more responsible for transmitting SQPV to native red squirrel populations.

Energetic benefits of sociality offset the costs of parasitism in a cooperative mammal.

Sociality and particularly advanced forms of sociality such as cooperative breeding (living in permanent groups with reproductive division of labour) is relatively rare among vertebrates. A suggested constraint on the evolution of sociality is the elevated transmission rate of parasites between group members. Despite such apparent costs, sociality has evolved independently in a number of vertebrate taxa including humans. However, how the costs of parasitism are overcome in such cases remains uncertain. We evaluated the potential role of parasites in the evolution of sociality in a member of the African mole-rats, the only mammal family that exhibits the entire range of social systems from solitary to eusocial. Here we show that resting metabolic rates decrease whilst daily energy expenditure and energy stores (i.e. body fat) increase with group size in social Natal mole rats (Cryptomys hottentotus natalensis). Critically, larger groups also had reduced parasite abundance and infested individuals only showed measurable increases in energy metabolism at high parasite abundance. Thus, in some circumstances, sociality appears to provide energetic benefits that may be diverted into parasite defence. This mechanism is likely to be self-reinforcing and an important factor in the evolution of sociality.

Environmental challenges and physiological solutions: comparative energetic daily rhythms of field mice populations from different ecosystems.

Daily and seasonal variations in physiological characteristics of mammals can be considered adaptations to temporal habitat variables. Across different ecosystems, physiological adjustments are expected to be sensitive to different environmental signals such as changes in photoperiod, temperature or water and food availability; the relative importance of a particular signal being dependent on the ecosystem in question. Energy intake, oxygen consumption (VO(2)) and body temperature (T(b)) daily rhythms were compared between two populations of the broad-toothed field mouse Apodemus mystacinus, one from a Mediterranean and another from a sub-Alpine ecosystem. Mice were acclimated to short-day (SD) 'winter' and long-day (LD) 'summer' photoperiods under different levels of salinity simulating osmotic challenges. Mediterranean mice had higher VO(2) values than sub-Alpine mice. In addition, mice exposed to short days had higher VO(2) values when given water with a high salinity compared with mice exposed to long days. By comparison, across both populations, increasing salinity resulted in a decreased T(b) in SD- but not in LD-mice. Thus, SD-mice may conserve energy by decreasing T(b) during ('winter') conditions which are expected to be cool, whereas LD-mice might do the opposite and maintain a higher T(b) during ('summer') conditions which are expected to be warm. LD-mice behaved to reduce energy expenditure, which might be considered a useful trait during 'summer' conditions. Overall, increasing salinity was a clear signal for Mediterranean-mice with resultant effects on VO(2) and T(b) daily rhythms but had less of an effect on sub-Alpine mice, which were more responsive to changes in photoperiod. Results provide an insight into how different populations respond physiologically to various environmental challenges.

Seasonal patterns of body temperature daily rhythms in group-living Cape ground squirrels Xerus inauris.

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 (T(a)). We measured core body temperature (T(b)) 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 T(a) provided the greatest explanatory power for mean T(b) whereas sunrise had greatest power for T(b) acrophase. There were significant changes in mean T(b) and T(b) acrophase over time with mean T(b) increasing and T(b) 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 T(b), sometimes in excess of 5°C, were noted during the first hour post emergence, after which T(b) remained relatively constant. This is consistent with observations that squirrels entered their burrows during the day to 'offload' heat. In addition, greater T(b) 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 T(a)-T(b) gradient. Finally, there were significant effects of age and group size on T(b) with a lower and less variable T(b) in younger individuals and those from larger group sizes. These data indicate that Cape ground squirrels have a labile T(b) which is sensitive to a number of abiotic and biotic factors and which enables them to be active in a harsh and variable environment.

The effects of season and dietary salt content on body temperature daily rhythms of common spiny mice from different micro-habitats.

We compared body temperature (T(b)) daily rhythms in two populations of common spiny mice, Acomys cahirinus, during summer and winter months in relation to increasing dietary salt content. Mice were collected from the North and South facing slopes (NFS and SFS) of the same valley, that are exhibiting mesic and xeric habitats, respectively. During the summer, whilst mice were offered a water source containing 0.9% NaCl, SFS individuals had T(b) peak values at 24:00, whereas NFS individuals had peak values at 18:00. When the salinity of the water source was increased, from 0.9 to 2.5% and then 3.5%, the difference between maximal and minimal T(b) of both populations increased. In addition, with increased salinity, the T(b) daily peak of SFS mice shifted to 18:00. During the winter, the mean daily T(b) values of both populations of mice were lower than during the summer. At 0.9% salinity, the NFS mice exhibited a daily T(b) variation with a peak at the beginning of the night. However, we did not detect any significant variation in daily T(b) in the SFS mice. At 2.5% salinity, the difference between the mean daily T(b) of mice from the two slopes increased. In winter we were unable to increase the salinity to 3.5% as the animals began to lose weight rapidly. We suggest that common spiny mice that inhabit these two micro-habitats are forming two discrete populations that respond differently to the environmental pressures prevailing in each habitat, by evolving different physiological capacities.

Comparative non-shivering thermogenesis in adjacent populations of the common spiny mouse (Acomys cahirinus) from opposite slopes: the effects of increasing salinity.

