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1.
Abstract Squamate reptiles are significant components of woodland vertebrate communities in eastern Australia, but their ecology is poorly understood. We investigated seasonal variation in habitat use by the Inland Carpet Python, Morelia spilota metcalfei Wells and Wellington (Pythonidae), a threatened snake that inhabits the woodland environments of the Murray–Darling Basin. Nine pythons were radiotracked within and near the Mount Meg Flora and Fauna Reserve in north‐eastern Victoria to investigate how habitat structure and prey distribution (namely, that of the European Rabbit, Oryctolagus cuniculus L. (Leporidae)) influenced seasonal movement patterns. Data were analysed over three spatial scales to allow firm interpretations regarding resource selection. Pythons exhibited distinct seasonal trends in habitat use. During the cooler spring months, snakes chose warm, well‐insulated microhabitats, primarily rocky outcrops on north‐ and north‐west‐facing hillsides. Pythons moved widely during the summer months, apparently in search of prey. Snake localities could be readily linked to rabbit distribution at this time. Specifically, snakes moved to more open, disturbed habitats that contained a high density of rabbits, and consistently selected microhabitats in close proximity to rabbit burrows. In autumn, habitat use was transitional, as snakes progressively returned to the rocky hillsides where they overwintered. Thus, trends in habitat use were influenced by the snakes' thermoregulatory and foraging strategies. Careful management of specific habitats and feral prey populations is required to conserve populations of this endangered snake.  相似文献   

2.
Despite increased worldwide popularity of keeping reptiles as pets, we know little about hematologic and biochemical parameters of most reptile species, or how these measures may be influenced by intrinsic and extrinsic factors. Blood samples from 43 wild-caught pythons (Morelia spilota imbricata) were collected at various stages of a 3-yr ecological study in Western Australia. Reference intervals are reported for 35 individuals sampled at the commencement of the study. As pythons were radiotracked for varying lengths of time (radiotransmitters were surgically implanted), repeated sampling was undertaken from some individuals. However, because of our ad hoc sampling design we cannot be definitive about temporal factors that were most important or that exclusively influenced blood parameters. There was no significant effect of sex or the presence of a hemogregarine parasite on blood parameters. Erythrocyte measures were highest for pythons captured in the jarrah forest and at the stage of radiotransmitter implantation, which was also linked with shorter time in captivity. Basophil count, the only leukocyte influenced by the factors tested, was highest when the python was anesthetized, as was globulin concentration. Albumin and the albumin:globulin ratio were more concentrated in summer (as was phosphorous) and at the initial stage of radiotransmitter placement (as was calcium). No intrinsic or extrinsic factors influenced creatinine kinase, aspartate aminotransferase, uric acid, or total protein. This study demonstrates that factors including season, location, surgical radiotransmitter placement, and anesthetic state can influence blood parameters of M. s. imbricata. For accurate diagnosis, veterinarians should be aware that the current reference intervals used to identify the health status of individuals for this species are outdated and the interpretation and an understanding of the influence of intrinsic and extrinsic factors are limited.  相似文献   

3.
Sexual dimorphism is usually interpreted in terms of reproductive adaptations, but the degree of sex divergence also may be affected by sex-based niche partitioning. In gape-limited animals like snakes, the degree of sexual dimorphism in body size (SSD) or relative head size can determine the size spectrum of ingestible prey for each sex. Our studies of one mainland and four insular Western Australian populations of carpet pythons ( Morelia spilota ) reveal remarkable geographical variation in SSD, associated with differences in prey resources available to the snakes. In all five populations, females grew larger than males and had larger heads relative to body length. However, the populations differed in mean body sizes and relative head sizes, as well as in the degree of sexual dimorphism in these traits. Adult males and females also diverged strongly in dietary composition: males consumed small prey (lizards, mice and small birds), while females took larger mammals such as possums and wallabies. Geographic differences in the availability of large mammalian prey were linked to differences in mean adult body sizes of females (the larger sex) and thus contributed to sex-based resource partitioning. For example, in one population adult male snakes ate mice and adult females ate wallabies; in another, birds and lizards were important prey types for both sexes. Thus, the high degree of geographical variation among python populations in sexually dimorphic aspects of body size and shape plausibly results from geographical variation in prey availability.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 113–125.  相似文献   

