Intraspecific variation in Eucalyptus secondary metabolites determines food intake by folivorous marsupials

Traditional approaches to the question of the effects of plant secondary metabolites on the feeding choices of folivores of Eucalyptus have focused on the tree species level, although numerous field studies of foraging behaviour have identified selection at the level of the individual trees. Attempts to relate these decisions to deterrency resulting from secondary leaf chemistry have been inconclusive because assays used have focused on broad groups of compounds such as “total” phenolics. In this study we have conducted no-choice feeding trials with two arboreal mammalian folivores, the common ringtail possum (Pseudocheirus peregrinus) and the koala (Phascolarctos cinereus), to measure deterrency of individual trees of two species of Eucalyptus, E. ovata and E. viminalis. Average daily intakes of E. ovata foliage by common ringtail possums ranged from 2.5 to 50 g kg^−0.75 body mass. Koala intakes of foliage from the same individual trees ranged from 22.4 to 36.3 g kg^−0.75 body mass. When fed foliage from different individual E. viminalis trees, common ringtail possums ate between 1.26 and 6.28 g kg^−0.75 body mass while koalas ate from 14.3 to 45.9 g kg^−0.75 body mass. Correlative analyses showed no relationships between feeding and several measures of nutritional quality, nor with total phenolics or condensed tannins. They did, however, identify two groups of plant secondary metabolites that may cause deterrency: terpenes, and a defined group of phenolic compounds, the diformylphloroglucinols (DFPs). Further bioassay experiments with common ringtail possums showed that only the DFPs could cause the effects seen with the foliage experiments at concentrations similar to those found in the leaves. We argue that, when in sufficiently high concentrations, DFPs determine the level of food intake by these animals irrespective of other questions of nutritional quality of the leaves. Received: 20 October 1997 / Accepted: 23 March 1998     

Does a sap feeding marsupial choose trees with specific chemical characteristics?

Only about 20 vertebrate species are known to feed regularly on tree sap. One of these is the yellow‐bellied glider (Petaurus australis), a marsupial that obtains between 16% and 80% of its diet from eucalypt sap. We reviewed the literature on sap feeding by the yellow‐bellied glider and identified 10 species from which it most frequently obtains sap. These species come mainly from a few sections of the subgenus Symphyomyrtus, which accounts for two‐thirds of over 2000 sap trees reported, but more specifically sections Latoangulatae and Maidenii within this subgenus. Some of these key species contain relatively high concentrations of foliar nutrients and each is an important food tree for at least one of the arboreal folivores – koala (Phascolarctos cinereus), greater glider (Petauroides volans), and common ringtail (Pseudocheirus peregrinus) and brushtail possums (Trichosurus vulpecula). Because yellow‐bellied gliders, like the arboreal folivores, prefer to feed from certain individuals within a species, we hypothesized that these trees possess a unique chemical signature that links sap‐feeding with the concentrations of available nitrogen and formylated phloroglucinol compounds in leaves – the nutritive and defensive chemicals that influence feeding on these species by marsupial folivores. We tested this hypothesis in samples of leaves and bark collected from E. punctata and E. viminalis but found no link between chemistry and sap feeding and conclude that other aspects of an individual tree, such as sap flow or sap chemistry, determine whether gliders will target it for sap.     

Differential susceptibility to Eucalyptus secondary compounds explains feeding by the common ringtail (Pseudocheirus peregrinus) and common brushtail possum (Trichosurus vulpecula)

The effect of two plant secondary metabolites, tannins and formylated phloroglucinol compounds (FPCs), on the intake of Eucalyptus foliage by common ringtail (Pseudocheirus peregrinus) and common brushtail possums (Trichosurus vulpecula) was studied. We manipulated the amount of tannin that was free to bind with protein by coating foliage with polyethylene glycol 4000 (PEG) and relied on natural intraspecific variation in FPC concentrations. In contrast to ringtail possums, brushtail possums showed a greater tolerance to FPCs and ate more foliage when it was coated with PEG, suggesting that tannins limited their food intake. Brushtails detected the effects of tannins through immediate oral sensations rather than through systemic effects. Ringtail possums appeared highly tolerant of foliar tannins yet susceptible to low concentrations of FPCs. We could not detect any interaction between tannins and FPCs that affected the intake of Eucalyptus foliage by either species of possum. Although ringtail and brushtail possums are widely regarded as specialist and generalist folivores, respectively, their differential susceptibility to co-occurring secondary metabolites suggests greater complexity. Each possum species appears to be a specialist in its own right, which leads to a partitioning of available foliage. Brushtails avoid tannins and ringtails avoid FPCs.     

