Some like it cold: summer torpor by freetail bats in the Australian arid zone

Bats are among the most successful groups of Australian arid-zone mammals and, therefore, must cope with pronounced seasonal fluctuations in ambient temperature (T _a), food availability and unpredictable weather patterns. As knowledge about the energy conserving strategies in desert bats is scant, we used temperature-telemetry to quantify the thermal physiology of tree-roosting inland freetail bats (Mormopterus species 3, 8.5 g, n = 8) at Sturt National Park over two summers (2010–2012), when T _a was high and insects were relatively abundant. Torpor use and activity were affected by T _a. Bats remained normothermic on the warmest days; they employed one “morning” torpor bout on most days and typically exhibited two torpor bouts on the coolest days. Overall, animals employed torpor on 67.9 % of bat-days and torpor bout duration ranged from 0.5 to 39.3 h. At any given T _a, torpor bouts were longer in Mormopterus than in bats from temperate and subtropical habitats. Furthermore, unlike bats from other climatic regions that used only partial passive rewarming, Mormopterus aroused from torpor using either almost entirely passive (68.9 % of all arousals) or active rewarming (31.1 %). We provide the first quantitative data on torpor in a free-ranging arid-zone molossid during summer. They demonstrate that this desert bat uses torpor extensively in summer and often rewarms passively from torpor to maximise energy and water conservation.     

Relative impacts of cattle grazing and feral animals on an Australian arid zone reptile and small mammal assemblage

The effect of different levels of cattle grazing on an arid Australian small terrestrial mammal and lizard assemblage was assessed in a long‐tem series of cross‐fence comparisons. Cross‐fenced sites were closely matched for edaphic and vegetation characteristics and experienced near identical weather patterns, to ensure that cattle grazing pressure was the principal determinant of any differences in fauna assemblages. In addition, the effects of removal of cattle, cats, foxes and rabbits from three of these long‐term monitoring sites were assessed to determine the relative impacts of cattle grazing and feral animals. Small mammal captures, with the exception of Mus musculus, revealed a significant negative response to cattle grazing pressure but this response was of a considerably lower magnitude than the dramatic increase in rodent captures and species richness within the feral animal‐proof Arid Recovery Reserve. Higher kangaroo numbers in ungrazed controls, compared with treatments grazed by cattle, possibly negated the benefits to small mammals of removing cattle grazing. No reptile species responded significantly to the grazing treatments although reptile richness and captures of geckos and skinks were the lowest and agamid captures were the highest at heavily grazed sites. Nephrurus levis was the only reptile species to increase significantly, while captures of some smaller geckoes declined, within the feral‐proof treatment. Feral predation exerted a more significant effect on most small mammal species than the levels of cattle grazing assessed in this study, yet reptile responses to grazing or feral animals were less apparent and were likely primarily driven by changes in vegetation cover or secondary trophic impacts.     

Rabbits and the failure of regeneration in Australian arid zone Acacia

Three experiments are reported concerning the effect of rabbit grazing (Oryctolagus cuniculus L.) upon the recruitment of Acacia seedlings to populations in the South Australian arid zone. In western myall woodland (Acacia papyrocaqsa Benth.) under prevailing rabbit and sheep densities, seedlings exposed to grazing by these two herbivores or to rabbits alone were severely pruned, whereas totally protected seedlings grew unchecked. Seedlings of four Acacia species; A. papyrocarpa, A. oswaldii (F. Muell.), A. kempeana (F. Muell.) and A. burkittii (F. Muell. ex Benth.) were transplanted into four 50 m × 50 m rabbit-proof enclosures. Six rabbits were introduced into each enclosure and within 24 h half of the total seedling population had been grazed. This was at a seedling dry weight ratio of 1|150 000 of the total fodder on offer. In one of the enclosures no seedlings were eaten and there is evidence to suggest that a dense patch of grass had a buffering effect, reducing grazing pressure. Small shoots cut from old Acacia and transferred to the ground throughout 1000 ha of western myall woodland were grazed rapidly near rabbit warrens and progressively less rapidly with increased distance from warrens. The experiments demonstrated that even with the lowered post-myxomatosis population densities, rabbit grazing pressure would significantly affect recruitment in arid zone Acacia populations in the absence of stock.     

