Selection of food patches by sympatric herbivores in response to concealment and distance from a refuge

Small herbivores face risks of predation while foraging and are often forced to trade off food quality for safety. Life history, behaviour, and habitat of predator and prey can influence these trade‐offs. We compared how two sympatric rabbits (pygmy rabbit, Brachylagus idahoensis; mountain cottontail, Sylvilagus nuttallii) that differ in size, use of burrows, and habitat specialization in the sagebrush‐steppe of western North America respond to amount and orientation of concealment cover and proximity to burrow refuges when selecting food patches. We predicted that both rabbit species would prefer food patches that offered greater concealment and food patches that were closer to burrow refuges. However, because pygmy rabbits are small, obligate burrowers that are restricted to sagebrush habitats, we predicted that they would show stronger preferences for greater cover, orientation of concealment, and patches closer to burrow refuges. We offered two food patches to individuals of each species during three experiments that either varied in the amount of concealment cover, orientation of concealment cover, or distance from a burrow refuge. Both species preferred food patches that offered greater concealment, but pygmy rabbits generally preferred terrestrial and mountain cottontails preferred aerial concealment. Only pygmy rabbits preferred food patches closer to their burrow refuge. Different responses to concealment and proximity to burrow refuges by the two species likely reflect differences in perceived predation risks. Because terrestrial predators are able to dig for prey in burrows, animals like pygmy rabbits that rely on burrow refuges might select food patches based more on terrestrial concealment. In contrast, larger habitat generalists that do not rely on burrow refuges, like mountain cottontails, might trade off terrestrial concealment for visibility to detect approaching terrestrial predators. This study suggests that body size and evolutionary adaptations for using habitat, even in closely related species, might influence anti‐predator behaviors in prey species.     

Foraging in a risky environment: a comparison of Bennett's wallabies Macropus rufogriseus rufogriseus (Marsupialia: Macropodidae) and red‐bellied pademelons Thylogale billiardierii (Marsupialia: Macropodidae) in open habitats

Abstract This study aimed to establish whether red‐bellied pademelons (Thylogale billiardierii) and Bennett's wallabies (Macropus rufogriseus rufogriseus) alter their foraging distribution in open habitat, in response to food availability and distance to protective shelter, the latter used as a measure of predation risk. Scat counts were used as a measure of the presence or absence of these macropods over two plantations (Russell and Dunalley). These plantations differed in both their on‐site food and shelter characteristics (the presence or absence of windrows). Logistic regression indicated that at Russell, which had low food availability but the presence of on‐site shelter, probability of scats of both species increased with the percentage cover of both edible and inedible vegetation. The probability of both pademelon and wallaby scats decreased with increasing distance from windrows, but increased with increasing distance from forest at the plantation edge. Logistic regression indicated that at Dunalley, which had high food availability but no on‐site shelter, the probability of scats of both species increased with an increase in the percentage cover of edible vegetation. In relation to predation risk, however, the two species differed in their response. Pademelons exhibited a decrease in scat probability with increasing distance from the forest at the plantation edge, while wallabies showed an increase in scat probability with distance from the forest at the plantation edge. Results indicated some differences in antipredation strategies of the two species, which may be a function of differences in body size.     

Home range dynamics of the yellow‐footed rock‐wallaby (Petrogale xanthopus celeris) in central‐western Queensland