4.
Understanding an organism's home range is an important component of effective wildlife management. However, home ranges can vary spatially and temporally within and between populations. Landscape ecology theory can provide a framework for understanding spatio‐temporal variability in animal traits. We used radio‐telemetry in a population of diamond python Morelia spilota spilota Lacépède (Pythonidae) from a biologically rich and structurally heterogeneous reserve in eastern Australia to explore the relationship between home range size, optimal foraging theory and vegetation mosaic theory. Twelve adult snakes were tracked between September 2004 and February 2008. Male home ranges were significantly larger (P < 0.05) and more variable (41 ± 30 ha) than female home ranges (23 ± 5 ha), and males moved further between observations (123 m c.f. 65 m). Core activity centres varied significantly among habitat (P < 0.05) with larger home ranges observed in heathland, a vegetation community which supported comparatively low mammal diversity. No other variables examined including number of fixes, body length, prey abundance, vegetation heterogeneity or fire history explained home range variability. In this system, relatively high mammalian prey diversity and rapid post‐fire vegetation succession may limit prey availability and fire effects as being significant determinants of home range variability in M. spilota.  相似文献   

5.
R. Shine  M. Fitzgerald 《Oecologia》1995,103(4):490-498
Although adaptationist hypotheses predict a functional relationship between mating systems and sexual size dimorphism, such predictions are difficult to test because of the high degree of phylogenetic conservatism in both of these traits. Taxa that show intraspecific variation in mating systems hence offer valuable opportunities for more direct tests of evolutionary-ecological hypotheses. Based on a collation of published and unpublished records, we document intraspecific geographic variation in mating systems (presence versus absence of male-male combat) within the widely-distributed Australian python Morelia spilota. Radiotelemetric monitoring of 19 free-ranging pythons in a population in north-eastern New South Wales showed that these animals display a mating system of female defence polygyny. Previous studies on a southern population of the same species found that males engaged in long mate-searching movements, showed no overt agonistic behavior, and formed long-term (>2 months) aggregations around reproductive females. In strong contrast, our adult male carpet pythons (i) moved about relatively little (mean displacement <11 m/day) during the mating season, (ii) remained with females only briefly (<5 days), and (iii) engaged in male-male combat in the vicinity of females. This male-male combat included vigorous biting as well as ritualised wrestling matches, resulting in a high incidence of bite scars in adult males. In keeping with predictions from sexual selection theory, males attain larger body sizes than females in this population, whereas females grow larger than males in the previously-studied southern population where males do not engage in physical combat for mating opportunities.  相似文献   

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8.
Abstract: Despite outnumbering their temperate counterparts, tropical snake species have been poorly studied. Yet, the few tropical species that have been studied show a variety of behavioural traits beyond those described in temperate species. Here we reveal both age and sexual differences in the movements of tropical green pythons (Morelia viridis: Pythonidae). We radio‐tracked 27 individuals (17 females and 10 males) for up to 18 months, locating individuals during both the day and night. The home range size for adult females (mean ± SE of 6.21 ± 1.85 ha) was correlated with snout–vent length. Neither adult males nor juveniles had a stable home range. Adult females had stable home ranges that overlapped considerably with those of other females and yellow individuals. Multiple radio‐tracked adult males passed through the territory of radio‐tracked adult females during the study. Females of all sizes were more likely to change position each day than males. There were no differences between the sexes or size categories in the distances moved in most months, although the variation in movement distances was higher in the dry season than during the wet season. In the wet season (January–March) movement distances increased and these were size‐ and sex‐related. This increased activity may be associated with mate searching. Males of M. viridis may maximize their rate of encountering mature females by roaming rather than maintaining a home range. Juvenile green pythons moved distances equal to adult snakes in most months despite their comparatively small size.  相似文献   