We compared non-shivering thermogenesis between two adjacent populations of the common spiny mouse Acomys cahirinus from different habitats, in relation to increasing salinity. Individuals were captured from the north- and south-facing slopes of the same valley, that represent "Mediterranean" and "desert" habitats, respectively. We hypothesized that the two populations of mice would differ in their thermoregulatory capacities, reflecting their need to cope with the environmental stress in each habitat. We measured resting metabolic rate by recording oxygen consumption, body temperature and response to an injection of exogenous noradrenaline. Mice were maintained on diets with increasing levels of salt intake to examine their abilities to cope with increasing osmotic stress. Mice from north-facing slopes generally had a higher resting metabolic rate and a higher increase in oxygen consumption in response to noradrenaline than mice from south-facing slopes. Increasing salinity decreased resting metabolic rate values, body temperature, and oxygen consumption in response to noradrenaline in both populations, and diminished slope-dependant differences. We suggest that these differences could be a result of an ongoing adaptive process to different climatic conditions, typical of the Mediterranean region, that are a demonstrable example of evolution in action.

Differential energy costs of winter acclimatized common spiny mice Acomys cahirinus from two adjacent habitats.

The common spiny mouse Acomys cahirinus, of Ethiopian origin, has a widespread distribution across arid, semi-arid and Mediterranean parts of the Arabian sub-region. We compared the daily energy expenditure (DEE), water turnover (WTO) and sustained metabolic scope (SusMS=DEE/resting metabolic rate) of two adjacent populations during the winter. Mice were captured from North- and South- facing slopes (NFS and SFS) of the same valley, comprising mesic and xeric habitats, respectively. Both DEE and SusMS winter values were greater in NFS than SFS mice and were significantly greater than values previously measured in the summer for these two populations in the same environments. However, WTO values were consistent with previously established values and were not significantly different from allometric predictions for desert eutherians. We suggest that physiological plasticity in energy expenditure, which exists both temporally and spatially, combined with stable WTO, perhaps reflecting a xeric ancestry, has enabled A. cahirinus to invade a wide range of habitats.

Shelters from the storm : A note on the geography of hurricane shelters in Barbados, 1982

Barbados, a small island of 166 square miles in the Caribbean, with a population of 246,416 persons, has a total of 177 emergency shelters with a known capacity of 20,623 persons. The average shelter capacity is 117 persons and the total known shelter capacity represents 8.4

of the population. The spatial arrangement of the grade I shelters, as seen relative to the 1980 population census map by grouped enumeration districts, reveals that there are many areas and persons, who, in time of emergency, will not be able to avail themselves to the protection of a shelter (AU)

A geo-spatial analysis of health care in Barbados (1982) - abstract

In Barbados, the overall picture of health care is quite bright, with a population per medical practioner of 1,100 and a population per hospital bed of 400. However, an analysis of the location of the medical facilities and practitioners reveals that there is much disparity in the availability of health care. Places like St. Lucy and St. Joseph as well as parts of St. Philip are at a marked disadvantage, having no medical practioner in residence, and are somewhat removed from the nearest available medical service. This was confirmed, using three established tecniques in spatial analysis (AU)

Clustering of cases of mycobacterium fortuitum infection investigated by molecular typing

Organisms of the Mycobacterium fortuitum complex are recognized, but uncommon, causes of pulmonary disease, primary cutaneous disease and a wide spectrum of nosocomial infections. M.fortuitum was isolated from 20 patients over a 15-month period, with an apparent clustering of isolates of M.fortuitum occurring from January to March 1994. The molecular epidemiology of this clustering was investigated using an arbitrary primer-polymerase chain reaction method (AP-PCR). Twenty-two isolates were studied and yielded 14 distinct profiles. Multiple isolates from a single patient yielded identical profiles. All of seven isolates of M.fortuitum recovered during the six-weeks period from January to March 1994 shared a common profile which was distinct from all other isolates, suggesting that a single strain was located from specimens from all seven patients. The source of the cluster of isolates of M.fortuitum is uncertain. We can find no epidemiological link upon which to suppose an episode of cross-infection within the hospital environment. Therefore it seems likely that contamination of the specimens during collection, transport or processing was responsible for the "pseudo-outbreak" of M.fortuitum observed in this study (AU)

The medical geography of clinical leptospirosis in Barbados 1976 to 1982

This study examines the inter-relationship of the factors: host, agent and human activity in producing clinical leptospirosis in Barbados from 1976 through 1982. These inter-relationships are examined at 2 levels: the macro (parish) and the micro (district) levels. At the macro level the factors of rainfall, drainage and involvement in agriculture were found to have significant associations with the average morbidity pattern. When plotted relative to rainfall, 71.8 percent of the cases occurred in locations and months of above average rainfall. When plotted relative to drainage, 91.3 percent of the cases occurred in areas below 250 ft., where clay infilling in watercourses produced flood-prone environments, or in areas above 250 ft. which were within 220 yd. of watercourses. The net result is that rainfall and drainage combined accounted for 98.5 percent of cases at this level. The Rainfall-Agricultural Involvement multiple regression model explained 60 percent of the variation in parish morbidity over the time period. These factors, however, did not adequately explain micro-level patterns of morbidity. To understand these, human activity was examined. This analysis utilized an adaptation of 2 methodologies - the 24 hr. Recall Technique and Water Contact Studies. These were used to determine exposure to the physical environment, and its relation to the pattern of morbidity. For this examination 2 areas were studied - St. Philip South-West, a high morbidity area with more cases than could be explained by the moisture factor alone, and St. James East, with fewer. Exposure to the physical environment was found to vary according to location, sex and the pattern of human activity. These all had strong associations with morbidity. The micro-level study revealed that there are 2 distinct spheres of exposure - the home and the work environments - and there tends to be little overlap in these 2 spheres. The study also revealed that there was a spatial variation in the nature of contact with the environment which may be an important consideration in explaining the micro-level pattern of morbidity. (AU)