Article

An outback oasis: the ecological importance of bilby burrows

Authors:
  • Department of Primary Industries and Regional Development, WA
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Abstract

Ecosystem engineers are species that have a role in creating and maintaining certain habitat traits that are important for other species. Burrowing species do this by creating subterranean refugia from predation and thermal extremes, but also providing foraging opportunities through soil movement and by increasing local landscape heterogeneity. In this study, we used camera traps to monitor the burrows of greater bilbies (Macrotis lagotis), a vulnerable Australian marsupial, in an area subject to frequent disturbance by fire. We tested the hypothesis that bilby burrows provide refuge for other species and therefore their presence increases biodiversity. In total, 45 taxa – 22 bird, 16 reptile and 7 mammal taxa – were recorded interacting with 127 burrows across 7 sites. Species richness was greater at burrows compared with vegetation away from burrows, while abundance was no different. There was no difference in species assemblage for bilby burrows that were actively maintained by bilbies compared with abandoned burrows, although there was more activity at bilby maintained burrows. A wildfire allowed us to test the ad hoc hypothesis that the use of bilby burrows was greater when vegetation cover was removed by fire. We recorded significant differences in species assemblage interacting with burrows after fire, although overall species richness and abundance did not change. The response of individual species was variable; for example, burrows provide a refuge for smaller species (such as mice and small reptiles), and may therefore protect them from the effects of fire. Where they persist, bilbies provide an important ecosystem engineering service, as their burrows support a broad range of species. Further reduction in the distribution of the bilby is therefore likely to have a flow-on effect on biodiversity, impacting species that use their burrows for refuge.

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... Although bilbies were recorded constructing burrows throughout their historic range, how individuals used burrows in different habitats was not documented. Recent research has highlighted the importance of both active and disused bilby burrows as a refuge for other species in the arid zone (Read et al. 2008;Hofstede and Dziminski 2017;Dawson et al. 2019). The extinction of bilbies and the loss of their burrows from over half of the Australian continent may also have had a negative effect on other species in temperate environments. ...
... The loss of the bilby and other burrowing species from many locations in Australia may have had implications for other species that co-existed with burrowing species (Fleming et al. 2014). In a tropical monsoonal climate, 45 species of mammal, bird and reptile have been recorded as interacting with bilby burrows (Dawson et al. 2019). Similarly, in both the arid zone and temperate environments of Australia, a wide variety of mammal, bird and reptile species have been recorded using the burrows of other species (Wood Jones 1924;Copley 1999;Haby et al. 2013;Ostendorf et al. 2016;Hofstede and Dziminski 2017;Thornett et al. 2017). ...
Article
Remnant natural populations of greater bilbies (Macrotis lagotis) are confined to the Australian arid zone where bilbies construct and shelter in multiple burrows within their home range. We investigated burrow use behaviour of bilbies in a translocated population in temperate southern Australia to determine if behaviour differed in this climatic zone. Over a 12 month period, 43 adult bilbies at Venus Bay Conservation Park were spool-and-line tracked to 118 burrows. Active burrow density was 0.55 per ha, and bilbies at the site used multiple burrows (up to 13 for males and 8 for females) and regularly moved between diurnal burrows. Male bilbies had significantly larger burrow ranges (10.2 � 5.8 ha, MCP100, mean � s.d.) than females (2.6 � 1.8 ha), and were similar in size to those recorded in an arid zone population. Males’ burrow ranges tended to overlap with the burrow range of multiple other males and females. The density of burrows in the current study suggests that bilby burrows were likely to have been a common landscape feature within the southern parts of the species range prior to their local extinction. Further research is needed to determine the impact of the loss of bilby burrows from southern Australia on other burrow commensal species.
... Despite the similarity in function to cavity excavators, comparatively fewer studies have examined the role of burrow excavation on the suite of co-occuring species within differing communities (Davidson et al., 2012). Some notable exceptions include assessments of burrows excavated by prairie dogs (Cynomys sp.) and kangaroo rats (Dipodomys sp.; Davidson et al., 2008), bettongs (Bettongia lesueur; Read et al., 2008), aardvarks (Orycteropus afer; Whittington-Jones et al., 2011), greater bilbies (Macrotis lagotis; Dawson et al., 2019), giant armadillos (Priodontes maximus; Blanco et al., 2020), and gopher tortoises (Murphy et al., 2021). Many other burrow excavators remain (e.g., Davidson et al., 2012), however, and additional work is required to expand the understanding of how burrowing animals influence ecological communities. ...
... All bird species are listed on the left. This figure shows that both birds and mammals, specifically mice (Peromyscus sp.) and chipping sparrow (Spizella passerina), made up a substantial portion of interactions addressed for other fossorial mammals (e.g., Davidson et al., 2008;Dawson et al., 2019;Blanco et al., 2020;Read et al., 2008) along with the rich body of literature highlighting the cavity web (i.e., diversity and frequency of species secondarily using tree cavities) associated with woodpeckers (Cockle, Ibarra, et al., 2019;Cockle et al., 2011;Martin et al., 2004;Martin & Eadie, 1999). Our study has provided insight concerning the role of habitat provisioning by American badgers, which has substantial consequences on how we conceptualize badgers as ecosystem engineers. ...
Article
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Abstract Ecosystem engineers are organisms that influence their environment, which includes alterations leading to habitat provisioning for other species. Perhaps the most well‐examined guild of species provisioning habitat for other species is tree cavity excavators or woodpeckers (Picidae). Many studies have examined the suite of secondary cavity users that rely on woodpeckers, and how the ecological network of secondary users, collectively referred to as the nest web, changes across communities. Despite similar habitat provisioning processes, fewer studies have assessed the suite of species associated with burrowers providing access to subterranean habitat. Here, we begin to characterize the burrow web provisioned by American badgers (Taxidea taxus) and evaluate the diversity and frequency of species interactions we detected at abandoned badger burrows in Wyoming, USA. We deployed camera traps at 23 badger burrows and identified interactions with the burrow by birds, mammals, and reptiles. Overall, we discovered 31 other species utilizing badger burrows, consisting of 12 mammals, 18 birds, and 1 reptile. Mammals, other than American badgers themselves and other fossorial species such as ground squirrels (Urocitellus sp.), frequently using burrows included mice (Peromyscus sp.), long‐tailed weasel (Mustela frenata), pygmy rabbit (Brachylagus idahoensis), and desert cottontail (Sylvilagus audubonii). Of the 18 bird species detected, most accounted for
... Structural features, including those created by natural disturbances (i.e., wind, fire) and ecosystem engineers (i.e., gopher tortoises, pocket gophers), contribute to habitat heterogeneity and, therefore biodiversity (Collins and Uno, 1983, Shugart and Seagle, 1985, Wright et al., 2002. Underground refugia in terrestrial ecosystems are an example of such habitat features that increase local biodiversity (Smith and Foggin, 1999, Lai and Smith, 2003, Bravo et al., 2009, Dawson et al., 2019. ...
... Previous studies documenting vertebrate use of stump holes have either relied on in-person visual surveys or were taxa specific such as radio telemetry studies. Studies using trail cameras have been conducted on animal-constructed burrows that produced comprehensive surveys of the commensal fauna utilizing those features (Dziadzio and Smith, 2016, Thornett et al., 2017, White and Tuberville, 2017, Dawson et al., 2019. To date, no studies have conducted systematic surveys of stump holes using trail cameras which would provide this comprehensive survey of all vertebrates utilizing these habitat features due to the ability to monitor continually without the potential disturbance of a human observer. ...
Article
In the fire maintained longleaf pine (Pinus palustris) ecosystem, underground refugia such as gopher tortoise (Gopherus polyphemus) burrows and stump holes may be important for animals to escape fire and extreme temperatures. Despite being documented as refugia for several species of concern including the black pine snake (Pituophis melanoleucus lodingi) and eastern diamondback rattlesnake (Crotalus adamanteus), longleaf pine stumps are commonly removed and harvested for rosin, eliminating associated underground habitats. We used trail cameras to examine the use of stump holes by vertebrates from September 2018 – May 2019. Each of 35 stump holes was paired with a nearby gopher tortoise burrow, a documented high value refugium type, to serve as a reference. We used Shannon Diversity Index to investigate species diversity differences and non-metric multidimensional scaling to investigate species composition differences between stump holes and tortoise burrows. We developed multi-season occupancy models to investigate reptile, amphibian, bird, and small mammal occupancy differences between tortoise burrows and stump holes. We documented 13 taxa unique to stump holes, 14 taxa unique to tortoise burrows, and 26 shared taxa. Although overall species diversity was similar between tortoise burrows and stump holes, species composition differed, with more reptile species associated with stump holes and more bird species associated with gopher tortoise burrows. Reptile, amphibian, bird, and small mammal occupancy was similar between stump holes and tortoise burrows and among stumps of varying decay states. Our research underscores the collective importance of tortoise burrows and stump holes as refugia and foraging sites for wildlife in the longleaf pine ecosystem. Additionally, our study demonstrates the importance of developing best management practices for stump removal such as retaining a proportion of stumps of different decay classes.
... Cat hunting strategies vary with prey type [62], with the mobile strategy likely to be most effective for small birds or reptiles, and the ambush strategy employed for fossorial prey, e.g. near rabbit warrens [55] and greater bilby (Macrotis lagotis (Reid)) burrows [63,64]. Although cats often hunt in open habitat, they can climb trees to target a suite of arboreal prey [65,66], and are small enough to enter rock crevices and burrows/warrens, to prey upon animals where they take refuge. ...