Analyses of the interspecific differences in macropod home range size suggest that habitat productivity exerts a greater influence on range size than does body mass. This relationship is also apparent within the rock‐wallaby genus. Lim reported that yellow‐footed rock‐wallabies (Petrogale xanthopus xanthopus) inhabiting the semi‐arid Flinders Ranges (South Australia) had a mean home range of 170 ha. While consistent with the hypothesis that species inhabiting less productive habitats will require larger ranges to fulfil their energetic requirements, the ranges reported by Lim were considerably larger than those observed for heavier sympatric macropods. The aim of the current study was to document the home range dynamics of P. x. celeris in central‐western Queensland and undertake a comparison with those reported for their southern counterparts. Wallaby movements were monitored at Idalia National Park, between winter 1992 and winter 1994. Male foraging ranges (95% fixed kernel; 15.4 ha, SD = ±7.8 ha) were found to be significantly larger than those of female wallabies (11.3 ha, SD = ±4.9 ha). Because of varying distances to the wallabies' favoured foraging ground (i.e. an adjacent herb field), the direction in which the wallabies moved to forage also significantly affected range size. Mean home range size was estimated to be 23.5 ha (SD = ±15.2 ha; 95% fixed kernel) and 67.5 ha (SD = ±22.4 ha; 100% minimum convex polygon). The discrepancy between these two estimates resulted from the exclusion of locations, from the 95% kernel estimates, when the wallabies moved to a water source 1.5 km distant from the colony site. The observed foraging and home ranges approximated those that could be expected for a macropod inhabiting the semi‐arid zone (i.e. 2.4 times larger‐than‐predicted from body mass alone). Possible reasons for the disparity between the current study and that of Lim are examined.     

Red kangaroos (<Emphasis Type="Italic">Macropus rufus</Emphasis>) receive an antipredator benefit from aggregation

For species that cannot seek cover to escape predators, aggregation becomes an important strategy to reduce predation risk. However, aggregation may not be entirely beneficial because aggregated animals may compete for access to limited resources and might even attract predators. Available evidence suggests that foraging competition influences time allocation in large-bodied macropodid marsupials, but previous studies have focused primarily on species in areas with protective cover. We studied red kangaroos, a species often found in open country without noticeable cover, to determine whether they experienced a net benefit by aggregation. Red kangaroos varied their time allocation as a function of group size and, importantly, more variation in time allocation to vigilance and foraging was explained by non-linear models than by linear models. This suggests red kangaroos directly translated the reduction of predation risk brought about by aggregation into greater time foraging and less time engaged in vigilance. We infer that red kangaroos received a net benefit by aggregation. Social species living in the open may be generally expected to rely on others to help manage predation risk. Communicated by K. Kotrschal     

Habitat selection by the swamp wallaby (Wallabia bicolor) in relation to diel period,food and shelter

Patterns of resource selection by animals may be influenced by sex, and often change over a 24‐h period. We used a dry sclerophyll landscape managed for commercial timber production to investigate the effects of sex and diel period on habitat selection by the swamp wallaby (Wallabia bicolor). We predicted that selection would be (i) affected by both sex and diel period; and (ii) positively related to lateral cover during the day, but to food resources at night. Non‐metric multidimentional scaling indicated that some of the available habitats differed markedly with respect to visibility (an indicator of lateral cover), fern cover, forb cover, wallaby density and a forage quality index, providing the basis for non‐random habitat selection. At the landscape scale, wallabies showed strong selection for 5‐year‐old regenerating sites, selected against 10‐year‐old regenerating sites and unharvested forest, and avoided recently harvested (3–10 months post‐harvest) sites completely. At the scale of individual home ranges, a pooled male and female sample demonstrated selection for unharvested forest over recently harvested sites during both diurnal and nocturnal periods. A separate analysis showed that both sex and diel period influenced the selection of 5‐ and 10‐year‐old sites and the surrounding unharvested forest. Using a novel approach, we demonstrated that diurnal habitat selection by both sexes was negatively correlated with visibility, representing stronger selection for areas with more lateral cover. Nocturnal selection by females was positively correlated with values of a forage quality index, but this was not the case for males. We hypothesise that the observed patterns of selection were driven by the need to find food and avoid predators, but were also affected by the different reproductive strategies of males and females. Our results demonstrate the importance of incorporating factors such as sex and diel period into analyses of habitat selection.     

