Diets of Two Lemur Species in Different Microhabitats in Beza Mahafaly Special Reserve,Madagascar

Studies of primate diets usually focus on differences that distinguish species or populations. However, variation in diet can occur at a more local level of groups within a population, especially in a non-homogeneous habitat. I compared dietary variation in food composition and toughness across groups of 2 lemur species in Beza Mahafaly special reserve, Madagascar. Beza Mahafaly contains an 80-ha reserve (Parcel 1) that, while small, hosts a dense population of Lemur catta (ring-tailed lemurs) and Propithecus verreauxi verreauxi (sifakas). Microhabitats in the eastern vs. western sides of the parcel are structurally and floristically distinct. Sifakas in this parcel have small, discrete home ranges and are morphological folivores. For these reasons, I expected that the 6 groups studied would eat a different menu of food plants but with similar toughness values. Ring-tailed lemurs have comparatively large, overlapping home ranges, and I expected that the 5 study groups would eat similar foods. Despite living in different microhabitats across the parcel, sifakas exhibit high dietary uniformity both in dietary plant species composition and the toughness of the foods. Food selection in sifakas operates on two distinct levels. Sifaka groups share many key food species that appear independent of local abundances, but the ranking of the foods within each group appears related to availability. Ring-tailed lemur groups are more heterogeneous in the composition of their diets relative to sifakas, though the time spent feeding on individual foods reveals a marked preference for the fruits of Tamarindus indica by all groups. Food toughness is consistent across the parcel with the exception of the most western group. Ring-tailed lemurs are highly specific feeders, but indiscriminate nibblers. Sifakas are targeted, balanced feeders. There does not appear to be a consistent microhabitat effect operating across species. Differences within sifaka and ring-tailed lemur populations in food composition and toughness, however, correspond to an east-west microhabitat gradient. Measures of dietary flexibility must take into account not only the plant species consumed and the different parts eaten but also their associated food properties and proportion of time spent feeding on them.     

Xanthogranuloma of the choroid plexus in the fat-tailed dwarf lemur (Cheirogaleus medius)

This report documents the death of two fat-tailed dwarf lemurs (Cheirogaleus medius) maintained over 6 years each in our laboratory. Postmortem studies revealed xanthogranuloma of the choroid plexus, a mass replete with stored lipids, including cholesterol crystals. Six months prior to their deaths, both animals developed a peculiar head tilt and signs suggestive of neurological dysfunction. At autopsy, each had masses projecting into the lateral and IVth ventricles and an associated obstructive hydrocephalus. Cryostat sections of the brains of both lemurs showed histological features consistent with xanthogranuloma of the choroid plexus, a histologically benign and usually asymptomatic lesion found in up to 7% of human autopsies. This case is of special interest because of the unique feeding strategies in the fat-tailed dwarf lemur. Since C. medius remains in torpor for 6 months out of the year during the time of food scarcity in the forests of Madagascar, the animal must accumulate large reserves of fat during its active period. In the laboratory, however, dwarf lemurs do not normally go into torpor, and the accumulated fat is not used. The finding of this tumor, therefore, suggests that the combination of a captive high-fat diet and the unusual fat-storage mechanisms utilized by C. medius contributed to the buildup of lipids and might be etiologically related to the development of those lesions. © 1996 Wiley-Liss, Inc.     

Variation in dietary patterns among and within polyphagous grasshopper species (Orthoptera: Acrididae)

Individuals of two polyphagous grasshopper species,Melanoplus differentialis andSchistocerca albolineata, were reared under standardized conditions to eliminate prior experience as an influence on feeding behavior. Individuals were offered four plants in simultaneous choice tests from 8 to 14 times during development to adulthood. Individual insects varied in the preferred plant and the strength of preference, in the strength of the preference hierarchy among the four plants, and in breadth of feeding in choice tests. Average feeding diversity in choice tests increased significantly in later instars, but the sexes did not differ in feeding pattern. In both species a significant preference for one plant was generally but not invariably associated with a consistent preference hierarchy. Breadth of feeding in all tests was inversely related to the strength of preference and of the preference hierarchy. Although the two species differed in feeding diversity and in the relationship between preference and strength of preference hierarchy, evidence suggests that these differences were due to the specific plants used rather than to true interspecific differences. The existence of such variation under highly standardized rearing conditions suggests that genetic variation for these characteristics may exist in natural populations of polyphagous grasshoppers.     

