Dispersal Ecology: Where Have All the Seeds Gone?

How effective are different animals at dispersing seeds? A new study has traced seeds sampled in faeces to their mother of origin and concluded that carnivorous mammals can be better dispersers than birds.     

Revisiting the cost of carnivory in mammals

Predator–prey relationships play a key role in the evolution and ecology of carnivores. An understanding of predator–prey relationships and how this differs across species and environments provides information on how carnivorous strategies have evolved and how they may change in response to environmental change. We aim to determine how mammals overcame the challenges of living within the marine environment; specifically, how this altered predator–prey body mass relationships relative to terrestrial mammals. Using predator and prey mass data collected from the literature, we applied phylogenetic piecewise regressions to investigate the relationship between predator and prey size across carnivorous mammals (51 terrestrial and 56 marine mammals). We demonstrate that carnivorous mammals have four broad dietary groups: small marine carnivores (< 11 000 kg) and small terrestrial carnivores (< 11 kg) feed on prey less than 5 kg and 2 kg, respectively. On average, large marine carnivores (> 11 000 kg) feed on prey equal to 0.01% of the carnivore's body size, compared to 45% or greater in large terrestrial carnivores (> 11 kg). We propose that differences in prey availability, and the relative ease of processing large prey in the terrestrial environment and small prey in marine environment, have led to the evolution of these novel foraging behaviours. Our results provide important insights into the selection pressures that may have been faced by early marine mammals and ultimately led to the evolution of a range of feeding strategies and predatory behaviours.     

Rabies prognosis in western Siberia and the regulatory factors of the epizootic process

In this article the regulatory factors of the epizootic process are considered and the spatial-temporal prognostication of rabies infection in the region is proposed on the basis of data on rabies morbidity among animals, the purchase of skins of carnivorous animals for 20-25 years, virological experiments on wild animals, calculation of the number of carnivores and small mammals, as meteorological observations. The study has shown that a variety of animal species serving as hosts for the virus and its population differences contribute to the stable existence of the infection. Rabies morbidity has been found to be positively linked with its preceding level, the number of wild animals, the height and hardness of the snow cover and negatively with the number of small mammals.     

Contrasting patterns of seed dispersal between alien mammals and native lizards in a declining plant species

The introduction of carnivorous mammals has led many native island species to extinction. In the Balearic Islands, the introduction of carnivorous mammals in the main islands has contributed to the extinction of the endemic lizard Podarcis lilfordi, which is an important seed disperser of many plant species. One of the introduced mammals, Martes martes (pine marten), is also known to disperse seeds and may replace the native lizard in this role in islands. However, little is known on the patterns of seed dispersal by these two different species and their possible implications for plant regeneration ability and population structure. We have compared the quality of seed deposition provided by both to the vulnerable Mediterranean shrub Cneorum tricoccon, by studying the pattern of seed distribution among sites generated by both dispersers as well as the suitability of those sites for seedling emergence and establishment. The study was carried out in two types of habitats (coastal shrublands and pine forests) and two islands (Mallorca and Dragonera). Lizards and mammals showed contrasting patterns of seed deposition and, where lizards were absent, mammals played their role as seed dispersers in pine forests but not in coastal shrublands. The lack of seed dispersal in the coastal shrubland seriously limits recruitment, by concentrating seeds under conspecifics and hindering colonisation opportunities, marking a long-term trend towards decline. The introduced predator replaces the native seed disperser in its service where it has gone extinct, although with important differences in the dispersal service provided.     

The Coccidia of the Zorille letonyx (Zorilia) capensis Kaup

The literature on the coccidia of the carnivorous mammals of the family Mustelidae has been reviewed. Three species of Isospora are described for the first time from the zoriile, Ictcnyx (Zorilla) capensis (Fam. Mustelidae ). Two of these, I. hoogstraali sp. now, and 7. africana sp. nov are considered to be new species, while the third one, I. bigemina var. zorillae var. nov. is recognized as a new variety.     