Resolution of portions of the kangaroo phylogeny (Marsupialia: Macropodidae) using DNA hybridization

We generated a DNA hybridization matrix comparing eleven 'true' kangaroos (Macropodinae) and two outgroup marsupials, the rufous rat-kangaroo Aepyprymnus rufescens (Potoroinae) and the brush-tailed phalanger Trichosurus vulpecula (Phalangeridae). A small matrix included additional species of the genus Macropus (large kangaroos and wallabies). The results indicate that the New Guinean forest wallaby Dorcopsulus vanheurni, and the quokka Setonix brachyurus, represent successively closer sister-groups of other macropodines. The remaining taxa examined form two clades: the tree kangaroo Dendrolagus matschiei with die pademelons Thylogale and rock wallabies Petrogale, and Macropus including the swamp wallaby Wallabia bicolor. The smaller matrix of five Macropus species and Wallabia (with Dorcopsulus as an outgroup) pairs the red-necked wallaby M. rufogriseus and Parry's wallaby M. parryi, with the eastern grey kangaroo M. giganteus as their nearest relative; and associates the red kangaroo M. rufus and wallaroo M. robustus, with Wallabia as their sister-taxon. In the larger study, we found mat inclusion of both outgroups provided little resolution among the macropodines, judging by jackknife and bootstrap tests. When Aepyprymnus was deleted, the Dendrolagus-Thylogale-Petrogale association obtained; with Trichosurus eliminated instead, the Wallabia-Macropus group was recovered. Only analysis of the eleven ingroup taxa by themselves gave a topology which supported both major clades. Our findings suggest that, at least for DNA hybridization studies, when ingroup taxa are separated by very short internodes experimental error in outgroup-to-ingroup distances may seriously compromise determination of ingroup affinities as well as the position of the root. We recommend that in such cases separate analyses with the outgroups sequentially eliminated and rigorous validation of die topology at each step should be conducted.     

Circadian rhythms enable efficient resource selection in a human‐modified landscape

Animals access resources such as food and shelter, and acquiring these resources has varying risks and benefits, depending on the suitability of the landscape. Some animals change their patterns of resource selection in space and time to optimize the trade‐off between risks and benefits. We examine the circadian variation in resource selection of swamp wallabies (Wallabia bicolor) within a human‐modified landscape, an environment of varying suitability. We used GPS data from 48 swamp wallabies to compare the use of landscape features such as woodland and scrub, housing estates, farmland, coastal areas, wetlands, waterbodies, and roads to their availability using generalized linear mixed models. We investigated which features were selected by wallabies and determined whether the distance to different landscape features changed, depending on the time of the day. During the day, wallabies were more likely to be found within or near natural landscape features such as woodlands and scrub, wetlands, and coastal vegetation, while avoiding landscape features that may be perceived as more risky (roads, housing, waterbodies, and farmland), but those features were selected more at night. Finally, we mapped our results to predict habitat suitability for swamp wallabies in human‐modified landscapes. We showed that wallabies living in a human‐modified landscape selected different landscape features during day or night. Changing circadian patterns of resource selection might enhance the persistence of species in landscapes where resources are fragmented and disturbed.     

Behavioural responses of free‐ranging western grey kangaroos (Macropus fuliginosus) to olfactory cues of historical and recently introduced predators

Predation risk influences foraging decisions and time allocation of prey species, and may result in habitat shifts from potentially dangerous to safer areas. We examined a wild population of western grey kangaroos (Macropus fuliginosus) to test the efficacy of predator faecal odour in influencing time allocated to different behaviours and inducing changes in habitat use. Kangaroos were exposed to fresh faeces of a historical predator, the dingo (Canis lupus dingo), a recently introduced predator, the red fox (Vulpes vulpes), a herbivore (horse, Equus caballus) and an unscented control simultaneously. Kangaroos did not increase vigilance in predator‐scented areas. However, they investigated odour sources by approaching and sniffing; more time was spent investigating fox odour than control odours. Kangaroos then exhibited a clear anti‐predator response to predator odours, modifying their space use by rapidly escaping, then avoiding fox and dingo odour sources. Our results demonstrate that wild western grey kangaroos show behavioural responses to predator faeces, investigating then avoiding these olfactory cues of potential predation risk, rather than increasing general vigilance. This study contributes to our understanding of the impact of introduced mammalian predators on marsupial prey and demonstrates that a native Australian marsupial can recognize and respond to the odour of potential predators, including one that has been recently introduced.     