9.
Information on the movement ecology of species can assist with identifying barriers to dispersal and appropriate management actions. We focus on the threatened Malleefowl (Leipoa ocellata) whose ability to move and disperse within fragmented landscapes is critical for their survival. We also investigate the possible effects of climate change on Malleefowl movement. We used solar-powered GPS telemetry to collect movement data and determine the influence of breeding status, remnant vegetation patches and environmental variables. Seven Malleefowl were tracked between 1 and 50 months, resulting in 20 932 fixes. While breeding, Malleefowl had significantly smaller home ranges (92 ± 43 ha breeding; 609 ± 708 ha non-breeding), moved shorter daily distances (1283 ± 605 breeding; 1567 ± 841 non-breeding) and stayed closer to the incubation mound (349 ± 324 m breeding; 3293 ± 2715 m non-breeding). Most Malleefowl effectively disassociated from the mound once breeding stopped, with two birds dispersing up to 10.2 km. Movement patterns were significantly correlated with the size of the remnant native vegetation patch, with smaller home ranges being utilized in small patches than in large patches. One male almost exclusively remained within a 107-ha patch for over 4 years, but a female crossed between closely spaced uncleared patches. Long-range movements of nearly 10 km daily displacement were recorded in large remnants almost exclusively when not breeding. Temperature and rain had a significant effect on movement: modelling suggests daily distances decline from 1.3 km at 25°C to 0.9 km at 45°C, with steeper declines over 30°C. The influence of patch size on movement patterns suggests that Malleefowl movement may be governed by the size of remnant patches and that habitat continuity may be important for facilitating recolonization after catastrophic events and maintaining genetic diversity. Climate change may reduce Malleefowl movement during hot, dry periods possibly affecting breeding success.  相似文献   

10.
This study monitored post-release movements of 20 wild Japanese eels (Anguilla japonica) [mean ± S.D. 520.8 ± 92.3 mm total length (TL), 217.9 ± 146.3 g body mass (BM)] in a brackish water lagoon in northeastern Japan using acoustic telemetry to elucidate how wild Japanese eels use different river, estuary and marine environments. In addition, 12 cultured Japanese eels (TL = 578.9 ± 18.0 mm, BM = 344.9 ± 25.5 g) were released to understand the comparative behaviours of wild and cultured eels. Both types of eels were simultaneously released in the southern inner part of the lagoon in September 2016 where there are freshwater influences from a river. Following release, eight of the wild eels (40%) were largely sedentary near the released point (river mouth) and stayed at the site for overwinter. Nonetheless, several individuals showed behavioural plasticity of habitat use: three wild eels moved towards the northern part of the lagoon with stronger influence from the sea during May–July 2017. Two wild eels showed clear repeated movements from the lagoon to a river at night and returned to the lagoon by dawn for more than a week every day, and one wild eel migrated upstream for overwintering. Signals from 55% of the wild eels could be detected for more than 6 months, whereas those from all of the cultured eels were lost by December 2016, indicating a short resident time of large cultured eels (BM > 200 g) released in a brackish water area. One wild silver eel migrated to the outer sea during the ebb tide at night in November 2016, probably triggered by the decrease in water temperature (from c. 20°C to c. 13°C), and seven cultured eels similarly moved to the outer sea during October–November 2016. The results revealed the similarities (e.g., nocturnal movements) and differences (e.g., stay period and seasonal movements) in the behavioural characteristics of wild and cultured eels and indicated that habitat connectivity among river, estuary and coastal waters is crucial for enabling eels to efficiently utilise these productive habitats through their behavioural plasticity.  相似文献   

11.
The goal of this study was to investigate the ecological flexibility of Tonkean macaques (Macaca tonkeana) by examining how they respond to human-induced habitat alteration. To do so, I observed movement patterns, forest strata use, microhabitat use, and home range use in two groups that occupied habitats with different levels of human alteration and habitat quality in Lore Lindu National Park, Sulawesi, Indonesia. The group occupying the heavily altered habitat (Anca) spent a significantly greater proportion of time traveling on the ground than the group in minimally altered habitat (CH), and significantly more time than expected in microhabitats within their range that were characterized by greater alteration (e.g., agroforestry areas). There was no significant difference between the two groups in daily path length, despite differences in group size. The Anca group exhibited a greater home range area per individual than the CH group, and utilized a more limited area within their home range with greater intensity, relative to the CH group. Tonkean macaques therefore show considerable flexibility in response to anthropogenic disturbance by adjusting their use of forest strata to facilitate travel and increase foraging opportunities and by intensively using particular areas within their home range where known resources are present and predictably available.  相似文献   