Competition between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia

Abstract Competition between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large-scale manipulative experiment incorporating two replicates of each of three treatments: sheep-only, kangaroo-only and a sheepAangaroo mixture. The study was conducted over two years during which time pasture conditions varied markedly. Competition was intermittent, occurring only during a period of climatically related food depletion (semi-drought). At this time there was a large increase in kangaroo densities due to an influx of kangaroos from neighbouring areas. Competition reduced live-weight in sheep but had no significant impact on wool production. This effect was linked to diet selection. Competition caused red kangaroos to favour paddocks destocked of sheep but had no detectable effect on the condition of kangaroos.     

Limb conditions that predispose sheep to lameness in the arid zone of Nigeria

A total of 5549 sheep were examined for indication of lameness consequent to limb conditions in the arid zone of Nigeria. Out of these, 1051 showed evidence of signs of lameness in at least one limb. A prevalence rate of 18.09% was recorded in the sheep examined. The common limb conditions that predisposed sheep to lameness were overgrown hooves, traumatic injuries, interdigital pouch inflammation, limb conformational anomalies and fracture. Hoof overgrowth ranked highest as a cause of lameness. The proportions of lameness were higher during the wet months. Sheep below 4 years of age showed higher incidence of lameness compared to those above 4 years. However, there was decreasing frequency and increasing severity of lameness with age in the sheep. More lameness cases were recorded in the forelimbs than in the hindlimbs. There was no significant difference as to which gender was more predisposed to development or manifestation of lameness. Frequency of lameness in sheep in the arid zone of Nigeria is high. It is pertinent that thorough and effective management practices and early diagnosis of lameness should be performed adequately so that these conditions can be put under control to allow for increased productivity of sheep in the arid zone of Nigeria.     

Water and energy fluxes during summer in an arid‐zone passerine bird

Endothermic animals resident in hot, arid terrestrial environments are likely to face a trade‐off between their ability to obtain water and elevated thermoregulatory water requirements. We assessed whether daily water flux (DWF) is higher on hot days, reflecting increases in evaporative cooling demands, in an arid‐zone bird that obtains its water through food intake. We obtained measurements of DWF (partitioned into water influx and efflux rates) in 71 White‐browed Sparrow‐Weavers Plocepasser mahali at a desert site and a semi‐desert site, during summer in the Kalahari Desert of southern Africa. We found no evidence that DWF varied with maximum daily air temperature (T_air, range = 27.6–39.2 °C). Instead, DWF was lower during dry periods than in the wet season at the semi‐desert site. Furthermore, birds showed deficits in water balance (water influx/water efflux) during the dry periods at both sites. Our data show that DWF is low in a non‐drinking bird that obtains its water through food, and that demands for evaporative water loss on very hot days (maximum T_air of 40–44 °C) may exceed water intake rates during hot and dry periods. Species that do not have opportunities to drink will experience strong trade‐offs between thermoregulation, hydration state and activity levels as temperatures increase.     

Bet‐hedging and germination in the Australian arid zone shrub Acacia ligulata

The diaspore of the Australian arid zone shrub Acacia ligulata is dispersed by birds and ants. To investigate the benefits of providing a dispersal structure attractive to both groups, we compared the germination response and viability of seeds eaten by birds, handled by ants or collected from trees to simulated precursors of germination: scarification, fire and rainfall were simulated. Seed germination and viability were related to the degree of preheating disturbance to the seed coat. Heating increased the germinability of seeds not scarified or eaten by birds. In the absence of heating, ingestion by birds increased germinability. Heating increased the mortality of seeds. Our results suggest that ingestion of seeds by birds may break seed dormancy and hence enable some seeds to germinate soon after dispersal. Alternatively, seeds not eaten by birds are likely to remain dormant until sufficiently scarified by soil or stimulated by fire. Consequently, in areas such as the Simpson Desert, A. ligulata may be able to use a range of seedling establishment ‘windows’ provided by monsoon rains, post‐fire environments and unseasonal winter rains, and also spread the risk of unsuccessful seedling establishment by retaining dormant seeds in the seedbank.     