Predation risk of eggs and nestlings relative to nest‐site characteristics of the Bull‐headed Shrike Lanius bucephalus

Appropriate nest‐site selection is one of the most important ways to minimize loss of reproductive investment due to predation. We determined the environmental characteristics associated with nest predation during the incubation and nestling periods of arboreal nesting Bull‐headed Shrikes on the oceanic Minami‐Daito Island where the predator community has low species diversity and includes only three introduced mammals: Ship Rat Rattus rattus, Japanese Weasel Mustela itatsi and Feral Cat Felis catus. Egg predation declined with increasing grassland cover around nests, whereas nestling predation declined with increasing nest concealment and nest height. Our results suggest that effective nest‐site characteristics for avoiding nest predation differ during the incubation and nestling periods and are dependent on the predator species and their search strategies, at least in habitats with low predator species diversity.     

Foraging behavior of three Tasmanian macropodid marsupials in response to present and historical predation threat

It is often essential to understand historical selection regimes to explain current traits. We studied antipredator behavior of three Tasmanian macropodid marsupials – Forester kangaroos Macropus giganteus , Bennett's wallabies M. rufogriseus , and Tasmanian pademelons Thylogale billardierii – to understand how antipredator behavior functions in a relatively intact predator community. We also compared behavior of the kangaroos and wallabies on a predator-free island where they were translocated from mainland Tasmania 30 yr ago. Both species allowed humans to get closer to them on the predator-free island; a finding consistent with a reduced risk of predation on the island. Neither kangaroos, nor wallabies, exhibited group size effects – they did not modify time allocated to foraging or antipredator vigilance as a function of group size at either site. Nor did overall time allocation vary in any consistent way. In contrast, mainland Australian sibling-species of Forester kangaroos and Bennett's wallabies have both been reported to have group size effects. It is possible either that the extinction of the thylacine Thylacinus cynocephalus in the last century has led to an evolutionary loss of group size effects and other antipredator behavior, or that thylacines were never that important a predator on Tasmanian subspecies. In contrast, Tasmanian pademelons studied on the Tasmanian mainland modified time allocation as a function of group size suggesting that they perceived safety in numbers. Pademelons, because of their body size, are relatively more vulnerable than larger-bodied macropodids to the rich community of marsupial carnivores in Tasmania, and used a mix of social and individual strategies to manage predation risk.     

State‐space modeling reveals habitat perception of a small terrestrial mammal in a fragmented landscape

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Does Feeding Competition Influence Tammar Wallaby Time Allocation?

Animals may aggregate to reduce predation risk, but this potentially incurs the cost of increased competition. We studied the degree to which competition for food influenced the time tammar wallabies (Macropus eugenii) allocate to foraging and vigilance by experimentally manipulating access to food, while holding other factors constant. Groups of six wallabies were observed when they had access to either one or six non‐depleting bins of supplemental food. Food availability had no effect on the time allocated to foraging, looking or affiliative interactions, and this was true whether individuals or groups were treated as the unit of analysis. However, wallabies engaged in substantially more aggressive acts in the high‐competition treatment. These results, when combined with other findings, suggest that the moderately social tammar wallaby receives an antipredator benefit by aggregating with conspecifics which is not reduced significantly by foraging competition.     