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The lack of long-term studies remains a limiting factor in understanding the home range, spatial ecology and movement of giraffes. We equipped eight giraffes with GPS satellite units and VHF capacity, which were built in to the collars for the remote collection of data on their movements and home ranges over two years on Khamab Kalahari Nature Reserve (KKNR) within the Kalahari region of South Africa. Giraffe numbers in KKNR dropped from 135 individuals to 111 in just five years, revealing the lack of knowledge about their required habitat needs, space use and diet. With over 1000 km2 available for roaming within the reserve, habitat selection, principle and preferred food species played a significant role in home range size and overlap between individuals. These giraffes used an average annual home range of 206 km2 (20 602 ha) as calculated by a 95% minimum convex polygon (MCP) with a standard deviation core home range calculated by a 50% MCP of 10.1 km2 to satisfy their annual needs for survival and reproduction in their preferred vegetation. In the wet, hot season (summer: December–February) when food was abundant, giraffes frequented smaller areas (average 177 km2), while in the dry, cool season (winter: June to August) the mean home range size increased to approximately 245 km2. Rainfall influenced spatial distribution since it determined vegetation productivity and leaf phenology. The different seasons influenced giraffe movements, while different vegetation types and season influenced their home range size. Season and food availability also influenced home range overlap between different giraffe herds. Home range overlap occurred when giraffes were forced to roam in overlapping areas during the dryer months when the winter deciduous nature of the majority of the tree species resulted in lower food availability. In winter, the overlap was approximately 31% and in autumn approximately 23%. During the wet and warmer months, overlapping was 15% in summer and 19% in spring, respectively. The percentage of time spent in different vegetation type areas was influenced by the abundance of the principal food species of that plant community. It is thus concluded that the movements of giraffes were primarily influenced by a combination of environmental factors such as season, rainfall and vegetation density.  相似文献   

14.
The feeding behavior of a group of titis (Callicebus coimbrai) was monitored over an annual cycle at a site in northeastern Brazil. Behavioral data were collected in scan samples (1-min scan at 5-min intervals), and complementary data on fruit availability and new leaf cover were collected. Feeding time accounted for 28.9% of daily activity. Fruit was the principal item of the diet (61.2% of records) and the primary category in all months except September, when it was surpassed by leaves. Young leaves were the second most important category (20.0%). The consumption of seeds and insects was prominent in November and December. Fifty-two plant species were exploited, and the Elaeocarpaceae, Myrtaceae, Sapotaceae, and Passifloraceae provided the vast majority (86.0%) of plant feeding records. The phenological record did not provide a good measure of fruit availability, but a strong correlation (r(s) =0.902, P<0.0001, n=12) was found between the consumption of leaves and the exploitation of lianas each month. Lianas accounted for 28.2% of plant feeding records, and predominated between August and December. This suggests that lianas may represent a key factor in the ability of the species to tolerate the intense habitat fragmentation found throughout its geographic range.  相似文献   

15.
While movements of organisms have been studied across a myriad of environments, information is often lacking regarding spatio‐seasonal patterning in complex temperate coastal systems. Highly mobile fish form an integral part of marine food webs providing linkages within and among habitats, between patches of habitats, and at different life stages. We investigated how movement, activity, and connectivity patterns of Atlantic cod (Gadus morhua) are influenced by dynamic environmental conditions. Movement patterns of 39 juvenile and subadult Atlantic cod were assessed in two coastal sites in the Swedish Skagerrak for 5 months. We used passive acoustic telemetry and network analysis to assess seasonal and spatial movement patterns of cod and their relationships to different environmental factors, using statistical correlations, analysis of recurrent spatial motifs, and generalized linear mixed models. Temperature, in combination with physical barriers, precludes significant connectivity (complex motifs) within the system. Sea surface temperature had a strong influence on connectivity (node strength, degree, and motif frequency), where changes from warmer summer waters to colder winter waters significantly reduced movement activity of fish. As the seasons changed, movement of fish gradually decreased from large‐scale (km) linkages in the summer to more localized movement patterns in the winter (limited to 100s m). Certain localized areas, however, were identified as important for connectivity throughout the whole study period, likely due to these multiple‐habitat areas fulfilling functions required for foraging and shelter. This study provides new knowledge regarding inshore movement dynamics of juvenile and subadult Atlantic cod that use complex, coastal fjord systems. The findings show that connectivity, seasonal patterns in particular, should be carefully considered when selecting conservation areas to promote marine stewardship.  相似文献   