Sheoak woodlands: a newly identified habitat for western ringtail possums

Although critically endangered western ringtail possums (Pseudocheirus occidentalis) have been recorded from a variety of vegetation types in southwestern Australia, the extent to which many of these vegetation types are occupied by the species remains unknown. We conducted spotlight surveys for western ringtail possums between March and April 2018 in Albany, southwestern Australia, to determine the species’ occupancy in 2 vegetation types. Using occupancy models, we demonstrated that sheoak (Allocasuarina fraseriana) woodlands, previously unrecognized as providing western ringtail possum habitat, support the species, although the median probability of their occupancy was lower than in marri (Corymbia calophylla) and eucalypt (Eucalyptus marginata and E. staeri) woodlands. Use of trees and other habitat components by western ringtail possums varied within and between vegetation types. Sheoak woodlands are likely critical for western ringtail possums and given the apparent flexibility in vegetation types used by the species, investigation of the potential value of other vegetation types for this species has conservation merit. © 2019 The Wildlife Society.     

New evidence of unexpectedly high animal density and diet diversity will benefit the conservation of the Critically Endangered western ringtail possum

A comprehensive and contemporary understanding of habitat and resource requirements has been critical to the conservation of multiple taxa and ecosystems globally. Until recently, much of the ecological knowledge that contributes to conservation priorities and strategies for the Critically Endangered western ringtail possum (Pseudocheirus occidentalis) was largely derived from decades‐old observations in peppermint (Agonis flexuosa) and marri‐jarrah (Corymbia calophylla and Eucalyptus marginanta) woodlands in the northern parts of the species range. These observations do not account for more recent evidence of their flexible use of habitat resources in other regions of its range. This may represent a significant conservation opportunity for the species through the identification of additional habitats that warrant protection. In a region where knowledge of their ecology is scarce, we used scat analysis and quantitative spotlighting to determine the diet and density of western ringtail possums in three vegetation types: peppermint, sheoak (Allocasuarina fraseriana) and marri‐eucalypt (C. calophylla, E. marginanta and Eucalyptus staerii) woodlands. Given the species’ reported dependence on peppermint woodlands and dominant canopy species for food sources, we hypothesised that western ringtail possums would be most abundant in this habitat type and that their diet would comprise the foliage of few (≤2 species) canopy species. We found western ringtail possums consumed a higher diversity of plant species than expected (8–14), exhibited dietary preference for non‐dominant canopy species and were present in all sampled vegetation types at substantially higher densities than previously recorded for the region (as high as 17 possums ha^?1). Our results confirm (i) the western ringtail possum is flexible in its use of habitat resources and (ii) the significant conservation value of sheoak and marri‐eucalypt woodlands in the southernmost portion of its distribution.     

Sideroxylonal in Eucalyptus foliage influences foraging behaviour of an arboreal folivore

Plant secondary metabolites (PSMs) offer plants chemical defences against herbivores, and are known to influence intake and diet choice in both insect and mammalian herbivores. However, there is limited knowledge regarding how PSMs influence herbivore foraging decisions. Herbivore foraging decisions, in turn, directly impact on which individual plants, and plant species, are selected for consumption. We took advantage of the natural variation in sideroxylonal concentrations in the foliage of Eucalyptus melliodora (Cunn. ex Schauer) to investigate feeding patterns of a marsupial folivore, the common ringtail possum, Pseudocheirus peregrinus (Boddaert 1785). Foliage, collected from six trees, contained between 0.32 and 12.97 mg g-DM^-1 sideroxylonal. With increasing sideroxylonal concentrations, possums decreased their total intake, rate of intake and intake per feeding bout, and increased their cumulative time spent feeding. Possums did not alter their total feeding time, number of feeding bouts or time per feeding bout in response to increasing sideroxylonal concentrations. Results demonstrate important behavioural changes in foraging patterns in response to sideroxylonal. These behavioural changes have important implications, in relation to altered foraging efficiency and potential predation risk, for herbivores foraging in the field. As a result, the spatial distribution of dietary PSMs across a landscape may directly influence herbivore fitness, and ultimately habitat selection of mammalian herbivores.     