Using habitat selection theories to predict the spatiotemporal distribution of migratory birds during stopover – a case study of pink‐footed geese Anser brachyrhynchus

Understanding how animals select for habitat and foraging resources therein is a crucial component of basic and applied ecology. The selection process is typically influenced by a variety of environmental conditions including the spatial and temporal variation in the quantity and quality of food resources, predation or disturbance risks, and inter‐ and intraspecific competition. Indeed, some of the most commonly employed ecological theories used to describe how animals choose foraging sites are: nutrient intake maximisation, density‐dependent habitat selection, central‐place foraging, and predation risk effects. Even though these theories are not mutually exclusive, rarely are multiple theoretical models considered concomitantly to assess which theory, or combination thereof, best predicts observed changes in habitat selection over space and time. Here, we tested which of the above theories best‐predicted habitat selection of Svalbard‐breeding pink‐footed geese at their main spring migration stopover site in mid‐Norway by computing a series of resource selection functions (RSFs) and their predictive ability (k‐fold cross validation scores). At this stopover site geese fuel intensively as a preparation for breeding and further migration. We found that the predation risk model and a combination of the density‐dependent and central‐place foraging models best‐predicted habitat selection during stopover as geese selected for larger fields where predation risk is typically lower and selection for foraging sites changed as a function of both distance to the roost site (i.e. central‐place) and changes in local density. In contrast to many other studies, the nutritional value of the available food resources did not appear to be a major limiting factor as geese used different food resources proportional to their availability. Our study shows that in an agricultural landscape where nutritional value of food resources is homogeneously high and resource availability changes rapidly; foraging behaviour of geese is largely a tradeoff between fast refuelling and disturbance/predator avoidance.     

Bottom‐up processes in a declining yellow‐footed rock‐wallaby (Petrogale xanthopus celeris) population

Populations of large herbivores are generally considered to be food limited, escaping the regulatory effects of predation through their large body size, migratory behaviour and/or the occurrence of alternate prey species. In the Australian arid and semi‐arid zones, the availability of forage biomass is considered to be the primary driver of fluctuations in kangaroo abundance. However, little is known about the population dynamics of the smaller sympatric macropods. We examined the demographic traits of a large colony of yellow‐footed rock‐wallabies (Petrogale xanthopus celeris), following a 2‐year period of above average rainfall. The population was located within a conservation reserve that was subject to a predator control program around its perimeter and on neighbouring properties. The low predator abundance provided an opportunity to gauge the strength of bottom‐up population processes. During the two years of the study, the population declined in size by 53%, resulting from both the virtual absence of juvenile recruitment and the loss of adult wallabies. Although reproductive output was high, low pouch young and juvenile survival rates resulted in few individuals progressing into the adult population. With minimal recruitment, the rate of population decline (r = 0.77) matched the observed adult survival rate (Φ = 0.76). Despite average rainfall conditions during the study, survival rates across all age‐classes were equivalent to those reported for other rock‐wallaby populations during periods of scarcity. The reduced survival rates were attributed to low levels of forage resources, particularly around the wallabies' refuge sites, suggesting the bottom‐up regulation of the colony at high densities. The data suggest that the colony was at temporarily high abundance, following a rainfall driven pulse of recruitment. Conservation management actions for this species should focus on increasing juvenile survival rates within declining populations, through the control of feral goats (Capra hircus), rabbits (Oryctolagus cuniculus) and red foxes (Vulpes vulpes).     

Comparison of habitat selection by two sympatric macropods,Thylogale billardierii and Macropus rufogriseus rufogriseus,in a patchy eucalypt‐forestry environment

Abstract Population density estimates and patterns of habitat selection by sympatric red‐bellied pademelons (Thylogale billardierii (Marsupialia: Macropodidae)) and red‐necked wallabies (Macropus rufogriseus rufogriseus (Marsupialia: Macropodidae)) were examined within a patchy forestry environment in north‐west Tasmania. Population density of both species was relatively high. Selection indices from both population surveys and animal movement data showed that T. billardierii and M. rufogriseus had similar patterns of habitat selection at two spatio‐temporal scales; home range within the study area and habitats selected while foraging at night. Both species selected for young Eucalyptus nitens plantation with high weed‐cover within their home range. At night, T. billardierii and M. rufogriseus selected for open habitats (young plantation and grassland) and avoided closed habitats (native forest and 5–7 years old E. nitens plantation). There was no evidence for resource partitioning between species at these scales. In contrast, the two species differed in their selection for daytime sheltering habitat; T. billardierii selected native forest while M. rufogriseus selected older plantation. This may reflect differences in their predator avoidance strategies; that is, crypsis versus flight, rather than resource partitioning as a result of interspecific competition. The environment appears to be of high quality for both species, with patches of feeding and shelter habitats within close proximity of one another.     

