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1.
Understanding of resource requirements of vulnerable species is key for conservation planning. Here, we used stable carbon (δ13C) and nitrogen isotopes (δ15N) of hair from giant armadillos (Priodontes maximus) to understand individual resource use. We collected hair from 19 giant armadillos analyzing 34 samples from the Brazilian Pantanal and compared the resource use between sexes and age classes. We also assessed the relationship of isotopic values with individuals’ body mass and the habitat type used. We observed a wide variation in resource use by giant armadillos, showing that individuals consume prey that feeds on distinct resources and occupies different habitat types, indicating that there is individual variation in foraging behavior. Most giant armadillos presented a mixed diet (C3/C4 resources, forests/open areas), but a quarter of individuals had strictly C4 diets (open areas). Males are more prone to forage on C4 resources, presenting an isotopic niche 2.6-times larger than that of females. Subadults presented diets more associated with habitats with high arboreal cover (C3 resources, forests), while adults foraged more in open areas (C4 resources). This result is mirrored by the positive relationship between δ13C values and body mass, suggesting that larger giant armadillos tend to feed more in open areas. We observed that δ13C values decreased as individuals increased the use of habitats with high arboreal cover. We stress the importance of conserving the natural mosaic in the Pantanal landscape for the species persistence, given that giant armadillos require all habitat types to fulfill their dietary, spatial, and developmental needs.  相似文献   

2.
Stable isotope analysis is very useful in animal ecology, especially in diet reconstruction and trophic studies. Differences in isotope ratios between consumers and their diet, termed discrimination factors, are essential for studies of stable isotope ecology and are species‐specific and tissue‐specific. Given the specialized bamboo diet and clear foraging behavior, here, we calculated discrimination factors for carbon and nitrogen isotopes from diet to tissues (tooth enamel, hair keratin and bone collagen) for the giant panda (Ailuropoda melanoleuca), a species derived from meat‐eating ancestors. Our results showed that carbon discrimination factor obtained from giant panda tooth enamel (ε 13Cdiet‐enamel = 10.0‰) and nitrogen discrimination factors from hair keratin (Δ15Ndiet‐hair = 2.2‰) and bone collagen (Δ15Ndiet‐collagen = 2.3‰) were lower, and carbon discrimination factors from hair keratin (Δ13Cdiet‐hair = 5.0‰) and bone collagen (Δ13Cdiet‐collagen = 6.1‰) were higher than those of other mammalian carnivores, omnivores and herbivores. Such distinctive values are likely the result of a low‐nutrient and specialized bamboo diet, carnivore‐like digestive system and exceptionally low metabolism in giant pandas.  相似文献   

3.
Predator–prey size relationships are among the most important patterns underlying the structure and function of ecological communities. Indeed, these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil record. Stable isotope analysis (SIA) is a powerful remote approach to examining animal diets and paleodiets. The approach is based on the principle that isotope compositions of consumer tissues reflect those of their prey. In systems where resource isotope compositions are distributed along a body size gradient, SIA could be used to reconstruct predator–prey size relationships. We analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio–Pleistocene African savanna assemblages, and show that the range of δ13C values among mammalian prey species (herbivores and rodents) increases with body mass (BM), because C4 plant feeding (essentially grazing) is more common among larger taxa. Consequently, δ13C values of mammalian carnivores in these systems are related to species' BM, reflecting a higher average C4 prey component in the diets of larger‐bodied carnivores. This pattern likely emerges because only the largest carnivores in these systems have regular access to the C4 prey base, whereas smaller carnivores do not. The δ13C–BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator–prey size relationships in contemporary and fossil savanna assemblages, and for interpreting how various behavioral, ecological and environmental factors influence prey size selection.  相似文献   