16.
The abundance of food, especially that of fruit and often that of young leaves, varies considerably over time for most primates. This variation can depend on or be independent of seasonality in rainfall. Mountain gorillas (Gorilla gorilla beringei) in the Virungas are exceptional: their habitat contains almost no edible fruit, and they mostly eat perennially available herbs and vines that are densely and evenly distributed in much of their habitat. Earlier studies documented little consistent temporal variation in mountain gorilla diets and habitat use, except for seasonal use of bamboo by some groups, and documented no birth seasonality. Long-term data ( 7 years) on 6 mountain gorilla groups confirm these results for habitat use, except that they show some seasonality in use of the upper altitudinal extremes of the gorillas' home ranges for unclear reasons. Relatively low and inconsistent variation in habitat quality over time should lower the costs of grouping for gorillas compared to other apes. Long-term data also confirm the absence of seasonality in births and conceptions. However, they show that mortality rates and risk of respiratory infections vary directly with rainfall. These relationships are probably causal and may be mediated through thermoregulatory stress.  相似文献   

17.
Advances in tracking technology have led to an exponential increase in animal location data, greatly enhancing our ability to address interesting questions in movement ecology, but also presenting new challenges related to data management and analysis. Step‐selection functions (SSFs) are commonly used to link environmental covariates to animal location data collected at fine temporal resolution. SSFs are estimated by comparing observed steps connecting successive animal locations to random steps, using a likelihood equivalent of a Cox proportional hazards model. By using common statistical distributions to model step length and turn angle distributions, and including habitat‐ and movement‐related covariates (functions of distances between points, angular deviations), it is possible to make inference regarding habitat selection and movement processes or to control one process while investigating the other. The fitted model can also be used to estimate utilization distributions and mechanistic home ranges. Here, we present the R package amt (animal movement tools) that allows users to fit SSFs to data and to simulate space use of animals from fitted models. The amt package also provides tools for managing telemetry data. Using fisher (Pekania pennanti) data as a case study, we illustrate a four‐step approach to the analysis of animal movement data, consisting of data management, exploratory data analysis, fitting of models, and simulating from fitted models.  相似文献   

18.
The African White-backed Vulture Gyps africanus is widely distributed across sub-Saharan Africa but populations are in decline. Loss of suitable habitat for foraging and breeding are among the most important causes, and future conservation will require identification of suitable remaining habitat and the threats to it and to the vultures in it. Like many large raptors, African White-backed Vultures have a long breeding cycle and thus spend much of each year near their nest site, but ecological correlates of nest sites have not been quantified for any African vulture species. We use nest-site data for African White-backed Vultures collected during aerial and ground surveys and habitat data derived from a GIS to develop statistical models that estimate the probability of nest presence in relation to habitat characteristics, and test these models against an independent dataset. The models predicted that both direct and indirect disturbance by humans limit the potential distribution. Suitable habitat needs to be identified and receive adequate protection from poaching. Poaching of vultures is thought to be mainly for use in traditional medicine and does not target any particular species, so all vulture species can be considered equally at risk. We predict the likelihood of individuals nesting in currently unprotected areas should they become protected. These predictions show that readily available GIS data combined with relatively simple statistical modelling can provide meaningful large-scale predictions of habitat availability.  相似文献   

