Exclusion of interspecific competition reduces scatter‐hoarding of Siberian chipmunk Tamias sibiricus: A field study

Although food availability and the abundance of seed predators have been postulated to affect seed dispersal, it is not clear how seed‐eating animals modify their scatter‐hoarding strategies in response to different levels of interspecific competition. We placed paired germinated and ungerminated acorns of Quercus mongolica on 30‐cm high platforms to exclude potential interspecific competition of the predominant larder hoarders Apodemus peninsulae and Myodes rufocanus, to investigate seed dispersal by a predominant scatter‐hoarder, Tamias sibiricus, in the field in north‐eastern China. Our results showed that T. sibiricus ate more acorns in situ in the absence of interspecific competition. In the presence of interspecific competition of A. peninsulae and C. rufocanus, however, more acorns were scatter‐hoarded by T. sibiricus. Regardless of interspecific competition, germination of acorns showed no significant effects on seed dispersal patterns, inconsistent with the “seed perishability hypothesis” that animals avoid hoarding seeds with high perishability. Exclusion of interspecific competition, though relatively increasing the per capita seed abundance, appears to reduce seed dispersal, scatter‐hoarding and seedling establishment. Therefore, we propose that moderate interspecific competition rather than competition exclusion may benefit seed scatter‐hoarding and seedling establishment.     

Differences in diet between two rodent species,Mastomys natalensis and Gerbilliscus vicinus,in fallow land habitats in central Tanzania

Differences in the ecological niche requirements among rodent species competing in the same habitat may result from differences in the use of one to three resources: space, time and food or some combination of these. Alternatively, differences in resource use utilization among animal species may simply reflect availability of food, and when food is limited, different animal species compete. In this study, the diet of two rodent pest species, Mastomys natalensis and Gerbilliscus vicinus, coexisting in fallow land in central Tanzania were studied to assess the degree of diet differentiation among them. Dietary niche breadth of G. vicinus was greater than that of M. natalensis in all stages of the maize cropping seasons. The rodent species studied overlapped considerably in the food items consumed ranging from niche overlap (O_jk) of 0.77–0.89. Grains/seeds featured high in the diet of M. natalensis while plant material occurrence was high in G. vicinus. These two food categories may have contributed to differences in diet partitioning, which may, in turn, facilitate their coexistence in fallow land.     

Temporal niche overlap among insectivorous small mammals

Being active in the same environment at different times exposes animals to the effects of very different environmental factors, both biotic and abiotic. In the present study, we used live traps equipped with timing devices to evaluate the potential role of biotic factors (competition and food abundance) on overall overlap in the temporal niche axis of 4 insectivorous small mammals in high‐elevation grassland fields (‘campos de altitude’) of southern Brazil. Based on resources availability (invertebrates), data on animal captures were pooled in 2 seasons: ‘scarcity’ (June 2001–September 2001) and ‘abundance’ (November 2001–May 2002) seasons. We tested for non‐random structure in temporal niche overlap among the species in each season. These species were the rodents Oxymycterus nasutus (Waterhouse, 1837), Deltamys sp., Akodon azarae (Fischer, 1829), and the marsupial Monodelphis brevicaudis Olfers, 1818. The studied community was mainly diurnal with crepuscular peaks. Simulations using the Pianka index of niche overlap indicated that the empirical assemblage‐wide overlap was not significantly different from randomly generated patterns in the abundance season but significantly greater than expected by chance alone in the scarcity season. All the species showed an increase in temporal niche breadth during the abundance season, which appears to be related to longer daylength and high nocturnal temperatures. Patterns on both temporal niche overlap and temporal niche breadth were the opposite to those that we were expecting in the case of diel activity patterns determined by competition for dietary resources. Therefore, we conclude that competition did not seem to be preponderant for determining patterns of temporal niche overlap by the studied community.     