4.
The South American grey fox Lycalopex griseus is a canid widely distributed in southern South America; however, some aspects of its biology are still poorly known. We studied the diet and density of L. griseus in the Lago Peñuelas Biosphere Reserve, in Central Chile. The trophic niche breadth was B = 6.16 (Bsta = 0.47) and prey diversity was H′ = 2.46 (Hmax′ = 3.17, J′ = 0.78). The highest proportions of prey consumed in the diet were Oryctolagus cuniculus (52.21%) and other mammals (32.78%). We compared these results with a latitudinal gradient of diet results for this species in Chile. L. griseus eats mostly mammals (>90% of total prey), consuming the rodent Phyllotis darwini and reptiles in the northern zone; Oryctolagus cuniculus, Octodon degus and Abrocoma bennetti in the central zone; Abrothrix spp. and lagomorphs in the southern zone; and Lepus capensis and Ovis aries in the austral zone. The estimated density of L. griseus in Lago Peñuelas NR was 1.3 foxes/km2.  相似文献   

5.
The stable carbon isotope technique has been widely used to infer the dietary ecology of a range of animal species; however calibration of the technique with animals fed known diets is essential for accurate back-calculation of dietary preferences. The aim of this study was to identify suitable samples and back-calculation methods to predict short-term (2 to 3 week) dietary selection by sheep among plants with C3 and C4 photosynthetic pathways. Variation in integration time of dietary carbon into plasma and faeces; diet-tissue discrimination of carbon isotopes (fractionation) and the importance of accounting for the digestible or indigestible components of the diet was investigated. The results indicate that faecal and rumen samples provided the most accurate prediction of short term dietary changes in sheep selecting between C3 and C4 plants. The most accurate back-calculation method for these samples used δ13C of the C3 and C4 plants and accounted for both diet-tissue discrimination and differences in the indigestibility between the C3 and C4 forage. For faecal samples, the organic matter content of the diet originating from C4 plants could be predicted with a mean error as low as 2.7%. Wool and plasma samples were not conducive to predicting proportion of C4 forage in the diet within 18 days after a change in diet; however plasma could be used to discriminate between animals fed 100% C3 and C4 diets after 3 days. The δ13C technique provides a valuable tool for researchers when designing pastures for dual environmental and production purposes. An understanding of what sheep select allows for development of appropriate grazing management strategies to optimise productivity and/or persistence of target species.  相似文献   

6.
Sceloporus lizards depend on external heat to achieve their preferred temperature (Tsel) for performing physiological processes. Evidence both in the field and laboratory indicates that pregnant females of this Genus select body temperatures (Tb) lower than 34 °C as higher temperatures may be lethal to embryos. Therefore, thermoregulation is crucial for successful embryo development. Given the increase in global air temperature, it is expected that the first compensatory response of species that inhabit tropical climates will be behavioral thermoregulation. We tested whether viviparous Sceloporus formosus group lizards in the wild exhibited differences in thermoregulatory behavior to achieve the known Tsel for developing embryos regardless of local thermal conditions. We quantified field active body temperature, thermoregulatory behavior mechanisms (time of sighting, microhabitat used and basking time) and available microhabitat thermal conditions (i.e. operative temperature) for 10 lizard species during gestation, distributed along an altitudinal gradient. We applied both conventional and phylogenic analyses to explore whether Tb or behavioral thermoregulation could be regulated in response to different thermal conditions. These species showed no significant differences in field Tb during gestation regardless of local thermal conditions. In contrast, they exhibited significant differences in their behavioral thermoregulation associated with local environmental conditions. Based on these observations, the differences in thermoregulatory behavior identified are interpreted as compensatory adjustments to local thermal conditions. We conclude that these species may deal with higher temperatures predicted for the tropics by modulating their thermoregulatory behavior.  相似文献   

7.
Conditioned taste aversion (CTA) is an adaptive learning mechanism whereby a consumer associates the taste of a certain food with symptoms caused by a toxic substance, and thereafter avoids eating that type of food. Recently, wildlife researchers have employed CTA to discourage native fauna from ingesting toxic cane toads (Rhinella marina), a species that is invading tropical Australia. In this paper, we compare the results of 2 sets of CTA trials on large varanid lizards (“goannas,” Varanus panoptes). One set of trials (described in this paper) exposed recently‐captured lizards to sausages made from cane toad flesh, laced with a nausea‐inducing chemical (lithium chloride) to reinforce the aversion response. The other trials (in a recently‐published paper, reviewed herein) exposed free‐ranging lizards to live juvenile cane toads. The effectiveness of the training was judged by how long a lizard survived in the wild before it was killed (fatally poisoned) by a cane toad. Both stimuli elicited rapid aversion to live toads, but the CTA response did not enhance survival rates of the sausage‐trained goannas after they were released into the wild. In contrast, the goannas exposed to live juvenile toads exhibited higher long‐term survival rates than did untrained conspecifics. Our results suggest that although it is relatively easy to elicit short‐term aversion to toad cues in goannas, a biologically realistic stimulus (live toads, encountered by free‐ranging predators) is most effective at buffering these reptiles from the impact of invasive toxic prey.  相似文献   