Feeding Ecology of <Emphasis Type="Italic">Trachypithecus pileatus</Emphasis> in India

We observed a group of capped langurs for 12 mo in the Pakhui Wildlife Sanctuary, Arunachal Pradesh, India. We recorded the time of feeding on different food plant species, food categories, and the feeding heights of monkeys in trees. Capped langurs spent 68% of their feeding time on leaves, 16% on flowers, and 16% on fruits. Feeding on leaves was consistently high (p < 0.01) during the year, with the highest feeding in May (85%) and the lowest in January (47%). The seasonal difference in feeding on leaves is significant (p < 0.05): it was higher in summer and during monsoon. The feeding time on flowers was maximal (35%) in March and that on fruits and seeds was minimal (38%) in January. Langurs ate 52 plant species throughout the year. The largest number of plants (6) were species of Moraceae, and langurs spent more feeding time (20%) on them alone. The number of plants eaten per month varied significantly (p < 0.05). Langurs ate Gmelina arborea, Albizzia lucida, Ficus glomereta, and Makania micrantha throughout the year. They spent 44% of their feeding time in terminal canopies and their average feeding height was 30–35 m. This is the first study to examine the feeding ecology of capped langurs and provides baseline data for the species.     

Resilience of arboreal folivores to habitat damage by a severe tropical cyclone

Abstract Severe tropical cyclones greatly modify habitat of arboreal folivores by destroying forest canopy, reducing structure and complexity and defoliating remaining trees. We hypothesized that forest modification following severe Cyclone Larry would stress arboreal folivores of the Family Pseudocheiridae and be reflected in increased home ranges and a decrease in body condition. We conducted 19 pre‐cyclone and 24 post‐cyclone spotlighting surveys at a site with severe cyclone damage, and 18 post‐cyclone surveys at a site with minor damage. We detected a greater number of lemuroid, Hemibelideus lemuroides and green, Pseudochirops archeri, ringtail possums as these possums remained in the severely damaged canopy and forest edge. In contrast, Herbert River ringtail possums, Pseudochirulus herbertensis, were detected in smaller numbers. We radio‐tracked eight P. herbertensis before the cyclone, following two of these and nine new animals after the category 4 cyclone. No significant post‐cyclone alteration in home range area or span was recorded in data pooled across the two sites or in limited post‐cyclone data at the severely disturbed site, but a greater variability in home range was observed after cyclone (pooled across sites: 1.72 ± 0.77 ha; 197 ± 47 m) than before the cyclone (1.35 ± 0.30 ha; 196 ± 23 m). In contrast, pooled pre‐ and post‐cyclone home range areas and spans were larger at the severely‐disturbed site (2.08 ± 0.56 ha; 231 ± 32 m) than at the site with minor damage (0.68 ± 0.11 ha; 114 ± 25 m), suggesting resources were more widely spread at the former site. Post‐cyclone home ranges were also larger at the severely damaged site (severe: 3.33 ± 1.36 ha, n = 3; minor: 0.52 ± 0.07 ha, n = 4). Condition of P. herbertensis (mass/tail length) did not differ significantly pre‐ and post‐cyclone or between less and severely disturbed sites. These results and observations of breeding after cyclone suggest that possum populations may be resilient to severe cyclone damage under the relatively wet conditions experienced post‐Cyclone Larry.     

Predicting the Competitive Regime of Female <Emphasis Type="Italic">Colobus vellerosus</Emphasis> from the Distribution of Food Resources