Food habits and trophic resource partitioning among three mormyrid fishes from man-made Lake Ayame,Ivory Coast

Feeding habits and trophic relationships among three mormyrid species (Petrocephalus bovei, Marcusenius ussheri and Marcusenius furcidens) were assessed in the man-made Lake Ayame in Ivory Coast. The index of preponderance combining the occurrence and weight percentages of the identified prey items showed that these three mormyrid species mainly feed on invertebrates, especially aquatic insects. Petrocephalus bovei mainly feeds on chaoborid larvae, whereas both Marcusenius species preferentially feed on chironomid larvae. This segregation of food items associated with the relative abundance of chironomid larvae may reduce interspecific competition between these three fish species, and may therefore allow their coexistence. Horn’s food overlap index revealed highly significant similarities in the trophic spectrum between both Marcusenius species, and for the dry as well as the rainy season.     

Dietary patterns of two herbivorous rodents: Otomys unisulcatus and Parotomys brantsii in the Karoo

Differences and overlap in the diets of two sympatric, herbivorous rodents Otomys unisulcatus and Parotomys brantsii were investigated. Frequency of occurrence of plant species in the diets were compared with availability of the plants in the rodents' habitats. Both rodents are generalist herbivores, eating plants species in proportion to the availability in their habitats. Dietary patterns, diversity of diet and degree of overlap between rodent's diets are a function of food availability in the different habitats. It is suggested that these rodents separate niches on a spatial rather than trophic basis. Differences in dietary patterns are therefore not critical for niche separation but are the result of habitat segregation.     

Midsummer Trophic Overlap Between Guanaco and Sheep in Patagonian Rangelands

Diet overlap estimation among species is important to understand interspecific interactions. Through these interactions, one species may extinguish others through competition or adapt through mechanisms such as resource partitioning. The introduction of domestic herbivores in a native assemblage may introduce competition for resources with wild herbivores. In southern Patagonian steppes, guanaco (Lama guanicoe) populations are increasing after a drastic demise during the past century. This is occurring in protected areas and extensive ranching areas for sheep, and in the latter ranchers have rising concerns regarding competition. In this observational study, we measured diet overlap, food selection and preferences, and niche width for guanaco and sheep to compare use of food resources during the summer season. Feces were analyzed through microhistological technique to determine sheep and guanaco diets. Diets of guanaco and sheep were dominated by tussock grass (Festuca gracillima, sheep > 60%, guanaco > 50%), the most abundant plant species. Although food niche widths, measured through Levin’s Index, were narrow, guanaco presented the broadest niche (P < 0.001). Of the 17 identified plant species present in guanaco and sheep diets, 5 were always selected by both ungulates and 1 was always avoided at the four study sites. Overlap between diets was high (> 0.90), evidencing potential competition. In addition, diet overlap coupled with our results of small variation in use and selectivity of food resources suggest the absence of resource partitioning. Therefore, both species might share resources or coexist, possibly due to high availability or spatial distribution of food resources and guanaco resilience to cope with numerically dominant competition from sheep. These findings offer new insight into the understanding of these species’ interactions. It is also a management challenge to emerging wild and domestic herbivores interactions, as well as livestock production concerns at large.     

Asymmetric competition for seeds between two sympatric food hoarding rodents: implications for coexistence

Asymmetric competition occurs when some species have distinct advantages over their competitors and is common in animals with overlapping habitats and diet. However, the mechanism allowing coexistence between asymmetric competitors is not fully clear. Chinese white-bellied rats (Niviventer confucianus, CWR) and Korean field mice (Apodemus peninsulae, KFM) are common asymmetric competitors in shrublands and forests west of Beijing city. They share similar diet (e.g. plant seeds) and activity (nocturnal), but differ in body size (CWR are bigger than KFM), food hoarding habit (CWR: mainly larder hoarding; KFM: both larder and scatter hoarding), and ability to protect cached food (CWR are more aggressive than KFM). Here, we tested seed competition in 15 CWR–KFM pairs over a 10-day period under semi-natural enclosure conditions to uncover the differences in food hoarding, cache pilferage, and food protection between the 2 rodents, and discuss the implication for coexistence. Prior to pilferage, CWR harvested and ate more seeds than KFM. CWR tended to larder hoard seeds, whereas KFM preferred to scatter hoard seeds. Following pilferage, CWR increased consumption, decreased intensity of hoarding, and pilfered more caches from KFM than they lost, while KFM increased consumption more than they hoarded, and they preferred to hoard seeds in low and medium competition areas. Accordingly, both of the 2 rodent species increased their total energy consumption and hoarding following pilferage. Both rodent species tended to harvest seeds from the source, rather than pilfer caches from each other to compensate for cache loss via pilferage. Compared to CWR, KFM consumed fewer seeds when considering seed number, but hoarded more seeds when considering the seeds’ relative energy (energy of hoarded seeds/rodent body mass^2/3) at the end of the trials. These results suggest that asymmetric competition for food exists between CWR and KFM, but differentiation in hoarding behavior could help the subordinate species (i.e. KFM) hoard more energy than the dominant species (i.e. CWR), and may contribute to their coexistence in the field.     

