Youbing Zhou

DIETARY SHIFTS IN RELATION TO FRUIT AVAILABILITY AMONG MASKED PALM CIVETS (PAGUMA LARVATA) IN CENTRAL CHINA

Abstract The spatial and temporal distribution of food resources can profoundly affect foraging decisions and prey selection, potentially resulting in shifts in diet in response to changes in resource availability. The masked palm civet (Paguma larvata) has long been regarded as a dietary generalist that feeds primarily on fruits and small mammals. Both types of food resources may vary spatially and temporally and the diet of P. larvata is expected to change in response to variation in the availability and distribution of these resources. To address the effects of such variation on foraging by masked palm civets, we studied a population of P. larvata inhabiting a highly heterogeneous habitat in central China consisting of primary forest, selectively logged forest, logged forest, broad-leaved and coniferous forest plantations, and cultivated farmland. Available food resources included wild fruits, cultivated fruits, leaves, plant cortexes, amphibians, reptiles, birds, small mammals, molluscs, and arthropods. The abundance of these food categories varied significantly among seasons and habitats and civets altered consumption of these categories according to their temporal and spatial availability. The diversity of items consumed also varied significantly among seasons and habitats. From June to October, wild fruits were the main food of civets in forest habitats, whereas cultivated fruits were the main food in farmland. In contrast, from November to May, civets in forested habitats consumed primarily rodents and birds. Concordant with these changes was a shift from foraging in primary forest (November–May) to foraging in logged forest and farmland (June–October) that appeared to be associated with the availability of fruits. These results demonstrate the ability of civets to change their diet, both spatially and temporally, in response to changing food resources. To better understand how foraging behavior of civets varies with resource availability, similar studies should be conducted in tropical environments characterized by year-round availability of fruit.

Frugivory and seed dispersal by the yellow-throated marten, Martes flavigula , in a subtropical forest of China

The yellow-throated marten, Martes flavigula, is the only living species of the genus Martes found in subtropical and tropical forests (Harrison et al. 2004). It is distributed throughout central and southern Asia in a wide variety of habitats. Despite its extensive geographical range, the ecology and behaviour of this species has so far received little attention, aside from a study of habitat use (Grassman et al. 2005). Studies on other martens have shown that fruits are an important food resource (e.g. M. martes, Bermejo & Guitian 2000; M. foina, Pandolfi et al. 1996). Thus, they are considered to be important potential seed dispersers (Corlett 1998, Herrera 1989, Willson 1993), as confirmed by recent studies (M. melampus, Otani 2002; M. americana, Hickey et al. 1999; M. foina and M. martes, Schaumann & Heinken 2002). Although no systematic study of the diet of M. flavigula has been conducted (Harrison et al. 2004), it is known to be omnivorous and to consume fruit (Gao & Wang 1987). To date, however, there has been no comprehensive study of frugivory and seed dispersal by M. flavigula (but see Corlett 1998).

Diet of an opportunistically frugivorous carnivore, Martes flavigula, in subtropical forest

Abstract In response to foraging for foods that fluctuate in availability, generalists often exhibit the ability to switch between different food sources. Many of the Carnivora on an omnivorous–frugivorous diet display temporal dietary switching and specialism, but the mechanisms underlying this are incompletely understood. Here we studied the diet of the opportunistically frugivorous yellow-throated marten (Martes flavigula) with regard to food-resource exploitation in a subtropical forest of central China. Diet was determined through scat analyses combined with surveys to estimate local food abundance. Peak fruit consumption and the lowest utilization of small mammals occurred when fruit abundance reached its temporal maximum in the environment in synchrony with a concomitant peak in small mammal abundance. When both fruits and small mammals were least abundant in the environment, the martens diet shifted to the maximum utilization of small mammals with no fruit consumption. This dietary switching could not be explained by the fluctuation in the abundance of principal prey in the environment, that is, small mammals, but by the ease of procurement of fruit at peak fruiting season. The martens diet thus does not simply reflect primary resource abundance but is a function of the relative abundance and inferred availability of alternative food types. This case study of the yellow-throated marten provides insight into foraging strategies that depend on the relative, temporal availability of food types, a phenomenon observed for other generalist omnivores (including several Carnivora).