We examined the spatial and temporal distribution of the foods of ursine colobus (Colobus vellerosus) at Boabeng-Fiema, Ghana as a means to predict the monopolizablity and usurpability of their food resources. Recent evidence suggests that food may not be limiting for folivorous primates, and that male sexual coercion may be a more important influence on folivore social organization. To address the question, we collected focal data on the feeding behavior of adult females and males over 11 mo (September 2000-August 2001) on 2 groups: WW (n = 31–33 individuals) and B (n = 8–16 individuals). We also conducted phenological monitoring and a tree survey of the two-group home ranges to establish food availability and distribution. We used 2 behavioral or organism-defined indicators of feeding behavior to assess potential resource contestability: food site residence time and distance moved between food sites. The colobus fed on a high diversity of species, most of their food trees were not clumped in distribution, within-tree interfood distances were short, and food trees were large. The only condition associated with the potential for monopolization was low food tree density. However, low food tree density may be offset by the colobus’ use of large trees. Taken together, the ecological and behavioral indicators suggest the food resources of Colobus vellerosus had a low potential for monopolization. Our results also indicate mature leaves had the longest food site residence time, which may suggest they should be the most usurpable plant part, though their presumed low quality and high abundance probably counteracted the effect. The pattern implied the potential for direct feeding competition among Colobus vellerosus at Boabeng-Fiema was low and agonistic interactions over food are not expected. Instead, a group size effect on feeding efficiency should be a more predominant influence on feeding efficiency, if food is limiting for the species.     

Early spring defoliation,secondary leaf flush,and leafminer outbreaks on American holly

Summary Adults of Phytomyza ilicicola (Diptera: Agromyzidae), a univoltine specialist leafminer, emerge in close synchrony with leaf flush of American holly and feed on and oviposit in soft, partially expanded leaves. Early spring defoliation, such as commonly results from freezing injury to young shoots, is followed several weeks later by a second flush of young leaves from lateral buds. We simulated this phenomenon by manually defoliating whole small trees and individual shoots of large trees to test the hypothesis that freezing injury can encourage leafminer outbreaks by inducing an abundance of soft, protein rich young leaves late in the adult activity period, when availability of vulnerable leaves becomes limited. Defoliation of small trees one or two weeks after bud break resulted in six- to 13-fold increases in the incidence of feeding punctures and larval mines on second flush leaves as compared with densities on original young leaves of control trees. Similarly, we induced significant increases in feeding punctures and larval mines on second flush leaves of individual defoliated shoots, although leaves that did not open until after the flight period escaped this injury. These observations underscore the capability of adult female P. ilicicola to locate and exploit a small number of phenologically available leaves among many hundreds of older leaves on the same tree. By altering the phenology of leaf flush, certain kinds of environmental stress may predispose perennial plants to outbreaks of early season folivores that restrict their feeding or oviposition to very young leaves.     

Foraging ecology of howler monkeys in a cacao (Theobroma cacao) plantation in Comalcalco, Mexico

Recent evidence indicates that primate populations may persist in neotropical fragmented landscapes by using arboreal agroecosystems, which may provide temporary habitats, increased areas of vegetation, and connectivity, among other benefits. However, limited data are available on how primates are able to sustain themselves in such manmade habitats. We report the results of a 9-month-long investigation of the feeding ecology of a troop of howler monkeys (n = 24) that have lived for the past 25 years in a 12-ha cacao plantation in the lowlands of Tabasco, Mexico. A vegetation census indicated the presence of 630 trees (> or =20 cm diameter at breast height (DBH)) of 32 shade species in the plantation. The howlers used 16 plant species (13 of which were trees) as sources of leaves, fruits, and flowers. Five shade tree species (Ficus cotinifolia, Pithecellobium saman, Gliricidia sepium, F. obtusifolia, and Ficus sp.) accounted for slightly over 80% of the total feeding time and 78% of the total number trees (n = 139) used by the howlers, and were consistently used by the howlers from month to month. The howlers spent an average of 51% of their monthly feeding time exploiting young leaves, 29% exploiting mature fruit, and 20% exploiting flowers and other plant items. Monthly consumption of young leaves varied from 23% to 67%, and monthly consumption of ripe fruit varied from 12% to 64%. Differences in the protein-to-fiber ratio of young vs. mature leaves influenced diet selection by the monkeys. The howlers used 8.3 ha of the plantation area, and on average traveled 388 m per day in each month. The howlers preferred tree species whose contribution to the total tree biomass and density was above average for the shade-tree population in the plantation. Given the right conditions of management and protection, shaded arboreal plantations in fragmented landscapes can sustain segments of howler monkey populations for many decades.     