Seasonal variations in the diet and food selection of the Algerian hedgehog Atelerix algirus

The Algerian hedgehog Atelerix algirus is an insectivorous species. However, the exact composition of its natural diet remains largely undetermined, especially in relation to seasonal variations in food availability. From March to November, we simultaneously analysed the composition of 180 hedgehog faecal samples and food availability in the Soumman Valley, Algeria to assess food selection in this species. The faeces contained 196 different prey species, of which 92% belonged to the class Insecta. The highest prey species diversity was found in the Coleoptera order (100 species recorded) and the highest species occurrence was found in Hymenoptera (65% of the prey items, mainly represented by the harvester ant Messor barbarus, a crop-ravaging species). This study shows that the Algerian hedgehog is mainly a generalist species with a diet that is strongly linked to food availability. However, seasonal variations were observed in prey selection, and a notable shift in food preference was observed during autumn. The exact nature of these changes in feeding behaviour remains to be investigated, notably in relation to changes in energy requirements of this species before hibernation, in terms of quantity and/or quality.     

Comparative morphology of the feeding appendages of four mesozooplankton species in the Sundays River estuary

The morphology of feeding appendages of the coexisting estuarine copepods, Pseudodiaptomus hessei and Acartia longipatetla, and mysids, Rhopalophthalmus terranatalis and Mesopodopsis wooldridgei. were examined and compared as an aid in elucidating dietary differences. The robust mandibles of P. hessei copepodids compared to the more pointed and slender teeth with no molar region, of A. longipatella suggest that the latter species relies on more fragile food particles. Mandible edge indices indicate, however, omnivorous feeding by both species. No clear dietary differences could be deduced from the dimensions of the second maxillae of these copepods. Mandible edge indices calculated for the mysid species suggest a more herbivorous feeding mode in M. wooldridgei and a more carnivorous one in R. terranatalis, supporting previous studies on their diets. No interspecific differences between the mysid size classes were evident from edge indices. Significant increments in setae and setule lengths and spacing with increasing mysid size class were evident, reflecting differences in food particle sizes utilized. The morphological differences in the feeding apparatus could reflect differences in the diets between species and indicate differences in food particle sizes utilized by the various developmental stages within species. These differences in diet should reduce inter- and intraspecific competition.     

Dietary regimen of the woodpigeon (Columba palumbus)

Recently, new agricultural policies and European Directives brought to important changes in farming practice, some of which could affect food availability for the wild bird population endangering biodiversity. This study aims to evaluate the consequences of such agricultural changes in France on the woodpigeon's dietary regimen. A total of 1,093 woodpigeons were collected over a four-year period (2014–2017). Voluntary sampling was performed in six regions in the south-west of France by local hunters during this species’ autumnal migration and wintering. Ingluvies contents were recovered, macroscopically and microscopically identified, and then weighed before and after drying. Five food groups were identified: acorns, corn, green plant material, cultivated seeds and others. ANOVA testing followed by Tukey's test for multiple comparison were performed (R version 3.5.2). Significance was set at p < .05. A total of 762 woodpigeons met the study's inclusion criteria. Mean weight of total crop contents was less of 9 grams of dry matter. Most frequent food groups were “green plant material” (70.3%), acorns (42.3%) and corn (27.2%). In terms of grams of dry matter, the most important food in the crop content were acorns (62%): these were eaten more during the first two hunting seasons (p < .001), and in region A, lower amount was consumed compared to all other regions. On the contrary, corn intake peaked during the third year (p < .001), and in region A, birds had an increasing intake of this cereal. Cultivated seeds contributed to the diet more during migration (p = .007), while “green plant material” and others more during wintering (p = .011; p = .004). In conclusion, results confirm the opportunistic nature of the woodpigeon, balancing its diet according to food availability. Corn was eaten more in areas where the winter burying of chopped maize stover (mulching), provided by the Nitrate's directive, was in derogation.     