Energy, water and space use by free-living red kangaroos Macropus rufus and domestic sheep Ovis aries in an Australian rangeland

We used doubly labelled water to measure field metabolic rates (FMR) and water turnover rates (WTR) in one of Australia’s largest native herbivores, the red kangaroo (Macropus rufus) and one of Australia’s dominant livestock species, the wool-breed Merino sheep, under free-living conditions in a typical Australian rangeland. Also, we used GPS technology to examine animal space use, along with the comparisons of urine concentration, diet, diet digestibility, and subsequent grazing pressures. We found smaller space-use patterns than previously reported for kangaroos, which were between 14 and 25 % those of sheep. The FMR of a 25-kg kangaroo was 30 % that of a 45-kg sheep, while WTR was 15 % and both were associated with smaller travel distances, lower salt intakes, and higher urine concentration in kangaroos than sheep. After accounting for differences in dry matter digestibility of food eaten by kangaroos (51 %) and sheep (58 %), the relative grazing pressure of a standard (mature, non-reproductive) 25-kg kangaroo was 35 % that of a 45-kg sheep. Even for animals of the same body mass (35 kg), the relative grazing pressure of the kangaroo was estimated to be only 44 % that of the sheep. After accounting for the energetic costs of wool growth by sheep, the FMRs of our sheep and kangaroos were 2–3 times their expected BMRs, which is typical for mammalian FMR:BMRs generally. Notably, data collected from our free-living animals were practically identical to those from animals confined to a semi-natural enclosure (collected in an earlier study under comparable environmental conditions), supporting the idea that FMRs are relatively constrained within species.     

Multiple genomic signatures of selection in goats and sheep indigenous to a hot arid environment

Goats and sheep are versatile domesticates that have been integrated into diverse environments and production systems. Natural and artificial selection have shaped the variation in the two species, but natural selection has played the major role among indigenous flocks. To investigate signals of natural selection, we analyzed genotype data generated using the caprine and ovine 50K SNP BeadChips from Barki goats and sheep that are indigenous to a hot arid environment in Egypt''s Coastal Zone of the Western Desert. We identify several candidate regions under selection that spanned 119 genes. A majority of the genes were involved in multiple signaling and signal transduction pathways in a wide variety of cellular and biochemical processes. In particular, selection signatures spanning several genes that directly or indirectly influenced traits for adaptation to hot arid environments, such as thermo-tolerance (melanogenesis) (FGF2, GNAI3, PLCB1), body size and development (BMP2, BMP4, GJA3, GJB2), energy and digestive metabolism (MYH, TRHDE, ALDH1A3), and nervous and autoimmune response (GRIA1, IL2, IL7, IL21, IL1R1) were identified. We also identified eight common candidate genes under selection in the two species and a shared selection signature that spanned a conserved syntenic segment to bovine chromosome 12 on caprine and ovine chromosomes 12 and 10, respectively, providing, most likely, the evidence for selection in a common environment in two different but closely related species. Our study highlights the importance of indigenous livestock as model organisms for investigating selection sweeps and genome-wide association mapping.     