Microhabitat nest‐site selection by ducks in the boreal forest

The boreal forest is one of the North America’s most important breeding areas for ducks, but information about the nesting ecology of ducks in the region is limited. We collected microhabitat data related to vegetation structure and composition at 157 duck nests and paired random locations in Alberta’s boreal forest region from 2016 to 2018. We identified fine‐scale vegetation features selected by ducks for all nests, between nesting guilds, and among five species using conditional logistic regression. Ducks in the boreal forest selected nest sites with greater overhead and graminoid cover, but less forb cover than random sites. Characteristics of the nest sites of upland‐ and overwater‐nesting guilds differed, with species nesting in upland habitat selecting nests that provided greater shrub cover and less lateral concealment and species nesting over water selecting nests with less shrub cover. We examined the characteristics of nest sites of American Wigeon (Mareca americana), Blue‐winged Teal (Spatula discors), Green‐winged Teal (Anas crecca), Mallards (Anas platyrhynchos), and Ring‐necked Ducks (Aythya collaris), and found differences among species that may facilitate species coexistence at a regional scale. Our results suggest that females of species nesting in upland habitat selected nest sites that optimized concealment from aerial predators while also allowing detection of and escape from terrestrial predators. Consequently, alteration in the composition and heterogeneity of vegetation and predator communities caused by climate change and industrial development in the boreal forest of Canada may affect the nest‐site selection strategies of boreal ducks.     

Livestock guardian dogs as surrogate top predators? How Maremma sheepdogs affect a wildlife community

Use of livestock guardian dogs (LGDs) to reduce predation on livestock is increasing. However, how these dogs influence the activity of wildlife, including predators, is not well understood. We used pellet counts and remote cameras to investigate the effects of free ranging LGDs on four large herbivores (eastern gray kangaroo, common wombat, swamp wallaby, and sambar deer) and one mesopredator (red fox) in Victoria, Australia. Generalized mixed models and one‐ and two‐species detection models were used to assess the influence of the presence of LGDs on detection of the other species. We found avoidance of LGDs in four species. Swamp wallabies and sambar deer were excluded from areas occupied by LGDs; gray kangaroos showed strong spatial and temporal avoidance of LGD areas; foxes showed moderately strong spatial and temporal avoidance of LGD areas. The effect of LGDs on wombats was unclear. Avoidance of areas with LGDs by large herbivores can benefit livestock production by reducing competition for pasture and disease transmission from wildlife to livestock, and providing managers with better control over grazing pressure. Suppression of mesopredators could benefit the small prey of those species. Synthesis and applications: In pastoral areas, LGDs can function as a surrogate top‐order predator, controlling the local distribution and affecting behavior of large herbivores and mesopredators. LGDs may provide similar ecological functions to those that in many areas have been lost with the extirpation of native large carnivores.     

The impact of grazing by macropods on coastal foredune vegetation in southeast Queensland

Abstract The extent of grazing by two macropodids, the agile wallaby (Macropus agilis) and the swamp wallaby (Wallabia bicolor) on coastal foredunes on South Stradbroke Island in southeast Queensland was investigated to determine potential impacts on the principal sand colonizing species, sand spinifex grass (Spinifex sericeus). Grazing on spinifex grass on the foredunes of South Stradbroke island can be attributed principally to agile wallabies. Foraging activity by wallabies was higher in areas of high spinifex abundance, however, grazing intensity and impact on spinifex was only important on foredunes with low spinifex abundance. Spinifex consumption by wallabies was also related to a number of factors, especially composition and structure of vegetation in adjacent habitats. Spinifex consumption increased when the abundance of ground cover components (grasses, sedges, forbs) in adjacent habitats was low and structural complexity was high. Grazing on foredunes by wallabies significantly affects the species composition of the foredune community by excluding the establishment of a number of perennial foredune plant species. This may have implications for community succession in coastal ecosystems.     