A killer appetite: metabolic consequences of carnivory in marine mammals

Among terrestrial mammals, the morphology of the gastrointestinal tract reflects the metabolic demands of the animal and individual requirements for processing, distributing, and absorbing nutrients. To determine if gastrointestinal tract morphology is similarly correlated with metabolic requirements in marine mammals, we examined the relationship between basal metabolic rate (BMR) and small intestinal length in pinnipeds and cetaceans. Oxygen consumption was measured for resting bottlenose dolphins and Weddell seals, and the results combined with data for four additional species of carnivorous marine mammal. Data for small intestinal length were obtained from previously published reports. Similar analyses were conducted for five species of carnivorous terrestrial mammal, for which BMR and intestinal length were known. The results indicate that the BMRs of Weddell seals and dolphins resting on the water surface are 1.6 and 2.3 times the predicted levels for similarly sized domestic terrestrial mammals, respectively. Small intestinal lengths for carnivorous marine mammals depend on body size and are comparatively longer than those of terrestrial carnivores. The relationship between basal metabolic rate (kcal day(-1)) and small intestinal length (m) for both marine and terrestrial carnivores was, BMR=142.5 intestinal length(1.20) (r(2)=0.83). We suggest that elevated metabolic rates among marine mammal carnivores are associated with comparatively large alimentary tracts that are presumably required for supporting the energetic demands of an aquatic lifestyle and for feeding on vertebrate and invertebrate prey.     

Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence

Here we describe an unusual fossil assemblage found inside a crotovine from the late Pliocene Chapadmalal ‘Formation’ (Buenos Aires Province). This assemblage contains the greatest vertebrate diversity recovered inside an ichnofossil of this type, including skeletal remains of dasypodids, didelphids, procyonids, anurans and caviomorph rodents within coprolites and disaggregated scatological waste. We describe four general size types for crotovines and palaeoburrows found in the Pliocene to Holocene of Argentina and Brazil, of which the structure found corresponds to the ‘mid-large’ size type and is linked to the activity of the large dasypodid Ringueletia simpsoni. The scatological remains are assigned to a small-sized carnivorous mammal with a body mass of between 1 and 6 kg. Within the guild of Chapadmalalan omnivorous–carnivorous mammals, this inferred mass range is restricted to large didelphids and mid-sized procyonids (represented in the assemblage by Thylophorops chapadmalensis and Cyonasua lutaria, respectively). The data gathered here confirms that the reoccupation of burrows is a common behaviour in small-sized carnivorous mammals at least since the early Pliocene. In addition, we suggest a predator–prey relationship between the studied carnivores and the most abundant small fossorial mammals of the Pampean Pliocene.     

Examining the Prey Mass of Terrestrial and Aquatic Carnivorous Mammals: Minimum,Maximum and Range

Predator-prey body mass relationships are a vital part of food webs across ecosystems and provide key information for predicting the susceptibility of carnivore populations to extinction. Despite this, there has been limited research on the minimum and maximum prey size of mammalian carnivores. Without information on large-scale patterns of prey mass, we limit our understanding of predation pressure, trophic cascades and susceptibility of carnivores to decreasing prey populations. The majority of studies that examine predator-prey body mass relationships focus on either a single or a subset of mammalian species, which limits the strength of our models as well as their broader application. We examine the relationship between predator body mass and the minimum, maximum and range of their prey''s body mass across 108 mammalian carnivores, from weasels to baleen whales (Carnivora and Cetacea). We test whether mammals show a positive relationship between prey and predator body mass, as in reptiles and birds, as well as examine how environment (aquatic and terrestrial) and phylogenetic relatedness play a role in this relationship. We found that phylogenetic relatedness is a strong driver of predator-prey mass patterns in carnivorous mammals and accounts for a higher proportion of variance compared with the biological drivers of body mass and environment. We show a positive predator-prey body mass pattern for terrestrial mammals as found in reptiles and birds, but no relationship for aquatic mammals. Our results will benefit our understanding of trophic interactions, the susceptibility of carnivores to population declines and the role of carnivores within ecosystems.     

Trichinella pseudospiralis in sedentary night-birds of prey from Central Italy.

Trichinella pseudospiralis has been isolated from carnivorous and carrion-feeding mammals and birds in Eastern Europe, Asia, Australia, and North America, suggesting its cosmopolitan distribution. We conducted a survey to detect this parasite in raptorial and carrion-feeding birds in Italy, examining muscles from 205 animals by artificial digestion. We isolated from the breast muscle 1 larva from a tawny owl (Strix aluco) and 2 larvae from a little owl (Athene noctua). These larvae were identified as T. pseudospiralis by the polymerase chain reaction with a specific primer set. This is the first documented report of T. pseudospiralis in animals in Western Europe.     