Effects of insect infestation on rodent‐mediated dispersal of Quercus aliena: results from field and enclosure experiments

Rodents influence plant establishment and regeneration by functioning as both seed predators and dispersers. However, these rodent–plant interactions can vary significantly due to various environmental conditions and the activity of other insect seed predators. Here, we use a combination of both field and enclosure (i.e. individual cage and semi‐natural enclosure) experiments, to determine whether rodents can distinguish sound seeds from those infested with insects. We also demonstrate how such responses to insects are influenced by food abundance and other environmental factors. We presented rodents with 2 kinds of Quercus aliena seeds (sound and insect‐infested seeds) in a subtropical forest in the Qinling Mountains, central China, from September to November of 2011 to 2013. The results showed that rodents preferred to hoard and eat sound seeds than infested seeds in the field and semi‐natural enclosure, while they preferred to eat infested seeds over sound seeds in the individual cages. In addition, both hoarding and eating decisions were influenced by food abundance. Rodents hoarded more sound seeds in years of high food abundance while they consumed more acorns in years of food shortage. Compared with field results, rodents reduced scatter‐hoarding behavior in semi‐natural enclosures and ate more insect‐infested seeds in smaller individual cages. These results further confirm that rodents distinguish infested seeds from non‐infested seeds but demonstrate that this behavior varies with conditions (i.e. environment and food abundance). We suggest that such interactions will influence the dispersal and natural regeneration of seeds as well as predation rates on insect larvae.     

Temporal Variation in Diet and Nutrition of Preincubating Greater Sage-Grouse

Greater sage-grouse (Centrocercus urophasianus) habitat management involves vegetation manipulations to increase or decrease specific habitat components. For sage-grouse habitat management to be most effective, an understanding of the functional response of sage-grouse to changes in resource availability is critical. We investigated temporal variation in diet composition and nutrient content (crude protein, calcium, and phosphorus) of foods consumed by preincubating female sage-grouse relative to food supply and age of hen. We collected 86 preincubating female greater sage-grouse at foraging areas during early (18–31 March) and late (1–12 April) preincubation periods during 2002–2003. Females consumed 22 food types including low sagebrush (Artemisia arbuscula Nutt.), big sagebrush (Artemisia tridentata Nutt.), 15 forb species, 2 insect taxa, sagebrush galls, moss, and a trace amount of unidentified grasses. Low sagebrush was the most common food item, but forbs were found in 89% of the crops and composed 30.1% aggregate dry mass (ADM) of the diet. ADM and species composition of female diets were highly variable between collection periods and years, and coincided with temporal variation in forb availability. Adult females consumed more forbs and less low sagebrush compared to yearling females. Because of higher levels of crude protein, calcium, and phosphorus, forbs were important diet components in comparison with low sagebrush, which had the lowest nutrient content of all foods consumed. Our results indicate that increased forb abundance in areas used by female sage-grouse prior to nesting would increase their forb consumption and nutritional status for reproduction. We recommend that managers should emphasize delineation of habitats used by preincubating sage-grouse and evaluate the need for enhancing forb abundance and diversity.     

Comparative behaviour and ecology of two sympatric mongoose species (Cynictis penicillata and Galerella pulverulenta)

The activity, movements, home range size, habitat selection, social structure, density, pattern of faeces deposition, anti-predator behaviour, diet, and availability and distribution of the main food sources of two mongoose species [the yellow mongoose Cynictis penicillata and the Cape grey mongoose Gaierelia pulverulenta (= Herpestes pulverulentos) in a coastal area of South Africa are compared, Both species were diurnal. Galerella did not use dens, whereas Cynictis never rested outside a den. Total distance moved, home range size and density did not differ between the two species. Galerella frequented bush, whereas Cynictis frequented open fields. The yellow mongoose was more social than the grey mongoose, but the basic social structure was similar. Faeces of Cynictis were found in large clumps close to the dens, while those of Galerella were more scattered. This parallels the greater constancy of use of the sleeping sites by Cynictis. Rodents (> 90% of Cape grey mongoose diet) were much more abundant in the bush, while availability of insects (main food source for the yellow mongoose) was higher in the open fields. Habitat selection, Ihrough its effects on anti-predator and feeding strategies, might have been the leading factor in the evolution of sociality in herpestids.     