Varying patterns of coexistence of two mouse lemur species (Microcebus ravelobensis and M. murinus) in a heterogeneous landscape

The coexistence of closely related species is not easily understood on the basis of ecological theories. This study investigates the extent of coexistence of two congeneric species of Microcebus murinus (MUR) and M. ravelobensis (RAV) in northwestern Madagascar. Their presence and local relative population densities were determined by capturing and nocturnal transect counts and compared at 22 study sites in the Ankarafantsika National Park. All sites were characterized with regard to their altitude, access to surface water, and 19 structural vegetation characteristics. RAV and MUR were not equally distributed over this regional scale. RAV occurred in more sites and at higher maximum densities than MUR. The relative population densities of both species were significantly and negatively correlated with each other. Whereas the relative population densities of MUR increased with altitude and were highest in dry habitats far from surface water, the relative population densities of RAV generally decreased with altitude and were highest in low altitude habitats close to surface water. The results of the vegetation characteristics also reflect these general trends. The divergent pattern of local and regional coexistence of these two species is discussed and can be best explained either by the existence of a spatially heterogeneous competitive environment or by independent evolutionary pathways in different historic environments. Am. J. Primatol. 71:928–938, 2009. © 2009 Wiley‐Liss, Inc.     

Competition for dietary fructose between Moniliformis (acanthocephala) and growing rats

Crompton D. W. T., Singhvi A., Nesheim M. C. and Walters D. E. 1981. Competition for dietary fructose between Moniliformis (Acanthocephala) and growing rats. International journal for Parasitology11: 457–461. The food intake, weight gain and blood sugar of young rats, fed on diets containing growth-limiting amounts of fructose and infected with Moniliformis dubius (Acanthocephala) for 6 weeks, were measured and compared with values obtained from similar uninfected rats which had been treated in the same manner. The growth of the rats was closely related to the fructose content of the diet. However, on average, the infected rats gained less weight than their uninfected counterparts. Significant differences between the values for blood sugar from infected and uninfected rats were not detected when the diet contained 2% fructose. The blood sugar of infected rats fed on a diet containing 4% fructose was found to be significantly less than that of similar uninfected rats. Information was also obtained about the numbers, sex, dry weight and location of the Moniliformis in the small intestines of their hosts. Male and female Moniliformis from rats fed on the 4% fructose diet were found to be heavier than those from rats fed on the 2% fructose diet. The results can be interpreted to suggest that the reduction in the growth rate of the infected rats is due to competition for fructose between Moniliformis and the rat.     

Relative efficiency of preferred and nonpreferred patterns of lateralized foraging in the gentle lemur (Hapalemur griseus)

Lateralized patterns of hand use in species-typical bamboo shoot foraging were evaluated for efficiency in five female and six male gentle lemurs (Hapalemur griseus sp.). Efficiency was defined as amount of time required to complete a foraging response sequence. The foraging pattern consisted of four component movements: PULL-IN, COUNTERFORCE, TURN, and FEED-IN. These component movements had been shown in a previous study to incorporate lateral hand biases that formed subsets of patterns that were characteristic for each gentle lemur. The duration of each foraging sequence was measured from the beginning of the first component to the initiation of the terminal component. Frequency of use scores were employed to divide the pattern sequences of each subject into preferred and nonpreferred categories. A within-subjects comparison of the mean durations of preferred patterns (M = 2.56 sec) with those of non- preferred patterns (M = 3.02 sec) found that preferred patterns were executed more rapidly, t(10) = 3.36, P = .007. A multiple regression showed that order of pattern preference accounted for 89% of the variance in mean duration of response time (R² = .89, P = .056). Thus, the use of preferred lateralized hand patterns resulted in more rapid bamboo shoot harvesting. Speed in foraging may be regarded as an adaptive strategy for a species that subsists on a high bulk, low nutrient density food such as bamboo. © 1995 Wiley-Liss, Inc.     

Foraging patterns and dietary mixing in the field by the generalist grasshopperBrachystola magna (Orthoptera: Acrididae)

The foraging behavior of a cryptic romaleine grasshopper was observed in its natural habitat in southern Arizona. Individual polyphagy, dietary mixing, and the pattern of feeding on different substrates were monitored. Individuals were found to be extreme generalists with surprising levels of feeding on other insects. Differences in the foraging behavior between grasshopper species are discussed in relation to the habitat, the season, and the different defensive strategies.     