Article
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Introduction of the domestic cat and red fox has devastated Australian native fauna. We synthesized Australian diet analyses to identify traits of prey species in cat, fox and dingo diets, which prey were more frequent or distinctive to the diet of each predator, and quantified dietary overlap. Nearly half (45%) of all Australian terrestrial mammal, bird and reptile species occurred in the diets of one or more predators. Cat and dingo diets overlapped least (0.64 ± 0.27, n = 24 location/time points) and cat diet changed little over 55 years of study. Cats were more likely to have eaten birds, reptiles and small mammals than foxes or dingoes. Dingo diet remained constant over 53 years and constituted the largest mammal, bird and reptile prey species, including more macropods/potoroids, wombats, monotremes and bandicoots/bilbies than cats or foxes. Fox diet had greater overlap with both cats (0.79 ± 0.20, n = 37) and dingoes (0.73 ± 0.21, n = 42), fewer distinctive items (plant material, possums/gliders) and significant spatial and temporal heterogeneity over 69 years, suggesting the opportunity for prey switching (especially of mammal prey) to mitigate competition. Our study reinforced concerns about mesopredator impacts upon scarce/threatened species and the need to control foxes and cats for fauna conservation. However, extensive dietary overlap and opportunism, as well as low incidence of mesopredators in dingo diets, precluded resolution of the debate about possible dingo suppression of foxes and cats.
... This integration is carried out by symbiosis, i.e., interspecific relations (synoikia, commensalism, mutualism, parasitism, and others) between the host and its cohabitants (Savinov 2011). However, the study of commensals was carried out in a few animals (Hackman 1963;Platt et al. 2004;Pike and Grosse 2006;Read et al. 2008;Pike and Mitchell 2013;Thornett et al. 2016;Hofstede and Dziminski 2017;Brunke and Buffam 2018;Dawson et al. 2019), due to the incredible complexity of their detection. ...
Article
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Stepanova I, Andreychev A, Kulakhmetov R, Lobachev E. 2021. Commensals of underground mammals: European mole (Talpa europaea, Eulipotyphla, Talpidae) and the greater mole-rat (Spalax microphthalmus, Rodentia, Spalacidae). Biodiversitas 22: 4665-4670. The study of lodgers of burrows of underground mammals was carried out using the method of hunting cylinders (cans). In the study, 29 different representatives from the following classes were identified in the courses of the greater mole-rat and European mole: Diplopoda, Chilopoda, Gastropoda, Insecta, Amphibia, and Mammalia. Among the vertebrates captured are Eurasian common shrew (Sorex araneus), Eurasian pygmy shrew (Sorex minutus), bank vole (Clethrionomys glareolus), common spadefoot toad (Pelobates fuscus), moor frog (Rana arvalis), and common toad (Bufo bufo). Twenty-six different species have been identified among invertebrates. Many animals seek shelter in the burrows of underground mammals from enemies and adverse climatic factors for food or conditions for reproduction. In the central part of Russia, more species of commensals were found in European mole burrows (29) than in greater mole-rat burrows (21).
... As ecosystem engineers (sensu Jones, Lawton & Shachak 1994), digging mammals influence geomorphological processes (Butler 1995) and soil resources, creating shelter for other animals (e.g. Whittington -Jones, Bernard & Parker 2011;Dawson et al. 2019) and affecting vegetation and soil biota (Davidson, Detling & Brown 2012;Fleming et al. 2014). However, due to complex interactions between the digging species, habitat and soil characteristics, and the extent and longevity of the burrows or warrens, the effects of digging mammals on soil and vegetation properties vary (Mallen-Cooper, Nakagawa & Eldridge 2019). ...
Technical Report
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The use of conservation translocations to reinstate the ecosystem functions of digging and burrowing mammals is becoming more common. However, in an increasingly altered world, the roles of translocated populations, and their importance for other species, may be different. Boodies (Bettongia lesueur), a commonly translocated species in Australia, construct extensive warrens, but how their warrens affect soil properties and vegetation communities is unknown. We investigated soil properties, vegetation communities and novel ecosystem elements (specifically non-native flora and fauna) on boodie warrens at three translocation sites widely distributed across the species’ former range. Our results suggest that translocated boodie populations may be benefiting both native and non-native flora and fauna. Translocated boodies, through the construction of their warrens, substantially alter the sites where they are released, but this does not always reflect their historic ecosystem roles.
... As ecosystem engineers (sensu Jones et al., 1994), digging mammals influence geomorphological processes (Butler, 1995) and soil resources, creating shelter for other animals (e.g., Dawson et al., 2019;Whittington-Jones et al., 2011) and affecting vegetation and soil biota (Davidson et al., 2012;Fleming et al., 2014). However, due to complex interactions between the digging species, habitat and soil characteristics, and the extent and longevity of the burrows or warrens, the effects of digging mammals on soil and vegetation properties vary (Mallen-Cooper et al., 2019). ...
Article
Full-text available
Digging and burrowing mammals modify soil resources, creating shelter for other animals and influencing vegetation and soil biota. The use of conservation trans-locations to reinstate the ecosystem functions of digging and burrowing mammals is becoming more common. However, in an increasingly altered world, the roles of translocated populations, and their importance for other species, may be different. Boodies (Bettongia lesueur), a commonly translocated species in Australia, construct extensive warrens, but how their warrens affect soil properties and vegetation communities is unknown. We investigated soil properties, vegetation communities, and novel ecosystem elements (specifically non-native flora and fauna) on boodie war-rens at three translocation sites widely distributed across the species' former range. We found that soil moisture and most soil nutrients were higher, and soil compaction was lower, on warrens in all sites and habitat types. In contrast, there were few substantial changes to vegetation species richness, cover, composition, or productivity. In one habitat type, the cover of shrubs less than 1 m tall was greater on warrens than control plots. At the two sites where non-native plants were present, their cover was greater, and they were more commonly found on boodie warrens compared to control plots. Fourteen species of native mammals and reptiles were recorded using the warrens, but, where they occurred, the scat of the non-native rabbit (Oryctolagus cuniculus) was also more abundant on the warrens. Together, our results suggest that translocated boodie populations may be benefiting both native and non-native flora and fauna. Translocated boodies, through the construction of their warrens, substantially alter the sites where they are released, but this does not always reflect their historic ecosystem roles.
... As fire approaches, they run away or move through tunnels. Those sleeping or hibernating in burrows are protected from direct fire effects (Dawson et al., 2019), but when they return to the burned surface, exhausted by long fasting, they may die because of forced changes in the diet composition or higher predation pressure. In fire-prone environments, some species have developed peculiar traits or behaviours to resist fire and/or survive on inhospitable post-fire landscapes (Fig. 3). ...
Article
Fire has always been a driving factor of life on Earth. Now that mankind has definitely joined the other environmental forces in shaping the planet, lots of species are threatened by human-induced variation in fire regimes. Soil-dwelling organisms, i.e., those organisms that primarily live in soil, suffer the numerous and different consequences of fire occurrence that are, however, often overlooked compared to those on vegetation and wildlife. Most of these organisms live in the uppermost soil layer, where fire-imposed temperatures on the ground are the highest insofar as they are lethal or dangerously upset natural habitats. This contribution is a reasoned collation of findings from a number of works conducted worldwide that aims to gain insight into the immediate and longer-term impacts of single or repeated wild or prescribed fires on one group of soil-dwelling organisms or more. In fire-prone ecosystems, fire is a controlling factor of soil biota biodiversity and activity, but also where it is infrequent its ecological footprint can be substantial and lasting. Generally, the immediate fire impact on soil biota is strictly related to the peak temperatures reached on the ground and their duration, and on a set of soil properties and water content. Vertebrates can escape overheating death by running away, searching for wet niches or burrowing deep into soil. Invertebrates and microorganisms, which have little or no mobility, succumb more easily to fire, but make up for this intrinsic vulnerability thanks to their greater fecundity at the population level. Fire or burn severity, which can generally be defined as loss of organic matter aboveground and belowground, is the key factor of the indirect fire effects on soil-dwelling biota; whereas controlled burns do not often imply any substantial and lasting shift from the original situation, extreme and vast wildfires can have major consequences that may be severer than direct killing. In fact lairs are devastated, nutrient pools are heavily affected, food webs are upset, soil temperature and moisture regimes change, and toxic pyrogenic compounds remain in soil. All types of organisms can recolonise the burned area from their sanctuaries, provided that land use does not change, e.g., to pastures or arable fields, and prompt enough vegetation re-sprouting and/or encroachment prevent substantial soil erosion. Each major taxon has genera or species with useful traits and behaviours to resist fire or to recover from its unwelcome environmental legacy sooner than others. If burned soil does not undergo other fires that occur too closely together for the typical fire regime of that particular area, most of its living components are generally capable of returning to pre-fire levels in times that depend on a series of factors, such as fire severity and post-fire rainfall.
... Once found across 70% of the Australian mainland, the bilby is now restricted to ,20% of its former range (Southgate 1990a), and listed as vulnerable at the national level. Bilbies are ecosystem engineers, constructing large burrows, that provide habitat for a range of mammals, birds and reptiles (Dawson et al. 2019a). The broad historical range of bilbies, and the varied biomes they have occupied, suggest a flexible dietary strategy. ...