How seed defense and seed abundance predict dispersal and survival patterns in Camellia

Little is known about how seed defense and seed abundance interact with behavioral responses of seed dispersers to predict dispersal and survival dynamics in animal‐dispersed plants. By tracking the fate of individual seeds in Camellia stands with high and low seed abundance in Southwest China in 2007, we investigated the dispersal and survival of 2 high‐saponin Camellia species (Camellia oleifera and Camellia sinensis and 1 non‐saponin species (peanut Arachis hypogaea) as a control. Saponins in Camellia seeds are chemical compounds that act as seed defense. Our results were most consistent with the predictions based on the predator satiation hypothesis and the plant defense hypothesis. At the abundant Camellia stand (predators and dispersers were satiated), more Camellia seeds survived at the source but fewer were hoarded and survived at cache sites. At the sparse Camellia stand (predators and dispersers were not satiated), no Camellia seeds survived at the source, but more Camellia seeds were hoarded and survived at cache sites. Unlike Camellia seeds, no peanuts survived at the source at both stands, while more peanuts were hoarded and then survived at cache sites in the abundant Camellia stand compared to none at the sparse Camellia stand. In addition, the 2 Camellia species showed similar trends for seed fates across different dispersal stages. Our study indicates that the combined effects of seed abundance and seed defense, compared to their separate effects, provide a more accurate prediction for dispersal and survival patterns in animal‐dispersed Camellia species.     

Influence of food availability,plant productivity,and indigenous forest use on ranging behavior of the endangered samango monkey (Cercopithecus albogularis schwarzi), in the Soutpansberg Mountains,South Africa

Understanding the determinants of ranging patterns in species susceptible to habitat fragmentation is fundamental for assessing their long‐term adaptability to an increasingly human‐dominated landscape. The aim of this study was to determine and compare the influence of ground‐based food availability, remotely sensed plant productivity, and indigenous forest use on the ranging patterns of the endangered samango monkey (Cercopithecus albogularis schwarzi). We collected monthly ranging data on two habituated samango monkey groups, from February 2012 to December 2016, from our field site in the Soutpansberg Mountains, South Africa. We used linear mixed models to explore how food availability, plant productivity, and indigenous forest use influenced monthly ranging patterns, while controlling for group size, number of sample days and day length. We found that as more areas of high plant productivity (derived from remotely sensed EVI) were incorporated into the ranging area, both total and core monthly ranging areas decreased. In addition, both total ranging area and mean monthly daily path length decreased as more indigenous forest was incorporated into the ranging area. However, we found no effect of either ground‐based food availability or remotely sensed plant productivity on ranging patterns. Our findings demonstrate the behavioral flexibility in samango monkey ranging, as samangos can utilize matrix habitat during periods of low productivity but are ultimately dependent on access to indigenous forest patches. In addition, we highlight the potential of using remotely sensed areas of high plant productivity to predict ranging patterns in a small ranging, forest‐dwelling guenon, over ground‐based estimates of food availability.     

Fluctuation in seed abundance has contrasting effects on the fate of seeds from two rapidly germinating tree species in an Asian tropical forest