Control of Penicillium roqueforti (Thom) infection in cultures of Drosophila melanogaster (Meigen) (Diptera: Drosophilidae)

Abstract  Microbial contamination of artificial insect food media can jeopardise the viability, productivity and survival of many insect cultures, including Drosophila melanogaster . Here we investigated and improved upon control methods for one common contaminant, Penicillium roqueforti . We found that the combined effect of methyl p -hydroxybenzoate (23.7 mM), propionic acid (67.5 mM) and sorbic acid (8.9 mM) (PS^NPS treatment) was the most effective of the four candidate treatments, at inhibiting the growth of P. roqueforti. PS^NPS treatment inhibited 100% of visible P. roqueforti growth for 21 days (a complete D. melanogaster life cycle) and thus reduced the risk of transmitting infection to the next generation. Although the PS^NPS treatment negatively affected the two D. melanogaster fitness components, survivorship (number of adults) and biomass (live weight), it did not prevent successful reproduction and is suitable for short-term treatment of P. roqueforti infections.     

Sleeping site ecology in a rain-forest dwelling nocturnal lemur (Lepilemur mustelinus): implications for sociality and conservation

Suitable sleeping sites as potentially restricted resources are suggested to shape sociality in primates. We investigated sleeping site ecology of a rain-forest dwelling sportive lemur in eastern Madagascar for the first time. Using radiotelemetry, we characterized the type, quality and usage of sleeping sites as well as social sleeping habits of 11 focal individuals of the weasel sportive lemur (Lepilemur mustelinus) during the dry and the onset of the rainy season. Morphometric measurements provided additional information. The sexes showed an unusual sexual dimorphism for primates. Males and females did not differ in body length, but females surpassed males in body mass suggesting female dominance. Both sexes used dense vegetation and holes in hollow trees high above the ground as shelters for sleeping during the day. No sex difference in the quality of tree holes was found, but focal individuals used tree holes more often than open sleeping sites in dense vegetation. Both sexes showed high sleeping site fidelity limited to two to six different sites that they used primarily solitarily. The results imply that suitable sleeping sites are limited and survival of this species will strongly depend on the availability of mature rain forests with suitable hollow trees. Furthermore, these findings provide evidence of a solitary sleeping and ranging system in this rain-forest dwelling sportive lemur with suitable sleeping sites as defendable resources.     

The diet of two species of Isoperla (Plecoptera: Perlodidae) in relation to season,site, and sympatry

The seasonal change in gut contents of nymphs of Isoperla grammatica and I. difformis from six streams in southern Sweden was analysed. Both species had ingested a variety of benthic prey and vegetable matter, predominantly diatoms. Some seasonality was evident with high percentages of diatoms in spring in I. grammatica, and in autumn in I. difformis. The scope of food was larger in the latter species which contained about equal proportions of vegetable matter, chironomids, mayfly, stonefly, and black fly larvae. In I. grammatica plant matter and chironomids dominated strongly, comprising > 50% of the gut contents on an annual basis, > 90 % in spring. While small nymphs of I. difformis contained a low proportion of animal matter, only gradually increasing with size, the nymphs of I. grammatica were carnivorous from very early instars. Both species switched to a temporarily strong utilization of algae in spring. This differed among sites, and appeared to reflect differences in insolation and thus the availability of algae. There was a significant negative relationship between the mean densities of Isoperla nymphs and the proportion of animal material found in the guts of I. grammatica (R ² = 0.86). Considering the density of I. grammatica alone, the relationship was weaker (R ² = 0.56). A positive correlation between predator and prey size was observed. With chironomid prey the size range increased with predator size. With simuliid prey, however, prey size increased with predator size in such a way that it suggests selection rather than just an expanding prey size range. Correlations were stronger and regression coefficients significantly higher for I. grammatica than for I. difformis. We suggest that I. grammatica, which ingests a much wider size range of prey might choose prey of optimal sizes more readily than the more synchronously developing I. difformis. Although the life cycles of the two species are staggered, overlap in size distribution indicates that competition for food could be important in spring. However, observed differences in diet should facilitate coexistence. Gut content differences might in turn be accomplished through microhabitat segregation.     