Comparison between the communities of parasitic nematoda of sheep and goats bred in arid zones of Venezuela

Under the studied conditions, the structure and composition of community of parasitic nematodes observed in both sheeps and goats, is similar (rS = 0.90 P less than or equal to 0.05 and CSS = 93.33%), the Shannon-Weaver index of diversity was 1.23 +/- 0.15 bits and 1.15 +/- 0.24 bits for sheeps and goats, respectively. The equitability index resulted in 0.49 +/- 0.06 for sheep-nematodes and 0.44 +/- 0.09 for goats-nematodes. However, no significant difference was observed when the means of these indexes, were compared. Not withstanding, a greater homogenity was observed in the ovine parasitic nematodes.     

The dietary overlap between red kangaroos (Macropus rufus) and sheep (Ovis aries) in the arid rangelands of Australia

Abstract The interaction between red kangaroos and sheep in the more arid areas of Australia was examined by means of a large-scale manipulative experiment. The diets of red kangaroos and sheep grazing together and separately in large paddocks were studied to assess whether competition for food might influence diet selection in these species. Diets and the amount of intra- and interspecific dietary overlap varied in accordance with pasture conditions. At pasture biomasses ranging from 50 to 200 g m^?2 (dry weight [wt]), the diets of red kangaroos and sheep overlapped by 58–73%, with forbs and grasses being the major items in the diets of both species. The diets of both sheep and red kangaroos under different experimental regimes were similar. In dry times (pasture biomass 40–50 g m^?2 (dry wt) more shrubs were eaten by both species and the amount of dietary overlap tended to be lower (52–66%). The diets of kangaroos were similar between paddocks. However, in paddocks containing both species sheep consumed proportionately more chenopodaceous shrubs and fewer grasses than those in ‘kangaroo-free’ paddocks.     

Myrmecochory in some plants (F. chenopodiaceae) of the Australian arid zone

Summary Several common plants (Chenopodiaceae) of the Australian arid zone produce diaspores that bear small and inconspicuous food bodies and are adapted for dispersal by ants. For these species, myrmecochory probably represents an adaptation for highly directional dispersal of diaspores to favorable microsites where nutrients are concentrated and possibly more accessible. Dispersal of diaspores by ants can have a pronounced effect on plant dispersion. In habitats characterized by red, crusty alluvial loam soils, myrmecochorous species grow almost exclusively on ant mounds; these same species grow in relatively continuous stands in sandy soil habitats. The flora of the Australia arid zone may contain many plant species that are adapted to use ants as dispersal agents. We consider several factors that may have promoted or facilitated the evolution of myrmecochory in arid zone plants.     

Water relations in three species of theConvolvulaceae in the Indian arid zone

The relationship of water deficit, actual water content, area, water loss and stomatal behaviour in leaves of different insertion levels of three members of Indian arid zoneConvolvulaceae—Merremia aegyptia, M. dissecta andIpomoea pes-caprae were measured simultaneously in the month of May, 1974, when field conditions were extremely adverse for growth. The two former species loose far more water than the latter. The values measured varied considerably with the leaf insertion levels and they reversed inI. pes-caprae when compared withMerremia species.     

Survival, ranging, habitat choice and diet of the Northern Goshawk Accipiter gentilis during winter in Northern Finland

The winter ecology of the Northern Goshawk Accipiter gentilis was studied in northern Finland in 1991-95. The data consist of 26 radiomarked hawks, of which 331 day and 299 night positions were located. Average range size was 9894 ha for males (minimum convex polygon, n = 4) and 6282 ha for females ( n = 11). Ranges calculated by the 75% harmonic mean contour gave range areas of 3283 ha for males ( n = 3) and 2753 ha for females ( n = 11). Harmonic mean centres concentrated near human settlements, implying better food availability there compared with woodland areas. Some Goshawks preyed upon animals living in the city dump in late winter. Goshawks preferred deciduous and mature conifer forests and avoided open areas such as fields and bogs. They also avoided very heterogeneous sites. The winter diet consisted mostly of Mountain Hares Lepus timidus (30.9%), Red Squirrels Sciurus vulgaris (23.6%), Brown Rats Rattus norvegicus (12.7%) and forest grouse Tetraonidae (27.1%), of which Black Grouse Tetrao tetrix was the most important (14.5%). By weight, hares constituted 70% of the biomass consumed.     