8.
Horseshoe crabs, the most well-known example of “living fossils”, are iconic and ecologically important macroinvertebrates in coastal and estuarine ecosystems. Their blood is a crucial resource for manufacturing Limulus or Tachypleus amebocyte lysate to detect bacterial endotoxins or fungal contamination in drug and medical devices. An enhanced understanding of their ecological roles and trophic interactions in the food webs is fundamental to facilitate resource management for the declining populations in Asia. Foraging information of the Asian species, however, is mainly derived from preliminary, scattered reports from a limited number of study locations. In this study, resource utilization, trophic niche dynamics, and trophic interaction of the juvenile tri-spine horseshoe crab, Tachypleus tridentatus (instars 1–12, approximately 0.5–8 years old) across ontogeny was assessed in diversified nursery habitats along the northern Beibu Gulf, China, using carbon and nitrogen stable isotopes. Our results suggest that: (i) T. tridentatus are ecological generalists given the vast range of carbon isotopic values and trophic niche width estimates exhibited between multiple instar groups; (ii) juvenile T. tridentatus across most habitat types predominantly assimilated energy from a variety of basal production sources in the food web, but primarily depended on sedimentary organic matter and seagrass resource pools; (iii) ontogenetic shifts in juvenile dietary proportions were evident, with decreased reliance on sedimentary organic matter, coupled with increased reliance on benthic macroinvertebrate grazers, detritivores, and omnivores with age; and (iv) nearly all juvenile instars occupied similar trophic positions in the food web with slight shifts in trophic position present with increasing size. Our findings indicate that resource availability and ontogenetic diet shifts strongly influence horseshoe crab trophic dynamics, and age should be accounted when formulating habitat conservation measures based on resource use for Asian horseshoe crabs.  相似文献   

9.
The lizard Angolosaurus skoogi inhabits the surface and subsurface environments of sand dunes of the northern Namib Desert. We have related posture, locomotion, and other aspects of surface activity to the microclimate prevailing above and below the surface. Globe temperature was the best microclimatic correlate of surface activity. From our analysis, we concluded that surface thermoregulatory behaviour of A. skoogi is facultative, and aimed at maintaining a body temperature compatible with foraging and other obligatory surface activities.  相似文献   

10.
伊犁绢蒿是新疆蒿属荒漠草地常见的草地建群种之一,春季担负着家畜体膘的恢复和产羔育幼,秋季家畜要在该草地上贮存更多的能量和为繁衍下一代而进行配种。以蒿属荒漠草地为基础,以伊犁绢蒿为研究对象,结合野外定点取样,分析了伊犁绢蒿根、茎、叶中可溶性糖含量在不同刈割强度下随时间的动态变化,同时,在数据分析的基础上,明确了伊犁绢蒿秋季和春季营养物质贮存和消耗始期,并对不同刈割强度下伊犁绢蒿秋季根中可溶性糖的贮存量与来年春季植物体萌发消耗碳水化合物量之间的关联性做出判断。结果表明,根部可溶性糖含量在10月15日前后完成积累,在来年植株返青时,地下(根部)的营养物质就开始消耗,向地上运输,供植株返青和生长。C2处理不仅在秋季可溶性糖积累最高,而且在来年春季植株返青生长后在体内仍然能保持一个较高的水平,C0处理在秋季或春季植株体内可溶性糖含量在4个处理中总最低,直接影响株体越冬和次年返青。这表明不刈割并不是牧草最好的恢复方式,适度刈割有利于牧草的生长和体内可溶性糖的循环利用,但C0只能使植株处于劣势或死亡。  相似文献   