Prey preferences of the spotted hyaena (Crocuta crocuta) and degree of dietary overlap with the lion (Panthera leo)

Spotted hyaenas Crocuta crocuta were once considered mere scavengers; however, detailed research revealed that they are very efficient predators. Information on what spotted hyaenas actually prefer to prey on and what they avoid is lacking, as well as the factors that influence prey selection. Data from 14 published and one unpublished study from six countries throughout the distribution of the spotted hyaena were used to determine which prey species were preferred and which were avoided using Jacobs' index. The mean of these values for each species was used as the dependent variable in multiple regression, with prey abundance and prey body mass as predictive variables. In stark contrast to the rest of Africa's large predator guild, spotted hyaenas do not preferentially prey on any species. Also surprisingly, only buffalo, giraffe and plains zebra are significantly avoided. Spotted hyaena most prefer prey within a body mass range of 56–182 kg, with a mode of 102 kg. The dietary niche breadth of the spotted hyaena is similar to that of the lion Panthera leo , and the two species have a 58.6% actual prey species overlap and a 68.8% preferred prey species overlap. These results highlight the flexible and unselective nature of spotted hyaena predation and are probably a reason for the species' success throughout its range, despite a large degree of dietary overlap with lions.     

Contrasting diel activity and feeding patterns of four instars of Rhyacophila dorsalis (Trichoptera)

1. Ontogenetic shifts in prey choice and predator behaviour can affect food‐web structure. Therefore, it is important to establish if the diet and feeding activity differ between life‐stages of the same species. This hypothesis was tested for second, third, fourth and fifth larval instars of Rhyacophila dorsalis by comparing their diel activity and feeding patterns. Second to fifth instars collected from two streams were used either for gut analyses or for observations of their activity and feeding patterns in three stream tanks. Food was provided in excess; being organisms living in bryophytes on top of a large stone in each tank, augmented by different‐sized larvae of Ephemeroptera, Simuliidae and Chironomidae. As few first instars for gut analyses were found in the field, the diet of first instars reared in the laboratory was also studied. 2. Larvae for gut analyses were taken 1 h before dusk or dawn (n = 50 larvae per instar for each day or night sample). First and second instars fed on the smaller food items with no significant day‐night differences in diet. Gut contents indicated a progressive trend from feeding chiefly at night in third instars to almost exclusively at night in fifth instars. Fourth and fifth instars fed on the larger food items, whilst the diet of the third instar larvae overlapped with that of both the earlier and later instars. 3. Diel activity patterns of single larvae differed between instars but not within each instar (n = 20 larvae per instar). Second instars were active throughout the 24 h, with peaks at dusk, around midnight, dawn and around midday. A similar pattern was shown by third instars but the peak of activity at midday was less than the other three peaks. Prey were captured only during these peaks for both instars. Fourth and fifth instars were most active, and fed only, at night. They used an ambush strategy to capture more active prey at dusk and dawn (e.g. Baetis, Gammarus), and a searching strategy to capture more sedentary prey during the night (e.g. chironomids, simuliids). These experiments provided support for the hypothesis under test. If competition and/or interference occur between instars, then it could be reduced between earlier and later instars because of differences in their diet and diel pattern of feeding activity.     

The molecular simulation of the miscibility,mechanical properties and physical cross-linking behavior of the poly(vinyl alcohol)/poly(acrylic acid) composited membranes

The miscibility and mechanical properties of poly vinyl alcohol (PVA) and poly acrylic acid (PAA)-composited membranes were studied with molecular simulation. The Flory–Huggins parameters (δ) were calculated to prove the good miscibility of PVA and PAA. The radial distribution functions of hydroxyl and carboxyl atoms and the average number of H-bonds were observed to indicate the degree of physical cross-linking between PVA and PAA. The influences of intermolecular physical cross-linking on the glass transition temperature and mechanical properties were estimated. The results revealed that the PVA/PAA membrane with a composition of 2:3 has the best plastic properties, which exhibits a good application value. All of the simulated results showed good agreement with the experimental data. It indicates that the method presented in this work has a promising application prospect.     