Article
Full-text available
ContextEcologists need robust and effective methods to quantify the diet of animals. However, assessing dietary composition can be challenging because most animals are seldom observed eating, especially when studying rare or cryptic species. AimsMorphological analysis of scats has been extensively used previously, and recent advances in the accessibility of DNA barcoding techniques have also made molecular approaches a viable alternative for diet analysis from scats. We compared the results from two methods of scat analysis, to trial the use of contemporary approaches in scat analysis. Methods In the present study, we used morphological analysis and DNA barcoding of matter in scats to catalogue the diet of a generalist omnivore, the greater bilby (Macrotis lagotis Thylacomyidae), in the West Kimberley. The composition and diversity of diet items, as well as the taxonomic identification level, were compared between methods. Key resultsEach method provided complimentary results; morphological analysis uncovered the type of matter consumed (e.g. root, seed) and relative proportion of the total undigested content, whereas DNA barcoding could assign such matter to a taxon. Even though dietary DNA could be extracted from only 38% of scats, DNA barcoding identified a greater diversity of taxa in scats than did morphological analyses. Barcoding could detect the presence of highly-digestible items such as cossid moths (Cossidae) and spiders (Araneae). Conclusions Morphological analysis was useful for quantifying relative abundance of diet categories; however, DNA barcoding detected a greater diversity of dietary items within scats. Despite the expense of DNA barcoding, the method can more accurately identify the taxa consumed, whereas morphology can greatly underestimate dietary species diversity. However, the technical requirements for performing DNA analysis make it expensive, while resource-limited field ecologists can generally perform morphological analysis with appropriate training. ImplicationsResearchers and land managers will benefit from using both approaches in concert to gain a robust understanding of the local bilby diet. However, the cost and limitations of DNA barcoding (particularly when dealing with degraded DNA) mean that this approach should only be employed when the quality of the genetic material within samples is suitable. We recommend conducting exploratory analysis using morphological analysis (potentially in the field), with follow-up DNA barcoding to detect highly digestible items in fresh scats.
... The threshold for two consecutive detections of the same species at same site to be considered independent records was 1 h, leaving a total of 802 independent vertebrate records. To avoid the use of subjective interpretation of behaviors from photographs, and for comparative purposes, we categorized records combining spatial (Dawson et al., 2019) and temporal (Desbiez & Kluyber, 2013) thresholds based on continuous photographs. We categorized all captures into one of three categories: (1) any animal caught passing on camera but not within the target area (i.e., burrow or spoil pile) was classified as 'passing', (2) an 'interaction' occurred when the animal occupied the target area for less than 5 s and (3) we considered 'use' when the animal spent over 5 s within the burrow or spoil pile area. ...
Article
Burrowing species can be considered important ecosystem engineers that increase landscape heterogeneity, create subterranean shelters and provide foraging opportunities. We measured and described different aspects of giant armadillo (Priodontes maximus) excavations (size, age), and differences generated in relation to the surrounding environment (vegetation, humidity, temperature) in three sites of the Argentine Chaco Region. We used camera‐traps in two protected areas to monitor the use of burrows by other species and tested two primary and non‐mutually exclusive hypotheses: Giant armadillo burrows are used as thermal protection from temperature extremes and provide new foraging opportunities for other species. Greater litter cover and depth were recorded in giant armadillo burrows, and more bare ground in spoil piles, producing habitat heterogeneity. Burrows had higher humidity and more moderate temperatures, with lower temperatures during hot months and higher temperatures during cold months. Out of 48 vertebrate species recorded by camera‐traps, 27 taxa (17 mammals, 9 birds and one reptile) were recorded using burrows. White‐lipped peccaries (Tayassu peccari) and collared peccaries (Pecari tajacu) used burrows more frequently than other mammals. Medium‐sized carnivores such as Pampas fox (Lycalopex gymnocercus) and Geoffroy´s cat (Leopardus geoffroyii) tended to only investigate burrows, probably searching for prey. In no instances, animals other than giant armadillos were recorded staying inside burrows for more than a few seconds. Medium‐sized species interacted more frequently than large‐sized species, and smaller species used giant armadillo burrows less than larger ones, suggesting that the benefits provided by excavations to other species depend on their body weight. The probability of use of burrows decreases with time, suggesting that burrows provide a finite resource used opportunistically. Further reduction in the distribution of the giant armadillo is therefore likely to have effects on habitat heterogeneity and biodiversity, probably impacting the fitness of species that use their burrows as foraging sources. We described giant armadillo (Priodontes maximus) excavations and differences generated in relation to the surrounding environment in the Argentina Chaco Region. We tested two hypotheses, that giant armadillo burrows are used as thermal protection from temperature extremes, and that they provide new foraging opportunities for other species. Giant armadillo excavations alter vegetation, contributing to habitat heterogeneity. Their burrows present higher humidity, more moderate temperatures, and provide foraging opportunities for other species. Further reduction in the distribution of the giant armadillo is therefore likely to have effects on biodiversity, probably impacting the fitness of species that use their burrows as foraging sites.
... Dens and den systems (named "setts") are important refuge to protect vertebrate species from predation (mostly on cubs) and as a buffer against extreme temperatures (Kinlaw, 1999;Roper et al., 2001;Monetti et al., 2005;Mukherjee et al., 2017aMukherjee et al., , 2017bDawson et al., 2019), allowing a safe and successful reproduction (Butler and Roper, 1996;Mori et al., 2016;Mukherjee et al., 2018). Primary excavators directly dig burrows and include both strictly fossorial species (e.g. ...
Article
Positive interspecific interactions in animal communities (i.e. den sharing) have long been overlooked in animal ecology. The assessment of spatiotemporal overlap among species living within the same burrow system is paramount to explain their strategies of interspecific coexistence. We studied spatiotemporal behavioural patterns of coexistence among four den-sharing mammal species (i.e. the crested porcupine Hystrix cristata, the Eurasian badger Meles meles, the red fox Vulpes vulpes and the European pine marten Martes martes), inhabiting a hilly area of central Italy. Intensive camera trapping (September 2015-September 2018) was used to estimate the interspecific overlap of both temporal and spatial activity patterns for all species combinations. An extensive nocturnal temporal overlap was recorded among all the species, except the diurnal pine marten. However, crested porcupines were mostly active in the darkest nights, whereas bright moonlight enhanced the hunting success of the red fox. Activity of badgers was limited in bright nights only during cold months, when predation pressure and poaching risk were the highest. Crested porcupines avoided spatial sharing outside the den with both nocturnal carnivores, particularly during the winter, when its cubs are in the den. Overlap in ranging areas and activity rhythms between the red fox and the Eurasian badger may be promoted by a remarkable food niche partitioning. Conversely, spatiotemporal overlap between red foxes and pine martens suggested a significant interspecific spatial partitioning, due to the overlap in feeding habits. Den-sharing represents a form of positive interspecific interaction which may limit energy waste and increase local species diversity and densities. Species using the same burrow system may show both spatial and temporal niche partitioning throughout the year, thus allowing a non-competitive coexistence.
Thesis
The grassy woodlands of eastern Australia have declined in their range by more than 95% through clearing and fragmentation. This decline has coincided with the loss of many digging or soil-foraging species that are considered to be 'ecosystem engineers' because of their role in biopedturbation and effects on other species and processes. Ecosystem engineers are therefore a priority for reintroduction to restore biodiversity and ecosystem function. However, there are gaps in our knowledge of how digging animals affect their environment and potential impacts on recipient ecosystems. The aim of this thesis was to examine the impact of the eastern bettong (Bettongia gaimardi) on ecosystem processes, following their reintroduction to a fenced reserve. It consists of five chapters that explore different aspects of this topic and the implications for management and conservation. Chapter 2 examines biodiversity patterns as a backdrop to bettong reintroduction in a BoxGum grassy woodland. We found that beetle assemblages differed in their composition among distinct ground-layer plant communities at log and tree microhabitats, while beetle communities in open microhabitats were more uniform. Sites with evidence of prior agricultural use also had altered beetle communities. These findings demonstrate the fine-scale structure of the grassy woodland ecosystem as a mosaic of plant and insect communities. Chapter 3 investigates the structural and abiotic effects of bettong and rabbit foraging pits. I found that bettong pits filled in faster than rabbit pits due to their deeper and narrower shape. I did not find any consistent effect on soil nutrients in foraging pits, unlike similar studies in arid areas. Bettong pits reduced daily temperature fluctuations compared to the soil surface. I therefore concluded that in mesic environments, the structural effects of digging may be more important than changes in soil nutrients. Chapter 4 tests the hypothesis that bettong foraging pits provide favourable conditions for seed germination compared to the soil surface. I found that seedling abundance was almost doubled in pits compared to the soil surface. Responses differed between species and years, with native species responding more strongly to the presence of pits than exotic species in the first year. The response was also stronger in denser grassland, suggesting that the driving mechanism for the increased germination is the creation of gaps and reduced competition from the grass canopy. Chapter 5 examines the impact of bettongs on a native geophyte, the early nancy (Wurmbea dioica). I found that bettongs consumed 13-24% of the plants that emerged each year, resulting in a decline in the Wurmbea population over 5 years. However, there was a shift in the population demographics toward younger plants, which may suggest that bettong digging increased recruitment and a possible feedback mechanism. Similar interactions between digging animals and geophytes have been described internationally, but this is the first study in Australia. Finally, Chapter 6 synthesises research on soil-disturbing ecosystem engineers in Australia. I argue that the goals of species reintroductions are often poorly defined, leading to missed opportunities for research and potential negative outcomes. I discuss the factors that should be considered when reintroducing ecosystem engineers and provide a framework for clarifying the goals of species reintroductions. The outcomes of my research suggest that reintroducing extirpated ecosystem engineers may contribute to restoration of grassy woodlands, but they may also have unexpected consequences. Translocations should therefore consider both trophic and engineering effects and be prepared to monitor and manage unexpected outcomes. These findings will inform management of sanctuaries and translocations and contribute to restoration efforts in grassy woodlands in Australia and worldwide.