Direct Comparisons of 2D and 3D Dental Microwear Proxies in Extant Herbivorous and Carnivorous Mammals

The analysis of dental microwear is commonly used by paleontologists and anthropologists to clarify the diets of extinct species, including herbivorous and carnivorous mammals. Currently, there are numerous methods employed to quantify dental microwear, varying in the types of microscopes used, magnifications, and the characterization of wear in both two dimensions and three dimensions. Results from dental microwear studies utilizing different methods are not directly comparable and human quantification of wear features (e.g., pits and scratches) introduces interobserver error, with higher error being produced by less experienced individuals. Dental microwear texture analysis (DMTA), which analyzes microwear features in three dimensions, alleviates some of the problems surrounding two-dimensional microwear methods by reducing observer bias. Here, we assess the accuracy and comparability within and between 2D and 3D dental microwear analyses in herbivorous and carnivorous mammals at the same magnification. Specifically, we compare observer-generated 2D microwear data from photosimulations of the identical scanned areas of DMTA in extant African bovids and carnivorans using a scanning white light confocal microscope at 100x magnification. Using this magnification, dental microwear features quantified in 2D were able to separate grazing and frugivorous bovids using scratch frequency; however, DMTA variables were better able to discriminate between disparate dietary niches in both carnivorous and herbivorous mammals. Further, results demonstrate significant interobserver differences in 2D microwear data, with the microwear index remaining the least variable between experienced observers, consistent with prior research. Overall, our results highlight the importance of reducing observer error and analyzing dental microwear in three dimensions in order to consistently interpret diets accurately.     

Multiple adaptive losses of alanine-glyoxylate aminotransferase mitochondrial targeting in fruit-eating bats

The enzyme alanine-glyoxylate aminotransferase 1 (AGT) functions to detoxify glyoxylate before it is converted into harmful oxalate. In mammals, mitochondrial targeting of AGT in carnivorous species versus peroxisomal targeting in herbivores is controlled by two signal peptides that correspond to these respective organelles. Differential expression of the mitochondrial targeting sequence (MTS) is considered an adaptation to diet-specific subcellular localization of glyoxylate precursors. Bats are an excellent group in which to study adaptive changes in dietary enzymes; they show unparalleled mammalian dietary diversification as well as independent origins of carnivory, frugivory, and nectarivory. We studied the AGT gene in bats and other mammals with diverse diets and found that the MTS has been lost in unrelated lineages of frugivorous bats. Conversely, species exhibiting piscivory, carnivory, insectivory, and sanguinivory possessed intact MTSs. Detected positive selection in the AGT of ancestral fruit bats further supports adaptations related to evolutionary changes in diet.     

Fatal attraction: carnivorous plants roll out the red carpet to lure insects

We provide the first experimental test of the hypothesis that the coloration of carnivorous plants can act as a signal to lure insects and thus enhance capture rates. An experimental approach was needed to separate effects of the visual appearance of plants from those of traits that may correlate with appearance and also affect capture rates. We compared insect capture rates of pitcher plants with artificially coloured red and green pitchers in a paired design, and found that plants with red pitchers captured significantly more flying insects. Thus, we present the first experimental evidence of visual signalling in carnivorous plants. Further, it has previously been suggested that carnivorous plants use contrasting stripes or UV marks on their pitchers to lure insects; our results emphasize that insect traps do not need to sport contrasting colours to be attractive; it might be sufficient to be different from the background.     