Habitat and introduced predators influence the occupancy of small threatened macropods in subtropical Australia

Australia has had the highest rate of mammal extinctions in the past two centuries when compared to other continents. Frequently cited threats include habitat loss and fragmentation, changed fire regimes and the impact of introduced predators, namely the red fox (Vulpes vulpes) and the feral cat (Felis catus). Recent studies suggest that Australia's top predator, the dingo (Canis dingo), may have a suppressive effect on fox populations but not on cat populations. The landscape of fear hypothesis proposes that habitat used by prey species comprises high to low risk patches for foraging as determined by the presence and ubiquity of predators within the ecosystem. This results in a landscape of risky versus safe areas for prey species. We investigated the influence of habitat and its interaction with predatory mammals on the occupancy of medium‐sized mammals with a focus on threatened macropodid marsupials (the long‐nosed potoroo [Potorous tridactylous] and red‐legged pademelon [Thylogale stigmatica]). We assumed that differential use of habitats would reflect trade‐offs between food and safety. We predicted that medium‐sized mammals would prefer habitats for foraging that reduce the risk of predation but that predators would have a positive relationship with medium‐sized mammals. We variously used data from 298 camera trap sites across nine conservation reserves in subtropical Australia. Both dingoes and feral cats were broadly distributed, whilst the red fox was rare. Long‐nosed potoroos had a strong positive association with dense ground cover, consistent with using habitat complexity to escape predation. Red‐legged pademelons showed a preference for open ground cover, consistent with a reliance on rapid bounding to escape predation. Dingoes preferred areas of open ground cover whereas feral cats showed no specific habitat preference. Dingoes were positively associated with long‐nosed potoroos whilst feral cats were positively associated with red‐legged pademelons. Our study highlights the importance of habitat structure to these threatened mammals and also the need for more detailed study of their interactions with their predators.     

Olfactory and visual plant cues as drivers of selective herbivory

Food quality is an important consideration in the foraging strategy of all animals, including herbivores. Those that can detect and assess the nutritional value of plants from afar, using senses such as smell and sight, can forage more efficiently than those that must assess food quality by taste alone. Selective foraging not only affects herbivore fitness but can influence the structure and composition of plant communities, yet little is known about how olfactory and visual cues help herbivores to find preferred plants. We tested the ability of a free‐ranging, generalist mammalian browser, the swamp wallaby Wallabia bicolor, to use olfactory and visual plant cues to find and/or browse differentially on Eucalyptus pilularis seedlings grown under different nutrient conditions. Low‐nutrient seedlings differed from high‐nutrient seedlings, having lighter coloured leaves, red stems and lower biomass and nitrogen content. In the absence of visual cues, wallabies used odour to differentiate vials containing cut seedlings. They visited and investigated patches with high‐nutrient seedling odour most, followed by patches with low‐nutrient seedling odour, and patches with no added odour least. However, when visual and olfactory cues of seedlings were present, wallabies reversed their foraging response and were more likely to browse low‐ than high‐nutrient seedlings. This browsing difference, in turn, disappeared when long‐range visual cues were reduced by pinning seedlings horizontal to the ground. We suggest that visual cues overrode the effects of olfactory cues on browsing patterns of intact seedlings. Our study shows that herbivores can respond to odours of higher nutrient plants but in ecologically realistic scenarios they use a variety of visual and olfactory cues, with a context‐dependent outcome that is not always selection of high nutrient food. Our results demonstrate the importance of testing the sensory abilities of herbivores in realistic multi‐sensory settings to understand their function in selective foraging.