Article
Abstract Ecosystem engineers strongly influence the communities in which they live by modifying habitats and altering resource availability. These biogenic changes can persist beyond the presence of the engineer, and such modifications are known as ecosystem engineering legacy effects. Although many authors recognize ecosystem engineering legacies, and some case studies quantify the effects of legacies, few general frameworks describe their causes and consequences across species or ecosystem types. Here, we synthesize evidence for ecosystem engineering legacies and describe how consideration of key traits of engineers improves understanding of which engineers are likely to leave persistent biogenic modifications. Our review demonstrates that engineering legacies are ubiquitous, with substantial effects on individuals, communities, and ecosystem processes. Attributes that may promote the persistence of influential legacies relate to an engineer's traits, including its body size, lifespan, and living strategy (individual, conspecific group, or collection of multiple co‐occurring species). Additional lines of inquiry, such as how the recipients respond (e.g., density or richness) or the mechanism of engineering (e.g., burrowing or structure building), should be included in future ecosystem engineering legacy research. Understanding patterns of these persistent effects of ecosystem engineers and evaluating the consequences of losing them is an important area of research needed for understanding long‐term ecological responses to global change and biodiversity loss.
Article
Introduced predators are one of the leading causes of decline in island vertebrates. Understanding how they hunt and kill threatened prey can help improve management activities. Although broadscale features are known to influence predator movement patterns, factors influencing fine scale movement are often overlooked. In particular, the influence of prey cues and microhabitat features has received little attention despite predators spending considerable time hunting prey using a range of visual, olfactory and auditory cues. Using feral cats as a case study, we used video and GPS collars combined with ground-truthing to determine if predators use fine-scale prey cues or microhabitat features to hunt in an arid environment. Feral cat activity was comprised of continuous traverses interspersed with periods of stationary activity (GPS clusters) generally less than 40 minutes in duration. Video collars confirmed that these clusters included the majority of stalk and pounce hunting bouts. Stationary activity was significantly focussed on prominent prey cues such as burrows, foraging digs or warrens of mammalian prey including both exotic (rabbits) and threatened native species (rodents, bilbies and bettongs). Evidence of prey kills was higher at cluster sites. Cats spent significantly more time at microsites with high vegetation cover including single trees, suggesting that they use prominent prey cues and patches of thick cover to increase their probability of encountering prey and/or to conceal themselves during hunting or feeding activity. Results suggest prey species with conspicuous cues are at higher risk of predation and this vulnerability could increase over time as resident cats learn to identify the location of prey cues within their home range. Conversely, removing resident knowledgeable predators may reduce predation rates if immigrating predators take time to learn to locate prey cues in their new environment. We urge researchers to investigate fine-scale drivers of movement patterns as this information is likely to be critical for long term management of predator species.
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The taxonomic identity and status of the Australian Dingo has been unsettled and controversial since its initial description in 1792. Since that time it has been referred to by various names including Canis dingo, Canis lupus dingo, Canis familiaris and Canis familiaris dingo. Of these names C. l. dingo and C. f. dingo have been most often used, but it has recently been proposed that the Australian Dingo should be once again recognized as a full species—Canis dingo. There is an urgent need to address the instability of the names referring to the Dingo because of the consequences for management and policy. Therefore, the objective of this study was to assess the morphological, genetic, ecological and biological data to determine the taxonomic relationships of the Dingo with the aim of confirming the correct scientific name. The recent proposal for Canis dingo as the most appropriate name is not sustainable under zoological nomenclature protocols nor based on the genetic and morphological evidence. Instead we proffer the name C. familiaris for all free-ranging dogs, regardless of breed and location throughout the world, including the Australian Dingo. The suggested nomenclature also provides a framework for managing free-ranging dogs including Dingoes, under Australian legislation and policy. The broad principles of nomenclature we discuss here apply to all free-roaming dogs that coexist with their hybrids, including the New Guinea Singing Dog.
Thesis
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Arid Recovery, a fenced reserve free of feral predators in arid South Australia, has successfully reintroduced two critical weight range (CWR) mammals, greater bilbies (Macrotis lagotis) and burrowing bettongs (Bettongia lesueur) to facilitate the restoration of arid Australian ecosystems. This thesis evaluates the ecological roles of these reintroduced species and their relationship to ecosystem functioning and the restoration of these ecosystems. Surveys of foraging diggings and soil seed banks, and dietary analysis were used to measure impacts of these species on three main habitats within the Reserve. The results showed that bilbies and bettongs have three major roles in ecosystem functioning: consumers, ecosystem engineers, and dispersers of seeds and fungi. Both bilbies and bettongs were omnivorous, though their diets were distinctly different, with the bilbies focused more on invertebrates and seeds, while the bettongs consumed a greater proportion of coarser plant materials. The seed portion of the diets of both species during 2003-04 differed from a similar study three years previously, shortly after the animals had been reintroduced to Arid Recovery in 2000- 01. During 2003-04, the bilbies consumed a lower proportion of seeds of species of grasses and more of forbs, while seed consumption by bettongs narrowed to be almost exclusively the seeds of shrubs. The number of bilby and bettong diggings varied significantly both spatially and temporally, with averages of 7,530 ± 820 diggings ha-1 in Dunes, 10,560 ± 980 diggings ha-1 in Mulga, and 7,120 ± 610 diggings ha-1 in Swale. This resulted in an average of 2 to 3% disturbance of soil surface area, which is similar to or higher than reported for other Australian or overseas semi-fossorial species. The temporal variation in rates of digging was correlated with minimum daily temperatures and rainfall but not moonlight. This variation was also correlated with counts of bilby but not bettong tracks, suggesting that the temporal variability of diggings was related to levels of bilby activity. The persistence of bilby and bettong diggings differed between the three habitat types, with the majority of the diggings in the Mulga (94%) and Swale (87%) persisting for over 12 months, while Dune diggings filled much faster, with only 15% persisting over 12 months. These diggings were shown to accumulate and bury seeds and litter, and, under some conditions, enhance germination. The seeds of two plant species, the annual grass, Dactyloctenium radulans, and the shrub, Enchylaena tomentosa, germinated from bilby faecal pellets, and over a third of bilby faecal pellets contained fungal spores. Therefore bilbies have the potential to be dispersers of both seeds and fungi. All three major roles of the bilbies and bettongs in ecosystem functioning (consumers, ecosystem engineers, and dispersers of seeds and fungi) have the potential to affect the flows of organic, soil and water resources, and therefore vegetation structure and overall productivity. Soil seed bank densities differed between areas with and without bilbies and bettongs. However, the heterogeneity of the system made it difficult to confidently relate these differences to any particular effects of the bilbies and bettongs. Both bilbies and bettongs were able to locate and dig seeds buried 20 cm deep, and the caches of seed-harvester ants. Experiments showed that in areas of high digging density, 71 to 94% of seed rain accumulated and became buried in diggings. Since bilbies and bettongs have the potential to use buried seed resources, they have the potential to significantly affect soil seed banks through their consumption of seeds, redistribution of seeds through their digging activities and their interactions with other granivorous species. This study is a first step towards understanding the roles of reintroducing CWR mammals to arid ecosystems. Possible longer term effects of these reintroductions will depend on suitable regulation of animal numbers, and climatic patterns, as restorative effects of diggings would be greatest during periods of good rainfall, whereas droughts would slow restorative processes. Although the results of this research are unique for Arid Recovery, the principles of evaluating all major ecological roles of reintroduced species and their interactions with their environment could provide guidance for other reintroductions. These interactions are complex and would require longer-term studies over a range of conditions and locations to further understand the role of reintroducing CWR mammals to ecological restoration.
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Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ(15)N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra.
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The Boodie or Burrowing Bettong Bettongia lesueur became extinct on the Australian mainland by about 1960 but, in some areas, left evidence of its previous distribution in the form of relict landscape features, which remain widespread in arid areas with hard soils. We recorded the location of landscape features ('mounds'), which we attributed to B. lesueur, in the western deserts during the 1980s and 1990s. There were two types of mounds - large, irregular shaped mounds of calcrete or clayey soils that were accumulated spoil from warren digging and smaller, regular, and largely circular mounds on lateritic surfaces. We mapped mounds, which are visible as obvious features in an otherwise often monotonous landscape, during vehicular traverses of desert tracks over a 10-15 year period. Mound density along one 215 km traverse in the northern Gibson Desert was 5.9±0.96 km-2. We measured attributes of both types of mound in the Gibson Desert. The former persist as warrens (often occupied by Rabbits Oryctolagus cuniculus), have many entrances, are often large in aerial extent, and often associated with rock capping. The latter are largely symmetrical mounds, smaller (typically < 20 m in diameter), and with soil penetrability typically far greater than surrounding soil that often has a hard pan.
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Concern over the status of species associated with prairie dog colonies has increased with the recent proposed listing of black-tailed prairie dogs (Cynomys ludovicianus). We monitored burrowing owl (Athene cunicularia) populations and prairie dog densities in 17 black-tailed prairie dog colonies in the Nebraska panhandle between 1990 and 1996. All prairie dog colonies were controlled at least once during the study. We observed a 63% decline in nesting pairs of burrowing owls and significant declines in burrow densities. Results indicated a time lag in owl response to changes in active burrow densities. However, in the later years of the study when burrow densities were lowest, owl numbers were positively correlated with the density of active burrows in the same years, indicating active burrows may become more important as burrow density declines. We also monitored fledging success of burrowing owls for 398 nesting attempts over 5 years (1989-93) for a larger set of colonies that included the 17 used in the owl and prairie dog monitoring. Differences in mean fledging success among colonies each year (colony effect) explained most of the variation in fledging success among nesting owls. Vulnerability to badger (Taxidea taxus) predation may in part explain differences in fledging success among colonies; badger predation on owl nests was lower when densities of active prairie dog burrows were high. Efforts are needed to ensure preservation of black-tailed prairie dog colonies for burrowing owls and other species associated with this prairie ecosystem, and to better monitor changes in burrowing owl and prairie dog populations.