Comparative lectin histochemical analysis of the duodenal glands in various mammals

Composition and histotopography of lectin receptors have been studied in 12 species of mammals with various nutritional specialization: carnivorous, phytophagous and omnivorous. In cells of the duodenal glands of the carnivorous and omnivorous receptors to concanavalin A and lentil lectin (D-mannosoglycans ) are absent and they are present in the glands of the phytophagous animals. In cells of some parts of the glands presence of receptors to soya bean lectin (N-acetyl-D-galactosamine++) is the most characteristic sign of the duodenal glands in the carnivorous and phytophagous animals. Together with certain differences, depending on the nutritional way of the animals, specific peculiarities of lectins binding with glandulocytes of the duodenal glands are demonstrated. The data on rearrangement of the lectin receptors are obtained during the process of cellular differentiation. Presence of N-acetyl-D-galactosamine++ remnants-biding soya bean lectin in composition of oligosaccharide++ chains of glycoconjugates is a sign of low differential degree of the glandular cells. In more differentiated cells concealment in oligosaccharide chains of D-galactose remnants (peanut and castor-oil lectins receptors) by L-fucose, N-acetil-D-glucosamin remnants and sialic acid can have place; this is demonstrated as accumulation of receptors to wheat germ and Laburnum anagyroides lectins in the glandular cells.     

Short-term fasting induces intra-hepatic lipid accumulation and decreases intestinal mass without reduced brush-border enzyme activity in mink (<Emphasis Type="Italic">Mustela vison</Emphasis>) small intestine

For many mammalian species short-term fasting is associated with intestinal atrophy and decreased digestive capacity. Under natural conditions, strictly carnivorous animals often experience prey scarcity during winter, and they may therefore be particularly well adapted to short-term food deprivation. To examine how the carnivorous gastrointestinal tract is affected by fasting, small-intestinal structure, brush-border enzyme activities and hepatic structure and function were examined in fed mink (controls) and mink that had been fasted for 1–10 days. During the first 1–2 days of fasting, intestinal mass decreased more rapidly than total body mass and villus heights were reduced 25–40%. In contrast, tissue-specific activity of the brush-border enzymes sucrase, maltase, lactase, aminopeptidase A and dipeptidylpeptidase IV increased 0.5- to1.5-fold at this time, but returned to prefasting levels after 6 days of fasting. After 6–10 days of fasting there was a marked increase in the activity of hepatic enzymes and accumulation of intra-hepatic lipid vacuoles. Thus, mink may be a useful model for studying fasting-induced intestinal atrophy and adaptation as well as mechanisms involved in accumulation of intra-hepatic lipids following food deprivation in strictly carnivorous domestic mammals, such as cats and ferrets.Communicated by I.D. Hume     

Forelimb anatomy and the discrimination of the predatory behavior of carnivorous mammals: The thylacine as a case study

Carnivorous mammals use their forelimbs in different ways to capture their prey. Most terrestrial carnivores have some cursorial (running) adaptations, but ambush predators retain considerable flexibility in their forelimb movement, important for grappling with their prey. In contrast, predators that rely on pursuit to run down their prey have sacrificed some of this flexibility for locomotor efficiency, in the greater restriction of the forelimb motion to the parasagittal plane. In this article, we measured aspects of the forelimb anatomy (44 linear measurements) in 36 species of carnivorous mammals of known predatory behavior, and used multivariate analyses to investigate how well the forelimb anatomy reflects the predatory mode (ambush, pursuit, or pounce‐pursuit). A prime intention of this study was to establish morphological correlates of behavior that could then be applied to fossil mammals: for this purpose, five individuals of the recently extinct thylacine (Thylacinus cynocephalus) were also included as unknowns. We show that the three different types of predators can be distinguished by their morphology, both in analyses where all the forelimb bones are included together, and in the separate analyses of each bone individually. Of particular interest is the ability to distinguish between the two types of more cursorial predators, pursuit and pounce‐pursuit, which have previously been considered as primarily size‐based categories. Despite a prior consideration of the thylacine as a “pounce‐pursuit” or an “ambush” type of predator, the thylacines did not consistently cluster with any type of predatory carnivores in our analyses. Rather, the thylacines appeared to be more generalized in their morphology than any of the extant carnivores. The absence of a large diversity of large carnivorous mammals in Australia, past and present, may explain the thylacine's generalized morphology. J. Morphol. 275:1321–1338, 2014. © 2014 Wiley Periodicals, Inc.     

Diet and locomotion of the armadillo Peltephilus: a new view

The Santacrucian armadillos Peltephilus (Mammalia, Dasypodidae, Peltephilinae) are reanalysed in order to test the traditional hypothesis that they were the most cursorial and active hunters of the dasypodids. The masticatory musculature is reconstructed, the form and distribution of teeth are studied, and a model of the jaw movements is proposed. Furthermore, the limb anatomy as well as their index of fossorial ability are compared with those of other armadillos. It is concluded that Peltephilus , and very likely other peltephilines, are poorly designed as carnivorous, actively cursorial mammals. An alternative habit is proposed, in which Peltephilus and the other peltephilines are viewed as having the conservative armadillo structure of diggers, feeding on soft but tough items, probably plant material of underground origin.     