11.
《African Zoology》2013,48(2):158-164
Seasonal floodplains occasionally comprise highly productive zooplankton communities which are exposed to rapid shifts in predator regimes, also between vertebrate and invertebrate predators.We recorded the impact of two co-occurring zooplankton predators, the notonectid Anisops sardea and 0+ fish fry of Tilapia rendalli (max gape size 1 mm), on a cladoceran community dominated by Ceriodaphnia reticulata (0.25–0.78 mm), Daphnia laevis (0.6– 1.8 mm) and Scapholeberis kingi (0.27–0.8 mm). Both predators strongly reduced abundance of all prey species, yet with a striking size-selective effect for Daphnia prey only, where fish showed a strong preference for small individuals, while Anisops preferred large Daphnia individuals. This contrasts with the general view of size selection in invertebrate versus vertebrate predators, but is logically caused by the feeding mode of the notonectid, and the gape size limitation of the fish fry. The two predators also showed a dietary niche differentiation in terms of both prey selection and habitat choice. T. rendalli fed preferably on small species and size classes, whereas predation from A. sardea concentrated on large prey. Competitive interference was indicated when feeding on Ceriodaphnia, and niche partitioning when feeding on the two other species. The predatory pattern suggests long-lasting coexistence in the system.  相似文献   

12.
1. The biology of six species of larks in the Namib Desert near Walvis Bay, South West Africa, was studied in 1964, 1965 and 1966.

2. All species reproduced following rainfall in summer and autumn months, with the appearance of green grass and abundant insects on which the birds fed.

3. The primarily insectivorous species, Certhilauda albofasciata, shows no seasonality in moulting and testicular development, and reproduces whenever local rainfall results in favourable feeding and nesting circumstances, while the primarily granivorous Spizoeorys starki and Eremopterix verticalis have markedly seasonal testicular and moulting cycles timed so that reproduction occurs only during the late summer and autumn months. Ammomanes grayi is intermediate in food habits and in timing of moulting and reproduction, and C. albescens and Mirafra naevia may also be intermediate in this respect.

4. S. starki and E. verticalis are the only larks that normally drink, but flocks of both species were observed that were independent of drinking water.

5. Larks avoid heat stress during daytime by keeping to the shade of stones, tufts of vegetation and mouths of rodent burrows; and nests are nearly always placed on the shady side of a stone' or tuft of grass.

6. It is suggested that larks may be successful desert occupants because they have not become highly specialized and therefore can tolerate rapidly and severely changing environ-mental conditions associated with drought and irregular rainfall.  相似文献   

13.
Lizards have been reported as important pollinators on several oceanic islands. Here we evaluate the potential role of Galápagos lava lizards (Microlophus spp.) as pollinators across their radiation. Over 3 years, we sampled pollen transport by 9 lava lizard species on the 10 islands where they are present, including 7 single‐island endemics. Overall, only 25 of 296 individuals sampled (8.4%) transported pollen of 10 plant species, the most common being Prosopis juliflora, Exodeconus miersii, Sesuvium sp. and Cordia leucophlyctis. At least 8 of these plant species were native, and none were confirmed as introduced to the archipelago. Despite the low overall proportion of individuals carrying pollen, this was observed in 7 of the nine lizard species, and on 8 of the ten main islands (Española, Fernandina, Floreana, Isabela, Marchena, Pinta, Santa Cruz and Santiago), suggesting that this is a widespread interaction. The results reported here support the potential role of lava lizards as pollinators across their radiation, although they may represent a relatively modest contribution when compared with birds and insects. However, we cannot discard that lizards may be ecologically significant for particular plant species and ecosystems given the specific climatic condition and functional diversity of each island.  相似文献   