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Through their excavations, giant armadillos (Priodontes maximus) alter their physical surroundings and create new habitats, which influence resources for at least 24 other species of vertebrates in the Brazilian Pantanal. The role of this poorly known species as an ecosystem engineer may be of high value to the community of vertebrates.
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Many mammals, both potential competitors and preys, have been reported to use the complex burrow system of European badger Meles meles setts as shelter, mainly in northern Europe and during winter, when badgers are lethar-gic. Nonetheless, until recent times observations of den shar-ing have been largely restricted to anecdotal information, because of the mainly nocturnal activity of most sett occu-pants. Using camera-trapping, we investigated both the mam-mal fauna associated with 24 badger setts located in northern and central Italy, and seasonal variation in the composition of specific assemblages, without interfering with the occupants' activity. Trapping effort was 1,605 camera trap-days from December 2010 to December 2013. Badgers (two to six individuals per sett) shared their setts with a total of eight mammal species: crested porcupine Hystrix cristata, Eastern cottontail Sylvilagus floridanus, red fox Vulpes vulpes, pine marten Martes martes, stone marten Martes foina, wood mouse Apodemus sp., brown rat Rattus norvegicus and coypu Myocastor coypus. Den sharing was observed throughout the year, with a significant reduction of sharing during winter, when badgers were probably induced to move to alternative setts to avoid breeding porcupines. Eastern cottontails used badger burrows permanently and, at least in one occasion, reared their pups inside, although they can be easily preyed upon by badgers. Badger sett sharing may have favoured both the recent northward expansion of crested porcupines and settling of introduced cottontails in agricultural habitats.
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Forest areas restored after mining typically take decades, or longer, before they resemble the original vegetation community. Understanding how fauna succession varies with plant succession requires detailed knowledge of an animal’s ecology. Knowledge of an animal’s ecology can also be used to predict faunal responses to management manipulations and enable techniques to be developed that accelerate the return of fauna to restored sites. We radio-tracked western bearded dragons (Pogona minor) in a mix of unmined forest sites and sites restored after bauxite mining, in the jarrah forest of south-west Western Australia, to determine critical resources and important microhabitats for dragons. Dragons were generalists – utilising a range of microhabitats – and adaptable, adjusting their microhabitat use depending on availability. Individuals also differed significantly in their microhabitat use and did not appear to have a defined home range. We concluded that the species would rapidly recolonise restored sites and that no modifications to current restoration practices were required to accelerate their return. Prescribed burning of restored areas could negatively affect this species but the effect would be short-term (<2 years). The approach used in this study could be used to develop management prescriptions that accelerate the return of late-successional species to restored sites.
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A comprehensive, but simple-to-use software package for executing a range of standard numerical analysis and operations used in quantitative paleontology has been developed. The program, called PAST (PAleontological STatistics), runs on standard Windows computers and is available free of charge. PAST integrates spreadsheettype data entry with univariate and multivariate statistics, curve fitting, time-series analysis, data plotting, and simple phylogenetic analysis. Many of the functions are specific to paleontology and ecology, and these functions are not found in standard, more extensive, statistical packages. PAST also includes fourteen case studies (data files and exercises) illustrating use of the program for paleontological problems, making it a complete educational package for courses in quantitative methods.
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Despite once being described as common, digging mammal species have been lost from the Australian landscape over the last 200 years. Around half of digging mammal species are now extinct or under conservation threat, and the majority of extant species have undergone marked range contractions.Our aim is to identify the role of digging mammals in ecosystem processes throughout Australia. We highlight how the actions of digging mammals are vital for maintaining ecosystem functioning and how their extirpation has led to loss of ecosystem functions.A review of the literature indicates that many aspects of the influence of bioturbation on ecosystem functioning have been studied. The role of digging mammals in arid and semi-arid zones has been previously established. We collate and review a broader scope of studies, including those carried out in the mesic woodlands and forests of Australia. We identify roles of digging mammals in the context of ecosystem functioning and conservation management.Bioturbation significantly alters soil processes, increasing soil turnover and altering the chemical and structural properties of soil. Greater water infiltration and decreased surface run-off and erosion alter soil hydrophobicity and increase soil moisture. Diggings capture organic matter, provide habitat for a diversity of microscopic and macroscopic organisms, and increase nutrient cycling. Mycophagous mammals disperse fungi (e.g. mycorrhizae), while all diggings can create suitable sites for fungal growth. Diggings also capture plant seeds, increasing seedling germination, recruitment and plant growth. The overall effect of mammal diggings is therefore increased plant vigour and resilience, increased biodiversity and consequently improved ecosystem functioning.We propose that the loss of digging mammals has contributed to the deterioration of ecosystems in Australia. Recognising the roles of digging mammals will inform potential management options such as species translocations or reintroductions.
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Modern African elephants affect habitats and ecosystems in significant ways. They push over trees to feed on upper branches and often peel large sections of bark to eat. These destructive habits sometimes transform woody vegetation into grasslands. Systems of elephant trails may be used and re-used for centuries, and create incised features that extend for many kilometers on migration routes. Elephants, digging in search of water or mineral sediments, may remove several cubic meters of sediments in each excavation. Wallowing elephants may remove up to a cubic meter of pond sediments each time they visit water sources. Accumulations of elephant dung on frequented land surfaces may be over 2kg per square meter. Elephant trampling, digging, and dust-bathing may reverse stratigraphy at archeological localities. This paper summarizes these types of effects on biotic, geomorphic, and paleontological features in modern-day landscapes, and also describes several fossil sites that indicate extinct proboscideans had very similar effects, such as major sediment disturbances.
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Nine bilbies were reintroduced to a 14-km2 reserve free of rabbits, cats and foxes in South Australia in April 2000. The survival, growth and ecology of the population were studied for 17 months after release by means of radio-tracking and trapping. Reproduction was continuous over the study period, with juveniles successfully recruited into the population. Home-range size of female bilbies averaged 0.18 km2 and was significantly smaller than home ranges of males, which averaged 3.16 km2. Wild-born subadults had smaller home ranges than adults. While male home ranges, and male and female home ranges overlapped considerably, females appeared to maintain areas discrete from other adult females. Bilbies showed a significant preference for dune habitat. As swale habitat appears too hard for burrow construction and males moved greater distances from diurnal burrows than females, males are likely to access food reserves that are under-used by females. Both males and females reused at least 30% of their burrows, and females displayed long-term site fidelity. The release was considered successful and suggests that despite historical damage from rabbits and stock, bilbies are able to successfully recolonise parts of their former range in arid South Australia once rabbits, cats and foxes are removed.
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El desierto Mojave es uno de los más secos y calientes en Norteamérica. Se pensaría que los pájaros que viven en este desierto son especialistas adaptados para soportar ese ambiente. Sin embargo, la mayoría de la avifauna del desierto Mojave tiene una distribución geográfica que se extiende a regiones más frescas y húmedas. Reportamos observaciones de alondras cornudas (Eremophila alpestris) usando madrigueras de tortugas del desierto (Gopherus agassizii) durante el verano como refugio de las temperaturas altas en la superficie del suelo. Enseñamos que las alondras cornudas parecen discriminatorias del micro-ambiente que escogen, y que las madrigueras son los sitios más frescos y húmedos disponibles. Al utilizar las madrigueras de las tortugas del desierto, las alondras cornudas pueden reducir la pérdida evaporatoria del agua hasta 65%, y pueden evitar estrés fisiológico, o potencialmente la muerte. Investigación adicional debe evaluar la importancia de las madrigueras de las tortugas del desierto para otras especies porque es probable que provean un micro-hábitat a muchas especies que habitan en el desierto Mojave.
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Many small mammal species experience population declines following prescribed fire, presumably resulting from increased predation due to lack of cover. However, Peromyscus gossypinus (Cotton Mouse) typically shows a neutral or positive population response following fire. Because they typically spend diurnal hours in below-ground refuges, Cotton Mice may be less susceptible to predation following fire than other small mammals. We examined the effects of prescribed fire and exclusion of mammalian predators on selection of daytime refuges by Cotton Mice. We located daytime refuges of 12 radiotagged Cotton Mice in a fenced mesomammal-predator (hereafter, mesopredator) exclosure (23 refuge locations) and 9 Cotton Mice in an adjacent unfenced control plot (13 refuge locations) for one month prior to and one month after a prescribed fire in winter 2007. Refuge locations included Gopherus polyphemus (Gopher Tortoise) burrows (27.8%), other ground holes (44.4%), stump holes (25.0%), and holes at the base of trees (2.8%). Fire had little effect on refuge selection, likely because Cotton Mice primarily used below-ground refuges, which allowed them to avoid the direct effects of fire and predation following fire. Structure near the refuge, including burrows, stumps, and coarse woody debris, was important in selection of daytime refuges and was particularly important in the presence of mesopredators.
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Aims In ecology and conservation biology, the number of species counted in a biodiversity study is a key metric but is usually a biased underestimate of total species richness because many rare species are not detected. Moreover, comparing species richness among sites or samples is a statistical challenge because the observed number of species is sensitive to the number of individuals counted or the area sampled. For individual-based data, we treat a single, empirical sample of species abundances from an investigator-defined species assemblage or community as a reference point for two estimation objectives under two sampling models: estimating the expected number of species (and its unconditional variance) in a random sample of (i) a smaller number of individuals (multinomial model) or a smaller area sampled (Poisson model) and (ii) a larger number of individuals or a larger area sampled. For sample-based incidence (presence–absence) data, under a Bernoulli product model, we treat a single set of species incidence frequencies as the reference point to estimate richness for smaller and larger numbers of sampling units.