The seed predator satiation hypothesis states that high seed abundance can satiate seed predators or seed dispersers, thus promoting seed survival. However, for rapidly germinating seeds in tropical forests, high seed abundance may limit dispersal as the seeds usually remain under parent trees for long periods, which may lead to high mortality due to rodent predation or fungal infestations. By tracking 2 species of rapidly germinating seeds (Pittosporopsis kerrii, family Icacinaceae; Camellia kissi, family Theaceae), which depend on dispersal by scatter‐hoarding rodents, we investigated the effects of seed abundance at the community level on predation and seed dispersal in the tropical forest of Xishuangbanna Prefecture, Southwest China. We found that high seed abundance at the community level was associated with delayed and reduced seed removal, decreased dispersal distance and increased pre‐dispersal seed survival for both plant species. High seed abundance was also associated with reduced seed caching of C. kissi, but it showed little effect on seed caching of P. kerrii. However, post‐dispersal seed survival for the 2 plant species followed the reverse pattern. High seed abundance in the community was associated with higher post‐dispersal survival of P. kerrii seeds, but with lower post‐dispersal survival of C. kissi seeds. Our results suggest that different plant species derive benefit from fluctuations in seed production in different ways.     

Distribution and ecology of lesser pouched rat,Beamys hindei,in Tanzanian coastal forests

The lesser pouched rat, Beamys hindei, is a small rodent that is patchily distributed in the Eastern Arc Mountains and coastal forests in East Africa. The ecology of this species and its current distribution in coastal forests is not well known. Therefore, we conducted a study in selected coastal forests to assess the current distribution of the species and to investigate the population ecology in terms of abundance fluctuations and demographic patterns. Assessments of the species distribution were conducted in 5 forests through trapping with Sherman live traps. Data on ecology were obtained from monthly capture–mark–recapture studies conducted for 5 consecutive nights per month in two 1 ha grids set in Zaraninge Forest over a 2‐year period. The results indicate the presence of B. hindei in 3 forests where it was not previously recorded. The population abundance estimates ranged from 1 to 40 animals per month, with high numbers recorded during rainy seasons. Reproduction patterns and sex ratios did not differ between months. Survival estimates were not influenced by season, and recruitment was low, with growth rate estimates of 1 animal per month. These estimates suggest a stable population of B. hindei in Zaraninge Forest. Further studies are recommended to establish the home range, diet and burrowing behavior of the species in coastal forests in East Africa.     

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake (RFI) offered contrasting diets

Background

Methane (CH₄) emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency. The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake (RFI) while offered (i) a low energy high forage (HF) diet followed by (ii) a high energy low forage (LF) diet. Ruminal fluid was collected from 14 high (H) and 14 low (L) RFI animals across both dietary periods. Quantitative real time PCR (qRT-PCR) analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes. Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance, rumen fermentation variables and diet digestibility.

Results

Abundance of methanogens, did not differ between RFI phenotypes. However, relative abundance of total and specific methanogen species was affected (P < 0.05) by diet type, with greater abundance observed while animals were offered the LF compared to the HF diet.

Conclusions

These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH₄ emissions between efficient and inefficient animals, however dietary manipulation can influence the abundance of total and specific methanogen species.     

Fruit availability,frugivore satiation and seed removal in 2 primate‐dispersed tree species

During a mast‐fruiting event we investigated spatial variability in fruit availability, consumption, and seed removal at two sympatric tree species, Manilkara bidentata and M. huberi (Sapotaceae) at Nouragues Natural Reserve, French Guiana. We addressed the question of how Manilkara density and fruits at the community level might be major causes of variability in feeding assemblages between tree species. We thus explored how the frugivore assemblages differed between forest patches with contrasting relative Manilkara density and fruiting context. During the daytime, Alouatta seniculus was more often observed in M. huberi crowns at Petit Plateau (PP) with the greatest density of Manilkara spp. and the lowest fruit diversity and availability, whereas Cebus apella and Saguinus midas were more often observed in M. bidentata crowns at both Grand Plateau (GP), with a lowest density of M. bidentata and overall greater fruit supply, and PP. Overall, nearly 53% and 15% of the M. bidentata seed crop at GP and PP, respectively, and about 47% of the M. huberi seed crop were removed, otherwise either spit out or defecated beneath trees, or dropped in fruits. Small‐bodied primates concentrated fallen seeds beneath parent trees while large‐bodied primate species removed and dispersed more seeds away from parents. However, among the latter, satiated A. seniculus wasted seeds under conspecific trees at PP. Variations in feeding assemblages, seed removal rates and fates possibly reflected interactions with extra‐generic fruit species at the community level, according to feeding choice, habitat preferences and ranging patterns of primate species.