西双版纳热带雨林中榕树动物群落结构与多样性研究

榕树是西双版纳热带雨林生态系统中的一个关键植物类群,在该类植物中,形成了以榕树果实、叶片、枝杆、枯枝落叶、土壤为食物、栖息、繁殖环境和帮助榕树授粉、传播种子的动物群落;榕树和动物之间形成了互相依赖、协同共存、互保发展的紧密关系。     

Use of leaf resources by howling monkeys (Alouatta palliata) and leaf-cutting ants (Atta cephalotes) in the tropical rain forest of Los Tuxtlas,Mexico

Use of leaf resources by a troop of howling monkeys and two colonies of leaf cutting ants was studied for an annual cycle in the rain forest of Los Tuxtlas, Mexico. Howling monkeys spent half their annual foraging time feeding on leaves; leaf-cutting ants spent at least 80% of their recorded foraging time harvesting leaves. Both herbivores preferred young leaves over nature ones, and chemical analysis showed that the protein: fibre ratio of the leaves used was correlated with these preferences. Howling monkeys used 34 tree species as leaf sources. Leaf-cutting ants used 40 plant species of which 38 were trees. Eighteen species used by Alouatta were also used by Atta; species of Moraceae and Lauraceae were among the most important in their foraging preferences. The plant species used by monkeys and ants occurred at low densities (? 4.0 ind/ha). The seasonal production of leaves, the high density of leaf-cutting ant colonies at the study site, and the high amounts of young foliage harvested by the ants from tree species, and individual trees used by howling monkeys as sources of young leaves suggest that the foraging activities of Atta may represent a significant pressure upon leaf resources available to Alouatta.     

Anthropogenic edges impact howler monkey (Alouatta palliata) feeding behaviour in a Costa Rican rainforest

Anthropogenic forest fragmentation impacts many aspects of animal behaviour, including feeding ecology. With forests increasingly fragmented in tropical regions due to human development, the proportion of forest edge (≤?100 m from clear-cut regions) is higher relative to forest interior. Forest edges differ in vegetation from interior, making it important to better understand how anthropogenic edges impact the feeding behaviour of primates such as mantled howler monkeys (Alouatta palliata). We predicted that howler monkeys would feed on higher-quality plant resources, from a larger number of tree families, and from larger trees in forest interior compared to anthropogenic forest edge. We surveyed howler monkey feeding behaviour across forest zones in a fragmented rainforest in Costa Rica, La Suerte Biological Research Station. We observed individual monkeys for 30-minute periods, collecting data on their feeding behaviour and tree use at 2-minute intervals. We measured feeding trees and recorded the plant parts and taxonomy of resources consumed. Monkeys consumed more leaves and fewer stems and fed from a smaller number of tree families in the forest interior, while they consumed fewer leaves and more stems and fed from a larger number of tree families in the forest edge. Monkeys also fed from larger, taller trees in the forest interior than the edge. The differences in howler monkey feeding behaviour between forest zones attest to the impact of human disturbance on howler monkey feeding ecology.

     

Resources at the landscape scale influence possum abundance

Abstract There is increasing realization that human perceptions of a ‘patchy’ environment do not necessarily relate to that of a particular organism and ecological characteristics of land adjacent to patches of natural vegetation (‘remnants’) may influence the ecological processes within. We investigated how the distribution and abundance of resources within and surrounding 39 small remnants located within the city of Melbourne, Australia, influenced the abundance of common brushtail possums Trichosurus vulpecula (Phalangeridae) and common ringtail possums Pseudocheirus peregrinus (Pseudocheiridae), two primarily folivorous marsupials. Bayesian modelling techniques were used to relate the abundance of both possum species to estimates of den and food availability both within the remnant and within a 100‐m buffer strip extending out into adjacent residential development. We found that both brushtail and ringtail possum abundance within remnants increased with the density of potential den sites within the remnant and food availability within the surrounding landscape. Ringtail possum density within the remnant further increased with den availability within the surrounding landscape. Our results lend support to the hypothesis that, in highly modified landscapes, processes originating outside a remnant vegetation patch may influence the abundance of species within.     

Weeds as a predominant food source: a review of the diet of common hamsters Cricetus cricetus in farmlands and urban habitats

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What physiological processes permit insects to eat Eucalyptus leaves?