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While well-recognized as an important kind of ecological interaction, physical ecosystem engineering by organisms is diverse with varied consequences, presenting challenges for developing and using general understanding. There is also still some uncertainty as to what it is, and some skepticism that the diversity of engineering and its effects is amenable to conceptual integration and general understanding. What then, are the key cause/effect relationships and what underlies them? Here we develop, enrich and extend our extant understanding of physical ecosystem engineering into an integrated framework that exposes the essential cause/effect relationships, their underpinnings, and the interconnections that need to be understood to explain or predict engineering effects. The framework has four cause/effect relationships linking four components: 1. An engineer causes structural change; 2. Structural change causes abiotic change; 3. Structural and abiotic change cause biotic change; 4. Structural, abiotic and biotic change can feedback to the engineer. The first two relationships describe an ecosystem engineering process and abiotic dynamics, while the second two describe biotic consequence for other species and the engineer. The four relationships can be parameterized and linked using time-indexed equations that describe engineered system dynamics. After describing the relationships we discuss the utility of the framework; how it might be enriched; and briefly how it can be used to identify intersections of ecosystem engineering with fields outside ecology.
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Macrotermes mounds are a significant feature of African woodland landscape, contributing to habitat heterogeneity. The mounds are massive, often many centuries old, and support dense vegetation and a suite of woody plant species scarce in surrounding woodland. The present study tested the hypothesis that Zimbabwean Macrotermes mounds, with their greater niche availability, were more heavily utilized by small vertebrates than the surrounding miombo woodland. We carried out a survey of amphibian, reptile and mammal species during early and late rains for 16 termite mounds and 16 adjacent woodland habitat sites, and compared numbers of individuals, species and diversity. For amphibians and reptiles, individual numbers and species did not differ significantly between habitats and their activity was more influenced by season. For mammals, however, significantly more individuals and species were captured on termite mounds, with three species captured only on mounds (most notably the musk shrew Crocidura hirta spp. complex) and all others showing marked preference for this habitat. The greater number of mammals on termite mounds contributed to total small vertebrate biomass being 800 g/ha for termite mounds compared with 380 g/ha in woodland. For mammals certainly, Macrotermes mounds provide significant food and habitat in miombo woodland.
Book
The Action Plan for Australian Mammals 2012 is the first review to assess the conservation status of all Australian mammals. It complements The Action Plan for Australian Birds 2010 (Garnett et al. 2011, CSIRO Publishing), and although the number of Australian mammal taxa is marginally fewer than for birds, the proportion of endemic, extinct and threatened mammal taxa is far greater. These authoritative reviews represent an important foundation for understanding the current status, fate and future of the nature of Australia. This book considers all species and subspecies of Australian mammals, including those of external territories and territorial seas. For all the mammal taxa (about 300 species and subspecies) considered Extinct, Threatened, Near Threatened or Data Deficient, the size and trend of their population is presented along with information on geographic range and trend, and relevant biological and ecological data. The book also presents the current conservation status of each taxon under Australian legislation, what additional information is needed for managers, and the required management actions. Recovery plans, where they exist, are evaluated. The voluntary participation of more than 200 mammal experts has ensured that the conservation status and information are as accurate as possible, and allowed considerable unpublished data to be included. All accounts include maps based on the latest data from Australian state and territory agencies, from published scientific literature and other sources. The Action Plan concludes that 29 Australian mammal species have become extinct and 63 species are threatened and require urgent conservation action. However, it also shows that, where guided by sound knowledge, management capability and resourcing, and longer-term commitment, there have been some notable conservation success stories, and the conservation status of some species has greatly improved over the past few decades. The Action Plan for Australian Mammals 2012 makes a major contribution to the conservation of a wonderful legacy that is a significant part of Australia’s heritage. For such a legacy to endure, our society must be more aware of and empathetic with our distinctively Australian environment, and particularly its marvellous mammal fauna; relevant information must be readily accessible; environmental policy and law must be based on sound evidence; those with responsibility for environmental management must be aware of what priority actions they should take; the urgency for action (and consequences of inaction) must be clear; and the opportunity for hope and success must be recognised. It is in this spirit that this account is offered. Winner of a 2015 Whitley Awards Certificate of Commendation for Zoological Resource.
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There is little information on predator–prey interactions in wind energy landscapes in North America, especially among terrestrial vertebrates. Here, we evaluated how proximity to roads and wind turbines affect mesocarnivore visitation with desert tortoises (Gopherus agassizii) and their burrows in a wind energy landscape. In 2013, we placed motion-sensor cameras facing the entrances of 46 active desert tortoise burrows in a 5.2-km2 wind energy facility near Palm Springs, California, USA. Cameras recorded images of 35 species of reptiles, mammals, and birds. Counts for 4 species of mesocarnivores at desert tortoise burrows increased closer to dirt roads, and decreased closer to wind turbines. Our results suggest that anthropogenic infrastructure associated with wind energy facilities could influence the general behavior of mammalian predators and their prey. Further investigation of proximate mechanisms that underlie road and wind turbine effects (i.e., ground vibrations, sound emission, and traffic volume) and on wind energy facility spatial designs (i.e., road and wind turbine configuration) could prove useful for better understanding wildlife responses to wind energy development. © 2017 The Wildlife Society.
Article
Greater bilbies (Macrotis lagotis) have been described as ecosystem engineers and their burrows are significant structures across an often featureless and harsh arid landscape. Remote cameras were deployed at bilby burrows to determine whether bilby burrows were important structures for other species. Cameras detected two mammal species, brush-tailed mulgara (Dasycercus blythi) and spinifex hopping mice (Notomys alexis), permanently occupying bilby burrows, and a further two species, short-beaked echidnas (Tachyglossus aculeatus acanthion) and sand goannas (Varanus gouldii), regularly using bilby burrows for shelter. An additional suite of 16 mammal, bird, reptile, amphibian and invertebrate species were detected interacting with bilby burrows. There was no difference in the number of species using disused or occupied bilby burrows, indicating that even disused bilby burrows are important structures for other species. We show that bilby burrows are used by a range of species and are analogous to the traditional, mostly North American, and commonly provided text book examples of the gopher tortoise and kangaroo rat. The disappearance of bilbies across at least 80% of their former range and thus the disappearance of their burrows as important structural resources in a harsh, arid environment may have had important consequences for a range of species.
Article
Gopher Tortoise (Gopherus polyphemus) burrows are used by more than 60 vertebrate species, but the frequency with which species use burrows and the extent to which other vertebrates use the mound of sand at the burrow entrance, called the burrow apron, has not been quantitatively assessed. Between 2 June and 9 October 2014, we monitored active and inactive adult Gopher Tortoise burrows with motion-triggered trail cameras to identify and enumerate vertebrate burrow visitors. We recorded 12,238 video clips during 2299 trap nights, of which 10,151 (83%) contained a Gopher Tortoise and 1732 (14%) contained other vertebrate species. We reduced multiple videos of a single burrow visitation to 1 observation, resulting in 929 observations of 14 vertebrate species (not including the Gopher Tortoise) using tortoise burrows and 34 species on burrow aprons. Mammals were the most commonly recorded taxa (54%), followed by birds (32%), amphibians (9%), and reptiles (5%). Active burrows were visited more frequently than inactive burrows across all taxa, and burrow aprons were used more frequently than the burrow tunnel. Although active and inactive Gopher Tortoise burrows provide refuge for some vertebrate species, active burrows may provide additional resources, such as increased prey for insectivorous species. More species were found to be present on burrow aprons than within burrows, indicating the apron may be an important microhabitat for species, including those not known to use burrows.
Article
Burrows can provide refuge for both burrowing and non-burrowing species within harsh environments through protection from climatic extremes, water loss and predation. In Australia, however, despite having a rich diversity of burrowing mammals, little is known about the use of burrows by non-burrowing species. This study aimed to identify the extent of co-use of southern hairy-nosed wombat (Lasiorhinus latifrons) burrows on Wedge Island off the coast of South Australia. Burrow use was monitored using 34 motion-activated cameras placed outside wombat burrows between March and September 2015. Eleven species were found to use burrows, with six commensal species observed using burrows on numerous occasions. These included two mammal species (black-footed rock-wallaby, Petrogale lateralis pearsoni; brush-tailed bettong, Bettongia penicillata), three reptile species (peninsula dragon, Ctenophorus fionni; southern sand-skink, Liopholis multiscutata; White's skink, Liopholis whitii), and one avian species (little penguin, Eudyptula minor). The most common species observed using burrows was the black-footed rock-wallaby, which was recorded using burrows 1795 times. Observations of wombats using burrows were made 1674 times. The prevalent use of burrows on Wedge Island by species other than wombats is an observation with potentially important and broad ecological, conservation, and management implications across Australia's arid and semiarid zones.
Book
A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods. The emphasis is on presenting practical problems and full analyses of real data sets.
Article
Soil-disturbing vertebrates (SDV) are relatively low in biodiversity and biomass compared with the dominant soil fauna (microorganisms and invertebrates), but they can nevertheless have a great impact on the physical and chemical properties of soils. Our goal is to take an ichnological (organism-substrate interactions)–based approach to review the impacts of SDV on soils; these impacts result in three basic categories of physical structures (traces): subterranean excavations, constructed surficial mounds, and surficial excavations and depressions. We focus on direct rather than indirect effects and frame these in terms of soil additions, losses, translocations, and transformations. We look at publication trends in the SDV literature and graphically summarize examples of maximum reported construction heights, excavation depths, and volumes of soil displacement for various SDV. We then review SDV impacts on soil color, texture, horizonation, structure, bulk density, soil moisture, porosity and permeability, organic matter, pH, cation exchange capacity, and the nutrients Ca, Mg, N, K, P, S, and Si. Translocations are common sources of variation in these properties and may be especially important in creating nutrient-rich patches in otherwise limited landscapes. Common results of SDV activity include destruction of soil structure, decreases in bulk density, and increases in infiltration rates, porosity, and permeability. Additions of excrement and plant material are important sources of organic matter, N, and K. Direct soil losses may occur through geophagy and trampling and wallowing behaviors. Erosion is an important indirect impact often related to killing of surface vegetation from mounding and foraging behaviors.