19.
Ecological studies on seasonally dry tropical forest herpetofauna are scarce and those focused on interspecific relations of lizards in this endangered ecosystem are even fewer. This study evaluates general and seasonal patterns in time and habitat use among four lizard species (Anolis nebulosus, Sceloporus melanorhinus, S. utiformis, and Urosaurus bicarinatus) in a protected area of dry tropical forest in western Mexico. Data were gathered by visual surveys along 12 linear parallel transects located in an undisturbed habitat. Anolis nebulosus showed a bimodal pattern in daily activity whereas the other species exhibited unimodal patterns of activity. Seasonality only affected the general activity patterns of S. melanorhinus and U. bicarinatus. With the exception of A. nebulosus and S. melanorhinus, statistical differences were found for all pairwise comparisons of general and seasonal patterns of habitat use. The use of leaf‐litter and low perches in arboreal species was higher during the dry season, probably in response to higher food availability in these habitats. As expected, environmental seasonality affects both activity time and habitat use by lizards. Results suggest greater differences in habitat use than in time of activity among species. The data also indicate complementary use of time and space by these lizard species: species showing similar activity patterns exhibit greater differences in their habitat use. Predation could be an important factor affecting the use of habitat and time by the four lizard species.

Los estudios ecológicos de la herpetofauna de los bosques tropicales secos son escasos y aquellos enfocados a las relaciones ínterespecíficas en lagartijas de este ecosistema fuertemente amenazado son aún más raros. Este estudio evalúa el uso del tiempo y del hábitat de cuatro especies de lagartijas (Anolis nebulosus, Sceloporus melanorhinus, S. utiformis y, Urosaurus bicarinatus) en un área protegida en el occidente de México al comparar los patrones generales y estacionales. La información se obtuvo basándose en 12 transectos visuales ubicados en bosque intacto. Anolis nebulosus registró un patrón bimodal de actividad diaria mientras que en el resto fue unimodal, pero aparentemente, la estacionalidad solo afecto los patrones generales de S. melanorhinus y U. bicarinatus. A excepción de A. nebulosus y S. melanorhinus, todas las comparaciones intraespecificas de los patrones generales y estacionales del uso del hábitat mostraron diferencias estadísticamente significativas. El uso de la hojarasca y perchas mas bajas, en las especies arborícolas, fue mayor durante la época de sequía probablemente en respuesta a una mayor disponibilidad de alimento en esos hábitats durante ese tiempo. Como se esperaba, la estacionalidad puede afectar el uso del tiempo y hábitat en lagartijas. Los resultados sugieren la posibilidad de un mayor uso diferencial del hábitat que del tiempo y la ocurrencia de un uso complementario de ellos: las especies con patrones de actividad más similares difieren más en su uso del hábitat. La depredación puede tener un efecto importante en el uso del tiempo y hábitat de estas especies de lagartijas.  相似文献   

20.
Reef flats, typically a low‐relief carbonate and sand habitat in shallow water leeward of the reef crest, are one of the most extensive zones on Pacific coral reefs. This shallow zone often supports an abundant and diverse fish assemblage that is exposed to more significant variations in physical factors, such as water depth and movement, temperature and ultraviolet (UV) radiation levels, than most other reef fishes. This review examines the characteristics of reef flat fish assemblages, and then investigates what is known about how they respond to their biophysical environment. Because of the challenges of living in shallow, wave‐exposed water, reef flats typically support a distinct fish assemblage compared to other reef habitats. This assemblage clearly changes across tidal cycles as some larger species migrate to deeper water at low tide and other species modify their behaviour, but quantitative data are generally lacking. At least some reef flat fish species are well‐adapted to high temperatures, low oxygen concentrations and high levels of UV radiation. These behavioural and physiological adaptations suggest that there may be differences in the demographic processes between reef flat assemblages and those in deeper water. Indeed, there is some evidence that reef flats may act as nurseries for some species, but more research is required. Further studies are also required to predict the effects of climate change, which is likely to have multifaceted impacts on reef flats by increasing temperature, water motion and sediment load. Sea‐level rise may also affect reef flat fish assemblages and food webs by increasing the amount of time that larger species are able to forage in this zone. The lack of data on reef flats is surprising given their size and relative ease of access, and a better understanding of their functional role within tropical marine seascapes is urgently required.  相似文献   

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