14.
Historically, tallgrass prairie burns occurred at many seasons and frequencies. Currently, tallgrass prescribed burns often occur annually in the spring, usually for cattle forage production. Altering burning season and frequency is known to affect plant composition and biomass production, but researchers are still uncertain how burning season and frequency interact. We present the long-term effects of a factorial combination of different burn seasons (spring, summer, autumn, or variable [rotated through seasons]) and frequencies (annual or quadrennial) on the plant composition and biomass production of an ungrazed, restored tallgrass prairie in eastern Nebraska, United States. The experimental plots were established in 1978 and visually surveyed for baseline data in 1979 and 1981. Experimental burn treatments were begun in 1982. Plots were visually surveyed until 2011 with the following results: 1) annual spring and summer burns increased C4 graminoid abundance; 2) annual autumn burns increased forb abundance; 3) burn season had little effect on plant composition for quadrennial burns; and 4) variable season burns generally led to plant composition that was intermediate between annual spring/summer and annual autumn burns. We also clipped biomass to estimate aboveground annual net primary production (ANPP) in 2015, a year in which both annual and quadrennial burns occurred. Total ANPP did not differ significantly between burn frequencies nor between spring and autumn burns (772 g m? 2 average) but was lower in summer burns (541 g m? 2). ANPP results were similar to visual surveys, with significantly higher C4 graminoid ANPP in spring than autumn burns and significantly lower forb and C3 graminoid ANPP in spring than autumn burns. Overall, these results suggest autumn burns can increase forb and C3 graminoid abundance, without strongly affecting total ANPP relative to spring burns. Future studies should compare plant and livestock production between spring and autumn burns in grazed fields.  相似文献   

15.
《African Zoology》2013,48(2):261-268
Seasonal changes in the diet of Cape clawless otters Aonyx capensis feeding in the surf zone in False Bay, Western Cape Province, South Africa, were investigated by spraint (faecal) analysis. The most common prey species, during all seasons, was the Cape rock crab, Plagusia chabrus. The next most important prey species was the Cape rock lobster, Jasus lalandii, with the fish species Clinus superciliosus being equally important in winter. Other prey were fresh-water crabs, Potamonautes perlatus, octopus, Octopus granulatus, and 17 other species of fish, frogs and mammals. In winter and autumn the most important prey category was fish while in spring and summer, crustaceans were the most important. Diversity of prey was lowest in winter, increasing through the seasons from spring to autumn.  相似文献   

16.
Blood cell morphology and count are not uniform across species. Recently, between‐species comparisons revealed that the size of red blood cells is associated with body size in some lizard taxa, and this finding was interpreted in the context of the metabolic theory. In the present study, we examined the numbers and the size of blood cells in 2 species of monitor lizards, the mangrove‐dwelling monitor (Varanus indicus) and the savannah monitor (V. exanthematicus), and we compared these traits in individuals of different body size. The results revealed that during the course of ontogeny, the size of red blood cells increases with body mass. Because the mass‐specific metabolic rate decreases with body size and the cell volume‐to‐surface ratio decreases with the cell size, changes in the erythrocyte size might be the result of oxygen transport adjustment.  相似文献   

17.
The Algerian hedgehog Atelerix algirus is an insectivorous species. However, the exact composition of its natural diet remains largely undetermined, especially in relation to seasonal variations in food availability. From March to November, we simultaneously analysed the composition of 180 hedgehog faecal samples and food availability in the Soumman Valley, Algeria to assess food selection in this species. The faeces contained 196 different prey species, of which 92% belonged to the class Insecta. The highest prey species diversity was found in the Coleoptera order (100 species recorded) and the highest species occurrence was found in Hymenoptera (65% of the prey items, mainly represented by the harvester ant Messor barbarus, a crop-ravaging species). This study shows that the Algerian hedgehog is mainly a generalist species with a diet that is strongly linked to food availability. However, seasonal variations were observed in prey selection, and a notable shift in food preference was observed during autumn. The exact nature of these changes in feeding behaviour remains to be investigated, notably in relation to changes in energy requirements of this species before hibernation, in terms of quantity and/or quality.  相似文献   