Article
Interactions between organisms are a major determinant of the distribution and abundance of species. Ecology textbooks (e.g., Ricklefs 1984, Krebs 1985, Begon et al. 1990) summarise these important interactions as intra- and interspecific competition for abiotic and biotic resources, predation, parasitism and mutualism. Conspicuously lacking from the list of key processes in most text books is the role that many organisms play in the creation, modification and maintenance of habitats. These activities do not involve direct trophic interactions between species, but they are nevertheless important and common. The ecological literature is rich in examples of habitat modification by organisms, some of which have been extensively studied (e.g. Thayer 1979, Naiman et al. 1988).
Article
We classified burrows of a population of gopher tortoises (Gopherus polyphemus) as active, inactive or abandoned according to the physical characteristics of the entrances. We excavated 1019 burrows (454 active, 449 inactive and 116 abandoned) to determine if either tortoises (males, females and juveniles) or symbionts differentially used these three burrow categories. We captured 400 tortoises in burrows. We classified all burrows immediately prior to excavation. Tortoises were captured significantly more often in active than in either inactive or abandoned burrows. Juveniles were captured significantly more often than adults in inactive burrows only. Numerically, 53% of the symbiont individuals were reptiles, 36% were amphibians and 11% were mammals. The number of reptilian species was greater than that of both amphibians and mammals. Mammalian individuals were significantly under-represented in our sample relative to reptiles and amphibians. When all vertebrate symbionts were combined, we could detect no difference in use of the three burrow categories. Reptiles, however, were found significantly more often in active burrows. When snakes and lizards were analyzed separately, only lizards were found significantly more often in active burrows; snakes were randomly distributed in burrow categories. We present several hypotheses to account for these observed distributions.
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Twenty-two species of vertebrates have been recorded in Colorado as using pocket gopher burrows for retreats and foraging routes, and the local occurrence of several reptiles and of the tiger salamander is determined by the presence of these burrows. Adult tiger salamanders often live in burrows occupied by pocket gophers; apparently these two animals are mutually tolerant. Ground squirrels are pocket gophers' strongest competitors for burrow systems and occasionally force pocket gophers from their burrows. The plugging by pocket gophers of open entrances to their burrows is important in excluding other burrowinhabiting vetebrates as well as predators.
Article
Florida mice (Podomys floridanus) radio-tracked in xeric upland habitats in S-central Florida used gopher tortoise (Gopherus polyphemus) burrows exclusively. The mice showed no obvious preference for active, inactive or abandoned burrows and used both main entrances and small ground holes (chimneys) for access. Over periods of 2-19 days, individuals were found in from 1-5 different locations within the same burrow and used from 1-3 different burrows. Mice were typically located in side passages off the main burrow. Locations of males and females did not differ in the distance from the entrance (combined \bar{x} ± SE = 161 ± 20 cm) or depth below ground (combined \bar{x} = 68 ± 9 cm), but males were closer to the main burrow (\bar{x} = 86 ± 18 cm) than females (\bar{x} = 172 ± 24 cm). In the same study area 4 yr earlier, cotton mice (Peromyscus gossypinus) also used tortoise burrows extensively but typically occupied the main burrow instead of a side passage. This difference between the two species in site preference within gopher tortoise burrows and their apparent tolerance of joint occupancy of burrows presumably reduce interspecific competition for homesites in habitats in which Florida mice and cotton mice co-occur. The Florida mouse is more specialized behaviorally and morphologically for burrow dwelling than the cotton mouse.
Article
In harsh, resource-limited rangelands, plants and other structures, such as animal burrows, can ameliorate extreme microclimate conditions and increase resource availability for other species. The aim of this study was to determine whether relic bilby (Macrotis lagotis) refuge burrows had the potential to contribute to a rangeland restoration program by moderating microclimate and accumulating resources. During the day, the burrows maintained significantly higher relative humidity than control microsites. At night, temperature was significantly higher and humidity was significantly lower in the burrows than the control microsites. Both temperature and humidity were also significantly less variable in the burrows. There was some overlap between burrows and control microsites in soil chemistry, but burrows were significantly higher in soil moisture, pH(CaCl2), exchangeable magnesium, exchangeable potassium, mineral nitrogen, and total cation exchange capacity, and significantly lower in bio-available aluminium. Soils in burrows contained three times more mineral nitrogen, which has been previously shown to increase plant diversity and abundance in the presence of additional moisture. These results suggest the relic bilby burrows could potentially provide more suitable habitats for the establishment and productivity of other species by moderating microclimates, accumulating nutrients and soil moisture, and ameliorating the potentially detrimental effects of bio-available aluminium.
Article
The Ethiopian wolf (Canis simensis) is a rare and endangered carnivore found in only a few mountain ranges of the Ethiopian highlands. We studied its diet and feeding behavior in Bale Mountains National Park, Ethiopia, from 1988 through 1992. Observations of foraging behavior (n = 380) and scat analysis (n = 689) suggested that the Ethiopian wolf specializes in eating rodents. Rodents accounted for 96% of the prey occurrences and 97% volume in the droppings. The giant molerat (Tachyoryctes macrocephalus) was the main food item, followed in importance by three species of rats (Arvicanthis blicki, Lophuromys melanonyx, and Otomys typus). Ethiopian wolves foraged solitarily throughout the day, but occasionally small packs ( ltoreq 6) hunted hares, young antelopes, and sheep. During foodchoice experiments, wolves significantly preferred Tachyoryctes to Arvicanthis and Lophuromys, Arvicanthis to Lophuromys, and either of them to Stenocephalemys, which was invariably discarded. Lepus starcki was preferred to any of the species of rats. The contribution of different species of prey to the diet of the Ethiopian wolf correlated with abundance of prey.
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Ecosystem engineers play fundamental ecological roles by modifying habitats in ways that affect a multitude of other species and by creating refugia with novel microclimates. We hypothesize that burrow-creating organisms may facilitate climate change adaptation by providing refugia from extreme and fluctuating temperatures found aboveground. We support this hypothesis by showing that large burrow-dwelling tortoises, Gopherus polyphemus, likely depend upon burrows for thermoregulation. By exploiting the varied thermal conditions within burrows, tortoises avoided lethal temperatures and extreme fluctuations in body temperature, maintained moderate and stable body temperatures on hot days, and maintained relatively warm temperatures overnight. Climate change is predicted to increase maximum air temperatures throughout the geographic range of this species, with impacts most severe in Florida, US, where the range of future conditions could be above that of current maxima. This implies that environmental temperatures will be above lethal thermal limits more often, highlighting the importance of refugia from extreme conditions. Large burrowing animals (e.g. aardvarks, pocket gophers, rabbits, seabirds, tortoises, wombats) are widely distributed globally and could provide similar thermal refugia for countless commensal taxa. Burrows and the animals that create them are in urgent need of conservation, which will help ensure the widespread availability of refugia that offer protection from extreme temperatures under climate change.
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The pygmy blue-tongue lizard, Tiliqua adelaidensis, had been considered extinct until its recent rediscovery near Burra in the mid-north of South Australia. The lizards apparently rely on spider burrows with a single entrance as refuge sites. In this paper we describe observations from all-day video recordings of the entrances of burrows occupied by lizards on 31 days across the spring and early summer of 1996. The lizards spent most of each day either retreated down the burrow or basking at the burrow entrance. Early in the season, when temperatures were cooler, lizards spent more of each day basking, and more of their basking time fully emerged from the burrow, than later in the season. Results are consistent with the hypothesis that the lizards thermoregulate by moving in and out of the burrow. Lizards also fed by making short excursions from the burrow, often to catch passing invertebrate prey, although they also fed on flowers early in spring. Later in the season lizards were more likely to vacate their burrows for longer times, or to move away from their burrows, and mating activity was observed when males approached burrows occupied by females. The observations suggest that pygmy blue-tongue lizards rely heavily on burrows for many activities, and that any conservation management scheme for this endangered species will rely on maintaining an adequate supply of burrows.
Article
Burrows created by other organisms provide important refugia for many vertebrates and invertebrates. With severe range declines of most of Australia's burrowing mammals, the introduced European rabbit may have replaced the role of native burrowers. The vertebrate and invertebrate fauna using the warrens of the native burrowing bettong and greater bilby were compared with fauna using warrens of the introduced European rabbit and control sites without active warrens in arid South Australia. Echidnas, broad-banded sandswimmers, hemipterans and coleopterans, particularly Brises caraboides, revealed a preference for warrens over sites without warrens. Iridomryrmex sp. E (rufoniger gp.) was recorded at significantly higher abundance at bettong rather than rabbit warrens and Melophorus ants apparently benefited from the bare ground around warrens of both native burrowers and rabbits. Identification of small mammal preferences for different warren types was confounded by low predation rates inside the Arid Recovery Reserve, where cats and foxes had been exterminated to allow reintroduction of native burrowers. Due to the widespread use of the below ground and surface features of warrens by commensal native vertebrates and invertebrates, consideration should be given to reintroducing native burrowers following the removal of rabbits in arid Australia.