Water use and the thermoregulatory behaviour of kangaroos in arid regions: insights into the colonisation of arid rangelands in Australia by the Eastern Grey Kangaroo (Macropus giganteus)

The Eastern Grey Kangaroo (Macropus giganteus) occurs mostly in the wetter regions of eastern Australia. However, in the past 30–40 years it has moved into more arid regions (rainfall<250 mm), thus increasing its overlap zone with the xeric adapted Red Kangaroo (Macropus rufus). An increased access to water (supplied for domestic stock) may explain this range extension, but changes in the availability of preferred feed could also be involved. The water use, drinking patterns and thermoregulatory behaviour of these two species of kangaroo have been examined in a semi-free range study, during summer at an arid rangeland site. Foraging was largely nocturnal in both species and during the day they behaved to reduce heat loads. This was especially so for M. giganteus, which showed greater shade seeking. However, it still used more water (72±2.6 mL kg⁻¹ day⁻¹, mean ± SE) than M. rufus (56±7.6 mL kg⁻¹ day⁻¹) and drank twice as frequently. Although M. giganteus produced a less concentrated urine (1422±36 mosmol kg⁻¹) than M. rufus (1843±28 mosmol kg⁻¹), kidney physiology did not explain all of the differences in water metabolism between the species. Water from the feed and faecal water retention also appear to be involved. Broadly, a better access to reliable water and the utilisation of mesic microhabitats has enabled M. giganteus to make inroads into the changing rangelands of eastern Australia. However, changes in the vegetation, due to stock grazing, have also favoured M. giganteus, which is a grass eating specialist.     

Feeding behavior, rumination, reticulo-ruminal fermentation and plasma volatile fatty acids, compared in goats and sheep; influence of the diet

Two-year old Alpine she-goats (n = 3) and Texel ewes (n = 3) were compared as to eating behaviour, rumination and volatile fatty acids (VFA) in rumen and blood. The animals were fed once daily with two different proportions (20 and 80%) of barley and hay. Dry matter intake was fixed at 48 g D.M/kg P0.75 per day. In similar feeding and environmental conditions, eating behaviour and rumination of goats and sheep did not differ much: the goats tended to eat faster and there were more rumination periods in the sheep. Latency time, mean duration of rumination periods, daily rumination time and circadian pattern of rumination did not differ significantly between the two species (fig. 1). With both diets we observed a higher VFA concentration and a lower acetate/propionate ratio in the rumen of the ewes; however, rumen pH was lower only in those eating the 80% barley ration (fig. 2). Blood VFA in the jugular vein did not differ between sheep and goats (fig. 3). The proportion of cereals and hay in the diets affected rumen fermentation and rumination pattern in both species. With a higher concentrate/roughage ratio, rumen and plasma VFA increased, while the pH and acetate/propionate ratio in the lumen juice, the number of rumination periods and daily rumination time decreased. When the animals were fed the 80% barley ration, there was practically no rumination in the first 9 h after the single meal. During this time, rumen pH was minimal and VFA levels in the rumen and blood were maximal.     

Fish larvae, growth and biomass relationships in an Australian arid zone river: links between floodplains and waterholes