Inter-decadal patterns of population and dietary change in sea otters at Amchitka Island, Alaska

After having been hunted to near-extinction in the Pacific maritime fur trade, the sea otter population at Amchitka Island, Alaska increased from very low numbers in the early 1900s to near equilibrium density by the 1940s. The population persisted at or near equilibrium through the 1980s, but declined sharply in the 1990s in apparent response to increased killer whale predation. Sea otter diet and foraging behavior were studied at Amchitka from August 1992 to March 1994 and the data compared with similar information obtained during several earlier periods. In contrast with dietary patterns in the 1960s and 1970s, when the sea otter population was at or near equilibrium density and kelp-forest fishes were the dietary mainstay, these fishes were rarely eaten in the 1990s. Benthic invertebrates, particularly sea urchins, dominated the otter’s diet from early summer to mid-winter, then decreased in importance during late winter and spring when numerous Pacific smooth lumpsuckers (a large and easily captured oceanic fish) were eaten. The occurrence of spawning lumpsuckers in coastal waters apparently is episodic on a scale of years to decades. The otters’ recent dietary shift away from kelp-forest fishes is probably a response to the increased availability of lumpsuckers and sea urchins (both high-preference prey). Additionally, increased urchin densities have reduced kelp beds, thus further reducing the availability of kelp-forest fishes. Our findings suggest that dietary patterns reflect changes in population status and show how an ecosystem normally under top-down control and limited by coastal zone processes can be significantly perturbed by exogenous events. Received: 23 March 1999 / Accepted: 19 January 2000     

Management of dietary essential metals (iron,copper, zinc,chromium and manganese) by Wistar and Zucker obese rats fed a self-selected high-energy diet

The balances and content of essential elements (iron, copper, zinc, chromium and manganese) in the body of Wistar, Zucker lean and Zucker obese rats fed a reference or cafeteria diet from day 30 to 60 after birth have been studied. Intestinal iron absorption compensated for low iron content of the cafeteria diet and the extra needs of growth and fat deposition. It can be assumed that the altered energy regulation processes that afflict the genetically obese rat are not directly related to altered iron metabolism. Obese Zucker rats had lower copper tissue concentrations than lean rats, but when fed a cafeteria diet the differences between Zucker rats strains disappear. This cannot be traced to large differences in diet copper concentration. A low diet availability of zinc—such as that of cafeteria-fed fa/fa rats—is easily compensated for by increasing absorption. So, as a consequence, we can conclude that genetic obesity did not impair zinc absorption. There was no deficit of zinc in any of the groups studied; the rats have enough capacity to extract zinc within a wide range of dietary concentrations. The absorption of dietary chromium was inversely proportional to its concentration. The ability to extract chromium from the diet and the very low urinary losses are a consequence of its scarcity in most dietary items. Despite wide variations in the manganese of the diets, the absorption rates were practically unchanged except for obese rats fed the cafeteria diet. It seems that this low absorptive capacity is enough to supply the rat with the manganese it needs, since a sizeable—but subjected to 8-fold-span variations-proportion is lost in the urine. This alone points towards a considerable excess of manganese in both diets studied. Obesity does not have a significant effect on the abilities to absorb and retain minerals, since these processes were more related to dietary availability. Management of essential metals by obese rats depends whether this condition is genetic or induced by diet. Most of the differences observed can be related to differences in diet concentration, to the excess fat content or different metabolic attitude to use substrates of obese animals. The data presented show that the cafeteria diet used adequately serves the mineral needs of the rat, since the rat adapts its absorbing and retaining strategies to match the dietary availability of these minerals.     

Feeding habits and dietary overlap of Naididae (Oligochaeta) from a bog stream

Feeding habits and dietary overlap of three species of naidid oligochaetes (Chaetogaster diastrophus, Dero digitata, Dero nivea) were studied during June 1982–December 1983 from a bog stream in Wisconsin, USA. Chaetogaster diastrophus primarily ingested diatoms, while D. digitata and D. nivea primarily ingested detritus. Dietary overlap was substantial (97–98%) between D. digitata and D. nivea using the dietary overlap coefficient. Dietary overlap between C. diastrophus and D. digitata was 58–62% and that between C. diastrophus and D. nivea was 51–55%. Dietary differences existed between the three species in the percentage of each major food type and diatom genera ingested, selective ingestion or avoidance of diatom genera and in the size classes (length and/or volume) of diatoms consumed. These data suggest temporal coexistence of these species may possibly be due to complex food resource partitioning, although in this habitat, C. diastrophus, D. digitata, and D. nivea did not exhibit concurrent peak abundances; thus, interspecific competition for food was minimized.