Article
Physical ecosystem engineers often make major, durable physical constructs that can provide living space for other species and can structure local animal communities over evolutionary time. In Florida, a medium sized chelonian, the Gopher Tortoise (Gopherus polyphemus) will excavate extensive subterranean chambers that can endure for long periods of time. The tortoise starts a ‘burrowing cascade’, by first excavating a larger burrow that may extend 10m, which is then re-engineered by Florida Mice (Podomys floridanus) and other rodents that dig smaller side-burrows and pockets. This sequence is often followed by an invertebrate, the camel cricket (Ceuthophilus labibuli) which is reported to excavate even smaller chambers. Our first aim was to quantify the zoogeomorphic impact of this burrowing cascade by measuring the amount of soil excavated in a large sample of burrows in two communities. Secondly, we hypothesized that the high biodiversity reported for these structures might be related to the quasi-fractal nature of the geometry, following the work of Frontier (1987). To visualize this underground geometry, we used high-resolution 3D Ground Penetrating Radar (GPR), which provided images and insights previously unobtainable using excavations or 2D GPR. Our images verified that the active tortoise burrow had a spiraling shape, but also showed splits in the larger burrow apparently dug by tortoises. For the first time, the smaller Florida Mouse burrows were imaged, showing side loops that exit and re-renter the tortoise burrow. This study also presents new information by making the discovery of numerous remnants of past tortoise burrows deeper underground in the sampling grid surrounding the active burrow. Our third aim was to interpret our field results with previous ecological field studies to evaluate the strength of evidence that this species ranks as an ecosystem engineer.
Article
Burrow systems constructed by banner-tailed kangaroo rats Dipodomys spectabilis provide important refuges for ground-dwelling animals to escape from harsh surface conditions. Two species of lizards and several groups of invertebrates were significantly more abundant at burrow systems than in the intervening grassland. Many other animals used the burrow systems, but did not exhibit differential abundance. The kangaroo rat creates habitat patches that are abiotically moderate and contain high concentrations of food resources. -from Authors
Article
A general binomial mixture model is proposed for the species accumulation function based on presence-absence (incidence) of species in a sample of quadrats or other sampling units. The model covers interpolation between zero and the observed number of samples, as well as extrapolation beyond the observed sample set. For interpolation (sample-based rarefaction), easily calculated, closed-form expressions for both expected richness and its confidence limits are developed (using the method of moments) that completely eliminate the need for resampling methods and permit direct statistical comparison of richness between sample sets. An incidence-based form of the Coleman (random-placement) model is developed and compared with the moment-based interpolation method. For extrapolation beyond the empirical sample set (and simultaneously, as an alternative method of interpolation), a likelihood-based estimator with a bootstrap confidence interval is described that relies on a sequential, AIC-guided algorithm to fit the mixture model parameters. Both the moment-based and likelihood-based estimators are illustrated with data sets for temperate birds and tropical seeds, ants, and trees. The moment-based estimator is confidently recommended for interpolation (sample-based rarefaction). For extrapolation, the likelihood-based estimator performs well for doubling or tripling the number of empirical samples, but it is not reliable for estimating the richness asymptote. The sensitivity of individual-based and sample-based rarefaction to spatial (or temporal) patchiness is discussed.
Article
The world’s grassland ecosystems are shaped in part by a key functional group of social, burrowing, herbivorous mammals. Through herbivory and ecosystem engineering they create distinctive and important habitats for many other species, thereby increasing biodiversity and habitat heterogeneity across the landscape. They also help maintain grassland presence and serve as important prey for many predators. However, these burrowing mammals are facing myriad threats, which have caused marked decreases in populations of the best-studied species, as well as cascading declines in dependent species and in grassland habitat. To prevent or mitigate such losses, we recommend that grasslands be managed to promote the compatibility of burrowing mammals with human activities. Here, we highlight the important and often overlooked ecological roles of these burrowing mammals, the threats they face, and future management efforts needed to enhance their populations and grassland ecosystems.
Article
The pygmy rabbit (Brachylagus idahoensis) is a secretive, obligate sagebrush-steppe resident of the Intermountain West and is one of two rabbits in North America that digs its own burrows. Although the pygmy rabbit has a recorded home range of 0.21–67.9 ha in relatively high sagebrush cover (21%–36%), they spend much of their time within 30–100 m of a burrow system. Due to big sagebrush cover in preferred habitat and the secretive behavior of pygmy rabbits, it is often difficult to study this leporid through direct observation. We used remote cameras to document pygmy rabbit activity at burrow systems in south central Utah from 2006 to 2008. We analyzed photographs from remote cameras for daily and seasonal patterns of activity. Our results suggested that time of day and season were important influences on activity level, while year and site were less so. Pygmy rabbits were active during all time periods of the day, but the greatest activity occurred in the morning, except during winter. Numerous other species were recorded by remote cameras, including other leporids, birds, rodents, reptiles, and terrestrial predators. Remote cameras are a valuable tool in understanding pygmy rabbit behavior, in addition to confirming rabbit presence in areas of interest.
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Species richness is a fundamental measurement of community and regional diversity, and it underlies many ecological models and conservation strategies. In spite of its importance, ecologists have not always appreciated the effects of abundance and sampling effort on richness measures and comparisons. We survey a series of common pitfalls in quantifying and comparing taxon richness. These pitfalls can be largely avoided by using accumulation and rarefaction curves, which may be based on either individuals or samples. These taxon sampling curves contain the basic information for valid richness comparisons, including category–subcategory ratios (species-to-genus and species-to-individual ratios). Rarefaction methods – both sample-based and individual-based – allow for meaningful standardization and comparison of datasets. Standardizing data sets by area or sampling effort may produce very different results compared to standardizing by number of individuals collected, and it is not always clear which measure of diversity is more appropriate. Asymptotic richness estimators provide lower-bound estimates for taxon-rich groups such as tropical arthropods, in which observed richness rarely reaches an asymptote, despite intensive sampling. Recent examples of diversity studies of tropical trees, stream invertebrates, and herbaceous plants emphasize the importance of carefully quantifying species richness using taxon sampling curves.
Article
Fertile patches are created and maintained by a combination of physical and biologically-mediated processes including soil disturbance by animals. We examined the creation of fertile patches by 4 vertebrates, the greater bilby Macrotis lagotis, burrowing bettong Bettongia lesueur, European rabbit Oryctolagus cuniculus, and Gould's sand goanna Varanus gouldii within dunes, ecotones, and swales in a dunefield in arid South Australia. These animals all create pits when foraging for subterranean food resources. We hypothesized that 1) the effect of pits on litter capture would vary among landscapes and animal species, 2) larger pits would trap more litter and seed, 3) pits would contain more viable seed than the surrounding matrix, and 4) the effect of pits on soil chemistry would vary among animal species, and be greater in landscapes with more finely textured soils. We found that litter was restricted almost exclusively to the pits, and was greater in pits with larger openings. Litter capture was greater in ecotones and dunes than in swales. A total of 1307 seedlings from 46 genera germinated from litter samples taken from the pits, but no seedlings emerged from samples taken from soil surrounding the pits. Foraging pits contained significantly higher levels of total C and N than surrounding soil, and total C and N concentrations were greatest in swales and lowest in dunes. Pits contained ca 55% more mineralisable N that surface soils, and pits constructed by bilbies and bettongs contained half the concentration of mineralisable N as those of rabbits and goannas. Concentrations of mineral N and mineralisable N were also greatest in the swales. Our results demonstrate the importance of animal-created pits as nutrient sinks and sites for seedling establishment, and suggest that changes in the composition of arid zone vertebrates may have resulted in profound changes to nutrient and soil dynamics in arid Australia.
Article
Although elephants are commonly cited as an example of ecosystem engineering, cases involving Asian elephants are missing in the literature. In a dry environment of southeastern Sri Lanka, I examined 290 elephant dung piles and found a total of six frogs from three different species in 1.7 percent (N=5) of the dung piles. This suggests a facilitative role of elephants by providing habitat for amphibians. Aunque los elefantes son citados frequentemente como ejemplo de ingeniería de ecosistemas, en la literatura no hay casos que impliquen al elefante asiático. En un ambiente seco del sureste de Sri Lanka examiné 290 excrementos de elefante y encontré un total de seis ranas de tres especies diferentes en 1,7 por ciento (N = 5) de los excrementos. Esto sugiere un rol facilitador de los elefantes proveyendo hábitat para anfibios.
Article
Certain species play particularly large roles in ecosystems, and are often referred to as keystones. However, little is known about the interactive effects of these species where they co-occur. Prairie dogs (Cynomys spp.) and banner-tailed kangaroo rats Dipodomys spectabilis are commonly considered keystone species of grassland ecosystems, creating a mosaic of unique habitats on the landscape through ecosystem engineering and herbivory. We examined the separate and interactive effects of these species on the structure of grassland arthropod communities. We conducted a cross-site study at two locations in the northern Chihuahuan Desert, and evaluated the impacts of these rodents on ground-dwelling arthropod and grasshopper communities in areas where prairie dogs and kangaroo rats co-occurred compared to areas where each rodent species occurred alone. Our results demonstrate that prairie dogs (C. gunnisoni and C. ludovicianus) and banner-tailed kangaroo rats had keystone-level impacts on arthropod communities both separately and interactively. Their burrow systems provided important habitats for multiple trophic and taxonomic groups of arthropods, and increased overall arthropod abundance and species richness. Many arthropods also were attracted to the aboveground habitats around the mounds and across the landscapes where the rodents occurred. Detritivores, predators, ants, grasshoppers, and rare rodent burrow inhabitants were especially associated with prairie dog and kangaroo rat activity. The impacts of prairie dogs and kangaroo rats were unique, and the habitats they created supported different assemblages of arthropods. Where both rodent species co-occurred, there was greater heterogeneity and arthropod diversity on the landscape. Our results suggest that the interaction of multiple keystones, especially those with engineering roles, results in unique and more diverse communities in time and space.