Contrasting Sociality in Two Widespread, Generalist, Mustelid Genera, Meles and Martes

Abstract. The genera Meles and Martes both belong to the family Mustelidae, both exhibit similar life history traits, ecology and foraging behaviour, and yet while Meles species are facultatively social, all Martes species are solitary. We compare and contrast the socio-biology of these two genera, establishing that as generalist omnivores both experience similar conditions of resource dispersion, but have intrinsic differences in their morphological and physiological capacity to exploit resources. The rotund body-type of badgers predisposes them to be able to tolerate conditions of restricted food security, by buffering periods of scarcity with increased body-mass. Badgers also use torpor to cope with seasonal food scarcity, and conserve energy by remaining within complex subterranean dens. Martens, in contrast, must maintain a lean, elongate body-type for effective hunting and thus do not store energy as increased body-mass to a comparable extent. Martens do not exhibit torpor and their dens are simple. We conclude that these differences prevent martens from being able to tolerate restricted food security; the type of precursive aggregation fundamental to the formation of social groups observed in badgers. We argue that the Japanese badger is transitionary in the development of integrated social organisation, forming spatial groups with extended juvenile philopatry.

Anomalous, extreme weather disrupts obligate seed dispersal mutualism: snow in a subtropical forest ecosystem

Ongoing global climate change is predicted to increase the frequency and magnitude of extreme weather events, impacting population dynamics and community structure. There is, however, a critical lack of case studies considering how climatic perturbations affect biotic interactions. Here, we document how an obligate seed dispersal mutualism was disrupted by a temporally anomalous and meteorologically extreme interlude of unseasonably frigid weather, with accompanying snowstorms, in subtropical China, during January-February 2008. Based on the analysis of 5892 fecal samples (representing six mammalian seed dispersers), this event caused a substantial disruption to the relative seed dispersal function for the raisin tree Hovenia dulcis from prestorm 6.29 (2006) and 11.47 (2007), down to 0.35 during the storm (2008). Crucially, this was due to impacts on mammalian seed dispersers and not due to a paucity of fruit, where 4.63 fruit per branch were available in January 2008, vs. 3.73 in 2006 and 3.58 in 2007. An induced dietary shift occurred among omnivorous carnivores during this event, from the consumption fruit to small mammals and birds, reducing their role in seed dispersal substantially. Induced range shift extinguished the functionality of herbivorous mammals completely, however, seed dispersal function was compensated in part by three omnivorous carnivores during poststorm years, and thus while the mutualism remained intact it was enacted by a narrower assemblage of species, rendering the system more vulnerable to extrinsic perturbations. The storms extended effects also had anthropogenic corollaries - migrating ungulates becoming exposed to heightened levels of illegal hunting - causing long-term modification to the seed dispersal community and mutualism dynamics. Furthermore, degraded forests proved especially vulnerable to the storms effects. Considering increasing climate variability and anthropogenic disturbance, the impacts of such massive, aberrant events warrant conservation concern, while affording unique insights into the stability of mutualisms and the processes that structure biodiversity and mediate ecosystem dynamics.

Peduncles elicit large-mammal endozoochory in a dry-fruited plant

BACKGROUND AND AIMS Plants have evolved a variety of seed dispersal mechanisms to overcome lack of mobility. Many species embed seeds in fleshy pulp to elicit endozoochory, i.e. disseminating seed through the animal gut. In contrast to well-studied fleshy fruited plants, dry-fruited plants may exploit this dispersal mutualism by producing fleshy appendages as a nutritional reward to entice animals to swallow their diaspores, but this has been little studied. In this study, it is hypothesized that these accessory fruits represent co-adaptations facilitating the syndrome of mammalian endozoochorous dispersal. METHODS Field observations (focal tree watches, faecal surveys and fruiting phenology) with experimental manipulations (examination of seed germination and feeding trials) were conducted over 2 years in a native population of the raisin tree, Hovenia dulcis, which produces enlarged, twisted brown peduncles with external black seeds, in central China. KEY RESULTS Birds were not observed to swallow seeds or carry infructescences away during 190 h of focal tree watches. However, H. dulcis seeds were detected in 247 faecal samples, representative of two herbivore and four carnivore mammalian species. Feeding trials revealed that peduncles attracted mammals to consume the entire infructescence, thereby facilitating effective seed dispersal. The germination rate of egested seeds proved higher than that of unconsumed seeds. It was also noted that this mutualism was most vulnerable in degraded forest. CONCLUSIONS Hovenia dulcis peduncle sets are confirmed to adapt primarily to mammalian endozoochory, a mutualistic association similar in function to fleshy pulp or foliage. This demonstrates that plant organ systems can be adapted to unique mutualisms that utilize animal dispersal agents. Such an ecological role has until now been attributed only to bird epizoochory. Future studies should consider more widely the putative role of peduncle sets and mammalian endozoochory as a dispersal mechanism, particularly for those plants that possess relatively large accessory fruits.