1. Floodplain inundation provides many benefits to fish assemblages of floodplain river systems, particularly those with a predictable annual flood pulse that drives yearly peaks in fish production. In arid‐zone rivers, hydrological patterns are highly variable and the influence of irregular floods on fish production and floodplain energy subsidies may be less clear‐cut. To investigate the importance of floodplain inundation to a dryland river fish assemblage, we sampled fish life stages on the floodplain of Cooper Creek, an Australian arid‐zone river. Sampling was focused around Windorah during a major flood in January 2004 and in isolated waterholes in March 2004 following flood drawdown. 2. Of the 12 native species known to occur in this region, 11 were present on the floodplain, and all were represented by at least two of three life‐stages – larvae, juveniles or adult fish. Late stage larvae of six fish species were found on the floodplain. There were site‐specific differences in larval species assemblages, individual species abundances and larval distribution patterns among floodplain sites. 3. Significant growth was evident on the floodplain, particularly by larval and juvenile fish, reflecting the combination of high water temperatures and shallow, food rich habitats provided by the relatively flat floodplain. 4. Low variation in biomass, species richness and presence/absence of juvenile and adult fish across four floodplain sites indicates consistently high fish productivity across an extensive area. 5. Similarities and differences in fish biomass between the floodplain and isolated post‐flood waterholes suggest high rates of biomass transfer (involving the most abundant species) into local waterholes and, potentially, biomass transfer by some species to other waterholes in the catchment during floodplain inundation and after floods recede. 6. The high concentration of fish on this shallow floodplain suggests it could be a key area of high fish production that drives a significant proportion of waterhole productivity in the vicinity. The Windorah floodplain provides favourable conditions necessary for the spawning of some species and juvenile recruitment of the majority of species. It is also appears to be a significant conduit for the movements of fish that underpin high genetic similarity, hence population mixing, of many species throughout the Cooper Creek catchment. The high floodplain fish production in turn provides a significant energy subsidy to waterholes after floodwaters recede. 7. The identification of key sites of high fish production, such as the Windorah floodplain, may be important from a conservation perspective. Key management principles should be: maintenance of the natural flooding regime; identification of the most productive floodplain areas; and maintenance of their connectivity to anastomosing river channels and the remnant aquatic habitats that ultimately sustain this fish assemblage through long‐term dry/drought and flood cycles.     

Birth of a biome: insights into the assembly and maintenance of the Australian arid zone biota

The integration of phylogenetics, phylogeography and palaeoenvironmental studies is providing major insights into the historical forces that have shaped the Earth's biomes. Yet our present view is biased towards arctic and temperate/tropical forest regions, with very little focus on the extensive arid regions of the planet. The Australian arid zone is one of the largest desert landform systems in the world, with a unique, diverse and relatively well-studied biota. With foci on palaeoenvironmental and molecular data, we here review what is known about the assembly and maintenance of this biome in the context of its physical history, and in comparison with other mesic biomes. Aridification of Australia began in the Mid-Miocene, around 15 million years, but fully arid landforms in central Australia appeared much later, around 1-4 million years. Dated molecular phylogenies of diverse taxa show the deepest divergences of arid-adapted taxa from the Mid-Miocene, consistent with the onset of desiccation. There is evidence of arid-adapted taxa evolving from mesic-adapted ancestors, and also of speciation within the arid zone. There is no evidence for an increase in speciation rate during the Pleistocene, and most arid-zone species lineages date to the Pliocene or earlier. The last 0.8 million years have seen major fluctuations of the arid zone, with large areas covered by mobile sand dunes during glacial maxima. Some large, vagile taxa show patterns of recent expansion and migration throughout the arid zone, in parallel with the ice sheet-imposed range shifts in Northern Hemisphere taxa. Yet other taxa show high lineage diversity and strong phylogeographical structure, indicating persistence in multiple localised refugia over several glacial maxima. Similar to the Northern Hemisphere, Pleistocene range shifts have produced suture zones, creating the opportunity for diversification and speciation through hybridisation, polyploidy and parthenogenesis. This review highlights the opportunities that development of arid conditions provides for rapid and diverse evolutionary radiations, and re-enforces the emerging view that Pleistocene environmental change can have diverse impacts on genetic structure and diversity in different biomes. There is a clear need for more detailed and targeted phylogeographical studies of Australia's arid biota and we suggest a framework and a set of a priori hypotheses by which to proceed.