Many species of insects eat Eucalyptus foliage despite its relatively low nutritional value and the many plant secondary metabolites (PSMs) present, for example, terpenes, phenols and formylated phloroglucinols (FPGs). Formylated phloroglucinols are a new class of PSMs that act as antifeedants for possums and koalas. What physiological processes are present that permit insects to eat eucalypt foliage and how do PSMs influence insect feeding or digestion? Some trees seem to be repeatedly infested with eucalypt‐feeding insects, possibly as a result of previous chemosensory cues remaining from parental selection of a plant. Avoidance or storage of PSMs permit jarrah leafminers (Perthida glyphopa) and sawflies (Perga sp.) to consume eucalypt foliage without dealing with the majority of these compounds. Some PSMs can be metabolized by polysubstrate membrane oxidases as found in caterpillars or sawflies that feed on eucalypts. High midgut pH may be advantageous for nutrient extraction and PSM metabolism, and midgut pH ranges between 8.5 and 8.9 for caterpillars of Hyalarcta huebneri. Plant secondary metabolites may not be absorbed as a result of the combined presence of the peritrophic matrix and endogenous surfactants. Excretion of PSMs can be as metabolites or intact compounds. Both putative metabolites and sideroxylonal‐A, an FPG, are present in the faeces of larvae of the case moth, H. huebneri. The presence of sideroxylonal‐A in the food had an effect on the presence of 5‐hydroxytryptamine (5HT) in the central nervous system of caterpillars, as larvae fed leaves with a high concentration of sideroxylonal‐A had relatively more 5HT in the brain and central nervous system ganglia than larvae fed leaves containing a low concentration. Further work is necessary to clarify how PSMs are handled by eucalypt‐feeding insects and what effect FPGs have on feeding and digestion.     

Nutritional Correlates of Koala Persistence in a Low-Density Population

It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.     

The role of phytochemistry in dietary choices of Tana River red colobus monkeys(Procolobus badius rufomitratus)

We conducted a phytochemical survey of tree species growing within the riverine forests of the Tana River National Primate Reserve in Kenya to understand better the feeding ecology of an endangered resident primate, the Tana River red colobus monkey (Procolobus badius rufomitratus).Young leaves, which make up a large percentage of this monkey's diet, are significantly higher in nitrogen and lower in acid detergent fiber than more abundant mature leaves are. Phenolic chemistry had little inhibitory effect on feeding by P. b. rufomitratus.Choice among tree species by P. b. rufomitratusappears to be influenced largely by leaf availability,once an acceptable threshold of nitrogen and fiber is reached When mature leaves are eaten, they selected species that are high in nitrogen and low in fiber. A significantly higher nitrogen content was found for the mature leaves of all leguminous versus nonleguminous tree species. Consequently, the availability of certain types of mature leaf species during periods of preferred food scarcity may prove critical to groups of Tana River red colobus monkeys.     

Comparative dietary ecology of two congeneric marsupial folivores

Knowledge of species diets is critical to assisting our understanding of their ecology. Using microhistological analysis of faecal samples, we described and compared the diets of sympatrically occurring folivorous congenerics, common and mountain brushtail possums (Trichosurus vulpecula and T. cunninghami, respectively). Throughout the 28‐month study period, common brushtails relied heavily on eucalypt foliage, particularly very young leaves, which is consistent with data from captive studies on their dietary physiology. In contrast, eucalypt foliage formed only a small part of the diet of mountain brushtails, which instead relied heavily on silver wattle foliage. The mean number of plant groups per faecal sample was significantly greater for common brushtails than mountain brushtails. No significant differences in diet between male and female mountain brushtails were detected. However, intraspecific differences in diet occurred for common brushtails: the diet of females included significantly less eucalypt foliage and significantly more foliage of the exotic, tree lucerne, than that of males during the Wet Season (April–November), but not during the Dry Season (December–March). Diets varied temporally for both species, with some individuals feeding on seasonally available resources. The diets described for common and mountain brushtails are consistent with those of a dry‐adapted and mesic‐adapted species, respectively. We discuss how our results contribute to our understanding of the evolutionary history of both study species, and more broadly the family Phalangeridae to which they belong. We also consider the diet of our study species in the context of recent advances in our understanding of interactions between plants that produce secondary metabolites, and mammals specialized to feed on them.