Ranging and Activity Patterns of the Group-Living Ferret Badger Melogale moschata in Central China

Patterns of space use can provide valuable insights into patterns of activity and social structure of poorly known mammal species. From April 2005 to November 2006 we radiotracked a low-density population of ferret badgers (Melogale moschata) in central China. Fourteen males and 8 females were caught. Nine of these individuals (6 males and 3 females) were followed; mean (± SD) 100% minimum convex polygon (MCP100) home range was 128.3 ± 131.9 ha, with no difference between sexes. For MCP100, neither nightly movement distances nor daily activity patterns revealed significant variation due to sex or season. Core areas (50% minimum convex polygon [MCP50]) were typically located centrally within overall home ranges. Two distinct groups of animals were evident in the radiotracked subpopulation, one consisting of 7 adults and the other composed of at least the 2 remaining collared badgers with field signs of additional badgers from the periphery of our study area. Within each group, home ranges of radiocollared individuals overlapped extensively (62.1% ± 26.5% for MCP100; 59.6% ± 23.0% for MCP95; 37.1% ± 24.5% for MCP50), and up to 4 adults per group shared the same burrow (sett). We consider the implications of our data for understanding of mustelid sociospatial behavior.

Seasonal dietary shifts and food resource exploitation by the hog badger ( Arctonyx collaris ) in a Chinese subtropical forest

Spatial and temporal fluctuations in the availability of food resources can affect adaptive foraging strategies substantially, with the potential to promote temporal dietary switching and specialisation among generalist carnivores. To understand this relationship better at the causal level, we examined spatial and temporal variation in diet composition and diversity in the hitherto little-known hog badger (Arctonyx collaris), in comparison to the environmental abundance of principal food resources, in a subtropical forest of central China. Here, hog badgers fed predominantly on earthworms and fruits, complemented with arthropod imagoes and invertebrate larvae, whereas vertebrate prey categories (mammals, birds and reptiles) were consumed infrequently. We observed strong seasonal variation in the consumption of different food categories. Earthworms predominated during spring, fruits in autumn, and earthworms, complemented by arthropods, in summer, with hog badgers apparently hibernating in winter. Fluctuation in dietary preferences between seasons and habitats correlated only partially with environmental food abundance; in autumn, when fruit abundance peaked, and despite a concomitant peak in earthworm abundance, hog badgers exhibited a dietary shift, indicating a preference for fruit, over earthworms. This resulted in autumnal minima in seasonal food niche breadth and evenness values. We conclude that, in this region, hog badgers exhibited a generalist diet but switched between food categories in response to changes in environmental seasonal abundance.

Niche overlap and sett-site resource partitioning for two sympatric species of badger.

Competition for resources can be a determining factor in whether similar species can co-exist. As an example of such intra-guild competition, we investigated sett (den)-site selection by two sympatric species of badger, the Chinese ferret badger (Melogale moschata) and the hog badger (Arctonyx collaris) in Houhe National Nature Reserve, central China. As members of the same guild we predicted that competition should occur between these species; and that their relationship along various niche dimensions should be affected by their five-fold difference in body size. We tested mechanisms facilitating coexistence in terms of sett sites at two spatio-temporal scales: (1) habitat selection; (2) internal den-microhabitat conditions. Logistic regression models revealed that ferret badgers selected sites characterized by dense, species-diverse shrub cover, low elevation and low tree cover. Discriminant function analysis revealed that these primary differences were attributable to slope angle, shrub cover and human activity. Niche overlap value, in terms of sett-site characteristics, was 0.359 (values in excess of 0.6 often limit viable coexistence). At the microclimatic scale, both the absolute, and range, of temperature values within setts also differed significantly between M. moschata and A. collaris. Our findings for these little-known, co-existing badger species provide evidence for two mechanisms (trade-off in relative abilities to exploit different habitats and microhabitat) facilitating niche separation, with regard to den site selection.

Spatial organization and activity patterns of the masked palm civet (Paguma larvata) in central-south China

Abstract Movement and activity patterns are important components of life history, being central to resource acquisition and defense, mating behavior, and individual survival and fitness. Here, we present results from the 1st systematic radiotracking study of the masked palm civet (Paguma larvata), a widespread viverrid found in subtropical and tropical forests of Asia. From June 2004 to November 2007, we radiotracked 12 masked palm civets (5 males and 7 females) in central-south China. Mean individual home-range size based on 95% minimum convex polygons was 192.6 ha ± 42.6 SE (range = 64–451 ha). Although males had larger mean home-range sizes than females (276.8 and 136.5 ha, respectively), these differences were not statistically significant. Males also exhibited greater daily movement distances and extents than females, but we found no evidence of sexual dimorphism in body size. Masked palm civets were predominantly nocturnal, but were active intermittently during the day. No significant seasonal (monthly) differences in daily activity patterns were apparent. We did, however, observe reduced hours of activity—but not continuous inactivity—during winter; consequently, we concluded that our study animals did not hibernate or semihibernate. We speculate that our observations of home-range overlap among individuals may indicate group living in the masked palm civet.