18.
Global climate change is expected to influence the distribution of global biodiversity. C4 and C3 perennial grasses co-occur in the fire-prone KwaZulu-Natal uKhahlamba-Drakensberg grasslands, with C3 grass species occurring at cooler locations in the mountain range and C4 grass species at warmer locations. If a warming climate is expected to cause a contraction in the ranges of C3 grasses, evidence of temperature controlling current distributions is required. This study modelled the distribution of five C3 grass species, namely Tenaxia stricta, Tenaxia disticha, Festuca costata, Merxmuellera drakensbergensis and Merxmuellera stereophylla, to temperature-related surrogate variables using presence–absence data collected across the environmental heterogeneity of the mountain range. Distributions of each species, and of all species combined, were modelled using generalised additive models. These temperature-related variables accounted for the distribution of all five species, least so for F. costata. Four species could therefore contract in range in response to climate change, whereas F. costata is least likely to have a range contraction directly related to a warming climate and could experience a range expansion owing to the fertilising effect of increased [CO2].  相似文献   

19.
《African Zoology》2013,48(1):38-44
We examined 170 museum specimens of the southern African gekkonid lizard Homopholis wahlbergii, to quantify sexual dimorphism, male and female reproductive cycles and diet. The largest male and female we recorded were 116 and 119 mm snout–vent length (SVL) respectively. We compared SVL, tail length, head length, head width and eye diameter and found no evidence of sexual dimorphism in any of these characters. The smallest female with thickened muscular oviducts and follicles, indicating sexual maturity, was 59 mm SVL, but the smallest female we found with fully developed eggs was 85mmSVL. Virtually all females larger than 59 mm appeared to be in some stage of reproduction, suggesting that females reproduce every year once they reach sexual maturity. Egg size ranged from 17–19mm long. Egg size was not correlated with maternal SVL. We found adult females with ready-to-lay eggs during the warmer months of the year, but not during winter and spring. The smallest sexually mature male was 72 mm SVL. Virtually all males larger than this size displayed at least semi-turgid testes and most adult male testes were at least semi-turgid for much of the year. The only significant decrease in testicular activity was in mid-winter (June–August), thus, spermatogenesis is closely tied to female follicular development and ovulation. Velvet geckos are largely insectivorous (92%) and feed on a broad spectrum of prey. Their diet was dominated both numerically (34%) and volumetrically (22%) by beetles. Lepidoptera were the next most important prey category, suggesting that they exploit both terrestrial and flying invertebrates. They are unusual among lizards because they feed on millipedes. Males and females had very similar diets which may be explained by their lack of sexual dimorphism, although females tended to eat a greater volume of prey. Interestingly, less than half (37%) of the lizards examined contained prey items, suggesting that most individuals were not in positive energy balance. We also found evidence of prey size selection as a function of gape size, such that larger geckos took advantage of larger prey items.  相似文献   

20.
It is important to predict how many individuals of a predator species can survive in a given area on the basis of prey sufficiency and to compare predictive estimates with actual numbers to understand whether or not key threats are related to prey availability. Rugged terrain and low detection probabilities do not allow for the use of traditional prey count techniques in mountain areas. We used presence–absence occupancy modeling and camera‐trapping to estimate the abundance and densities of prey species and regression analysis to predict leopard (Panthera pardus) densities from estimated prey biomass in the mountains of the Nuvadi area, Meghri Ridge, southern Armenia. The prey densities were 12.94 ± 2.18 individuals km?2 for the bezoar goat (Capra aegagrus), 6.88 ± 1.56 for the wild boar (Sus scrofa) and 0.44 ± 0.20 for the roe deer (Capreolus capreolus). The detection probability of the prey was a strong function of the activity patterns, and was highest in diurnal bezoar goats (0.59 ± 0.09). Based on robust regression, the estimated total ungulate prey biomass (720.37 ± 142.72 kg km?2) can support a leopard density of 7. 18 ± 3.06 individuals 100 km?2. The actual leopard density is only 0.34 individuals 100 km?2 (i.e. one subadult male recorded over the 296.9 km2), estimated from tracking and camera‐trapping. The most plausible explanation for this discrepancy between predicted and actual leopard density is that poaching and disturbance caused by livestock breeding, plant gathering, deforestation and human‐induced wild fires are affecting the leopard population in Armenia.  相似文献   

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