The ecology and macroecology of mammalian home range area

Although many studies employ allometric relationships to demonstrate possible dependence of various traits on body mass, the relationship between home range size and body mass has been perhaps the most difficult to understand. Early studies demonstrated that carnivorous species had larger home ranges than herbivorous species of similar mass. These studies also argued that scaling relations (e.g., slopes) of the former were steeper than those of the latter and explained this in terms of the distribution of food resources, which are more uniformly distributed for most herbivores than for carnivores. In contrast to these studies, we show that scaling relations of home ranges for carnivorous mammals do not differ significantly from those of herbivorous and omnivorous species and that all three exhibit slopes that are significantly steeper than predicted on the basis of energetic requirements. We also demonstrate that home range size is constrained to fit within a polygonal constraint space bounded by lines representing energetic and/or biophysical limitations, which suggests that the log-linear relationship between home range area and mass may not be the appropriate function to compare against the energetically predicted slopes of 0.75 or 1.0. It remains unclear, however, why the slope of the relationship between home range area and body mass, whether based on raw data or on constraint lines, always exceeds that predicted by the energetic needs hypothesis.     

Pollinator‐prey conflict in carnivorous plants

Most carnivorous plants utilize insects in two ways: the flowers attract insects as pollen vectors for sexual reproduction, and the leaves trap insects for nutrients. Feeding on insects has been explained as an adaptation to nutrient‐poor soil, and carnivorous plants have been shown to benefit from insect capture through increased growth, earlier flowering and increased seed production. Most carnivorous plant species seem to benefit from insect pollination, although many species autonomously self‐pollinate and some propagate vegetatively. However, assuming that outcross pollen is advantageous and is a more important determinant of reproductive success than the nutrients gained from prey, there should be a selective pressure on carnivorous plants not to feed on their potential pollen vectors. Therefore, it has been suggested that carnivorous plants are subject to a conflict, often called the pollinator‐prey conflict (PPC). The conflict results from a trade‐off of the benefits from feeding on potentially pollinating insects versus the need to use them as pollen vectors for sexual reproduction. In this review we analyze the conditions under which a PPC may occur, review the evidence for the existence of PPCs in carnivorous plants, and explore the mechanisms that may be in place to prevent or alleviate a PPC. With respect to the latter, we discuss how plant signals such as olfactory and visual cues may play a role in separating the functions of pollinator attraction and prey capture.     

Human adaptations to meat eating

It is argued that Homo sapiens is a habitual rather than a facultative meat eater. Quantitative similarity of human gut morphology to guts of carnivorous mammals, preferential absorption of haem rather than iron of plant origin, and the exclusive use of humans as the definitive host by Taenia saginata and the almost complete human specificity of T. solium are used to support the argument.     

Costs of carnivory: tooth fracture in Pleistocene and Recent carnivorans

Large, carnivorous mammals often break their teeth, probably as a result of tooth to bone contact that occurs when carcasses are consumed more fully, a behaviour likely to occur under conditions of food stress. Recent studies of Pleistocene predators revealed high numbers of teeth broken in life, suggesting that carcass utilization and, consequently, food competition was more intense in the past than at present. However, the putative association between diet and tooth fracture frequency was based on a small sample of large, highly carnivorous species. In the present study, a greater diversity of extant carnivorans is sampled, including insectivorous, omnivorous, and carnivorous forms, ranging in size from weasels to tigers. Species that habitually consume hard foods (bones, shells) had the highest fracture frequencies, followed by carnivores, and then insectivorous and/or omnivorous species. Predator and prey sizes were not associated with tooth fracture frequency, but more aggressive species did break their teeth more often. Comparison of the modern sample with five Pleistocene species confirms the previous finding of higher tooth breakage in the past, although some extant species have fracture frequencies that approach those of extinct species. Thus, the Pleistocene predator guild appears to have been characterized by relatively high levels of competition that are rarely observed today.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 68–81.